From 8d4f9d241cdbd71a882a852c6e9285de279c0f87 Mon Sep 17 00:00:00 2001 From: Hans Verkuil Date: Sun, 18 Jan 2009 13:00:12 +0100 Subject: v4l2spec: add version 0.24 of the spec From: Hans Verkuil Priority: normal Signed-off-by: Hans Verkuil --- v4l/scripts/strip-trailing-whitespaces.sh | 2 +- v4l2-spec/Makefile | 496 ++++++ v4l2-spec/README | 17 + v4l2-spec/TEMPLATES | 90 ++ v4l2-spec/biblio.sgml | 219 +++ v4l2-spec/common.sgml | 1169 +++++++++++++++ v4l2-spec/compat.sgml | 2335 +++++++++++++++++++++++++++++ v4l2-spec/controls.sgml | 1660 ++++++++++++++++++++ v4l2-spec/crop.gif | Bin 0 -> 5967 bytes v4l2-spec/crop.pdf | Bin 0 -> 5846 bytes v4l2-spec/custom.dsl | 52 + v4l2-spec/dev-capture.sgml | 115 ++ v4l2-spec/dev-codec.sgml | 26 + v4l2-spec/dev-effect.sgml | 25 + v4l2-spec/dev-osd.sgml | 164 ++ v4l2-spec/dev-output.sgml | 111 ++ v4l2-spec/dev-overlay.sgml | 373 +++++ v4l2-spec/dev-radio.sgml | 55 + v4l2-spec/dev-raw-vbi.sgml | 347 +++++ v4l2-spec/dev-rds.sgml | 44 + v4l2-spec/dev-sliced-vbi.sgml | 396 +++++ v4l2-spec/dev-teletext.sgml | 40 + v4l2-spec/driver.sgml | 208 +++ v4l2-spec/fdl-appendix.sgml | 671 +++++++++ v4l2-spec/fieldseq_bt.gif | Bin 0 -> 25430 bytes v4l2-spec/fieldseq_bt.pdf | Bin 0 -> 9185 bytes v4l2-spec/fieldseq_tb.gif | Bin 0 -> 25323 bytes v4l2-spec/fieldseq_tb.pdf | Bin 0 -> 9173 bytes v4l2-spec/func-close.sgml | 70 + v4l2-spec/func-ioctl.sgml | 146 ++ v4l2-spec/func-mmap.sgml | 185 +++ v4l2-spec/func-munmap.sgml | 83 + v4l2-spec/func-open.sgml | 121 ++ v4l2-spec/func-poll.sgml | 127 ++ v4l2-spec/func-read.sgml | 189 +++ v4l2-spec/func-select.sgml | 138 ++ v4l2-spec/func-write.sgml | 136 ++ v4l2-spec/io.sgml | 1073 +++++++++++++ v4l2-spec/pixfmt-grey.sgml | 70 + v4l2-spec/pixfmt-nv12.sgml | 151 ++ v4l2-spec/pixfmt-packed-rgb.sgml | 862 +++++++++++ v4l2-spec/pixfmt-packed-yuv.sgml | 244 +++ v4l2-spec/pixfmt-sbggr16.sgml | 91 ++ v4l2-spec/pixfmt-sbggr8.sgml | 75 + v4l2-spec/pixfmt-uyvy.sgml | 128 ++ v4l2-spec/pixfmt-y16.sgml | 89 ++ v4l2-spec/pixfmt-y41p.sgml | 157 ++ v4l2-spec/pixfmt-yuv410.sgml | 141 ++ v4l2-spec/pixfmt-yuv411p.sgml | 155 ++ v4l2-spec/pixfmt-yuv420.sgml | 157 ++ v4l2-spec/pixfmt-yuv422p.sgml | 161 ++ v4l2-spec/pixfmt-yuyv.sgml | 128 ++ v4l2-spec/pixfmt.sgml | 728 +++++++++ v4l2-spec/v4l2.sgml | 465 ++++++ v4l2-spec/vbi_525.gif | Bin 0 -> 4741 bytes v4l2-spec/vbi_525.pdf | Bin 0 -> 3395 bytes v4l2-spec/vbi_625.gif | Bin 0 -> 5095 bytes v4l2-spec/vbi_625.pdf | Bin 0 -> 3683 bytes v4l2-spec/vbi_hsync.gif | Bin 0 -> 2400 bytes v4l2-spec/vbi_hsync.pdf | Bin 0 -> 7405 bytes v4l2-spec/vidioc-dbg-g-register.sgml | 238 +++ v4l2-spec/vidioc-encoder-cmd.sgml | 204 +++ v4l2-spec/vidioc-enum-fmt.sgml | 157 ++ v4l2-spec/vidioc-enum-frameintervals.sgml | 270 ++++ v4l2-spec/vidioc-enum-framesizes.sgml | 282 ++++ v4l2-spec/vidioc-enumaudio.sgml | 86 ++ v4l2-spec/vidioc-enumaudioout.sgml | 89 ++ v4l2-spec/vidioc-enuminput.sgml | 270 ++++ v4l2-spec/vidioc-enumoutput.sgml | 172 +++ v4l2-spec/vidioc-enumstd.sgml | 391 +++++ v4l2-spec/vidioc-g-audio.sgml | 188 +++ v4l2-spec/vidioc-g-audioout.sgml | 154 ++ v4l2-spec/vidioc-g-chip-ident.sgml | 236 +++ v4l2-spec/vidioc-g-crop.sgml | 143 ++ v4l2-spec/vidioc-g-ctrl.sgml | 130 ++ v4l2-spec/vidioc-g-enc-index.sgml | 213 +++ v4l2-spec/vidioc-g-ext-ctrls.sgml | 254 ++++ v4l2-spec/vidioc-g-fbuf.sgml | 435 ++++++ v4l2-spec/vidioc-g-fmt.sgml | 201 +++ v4l2-spec/vidioc-g-frequency.sgml | 145 ++ v4l2-spec/vidioc-g-input.sgml | 100 ++ v4l2-spec/vidioc-g-jpegcomp.sgml | 180 +++ v4l2-spec/vidioc-g-modulator.sgml | 240 +++ v4l2-spec/vidioc-g-output.sgml | 100 ++ v4l2-spec/vidioc-g-parm.sgml | 332 ++++ v4l2-spec/vidioc-g-priority.sgml | 144 ++ v4l2-spec/vidioc-g-sliced-vbi-cap.sgml | 264 ++++ v4l2-spec/vidioc-g-std.sgml | 99 ++ v4l2-spec/vidioc-g-tuner.sgml | 524 +++++++ v4l2-spec/vidioc-log-status.sgml | 58 + v4l2-spec/vidioc-overlay.sgml | 83 + v4l2-spec/vidioc-qbuf.sgml | 168 +++ v4l2-spec/vidioc-querybuf.sgml | 103 ++ v4l2-spec/vidioc-querycap.sgml | 270 ++++ v4l2-spec/vidioc-queryctrl.sgml | 391 +++++ v4l2-spec/vidioc-querystd.sgml | 83 + v4l2-spec/vidioc-reqbufs.sgml | 160 ++ v4l2-spec/vidioc-streamon.sgml | 106 ++ 98 files changed, 22347 insertions(+), 1 deletion(-) create mode 100644 v4l2-spec/Makefile create mode 100644 v4l2-spec/README create mode 100644 v4l2-spec/TEMPLATES create mode 100644 v4l2-spec/biblio.sgml create mode 100644 v4l2-spec/common.sgml create mode 100644 v4l2-spec/compat.sgml create mode 100644 v4l2-spec/controls.sgml create mode 100644 v4l2-spec/crop.gif create mode 100644 v4l2-spec/crop.pdf create mode 100644 v4l2-spec/custom.dsl create mode 100644 v4l2-spec/dev-capture.sgml create mode 100644 v4l2-spec/dev-codec.sgml create mode 100644 v4l2-spec/dev-effect.sgml create mode 100644 v4l2-spec/dev-osd.sgml create mode 100644 v4l2-spec/dev-output.sgml create mode 100644 v4l2-spec/dev-overlay.sgml create mode 100644 v4l2-spec/dev-radio.sgml create mode 100644 v4l2-spec/dev-raw-vbi.sgml create mode 100644 v4l2-spec/dev-rds.sgml create mode 100644 v4l2-spec/dev-sliced-vbi.sgml create mode 100644 v4l2-spec/dev-teletext.sgml create mode 100644 v4l2-spec/driver.sgml create mode 100644 v4l2-spec/fdl-appendix.sgml create mode 100644 v4l2-spec/fieldseq_bt.gif create mode 100644 v4l2-spec/fieldseq_bt.pdf create mode 100644 v4l2-spec/fieldseq_tb.gif create mode 100644 v4l2-spec/fieldseq_tb.pdf create mode 100644 v4l2-spec/func-close.sgml create mode 100644 v4l2-spec/func-ioctl.sgml create mode 100644 v4l2-spec/func-mmap.sgml create mode 100644 v4l2-spec/func-munmap.sgml create mode 100644 v4l2-spec/func-open.sgml create mode 100644 v4l2-spec/func-poll.sgml create mode 100644 v4l2-spec/func-read.sgml create mode 100644 v4l2-spec/func-select.sgml create mode 100644 v4l2-spec/func-write.sgml create mode 100644 v4l2-spec/io.sgml create mode 100644 v4l2-spec/pixfmt-grey.sgml create mode 100644 v4l2-spec/pixfmt-nv12.sgml create mode 100644 v4l2-spec/pixfmt-packed-rgb.sgml create mode 100644 v4l2-spec/pixfmt-packed-yuv.sgml create mode 100644 v4l2-spec/pixfmt-sbggr16.sgml create mode 100644 v4l2-spec/pixfmt-sbggr8.sgml create mode 100644 v4l2-spec/pixfmt-uyvy.sgml create mode 100644 v4l2-spec/pixfmt-y16.sgml create mode 100644 v4l2-spec/pixfmt-y41p.sgml create mode 100644 v4l2-spec/pixfmt-yuv410.sgml create mode 100644 v4l2-spec/pixfmt-yuv411p.sgml create mode 100644 v4l2-spec/pixfmt-yuv420.sgml create mode 100644 v4l2-spec/pixfmt-yuv422p.sgml create mode 100644 v4l2-spec/pixfmt-yuyv.sgml create mode 100644 v4l2-spec/pixfmt.sgml create mode 100644 v4l2-spec/v4l2.sgml create mode 100644 v4l2-spec/vbi_525.gif create mode 100644 v4l2-spec/vbi_525.pdf create mode 100644 v4l2-spec/vbi_625.gif create mode 100644 v4l2-spec/vbi_625.pdf create mode 100644 v4l2-spec/vbi_hsync.gif create mode 100644 v4l2-spec/vbi_hsync.pdf create mode 100644 v4l2-spec/vidioc-dbg-g-register.sgml create mode 100644 v4l2-spec/vidioc-encoder-cmd.sgml create mode 100644 v4l2-spec/vidioc-enum-fmt.sgml create mode 100644 v4l2-spec/vidioc-enum-frameintervals.sgml create mode 100644 v4l2-spec/vidioc-enum-framesizes.sgml create mode 100644 v4l2-spec/vidioc-enumaudio.sgml create mode 100644 v4l2-spec/vidioc-enumaudioout.sgml create mode 100644 v4l2-spec/vidioc-enuminput.sgml create mode 100644 v4l2-spec/vidioc-enumoutput.sgml create mode 100644 v4l2-spec/vidioc-enumstd.sgml create mode 100644 v4l2-spec/vidioc-g-audio.sgml create mode 100644 v4l2-spec/vidioc-g-audioout.sgml create mode 100644 v4l2-spec/vidioc-g-chip-ident.sgml create mode 100644 v4l2-spec/vidioc-g-crop.sgml create mode 100644 v4l2-spec/vidioc-g-ctrl.sgml create mode 100644 v4l2-spec/vidioc-g-enc-index.sgml create mode 100644 v4l2-spec/vidioc-g-ext-ctrls.sgml create mode 100644 v4l2-spec/vidioc-g-fbuf.sgml create mode 100644 v4l2-spec/vidioc-g-fmt.sgml create mode 100644 v4l2-spec/vidioc-g-frequency.sgml create mode 100644 v4l2-spec/vidioc-g-input.sgml create mode 100644 v4l2-spec/vidioc-g-jpegcomp.sgml create mode 100644 v4l2-spec/vidioc-g-modulator.sgml create mode 100644 v4l2-spec/vidioc-g-output.sgml create mode 100644 v4l2-spec/vidioc-g-parm.sgml create mode 100644 v4l2-spec/vidioc-g-priority.sgml create mode 100644 v4l2-spec/vidioc-g-sliced-vbi-cap.sgml create mode 100644 v4l2-spec/vidioc-g-std.sgml create mode 100644 v4l2-spec/vidioc-g-tuner.sgml create mode 100644 v4l2-spec/vidioc-log-status.sgml create mode 100644 v4l2-spec/vidioc-overlay.sgml create mode 100644 v4l2-spec/vidioc-qbuf.sgml create mode 100644 v4l2-spec/vidioc-querybuf.sgml create mode 100644 v4l2-spec/vidioc-querycap.sgml create mode 100644 v4l2-spec/vidioc-queryctrl.sgml create mode 100644 v4l2-spec/vidioc-querystd.sgml create mode 100644 v4l2-spec/vidioc-reqbufs.sgml create mode 100644 v4l2-spec/vidioc-streamon.sgml diff --git a/v4l/scripts/strip-trailing-whitespaces.sh b/v4l/scripts/strip-trailing-whitespaces.sh index cb341ce76..def48a67d 100755 --- a/v4l/scripts/strip-trailing-whitespaces.sh +++ b/v4l/scripts/strip-trailing-whitespaces.sh @@ -21,7 +21,7 @@ fi for file in `eval $files`; do case "$file" in - *.patch) + *.gif | *.pdf | *.patch) continue ;; esac diff --git a/v4l2-spec/Makefile b/v4l2-spec/Makefile new file mode 100644 index 000000000..db3d71974 --- /dev/null +++ b/v4l2-spec/Makefile @@ -0,0 +1,496 @@ +# Also update in v4l2.sgml! +VERSION = 0.24 + +SGMLS = \ + biblio.sgml \ + capture.c.sgml \ + common.sgml \ + compat.sgml \ + controls.sgml \ + dev-capture.sgml \ + dev-codec.sgml \ + dev-effect.sgml \ + dev-osd.sgml \ + dev-output.sgml \ + dev-overlay.sgml \ + dev-radio.sgml \ + dev-raw-vbi.sgml \ + dev-rds.sgml \ + dev-sliced-vbi.sgml \ + dev-teletext.sgml \ + driver.sgml \ + entities.sgml \ + fdl-appendix.sgml \ + func-close.sgml \ + func-ioctl.sgml \ + func-mmap.sgml \ + func-munmap.sgml \ + func-open.sgml \ + func-poll.sgml \ + func-read.sgml \ + func-select.sgml \ + func-write.sgml \ + indices.sgml \ + io.sgml \ + pixfmt-grey.sgml \ + pixfmt-nv12.sgml \ + pixfmt-packed-rgb.sgml \ + pixfmt-packed-yuv.sgml \ + pixfmt-sbggr16.sgml \ + pixfmt-sbggr8.sgml \ + pixfmt-uyvy.sgml \ + pixfmt-y16.sgml \ + pixfmt-y41p.sgml \ + pixfmt-yuv410.sgml \ + pixfmt-yuv411p.sgml \ + pixfmt-yuv420.sgml \ + pixfmt-yuv422p.sgml \ + pixfmt-yuyv.sgml \ + pixfmt.sgml \ + v4l2.sgml \ + videodev2.h.sgml \ + vidioc-cropcap.sgml \ + vidioc-dbg-g-register.sgml \ + vidioc-encoder-cmd.sgml \ + vidioc-enum-fmt.sgml \ + vidioc-enum-frameintervals.sgml \ + vidioc-enum-framesizes.sgml \ + vidioc-enumaudio.sgml \ + vidioc-enumaudioout.sgml \ + vidioc-enuminput.sgml \ + vidioc-enumoutput.sgml \ + vidioc-enumstd.sgml \ + vidioc-g-audio.sgml \ + vidioc-g-audioout.sgml \ + vidioc-g-chip-ident.sgml \ + vidioc-g-crop.sgml \ + vidioc-g-ctrl.sgml \ + vidioc-g-enc-index.sgml \ + vidioc-g-ext-ctrls.sgml \ + vidioc-g-fbuf.sgml \ + vidioc-g-fmt.sgml \ + vidioc-g-frequency.sgml \ + vidioc-g-input.sgml \ + vidioc-g-jpegcomp.sgml \ + vidioc-g-modulator.sgml \ + vidioc-g-output.sgml \ + vidioc-g-parm.sgml \ + vidioc-g-priority.sgml \ + vidioc-g-sliced-vbi-cap.sgml \ + vidioc-g-std.sgml \ + vidioc-g-tuner.sgml \ + vidioc-log-status.sgml \ + vidioc-overlay.sgml \ + vidioc-qbuf.sgml \ + vidioc-querybuf.sgml \ + vidioc-querycap.sgml \ + vidioc-queryctrl.sgml \ + vidioc-querystd.sgml \ + vidioc-reqbufs.sgml \ + vidioc-streamon.sgml \ + +PDFPICS = \ + crop.pdf \ + fieldseq_bt.pdf \ + fieldseq_tb.pdf \ + vbi_525.pdf \ + vbi_625.pdf \ + vbi_hsync.pdf + +GIFPICS = \ + crop.gif \ + fieldseq_bt.gif \ + fieldseq_tb.gif \ + vbi_525.gif \ + vbi_625.gif \ + vbi_hsync.gif + +# Some Jade warnings for authors. +WARN = +#WARN = -w all -w duplicate -w net + +# Stylesheet customization. +CUSTOM_HTML = --dsl custom.dsl\#html +CUSTOM_PRINT = --dsl custom.dsl\#print + +all: capture html-single pdf html + +html: html-build.stamp + +html-single: html-single-build.stamp + +pdf: pdf-build.stamp + +FUNCS = \ + close \ + ioctl \ + mmap \ + munmap \ + open \ + poll \ + read \ + select \ + write \ + +IOCTLS = \ + VIDIOC_CROPCAP \ + VIDIOC_DBG_G_REGISTER \ + VIDIOC_DBG_S_REGISTER \ + VIDIOC_DQBUF \ + VIDIOC_ENCODER_CMD \ + VIDIOC_ENUMAUDIO \ + VIDIOC_ENUMAUDOUT \ + VIDIOC_ENUMINPUT \ + VIDIOC_ENUMOUTPUT \ + VIDIOC_ENUMSTD \ + VIDIOC_ENUM_FMT \ + VIDIOC_ENUM_FRAMEINTERVALS \ + VIDIOC_ENUM_FRAMESIZES \ + VIDIOC_G_AUDIO \ + VIDIOC_G_AUDOUT \ + VIDIOC_G_CHIP_IDENT \ + VIDIOC_G_CROP \ + VIDIOC_G_CTRL \ + VIDIOC_G_ENC_INDEX \ + VIDIOC_G_EXT_CTRLS \ + VIDIOC_G_FBUF \ + VIDIOC_G_FMT \ + VIDIOC_G_FREQUENCY \ + VIDIOC_G_INPUT \ + VIDIOC_G_JPEGCOMP \ + VIDIOC_G_MPEGCOMP \ + VIDIOC_G_MODULATOR \ + VIDIOC_G_OUTPUT \ + VIDIOC_G_PARM \ + VIDIOC_G_PRIORITY \ + VIDIOC_G_SLICED_VBI_CAP \ + VIDIOC_G_STD \ + VIDIOC_G_TUNER \ + VIDIOC_LOG_STATUS \ + VIDIOC_OVERLAY \ + VIDIOC_QBUF \ + VIDIOC_QUERYBUF \ + VIDIOC_QUERYCAP \ + VIDIOC_QUERYCTRL \ + VIDIOC_QUERYMENU \ + VIDIOC_QUERYSTD \ + VIDIOC_REQBUFS \ + VIDIOC_STREAMOFF \ + VIDIOC_STREAMON \ + VIDIOC_S_AUDIO \ + VIDIOC_S_AUDOUT \ + VIDIOC_S_CROP \ + VIDIOC_S_CTRL \ + VIDIOC_S_EXT_CTRLS \ + VIDIOC_S_FBUF \ + VIDIOC_S_FMT \ + VIDIOC_S_FREQUENCY \ + VIDIOC_S_INPUT \ + VIDIOC_S_JPEGCOMP \ + VIDIOC_S_MPEGCOMP \ + VIDIOC_S_MODULATOR \ + VIDIOC_S_OUTPUT \ + VIDIOC_S_PARM \ + VIDIOC_S_PRIORITY \ + VIDIOC_S_STD \ + VIDIOC_S_TUNER \ + VIDIOC_TRY_ENCODER_CMD \ + VIDIOC_TRY_EXT_CTRLS \ + VIDIOC_TRY_FMT \ + +TYPES = \ + v4l2_std_id \ + +ENUMS = \ + v4l2_buf_type \ + v4l2_colorspace \ + v4l2_ctrl_type \ + v4l2_field \ + v4l2_frmivaltypes \ + v4l2_frmsizetypes \ + v4l2_memory \ + v4l2_priority \ + v4l2_tuner_type \ + +STRUCTS = \ + v4l2_audio \ + v4l2_audioout \ + v4l2_buffer \ + v4l2_capability \ + v4l2_captureparm \ + v4l2_chip_ident \ + v4l2_clip \ + v4l2_control \ + v4l2_crop \ + v4l2_cropcap \ + v4l2_enc_idx \ + v4l2_enc_idx_entry \ + v4l2_encoder_cmd \ + v4l2_ext_control \ + v4l2_ext_controls \ + v4l2_fmtdesc \ + v4l2_format \ + v4l2_fract \ + v4l2_framebuffer \ + v4l2_frequency \ + v4l2_frmival_stepwise \ + v4l2_frmivalenum \ + v4l2_frmsize_discrete \ + v4l2_frmsize_stepwise \ + v4l2_frmsizeenum \ + v4l2_input \ + v4l2_jpegcompression \ + v4l2_modulator \ + v4l2_output \ + v4l2_outputparm \ + v4l2_pix_format \ + v4l2_queryctrl \ + v4l2_querymenu \ + v4l2_rect \ + v4l2_register \ + v4l2_requestbuffers \ + v4l2_sliced_vbi_cap \ + v4l2_sliced_vbi_data \ + v4l2_sliced_vbi_format \ + v4l2_standard \ + v4l2_streamparm \ + v4l2_timecode \ + v4l2_tuner \ + v4l2_vbi_format \ + v4l2_window \ + +ERRORS = \ + EACCES \ + EAGAIN \ + EBADF \ + EBUSY \ + EFAULT \ + EIO \ + EINTR \ + EINVAL \ + ENFILE \ + ENOMEM \ + ENOTTY \ + ENXIO \ + EMFILE \ + EPERM \ + ERANGE \ + +ESCAPE = \ + -e "s/&/\\&/g" \ + -e "s//\\>/g" + +# Generate references to these structs in videodev2.h.sgml. +DOCUMENTED = \ + -e "s/\(\(enum\|struct\) *\)\(v4l2_[a-zA-Z0-9_]*\)/\1\3<\/link>/g" \ + -e "s/\(V4L2_PIX_FMT_[A-Z0-9_]\+\) /\1<\/link> /g" \ + -e ":a;s/\(linkend=\".*\)_\(.*\">\)/\1-\2/;ta" + +# We don't generate references to these structs in videodev2.h.sgml +# because they are undocumented. +UNDOCUMENTED = \ + $(shell for i in \ + v4l2_bitrate \ + v4l2_bitrate_mode \ + v4l2_exposure_auto_type \ + v4l2_mpeg_aspectratio \ + v4l2_mpeg_aspectratio \ + v4l2_mpeg_audio_crc \ + v4l2_mpeg_audio_emphasis \ + v4l2_mpeg_audio_encoding \ + v4l2_mpeg_audio_l1_bitrate \ + v4l2_mpeg_audio_l2_bitrate \ + v4l2_mpeg_audio_l3_bitrate \ + v4l2_mpeg_audio_mode \ + v4l2_mpeg_audio_mode_extension \ + v4l2_mpeg_audio_sampling_freq \ + v4l2_mpeg_audiotype \ + v4l2_mpeg_audiotype \ + v4l2_mpeg_compression \ + v4l2_mpeg_compression \ + v4l2_mpeg_cx2341x_video_chroma_spatial_filter_type \ + v4l2_mpeg_cx2341x_video_luma_spatial_filter_type \ + v4l2_mpeg_cx2341x_video_median_filter_type \ + v4l2_mpeg_cx2341x_video_spatial_filter_mode \ + v4l2_mpeg_cx2341x_video_temporal_filter_mode \ + v4l2_mpeg_stream_type \ + v4l2_mpeg_stream_vbi_fmt \ + v4l2_mpeg_streamtype \ + v4l2_mpeg_streamtype \ + v4l2_mpeg_video_aspect \ + v4l2_mpeg_video_bitrate_mode \ + v4l2_mpeg_video_encoding \ + v4l2_mpeg_videotype \ + v4l2_mpeg_videotype \ + v4l2_power_line_frequency \ + v4l2_prio_state \ + ; do echo "-e \"s/ *$$i/\\\\ $$i/g\""; done) + +capture.c.sgml: ../v4l2-apps/test/capture_example.c Makefile + echo "" > $@ + expand --tabs=8 < $< | \ + sed $(ESCAPE) $(UNDOCUMENTED) $(DOCUMENTED) | \ + sed 's/i\.e\./&ie;/' >> $@ + echo "" >> $@ + +videodev2.h.sgml: ../linux/include/linux/videodev2.h Makefile + echo "" > $@ + expand --tabs=8 < $< | \ + sed $(ESCAPE) $(UNDOCUMENTED) $(DOCUMENTED) | \ + sed 's/i\.e\./&ie;/' >> $@ + echo "" >> $@ + +checks: + # Warn about FOO-BAR which should be + # &FOO-BAR; or FOO_BAR. + (! grep '>[A-Z]+-[A-Z-]+<' *.sgml) + # Don't end a refpurpose blob with a period. + (! grep '\.' *.sgml) + # Catch typos in error code names. + errs=`grep '[^<]\+' *.sgml | \ + sed 's/.*//;s/<\/errorcode>.*//' | sort -u` ; \ + for err in $$errs; do \ + if ! echo $(ERRORS) | grep -q $$err ; then \ + echo Unknown error code $$err ; exit 1 ; \ + fi ; \ + done + # Use the respective entities instead. + for abbrev in "e\\.g\\." "i\\.e\\." "i2c" ; do \ + grep "[^a-z&]$$abbrev[^a-z.;-]" *.sgml | \ + grep -v -E "(ENTITY|videodev2\.h)" && exit 1 ; \ + done ; \ + exit 0 + +# We're generating these entities to avoid typos, to enforce consistent +# naming, an to be warned about missing items (Jade screams bloody murder +# if references are dangling). +entities.sgml: Makefile + echo "" >$@ + echo -e "\n" >>$@ + for ident in $(FUNCS) ; do \ + entity=`echo $$ident | tr _ -` ; \ + echo "$$ident()\">" \ + >>$@ ; \ + done + echo -e "\n" >>$@ + for ident in $(IOCTLS) ; do \ + entity=`echo $$ident | tr _ -` ; \ + id=`grep "$$ident" vidioc-*.sgml | sed 's/\.sgml.*//'` ; \ + echo "$$ident\">" \ + >>$@ ; \ + done + echo -e "\n" >>$@ + for ident in $(TYPES) ; do \ + entity=`echo $$ident | tr _ -` ; \ + echo "$$ident\">" >>$@ ; \ + done + echo -e "\n" >>$@ + for ident in $(ENUMS) ; do \ + entity=`echo $$ident | tr _ -` ; \ + echo "$$ident\">" >>$@ ; \ + done + echo -e "\n" >>$@ + for ident in $(STRUCTS) ; do \ + entity=`echo $$ident | tr _ -` ; \ + echo "$$ident\">" >>$@ ; \ + done + echo -e "\n" >>$@ + for ident in $(ERRORS) ; do \ + echo "$$ident" \ + "error code\">" >>$@ ; \ + done + echo -e "\n" >>$@ + for file in $(SGMLS) ; do \ + entity=`echo "$$file" | sed 's/.sgml//;s/\./-/g'` ; \ + if ! echo "$$file" | \ + grep -q -E -e '^(func|vidioc|pixfmt)-' ; then \ + echo "" >>$@ ; \ + fi ; \ + done + echo -e "\n" >>$@ + for file in $(SGMLS) ; do \ + if echo "$$file" | \ + grep -q -E -e '^(func|vidioc|pixfmt)-' ; then \ + entity=`echo "$$file" | sed 's/^[^-]*/sub/;s/.sgml//'` ; \ + echo "" >>$@ ; \ + fi ; \ + done + +# Jade can auto-generate a list-of-tables, which includes all structs, +# but we only want data types, all types, and sorted please. +indices.sgml: Makefile + echo "" >$@ + echo -e "\nList of Types" >>$@ + for ident in $(TYPES) ; do \ + id=`echo $$ident | tr _ -` ; \ + echo "$$ident" >>$@ ; \ + done + for ident in $(ENUMS) ; do \ + id=`echo $$ident | tr _ -` ; \ + echo "enum $$ident" >>$@ ; \ + done + for ident in $(STRUCTS) ; do \ + id=`echo $$ident | tr _ -` ; \ + echo "struct $$ident" >>$@ ; \ + done + echo "" >>$@ + +# HTML version. +html-build.stamp: Makefile checks $(SGMLS) $(GIFPICS) + rm -rf v4l2 + if which docbook2html >/dev/null ; then \ + docbook2html $(WARN) $(CUSTOM_HTML) --output v4l2 v4l2.sgml ; \ + else \ + db2html $(WARN) $(CUSTOM_HTML) --output v4l2 v4l2.sgml ; \ + fi + cp $(GIFPICS) v4l2/ + cd v4l2 ; \ + test -e index.html || ln -s book1.htm index.html ; \ + test -e capture-example.html || \ + ln -s `grep -l getopt_long *.htm` capture-example.html + chmod a+rX -R v4l2 + touch html-build.stamp + +# For online version. When you have a dial-up connection a single file +# is more convenient than clicking through dozens of pages. +html-single-build.stamp: Makefile checks $(SGMLS) $(GIFPICS) + rm -rf v4l2-single + if which docbook2html >/dev/null; then \ + docbook2html $(WARN) $(CUSTOM_HTML) --nochunks \ + --output v4l2-single v4l2.sgml ; \ + else \ + db2html $(WARN) $(CUSTOM_HTML) --nochunks \ + --output v4l2-single v4l2.sgml ; \ + fi + cp $(GIFPICS) v4l2-single/ + chmod a+rX -R v4l2-single + touch html-single-build.stamp + +# For printing. +pdf-build.stamp: Makefile checks $(SGMLS) $(PDFPICS) + if which docbook2pdf >/dev/null; then \ + docbook2pdf $(WARN) $(CUSTOM_PRINT) v4l2.sgml ; \ + else \ + db2pdf $(WARN) $(CUSTOM_PRINT) v4l2.sgml ; \ + fi + touch pdf-build.stamp + +# Example. +capture: ../v4l2-apps/test/capture_example.c + gcc $^ -o $@ + +clean: + rm -f *.stamp + rm -f videodev2.h.sgml + rm -f capture.c.sgml + rm -f capture + rm -f indices.sgml entities.sgml diff --git a/v4l2-spec/README b/v4l2-spec/README new file mode 100644 index 000000000..1d651cf62 --- /dev/null +++ b/v4l2-spec/README @@ -0,0 +1,17 @@ +This is the DocBook source of the Video For Linux Two API Specification. + +The latest version is part of the v4l-dvb master repository: + + http://linuxtv.org/hg/v4l-dvb + +If you have ideas or questions regarding V4L2, please try the +linux-media mailing list. Information on how to join is here: + + http://www.linuxtv.org/lists.php + +The Makefile supports the following targets: + +html Tree of HTML files (default) +html-single A single HTML file +pdf A PDF file +coffeebreak All of the above diff --git a/v4l2-spec/TEMPLATES b/v4l2-spec/TEMPLATES new file mode 100644 index 000000000..31aa64289 --- /dev/null +++ b/v4l2-spec/TEMPLATES @@ -0,0 +1,90 @@ +These are templates for various tables. Happy copy-and-pasting! + +cs-str; are colspecs for a struct table +cs-ustr; are colspecs for a struct table with substructs (four columns) +cs-def; are colspecs for a defines or enums table + + + struct <structname>v4l2_</structname> + + &cs-str; + + + + + + + + +
+ + + struct <structname>v4l2_</structname> + + &cs-ustr; + + + type + name + + descr + + + + type + name + descr + + + +
+ + + enum v4l2_ + + &cs-def; + + + + 1 + + + + +
+ + + Flags + + &cs-def; + + + V4L2_ + 0x + + + + +
+ +
+ Banana Example + + + + + + A banana + + +
+ +For EMACS, put that at the end of each sgml file. + + diff --git a/v4l2-spec/biblio.sgml b/v4l2-spec/biblio.sgml new file mode 100644 index 000000000..b013ece1d --- /dev/null +++ b/v4l2-spec/biblio.sgml @@ -0,0 +1,219 @@ + + References + + + EIA 608-B + + Electronic Industries Alliance (http://www.eia.org) + + EIA 608-B "Recommended Practice for Line 21 Data +Service" + + + + EN 300 294 + + European Telecommunication Standards Institute +(http://www.etsi.org) + + EN 300 294 "625-line television Wide Screen Signalling +(WSS)" + + + + ETS 300 231 + + European Telecommunication Standards Institute +(http://www.etsi.org) + + ETS 300 231 "Specification of the domestic video +Programme Delivery Control system (PDC)" + + + + ETS 300 706 + + European Telecommunication Standards Institute +(http://www.etsi.org) + + ETS 300 706 "Enhanced Teletext specification" + + + + ISO 13818-1 + + International Telecommunication Union (http://www.itu.ch), International +Organisation for Standardisation (http://www.iso.ch) + + ITU-T Rec. H.222.0 | ISO/IEC 13818-1 "Information +technology — Generic coding of moving pictures and associated +audio information: Systems" + + + + ISO 13818-2 + + International Telecommunication Union (http://www.itu.ch), International +Organisation for Standardisation (http://www.iso.ch) + + ITU-T Rec. H.262 | ISO/IEC 13818-2 "Information +technology — Generic coding of moving pictures and associated +audio information: Video" + + + + ITU BT.470 + + International Telecommunication Union (http://www.itu.ch) + + ITU-R Recommendation BT.470-6 "Conventional Television +Systems" + + + + ITU BT.601 + + International Telecommunication Union (http://www.itu.ch) + + ITU-R Recommendation BT.601-5 "Studio Encoding Parameters +of Digital Television for Standard 4:3 and Wide-Screen 16:9 Aspect +Ratios" + + + + ITU BT.653 + + International Telecommunication Union (http://www.itu.ch) + + ITU-R Recommendation BT.653-3 "Teletext systems" + + + + ITU BT.709 + + International Telecommunication Union (http://www.itu.ch) + + ITU-R Recommendation BT.709-5 "Parameter values for the +HDTV standards for production and international programme +exchange" + + + + ITU BT.1119 + + International Telecommunication Union (http://www.itu.ch) + + ITU-R Recommendation BT.1119 "625-line +television Wide Screen Signalling (WSS)" + + + + JFIF + + Independent JPEG Group (http://www.ijg.org) + + JPEG File Interchange Format + Version 1.02 + + + + SMPTE 12M + + Society of Motion Picture and Television Engineers +(http://www.smpte.org) + + SMPTE 12M-1999 "Television, Audio and Film - Time and +Control Code" + + + + SMPTE 170M + + Society of Motion Picture and Television Engineers +(http://www.smpte.org) + + SMPTE 170M-1999 "Television - Composite Analog Video +Signal - NTSC for Studio Applications" + + + + SMPTE 240M + + Society of Motion Picture and Television Engineers +(http://www.smpte.org) + + SMPTE 240M-1999 "Television - Signal Parameters - +1125-Line High-Definition Production" + + + + V4L + + + Alan + Cox + + Red Hat, Inc. +
+ alan@redhat.com +
+ + + + Video4Linux API Specification + + This file is part of the Linux kernel sources under +Documentation/video4linux. + + + + + V4LPROG + + + Alan + Cox + + Red Hat, Inc. +
+ alan@redhat.com +
+ + + + Video4Linux Programming (a.k.a. The Video4Linux +Book) + + About V4L driver programming. This +book is part of the Linux kernel DocBook documentation, for example at + +http://kernelnewbies.org/documents/. SGML sources are included +in the kernel sources. + + + 2000 + Alan Cox + + + + + + diff --git a/v4l2-spec/common.sgml b/v4l2-spec/common.sgml new file mode 100644 index 000000000..e68f7e490 --- /dev/null +++ b/v4l2-spec/common.sgml @@ -0,0 +1,1169 @@ + Common API Elements + + Programming a V4L2 device consists of these +steps: + + + + Opening the device + + + Changing device properties, selecting a video and audio +input, video standard, picture brightness a. o. + + + Negotiating a data format + + + Negotiating an input/output method + + + The actual input/output loop + + + Closing the device + + + + In practice most steps are optional and can be executed out of +order. It depends on the V4L2 device type, you can read about the +details in . In this chapter we will discuss +the basic concepts applicable to all devices. + +
+ Opening and Closing Devices + +
+ Device Naming + + V4L2 drivers are implemented as kernel modules, loaded +manually by the system administrator or automatically when a device is +first opened. The driver modules plug into the "videodev" kernel +module. It provides helper functions and a common application +interface specified in this document. + + Each driver thus loaded registers one or more device nodes +with major number 81 and a minor number between 0 and 255. Assigning +minor numbers to V4L2 devices is entirely up to the system administrator, +this is primarily intended to solve conflicts between devices. + Access permissions are associated with character +device special files, hence we must ensure device numbers cannot +change with the module load order. To this end minor numbers are no +longer automatically assigned by the "videodev" module as in V4L but +requested by the driver. The defaults will suffice for most people +unless two drivers compete for the same minor numbers. + The module options to select minor numbers are named +after the device special file with a "_nr" suffix. For example "video_nr" +for /dev/video video capture devices. The number is +an offset to the base minor number associated with the device type. + + In earlier versions of the V4L2 API the module options +where named after the device special file with a "unit_" prefix, expressing +the minor number itself, not an offset. Rationale for this change is unknown. +Lastly the naming and semantics are just a convention among driver writers, +the point to note is that minor numbers are not supposed to be hardcoded +into drivers. + When the driver supports multiple devices of the same +type more than one minor number can be assigned, separated by commas: + + +> insmod mydriver.o video_nr=0,1 radio_nr=0,1 + + + In /etc/modules.conf this may be +written as: + +alias char-major-81-0 mydriver +alias char-major-81-1 mydriver +alias char-major-81-64 mydriver +options mydriver video_nr=0,1 radio_nr=0,1 + + + + When an application attempts to open a device +special file with major number 81 and minor number 0, 1, or 64, load +"mydriver" (and the "videodev" module it depends upon). + + + Register the first two video capture devices with +minor number 0 and 1 (base number is 0), the first two radio device +with minor number 64 and 65 (base 64). + + + When no minor number is given as module +option the driver supplies a default. +recommends the base minor numbers to be used for the various device +types. Obviously minor numbers must be unique. When the number is +already in use the offending device will not be +registered. + + By convention system administrators create various +character device special files with these major and minor numbers in +the /dev directory. The names recomended for the +different V4L2 device types are listed in . + + + The creation of character special files (with +mknod) is a privileged operation and +devices cannot be opened by major and minor number. That means +applications cannot reliable scan for loaded or +installed drivers. The user must enter a device name, or the +application can try the conventional device names. + + Under the device filesystem (devfs) the minor number +options are ignored. V4L2 drivers (or by proxy the "videodev" module) +automatically create the required device files in the +/dev/v4l directory using the conventional device +names above. +
+ + + +
+ Multiple Opens + + In general, V4L2 devices can be opened more than once. +When this is supported by the driver, users can for example start a +"panel" application to change controls like brightness or audio +volume, while another application captures video and audio. In other words, panel +applications are comparable to an OSS or ALSA audio mixer application. +When a device supports multiple functions like capturing and overlay +simultaneously, multiple opens allow concurrent +use of the device by forked processes or specialized applications. + + Multiple opens are optional, although drivers should +permit at least concurrent accesses without data exchange, &ie; panel +applications. This implies &func-open; can return an &EBUSY; when the +device is already in use, as well as &func-ioctl; functions initiating +data exchange (namely the &VIDIOC-S-FMT; ioctl), and the &func-read; +and &func-write; functions. + + Mere opening a V4L2 device does not grant exclusive +access. + Drivers could recognize the +O_EXCL open flag. Presently this is not required, +so applications cannot know if it really works. + Initiating data exchange however assigns the right +to read or write the requested type of data, and to change related +properties, to this file descriptor. Applications can request +additional access privileges using the priority mechanism described in +. +
+ +
+ Shared Data Streams + + V4L2 drivers should not support multiple applications +reading or writing the same data stream on a device by copying +buffers, time multiplexing or similar means. This is better handled by +a proxy application in user space. When the driver supports stream +sharing anyway it must be implemented transparently. The V4L2 API does +not specify how conflicts are solved. +
+ +
+ Functions + + To open and close V4L2 devices applications use the +&func-open; and &func-close; function, respectively. Devices are +programmed using the &func-ioctl; function as explained in the +following sections. +
+
+ +
+ Querying Capabilities + + Because V4L2 covers a wide variety of devices not all +aspects of the API are equally applicable to all types of devices. +Furthermore devices of the same type have different capabilities and +this specification permits the omission of a few complicated and less +important parts of the API. + + The &VIDIOC-QUERYCAP; ioctl is available to check if the kernel +device is compatible with this specification, and to query the functions and I/O +methods supported by the device. Other features can be queried +by calling the respective ioctl, for example &VIDIOC-ENUMINPUT; +to learn about the number, types and names of video connectors on the +device. Although abstraction is a major objective of this API, the +ioctl also allows driver specific applications to reliable identify +the driver. + + All V4L2 drivers must support +VIDIOC_QUERYCAP. Applications should always call +this ioctl after opening the device. +
+ +
+ Application Priority + + When multiple applications share a device it may be +desirable to assign them different priorities. Contrary to the +traditional "rm -rf /" school of thought a video recording application +could for example block other applications from changing video +controls or switching the current TV channel. Another objective is to +permit low priority applications working in background, which can be +preempted by user controlled applications and automatically regain +control of the device at a later time. + + Since these features cannot be implemented entirely in user +space V4L2 defines the &VIDIOC-G-PRIORITY; and &VIDIOC-S-PRIORITY; +ioctls to request and query the access priority associate with a file +descriptor. Opening a device assigns a medium priority, compatible +with earlier versions of V4L2 and drivers not supporting these ioctls. +Applications requiring a different priority will usually call +VIDIOC_S_PRIORITY after verifying the device with +the &VIDIOC-QUERYCAP; ioctl. + + Ioctls changing driver properties, such as &VIDIOC-S-INPUT;, +return an &EBUSY; after another application obtained higher priority. +An event mechanism to notify applications about asynchronous property +changes has been proposed but not added yet. +
+ +
+ Video Inputs and Outputs + + Video inputs and outputs are physical connectors of a +device. These can be for example RF connectors (antenna/cable), CVBS +a.k.a. Composite Video, S-Video or RGB connectors. Only video and VBI +capture devices have inputs, output devices have outputs, at least one +each. Radio devices have no video inputs or outputs. + + To learn about the number and attributes of the +available inputs and outputs applications can enumerate them with the +&VIDIOC-ENUMINPUT; and &VIDIOC-ENUMOUTPUT; ioctl, respectively. The +&v4l2-input; returned by the VIDIOC_ENUMINPUT +ioctl also contains signal status information applicable when the +current video input is queried. + + The &VIDIOC-G-INPUT; and &VIDIOC-G-OUTPUT; ioctl return the +index of the current video input or output. To select a different +input or output applications call the &VIDIOC-S-INPUT; and +&VIDIOC-S-OUTPUT; ioctl. Drivers must implement all the input ioctls +when the device has one or more inputs, all the output ioctls when the +device has one or more outputs. + + + + + Information about the current video input + + +&v4l2-input; input; +int index; + +if (-1 == ioctl (fd, &VIDIOC-G-INPUT;, &index)) { + perror ("VIDIOC_G_INPUT"); + exit (EXIT_FAILURE); +} + +memset (&input, 0, sizeof (input)); +input.index = index; + +if (-1 == ioctl (fd, &VIDIOC-ENUMINPUT;, &input)) { + perror ("VIDIOC_ENUMINPUT"); + exit (EXIT_FAILURE); +} + +printf ("Current input: %s\n", input.name); + + + + + Switching to the first video input + + +int index; + +index = 0; + +if (-1 == ioctl (fd, &VIDIOC-S-INPUT;, &index)) { + perror ("VIDIOC_S_INPUT"); + exit (EXIT_FAILURE); +} + + +
+ +
+ Audio Inputs and Outputs + + Audio inputs and outputs are physical connectors of a +device. Video capture devices have inputs, output devices have +outputs, zero or more each. Radio devices have no audio inputs or +outputs. They have exactly one tuner which in fact +is an audio source, but this API associates +tuners with video inputs or outputs only, and radio devices have +none of these. + Actually &v4l2-audio; ought to have a +tuner field like &v4l2-input;, not only +making the API more consistent but also permitting radio devices with +multiple tuners. + A connector on a TV card to loop back the received +audio signal to a sound card is not considered an audio output. + + Audio and video inputs and outputs are associated. Selecting +a video source also selects an audio source. This is most evident when +the video and audio source is a tuner. Further audio connectors can +combine with more than one video input or output. Assumed two +composite video inputs and two audio inputs exist, there may be up to +four valid combinations. The relation of video and audio connectors +is defined in the audioset field of the +respective &v4l2-input; or &v4l2-output;, where each bit represents +the index number, starting at zero, of one audio input or output. + + To learn about the number and attributes of the +available inputs and outputs applications can enumerate them with the +&VIDIOC-ENUMAUDIO; and &VIDIOC-ENUMAUDOUT; ioctl, respectively. The +&v4l2-audio; returned by the VIDIOC_ENUMAUDIO ioctl +also contains signal status information applicable when the current +audio input is queried. + + The &VIDIOC-G-AUDIO; and &VIDIOC-G-AUDOUT; ioctl report +the current audio input and output, respectively. Note that, unlike +&VIDIOC-G-INPUT; and &VIDIOC-G-OUTPUT; these ioctls return a structure +as VIDIOC_ENUMAUDIO and +VIDIOC_ENUMAUDOUT do, not just an index. + + To select an audio input and change its properties +applications call the &VIDIOC-S-AUDIO; ioctl. To select an audio +output (which presently has no changeable properties) applications +call the &VIDIOC-S-AUDOUT; ioctl. + + Drivers must implement all input ioctls when the device +has one or more inputs, all output ioctls when the device has one +or more outputs. When the device has any audio inputs or outputs the +driver must set the V4L2_CAP_AUDIO flag in the +&v4l2-capability; returned by the &VIDIOC-QUERYCAP; ioctl. + + + Information about the current audio input + + +&v4l2-audio; audio; + +memset (&audio, 0, sizeof (audio)); + +if (-1 == ioctl (fd, &VIDIOC-G-AUDIO;, &audio)) { + perror ("VIDIOC_G_AUDIO"); + exit (EXIT_FAILURE); +} + +printf ("Current input: %s\n", audio.name); + + + + + Switching to the first audio input + + +&v4l2-audio; audio; + +memset (&audio, 0, sizeof (audio)); /* clear audio.mode, audio.reserved */ + +audio.index = 0; + +if (-1 == ioctl (fd, &VIDIOC-S-AUDIO;, &audio)) { + perror ("VIDIOC_S_AUDIO"); + exit (EXIT_FAILURE); +} + + +
+ +
+ Tuners and Modulators + +
+ Tuners + + Video input devices can have one or more tuners +demodulating a RF signal. Each tuner is associated with one or more +video inputs, depending on the number of RF connectors on the tuner. +The type field of the respective +&v4l2-input; returned by the &VIDIOC-ENUMINPUT; ioctl is set to +V4L2_INPUT_TYPE_TUNER and its +tuner field contains the index number of +the tuner. + + Radio devices have exactly one tuner with index zero, no +video inputs. + + To query and change tuner properties applications use the +&VIDIOC-G-TUNER; and &VIDIOC-S-TUNER; ioctl, respectively. The +&v4l2-tuner; returned by VIDIOC_G_TUNER also +contains signal status information applicable when the tuner of the +current video input, or a radio tuner is queried. Note that +VIDIOC_S_TUNER does not switch the current tuner, +when there is more than one at all. The tuner is solely determined by +the current video input. Drivers must support both ioctls and set the +V4L2_CAP_TUNER flag in the &v4l2-capability; +returned by the &VIDIOC-QUERYCAP; ioctl when the device has one or +more tuners. +
+ +
+ Modulators + + Video output devices can have one or more modulators, uh, +modulating a video signal for radiation or connection to the antenna +input of a TV set or video recorder. Each modulator is associated with +one or more video outputs, depending on the number of RF connectors on +the modulator. The type field of the +respective &v4l2-output; returned by the &VIDIOC-ENUMOUTPUT; ioctl is +set to V4L2_OUTPUT_TYPE_MODULATOR and its +modulator field contains the index number +of the modulator. This specification does not define radio output +devices. + + To query and change modulator properties applications use +the &VIDIOC-G-MODULATOR; and &VIDIOC-S-MODULATOR; ioctl. Note that +VIDIOC_S_MODULATOR does not switch the current +modulator, when there is more than one at all. The modulator is solely +determined by the current video output. Drivers must support both +ioctls and set the V4L2_CAP_TUNER (sic) flag in +the &v4l2-capability; returned by the &VIDIOC-QUERYCAP; ioctl when the +device has one or more modulators. +
+ +
+ Radio Frequency + + To get and set the tuner or modulator radio frequency +applications use the &VIDIOC-G-FREQUENCY; and &VIDIOC-S-FREQUENCY; +ioctl which both take a pointer to a &v4l2-frequency;. These ioctls +are used for TV and radio devices alike. Drivers must support both +ioctls when the tuner or modulator ioctls are supported, or +when the device is a radio device. +
+ +
+ Satellite Receivers + + To be discussed. See also +proposals by Peter Schlaf, video4linux-list@redhat.com on 23 Oct 2002, +subject: "Re: [V4L] Re: v4l2 api". +
+
+ +
+ Video Standards + + Video devices typically support one or more different video +standards or variations of standards. Each video input and output may +support another set of standards. This set is reported by the +std field of &v4l2-input; and +&v4l2-output; returned by the &VIDIOC-ENUMINPUT; and +&VIDIOC-ENUMOUTPUT; ioctl, respectively. + + V4L2 defines one bit for each analog video standard +currently in use worldwide, and sets aside bits for driver defined +standards, ⪚ hybrid standards to watch NTSC video tapes on PAL TVs +and vice versa. Applications can use the predefined bits to select a +particular standard, although presenting the user a menu of supported +standards is preferred. To enumerate and query the attributes of the +supported standards applications use the &VIDIOC-ENUMSTD; ioctl. + + Many of the defined standards are actually just variations +of a few major standards. The hardware may in fact not distinguish +between them, or do so internal and switch automatically. Therefore +enumerated standards also contain sets of one or more standard +bits. + + Assume a hypothetic tuner capable of demodulating B/PAL, +G/PAL and I/PAL signals. The first enumerated standard is a set of B +and G/PAL, switched automatically depending on the selected radio +frequency in UHF or VHF band. Enumeration gives a "PAL-B/G" or "PAL-I" +choice. Similar a Composite input may collapse standards, enumerating +"PAL-B/G/H/I", "NTSC-M" and "SECAM-D/K". + Some users are already confused by technical terms PAL, +NTSC and SECAM. There is no point asking them to distinguish between +B, G, D, or K when the software or hardware can do that +automatically. + + + To query and select the standard used by the current video +input or output applications call the &VIDIOC-G-STD; and +&VIDIOC-S-STD; ioctl, respectively. The received +standard can be sensed with the &VIDIOC-QUERYSTD; ioctl. Note parameter of all these ioctls is a pointer to a &v4l2-std-id; type (a standard set), not an index into the standard enumeration. + An alternative to the current scheme is to use pointers +to indices as arguments of VIDIOC_G_STD and +VIDIOC_S_STD, the &v4l2-input; and +&v4l2-output; std field would be a set of +indices like audioset. + Indices are consistent with the rest of the API +and identify the standard unambiguously. In the present scheme of +things an enumerated standard is looked up by &v4l2-std-id;. Now the +standards supported by the inputs of a device can overlap. Just +assume the tuner and composite input in the example above both +exist on a device. An enumeration of "PAL-B/G", "PAL-H/I" suggests +a choice which does not exist. We cannot merge or omit sets, because +applications would be unable to find the standards reported by +VIDIOC_G_STD. That leaves separate enumerations +for each input. Also selecting a standard by &v4l2-std-id; can be +ambiguous. Advantage of this method is that applications need not +identify the standard indirectly, after enumerating.So in +summary, the lookup itself is unavoidable. The difference is only +whether the lookup is necessary to find an enumerated standard or to +switch to a standard by &v4l2-std-id;. + Drivers must implement all video standard ioctls +when the device has one or more video inputs or outputs. + + Special rules apply to USB cameras where the notion of video +standards makes little sense. More generally any capture device, +output devices accordingly, which is + + incapable of capturing fields or frames at the nominal +rate of the video standard, or + + + where timestamps refer +to the instant the field or frame was received by the driver, not the +capture time, or + + + where sequence numbers +refer to the frames received by the driver, not the captured +frames. + + Here the driver shall set the +std field of &v4l2-input; and &v4l2-output; +to zero, the VIDIOC_G_STD, +VIDIOC_S_STD, +VIDIOC_QUERYSTD and +VIDIOC_ENUMSTD ioctls shall return the +&EINVAL;. + See for a rationale. Probably +even USB cameras follow some well known video standard. It might have +been better to explicitly indicate elsewhere if a device cannot live +up to normal expectations, instead of this exception. + + + + Information about the current video standard + + +&v4l2-std-id; std_id; +&v4l2-standard; standard; + +if (-1 == ioctl (fd, &VIDIOC-G-STD;, &std_id)) { + /* Note when VIDIOC_ENUMSTD always returns EINVAL this + is no video device or it falls under the USB exception, + and VIDIOC_G_STD returning EINVAL is no error. */ + + perror ("VIDIOC_G_STD"); + exit (EXIT_FAILURE); +} + +memset (&standard, 0, sizeof (standard)); +standard.index = 0; + +while (0 == ioctl (fd, &VIDIOC-ENUMSTD;, &standard)) { + if (standard.id & std_id) { + printf ("Current video standard: %s\n", standard.name); + exit (EXIT_SUCCESS); + } + + standard.index++; +} + +/* EINVAL indicates the end of the enumeration, which cannot be + empty unless this device falls under the USB exception. */ + +if (errno == EINVAL || standard.index == 0) { + perror ("VIDIOC_ENUMSTD"); + exit (EXIT_FAILURE); +} + + + + + Listing the video standards supported by the current +input + + +&v4l2-input; input; +&v4l2-standard; standard; + +memset (&input, 0, sizeof (input)); + +if (-1 == ioctl (fd, &VIDIOC-G-INPUT;, &input.index)) { + perror ("VIDIOC_G_INPUT"); + exit (EXIT_FAILURE); +} + +if (-1 == ioctl (fd, &VIDIOC-ENUMINPUT;, &input)) { + perror ("VIDIOC_ENUM_INPUT"); + exit (EXIT_FAILURE); +} + +printf ("Current input %s supports:\n", input.name); + +memset (&standard, 0, sizeof (standard)); +standard.index = 0; + +while (0 == ioctl (fd, &VIDIOC-ENUMSTD;, &standard)) { + if (standard.id & input.std) + printf ("%s\n", standard.name); + + standard.index++; +} + +/* EINVAL indicates the end of the enumeration, which cannot be + empty unless this device falls under the USB exception. */ + +if (errno != EINVAL || standard.index == 0) { + perror ("VIDIOC_ENUMSTD"); + exit (EXIT_FAILURE); +} + + + + + Selecting a new video standard + + +&v4l2-input; input; +&v4l2-std-id; std_id; + +memset (&input, 0, sizeof (input)); + +if (-1 == ioctl (fd, &VIDIOC-G-INPUT;, &input.index)) { + perror ("VIDIOC_G_INPUT"); + exit (EXIT_FAILURE); +} + +if (-1 == ioctl (fd, &VIDIOC-ENUMINPUT;, &input)) { + perror ("VIDIOC_ENUM_INPUT"); + exit (EXIT_FAILURE); +} + +if (0 == (input.std & V4L2_STD_PAL_BG)) { + fprintf (stderr, "Oops. B/G PAL is not supported.\n"); + exit (EXIT_FAILURE); +} + +/* Note this is also supposed to work when only B + or G/PAL is supported. */ + +std_id = V4L2_STD_PAL_BG; + +if (-1 == ioctl (fd, &VIDIOC-S-STD;, &std_id)) { + perror ("VIDIOC_S_STD"); + exit (EXIT_FAILURE); +} + + +
+ + &sub-controls; + +
+ Data Formats + +
+ Data Format Negotiation + + Different devices exchange different kinds of data with +applications, for example video images, raw or sliced VBI data, RDS +datagrams. Even within one kind many different formats are possible, +in particular an abundance of image formats. Although drivers must +provide a default and the selection persists across closing and +reopening a device, applications should always negotiate a data format +before engaging in data exchange. Negotiation means the application +asks for a particular format and the driver selects and reports the +best the hardware can do to satisfy the request. Of course +applications can also just query the current selection. + + A single mechanism exists to negotiate all data formats +using the aggregate &v4l2-format; and the &VIDIOC-G-FMT; and +&VIDIOC-S-FMT; ioctls. Additionally the &VIDIOC-TRY-FMT; ioctl can be +used to examine what the hardware could do, +without actually selecting a new data format. The data formats +supported by the V4L2 API are covered in the respective device section +in . For a closer look at image formats see +. + + The VIDIOC_S_FMT ioctl is a major +turning-point in the initialization sequence. Prior to this point +multiple panel applications can access the same device concurrently to +select the current input, change controls or modify other properties. +The first VIDIOC_S_FMT assigns a logical stream +(video data, VBI data etc.) exclusively to one file descriptor. + + Exclusive means no other application, more precisely no +other file descriptor, can grab this stream or change device +properties inconsistent with the negotiated parameters. A video +standard change for example, when the new standard uses a different +number of scan lines, can invalidate the selected image format. +Therefore only the file descriptor owning the stream can make +invalidating changes. Accordingly multiple file descriptors which +grabbed different logical streams prevent each other from interfering +with their settings. When for example video overlay is about to start +or already in progress, simultaneous video capturing may be restricted +to the same cropping and image size. + + When applications omit the +VIDIOC_S_FMT ioctl its locking side effects are +implied by the next step, the selection of an I/O method with the +&VIDIOC-REQBUFS; ioctl or implicit with the first &func-read; or +&func-write; call. + + Generally only one logical stream can be assigned to a +file descriptor, the exception being drivers permitting simultaneous +video capturing and overlay using the same file descriptor for +compatibility with V4L and earlier versions of V4L2. Switching the +logical stream or returning into "panel mode" is possible by closing +and reopening the device. Drivers may support a +switch using VIDIOC_S_FMT. + + All drivers exchanging data with +applications must support the VIDIOC_G_FMT and +VIDIOC_S_FMT ioctl. Implementation of the +VIDIOC_TRY_FMT is highly recommended but +optional. +
+ +
+ Image Format Enumeration + + Apart of the generic format negotiation functions +a special ioctl to enumerate all image formats supported by video +capture, overlay or output devices is available. + Enumerating formats an application has no a-priori +knowledge of (otherwise it could explicitely ask for them and need not +enumerate) seems useless, but there are applications serving as proxy +between drivers and the actual video applications for which this is +useful. + + + The &VIDIOC-ENUM-FMT; ioctl must be supported +by all drivers exchanging image data with applications. + + + Drivers are not supposed to convert image formats in +kernel space. They must enumerate only formats directly supported by +the hardware. If necessary driver writers should publish an example +conversion routine or library for integration into applications. + +
+
+ +
+ Image Cropping, Insertion and Scaling + + Some video capture devices can sample a subsection of the +picture and shrink or enlarge it to an image of arbitrary size. We +call these abilities cropping and scaling. Some video output devices +can scale an image up or down and insert it at an arbitrary scan line +and horizontal offset into a video signal. + + Applications can use the following API to select an area in +the video signal, query the default area and the hardware limits. +Despite their name, the &VIDIOC-CROPCAP;, &VIDIOC-G-CROP; +and &VIDIOC-S-CROP; ioctls apply to input as well as output +devices. + + Scaling requires a source and a target. On a video capture +or overlay device the source is the video signal, and the cropping +ioctls determine the area actually sampled. The target are images +read by the application or overlaid onto the graphics screen. Their +size (and position for an overlay) is negotiated with the +&VIDIOC-G-FMT; and &VIDIOC-S-FMT; ioctls. + + On a video output device the source are the images passed in +by the application, and their size is again negotiated with the +VIDIOC_G/S_FMT ioctls, or may be encoded in a +compressed video stream. The target is the video signal, and the +cropping ioctls determine the area where the images are +inserted. + + Source and target rectangles are defined even if the device +does not support scaling or the VIDIOC_G/S_CROP +ioctls. Their size (and position where applicable) will be fixed in +this case. All capture and output device must support the +VIDIOC_CROPCAP ioctl such that applications can +determine if scaling takes place. + +
+ Cropping Structures + +
+ Image Cropping, Insertion and Scaling + + + + + + + + + The cropping, insertion and scaling process + + +
+ + For capture devices the coordinates of the top left +corner, width and height of the area which can be sampled is given by +the bounds substructure of the +&v4l2-cropcap; returned by the VIDIOC_CROPCAP +ioctl. To support a wide range of hardware this specification does not +define an origin or units. However by convention drivers should +horizontally count unscaled samples relative to 0H (the leading edge +of the horizontal sync pulse, see ). +Vertically ITU-R line +numbers of the first field (, ), multiplied by two if the driver can capture both +fields. + + The top left corner, width and height of the source +rectangle, that is the area actually sampled, is given by &v4l2-crop; +using the same coordinate system as &v4l2-cropcap;. Applications can +use the VIDIOC_G_CROP and +VIDIOC_S_CROP ioctls to get and set this +rectangle. It must lie completely within the capture boundaries and +the driver may further adjust the requested size and/or position +according to hardware limitations. + + Each capture device has a default source rectangle, given +by the defrect substructure of +&v4l2-cropcap;. The center of this rectangle shall align with the +center of the active picture area of the video signal, and cover what +the driver writer considers the complete picture. Drivers shall reset +the source rectangle to the default when the driver is first loaded, +but not later. + + For output devices these structures and ioctls are used +accordingly, defining the target rectangle where +the images will be inserted into the video signal. + +
+ +
+ Scaling Adjustments + + Video hardware can have various cropping, insertion and +scaling limitations. It may only scale up or down, support only +discrete scaling factors, or have different scaling abilities in +horizontal and vertical direction. Also it may not support scaling at +all. At the same time the &v4l2-crop; rectangle may have to be +aligned, and both the source and target rectangles may have arbitrary +upper and lower size limits. In particular the maximum +width and height +in &v4l2-crop; may be smaller than the +&v4l2-cropcap;.bounds area. Therefore, as +usual, drivers are expected to adjust the requested parameters and +return the actual values selected. + + Applications can change the source or the target rectangle +first, as they may prefer a particular image size or a certain area in +the video signal. If the driver has to adjust both to satisfy hardware +limitations, the last requested rectangle shall take priority, and the +driver should preferably adjust the opposite one. The &VIDIOC-TRY-FMT; +ioctl however shall not change the driver state and therefore only +adjust the requested rectangle. + + Suppose scaling on a video capture device is restricted to +a factor 1:1 or 2:1 in either direction and the target image size must +be a multiple of 16 × 16 pixels. The source cropping +rectangle is set to defaults, which are also the upper limit in this +example, of 640 × 400 pixels at offset 0, 0. An +application requests an image size of 300 × 225 +pixels, assuming video will be scaled down from the "full picture" +accordingly. The driver sets the image size to the closest possible +values 304 × 224, then chooses the cropping rectangle +closest to the requested size, that is 608 × 224 +(224 × 2:1 would exceed the limit 400). The offset +0, 0 is still valid, thus unmodified. Given the default cropping +rectangle reported by VIDIOC_CROPCAP the +application can easily propose another offset to center the cropping +rectangle. + + Now the application may insist on covering an area using a +picture aspect ratio closer to the original request, so it asks for a +cropping rectangle of 608 × 456 pixels. The present +scaling factors limit cropping to 640 × 384, so the +driver returns the cropping size 608 × 384 and adjusts +the image size to closest possible 304 × 192. + +
+ +
+ Examples + + Source and target rectangles shall remain unchanged across +closing and reopening a device, such that piping data into or out of a +device will work without special preparations. More advanced +applications should ensure the parameters are suitable before starting +I/O. + + + Resetting the cropping parameters + + (A video capture device is assumed; change +V4L2_BUF_TYPE_VIDEO_CAPTURE for other +devices.) + + +&v4l2-cropcap; cropcap; +&v4l2-crop; crop; + +memset (&cropcap, 0, sizeof (cropcap)); +cropcap.type = V4L2_BUF_TYPE_VIDEO_CAPTURE; + +if (-1 == ioctl (fd, &VIDIOC-CROPCAP;, &cropcap)) { + perror ("VIDIOC_CROPCAP"); + exit (EXIT_FAILURE); +} + +memset (&crop, 0, sizeof (crop)); +crop.type = V4L2_BUF_TYPE_VIDEO_CAPTURE; +crop.c = cropcap.defrect; + +/* Ignore if cropping is not supported (EINVAL). */ + +if (-1 == ioctl (fd, &VIDIOC-S-CROP;, &crop) + && errno != EINVAL) { + perror ("VIDIOC_S_CROP"); + exit (EXIT_FAILURE); +} + + + + + Simple downscaling + + (A video capture device is assumed.) + + +&v4l2-cropcap; cropcap; +&v4l2-format; format; + +reset_cropping_parameters (); + +/* Scale down to 1/4 size of full picture. */ + +memset (&format, 0, sizeof (format)); /* defaults */ + +format.type = V4L2_BUF_TYPE_VIDEO_CAPTURE; + +format.fmt.pix.width = cropcap.defrect.width >> 1; +format.fmt.pix.height = cropcap.defrect.height >> 1; +format.fmt.pix.pixelformat = V4L2_PIX_FMT_YUYV; + +if (-1 == ioctl (fd, &VIDIOC-S-FMT;, &format)) { + perror ("VIDIOC_S_FORMAT"); + exit (EXIT_FAILURE); +} + +/* We could check the actual image size now, the actual scaling factor + or if the driver can scale at all. */ + + + + + Selecting an output area + + +&v4l2-cropcap cropcap; +&v4l2-crop crop; + +memset (&cropcap, 0, sizeof (cropcap)); +cropcap.type = V4L2_BUF_TYPE_VIDEO_OUTPUT; + +if (-1 == ioctl (fd, VIDIOC_CROPCAP, &cropcap)) { + perror ("VIDIOC_CROPCAP"); + exit (EXIT_FAILURE); +} + +memset (&crop, 0, sizeof (crop)); + +crop.type = V4L2_BUF_TYPE_VIDEO_OUTPUT; +crop.c = cropcap.defrect; + +/* Scale the width and height to 50 % of their original size + and center the output. */ + +crop.c.width /= 2; +crop.c.height /= 2; +crop.c.left += crop.c.width / 2; +crop.c.top += crop.c.height / 2; + +/* Ignore if cropping is not supported (EINVAL). */ + +if (-1 == ioctl (fd, VIDIOC_S_CROP, &crop) + && errno != EINVAL) { + perror ("VIDIOC_S_CROP"); + exit (EXIT_FAILURE); +} + + + + + Current scaling factor and pixel aspect + + (A video capture device is assumed.) + + +&v4l2-cropcap; cropcap; +&v4l2-crop; crop; +&v4l2-format; format; +double hscale, vscale; +double aspect; +int dwidth, dheight; + +memset (&cropcap, 0, sizeof (cropcap)); +cropcap.type = V4L2_BUF_TYPE_VIDEO_CAPTURE; + +if (-1 == ioctl (fd, &VIDIOC-CROPCAP;, &cropcap)) { + perror ("VIDIOC_CROPCAP"); + exit (EXIT_FAILURE); +} + +memset (&crop, 0, sizeof (crop)); +crop.type = V4L2_BUF_TYPE_VIDEO_CAPTURE; + +if (-1 == ioctl (fd, &VIDIOC-G-CROP;, &crop)) { + if (errno != EINVAL) { + perror ("VIDIOC_G_CROP"); + exit (EXIT_FAILURE); + } + + /* Cropping not supported. */ + crop.c = cropcap.defrect; +} + +memset (&format, 0, sizeof (format)); +format.fmt.type = V4L2_BUF_TYPE_VIDEO_CAPTURE; + +if (-1 == ioctl (fd, &VIDIOC-G-FMT;, &format)) { + perror ("VIDIOC_G_FMT"); + exit (EXIT_FAILURE); +} + +/* The scaling applied by the driver. */ + +hscale = format.fmt.pix.width / (double) crop.c.width; +vscale = format.fmt.pix.height / (double) crop.c.height; + +aspect = cropcap.pixelaspect.numerator / + (double) cropcap.pixelaspect.denominator; +aspect = aspect * hscale / vscale; + +/* Devices following ITU-R BT.601 do not capture + square pixels. For playback on a computer monitor + we should scale the images to this size. */ + +dwidth = format.fmt.pix.width / aspect; +dheight = format.fmt.pix.height; + + +
+
+ +
+ Streaming Parameters + + Streaming parameters are intended to optimize the video +capture process as well as I/O. Presently applications can request a +high quality capture mode with the &VIDIOC-S-PARM; ioctl. + + The current video standard determines a nominal number of +frames per second. If less than this number of frames is to be +captured or output, applications can request frame skipping or +duplicating on the driver side. This is especially useful when using +the &func-read; or &func-write;, which are not augmented by timestamps +or sequence counters, and to avoid unneccessary data copying. + + Finally these ioctls can be used to determine the number of +buffers used internally by a driver in read/write mode. For +implications see the section discussing the &func-read; +function. + + To get and set the streaming parameters applications call +the &VIDIOC-G-PARM; and &VIDIOC-S-PARM; ioctl, respectively. They take +a pointer to a &v4l2-streamparm;, which contains a union holding +separate parameters for input and output devices. + + These ioctls are optional, drivers need not implement +them. If so, they return the &EINVAL;. +
+ + diff --git a/v4l2-spec/compat.sgml b/v4l2-spec/compat.sgml new file mode 100644 index 000000000..3eb873c70 --- /dev/null +++ b/v4l2-spec/compat.sgml @@ -0,0 +1,2335 @@ + Changes + + The following chapters document the evolution of the V4L2 API, +errata or extensions. They are also intended to help application and +driver writers to port or update their code. + +
+ Differences between V4L and V4L2 + + The Video For Linux API was first introduced in Linux 2.1 to +unify and replace various TV and radio device related interfaces, +developed independently by driver writers in prior years. Starting +with Linux 2.5 the much improved V4L2 API replaces the V4L API, +although existing drivers will continue to support V4L applications in +the future, either directly or through the V4L2 compatibility layer in +the videodev kernel module translating ioctls on +the fly. For a transition period not all drivers will support the V4L2 +API. + +
+ Opening and Closing Devices + + For compatibility reasons the character device file names +recommended for V4L2 video capture, overlay, radio, teletext and raw +vbi capture devices did not change from those used by V4L. They are +listed in and below in . + + The V4L videodev module automatically +assigns minor numbers to drivers in load order, depending on the +registered device type. We recommend that V4L2 drivers by default +register devices with the same numbers, but the system administrator +can assign arbitrary minor numbers using driver module options. The +major device number remains 81. + + + V4L Device Types, Names and Numbers + + + + Device Type + File Name + Minor Numbers + + + + + Video capture and overlay + /dev/video and +/dev/bttv0 According to +Documentation/devices.txt these should be symbolic links to +/dev/video0. Note the original bttv interface is +not compatible with V4L or V4L2. , +/dev/video0 to +/dev/video63 + 0-63 + + + Radio receiver + /dev/radio + According to +Documentation/devices.txt a symbolic link to +/dev/radio0. + , /dev/radio0 to +/dev/radio63 + 64-127 + + + Teletext decoder + /dev/vtx, +/dev/vtx0 to +/dev/vtx31 + 192-223 + + + Raw VBI capture + /dev/vbi, +/dev/vbi0 to +/dev/vbi31 + 224-255 + + + +
+ + V4L prohibits (or used to prohibit) multiple opens of a +device file. V4L2 drivers may support multiple +opens, see for details and consequences. + + V4L drivers respond to V4L2 ioctls with an &EINVAL;. The +compatibility layer in the V4L2 videodev module +can translate V4L ioctl requests to their V4L2 counterpart, however a +V4L2 driver usually needs more preparation to become fully V4L +compatible. This is covered in more detail in . +
+ +
+ Querying Capabilities + + The V4L VIDIOCGCAP ioctl is +equivalent to V4L2's &VIDIOC-QUERYCAP;. + + The name field in struct +video_capability became +card in &v4l2-capability;, +type was replaced by +capabilities. Note V4L2 does not +distinguish between device types like this, better think of basic +video input, video output and radio devices supporting a set of +related functions like video capturing, video overlay and VBI +capturing. See for an +introduction. + + + + struct +video_capability +type + &v4l2-capability; +capabilities flags + Purpose + + + + + VID_TYPE_CAPTURE + V4L2_CAP_VIDEO_CAPTURE + The video +capture interface is supported. + + + VID_TYPE_TUNER + V4L2_CAP_TUNER + The device has a tuner or +modulator. + + + VID_TYPE_TELETEXT + V4L2_CAP_VBI_CAPTURE + The raw VBI +capture interface is supported. + + + VID_TYPE_OVERLAY + V4L2_CAP_VIDEO_OVERLAY + The video +overlay interface is supported. + + + VID_TYPE_CHROMAKEY + V4L2_FBUF_CAP_CHROMAKEY in +field capability of +&v4l2-framebuffer; + Whether chromakey overlay is supported. For +more information on overlay see +. + + + VID_TYPE_CLIPPING + V4L2_FBUF_CAP_LIST_CLIPPING +and V4L2_FBUF_CAP_BITMAP_CLIPPING in field +capability of &v4l2-framebuffer; + Whether clipping the overlaid image is +supported, see . + + + VID_TYPE_FRAMERAM + V4L2_FBUF_CAP_EXTERNOVERLAY +not set in field +capability of &v4l2-framebuffer; + Whether overlay overwrites frame buffer memory, +see . + + + VID_TYPE_SCALES + - + This flag indicates if the hardware can scale +images. The V4L2 API implies the scale factor by setting the cropping +dimensions and image size with the &VIDIOC-S-CROP; and &VIDIOC-S-FMT; +ioctl, respectively. The driver returns the closest sizes possible. +For more information on cropping and scaling see . + + + VID_TYPE_MONOCHROME + - + Applications can enumerate the supported image +formats with the &VIDIOC-ENUM-FMT; ioctl to determine if the device +supports grey scale capturing only. For more information on image +formats see . + + + VID_TYPE_SUBCAPTURE + - + Applications can call the &VIDIOC-G-CROP; ioctl +to determine if the device supports capturing a subsection of the full +picture ("cropping" in V4L2). If not, the ioctl returns the &EINVAL;. +For more information on cropping and scaling see . + + + VID_TYPE_MPEG_DECODER + - + Applications can enumerate the supported image +formats with the &VIDIOC-ENUM-FMT; ioctl to determine if the device +supports MPEG streams. + + + VID_TYPE_MPEG_ENCODER + - + See above. + + + VID_TYPE_MJPEG_DECODER + - + See above. + + + VID_TYPE_MJPEG_ENCODER + - + See above. + + + + + + The audios field was replaced +by capabilities flag +V4L2_CAP_AUDIO, indicating +if the device has any audio inputs or outputs. To +determine their number applications can enumerate audio inputs with +the &VIDIOC-G-AUDIO; ioctl. The audio ioctls are described in . + + The maxwidth, +maxheight, +minwidth and +minheight fields were removed. Calling the +&VIDIOC-S-FMT; or &VIDIOC-TRY-FMT; ioctl with the desired dimensions +returns the closest size possible, taking into account the current +video standard, cropping and scaling limitations. +
+ +
+ Video Sources + + V4L provides the VIDIOCGCHAN and +VIDIOCSCHAN ioctl using struct +video_channel to enumerate +the video inputs of a V4L device. The equivalent V4L2 ioctls +are &VIDIOC-ENUMINPUT;, &VIDIOC-G-INPUT; and &VIDIOC-S-INPUT; +using &v4l2-input; as discussed in . + + The channel field counting +inputs was renamed to index, the video +input types were renamed as follows: + + + + struct video_channel +type + &v4l2-input; +type + + + + + VIDEO_TYPE_TV + V4L2_INPUT_TYPE_TUNER + + + VIDEO_TYPE_CAMERA + V4L2_INPUT_TYPE_CAMERA + + + + + + Unlike the tuners field +expressing the number of tuners of this input, V4L2 assumes each video +input is connected to at most one tuner. However a tuner can have more +than one input, &ie; RF connectors, and a device can have multiple +tuners. The index number of the tuner associated with the input, if +any, is stored in field tuner of +&v4l2-input;. Enumeration of tuners is discussed in . + + The redundant VIDEO_VC_TUNER flag was +dropped. Video inputs associated with a tuner are of type +V4L2_INPUT_TYPE_TUNER. The +VIDEO_VC_AUDIO flag was replaced by the +audioset field. V4L2 considers devices with +up to 32 audio inputs. Each set bit in the +audioset field represents one audio input +this video input combines with. For information about audio inputs and +how to switch between them see . + + The norm field describing the +supported video standards was replaced by +std. The V4L specification mentions a flag +VIDEO_VC_NORM indicating whether the standard can +be changed. This flag was a later addition together with the +norm field and has been removed in the +meantime. V4L2 has a similar, albeit more comprehensive approach +to video standards, see for more +information. +
+ +
+ Tuning + + The V4L VIDIOCGTUNER and +VIDIOCSTUNER ioctl and struct +video_tuner can be used to enumerate the +tuners of a V4L TV or radio device. The equivalent V4L2 ioctls are +&VIDIOC-G-TUNER; and &VIDIOC-S-TUNER; using &v4l2-tuner;. Tuners are +covered in . + + The tuner field counting tuners +was renamed to index. The fields +name, rangelow +and rangehigh remained unchanged. + + The VIDEO_TUNER_PAL, +VIDEO_TUNER_NTSC and +VIDEO_TUNER_SECAM flags indicating the supported +video standards were dropped. This information is now contained in the +associated &v4l2-input;. No replacement exists for the +VIDEO_TUNER_NORM flag indicating whether the +video standard can be switched. The mode +field to select a different video standard was replaced by a whole new +set of ioctls and structures described in . +Due to its ubiquity it should be mentioned the BTTV driver supports +several standards in addition to the regular +VIDEO_MODE_PAL (0), +VIDEO_MODE_NTSC, +VIDEO_MODE_SECAM and +VIDEO_MODE_AUTO (3). Namely N/PAL Argentina, +M/PAL, N/PAL, and NTSC Japan with numbers 3-6 (sic). + + The VIDEO_TUNER_STEREO_ON flag +indicating stereo reception became +V4L2_TUNER_SUB_STEREO in field +rxsubchans. This field also permits the +detection of monaural and bilingual audio, see the definition of +&v4l2-tuner; for details. Presently no replacement exists for the +VIDEO_TUNER_RDS_ON and +VIDEO_TUNER_MBS_ON flags. + + The VIDEO_TUNER_LOW flag was renamed +to V4L2_TUNER_CAP_LOW in the &v4l2-tuner; +capability field. + + The VIDIOCGFREQ and +VIDIOCSFREQ ioctl to change the tuner frequency +where renamed to &VIDIOC-G-FREQUENCY; and &VIDIOC-S-FREQUENCY;. They +take a pointer to a &v4l2-frequency; instead of an unsigned long +integer. +
+ +
+ Image Properties + + V4L2 has no equivalent of the +VIDIOCGPICT and VIDIOCSPICT +ioctl and struct video_picture. The following +fields where replaced by V4L2 controls accessible with the +&VIDIOC-QUERYCTRL;, &VIDIOC-G-CTRL; and &VIDIOC-S-CTRL; ioctls: + + + + struct video_picture + V4L2 Control ID + + + + + brightness + V4L2_CID_BRIGHTNESS + + + hue + V4L2_CID_HUE + + + colour + V4L2_CID_SATURATION + + + contrast + V4L2_CID_CONTRAST + + + whiteness + V4L2_CID_WHITENESS + + + + + + The V4L picture controls are assumed to range from 0 to +65535 with no particular reset value. The V4L2 API permits arbitrary +limits and defaults which can be queried with the &VIDIOC-QUERYCTRL; +ioctl. For general information about controls see . + + The depth (average number of +bits per pixel) of a video image is implied by the selected image +format. V4L2 does not explicitely provide such information assuming +applications recognizing the format are aware of the image depth and +others need not know. The palette field +moved into the &v4l2-pix-format;: + + + + struct video_picture +palette + &v4l2-pix-format; +pixfmt + + + + + VIDEO_PALETTE_GREY + V4L2_PIX_FMT_GREY + + + VIDEO_PALETTE_HI240 + V4L2_PIX_FMT_HI240 + This is a custom format used by the BTTV +driver, not one of the V4L2 standard formats. + + + + VIDEO_PALETTE_RGB565 + V4L2_PIX_FMT_RGB565 + + + VIDEO_PALETTE_RGB555 + V4L2_PIX_FMT_RGB555 + + + VIDEO_PALETTE_RGB24 + V4L2_PIX_FMT_BGR24 + + + VIDEO_PALETTE_RGB32 + V4L2_PIX_FMT_BGR32 + Presumably all V4L RGB formats are +little-endian, although some drivers might interpret them according to machine endianess. V4L2 defines little-endian, big-endian and red/blue +swapped variants. For details see . + + + + VIDEO_PALETTE_YUV422 + V4L2_PIX_FMT_YUYV + + + VIDEO_PALETTE_YUYV + VIDEO_PALETTE_YUV422 +and VIDEO_PALETTE_YUYV are the same formats. Some +V4L drivers respond to one, some to the other. + + V4L2_PIX_FMT_YUYV + + + VIDEO_PALETTE_UYVY + V4L2_PIX_FMT_UYVY + + + VIDEO_PALETTE_YUV420 + None + + + VIDEO_PALETTE_YUV411 + V4L2_PIX_FMT_Y41P + Not to be confused with +V4L2_PIX_FMT_YUV411P, which is a planar +format. + + + VIDEO_PALETTE_RAW + None V4L explains this +as: "RAW capture (BT848)" + + + VIDEO_PALETTE_YUV422P + V4L2_PIX_FMT_YUV422P + + + VIDEO_PALETTE_YUV411P + V4L2_PIX_FMT_YUV411P + Not to be confused with +V4L2_PIX_FMT_Y41P, which is a packed +format. + + + VIDEO_PALETTE_YUV420P + V4L2_PIX_FMT_YVU420 + + + VIDEO_PALETTE_YUV410P + V4L2_PIX_FMT_YVU410 + + + + + + V4L2 image formats are defined in . The image format can be selected with the +&VIDIOC-S-FMT; ioctl. +
+ +
+ Audio + + The VIDIOCGAUDIO and +VIDIOCSAUDIO ioctl and struct +video_audio are used to enumerate the +audio inputs of a V4L device. The equivalent V4L2 ioctls are +&VIDIOC-G-AUDIO; and &VIDIOC-S-AUDIO; using &v4l2-audio; as +discussed in . + + The audio "channel number" +field counting audio inputs was renamed to +index. + + On VIDIOCSAUDIO the +mode field selects one +of the VIDEO_SOUND_MONO, +VIDEO_SOUND_STEREO, +VIDEO_SOUND_LANG1 or +VIDEO_SOUND_LANG2 audio demodulation modes. When +the current audio standard is BTSC +VIDEO_SOUND_LANG2 refers to SAP and +VIDEO_SOUND_LANG1 is meaningless. Also +undocumented in the V4L specification, there is no way to query the +selected mode. On VIDIOCGAUDIO the driver returns +the actually received audio programmes in this +field. In the V4L2 API this information is stored in the &v4l2-tuner; +rxsubchans and +audmode fields, respectively. See for more information on tuners. Related to audio +modes &v4l2-audio; also reports if this is a mono or stereo +input, regardless if the source is a tuner. + + The following fields where replaced by V4L2 controls +accessible with the &VIDIOC-QUERYCTRL;, &VIDIOC-G-CTRL; and +&VIDIOC-S-CTRL; ioctls: + + + + struct +video_audio + V4L2 Control ID + + + + + volume + V4L2_CID_AUDIO_VOLUME + + + bass + V4L2_CID_AUDIO_BASS + + + treble + V4L2_CID_AUDIO_TREBLE + + + balance + V4L2_CID_AUDIO_BALANCE + + + + + + To determine which of these controls are supported by a +driver V4L provides the flags +VIDEO_AUDIO_VOLUME, +VIDEO_AUDIO_BASS, +VIDEO_AUDIO_TREBLE and +VIDEO_AUDIO_BALANCE. In the V4L2 API the +&VIDIOC-QUERYCTRL; ioctl reports if the respective control is +supported. Accordingly the VIDEO_AUDIO_MUTABLE +and VIDEO_AUDIO_MUTE flags where replaced by the +boolean V4L2_CID_AUDIO_MUTE control. + + All V4L2 controls have a step +attribute replacing the struct video_audio +step field. The V4L audio controls are +assumed to range from 0 to 65535 with no particular reset value. The +V4L2 API permits arbitrary limits and defaults which can be queried +with the &VIDIOC-QUERYCTRL; ioctl. For general information about +controls see . +
+ +
+ Frame Buffer Overlay + + The V4L2 ioctls equivalent to +VIDIOCGFBUF and VIDIOCSFBUF +are &VIDIOC-G-FBUF; and &VIDIOC-S-FBUF;. The +base field of struct +video_buffer remained unchanged, except V4L2 +defines a flag to indicate non-destructive overlays instead of a +NULL pointer. All other fields moved into the +&v4l2-pix-format; fmt substructure of +&v4l2-framebuffer;. The depth field was +replaced by pixelformat. See for a list of RGB formats and their +respective color depths. + + Instead of the special ioctls +VIDIOCGWIN and VIDIOCSWIN +V4L2 uses the general-purpose data format negotiation ioctls +&VIDIOC-G-FMT; and &VIDIOC-S-FMT;. They take a pointer to a +&v4l2-format; as argument. Here the win +member of the fmt union is used, a +&v4l2-window;. + + The x, +y, width and +height fields of struct +video_window moved into &v4l2-rect; +substructure w of struct +v4l2_window. The +chromakey, +clips, and +clipcount fields remained unchanged. Struct +video_clip was renamed to &v4l2-clip;, also +containing a struct v4l2_rect, but the +semantics are still the same. + + The VIDEO_WINDOW_INTERLACE flag was +dropped. Instead applications must set the +field field to +V4L2_FIELD_ANY or +V4L2_FIELD_INTERLACED. The +VIDEO_WINDOW_CHROMAKEY flag moved into +&v4l2-framebuffer;, under the new name +V4L2_FBUF_FLAG_CHROMAKEY. + + In V4L, storing a bitmap pointer in +clips and setting +clipcount to +VIDEO_CLIP_BITMAP (-1) requests bitmap +clipping, using a fixed size bitmap of 1024 × 625 bits. Struct +v4l2_window has a separate +bitmap pointer field for this purpose and +the bitmap size is determined by w.width and +w.height. + + The VIDIOCCAPTURE ioctl to enable or +disable overlay was renamed to &VIDIOC-OVERLAY;. +
+ +
+ Cropping + + To capture only a subsection of the full picture V4L +defines the VIDIOCGCAPTURE and +VIDIOCSCAPTURE ioctls using struct +video_capture. The equivalent V4L2 ioctls are +&VIDIOC-G-CROP; and &VIDIOC-S-CROP; using &v4l2-crop;, and the related +&VIDIOC-CROPCAP; ioctl. This is a rather complex matter, see + for details. + + The x, +y, width and +height fields moved into &v4l2-rect; +substructure c of struct +v4l2_crop. The +decimation field was dropped. In the V4L2 +API the scaling factor is implied by the size of the cropping +rectangle and the size of the captured or overlaid image. + + The VIDEO_CAPTURE_ODD +and VIDEO_CAPTURE_EVEN flags to capture only the +odd or even field, respectively, were replaced by +V4L2_FIELD_TOP and +V4L2_FIELD_BOTTOM in the field named +field of &v4l2-pix-format; and +&v4l2-window;. These structures are used to select a capture or +overlay format with the &VIDIOC-S-FMT; ioctl. +
+ +
+ Reading Images, Memory Mapping + +
+ Capturing using the read method + + There is no essential difference between reading images +from a V4L or V4L2 device using the &func-read; function, however V4L2 +drivers are not required to support this I/O method. Applications can +determine if the function is available with the &VIDIOC-QUERYCAP; +ioctl. All V4L2 devices exchanging data with applications must support +the &func-select; and &func-poll; functions. + + To select an image format and size, V4L provides the +VIDIOCSPICT and VIDIOCSWIN +ioctls. V4L2 uses the general-purpose data format negotiation ioctls +&VIDIOC-G-FMT; and &VIDIOC-S-FMT;. They take a pointer to a +&v4l2-format; as argument, here the &v4l2-pix-format; named +pix of its fmt +union is used. + + For more information about the V4L2 read interface see +. +
+
+ Capturing using memory mapping + + Applications can read from V4L devices by mapping +buffers in device memory, or more often just buffers allocated in +DMA-able system memory, into their address space. This avoids the data +copying overhead of the read method. V4L2 supports memory mapping as +well, with a few differences. + + + + + + V4L + V4L2 + + + + + + The image format must be selected before +buffers are allocated, with the &VIDIOC-S-FMT; ioctl. When no format +is selected the driver may use the last, possibly by another +application requested format. + + + Applications cannot change the number of +buffers. The it is built into the driver, unless it has a module +option to change the number when the driver module is +loaded. + The &VIDIOC-REQBUFS; ioctl allocates the +desired number of buffers, this is a required step in the initialization +sequence. + + + Drivers map all buffers as one contiguous +range of memory. The VIDIOCGMBUF ioctl is +available to query the number of buffers, the offset of each buffer +from the start of the virtual file, and the overall amount of memory +used, which can be used as arguments for the &func-mmap; +function. + Buffers are individually mapped. The +offset and size of each buffer can be determined with the +&VIDIOC-QUERYBUF; ioctl. + + + The VIDIOCMCAPTURE +ioctl prepares a buffer for capturing. It also determines the image +format for this buffer. The ioctl returns immediately, eventually with +an &EAGAIN; if no video signal had been detected. When the driver +supports more than one buffer applications can call the ioctl multiple +times and thus have multiple outstanding capture +requests.The VIDIOCSYNC ioctl +suspends execution until a particular buffer has been +filled. + Drivers maintain an incoming and outgoing +queue. &VIDIOC-QBUF; enqueues any empty buffer into the incoming +queue. Filled buffers are dequeued from the outgoing queue with the +&VIDIOC-DQBUF; ioctl. To wait until filled buffers become available this +function, &func-select; or &func-poll; can be used. The +&VIDIOC-STREAMON; ioctl must be called once after enqueuing one or +more buffers to start capturing. Its counterpart +&VIDIOC-STREAMOFF; stops capturing and dequeues all buffers from both +queues. Applications can query the signal status, if known, with the +&VIDIOC-ENUMINPUT; ioctl. + + + + + + For a more in-depth discussion of memory mapping and +examples, see . +
+
+ +
+ Reading Raw VBI Data + + Originally the V4L API did not specify a raw VBI capture +interface, only the device file /dev/vbi was +reserved for this purpose. The only driver supporting this interface +was the BTTV driver, de-facto defining the V4L VBI interface. Reading +from the device yields a raw VBI image with the following +parameters: + + + + &v4l2-vbi-format; + V4L, BTTV driver + + + + + sampling_rate + 28636363 Hz NTSC (or any other 525-line +standard); 35468950 Hz PAL and SECAM (625-line standards) + + + offset + ? + + + samples_per_line + 2048 + + + sample_format + V4L2_PIX_FMT_GREY. The last four bytes (a +machine endianess integer) contain a frame counter. + + + start[] + 10, 273 NTSC; 22, 335 PAL and SECAM + + + count[] + 16, 16Old driver +versions used different values, eventually the custom +BTTV_VBISIZE ioctl was added to query the +correct values. + + + flags + 0 + + + + + + Undocumented in the V4L specification, in Linux 2.3 the +VIDIOCGVBIFMT and +VIDIOCSVBIFMT ioctls using struct +vbi_format were added to determine the VBI +image parameters. These ioctls are only partially compatible with the +V4L2 VBI interface specified in . + + An offset field does not +exist, sample_format is supposed to be +VIDEO_PALETTE_RAW, equivalent to +V4L2_PIX_FMT_GREY. The remaining fields are +probably equivalent to &v4l2-vbi-format;. + + Apparently only the Zoran (ZR 36120) driver implements +these ioctls. The semantics differ from those specified for V4L2 in two +ways. The parameters are reset on &func-open; and +VIDIOCSVBIFMT always returns an &EINVAL; if the +parameters are invalid. +
+ +
+ Miscellaneous + + V4L2 has no equivalent of the +VIDIOCGUNIT ioctl. Applications can find the VBI +device associated with a video capture device (or vice versa) by +reopening the device and requesting VBI data. For details see +. + + No replacement exists for VIDIOCKEY, +and the V4L functions for microcode programming. A new interface for +MPEG compression and playback devices is documented in . +
+ +
+ +
+ Changes of the V4L2 API + + Soon after the V4L API was added to the kernel it was +criticised as too inflexible. In August 1998 Bill Dirks proposed a +number of improvements and began to work on documentation, example +drivers and applications. With the help of other volunteers this +eventually became the V4L2 API, not just an extension but a +replacement for the V4L API. However it took another four years and +two stable kernel releases until the new API was finally accepted for +inclusion into the kernel in its present form. + +
+ Early Versions + 1998-08-20: First version. + + 1998-08-27: The &func-select; function was introduced. + + 1998-09-10: New video standard interface. + + 1998-09-18: The VIDIOC_NONCAP ioctl +was replaced by the otherwise meaningless O_TRUNC +&func-open; flag, and the aliases O_NONCAP and +O_NOIO were defined. Applications can set this +flag if they intend to access controls only, as opposed to capture +applications which need exclusive access. The +VIDEO_STD_XXX identifiers are now ordinals +instead of flags, and the video_std_construct() +helper function takes id and transmission arguments. + + 1998-09-28: Revamped video standard. Made video controls +individually enumerable. + + 1998-10-02: The id field was +removed from struct video_standard and the +color subcarrier fields were renamed. The &VIDIOC-QUERYSTD; ioctl was +renamed to &VIDIOC-ENUMSTD;, &VIDIOC-G-INPUT; to &VIDIOC-ENUMINPUT;. A +first draft of the Codec API was released. + + 1998-11-08: Many minor changes. Most symbols have been +renamed. Some material changes to &v4l2-capability;. + + 1998-11-12: The read/write directon of some ioctls was misdefined. + + 1998-11-14: V4L2_PIX_FMT_RGB24 +changed to V4L2_PIX_FMT_BGR24, and +V4L2_PIX_FMT_RGB32 changed to +V4L2_PIX_FMT_BGR32. Audio controls are now +accessible with the &VIDIOC-G-CTRL; and &VIDIOC-S-CTRL; ioctls under +names starting with V4L2_CID_AUDIO. The +V4L2_MAJOR define was removed from +videodev.h since it was only used once in the +videodev kernel module. The +YUV422 and YUV411 planar +image formats were added. + + 1998-11-28: A few ioctl symbols changed. Interfaces for codecs and +video output devices were added. + + 1999-01-14: A raw VBI capture interface was added. + + 1999-01-19: The VIDIOC_NEXTBUF ioctl + was removed. +
+ +
+ V4L2 Version 0.16 1999-01-31 + 1999-01-27: There is now one QBUF ioctl, VIDIOC_QWBUF and VIDIOC_QRBUF +are gone. VIDIOC_QBUF takes a v4l2_buffer as a parameter. Added +digital zoom (cropping) controls. +
+ + + +
+ V4L2 Version 0.18 1999-03-16 + Added a v4l to V4L2 ioctl compatibility layer to +videodev.c. Driver writers, this changes how you implement your ioctl +handler. See the Driver Writer's Guide. Added some more control id +codes. +
+ +
+ V4L2 Version 0.19 1999-06-05 + 1999-03-18: Fill in the category and catname fields of +v4l2_queryctrl objects before passing them to the driver. Required a +minor change to the VIDIOC_QUERYCTRL handlers in the sample +drivers. + 1999-03-31: Better compatibility for v4l memory capture +ioctls. Requires changes to drivers to fully support new compatibility +features, see Driver Writer's Guide and v4l2cap.c. Added new control +IDs: V4L2_CID_HFLIP, _VFLIP. Changed V4L2_PIX_FMT_YUV422P to _YUV422P, +and _YUV411P to _YUV411P. + 1999-04-04: Added a few more control IDs. + 1999-04-07: Added the button control type. + 1999-05-02: Fixed a typo in videodev.h, and added the +V4L2_CTRL_FLAG_GRAYED (later V4L2_CTRL_FLAG_GRABBED) flag. + 1999-05-20: Definition of VIDIOC_G_CTRL was wrong causing +a malfunction of this ioctl. + 1999-06-05: Changed the value of +V4L2_CID_WHITENESS. +
+ +
+ V4L2 Version 0.20 (1999-09-10) + + Version 0.20 introduced a number of changes which were +not backward compatible with 0.19 and earlier +versions. Purpose of these changes was to simplify the API, while +making it more extensible and following common Linux driver API +conventions. + + + + Some typos in V4L2_FMT_FLAG +symbols were fixed. &v4l2-clip; was changed for compatibility with +v4l. (1999-08-30) + + + + V4L2_TUNER_SUB_LANG1 was added. +(1999-09-05) + + + + All ioctl() commands that used an integer argument now +take a pointer to an integer. Where it makes sense, ioctls will return +the actual new value in the integer pointed to by the argument, a +common convention in the V4L2 API. The affected ioctls are: +VIDIOC_PREVIEW, VIDIOC_STREAMON, VIDIOC_STREAMOFF, VIDIOC_S_FREQ, +VIDIOC_S_INPUT, VIDIOC_S_OUTPUT, VIDIOC_S_EFFECT. For example + +err = ioctl (fd, VIDIOC_XXX, V4L2_XXX); + becomes +int a = V4L2_XXX; err = ioctl(fd, VIDIOC_XXX, &a); + + + + + + All the different get- and set-format commands were +swept into one &VIDIOC-G-FMT; and &VIDIOC-S-FMT; ioctl taking a union +and a type field selecting the union member as parameter. Purpose is to +simplify the API by eliminating several ioctls and to allow new and +driver private data streams without adding new ioctls. + + This change obsoletes the following ioctls: +VIDIOC_S_INFMT, +VIDIOC_G_INFMT, +VIDIOC_S_OUTFMT, +VIDIOC_G_OUTFMT, +VIDIOC_S_VBIFMT and +VIDIOC_G_VBIFMT. The image format structure +v4l2_format was renamed to &v4l2-pix-format;, +while &v4l2-format; is now the envelopping structure for all format +negotiations. + + + + Similar to the changes above, the +VIDIOC_G_PARM and +VIDIOC_S_PARM ioctls were merged with +VIDIOC_G_OUTPARM and +VIDIOC_S_OUTPARM. A +type field in the new &v4l2-streamparm; +selects the respective union member. + + This change obsoletes the +VIDIOC_G_OUTPARM and +VIDIOC_S_OUTPARM ioctls. + + + + Control enumeration was simplified, and two new +control flags were introduced and one dropped. The +catname field was replaced by a +group field. + + Drivers can now flag unsupported and temporarily +unavailable controls with V4L2_CTRL_FLAG_DISABLED +and V4L2_CTRL_FLAG_GRABBED respectively. The +group name indicates a possibly narrower +classification than the category. In other +words, there may be multiple groups within a category. Controls within +a group would typically be drawn within a group box. Controls in +different categories might have a greater separation, or may even +appear in separate windows. + + + + The &v4l2-buffer; timestamp +was changed to a 64 bit integer, containing the sampling or output +time of the frame in nanoseconds. Additionally timestamps will be in +absolute system time, not starting from zero at the beginning of a +stream. The data type name for timestamps is stamp_t, defined as a +signed 64-bit integer. Output devices should not send a buffer out +until the time in the timestamp field has arrived. I would like to +follow SGI's lead, and adopt a multimedia timestamping system like +their UST (Unadjusted System Time). See +http://reality.sgi.com/cpirazzi_engr/lg/time/intro.html. [This link is +no longer valid.] UST uses timestamps that are 64-bit signed integers +(not struct timeval's) and given in nanosecond units. The UST clock +starts at zero when the system is booted and runs continuously and +uniformly. It takes a little over 292 years for UST to overflow. There +is no way to set the UST clock. The regular Linux time-of-day clock +can be changed periodically, which would cause errors if it were being +used for timestamping a multimedia stream. A real UST style clock will +require some support in the kernel that is not there yet. But in +anticipation, I will change the timestamp field to a 64-bit integer, +and I will change the v4l2_masterclock_gettime() function (used only +by drivers) to return a 64-bit integer. + + + + A sequence field was added +to &v4l2-buffer;. The sequence field counts +captured frames, it is ignored by output devices. When a capture +driver drops a frame, the sequence number of that frame is +skipped. + + +
+ +
+ V4L2 Version 0.20 incremental changes + + + 1999-12-23: In &v4l2-vbi-format; the +reserved1 field became +offset. Previously drivers were required to +clear the reserved1 field. + + 2000-01-13: The + V4L2_FMT_FLAG_NOT_INTERLACED flag was added. + + 2000-07-31: The linux/poll.h header +is now included by videodev.h for compatibility +with the original videodev.h file. + + 2000-11-20: V4L2_TYPE_VBI_OUTPUT and +V4L2_PIX_FMT_Y41P were added. + + 2000-11-25: V4L2_TYPE_VBI_INPUT was +added. + + 2000-12-04: A couple typos in symbol names were fixed. + + 2001-01-18: To avoid namespace conflicts the +fourcc macro defined in the +videodev.h header file was renamed to +v4l2_fourcc. + + 2001-01-25: A possible driver-level compatibility problem +between the videodev.h file in Linux 2.4.0 and +the videodev.h file included in the +videodevX patch was fixed. Users of an earlier +version of videodevX on Linux 2.4.0 should +recompile their V4L and V4L2 drivers. + + 2001-01-26: A possible kernel-level incompatibility +between the videodev.h file in the +videodevX patch and the +videodev.h file in Linux 2.2.x with devfs patches +applied was fixed. + + 2001-03-02: Certain V4L ioctls which pass data in both +direction although they are defined with read-only parameter, did not +work correctly through the backward compatibility layer. +[Solution?] + + 2001-04-13: Big endian 16-bit RGB formats were added. + + 2001-09-17: New YUV formats and the &VIDIOC-G-FREQUENCY; and +&VIDIOC-S-FREQUENCY; ioctls were added. (The old +VIDIOC_G_FREQ and +VIDIOC_S_FREQ ioctls did not take multiple tuners +into account.) + + 2000-09-18: V4L2_BUF_TYPE_VBI was +added. This may break compatibility as the +&VIDIOC-G-FMT; and &VIDIOC-S-FMT; ioctls may fail now if the struct +v4l2_fmt type +field does not contain V4L2_BUF_TYPE_VBI. In the +documentation of the &v4l2-vbi-format; +offset field the ambiguous phrase "rising +edge" was changed to "leading edge". +
+ +
+ V4L2 Version 0.20 2000-11-23 + + A number of changes were made to the raw VBI +interface. + + + + Figures clarifying the line numbering scheme were +added to the V4L2 API specification. The +start[0] and +start[1] fields no longer count line +numbers beginning at zero. Rationale: a) The previous definition was +unclear. b) The start[] values are ordinal +numbers. c) There is no point in inventing a new line numbering +scheme. We now use line number as defined by ITU-R, period. +Compatibility: Add one to the start values. Applications depending on +the previous semantics may not function correctly. + + + + The restriction "count[0] > 0 and count[1] > 0" +has been relaxed to "(count[0] + count[1]) > 0". Rationale: +Drivers may allocate resources at scan line granularity and some data +services are transmitted only on the first field. The comment that +both count values will usually be equal is +misleading and pointless and has been removed. This change +breaks compatibility with earlier versions: +Drivers may return EINVAL, applications may not function +correctly. + + + + Drivers are again permitted to return negative +(unknown) start values as proposed earlier. Why this feature was +dropped is unclear. This change may break +compatibility with applications depending on the start +values being positive. The use of EBUSY and +EINVAL error codes with the &VIDIOC-S-FMT; ioctl +was clarified. The &EBUSY; was finally documented, and the +reserved2 field which was previously +mentioned only in the videodev.h header +file. + + + + New buffer types +V4L2_TYPE_VBI_INPUT and +V4L2_TYPE_VBI_OUTPUT were added. The former is an +alias for the old V4L2_TYPE_VBI, the latter was +missing in the videodev.h file. + + +
+ +
+ V4L2 Version 0.20 2002-07-25 + Added sliced VBI interface proposal. +
+ +
+ V4L2 in Linux 2.5.46, 2002-10 + + Around October-November 2002, prior to an announced +feature freeze of Linux 2.5, the API was revised, drawing from +experience with V4L2 0.20. This unnamed version was finally merged +into Linux 2.5.46. + + + + As specified in , drivers +must make related device functions available under all minor device +numbers. + + + + The &func-open; function requires access mode +O_RDWR regardless of the device type. All V4L2 +drivers exchanging data with applications must support the +O_NONBLOCK flag. The O_NOIO +flag, a V4L2 symbol which aliased the meaningless +O_TRUNC to indicate accesses without data +exchange (panel applications) was dropped. Drivers must stay in "panel +mode" until the application attempts to initiate a data exchange, see +. + + + + The &v4l2-capability; changed dramatically. Note that +also the size of the structure changed, which is encoded in the ioctl +request code, thus older V4L2 devices will respond with an &EINVAL; to +the new &VIDIOC-QUERYCAP; ioctl. + + There are new fields to identify the driver, a new (as +of yet unspecified) device function +V4L2_CAP_RDS_CAPTURE, the +V4L2_CAP_AUDIO flag indicates if the device has +any audio connectors, another I/O capability +V4L2_CAP_ASYNCIO can be flagged. In response to +these changes the type field became a bit +set and was merged into the flags field. +V4L2_FLAG_TUNER was renamed to +V4L2_CAP_TUNER, +V4L2_CAP_VIDEO_OVERLAY replaced +V4L2_FLAG_PREVIEW and +V4L2_CAP_VBI_CAPTURE and +V4L2_CAP_VBI_OUTPUT replaced +V4L2_FLAG_DATA_SERVICE. +V4L2_FLAG_READ and +V4L2_FLAG_WRITE were merged into +V4L2_CAP_READWRITE. + + The redundant fields +inputs, outputs +and audios were removed. These properties +can be determined as described in and . + + The somewhat volatile and therefore barely useful +fields maxwidth, +maxheight, +minwidth, +minheight, +maxframerate were removed. This information +is available as described in and +. + + V4L2_FLAG_SELECT was removed. We +believe the select() function is important enough to require support +of it in all V4L2 drivers exchanging data with applications. The +redundant V4L2_FLAG_MONOCHROME flag was removed, +this information is available as described in . + + + + In &v4l2-input; the +assoc_audio field and the +capability field and its only flag +V4L2_INPUT_CAP_AUDIO was replaced by the new +audioset field. Instead of linking one +video input to one audio input this field reports all audio inputs +this video input combines with. + + New fields are tuner +(reversing the former link from tuners to video inputs), +std and +status. + + Accordingly &v4l2-output; lost its +capability and +assoc_audio fields. +audioset, +modulator and +std where added instead. + + + + The &v4l2-audio; field +audio was renamed to +index, for consistency with other +structures. A new capability flag +V4L2_AUDCAP_STEREO was added to indicated if the +audio input in question supports stereo sound. +V4L2_AUDCAP_EFFECTS and the corresponding +V4L2_AUDMODE flags where removed. This can be +easily implemented using controls. (However the same applies to AVL +which is still there.) + + Again for consistency the &v4l2-audioout; field +audio was renamed to +index. + + + + The &v4l2-tuner; +input field was replaced by an +index field, permitting devices with +multiple tuners. The link between video inputs and tuners is now +reversed, inputs point to their tuner. The +std substructure became a +simple set (more about this below) and moved into &v4l2-input;. A +type field was added. + + Accordingly in &v4l2-modulator; the +output was replaced by an +index field. + + In &v4l2-frequency; the +port field was replaced by a +tuner field containing the respective tuner +or modulator index number. A tuner type +field was added and the reserved field +became larger for future extensions (satellite tuners in +particular). + + + + The idea of completely transparent video standards was +dropped. Experience showed that applications must be able to work with +video standards beyond presenting the user a menu. Instead of +enumerating supported standards with an ioctl applications can now +refer to standards by &v4l2-std-id; and symbols defined in the +videodev2.h header file. For details see . The &VIDIOC-G-STD; and +&VIDIOC-S-STD; now take a pointer to this type as argument. +&VIDIOC-QUERYSTD; was added to autodetect the received standard, if +the hardware has this capability. In &v4l2-standard; an +index field was added for &VIDIOC-ENUMSTD;. +A &v4l2-std-id; field named id was added as +machine readable identifier, also replacing the +transmission field. The misleading +framerate field was renamed +to frameperiod. The now obsolete +colorstandard information, originally +needed to distguish between variations of standards, were +removed. + + Struct v4l2_enumstd ceased to +be. &VIDIOC-ENUMSTD; now takes a pointer to a &v4l2-standard; +directly. The information which standards are supported by a +particular video input or output moved into &v4l2-input; and +&v4l2-output; fields named std, +respectively. + + + + The &v4l2-queryctrl; fields +category and +group did not catch on and/or were not +implemented as expected and therefore removed. + + + + The &VIDIOC-TRY-FMT; ioctl was added to negotiate data +formats as with &VIDIOC-S-FMT;, but without the overhead of +programming the hardware and regardless of I/O in progress. + + In &v4l2-format; the fmt +union was extended to contain &v4l2-window;. All image format +negotiations are now possible with VIDIOC_G_FMT, +VIDIOC_S_FMT and +VIDIOC_TRY_FMT; ioctl. The +VIDIOC_G_WIN and +VIDIOC_S_WIN ioctls to prepare for a video +overlay were removed. The type field +changed to type &v4l2-buf-type; and the buffer type names changed as +follows. + + + + Old defines + &v4l2-buf-type; + + + + + V4L2_BUF_TYPE_CAPTURE + V4L2_BUF_TYPE_VIDEO_CAPTURE + + + V4L2_BUF_TYPE_CODECIN + Omitted for now + + + V4L2_BUF_TYPE_CODECOUT + Omitted for now + + + V4L2_BUF_TYPE_EFFECTSIN + Omitted for now + + + V4L2_BUF_TYPE_EFFECTSIN2 + Omitted for now + + + V4L2_BUF_TYPE_EFFECTSOUT + Omitted for now + + + V4L2_BUF_TYPE_VIDEOOUT + V4L2_BUF_TYPE_VIDEO_OUTPUT + + + - + V4L2_BUF_TYPE_VIDEO_OVERLAY + + + - + V4L2_BUF_TYPE_VBI_CAPTURE + + + - + V4L2_BUF_TYPE_VBI_OUTPUT + + + - + V4L2_BUF_TYPE_SLICED_VBI_CAPTURE + + + - + V4L2_BUF_TYPE_SLICED_VBI_OUTPUT + + + V4L2_BUF_TYPE_PRIVATE_BASE + V4L2_BUF_TYPE_PRIVATE + + + + + + + + In &v4l2-fmtdesc; a &v4l2-buf-type; field named +type was added as in &v4l2-format;. The +VIDIOC_ENUM_FBUFFMT ioctl is no longer needed and +was removed. These calls can be replaced by &VIDIOC-ENUM-FMT; with +type V4L2_BUF_TYPE_VIDEO_OVERLAY. + + + + In &v4l2-pix-format; the +depth field was removed, assuming +applications which recognize the format by its four-character-code +already know the color depth, and others do not care about it. The +same rationale lead to the removal of the +V4L2_FMT_FLAG_COMPRESSED flag. The +V4L2_FMT_FLAG_SWCONVECOMPRESSED flag was removed +because drivers are not supposed to convert images in kernel space. A +user library of conversion functions should be provided instead. The +V4L2_FMT_FLAG_BYTESPERLINE flag was redundant. +Applications can set the bytesperline field +to zero to get a reasonable default. Since the remaining flags were +replaced as well, the flags field itself +was removed. + The interlace flags were replaced by a &v4l2-field; +value in a newly added field +field. + + + + Old flag + &v4l2-field; + + + + + V4L2_FMT_FLAG_NOT_INTERLACED + ? + + + V4L2_FMT_FLAG_INTERLACED += V4L2_FMT_FLAG_COMBINED + V4L2_FIELD_INTERLACED + + + V4L2_FMT_FLAG_TOPFIELD += V4L2_FMT_FLAG_ODDFIELD + V4L2_FIELD_TOP + + + V4L2_FMT_FLAG_BOTFIELD += V4L2_FMT_FLAG_EVENFIELD + V4L2_FIELD_BOTTOM + + + - + V4L2_FIELD_SEQ_TB + + + - + V4L2_FIELD_SEQ_BT + + + - + V4L2_FIELD_ALTERNATE + + + + + + The color space flags were replaced by a +&v4l2-colorspace; value in a newly added +colorspace field, where one of +V4L2_COLORSPACE_SMPTE170M, +V4L2_COLORSPACE_BT878, +V4L2_COLORSPACE_470_SYSTEM_M or +V4L2_COLORSPACE_470_SYSTEM_BG replaces +V4L2_FMT_CS_601YUV. + + + + In &v4l2-requestbuffers; the +type field was properly defined as +&v4l2-buf-type;. Buffer types changed as mentioned above. A new +memory field of type &v4l2-memory; was +added to distinguish between I/O methods using buffers allocated +by the driver or the application. See for +details. + + + + In &v4l2-buffer; the type +field was properly defined as &v4l2-buf-type;. Buffer types changed as +mentioned above. A field field of type +&v4l2-field; was added to indicate if a buffer contains a top or +bottom field. The old field flags were removed. Since no unadjusted +system time clock was added to the kernel as planned, the +timestamp field changed back from type +stamp_t, an unsigned 64 bit integer expressing the sample time in +nanoseconds, to struct timeval. With the +addition of a second memory mapping method the +offset field moved into union +m, and a new +memory field of type &v4l2-memory; was +added to distinguish between I/O methods. See +for details. + + The V4L2_BUF_REQ_CONTIG +flag was used by the V4L compatibility layer, after changes to this +code it was no longer needed. The +V4L2_BUF_ATTR_DEVICEMEM flag would indicate if +the buffer was indeed allocated in device memory rather than DMA-able +system memory. It was barely useful and so was removed. + + + + In &v4l2-framebuffer; the +base[3] array anticipating double- and +triple-buffering in off-screen video memory, however without defining +a synchronization mechanism, was replaced by a single pointer. The +V4L2_FBUF_CAP_SCALEUP and +V4L2_FBUF_CAP_SCALEDOWN flags were removed. +Applications can determine this capability more accurately using the +new cropping and scaling interface. The +V4L2_FBUF_CAP_CLIPPING flag was replaced by +V4L2_FBUF_CAP_LIST_CLIPPING and +V4L2_FBUF_CAP_BITMAP_CLIPPING. + + + + In &v4l2-clip; the x, +y, width and +height field moved into a +c substructure of type &v4l2-rect;. The +x and y fields +were renamed to left and +top, &ie; offsets to a context dependent +origin. + + + + In &v4l2-window; the x, +y, width and +height field moved into a +w substructure as above. A +field field of type %v4l2-field; was added +to distinguish between field and frame (interlaced) overlay. + + + + The digital zoom interface, including struct +v4l2_zoomcap, struct +v4l2_zoom, +V4L2_ZOOM_NONCAP and +V4L2_ZOOM_WHILESTREAMING was replaced by a new +cropping and scaling interface. The previously unused struct +v4l2_cropcap and +v4l2_crop where redefined for this purpose. +See for details. + + + + In &v4l2-vbi-format; the +SAMPLE_FORMAT field now contains a +four-character-code as used to identify video image formats and +V4L2_PIX_FMT_GREY replaces the +V4L2_VBI_SF_UBYTE define. The +reserved field was extended. + + + + In &v4l2-captureparm; the type of the +timeperframe field changed from unsigned +long to &v4l2-fract;. This allows the accurate expression of multiples +of the NTSC-M frame rate 30000 / 1001. A new field +readbuffers was added to control the driver +behaviour in read I/O mode. + + Similar changes were made to &v4l2-outputparm;. + + + + The struct v4l2_performance +and VIDIOC_G_PERF ioctl were dropped. Except when +using the read/write I/O method, which is +limited anyway, this information is already available to +applications. + + + + The example transformation from RGB to YCbCr color +space in the old V4L2 documentation was inaccurate, this has been +corrected in . + + +
+ +
+ V4L2 2003-06-19 + + + + A new capability flag +V4L2_CAP_RADIO was added for radio devices. Prior +to this change radio devices would identify solely by having exactly one +tuner whose type field reads V4L2_TUNER_RADIO. + + + + An optional driver access priority mechanism was +added, see for details. + + + + The audio input and output interface was found to be +incomplete. + Previously the &VIDIOC-G-AUDIO; +ioctl would enumerate the available audio inputs. An ioctl to +determine the current audio input, if more than one combines with the +current video input, did not exist. So +VIDIOC_G_AUDIO was renamed to +VIDIOC_G_AUDIO_OLD, this ioctl will be removed in +the future. The &VIDIOC-ENUMAUDIO; ioctl was added to enumerate +audio inputs, while &VIDIOC-G-AUDIO; now reports the current audio +input. + The same changes were made to &VIDIOC-G-AUDOUT; and +&VIDIOC-ENUMAUDOUT;. + Until further the "videodev" module will automatically +translate between the old and new ioctls, but drivers and applications +must be updated to successfully compile again. + + + + The &VIDIOC-OVERLAY; ioctl was incorrectly defined with +write-read parameter. It was changed to write-only, while the write-read +version was renamed to VIDIOC_OVERLAY_OLD. The old +ioctl will be removed in the future. Until further the "videodev" +kernel module will automatically translate to the new version, so drivers +must be recompiled, but not applications. + + + + incorrectly stated that +clipping rectangles define regions where the video can be seen. +Correct is that clipping rectangles define regions where +no video shall be displayed and so the graphics +surface can be seen. + + + + The &VIDIOC-S-PARM; and &VIDIOC-S-CTRL; ioctls were +defined with write-only parameter, inconsistent with other ioctls +modifying their argument. They were changed to write-read, while a +_OLD suffix was added to the write-only versions. +The old ioctls will be removed in the future. Drivers and +applications assuming a constant parameter need an update. + + +
+ +
+ V4L2 2003-11-05 + + + In the following pixel +formats were incorrectly transferred from Bill Dirks' V4L2 +specification. Descriptions below refer to bytes in memory, in +ascending address order. + + + + Symbol + In this document prior to revision +0.5 + Corrected + + + + + V4L2_PIX_FMT_RGB24 + B, G, R + R, G, B + + + V4L2_PIX_FMT_BGR24 + R, G, B + B, G, R + + + V4L2_PIX_FMT_RGB32 + B, G, R, X + R, G, B, X + + + V4L2_PIX_FMT_BGR32 + R, G, B, X + B, G, R, X + + + + The +V4L2_PIX_FMT_BGR24 example was always +correct. + In the mapping +of the V4L VIDEO_PALETTE_RGB24 and +VIDEO_PALETTE_RGB32 formats to V4L2 pixel formats +was accordingly corrected. + + + + Unrelated to the fixes above, drivers may still +interpret some V4L2 RGB pixel formats differently. These issues have +yet to be addressed, for details see . + + +
+ +
+ V4L2 in Linux 2.6.6, 2004-05-09 + + + The &VIDIOC-CROPCAP; ioctl was incorrectly defined +with read-only parameter. It is now defined as write-read ioctl, while +the read-only version was renamed to +VIDIOC_CROPCAP_OLD. The old ioctl will be removed +in the future. + + +
+ +
+ V4L2 in Linux 2.6.8 + + + A new field input (former +reserved[0]) was added to the &v4l2-buffer; +structure. Purpose of this field is to alternate between video inputs +(⪚ cameras) in step with the video capturing process. This function +must be enabled with the new V4L2_BUF_FLAG_INPUT +flag. The flags field is no longer +read-only. + + +
+ +
+ V4L2 spec erratum 2004-08-01 + + + + The return value of the + function was incorrectly documented. + + + + Audio output ioctls end in -AUDOUT, not -AUDIOOUT. + + + + In the Current Audio Input example the +VIDIOC_G_AUDIO ioctl took the wrong +argument. + + + + The documentation of the &VIDIOC-QBUF; and +&VIDIOC-DQBUF; ioctls did not mention the &v4l2-buffer; +memory field. It was also missing from +examples. Also on the VIDIOC_DQBUF page the &EIO; +was not documented. + + +
+ +
+ V4L2 in Linux 2.6.14 + + + A new sliced VBI interface was added. It is documented +in and replaces the interface first +proposed in V4L2 specification 0.8. + + +
+ +
+ V4L2 in Linux 2.6.15 + + + The &VIDIOC-LOG-STATUS; ioctl was added. + + + + New video standards +V4L2_STD_NTSC_443, +V4L2_STD_SECAM_LC, +V4L2_STD_SECAM_DK (a set of SECAM D, K and K1), +and V4L2_STD_ATSC (a set of +V4L2_STD_ATSC_8_VSB and +V4L2_STD_ATSC_16_VSB) were defined. Note the +V4L2_STD_525_60 set now includes +V4L2_STD_NTSC_443. See also . + + + + The VIDIOC_G_COMP and +VIDIOC_S_COMP ioctl were renamed to +VIDIOC_G_MPEGCOMP and +VIDIOC_S_MPEGCOMP respectively. Their argument +was replaced by a struct +v4l2_mpeg_compression pointer. (The +VIDIOC_G_MPEGCOMP and +VIDIOC_S_MPEGCOMP ioctls where removed in Linux +2.6.25.) + + +
+ +
+ V4L2 spec erratum 2005-11-27 + The capture example in +called the &VIDIOC-S-CROP; ioctl without checking if cropping is +supported. In the video standard selection example in + the &VIDIOC-S-STD; call used the wrong +argument type. +
+ +
+ V4L2 spec erratum 2006-01-10 + + + The V4L2_IN_ST_COLOR_KILL flag in +&v4l2-input; not only indicates if the color killer is enabled, but +also if it is active. (The color killer disables color decoding when +it detects no color in the video signal to improve the image +quality.) + + + + &VIDIOC-S-PARM; is a write-read ioctl, not write-only as +stated on its reference page. The ioctl changed in 2003 as noted above. + + +
+ +
+ V4L2 spec erratum 2006-02-03 + + + In &v4l2-captureparm; and &v4l2-outputparm; the +timeperframe field gives the time in +seconds, not microseconds. + + +
+ +
+ V4L2 spec erratum 2006-02-04 + + + The clips field in +&v4l2-window; must point to an array of &v4l2-clip;, not a linked +list, because drivers ignore the struct +v4l2_clip.next +pointer. + + +
+ +
+ V4L2 in Linux 2.6.17 + + + New video standard macros were added: +V4L2_STD_NTSC_M_KR (NTSC M South Korea), and the +sets V4L2_STD_MN, +V4L2_STD_B, V4L2_STD_GH and +V4L2_STD_DK. The +V4L2_STD_NTSC and +V4L2_STD_SECAM sets now include +V4L2_STD_NTSC_M_KR and +V4L2_STD_SECAM_LC respectively. + + + + A new V4L2_TUNER_MODE_LANG1_LANG2 +was defined to record both languages of a bilingual program. The +use of V4L2_TUNER_MODE_STEREO for this purpose +is deprecated now. See the &VIDIOC-G-TUNER; section for +details. + + +
+ +
+ V4L2 spec erratum 2006-09-23 (Draft 0.15) + + + In various places +V4L2_BUF_TYPE_SLICED_VBI_CAPTURE and +V4L2_BUF_TYPE_SLICED_VBI_OUTPUT of the sliced VBI +interface were not mentioned along with other buffer types. + + + + In it was clarified +that the &v4l2-audio; mode field is a flags +field. + + + + did not mention the +sliced VBI and radio capability flags. + + + + In it was +clarified that applications must initialize the tuner +type field of &v4l2-frequency; before +calling &VIDIOC-S-FREQUENCY;. + + + + The reserved array +in &v4l2-requestbuffers; has 2 elements, not 32. + + + + In and the device file names +/dev/vout which never caught on were replaced +by /dev/video. + + + + With Linux 2.6.15 the possible range for VBI device minor +numbers was extended from 224-239 to 224-255. Accordingly device file names +/dev/vbi0 to /dev/vbi31 are +possible now. + + +
+ +
+ V4L2 in Linux 2.6.18 + + + New ioctls &VIDIOC-G-EXT-CTRLS;, &VIDIOC-S-EXT-CTRLS; +and &VIDIOC-TRY-EXT-CTRLS; were added, a flag to skip unsupported +controls with &VIDIOC-QUERYCTRL;, new control types +V4L2_CTRL_TYPE_INTEGER64 and +V4L2_CTRL_TYPE_CTRL_CLASS (), and new control flags +V4L2_CTRL_FLAG_READ_ONLY, +V4L2_CTRL_FLAG_UPDATE, +V4L2_CTRL_FLAG_INACTIVE and +V4L2_CTRL_FLAG_SLIDER (). See for details. + + +
+ +
+ V4L2 in Linux 2.6.19 + + + In &v4l2-sliced-vbi-cap; a buffer type field was added +replacing a reserved field. Note on architectures where the size of +enum types differs from int types the size of the structure changed. +The &VIDIOC-G-SLICED-VBI-CAP; ioctl was redefined from being read-only +to write-read. Applications must initialize the type field and clear +the reserved fields now. These changes may break the +compatibility with older drivers and applications. + + + + The ioctls &VIDIOC-ENUM-FRAMESIZES; and +&VIDIOC-ENUM-FRAMEINTERVALS; were added. + + + + A new pixel format V4L2_PIX_FMT_RGB444 () was added. + + +
+ +
+ V4L2 spec erratum 2006-10-12 (Draft 0.17) + + + V4L2_PIX_FMT_HM12 () is a YUV 4:2:0, not 4:2:2 format. + + +
+ +
+ V4L2 in Linux 2.6.21 + + + The videodev2.h header file is +now dual licensed under GNU General Public License version two or +later, and under a 3-clause BSD-style license. + + +
+ +
+ V4L2 in Linux 2.6.22 + + + Two new field orders + V4L2_FIELD_INTERLACED_TB and + V4L2_FIELD_INTERLACED_BT were + added. See for details. + + + + Three new clipping/blending methods with a global or +straight or inverted local alpha value were added to the video overlay +interface. See the description of the &VIDIOC-G-FBUF; and +&VIDIOC-S-FBUF; ioctls for details. + A new global_alpha field +was added to v4l2_window, +extending the structure. This may break +compatibility with applications using a struct +v4l2_window directly. However the VIDIOC_G/S/TRY_FMT ioctls, which take a +pointer to a v4l2_format parent +structure with padding bytes at the end, are not affected. + + + + The format of the chromakey +field in &v4l2-window; changed from "host order RGB32" to a pixel +value in the same format as the framebuffer. This may break +compatibility with existing applications. Drivers +supporting the "host order RGB32" format are not known. + + + +
+ +
+ V4L2 in Linux 2.6.24 + + + The pixel formats +V4L2_PIX_FMT_PAL8, +V4L2_PIX_FMT_YUV444, +V4L2_PIX_FMT_YUV555, +V4L2_PIX_FMT_YUV565 and +V4L2_PIX_FMT_YUV32 were added. + + +
+ +
+ V4L2 in Linux 2.6.25 + + + The pixel formats +V4L2_PIX_FMT_Y16 and +V4L2_PIX_FMT_SBGGR16 were added. + + + New controls +V4L2_CID_POWER_LINE_FREQUENCY, +V4L2_CID_HUE_AUTO, +V4L2_CID_WHITE_BALANCE_TEMPERATURE, +V4L2_CID_SHARPNESS and +V4L2_CID_BACKLIGHT_COMPENSATION were added. The +controls V4L2_CID_BLACK_LEVEL, +V4L2_CID_WHITENESS, +V4L2_CID_HCENTER and +V4L2_CID_VCENTER were deprecated. + + + + A Camera controls +class was added, with the new controls +V4L2_CID_EXPOSURE_AUTO, +V4L2_CID_EXPOSURE_ABSOLUTE, +V4L2_CID_EXPOSURE_AUTO_PRIORITY, +V4L2_CID_PAN_RELATIVE, +V4L2_CID_TILT_RELATIVE, +V4L2_CID_PAN_RESET, +V4L2_CID_TILT_RESET, +V4L2_CID_PAN_ABSOLUTE, +V4L2_CID_TILT_ABSOLUTE, +V4L2_CID_FOCUS_ABSOLUTE, +V4L2_CID_FOCUS_RELATIVE and +V4L2_CID_FOCUS_AUTO. + + + The VIDIOC_G_MPEGCOMP and +VIDIOC_S_MPEGCOMP ioctls, which were superseded +by the extended controls +interface in Linux 2.6.18, where finally removed from the +videodev2.h header file. + + +
+
+ +
+ Relation of V4L2 to other Linux multimedia APIs + +
+ X Video Extension + + The X Video Extension (abbreviated XVideo or just Xv) is +an extension of the X Window system, implemented for example by the +XFree86 project. Its scope is similar to V4L2, an API to video capture +and output devices for X clients. Xv allows applications to display +live video in a window, send window contents to a TV output, and +capture or output still images in XPixmaps + This is not implemented in XFree86. + . With their implementation XFree86 makes the +extension available across many operating systems and +architectures. + + Because the driver is embedded into the X server Xv has a +number of advantages over the V4L2 video +overlay interface. The driver can easily determine the overlay +target, &ie; visible graphics memory or off-screen buffers for a +destructive overlay. It can program the RAMDAC for a non-destructive +overlay, scaling or color-keying, or the clipping functions of the +video capture hardware, always in sync with drawing operations or +windows moving or changing their stacking order. + + To combine the advantages of Xv and V4L a special Xv +driver exists in XFree86 and XOrg, just programming any overlay capable +Video4Linux device it finds. To enable it +/etc/X11/XF86Config must contain these lines: + +Section "Module" + Load "v4l" +EndSection + + As of XFree86 4.2 this driver still supports only V4L +ioctls, however it should work just fine with all V4L2 devices through +the V4L2 backward-compatibility layer. Since V4L2 permits multiple +opens it is possible (if supported by the V4L2 driver) to capture +video while an X client requested video overlay. Restrictions of +simultaneous capturing and overlay are discussed in apply. + + Only marginally related to V4L2, XFree86 extended Xv to +support hardware YUV to RGB conversion and scaling for faster video +playback, and added an interface to MPEG-2 decoding hardware. This API +is useful to display images captured with V4L2 devices. +
+ +
+ Digital Video + + V4L2 does not support digital terrestrial, cable or +satellite broadcast. A separate project aiming at digital receivers +exists. You can find its homepage at http://linuxtv.org. The Linux DVB API +has no connection to the V4L2 API except that drivers for hybrid +hardware may support both. +
+ +
+ Audio Interfaces + + [to do - OSS/ALSA] +
+
+ +
+ Experimental API Elements + + The following V4L2 API elements are currently experimental +and may change in the future. + + + + Video Output Overlay (OSD) Interface, . + + + V4L2_BUF_TYPE_VIDEO_OUTPUT_OVERLAY, + &v4l2-buf-type;, . + + + V4L2_CAP_VIDEO_OUTPUT_OVERLAY, +&VIDIOC-QUERYCAP; ioctl, . + + + &VIDIOC-ENUM-FRAMESIZES; and +&VIDIOC-ENUM-FRAMEINTERVALS; ioctls. + + + &VIDIOC-G-ENC-INDEX; ioctl. + + + &VIDIOC-ENCODER-CMD; and &VIDIOC-TRY-ENCODER-CMD; +ioctls. + + + &VIDIOC-DBG-G-REGISTER; and &VIDIOC-DBG-S-REGISTER; +ioctls. + + + &VIDIOC-G-CHIP-IDENT; ioctl. + + +
+ +
+ Obsolete API Elements + + The following V4L2 API elements were superseded by new +interfaces and should not be implemented in new drivers. + + + + VIDIOC_G_MPEGCOMP and +VIDIOC_S_MPEGCOMP ioctls. Use Extended Controls, +. + + +
+ + diff --git a/v4l2-spec/controls.sgml b/v4l2-spec/controls.sgml new file mode 100644 index 000000000..d643bbec8 --- /dev/null +++ b/v4l2-spec/controls.sgml @@ -0,0 +1,1660 @@ +
+ User Controls + + Devices typically have a number of user-settable controls +such as brightness, saturation and so on, which would be presented to +the user on a graphical user interface. But, different devices +will have different controls available, and furthermore, the range of +possible values, and the default value will vary from device to +device. The control ioctls provide the information and a mechanism to +create a nice user interface for these controls that will work +correctly with any device. + + All controls are accessed using an ID value. V4L2 defines +several IDs for specific purposes. Drivers can also implement their +own custom controls using V4L2_CID_PRIVATE_BASE +and higher values. The pre-defined control IDs have the prefix +V4L2_CID_, and are listed in . The ID is used when querying the attributes of +a control, and when getting or setting the current value. + + Generally applications should present controls to the user +without assumptions about their purpose. Each control comes with a +name string the user is supposed to understand. When the purpose is +non-intuitive the driver writer should provide a user manual, a user +interface plug-in or a driver specific panel application. Predefined +IDs were introduced to change a few controls programmatically, for +example to mute a device during a channel switch. + + Drivers may enumerate different controls after switching +the current video input or output, tuner or modulator, or audio input +or output. Different in the sense of other bounds, another default and +current value, step size or other menu items. A control with a certain +custom ID can also change name and +type. + It will be more convenient for applications if drivers +make use of the V4L2_CTRL_FLAG_DISABLED flag, but +that was never required. + Control values are stored globally, they do not +change when switching except to stay within the reported bounds. They +also do not change ⪚ when the device is opened or closed, when the +tuner radio frequency is changed or generally never without +application request. Since V4L2 specifies no event mechanism, panel +applications intended to cooperate with other panel applications (be +they built into a larger application, as a TV viewer) may need to +regularly poll control values to update their user +interface. + Applications could call an ioctl to request events. +After another process called &VIDIOC-S-CTRL; or another ioctl changing +shared properties the &func-select; function would indicate +readability until any ioctl (querying the properties) is +called. + + + + Control IDs + + &cs-def; + + + ID + Type + Description + + + + + V4L2_CID_BASE + + First predefined ID, equal to +V4L2_CID_BRIGHTNESS. + + + V4L2_CID_USER_BASE + + Synonym of V4L2_CID_BASE. + + + V4L2_CID_BRIGHTNESS + integer + Picture brightness, or more precisely, the black +level. + + + V4L2_CID_CONTRAST + integer + Picture contrast or luma gain. + + + V4L2_CID_SATURATION + integer + Picture color saturation or chroma gain. + + + V4L2_CID_HUE + integer + Hue or color balance. + + + V4L2_CID_AUDIO_VOLUME + integer + Overall audio volume. Note some drivers also +provide an OSS or ALSA mixer interface. + + + V4L2_CID_AUDIO_BALANCE + integer + Audio stereo balance. Minimum corresponds to all +the way left, maximum to right. + + + V4L2_CID_AUDIO_BASS + integer + Audio bass adjustment. + + + V4L2_CID_AUDIO_TREBLE + integer + Audio treble adjustment. + + + V4L2_CID_AUDIO_MUTE + boolean + Mute audio, &ie; set the volume to zero, however +without affecting V4L2_CID_AUDIO_VOLUME. Like +ALSA drivers, V4L2 drivers must mute at load time to avoid excessive +noise. Actually the entire device should be reset to a low power +consumption state. + + + V4L2_CID_AUDIO_LOUDNESS + boolean + Loudness mode (bass boost). + + + V4L2_CID_BLACK_LEVEL + integer + Another name for brightness (not a synonym of +V4L2_CID_BRIGHTNESS). This control is deprecated +and should not be used in new drivers and applications. + + + V4L2_CID_AUTO_WHITE_BALANCE + boolean + Automatic white balance (cameras). + + + V4L2_CID_DO_WHITE_BALANCE + button + This is an action control. When set (the value is +ignored), the device will do a white balance and then hold the current +setting. Contrast this with the boolean +V4L2_CID_AUTO_WHITE_BALANCE, which, when +activated, keeps adjusting the white balance. + + + V4L2_CID_RED_BALANCE + integer + Red chroma balance. + + + V4L2_CID_BLUE_BALANCE + integer + Blue chroma balance. + + + V4L2_CID_GAMMA + integer + Gamma adjust. + + + V4L2_CID_WHITENESS + integer + Whiteness for grey-scale devices. This is a synonym +for V4L2_CID_GAMMA. This control is deprecated +and should not be used in new drivers and applications. + + + V4L2_CID_EXPOSURE + integer + Exposure (cameras). [Unit?] + + + V4L2_CID_AUTOGAIN + boolean + Automatic gain/exposure control. + + + V4L2_CID_GAIN + integer + Gain control. + + + V4L2_CID_HFLIP + boolean + Mirror the picture horizontally. + + + V4L2_CID_VFLIP + boolean + Mirror the picture vertically. + + + V4L2_CID_HCENTER_DEPRECATED (formerly V4L2_CID_HCENTER) + integer + Horizontal image centering. This control is +deprecated. New drivers and applications should use the Camera class controls +V4L2_CID_PAN_ABSOLUTE, +V4L2_CID_PAN_RELATIVE and +V4L2_CID_PAN_RESET instead. + + + V4L2_CID_VCENTER_DEPRECATED + (formerly V4L2_CID_VCENTER) + integer + Vertical image centering. Centering is intended to +physically adjust cameras. For image cropping see +, for clipping . This +control is deprecated. New drivers and applications should use the +Camera class controls +V4L2_CID_TILT_ABSOLUTE, +V4L2_CID_TILT_RELATIVE and +V4L2_CID_TILT_RESET instead. + + + V4L2_CID_POWER_LINE_FREQUENCY + integer + Enables a power line frequency filter to avoid +flicker. Possible values are: +V4L2_CID_POWER_LINE_FREQUENCY_DISABLED (0), +V4L2_CID_POWER_LINE_FREQUENCY_50HZ (1) and +V4L2_CID_POWER_LINE_FREQUENCY_60HZ (2). + + + V4L2_CID_HUE_AUTO + boolean + Enables automatic hue control by the device. The +effect of setting V4L2_CID_HUE while automatic +hue control is enabled is undefined, drivers should ignore such +request. + + + V4L2_CID_WHITE_BALANCE_TEMPERATURE + integer + This control specifies the white balance settings +as a color temperature in Kelvin. A driver should have a minimum of +2800 (incandescent) to 6500 (daylight). For more information about +color temperature see Wikipedia. + + + V4L2_CID_SHARPNESS + integer + Adjusts the sharpness filters in a camera. The +minimum value disables the filters, higher values give a sharper +picture. + + + V4L2_CID_BACKLIGHT_COMPENSATION + integer + Adjusts the backlight compensation in a camera. The +minimum value disables backlight compensation. + + + V4L2_CID_LASTP1 + + End of the predefined control IDs (currently +V4L2_CID_BACKLIGHT_COMPENSATION + 1). + + + V4L2_CID_PRIVATE_BASE + + ID of the first custom (driver specific) control. +Applications depending on particular custom controls should check the +driver name and version, see . + + + +
+ + Applications can enumerate the available controls with the +&VIDIOC-QUERYCTRL; and &VIDIOC-QUERYMENU; ioctls, get and set a +control value with the &VIDIOC-G-CTRL; and &VIDIOC-S-CTRL; ioctls. +Drivers must implement VIDIOC_QUERYCTRL, +VIDIOC_G_CTRL and +VIDIOC_S_CTRL when the device has one or more +controls, VIDIOC_QUERYMENU when it has one or +more menu type controls. + + + Enumerating all controls + + +&v4l2-queryctrl; queryctrl; +&v4l2-querymenu; querymenu; + +static void +enumerate_menu (void) +{ + printf (" Menu items:\n"); + + memset (&querymenu, 0, sizeof (querymenu)); + querymenu.id = queryctrl.id; + + for (querymenu.index = queryctrl.minimum; + querymenu.index <= queryctrl.maximum; + querymenu.index++) { + if (0 == ioctl (fd, &VIDIOC-QUERYMENU;, &querymenu)) { + printf (" %s\n", querymenu.name); + } else { + perror ("VIDIOC_QUERYMENU"); + exit (EXIT_FAILURE); + } + } +} + +memset (&queryctrl, 0, sizeof (queryctrl)); + +for (queryctrl.id = V4L2_CID_BASE; + queryctrl.id < V4L2_CID_LASTP1; + queryctrl.id++) { + if (0 == ioctl (fd, &VIDIOC-QUERYCTRL;, &queryctrl)) { + if (queryctrl.flags & V4L2_CTRL_FLAG_DISABLED) + continue; + + printf ("Control %s\n", queryctrl.name); + + if (queryctrl.type == V4L2_CTRL_TYPE_MENU) + enumerate_menu (); + } else { + if (errno == EINVAL) + continue; + + perror ("VIDIOC_QUERYCTRL"); + exit (EXIT_FAILURE); + } +} + +for (queryctrl.id = V4L2_CID_PRIVATE_BASE;; + queryctrl.id++) { + if (0 == ioctl (fd, &VIDIOC-QUERYCTRL;, &queryctrl)) { + if (queryctrl.flags & V4L2_CTRL_FLAG_DISABLED) + continue; + + printf ("Control %s\n", queryctrl.name); + + if (queryctrl.type == V4L2_CTRL_TYPE_MENU) + enumerate_menu (); + } else { + if (errno == EINVAL) + break; + + perror ("VIDIOC_QUERYCTRL"); + exit (EXIT_FAILURE); + } +} + + + + + Changing controls + + +&v4l2-queryctrl; queryctrl; +&v4l2-control; control; + +memset (&queryctrl, 0, sizeof (queryctrl)); +queryctrl.id = V4L2_CID_BRIGHTNESS; + +if (-1 == ioctl (fd, &VIDIOC-QUERYCTRL;, &queryctrl)) { + if (errno != EINVAL) { + perror ("VIDIOC_QUERYCTRL"); + exit (EXIT_FAILURE); + } else { + printf ("V4L2_CID_BRIGHTNESS is not supported\n"); + } +} else if (queryctrl.flags & V4L2_CTRL_FLAG_DISABLED) { + printf ("V4L2_CID_BRIGHTNESS is not supported\n"); +} else { + memset (&control, 0, sizeof (control)); + control.id = V4L2_CID_BRIGHTNESS; + control.value = queryctrl.default_value; + + if (-1 == ioctl (fd, &VIDIOC-S-CTRL;, &control)) { + perror ("VIDIOC_S_CTRL"); + exit (EXIT_FAILURE); + } +} + +memset (&control, 0, sizeof (control)); +control.id = V4L2_CID_CONTRAST; + +if (0 == ioctl (fd, &VIDIOC-G-CTRL;, &control)) { + control.value += 1; + + /* The driver may clamp the value or return ERANGE, ignored here */ + + if (-1 == ioctl (fd, &VIDIOC-S-CTRL;, &control) + && errno != ERANGE) { + perror ("VIDIOC_S_CTRL"); + exit (EXIT_FAILURE); + } +/* Ignore if V4L2_CID_CONTRAST is unsupported */ +} else if (errno != EINVAL) { + perror ("VIDIOC_G_CTRL"); + exit (EXIT_FAILURE); +} + +control.id = V4L2_CID_AUDIO_MUTE; +control.value = TRUE; /* silence */ + +/* Errors ignored */ +ioctl (fd, VIDIOC_S_CTRL, &control); + + +
+ +
+ Extended Controls + +
+ Introduction + + The control mechanism as originally designed was meant +to be used for user settings (brightness, saturation, etc). However, +it turned out to be a very useful model for implementing more +complicated driver APIs where each driver implements only a subset of +a larger API. + + The MPEG encoding API was the driving force behind +designing and implementing this extended control mechanism: the MPEG +standard is quite large and the currently supported hardware MPEG +encoders each only implement a subset of this standard. Further more, +many parameters relating to how the video is encoded into an MPEG +stream are specific to the MPEG encoding chip since the MPEG standard +only defines the format of the resulting MPEG stream, not how the +video is actually encoded into that format. + + Unfortunately, the original control API lacked some +features needed for these new uses and so it was extended into the +(not terribly originally named) extended control API. +
+ +
+ The Extended Control API + + Three new ioctls are available: &VIDIOC-G-EXT-CTRLS;, +&VIDIOC-S-EXT-CTRLS; and &VIDIOC-TRY-EXT-CTRLS;. These ioctls act on +arrays of controls (as opposed to the &VIDIOC-G-CTRL; and +&VIDIOC-S-CTRL; ioctls that act on a single control). This is needed +since it is often required to atomically change several controls at +once. + + Each of the new ioctls expects a pointer to a +&v4l2-ext-controls;. This structure contains a pointer to the control +array, a count of the number of controls in that array and a control +class. Control classes are used to group similar controls into a +single class. For example, control class +V4L2_CTRL_CLASS_USER contains all user controls +(&ie; all controls that can also be set using the old +VIDIOC_S_CTRL ioctl). Control class +V4L2_CTRL_CLASS_MPEG contains all controls +relating to MPEG encoding, etc. + + All controls in the control array must belong to the +specified control class. An error is returned if this is not the +case. + + It is also possible to use an empty control array (count +== 0) to check whether the specified control class is +supported. + + The control array is a &v4l2-ext-control; array. The +v4l2_ext_control structure is very similar to +&v4l2-control;, except for the fact that it also allows for 64-bit +values and pointers to be passed (although the latter is not yet used +anywhere). + + It is important to realize that due to the flexibility of +controls it is necessary to check whether the control you want to set +actually is supported in the driver and what the valid range of values +is. So use the &VIDIOC-QUERYCTRL; and &VIDIOC-QUERYMENU; ioctls to +check this. Also note that it is possible that some of the menu +indices in a control of type V4L2_CTRL_TYPE_MENU +may not be supported (VIDIOC_QUERYMENU will +return an error). A good example is the list of supported MPEG audio +bitrates. Some drivers only support one or two bitrates, others +support a wider range. +
+ +
+ Enumerating Extended Controls + + The recommended way to enumerate over the extended +controls is by using &VIDIOC-QUERYCTRL; in combination with the +V4L2_CTRL_FLAG_NEXT_CTRL flag: + + + +&v4l2-queryctrl; qctrl; + +qctrl.id = V4L2_CTRL_FLAG_NEXT_CTRL; +while (0 == ioctl (fd, &VIDIOC-QUERYCTRL;, &qctrl)) { + /* ... */ + qctrl.id |= V4L2_CTRL_FLAG_NEXT_CTRL; +} + + + + The initial control ID is set to 0 ORed with the +V4L2_CTRL_FLAG_NEXT_CTRL flag. The +VIDIOC_QUERYCTRL ioctl will return the first +control with a higher ID than the specified one. When no such controls +are found an error is returned. + + If you want to get all controls within a specific control +class, then you can set the initial +qctrl.id value to the control class and add +an extra check to break out of the loop when a control of another +control class is found: + + + +qctrl.id = V4L2_CTRL_CLASS_MPEG | V4L2_CTRL_FLAG_NEXT_CTRL; +while (0 == ioctl (fd, &VIDIOC-QUERYCTRL, &qctrl)) { + if (V4L2_CTRL_ID2CLASS (qctrl.id) != V4L2_CTRL_CLASS_MPEG) + break; + /* ... */ + qctrl.id |= V4L2_CTRL_FLAG_NEXT_CTRL; + } + + + + The 32-bit qctrl.id value is +subdivided into three bit ranges: the top 4 bits are reserved for +flags (⪚ V4L2_CTRL_FLAG_NEXT_CTRL) and are not +actually part of the ID. The remaining 28 bits form the control ID, of +which the most significant 12 bits define the control class and the +least significant 16 bits identify the control within the control +class. It is guaranteed that these last 16 bits are always non-zero +for controls. The range of 0x1000 and up are reserved for +driver-specific controls. The macro +V4L2_CTRL_ID2CLASS(id) returns the control class +ID based on a control ID. + + If the driver does not support extended controls, then +VIDIOC_QUERYCTRL will fail when used in +combination with V4L2_CTRL_FLAG_NEXT_CTRL. In +that case the old method of enumerating control should be used (see +1.8). But if it is supported, then it is guaranteed to enumerate over +all controls, including driver-private controls. +
+ +
+ Creating Control Panels + + It is possible to create control panels for a graphical +user interface where the user can select the various controls. +Basically you will have to iterate over all controls using the method +described above. Each control class starts with a control of type +V4L2_CTRL_TYPE_CTRL_CLASS. +VIDIOC_QUERYCTRL will return the name of this +control class which can be used as the title of a tab page within a +control panel. + + The flags field of &v4l2-queryctrl; also contains hints on +the behavior of the control. See the &VIDIOC-QUERYCTRL; documentation +for more details. +
+ +
+ MPEG Control Reference + + Below all controls within the MPEG control class are +described. First the generic controls, then controls specific for +certain hardware. + +
+ Generic MPEG Controls + + + MPEG Control IDs + + + + + + + + + + ID + Type + Description + + + + + + V4L2_CID_MPEG_CLASS  + class + The MPEG class +descriptor. Calling &VIDIOC-QUERYCTRL; for this control will return a +description of this control class. This description can be used as the +caption of a Tab page in a GUI, for example. + + + + V4L2_CID_MPEG_STREAM_TYPE  + enum + The MPEG-1, -2 or -4 +output stream type. One cannot assume anything here. Each hardware +MPEG encoder tends to support different subsets of the available MPEG +stream types. The currently defined stream types are: + + + + + + V4L2_MPEG_STREAM_TYPE_MPEG2_PS  + MPEG-2 program stream + + + V4L2_MPEG_STREAM_TYPE_MPEG2_TS  + MPEG-2 transport stream + + + V4L2_MPEG_STREAM_TYPE_MPEG1_SS  + MPEG-1 system stream + + + V4L2_MPEG_STREAM_TYPE_MPEG2_DVD  + MPEG-2 DVD-compatible stream + + + V4L2_MPEG_STREAM_TYPE_MPEG1_VCD  + MPEG-1 VCD-compatible stream + + + V4L2_MPEG_STREAM_TYPE_MPEG2_SVCD  + MPEG-2 SVCD-compatible stream + + + + + + + V4L2_CID_MPEG_STREAM_PID_PMT  + integer + Program Map Table +Packet ID for the MPEG transport stream (default 16) + + + + V4L2_CID_MPEG_STREAM_PID_AUDIO  + integer + Audio Packet ID for +the MPEG transport stream (default 256) + + + + V4L2_CID_MPEG_STREAM_PID_VIDEO  + integer + Video Packet ID for +the MPEG transport stream (default 260) + + + + V4L2_CID_MPEG_STREAM_PID_PCR  + integer + Packet ID for the +MPEG transport stream carrying PCR fields (default 259) + + + + V4L2_CID_MPEG_STREAM_PES_ID_AUDIO  + integer + Audio ID for MPEG +PES + + + + V4L2_CID_MPEG_STREAM_PES_ID_VIDEO  + integer + Video ID for MPEG +PES + + + + V4L2_CID_MPEG_STREAM_VBI_FMT  + enum + Some cards can embed +VBI data (⪚ Closed Caption, Teletext) into the MPEG stream. This +control selects whether VBI data should be embedded, and if so, what +embedding method should be used. The list of possible VBI formats +depends on the driver. The currently defined VBI format types +are: + + + + + + V4L2_MPEG_STREAM_VBI_FMT_NONE  + No VBI in the MPEG stream + + + V4L2_MPEG_STREAM_VBI_FMT_IVTV  + VBI in private packets, IVTV format (documented +in the kernel sources in the file Documentation/video4linux/cx2341x/README.vbi) + + + + + + + V4L2_CID_MPEG_AUDIO_SAMPLING_FREQ  + enum + MPEG Audio sampling +frequency. Possible values are: + + + + + + V4L2_MPEG_AUDIO_SAMPLING_FREQ_44100  + 44.1 kHz + + + V4L2_MPEG_AUDIO_SAMPLING_FREQ_48000  + 48 kHz + + + V4L2_MPEG_AUDIO_SAMPLING_FREQ_32000  + 32 kHz + + + + + + + V4L2_CID_MPEG_AUDIO_ENCODING  + enum + MPEG Audio encoding. +Possible values are: + + + + + + V4L2_MPEG_AUDIO_ENCODING_LAYER_1  + MPEG Layer I encoding + + + V4L2_MPEG_AUDIO_ENCODING_LAYER_2  + MPEG Layer II encoding + + + V4L2_MPEG_AUDIO_ENCODING_LAYER_3  + MPEG Layer III encoding + + + + + + + V4L2_CID_MPEG_AUDIO_L1_BITRATE  + enum + Layer I bitrate. +Possible values are: + + + + + + V4L2_MPEG_AUDIO_L1_BITRATE_32K  + 32 kbit/s + + V4L2_MPEG_AUDIO_L1_BITRATE_64K  + 64 kbit/s + + + V4L2_MPEG_AUDIO_L1_BITRATE_96K  + 96 kbit/s + + + V4L2_MPEG_AUDIO_L1_BITRATE_128K  + 128 kbit/s + + + V4L2_MPEG_AUDIO_L1_BITRATE_160K  + 160 kbit/s + + + V4L2_MPEG_AUDIO_L1_BITRATE_192K  + 192 kbit/s + + + V4L2_MPEG_AUDIO_L1_BITRATE_224K  + 224 kbit/s + + + V4L2_MPEG_AUDIO_L1_BITRATE_256K  + 256 kbit/s + + + V4L2_MPEG_AUDIO_L1_BITRATE_288K  + 288 kbit/s + + + V4L2_MPEG_AUDIO_L1_BITRATE_320K  + 320 kbit/s + + + V4L2_MPEG_AUDIO_L1_BITRATE_352K  + 352 kbit/s + + + V4L2_MPEG_AUDIO_L1_BITRATE_384K  + 384 kbit/s + + + V4L2_MPEG_AUDIO_L1_BITRATE_416K  + 416 kbit/s + + + V4L2_MPEG_AUDIO_L1_BITRATE_448K  + 448 kbit/s + + + + + + + V4L2_CID_MPEG_AUDIO_L2_BITRATE  + enum + Layer II bitrate. +Possible values are: + + + + + + V4L2_MPEG_AUDIO_L2_BITRATE_32K  + 32 kbit/s + + + V4L2_MPEG_AUDIO_L2_BITRATE_48K  + 48 kbit/s + + + V4L2_MPEG_AUDIO_L2_BITRATE_56K  + 56 kbit/s + + + V4L2_MPEG_AUDIO_L2_BITRATE_64K  + 64 kbit/s + + + V4L2_MPEG_AUDIO_L2_BITRATE_80K  + 80 kbit/s + + + V4L2_MPEG_AUDIO_L2_BITRATE_96K  + 96 kbit/s + + + V4L2_MPEG_AUDIO_L2_BITRATE_112K  + 112 kbit/s + + + V4L2_MPEG_AUDIO_L2_BITRATE_128K  + 128 kbit/s + + + V4L2_MPEG_AUDIO_L2_BITRATE_160K  + 160 kbit/s + + + V4L2_MPEG_AUDIO_L2_BITRATE_192K  + 192 kbit/s + + + V4L2_MPEG_AUDIO_L2_BITRATE_224K  + 224 kbit/s + + + V4L2_MPEG_AUDIO_L2_BITRATE_256K  + 256 kbit/s + + + V4L2_MPEG_AUDIO_L2_BITRATE_320K  + 320 kbit/s + + + V4L2_MPEG_AUDIO_L2_BITRATE_384K  + 384 kbit/s + + + + + + + V4L2_CID_MPEG_AUDIO_L3_BITRATE  + enum + Layer III bitrate. +Possible values are: + + + + + + V4L2_MPEG_AUDIO_L3_BITRATE_32K  + 32 kbit/s + + + V4L2_MPEG_AUDIO_L3_BITRATE_40K  + 40 kbit/s + + + V4L2_MPEG_AUDIO_L3_BITRATE_48K  + 48 kbit/s + + + V4L2_MPEG_AUDIO_L3_BITRATE_56K  + 56 kbit/s + + + V4L2_MPEG_AUDIO_L3_BITRATE_64K  + 64 kbit/s + + + V4L2_MPEG_AUDIO_L3_BITRATE_80K  + 80 kbit/s + + + V4L2_MPEG_AUDIO_L3_BITRATE_96K  + 96 kbit/s + + + V4L2_MPEG_AUDIO_L3_BITRATE_112K  + 112 kbit/s + + + V4L2_MPEG_AUDIO_L3_BITRATE_128K  + 128 kbit/s + + + V4L2_MPEG_AUDIO_L3_BITRATE_160K  + 160 kbit/s + + + V4L2_MPEG_AUDIO_L3_BITRATE_192K  + 192 kbit/s + + + V4L2_MPEG_AUDIO_L3_BITRATE_224K  + 224 kbit/s + + + V4L2_MPEG_AUDIO_L3_BITRATE_256K  + 256 kbit/s + + + V4L2_MPEG_AUDIO_L3_BITRATE_320K  + 320 kbit/s + + + + + + + V4L2_CID_MPEG_AUDIO_MODE  + enum + MPEG Audio mode. +Possible values are: + + + + + + V4L2_MPEG_AUDIO_MODE_STEREO  + Stereo + + + V4L2_MPEG_AUDIO_MODE_JOINT_STEREO  + Joint Stereo + + + V4L2_MPEG_AUDIO_MODE_DUAL  + Bilingual + + + V4L2_MPEG_AUDIO_MODE_MONO  + Mono + + + + + + + V4L2_CID_MPEG_AUDIO_MODE_EXTENSION  + enum + Joint Stereo +audio mode extension. In Layer I and II they indicate which subbands +are in intensity stereo. All other subbands are coded in stereo. Layer +III is not (yet) supported. Possible values +are: + + + + + + V4L2_MPEG_AUDIO_MODE_EXTENSION_BOUND_4  + Subbands 4-31 in intensity stereo + + + V4L2_MPEG_AUDIO_MODE_EXTENSION_BOUND_8  + Subbands 8-31 in intensity stereo + + + V4L2_MPEG_AUDIO_MODE_EXTENSION_BOUND_12  + Subbands 12-31 in intensity stereo + + + V4L2_MPEG_AUDIO_MODE_EXTENSION_BOUND_16  + Subbands 16-31 in intensity stereo + + + + + + + V4L2_CID_MPEG_AUDIO_EMPHASIS  + enum + Audio Emphasis. +Possible values are: + + + + + + V4L2_MPEG_AUDIO_EMPHASIS_NONE  + None + + + V4L2_MPEG_AUDIO_EMPHASIS_50_DIV_15_uS  + 50/15 microsecond emphasis + + + V4L2_MPEG_AUDIO_EMPHASIS_CCITT_J17  + CCITT J.17 + + + + + + + V4L2_CID_MPEG_AUDIO_CRC  + enum + CRC method. Possible +values are: + + + + + + V4L2_MPEG_AUDIO_CRC_NONE  + None + + + V4L2_MPEG_AUDIO_CRC_CRC16  + 16 bit parity check + + + + + + + V4L2_CID_MPEG_AUDIO_MUTE  + bool + Mutes the audio when +capturing. This is not done by muting audio hardware, which can still +produce a slight hiss, but in the encoder itself, guaranteeing a fixed +and reproducable audio bitstream. 0 = unmuted, 1 = muted. + + + + V4L2_CID_MPEG_VIDEO_ENCODING  + enum + MPEG Video encoding +method. Possible values are: + + + + + + V4L2_MPEG_VIDEO_ENCODING_MPEG_1  + MPEG-1 Video encoding + + + V4L2_MPEG_VIDEO_ENCODING_MPEG_2  + MPEG-2 Video encoding + + + + + + + V4L2_CID_MPEG_VIDEO_ASPECT  + enum + Video aspect. +Possible values are: + + + + + + V4L2_MPEG_VIDEO_ASPECT_1x1  + + + V4L2_MPEG_VIDEO_ASPECT_4x3  + + + V4L2_MPEG_VIDEO_ASPECT_16x9  + + + V4L2_MPEG_VIDEO_ASPECT_221x100  + + + + + + + V4L2_CID_MPEG_VIDEO_B_FRAMES  + integer + Number of B-Frames +(default 2) + + + + V4L2_CID_MPEG_VIDEO_GOP_SIZE  + integer + GOP size (default +12) + + + + V4L2_CID_MPEG_VIDEO_GOP_CLOSURE  + bool + GOP closure (default +1) + + + + V4L2_CID_MPEG_VIDEO_PULLDOWN  + bool + Enable 3:2 pulldown +(default 0) + + + + V4L2_CID_MPEG_VIDEO_BITRATE_MODE  + enum + Video bitrate mode. +Possible values are: + + + + + + V4L2_MPEG_VIDEO_BITRATE_MODE_VBR  + Variable bitrate + + + V4L2_MPEG_VIDEO_BITRATE_MODE_CBR  + Constant bitrate + + + + + + + V4L2_CID_MPEG_VIDEO_BITRATE  + integer + Video bitrate in bits +per second. + + + + V4L2_CID_MPEG_VIDEO_BITRATE_PEAK  + integer + Peak video bitrate in +bits per second. Must be larger or equal to the average video bitrate. +It is ignored if the video bitrate mode is set to constant +bitrate. + + + + V4L2_CID_MPEG_VIDEO_TEMPORAL_DECIMATION  + integer + For every captured +frame, skip this many subsequent frames (default 0). + + + + V4L2_CID_MPEG_VIDEO_MUTE  + bool + + "Mutes" the video to a +fixed color when capturing. This is useful for testing, to produce a +fixed video bitstream. 0 = unmuted, 1 = muted. + + + + V4L2_CID_MPEG_VIDEO_MUTE_YUV  + integer + Sets the "mute" color +of the video. The supplied 32-bit integer is interpreted as follows (bit +0 = least significant bit): + + + + + + Bit 0:7 + V chrominance information + + + Bit 8:15 + U chrominance information + + + Bit 16:23 + Y luminance information + + + Bit 24:31 + Must be zero. + + + + + + +
+
+ +
+ CX2341x MPEG Controls + + The following MPEG class controls deal with MPEG +encoding settings that are specific to the Conexant CX23415 and +CX23416 MPEG encoding chips. + + + CX2341x Control IDs + + + + + + + + + + ID + Type + Description + + + + + + V4L2_CID_MPEG_CX2341X_VIDEO_SPATIAL_FILTER_MODE  + enum + Sets the Spatial +Filter mode (default MANUAL). Possible values +are: + + + + + + V4L2_MPEG_CX2341X_VIDEO_SPATIAL_FILTER_MODE_MANUAL  + Choose the filter manually + + + V4L2_MPEG_CX2341X_VIDEO_SPATIAL_FILTER_MODE_AUTO  + Choose the filter automatically + + + + + + + V4L2_CID_MPEG_CX2341X_VIDEO_SPATIAL_FILTER  + integer (0-15) + The setting for the +Spatial Filter. 0 = off, 15 = maximum. (Default is 0.) + + + + V4L2_CID_MPEG_CX2341X_VIDEO_LUMA_SPATIAL_FILTER_TYPE  + enum + Select the algorithm +to use for the Luma Spatial Filter (default +1D_HOR). Possible values: + + + + + + V4L2_MPEG_CX2341X_VIDEO_LUMA_SPATIAL_FILTER_TYPE_OFF  + No filter + + + V4L2_MPEG_CX2341X_VIDEO_LUMA_SPATIAL_FILTER_TYPE_1D_HOR  + One-dimensional horizontal + + + V4L2_MPEG_CX2341X_VIDEO_LUMA_SPATIAL_FILTER_TYPE_1D_VERT  + One-dimensional vertical + + + V4L2_MPEG_CX2341X_VIDEO_LUMA_SPATIAL_FILTER_TYPE_2D_HV_SEPARABLE  + Two-dimensional separable + + + V4L2_MPEG_CX2341X_VIDEO_LUMA_SPATIAL_FILTER_TYPE_2D_SYM_NON_SEPARABLE  + Two-dimensional symmetrical +non-separable + + + + + + + V4L2_CID_MPEG_CX2341X_VIDEO_CHROMA_SPATIAL_FILTER_TYPE  + enum + Select the algorithm +for the Chroma Spatial Filter (default 1D_HOR). +Possible values are: + + + + + + V4L2_MPEG_CX2341X_VIDEO_CHROMA_SPATIAL_FILTER_TYPE_OFF  + No filter + + + V4L2_MPEG_CX2341X_VIDEO_CHROMA_SPATIAL_FILTER_TYPE_1D_HOR  + One-dimensional horizontal + + + + + + + V4L2_CID_MPEG_CX2341X_VIDEO_TEMPORAL_FILTER_MODE  + enum + Sets the Temporal +Filter mode (default MANUAL). Possible values +are: + + + + + + V4L2_MPEG_CX2341X_VIDEO_TEMPORAL_FILTER_MODE_MANUAL  + Choose the filter manually + + + V4L2_MPEG_CX2341X_VIDEO_TEMPORAL_FILTER_MODE_AUTO  + Choose the filter automatically + + + + + + + V4L2_CID_MPEG_CX2341X_VIDEO_TEMPORAL_FILTER  + integer (0-31) + The setting for the +Temporal Filter. 0 = off, 31 = maximum. (Default is 8 for full-scale +capturing and 0 for scaled capturing.) + + + + V4L2_CID_MPEG_CX2341X_VIDEO_MEDIAN_FILTER_TYPE  + enum + Median Filter Type +(default OFF). Possible values are: + + + + + + V4L2_MPEG_CX2341X_VIDEO_MEDIAN_FILTER_TYPE_OFF  + No filter + + + V4L2_MPEG_CX2341X_VIDEO_MEDIAN_FILTER_TYPE_HOR  + Horizontal filter + + + V4L2_MPEG_CX2341X_VIDEO_MEDIAN_FILTER_TYPE_VERT  + Vertical filter + + + V4L2_MPEG_CX2341X_VIDEO_MEDIAN_FILTER_TYPE_HOR_VERT  + Horizontal and vertical filter + + + V4L2_MPEG_CX2341X_VIDEO_MEDIAN_FILTER_TYPE_DIAG  + Diagonal filter + + + + + + + V4L2_CID_MPEG_CX2341X_VIDEO_LUMA_MEDIAN_FILTER_BOTTOM  + integer (0-255) + Threshold above which +the luminance median filter is enabled (default 0) + + + + V4L2_CID_MPEG_CX2341X_VIDEO_LUMA_MEDIAN_FILTER_TOP  + integer (0-255) + Threshold below which +the luminance median filter is enabled (default 255) + + + + V4L2_CID_MPEG_CX2341X_VIDEO_CHROMA_MEDIAN_FILTER_BOTTOM  + integer (0-255) + Threshold above which +the chroma median filter is enabled (default 0) + + + + V4L2_CID_MPEG_CX2341X_VIDEO_CHROMA_MEDIAN_FILTER_TOP  + integer (0-255) + Threshold below which +the chroma median filter is enabled (default 255) + + + + V4L2_CID_MPEG_CX2341X_STREAM_INSERT_NAV_PACKETS  + bool + + The CX2341X MPEG encoder +can insert one empty MPEG-2 PES packet into the stream between every +four video frames. The packet size is 2048 bytes, including the +packet_start_code_prefix and stream_id fields. The stream_id is 0xBF +(private stream 2). The payload consists of 0x00 bytes, to be filled +in by the application. 0 = do not insert, 1 = insert packets. + + + +
+
+
+ +
+ Camera Control Reference + + The Camera class includes controls for mechanical (or +equivalent digital) features of a device such as controllable lenses +or sensors. + + + Camera Control IDs + + + + + + + + + + ID + Type + Description + + + + + + V4L2_CID_CAMERA_CLASS  + class + The Camera class +descriptor. Calling &VIDIOC-QUERYCTRL; for this control will return a +description of this control class. + + + + + V4L2_CID_EXPOSURE_AUTO  + integer + Enables automatic +adjustments of the exposure time and/or iris aperture. The effect of +manual changes of the exposure time or iris aperture while these +features are enabled is undefined, drivers should ignore such +requests. Possible values are: + + + + + + V4L2_EXPOSURE_AUTO  + Automatic exposure time, automatic iris +aperture. + + + V4L2_EXPOSURE_MANUAL  + Manual exposure time, manual iris. + + + V4L2_EXPOSURE_SHUTTER_PRIORITY  + Manual exposure time, auto iris. + + + V4L2_EXPOSURE_APERTURE_PRIORITY  + Auto exposure time, manual iris. + + + + + + + + V4L2_CID_EXPOSURE_ABSOLUTE  + integer + Determines the exposure +time of the camera sensor. The exposure time is limited by the frame +interval. Drivers should interpret the values as 100 µs units, +where the value 1 stands for 1/10000th of a second, 10000 for 1 second +and 100000 for 10 seconds. + + + + + V4L2_CID_EXPOSURE_AUTO_PRIORITY  + boolean + When +V4L2_CID_EXPOSURE_AUTO is set to +AUTO or SHUTTER_PRIORITY, +this control determines if the device may dynamically vary the frame +rate. By default this feature is disabled (0) and the frame rate must +remain constant. + + + + + V4L2_CID_PAN_RELATIVE  + integer + This control turns the +camera horizontally by the specified amount. The unit is undefined. A +positive value moves the camera to the right (clockwise when viewed +from above), a negative value to the left. A value of zero does not +cause motion. + + + + + V4L2_CID_TILT_RELATIVE  + integer + This control turns the +camera vertically by the specified amount. The unit is undefined. A +positive value moves the camera up, a negative value down. A value of +zero does not cause motion. + + + + + V4L2_CID_PAN_RESET  + boolean + When this control is set +to TRUE (1), the camera moves horizontally to the +default position. + + + + + V4L2_CID_TILT_RESET  + boolean + When this control is set +to TRUE (1), the camera moves vertically to the +default position. + + + + + V4L2_CID_PAN_ABSOLUTE  + integer + This control +turns the camera horizontally to the specified position. Positive +values move the camera to the right (clockwise when viewed from above), +negative values to the left. Drivers should interpret the values as arc +seconds, with valid values between -180 * 3600 and +180 * 3600 +inclusive. + + + + + V4L2_CID_TILT_ABSOLUTE  + integer + This control +turns the camera vertically to the specified position. Positive values +move the camera up, negative values down. Drivers should interpret the +values as arc seconds, with valid values between -180 * 3600 and +180 +* 3600 inclusive. + + + + + V4L2_CID_FOCUS_ABSOLUTE  + integer + This control sets the +focal point of the camera to the specified position. The unit is +undefined. Positive values set the focus closer to the camera, +negative values towards infinity. + + + + + V4L2_CID_FOCUS_RELATIVE  + integer + This control moves the +focal point of the camera by the specified amount. The unit is +undefined. Positive values move the focus closer to the camera, +negative values towards infinity. + + + + + V4L2_CID_FOCUS_AUTO  + boolean + Enables automatic focus +adjustments. The effect of manual focus adjustments while this feature +is enabled is undefined, drivers should ignore such requests. + + + + +
+
+
+ + diff --git a/v4l2-spec/crop.gif b/v4l2-spec/crop.gif new file mode 100644 index 000000000..3b9e7d836 Binary files /dev/null and b/v4l2-spec/crop.gif differ diff --git a/v4l2-spec/crop.pdf b/v4l2-spec/crop.pdf new file mode 100644 index 000000000..c9fb81cd3 Binary files /dev/null and b/v4l2-spec/crop.pdf differ diff --git a/v4l2-spec/custom.dsl b/v4l2-spec/custom.dsl new file mode 100644 index 000000000..12a5e91d4 --- /dev/null +++ b/v4l2-spec/custom.dsl @@ -0,0 +1,52 @@ + + + +]]> + + +]]> +]> + + + + + + + +(define %generate-reference-toc% #t) +(define %refentry-new-page% #t) +(define %number-programlisting-lines% #f) +(define %section-autolabel% #t) +(define bop-footnotes #t) + +(define ($generate-book-lot-list$) + (list (normalize "figure") + (normalize "example"))) + +(define %paper-type% "A4") + + + + + + + + +(define %generate-reference-toc% #t) +(define %number-programlisting-lines% #f) +(define %section-autolabel% #t) +(define bop-footnotes #t) + +(define ($generate-book-lot-list$) + (list (normalize "figure") + (normalize "example"))) + + + + + + + diff --git a/v4l2-spec/dev-capture.sgml b/v4l2-spec/dev-capture.sgml new file mode 100644 index 000000000..d2885988b --- /dev/null +++ b/v4l2-spec/dev-capture.sgml @@ -0,0 +1,115 @@ + Video Capture Interface + + Video capture devices sample an analog video signal and store +the digitized images in memory. Today nearly all devices can capture +at full 25 or 30 frames/second. With this interface applications can +control the capture process and move images from the driver into user +space. + + Conventionally V4L2 video capture devices are accessed through +character device special files named /dev/video +and /dev/video0 to +/dev/video63 with major number 81 and minor +numbers 0 to 63. /dev/video is typically a +symbolic link to the preferred video device. Note the same device +files are used for video output devices. + +
+ Querying Capabilities + + Devices supporting the video capture interface set the +V4L2_CAP_VIDEO_CAPTURE flag in the +capabilities field of &v4l2-capability; +returned by the &VIDIOC-QUERYCAP; ioctl. As secondary device functions +they may also support the video overlay +(V4L2_CAP_VIDEO_OVERLAY) and the raw VBI capture +(V4L2_CAP_VBI_CAPTURE) interface. At least one of +the read/write or streaming I/O methods must be supported. Tuners and +audio inputs are optional. +
+ +
+ Supplemental Functions + + Video capture devices shall support audio input, tuner, controls, +cropping and scaling and streaming parameter ioctls as needed. +The video input and video standard ioctls must be supported by +all video capture devices. +
+ +
+ Image Format Negotiation + + The result of a capture operation is determined by +cropping and image format parameters. The former select an area of the +video picture to capture, the latter how images are stored in memory, +&ie; in RGB or YUV format, the number of bits per pixel or width and +height. Together they also define how images are scaled in the +process. + + As usual these parameters are not reset +at &func-open; time to permit Unix tool chains, programming a device +and then reading from it as if it was a plain file. Well written V4L2 +applications ensure they really get what they want, including cropping +and scaling. + + Cropping initialization at minimum requires to reset the +parameters to defaults. An example is given in . + + To query the current image format applications set the +type field of a &v4l2-format; to +V4L2_BUF_TYPE_VIDEO_CAPTURE and call the +&VIDIOC-G-FMT; ioctl with a pointer to this structure. Drivers fill +the &v4l2-pix-format; pix member of the +fmt union. + + To request different parameters applications set the +type field of a &v4l2-format; as above and +initialize all fields of the &v4l2-pix-format; +vbi member of the +fmt union, or better just modify the +results of VIDIOC_G_FMT, and call the +&VIDIOC-S-FMT; ioctl with a pointer to this structure. Drivers may +adjust the parameters and finally return the actual parameters as +VIDIOC_G_FMT does. + + Like VIDIOC_S_FMT the +&VIDIOC-TRY-FMT; ioctl can be used to learn about hardware limitations +without disabling I/O or possibly time consuming hardware +preparations. + + The contents of &v4l2-pix-format; are discussed in . See also the specification of the +VIDIOC_G_FMT, VIDIOC_S_FMT +and VIDIOC_TRY_FMT ioctls for details. Video +capture devices must implement both the +VIDIOC_G_FMT and +VIDIOC_S_FMT ioctl, even if +VIDIOC_S_FMT ignores all requests and always +returns default parameters as VIDIOC_G_FMT does. +VIDIOC_TRY_FMT is optional. +
+ +
+ Reading Images + + A video capture device may support the read() function and/or streaming (memory mapping or user pointer) I/O. See for details. +
+ + diff --git a/v4l2-spec/dev-codec.sgml b/v4l2-spec/dev-codec.sgml new file mode 100644 index 000000000..6e156dc45 --- /dev/null +++ b/v4l2-spec/dev-codec.sgml @@ -0,0 +1,26 @@ + Codec Interface + + + Suspended + + This interface has been be suspended from the V4L2 API +implemented in Linux 2.6 until we have more experience with codec +device interfaces. + + + A V4L2 codec can compress, decompress, transform, or otherwise +convert video data from one format into another format, in memory. +Applications send data to be converted to the driver through a +&func-write; call, and receive the converted data through a +&func-read; call. For efficiency a driver may also support streaming +I/O. + + [to do] + + diff --git a/v4l2-spec/dev-effect.sgml b/v4l2-spec/dev-effect.sgml new file mode 100644 index 000000000..9c243beba --- /dev/null +++ b/v4l2-spec/dev-effect.sgml @@ -0,0 +1,25 @@ + Effect Devices Interface + + + Suspended + + This interface has been be suspended from the V4L2 API +implemented in Linux 2.6 until we have more experience with effect +device interfaces. + + + A V4L2 video effect device can do image effects, filtering, or +combine two or more images or image streams. For example video +transitions or wipes. Applications send data to be processed and +receive the result data either with &func-read; and &func-write; +functions, or through the streaming I/O mechanism. + + [to do] + + diff --git a/v4l2-spec/dev-osd.sgml b/v4l2-spec/dev-osd.sgml new file mode 100644 index 000000000..7210292fa --- /dev/null +++ b/v4l2-spec/dev-osd.sgml @@ -0,0 +1,164 @@ + Video Output Overlay Interface + Also known as On-Screen Display (OSD) + + + Experimental + + This is an experimental +interface and may change in the future. + + + Some video output devices can overlay a framebuffer image onto +the outgoing video signal. Applications can set up such an overlay +using this interface, which borrows structures and ioctls of the Video Overlay interface. + + The OSD function is accessible through the same character +special file as the Video Output function. +Note the default function of such a /dev/video device +is video capturing or output. The OSD function is only available after +calling the &VIDIOC-S-FMT; ioctl. + +
+ Querying Capabilities + + Devices supporting the Video Output +Overlay interface set the +V4L2_CAP_VIDEO_OUTPUT_OVERLAY flag in the +capabilities field of &v4l2-capability; +returned by the &VIDIOC-QUERYCAP; ioctl. +
+ +
+ Framebuffer + + Contrary to the Video Overlay +interface the framebuffer is normally implemented on the TV card and +not the graphics card. On Linux it is accessible as a framebuffer +device (/dev/fbN). Given a V4L2 device, +applications can find the corresponding framebuffer device by calling +the &VIDIOC-G-FBUF; ioctl. It returns, amongst other information, the +physical address of the framebuffer in the +base field of &v4l2-framebuffer;. The +framebuffer device ioctl FBIOGET_FSCREENINFO +returns the same address in the smem_start +field of struct fb_fix_screeninfo. The +FBIOGET_FSCREENINFO ioctl and struct +fb_fix_screeninfo are defined in the +linux/fb.h header file. + + The width and height of the framebuffer depends on the +current video standard. A V4L2 driver may reject attempts to change +the video standard (or any other ioctl which would imply a framebuffer +size change) with an &EBUSY; until all applications closed the +framebuffer device. + + + Finding a framebuffer device for OSD + + +#include <linux/fb.h> + +&v4l2-framebuffer fbuf; +unsigned int i; +int fb_fd; + +if (-1 == ioctl (fd, VIDIOC_G_FBUF, &fbuf)) { + perror ("VIDIOC_G_FBUF"); + exit (EXIT_FAILURE); +} + +for (i = 0; i < 30; ++i) { + char dev_name[16]; + struct fb_fix_screeninfo si; + + snprintf (dev_name, sizeof (dev_name), "/dev/fb%u", i); + + fb_fd = open (dev_name, O_RDWR); + if (-1 == fb_fd) { + switch (errno) { + case ENOENT: /* no such file */ + case ENXIO: /* no driver */ + continue; + + default: + perror ("open"); + exit (EXIT_FAILURE); + } + } + + if (0 == ioctl (fb_fd, FBIOGET_FSCREENINFO, &si)) { + if (si.smem_start == (unsigned long) fbuf.base) + break; + } else { + /* Apparently not a framebuffer device. */ + } + + close (fb_fd); + fb_fd = -1; +} + +/* fb_fd is the file descriptor of the framebuffer device + for the video output overlay, or -1 if no device was found. */ + + +
+ +
+ Overlay Window and Scaling + + The overlay is controlled by source and target rectangles. +The source rectangle selects a subsection of the framebuffer image to +be overlaid, the target rectangle an area in the outgoing video signal +where the image will appear. Drivers may or may not support scaling, +and arbitrary sizes and positions of these rectangles. Further drivers +may support any (or none) of the clipping/blending methods defined for +the Video Overlay interface. + + A &v4l2-window; defines the size of the source rectangle, +its position in the framebuffer and the clipping/blending method to be +used for the overlay. To get the current parameters applications set +the type field of a &v4l2-format; to +V4L2_BUF_TYPE_VIDEO_OUTPUT_OVERLAY and call the +&VIDIOC-G-FMT; ioctl. The driver fills the +v4l2_window substructure named +win. It is not possible to retrieve a +previously programmed clipping list or bitmap. + + To program the source rectangle applications set the +type field of a &v4l2-format; to +V4L2_BUF_TYPE_VIDEO_OUTPUT_OVERLAY, initialize +the win substructure and call the +&VIDIOC-S-FMT; ioctl. The driver adjusts the parameters against +hardware limits and returns the actual parameters as +VIDIOC_G_FMT does. Like +VIDIOC_S_FMT, the &VIDIOC-TRY-FMT; ioctl can be +used to learn about driver capabilities without actually changing +driver state. Unlike VIDIOC_S_FMT this also works +after the overlay has been enabled. + + A &v4l2-crop; defines the size and position of the target +rectangle. The scaling factor of the overlay is implied by the width +and height given in &v4l2-window; and &v4l2-crop;. The cropping API +applies to Video Output and Video +Output Overlay devices in the same way as to +Video Capture and Video +Overlay devices, merely reversing the direction of the +data flow. For more information see . +
+ +
+ Enabling Overlay + + There is no V4L2 ioctl to enable or disable the overlay, +however the framebuffer interface of the driver may support the +FBIOBLANK ioctl. +
+ + diff --git a/v4l2-spec/dev-output.sgml b/v4l2-spec/dev-output.sgml new file mode 100644 index 000000000..4cbc08b10 --- /dev/null +++ b/v4l2-spec/dev-output.sgml @@ -0,0 +1,111 @@ + Video Output Interface + + Video output devices encode stills or image sequences as +analog video signal. With this interface applications can +control the encoding process and move images from user space to +the driver. + + Conventionally V4L2 video output devices are accessed through +character device special files named /dev/video +and /dev/video0 to +/dev/video63 with major number 81 and minor +numbers 0 to 63. /dev/video is typically a +symbolic link to the preferred video device. Note the same device +files are used for video capture devices. + +
+ Querying Capabilities + + Devices supporting the video output interface set the +V4L2_CAP_VIDEO_OUTPUT flag in the +capabilities field of &v4l2-capability; +returned by the &VIDIOC-QUERYCAP; ioctl. As secondary device functions +they may also support the raw VBI +output (V4L2_CAP_VBI_OUTPUT) interface. At +least one of the read/write or streaming I/O methods must be +supported. Modulators and audio outputs are optional. +
+ +
+ Supplemental Functions + + Video output devices shall support audio output, modulator, controls, +cropping and scaling and streaming parameter ioctls as needed. +The video output and video standard ioctls must be supported by +all video output devices. +
+ +
+ Image Format Negotiation + + The output is determined by cropping and image format +parameters. The former select an area of the video picture where the +image will appear, the latter how images are stored in memory, &ie; in +RGB or YUV format, the number of bits per pixel or width and height. +Together they also define how images are scaled in the process. + + As usual these parameters are not reset +at &func-open; time to permit Unix tool chains, programming a device +and then writing to it as if it was a plain file. Well written V4L2 +applications ensure they really get what they want, including cropping +and scaling. + + Cropping initialization at minimum requires to reset the +parameters to defaults. An example is given in . + + To query the current image format applications set the +type field of a &v4l2-format; to +V4L2_BUF_TYPE_VIDEO_OUTPUT and call the +&VIDIOC-G-FMT; ioctl with a pointer to this structure. Drivers fill +the &v4l2-pix-format; pix member of the +fmt union. + + To request different parameters applications set the +type field of a &v4l2-format; as above and +initialize all fields of the &v4l2-pix-format; +vbi member of the +fmt union, or better just modify the +results of VIDIOC_G_FMT, and call the +&VIDIOC-S-FMT; ioctl with a pointer to this structure. Drivers may +adjust the parameters and finally return the actual parameters as +VIDIOC_G_FMT does. + + Like VIDIOC_S_FMT the +&VIDIOC-TRY-FMT; ioctl can be used to learn about hardware limitations +without disabling I/O or possibly time consuming hardware +preparations. + + The contents of &v4l2-pix-format; are discussed in . See also the specification of the +VIDIOC_G_FMT, VIDIOC_S_FMT +and VIDIOC_TRY_FMT ioctls for details. Video +output devices must implement both the +VIDIOC_G_FMT and +VIDIOC_S_FMT ioctl, even if +VIDIOC_S_FMT ignores all requests and always +returns default parameters as VIDIOC_G_FMT does. +VIDIOC_TRY_FMT is optional. +
+ +
+ Writing Images + + A video output device may support the write() function and/or streaming (memory mapping or user pointer) I/O. See for details. +
+ + diff --git a/v4l2-spec/dev-overlay.sgml b/v4l2-spec/dev-overlay.sgml new file mode 100644 index 000000000..0eadd1611 --- /dev/null +++ b/v4l2-spec/dev-overlay.sgml @@ -0,0 +1,373 @@ + Video Overlay Interface + Also known as Framebuffer Overlay or Previewing + + Video overlay devices have the ability to genlock (TV-)video +into the (VGA-)video signal of a graphics card, or to store captured +images directly in video memory of a graphics card, typically with +clipping. This can be considerable more efficient than capturing +images and displaying them by other means. In the old days when only +nuclear power plants needed cooling towers this used to be the only +way to put live video into a window. + + Video overlay devices are accessed through the same character +special files as video capture devices. +Note the default function of a /dev/video device +is video capturing. The overlay function is only available after +calling the &VIDIOC-S-FMT; ioctl. + + The driver may support simultaneous overlay and capturing +using the read/write and streaming I/O methods. If so, operation at +the nominal frame rate of the video standard is not guaranteed. Frames +may be directed away from overlay to capture, or one field may be used +for overlay and the other for capture if the capture parameters permit +this. + + Applications should use different file descriptors for +capturing and overlay. This must be supported by all drivers capable +of simultaneous capturing and overlay. Optionally these drivers may +also permit capturing and overlay with a single file descriptor for +compatibility with V4L and earlier versions of V4L2. + A common application of two file descriptors is the +XFree86 Xv/V4L interface driver and +a V4L2 application. While the X server controls video overlay, the +application can take advantage of memory mapping and DMA. + In the opinion of the designers of this API, no driver +writer taking the efforts to support simultaneous capturing and +overlay will restrict this ability by requiring a single file +descriptor, as in V4L and earlier versions of V4L2. Making this +optional means applications depending on two file descriptors need +backup routines to be compatible with all drivers, which is +considerable more work than using two fds in applications which do +not. Also two fd's fit the general concept of one file descriptor for +each logical stream. Hence as a complexity trade-off drivers +must support two file descriptors and +may support single fd operation. + + +
+ Querying Capabilities + + Devices supporting the video overlay interface set the +V4L2_CAP_VIDEO_OVERLAY flag in the +capabilities field of &v4l2-capability; +returned by the &VIDIOC-QUERYCAP; ioctl. The overlay I/O method specified +below must be supported. Tuners and audio inputs are optional. +
+ +
+ Supplemental Functions + + Video overlay devices shall support audio input, tuner, controls, +cropping and scaling and streaming parameter ioctls as needed. +The video input and video standard ioctls must be supported by +all video overlay devices. +
+ +
+ Setup + + Before overlay can commence applications must program the +driver with frame buffer parameters, namely the address and size of +the frame buffer and the image format, for example RGB 5:6:5. The +&VIDIOC-G-FBUF; and &VIDIOC-S-FBUF; ioctls are available to get +and set these parameters, respectively. The +VIDIOC_S_FBUF ioctl is privileged because it +allows to set up DMA into physical memory, bypassing the memory +protection mechanisms of the kernel. Only the superuser can change the +frame buffer address and size. Users are not supposed to run TV +applications as root or with SUID bit set. A small helper application +with suitable privileges should query the graphics system and program +the V4L2 driver at the appropriate time. + + Some devices add the video overlay to the output signal +of the graphics card. In this case the frame buffer is not modified by +the video device, and the frame buffer address and pixel format are +not needed by the driver. The VIDIOC_S_FBUF ioctl +is not privileged. An application can check for this type of device by +calling the VIDIOC_G_FBUF ioctl. + + A driver may support any (or none) of five clipping/blending +methods: + + Chroma-keying displays the overlaid image only where +pixels in the primary graphics surface assume a certain color. + + + A bitmap can be specified where each bit corresponds +to a pixel in the overlaid image. When the bit is set, the +corresponding video pixel is displayed, otherwise a pixel of the +graphics surface. + + + A list of clipping rectangles can be specified. In +these regions no video is displayed, so the +graphics surface can be seen here. + + + The framebuffer has an alpha channel that can be used +to clip or blend the framebuffer with the video. + + + A global alpha value can be specified to blend the +framebuffer contents with video images. + + + + When simultaneous capturing and overlay is supported and +the hardware prohibits different image and frame buffer formats, the +format requested first takes precedence. The attempt to capture +(&VIDIOC-S-FMT;) or overlay (&VIDIOC-S-FBUF;) may fail with an +&EBUSY; or return accordingly modified parameters.. +
+ +
+ Overlay Window + + The overlaid image is determined by cropping and overlay +window parameters. The former select an area of the video picture to +capture, the latter how images are overlaid and clipped. Cropping +initialization at minimum requires to reset the parameters to +defaults. An example is given in . + + The overlay window is described by a &v4l2-window;. It +defines the size of the image, its position over the graphics surface +and the clipping to be applied. To get the current parameters +applications set the type field of a +&v4l2-format; to V4L2_BUF_TYPE_VIDEO_OVERLAY and +call the &VIDIOC-G-FMT; ioctl. The driver fills the +v4l2_window substructure named +win. It is not possible to retrieve a +previously programmed clipping list or bitmap. + + To program the overlay window applications set the +type field of a &v4l2-format; to +V4L2_BUF_TYPE_VIDEO_OVERLAY, initialize the +win substructure and call the +&VIDIOC-S-FMT; ioctl. The driver adjusts the parameters against +hardware limits and returns the actual parameters as +VIDIOC_G_FMT does. Like +VIDIOC_S_FMT, the &VIDIOC-TRY-FMT; ioctl can be +used to learn about driver capabilities without actually changing +driver state. Unlike VIDIOC_S_FMT this also works +after the overlay has been enabled. + + The scaling factor of the overlaid image is implied by the +width and height given in &v4l2-window; and the size of the cropping +rectangle. For more information see . + + When simultaneous capturing and overlay is supported and +the hardware prohibits different image and window sizes, the size +requested first takes precedence. The attempt to capture or overlay as +well (&VIDIOC-S-FMT;) may fail with an &EBUSY; or return accordingly +modified parameters. + + + struct <structname>v4l2_window</structname> + + &cs-str; + + + &v4l2-rect; + w + Size and position of the window relative to the +top, left corner of the frame buffer defined with &VIDIOC-S-FBUF;. The +window can extend the frame buffer width and height, the +x and y +coordinates can be negative, and it can lie completely outside the +frame buffer. The driver clips the window accordingly, or if that is +not possible, modifies its size and/or position. + + + &v4l2-field; + field + Applications set this field to determine which +video field shall be overlaid, typically one of +V4L2_FIELD_ANY (0), +V4L2_FIELD_TOP, +V4L2_FIELD_BOTTOM or +V4L2_FIELD_INTERLACED. Drivers may have to choose +a different field order and return the actual setting here. + + + __u32 + chromakey + When chroma-keying has been negotiated with +&VIDIOC-S-FBUF; applications set this field to the desired pixel value +for the chroma key. The format is the same as the pixel format of the +framebuffer (&v4l2-framebuffer; +fmt.pixelformat field), with bytes in host +order. E. g. for V4L2_PIX_FMT_BGR24 +the value should be 0xRRGGBB on a little endian, 0xBBGGRR on a big +endian host. + + + &v4l2-clip; * + clips + When chroma-keying has not +been negotiated and &VIDIOC-G-FBUF; indicated this capability, +applications can set this field to point to an array of +clipping rectangles. + + + Like the window coordinates +w, clipping rectangles are defined relative +to the top, left corner of the frame buffer. However clipping +rectangles must not extend the frame buffer width and height, and they +must not overlap. If possible applications should merge adjacent +rectangles. Whether this must create x-y or y-x bands, or the order of +rectangles, is not defined. When clip lists are not supported the +driver ignores this field. Its contents after calling &VIDIOC-S-FMT; +are undefined. + + + __u32 + clipcount + When the application set the +clips field, this field must contain the +number of clipping rectangles in the list. When clip lists are not +supported the driver ignores this field, its contents after calling +VIDIOC_S_FMT are undefined. When clip lists are +supported but no clipping is desired this field must be set to +zero. + + + void * + bitmap + When chroma-keying has +not been negotiated and &VIDIOC-G-FBUF; indicated +this capability, applications can set this field to point to a +clipping bit mask. + + + It must be of the same size +as the window, w.width and +w.height. Each bit corresponds to a pixel +in the overlaid image, which is displayed only when the bit is +set. Pixel coordinates translate to bits like: + +((__u8 *) bitmap)[w.width * y + x / 8] & (1 << (x & 7))where 0 ≤ x < +w.width and 0 ≤ +y <w.height. + Should we require + w.width to be a multiple of + eight? + When a clipping +bit mask is not supported the driver ignores this field, its contents +after calling &VIDIOC-S-FMT; are undefined. When a bit mask is supported +but no clipping is desired this field must be set to +NULL.Applications need not create a +clip list or bit mask. When they pass both, or despite negotiating +chroma-keying, the results are undefined. Regardless of the chosen +method, the clipping abilities of the hardware may be limited in +quantity or quality. The results when these limits are exceeded are +undefined. + When the image is written into frame buffer +memory it will be undesirable if the driver clips out less pixels +than expected, because the application and graphics system are not +aware these regions need to be refreshed. The driver should clip out +more pixels or not write the image at all. + + + + __u8 + global_alpha + The global alpha value used to blend the +framebuffer with video images, if global alpha blending has been +negotiated (V4L2_FBUF_FLAG_GLOBAL_ALPHA, see +&VIDIOC-S-FBUF;, ).Note +this field was added in Linux 2.6.23, extending the structure. However +the VIDIOC_G/S/TRY_FMT ioctls, +which take a pointer to a v4l2_format parent structure with padding +bytes at the end, are not affected. + + + +
+ + + struct <structname>v4l2_clip</structname><footnote> + <para>The X Window system defines "regions" which are +vectors of struct BoxRec { short x1, y1, x2, y2; } with width = x2 - +x1 and height = y2 - y1, so one cannot pass X11 clip lists +directly.</para> + </footnote> + + &cs-str; + + + &v4l2-rect; + c + Coordinates of the clipping rectangle, relative to +the top, left corner of the frame buffer. Only window pixels +outside all clipping rectangles are +displayed. + + + &v4l2-clip; * + next + Pointer to the next clipping rectangle, NULL when +this is the last rectangle. Drivers ignore this field, it cannot be +used to pass a linked list of clipping rectangles. + + + +
+ + + + + struct <structname>v4l2_rect</structname> + + &cs-str; + + + __s32 + left + Horizontal offset of the top, left corner of the +rectangle, in pixels. + + + __s32 + top + Vertical offset of the top, left corner of the +rectangle, in pixels. Offsets increase to the right and down. + + + __s32 + width + Width of the rectangle, in pixels. + + + __s32 + height + Height of the rectangle, in pixels. Width and +height cannot be negative, the fields are signed for hysterical +reasons. + + + +
+
+ +
+ Enabling Overlay + + To start or stop the frame buffer overlay applications call +the &VIDIOC-OVERLAY; ioctl. +
+ + diff --git a/v4l2-spec/dev-radio.sgml b/v4l2-spec/dev-radio.sgml new file mode 100644 index 000000000..ae8367219 --- /dev/null +++ b/v4l2-spec/dev-radio.sgml @@ -0,0 +1,55 @@ + Radio Interface + + This interface is intended for AM and FM (analog) radio +receivers. + + Conventionally V4L2 radio devices are accessed through +character device special files named /dev/radio +and /dev/radio0 to +/dev/radio63 with major number 81 and minor +numbers 64 to 127. + +
+ Querying Capabilities + + Devices supporting the radio interface set the +V4L2_CAP_RADIO and +V4L2_CAP_TUNER flag in the +capabilities field of &v4l2-capability; +returned by the &VIDIOC-QUERYCAP; ioctl. Other combinations of +capability flags are reserved for future extensions. +
+ +
+ Supplemental Functions + + Radio devices can support controls, and must support the tuner ioctls. + + They do not support the video input or output, audio input +or output, video standard, cropping and scaling, compression and +streaming parameter, or overlay ioctls. All other ioctls and I/O +methods are reserved for future extensions. +
+ +
+ Programming + + Radio devices may have a couple audio controls (as discussed +in ) such as a volume control, possibly custom +controls. Further all radio devices have one tuner (these are +discussed in ) with index number zero to select +the radio frequency and to determine if a monaural or FM stereo +program is received. Drivers switch automatically between AM and FM +depending on the selected frequency. The &VIDIOC-G-TUNER; ioctl +reports the supported frequency range. +
+ + diff --git a/v4l2-spec/dev-raw-vbi.sgml b/v4l2-spec/dev-raw-vbi.sgml new file mode 100644 index 000000000..39d814c44 --- /dev/null +++ b/v4l2-spec/dev-raw-vbi.sgml @@ -0,0 +1,347 @@ + Raw VBI Data Interface + + VBI is an abbreviation of Vertical Blanking Interval, a gap +in the sequence of lines of an analog video signal. During VBI +no picture information is transmitted, allowing some time while the +electron beam of a cathode ray tube TV returns to the top of the +screen. Using an oscilloscope you will find here the vertical +synchronization pulses and short data packages ASK +modulatedASK: Amplitude-Shift Keying. A high signal +level represents a '1' bit, a low level a '0' bit. +onto the video signal. These are transmissions of services such as +Teletext or Closed Caption. + + Subject of this interface type is raw VBI data, as sampled off +a video signal, or to be added to a signal for output. +The data format is similar to uncompressed video images, a number of +lines times a number of samples per line, we call this a VBI image. + + Conventionally V4L2 VBI devices are accessed through character +device special files named /dev/vbi and +/dev/vbi0 to /dev/vbi31 with +major number 81 and minor numbers 224 to 255. +/dev/vbi is typically a symbolic link to the +preferred VBI device. This convention applies to both input and output +devices. + + To address the problems of finding related video and VBI +devices VBI capturing and output is also available as device function +under /dev/video. To capture or output raw VBI +data with these devices applications must call the &VIDIOC-S-FMT; +ioctl. Accessed as /dev/vbi, raw VBI capturing +or output is the default device function. + +
+ Querying Capabilities + + Devices supporting the raw VBI capturing or output API set +the V4L2_CAP_VBI_CAPTURE or +V4L2_CAP_VBI_OUTPUT flags, respectively, in the +capabilities field of &v4l2-capability; +returned by the &VIDIOC-QUERYCAP; ioctl. At least one of the +read/write, streaming or asynchronous I/O methods must be +supported. VBI devices may or may not have a tuner or modulator. +
+ +
+ Supplemental Functions + + VBI devices shall support video +input or output, tuner or +modulator, and controls ioctls +as needed. The video standard ioctls provide +information vital to program a VBI device, therefore must be +supported. +
+ +
+ Raw VBI Format Negotiation + + Raw VBI sampling abilities can vary, in particular the +sampling frequency. To properly interpret the data V4L2 specifies an +ioctl to query the sampling parameters. Moreover, to allow for some +flexibility applications can also suggest different parameters. + + As usual these parameters are not +reset at &func-open; time to permit Unix tool chains, programming a +device and then reading from it as if it was a plain file. Well +written V4L2 applications should always ensure they really get what +they want, requesting reasonable parameters and then checking if the +actual parameters are suitable. + + To query the current raw VBI capture parameters +applications set the type field of a +&v4l2-format; to V4L2_BUF_TYPE_VBI_CAPTURE or +V4L2_BUF_TYPE_VBI_OUTPUT, and call the +&VIDIOC-G-FMT; ioctl with a pointer to this structure. Drivers fill +the &v4l2-vbi-format; vbi member of the +fmt union. + + To request different parameters applications set the +type field of a &v4l2-format; as above and +initialize all fields of the &v4l2-vbi-format; +vbi member of the +fmt union, or better just modify the +results of VIDIOC_G_FMT, and call the +&VIDIOC-S-FMT; ioctl with a pointer to this structure. Drivers return +an &EINVAL; only when the given parameters are ambiguous, otherwise +they modify the parameters according to the hardware capabilites and +return the actual parameters. When the driver allocates resources at +this point, it may return an &EBUSY; to indicate the returned +parameters are valid but the required resources are currently not +available. That may happen for instance when the video and VBI areas +to capture would overlap, or when the driver supports multiple opens +and another process already requested VBI capturing or output. Anyway, +applications must expect other resource allocation points which may +return EBUSY, at the &VIDIOC-STREAMON; ioctl +and the first read(), write() and select() call. + + VBI devices must implement both the +VIDIOC_G_FMT and +VIDIOC_S_FMT ioctl, even if +VIDIOC_S_FMT ignores all requests and always +returns default parameters as VIDIOC_G_FMT does. +VIDIOC_TRY_FMT is optional. + + + struct <structname>v4l2_vbi_format</structname> + + &cs-str; + + + __u32 + sampling_rate + Samples per second, i. e. unit 1 Hz. + + + __u32 + offset + Horizontal offset of the VBI image, +relative to the leading edge of the line synchronization pulse and +counted in samples: The first sample in the VBI image will be located +offset / +sampling_rate seconds following the leading +edge. See also . + + + __u32 + samples_per_line + + + + __u32 + sample_format + Defines the sample format as in , a four-character-code. + A few devices may be unable to +sample VBI data at all but can extend the video capture window to the +VBI region. + Usually this is +V4L2_PIX_FMT_GREY, i. e. each sample +consists of 8 bits with lower values oriented towards the black level. +Do not assume any other correlation of values with the signal level. +For example, the MSB does not necessarily indicate if the signal is +'high' or 'low' because 128 may not be the mean value of the +signal. Drivers shall not convert the sample format by software. + + + __u32 + start[2] + This is the scanning system line number +associated with the first line of the VBI image, of the first and the +second field respectively. See and + for valid values. VBI input drivers can +return start values 0 if the hardware cannot reliable identify +scanning lines, VBI acquisition may not require this +information. + + + __u32 + count[2] + The number of lines in the first and second +field image, respectively. + + + Drivers should be as +flexibility as possible. For example, it may be possible to extend or +move the VBI capture window down to the picture area, implementing a +'full field mode' to capture data service transmissions embedded in +the picture.An application can set the first or second +count value to zero if no data is required +from the respective field; count[1] if the +scanning system is progressive, &ie; not interlaced. The +corresponding start value shall be ignored by the application and +driver. Anyway, drivers may not support single field capturing and +return both count values non-zero.Both +count values set to zero, or line numbers +outside the bounds depicted in and , or a field image covering +lines of two fields, are invalid and shall not be returned by the +driver.To initialize the start +and count fields, applications must first +determine the current video standard selection. The &v4l2-std-id; or +the framelines field of &v4l2-standard; can +be evaluated for this purpose. + + + __u32 + flags + See below. Currently +only drivers set flags, applications must set this field to +zero. + + + __u32 + reserved[2] + This array is reserved for future extensions. +Drivers and applications must set it to zero. + + + +
+ + + Raw VBI Format Flags + + &cs-def; + + + V4L2_VBI_UNSYNC + 0x0001 + This flag indicates hardware which does not +properly distinguish between fields. Normally the VBI image stores the +first field (lower scanning line numbers) first in memory. This may be +a top or bottom field depending on the video standard. When this flag +is set the first or second field may be stored first, however the +fields are still in correct temporal order with the older field first +in memory. + Most VBI services transmit on both fields, but +some have different semantics depending on the field number. These +cannot be reliable decoded or encoded when +V4L2_VBI_UNSYNC is set. + + + + V4L2_VBI_INTERLACED + 0x0002 + By default the two field images will be passed +sequentially; all lines of the first field followed by all lines of +the second field (compare +V4L2_FIELD_SEQ_TB and +V4L2_FIELD_SEQ_BT, whether the top or bottom +field is first in memory depends on the video standard). When this +flag is set, the two fields are interlaced (cf. +V4L2_FIELD_INTERLACED). The first line of the +first field followed by the first line of the second field, then the +two second lines, and so on. Such a layout may be necessary when the +hardware has been programmed to capture or output interlaced video +images and is unable to separate the fields for VBI capturing at +the same time. For simplicity setting this flag implies that both +count values are equal and non-zero. + + + +
+ +
+ Line synchronization + + + + + + + + + Line synchronization diagram + + +
+ +
+ ITU-R 525 line numbering (M/NTSC and M/PAL) + + + + + + + + + NTSC field synchronization diagram + + + (1) For the purpose of this specification field 2 +starts in line 264 and not 263.5 because half line capturing is not +supported. + + +
+ +
+ ITU-R 625 line numbering + + + + + + + + + PAL/SECAM field synchronization diagram + + + (1) For the purpose of this specification field 2 +starts in line 314 and not 313.5 because half line capturing is not +supported. + + +
+ + Remember the VBI image format depends on the selected +video standard, therefore the application must choose a new standard or +query the current standard first. Attempts to read or write data ahead +of format negotiation, or after switching the video standard which may +invalidate the negotiated VBI parameters, should be refused by the +driver. A format change during active I/O is not permitted. +
+ +
+ Reading and writing VBI images + + To assure synchronization with the field number and easier +implementation, the smallest unit of data passed at a time is one +frame, consisting of two fields of VBI images immediately following in +memory. + + The total size of a frame computes as follows: + + +(count[0] + count[1]) * +samples_per_line * sample size in bytes + + The sample size is most likely always one byte, +applications must check the sample_format +field though, to function properly with other drivers. + + A VBI device may support read/write and/or streaming (memory mapping or user pointer) I/O. The latter bears the +possibility of synchronizing video and +VBI data by using buffer timestamps. + + Remember the &VIDIOC-STREAMON; ioctl and the first read(), +write() and select() call can be resource allocation points returning +an &EBUSY; if the required hardware resources are temporarily +unavailable, for example the device is already in use by another +process. +
+ + diff --git a/v4l2-spec/dev-rds.sgml b/v4l2-spec/dev-rds.sgml new file mode 100644 index 000000000..f63120682 --- /dev/null +++ b/v4l2-spec/dev-rds.sgml @@ -0,0 +1,44 @@ + RDS Interface + + The Radio Data System transmits supplementary +information in binary format, for example the station name or travel +information, on a inaudible audio subcarrier of a radio program. This +interface aims at devices capable of receiving and decoding RDS +information. + + The V4L API defines its RDS API as follows. + + From radio devices supporting it, RDS data can be read +with the &func-read; function. The data is packed in groups of three, +as follows: + + First Octet Least Significant Byte of RDS Block + + + Second Octet Most Significant Byte of RDS Block + + + Third Octet Bit 7: Error bit. Indicates that an +uncorrectable error occurred during reception of this block. Bit 6: +Corrected bit. Indicates that an error was corrected for this data +block. Bits 5-3: Received Offset. Indicates the offset received by the +sync system. Bits 2-0: Offset Name. Indicates the offset applied to +this data. + + + + It was argued the RDS API should be +extended before integration into V4L2, no new API has been devised yet. +Please write to the Video4Linux mailing list for discussion: &v4l-ml;. +Meanwhile no V4L2 driver should set the +V4L2_CAP_RDS_CAPTURE capability flag. + + + diff --git a/v4l2-spec/dev-sliced-vbi.sgml b/v4l2-spec/dev-sliced-vbi.sgml new file mode 100644 index 000000000..42f6f6938 --- /dev/null +++ b/v4l2-spec/dev-sliced-vbi.sgml @@ -0,0 +1,396 @@ + Sliced VBI Data Interface + + VBI stands for Vertical Blanking Interval, a gap in the +sequence of lines of an analog video signal. During VBI no picture +information is transmitted, allowing some time while the electron beam +of a cathode ray tube TV returns to the top of the screen. + + Sliced VBI devices use hardware to demodulate data transmitted +in the VBI. V4L2 drivers shall not do this by +software, see also the raw VBI +interface. The data is passed as short packets of fixed size, +covering one scan line each. The number of packets per video frame is +variable. + + Sliced VBI capture and output devices are accessed through the +same character special files as raw VBI devices. When a driver +supports both interfaces, the default function of a +/dev/vbi device is raw VBI +capturing or output, and the sliced VBI function is only available +after calling the &VIDIOC-S-FMT; ioctl as defined below. Likewise a +/dev/video device may support the sliced VBI API, +however the default function here is video capturing or output. +Different file descriptors must be used to pass raw and sliced VBI +data simultaneously, if this is supported by the driver. + +
+ Querying Capabilities + + Devices supporting the sliced VBI capturing or output API +set the V4L2_CAP_SLICED_VBI_CAPTURE or +V4L2_CAP_SLICED_VBI_OUTPUT flag respectively, in +the capabilities field of &v4l2-capability; +returned by the &VIDIOC-QUERYCAP; ioctl. At least one of the +read/write, streaming or asynchronous I/O +methods must be supported. Sliced VBI devices may have a tuner +or modulator. +
+ +
+ Supplemental Functions + + Sliced VBI devices shall support video +input or output and tuner or +modulator ioctls if they have these capabilities, and they may +support control ioctls. The video standard ioctls provide information +vital to program a sliced VBI device, therefore must be +supported. +
+ +
+ Sliced VBI Format Negotiation + + To find out which data services are supported by the +hardware applications can call the &VIDIOC-G-SLICED-VBI-CAP; ioctl. +All drivers implementing the sliced VBI interface must support this +ioctl. The results may differ from those of the &VIDIOC-S-FMT; ioctl +when the number of VBI lines the hardware can capture or output per +frame, or the number of services it can identify on a given line are +limited. For example on PAL line 16 the hardware may be able to look +for a VPS or Teletext signal, but not both at the same time. + + To determine the currently selected services applications +set the type field of &v4l2-format; to + V4L2_BUF_TYPE_SLICED_VBI_CAPTURE or +V4L2_BUF_TYPE_SLICED_VBI_OUTPUT, and the &VIDIOC-G-FMT; +ioctl fills the fmt.sliced member, a +&v4l2-sliced-vbi-format;. + + Applications can request different parameters by +initializing or modifying the fmt.sliced +member and calling the &VIDIOC-S-FMT; ioctl with a pointer to the +v4l2_format structure. + + The sliced VBI API is more complicated than the raw VBI API +because the hardware must be told which VBI service to expect on each +scan line. Not all services may be supported by the hardware on all +lines (this is especially true for VBI output where Teletext is often +unsupported and other services can only be inserted in one specific +line). In many cases, however, it is sufficient to just set the +service_set field to the required services +and let the driver fill the service_lines +array according to hardware capabilities. Only if more precise control +is needed should the programmer set the +service_lines array explicitly. + + The &VIDIOC-S-FMT; ioctl returns an &EINVAL; only when the +given parameters are ambiguous, otherwise it modifies the parameters +according to hardware capabilities. When the driver allocates +resources at this point, it may return an &EBUSY; if the required +resources are temporarily unavailable. Other resource allocation +points which may return EBUSY can be the +&VIDIOC-STREAMON; ioctl and the first &func-read;, &func-write; and +&func-select; call. + + + struct +<structname>v4l2_sliced_vbi_format</structname> + + + + + + + + + + __u32 + service_set + If +service_set is non-zero when passed with +&VIDIOC-S-FMT; or &VIDIOC-TRY-FMT;, the +service_lines array will be filled by the +driver according to the services specified in this field. For example, +if service_set is initialized with +V4L2_SLICED_TELETEXT_B | V4L2_SLICED_WSS_625, a +driver for the cx25840 video decoder sets lines 7-22 of both +fieldsAccording to ETS 300 706 lines 6-22 of the +first field and lines 5-22 of the second field may carry Teletext +data. to V4L2_SLICED_TELETEXT_B +and line 23 of the first field to +V4L2_SLICED_WSS_625. If +service_set is set to zero, then the values +of service_lines will be used instead. +On return the driver sets this field to the union of all +elements of the returned service_lines +array. It may contain less services than requested, perhaps just one, +if the hardware cannot handle more services simultaneously. It may be +empty (zero) if none of the requested services are supported by the +hardware. + + + __u16 + service_lines[2][24] + Applications initialize this +array with sets of data services the driver shall look for or insert +on the respective scan line. Subject to hardware capabilities drivers +return the requested set, a subset, which may be just a single +service, or an empty set. When the hardware cannot handle multiple +services on the same line the driver shall choose one. No assumptions +can be made on which service the driver chooses.Data +services are defined in . Array indices +map to ITU-R line numbers (see also and ) as follows: + + + + + Element + 525 line systems + 625 line systems + + + + + service_lines[0][1] + 1 + 1 + + + + + service_lines[0][23] + 23 + 23 + + + + + service_lines[1][1] + 264 + 314 + + + + + service_lines[1][23] + 286 + 336 + + + + + + Drivers must set +service_lines[0][0] and +service_lines[1][0] to zero. + + + __u32 + io_size + Maximum number of bytes passed by +one &func-read; or &func-write; call, and the buffer size in bytes for +the &VIDIOC-QBUF; and &VIDIOC-DQBUF; ioctl. Drivers set this field to +the size of &v4l2-sliced-vbi-data; times the number of non-zero +elements in the returned service_lines +array (that is the number of lines potentially carrying data). + + + __u32 + reserved[2] + This array is reserved for future +extensions. Applications and drivers must set it to zero. + + + +
+ + + + Sliced VBI services + + + + + + + + + + Symbol + Value + Reference + Lines, usually + Payload + + + + + V4L2_SLICED_TELETEXT_B +(Teletext System B) + 0x0001 + , + PAL/SECAM line 7-22, 320-335 (second field 7-22) + Last 42 of the 45 byte Teletext packet, that is +without clock run-in and framing code, lsb first transmitted. + + + V4L2_SLICED_VPS + 0x0400 + + PAL line 16 + Byte number 3 to 15 according to Figure 9 of +ETS 300 231, lsb first transmitted. + + + V4L2_SLICED_CAPTION_525 + 0x1000 + + NTSC line 21, 284 (second field 21) + Two bytes in transmission order, including parity +bit, lsb first transmitted. + + + V4L2_SLICED_WSS_625 + 0x4000 + , + PAL/SECAM line 23 + +Byte 0 1 + msb lsb msb lsb + Bit 7 6 5 4 3 2 1 0 x x 13 12 11 10 9 + + + + V4L2_SLICED_VBI_525 + 0x1000 + Set of services applicable to 525 +line systems. + + + V4L2_SLICED_VBI_625 + 0x4401 + Set of services applicable to 625 +line systems. + + + +
+ + Drivers may return an &EINVAL; when applications attempt to +read or write data without prior format negotiation, after switching +the video standard (which may invalidate the negotiated VBI +parameters) and after switching the video input (which may change the +video standard as a side effect). The &VIDIOC-S-FMT; ioctl may return +an &EBUSY; when applications attempt to change the format while i/o is +in progress (between a &VIDIOC-STREAMON; and &VIDIOC-STREAMOFF; call, +and after the first &func-read; or &func-write; call). +
+ +
+ Reading and writing sliced VBI data + + A single &func-read; or &func-write; call must pass all data +belonging to one video frame. That is an array of +v4l2_sliced_vbi_data structures with one or +more elements and a total size not exceeding +io_size bytes. Likewise in streaming I/O +mode one buffer of io_size bytes must +contain data of one video frame. The id of +unused v4l2_sliced_vbi_data elements must be +zero. + + + struct +<structname>v4l2_sliced_vbi_data</structname> + + &cs-def; + + + __u32 + id + A flag from +identifying the type of data in this packet. Only a single bit must be +set. When the id of a captured packet is +zero, the packet is empty and the contents of other fields are +undefined. Applications shall ignore empty packets. When the +id of a packet for output is zero the +contents of the data field are undefined +and the driver must no longer insert data on the requested +field and +line. + + + __u32 + field + The video field number this data has been captured +from, or shall be inserted at. 0 for the first +field, 1 for the second field. + + + __u32 + line + The field (as opposed to frame) line number this +data has been captured from, or shall be inserted at. See and for valid +values. Sliced VBI capture devices can set the line number of all +packets to 0 if the hardware cannot reliably +identify scan lines. The field number must always be valid. + + + __u32 + reserved + This field is reserved for future extensions. +Applications and drivers must set it to zero. + + + __u8 + data[48] + The packet payload. See for the contents and number of +bytes passed for each data type. The contents of padding bytes at the +end of this array are undefined, drivers and applications shall ignore +them. + + + +
+ + Packets are always passed in ascending line number order, +without duplicate line numbers. The &func-write; function and the +&VIDIOC-QBUF; ioctl must return an &EINVAL; when applications violate +this rule. They must also return an &EINVAL; when applications pass an +incorrect field or line number, or a combination of +field, line and +id which has not been negotiated with the +&VIDIOC-G-FMT; or &VIDIOC-S-FMT; ioctl. When the line numbers are +unknown the driver must pass the packets in transmitted order. The +driver can insert empty packets with id set +to zero anywhere in the packet array. + + To assure synchronization and to distinguish from frame +dropping, when a captured frame does not carry any of the requested +data services drivers must pass one or more empty packets. When an +application fails to pass VBI data in time for output, the driver +must output the last VPS and WSS packet again, and disable the output +of Closed Caption and Teletext data, or output data which is ignored +by Closed Caption and Teletext decoders. + + A sliced VBI device may support read/write and/or streaming (memory mapping and/or user +pointer) I/O. The latter bears the possibility of synchronizing +video and VBI data by using buffer timestamps. + +
+ + diff --git a/v4l2-spec/dev-teletext.sgml b/v4l2-spec/dev-teletext.sgml new file mode 100644 index 000000000..6c44650ba --- /dev/null +++ b/v4l2-spec/dev-teletext.sgml @@ -0,0 +1,40 @@ + Teletext Interface + + This interface aims at devices receiving and demodulating +Teletext data [, ], evaluating the +Teletext packages and storing formatted pages in cache memory. Such +devices are usually implemented as microcontrollers with serial +interface (I2C) and can be found on older +TV cards, dedicated Teletext decoding cards and home-brew devices +connected to the PC parallel port. + + The Teletext API was designed by Martin Buck. It is defined in +the kernel header file linux/videotext.h, the +specification is available from +http://home.pages.de/~videotext/. (Videotext is the name of +the German public television Teletext service.) Conventional character +device file names are /dev/vtx and +/dev/vttuner, with device number 83, 0 and 83, 16 +respectively. A similar interface exists for the Philips SAA5249 +Teletext decoder [specification?] with character device file names +/dev/tlkN, device number 102, N. + + Eventually the Teletext API was integrated into the V4L API +with character device file names /dev/vtx0 to +/dev/vtx31, device major number 81, minor numbers +192 to 223. For reference the V4L Teletext API specification is +reproduced here in full: "Teletext interfaces talk the existing VTX +API." Teletext devices with major number 83 and 102 will be removed in +Linux 2.6. + + There are no plans to replace the Teletext API or to integrate +it into V4L2. Please write to the Video4Linux mailing list: &v4l-ml; +when the need arises. + + diff --git a/v4l2-spec/driver.sgml b/v4l2-spec/driver.sgml new file mode 100644 index 000000000..1f7eea5c4 --- /dev/null +++ b/v4l2-spec/driver.sgml @@ -0,0 +1,208 @@ + V4L2 Driver Programming + + + + to do + + + diff --git a/v4l2-spec/fdl-appendix.sgml b/v4l2-spec/fdl-appendix.sgml new file mode 100644 index 000000000..f21019ae4 --- /dev/null +++ b/v4l2-spec/fdl-appendix.sgml @@ -0,0 +1,671 @@ + + + + + + Version 1.1, March 2000 + + + 2000Free Software Foundation, Inc. + + + +
Free Software Foundation, Inc. 59 Temple Place, + Suite 330, Boston, MA + 02111-1307 USA
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If you have no + Front-Cover Texts, write + no Front-Cover Texts instead of + Front-Cover Texts being LIST; likewise for Back-Cover Texts. + + + + If your document contains nontrivial examples of program code, + we recommend releasing these examples in parallel under your + choice of free software license, such as the GNU General Public + License, to permit their use in free software. + + + + + + + + + diff --git a/v4l2-spec/fieldseq_bt.gif b/v4l2-spec/fieldseq_bt.gif new file mode 100644 index 000000000..60e8569a7 Binary files /dev/null and b/v4l2-spec/fieldseq_bt.gif differ diff --git a/v4l2-spec/fieldseq_bt.pdf b/v4l2-spec/fieldseq_bt.pdf new file mode 100644 index 000000000..26598b23f Binary files /dev/null and b/v4l2-spec/fieldseq_bt.pdf differ diff --git a/v4l2-spec/fieldseq_tb.gif b/v4l2-spec/fieldseq_tb.gif new file mode 100644 index 000000000..718492f1c Binary files /dev/null and b/v4l2-spec/fieldseq_tb.gif differ diff --git a/v4l2-spec/fieldseq_tb.pdf b/v4l2-spec/fieldseq_tb.pdf new file mode 100644 index 000000000..4965b22dd Binary files /dev/null and b/v4l2-spec/fieldseq_tb.pdf differ diff --git a/v4l2-spec/func-close.sgml b/v4l2-spec/func-close.sgml new file mode 100644 index 000000000..dfb41cbbb --- /dev/null +++ b/v4l2-spec/func-close.sgml @@ -0,0 +1,70 @@ + + + V4L2 close() + &manvol; + + + + v4l2-close + Close a V4L2 device + + + + + #include <unistd.h> + + int close + int fd + + + + + + Arguments + + + + fd + + &fd; + + + + + + + Description + + Closes the device. Any I/O in progress is terminated and +resources associated with the file descriptor are freed. However data +format parameters, current input or output, control values or other +properties remain unchanged. + + + + Return Value + + The function returns 0 on +success, -1 on failure and the +errno is set appropriately. Possible error +codes: + + + + EBADF + + fd is not a valid open file +descriptor. + + + + + + + diff --git a/v4l2-spec/func-ioctl.sgml b/v4l2-spec/func-ioctl.sgml new file mode 100644 index 000000000..96dead0ec --- /dev/null +++ b/v4l2-spec/func-ioctl.sgml @@ -0,0 +1,146 @@ + + + V4L2 ioctl() + &manvol; + + + + v4l2-ioctl + Program a V4L2 device + + + + + #include <sys/ioctl.h> + + int ioctl + int fd + int request + void *argp + + + + + + Arguments + + + + fd + + &fd; + + + + request + + V4L2 ioctl request code as defined in the videodev.h header file, for example +VIDIOC_QUERYCAP. + + + + argp + + Pointer to a function parameter, usually a structure. + + + + + + + Description + + The ioctl() function is used to program +V4L2 devices. The argument fd must be an open +file descriptor. An ioctl request has encoded +in it whether the argument is an input, output or read/write +parameter, and the size of the argument argp in +bytes. Macros and defines specifying V4L2 ioctl requests are located +in the videodev.h header file. +Applications should use their own copy, not include the version in the +kernel sources on the system they compile on. All V4L2 ioctl requests, +their respective function and parameters are specified in . + + + + Return Value + + On success the ioctl() function returns +0 and does not reset the +errno variable. On failure +-1 is returned, when the ioctl takes an +output or read/write parameter it remains unmodified, and the +errno variable is set appropriately. See below for +possible error codes. Generic errors like EBADF +or EFAULT are not listed in the sections +discussing individual ioctl requests. + Note ioctls may return undefined error codes. Since errors +may have side effects such as a driver reset applications should +abort on unexpected errors. + + + + EBADF + + fd is not a valid open file +descriptor. + + + + EBUSY + + The property cannot be changed right now. Typically +this error code is returned when I/O is in progress or the driver +supports multiple opens and another process locked the property. + + + + EFAULT + + argp references an inaccessible +memory area. + + + + ENOTTY + + fd is not associated with a +character special device. + + + + EINVAL + + The request or the data pointed +to by argp is not valid. This is a very common +error code, see the individual ioctl requests listed in for actual causes. + + + + ENOMEM + + Not enough physical or virtual memory was available to +complete the request. + + + + ERANGE + + The application attempted to set a control with the +&VIDIOC-S-CTRL; ioctl to a value which is out of bounds. + + + + + + + diff --git a/v4l2-spec/func-mmap.sgml b/v4l2-spec/func-mmap.sgml new file mode 100644 index 000000000..2e2fc3933 --- /dev/null +++ b/v4l2-spec/func-mmap.sgml @@ -0,0 +1,185 @@ + + + V4L2 mmap() + &manvol; + + + + v4l2-mmap + Map device memory into application address space + + + + + +#include <unistd.h> +#include <sys/mman.h> + + void *mmap + void *start + size_t length + int prot + int flags + int fd + off_t offset + + + + + + Arguments + + + start + + Map the buffer to this address in the +application's address space. When the MAP_FIXED +flag is specified, start must be a multiple of the +pagesize and mmap will fail when the specified address +cannot be used. Use of this option is discouraged; applications should +just specify a NULL pointer here. + + + + length + + Length of the memory area to map. This must be the +same value as returned by the driver in the &v4l2-buffer; +length field. + + + + prot + + The prot argument describes the +desired memory protection. Regardless of the device type and the +direction of data exchange it should be set to +PROT_READ | PROT_WRITE, +permitting read and write access to image buffers. Drivers should +support at least this combination of flags. Note the Linux +video-buf kernel module, which is used by the +bttv, saa7134, saa7146, cx88 and vivi driver supports only +PROT_READ | PROT_WRITE. When +the driver does not support the desired protection the +mmap() function fails. + Note device memory accesses (⪚ the memory on a +graphics card with video capturing hardware) may incur a performance +penalty compared to main memory accesses, or reads may be +significantly slower than writes or vice versa. Other I/O methods may +be more efficient in this case. + + + + flags + + The flags parameter +specifies the type of the mapped object, mapping options and whether +modifications made to the mapped copy of the page are private to the +process or are to be shared with other references. + MAP_FIXED requests that the +driver selects no other address than the one specified. If the +specified address cannot be used, mmap() will fail. If +MAP_FIXED is specified, +start must be a multiple of the pagesize. Use +of this option is discouraged. + One of the MAP_SHARED or +MAP_PRIVATE flags must be set. +MAP_SHARED allows applications to share the +mapped memory with other (⪚ child-) processes. Note the Linux +video-buf module which is used by the bttv, +saa7134, saa7146, cx88 and vivi driver supports only +MAP_SHARED. MAP_PRIVATE +requests copy-on-write semantics. V4L2 applications should not set the +MAP_PRIVATE, MAP_DENYWRITE, +MAP_EXECUTABLE or MAP_ANON +flag. + + + + fd + + &fd; + + + + offset + + Offset of the buffer in device memory. This must be the +same value as returned by the driver in the &v4l2-buffer; +m union offset field. + + + + + + + Description + + The mmap() function asks to map +length bytes starting at +offset in the memory of the device specified by +fd into the application address space, +preferably at address start. This latter +address is a hint only, and is usually specified as 0. + + Suitable length and offset parameters are queried with the +&VIDIOC-QUERYBUF; ioctl. Buffers must be allocated with the +&VIDIOC-REQBUFS; ioctl before they can be queried. + + To unmap buffers the &func-munmap; function is used. + + + + Return Value + + On success mmap() returns a pointer to +the mapped buffer. On error MAP_FAILED (-1) is +returned, and the errno variable is set +appropriately. Possible error codes are: + + + + EBADF + + fd is not a valid file +descriptor. + + + + EACCES + + fd is +not open for reading and writing. + + + + EINVAL + + The start or +length or offset are not +suitable. (E. g. they are too large, or not aligned on a +PAGESIZE boundary.) + The flags or +prot value is not supported. + No buffers have been allocated with the +&VIDIOC-REQBUFS; ioctl. + + + + ENOMEM + + Not enough physical or virtual memory was available to +complete the request. + + + + + + + diff --git a/v4l2-spec/func-munmap.sgml b/v4l2-spec/func-munmap.sgml new file mode 100644 index 000000000..502ed4932 --- /dev/null +++ b/v4l2-spec/func-munmap.sgml @@ -0,0 +1,83 @@ + + + V4L2 munmap() + &manvol; + + + + v4l2-munmap + Unmap device memory + + + + + +#include <unistd.h> +#include <sys/mman.h> + + int munmap + void *start + size_t length + + + + + Arguments + + + start + + Address of the mapped buffer as returned by the +&func-mmap; function. + + + + length + + Length of the mapped buffer. This must be the same +value as given to mmap() and returned by the +driver in the &v4l2-buffer; length +field. + + + + + + + Description + + Unmaps a previously with the &func-mmap; function mapped +buffer and frees it, if possible. + + + + Return Value + + On success munmap() returns 0, on +failure -1 and the errno variable is set +appropriately: + + + + EINVAL + + The start or +length is incorrect, or no buffers have been +mapped yet. + + + + + + + diff --git a/v4l2-spec/func-open.sgml b/v4l2-spec/func-open.sgml new file mode 100644 index 000000000..7595d07a8 --- /dev/null +++ b/v4l2-spec/func-open.sgml @@ -0,0 +1,121 @@ + + + V4L2 open() + &manvol; + + + + v4l2-open + Open a V4L2 device + + + + + #include <fcntl.h> + + int open + const char *device_name + int flags + + + + + + Arguments + + + + device_name + + Device to be opened. + + + + flags + + Open flags. Access mode must be +O_RDWR. This is just a technicality, input devices +still support only reading and output devices only writing. + When the O_NONBLOCK flag is +given, the read() function and the &VIDIOC-DQBUF; ioctl will return +the &EAGAIN; when no data is available or no buffer is in the driver +outgoing queue, otherwise these functions block until data becomes +available. All V4L2 drivers exchanging data with applications must +support the O_NONBLOCK flag. + Other flags have no effect. + + + + + + Description + + To open a V4L2 device applications call +open() with the desired device name. This +function has no side effects; all data format parameters, current +input or output, control values or other properties remain unchanged. +At the first open() call after loading the driver +they will be reset to default values, drivers are never in an +undefined state. + + + Return Value + + On success open returns the new file +descriptor. On error -1 is returned, and the errno +variable is set appropriately. Possible error codes are: + + + + EACCES + + The caller has no permission to access the +device. + + + + EBUSY + + The driver does not support multiple opens and the +device is already in use. + + + + ENXIO + + No device corresponding to this device special file +exists. + + + + ENOMEM + + Not enough kernel memory was available to complete the +request. + + + + EMFILE + + The process already has the maximum number of +files open. + + + + ENFILE + + The limit on the total number of files open on the +system has been reached. + + + + + + + diff --git a/v4l2-spec/func-poll.sgml b/v4l2-spec/func-poll.sgml new file mode 100644 index 000000000..ec3c718f5 --- /dev/null +++ b/v4l2-spec/func-poll.sgml @@ -0,0 +1,127 @@ + + + V4L2 poll() + &manvol; + + + + v4l2-poll + Wait for some event on a file descriptor + + + + + #include <sys/poll.h> + + int poll + struct pollfd *ufds + unsigned int nfds + int timeout + + + + + + Description + + With the poll() function applications +can suspend execution until the driver has captured data or is ready +to accept data for output. + + When streaming I/O has been negotiated this function waits +until a buffer has been filled or displayed and can be dequeued with +the &VIDIOC-DQBUF; ioctl. When buffers are already in the outgoing +queue of the driver the function returns immediately. + + On success poll() returns the number of +file descriptors that have been selected (that is, file descriptors +for which the revents field of the +respective pollfd structure is non-zero). +Capture devices set the POLLIN and +POLLRDNORM flags in the +revents field, output devices the +POLLOUT and POLLWRNORM +flags. When the function timed out it returns a value of zero, on +failure it returns -1 and the +errno variable is set appropriately. When the +application did not call &VIDIOC-QBUF; or &VIDIOC-STREAMON; yet the +poll() function succeeds, but sets the +POLLERR flag in the +revents field. + + When use of the read() function has +been negotiated and the driver does not capture yet, the +poll function starts capturing. When that fails +it returns a POLLERR as above. Otherwise it waits +until data has been captured and can be read. When the driver captures +continuously (as opposed to, for example, still images) the function +may return immediately. + + When use of the write() function has +been negotiated the poll function just waits +until the driver is ready for a non-blocking +write() call. + + All drivers implementing the read() or +write() function or streaming I/O must also +support the poll() function. + + For more details see the +poll() manual page. + + + + Return Value + + On success, poll() returns the number +structures which have non-zero revents +fields, or zero if the call timed out. On error +-1 is returned, and the +errno variable is set appropriately: + + + + EBADF + + One or more of the ufds members +specify an invalid file descriptor. + + + + EBUSY + + The driver does not support multiple read or write +streams and the device is already in use. + + + + EFAULT + + ufds references an inaccessible +memory area. + + + + EINTR + + The call was interrupted by a signal. + + + + EINVAL + + The nfds argument is greater +than OPEN_MAX. + + + + + + + diff --git a/v4l2-spec/func-read.sgml b/v4l2-spec/func-read.sgml new file mode 100644 index 000000000..a67a5f507 --- /dev/null +++ b/v4l2-spec/func-read.sgml @@ -0,0 +1,189 @@ + + + V4L2 read() + &manvol; + + + + v4l2-read + Read from a V4L2 device + + + + + #include <unistd.h> + + ssize_t read + int fd + void *buf + size_t count + + + + + + Arguments + + + + fd + + &fd; + + + + buf + + + + + + count + + + + + + + + + Description + + read() attempts to read up to +count bytes from file descriptor +fd into the buffer starting at +buf. The layout of the data in the buffer is +discussed in the respective device interface section, see ##. If count is zero, +read() returns zero and has no other results. If +count is greater than +SSIZE_MAX, the result is unspecified. Regardless +of the count value each +read() call will provide at most one frame (two +fields) worth of data. + + By default read() blocks until data +becomes available. When the O_NONBLOCK flag was +given to the &func-open; function it +returns immediately with an &EAGAIN; when no data is available. The +&func-select; or &func-poll; functions +can always be used to suspend execution until data becomes available. All +drivers supporting the read() function must also +support select() and +poll(). + + Drivers can implement read functionality in different +ways, using a single or multiple buffers and discarding the oldest or +newest frames once the internal buffers are filled. + + read() never returns a "snapshot" of a +buffer being filled. Using a single buffer the driver will stop +capturing when the application starts reading the buffer until the +read is finished. Thus only the period of the vertical blanking +interval is available for reading, or the capture rate must fall below +the nominal frame rate of the video standard. + +The behavior of +read() when called during the active picture +period or the vertical blanking separating the top and bottom field +depends on the discarding policy. A driver discarding the oldest +frames keeps capturing into an internal buffer, continuously +overwriting the previously, not read frame, and returns the frame +being received at the time of the read() call as +soon as it is complete. + + A driver discarding the newest frames stops capturing until +the next read() call. The frame being received at +read() time is discarded, returning the following +frame instead. Again this implies a reduction of the capture rate to +one half or less of the nominal frame rate. An example of this model +is the video read mode of the bttv driver, initiating a DMA to user +memory when read() is called and returning when +the DMA finished. + + In the multiple buffer model drivers maintain a ring of +internal buffers, automatically advancing to the next free buffer. +This allows continuous capturing when the application can empty the +buffers fast enough. Again, the behavior when the driver runs out of +free buffers depends on the discarding policy. + + Applications can get and set the number of buffers used +internally by the driver with the &VIDIOC-G-PARM; and &VIDIOC-S-PARM; +ioctls. They are optional, however. The discarding policy is not +reported and cannot be changed. For minimum requirements see . + + + + Return Value + + On success, the number of bytes read is returned. It is not +an error if this number is smaller than the number of bytes requested, +or the amount of data required for one frame. This may happen for +example because read() was interrupted by a +signal. On error, -1 is returned, and the errno +variable is set appropriately. In this case the next read will start +at the beginning of a new frame. Possible error codes are: + + + + EAGAIN + + Non-blocking I/O has been selected using +O_NONBLOCK and no data was immediately available for reading. + + + + EBADF + + fd is not a valid file +descriptor or is not open for reading, or the process already has the +maximum number of files open. + + + + EBUSY + + The driver does not support multiple read streams and the +device is already in use. + + + + EFAULT + + buf references an inaccessible +memory area. + + + + EINTR + + The call was interrupted by a signal before any +data was read. + + + + EIO + + I/O error. This indicates some hardware problem or a +failure to communicate with a remote device (USB camera etc.). + + + + EINVAL + + The read() function is not +supported by this driver, not on this device, or generally not on this +type of device. + + + + + + + diff --git a/v4l2-spec/func-select.sgml b/v4l2-spec/func-select.sgml new file mode 100644 index 000000000..b67136231 --- /dev/null +++ b/v4l2-spec/func-select.sgml @@ -0,0 +1,138 @@ + + + V4L2 select() + &manvol; + + + + v4l2-select + Synchronous I/O multiplexing + + + + + +#include <sys/time.h> +#include <sys/types.h> +#include <unistd.h> + + int select + int nfds + fd_set *readfds + fd_set *writefds + fd_set *exceptfds + struct timeval *timeout + + + + + + Description + + With the select() function applications +can suspend execution until the driver has captured data or is ready +to accept data for output. + + When streaming I/O has been negotiated this function waits +until a buffer has been filled or displayed and can be dequeued with +the &VIDIOC-DQBUF; ioctl. When buffers are already in the outgoing +queue of the driver the function returns immediately. + + On success select() returns the total +number of bits set in the fd_sets. When the +function timed out it returns a value of zero. On failure it returns +-1 and the errno +variable is set appropriately. When the application did not call +&VIDIOC-QBUF; or &VIDIOC-STREAMON; yet the +select() function succeeds, setting the bit of +the file descriptor in readfds or +writefds, but subsequent &VIDIOC-DQBUF; calls +will fail.The Linux kernel implements +select() like the &func-poll; function, but +select() cannot return a +POLLERR. + + + When use of the read() function has +been negotiated and the driver does not capture yet, the +select() function starts capturing. When that +fails, select() returns successful and a +subsequent read() call, which also attempts to +start capturing, will return an appropriate error code. When the +driver captures continuously (as opposed to, for example, still +images) and data is already available the +select() function returns immediately. + + When use of the write() function has +been negotiated the select() function just waits +until the driver is ready for a non-blocking +write() call. + + All drivers implementing the read() or +write() function or streaming I/O must also +support the select() function. + + For more details see the select() +manual page. + + + + + Return Value + + On success, select() returns the number +of descriptors contained in the three returned descriptor sets, which +will be zero if the timeout expired. On error +-1 is returned, and the +errno variable is set appropriately; the sets and +timeout are undefined. Possible error codes +are: + + + + EBADF + + One or more of the file descriptor sets specified a +file descriptor that is not open. + + + + EBUSY + + The driver does not support multiple read or write +streams and the device is already in use. + + + + EFAULT + + The readfds, +writefds, exceptfds or +timeout pointer references an inaccessible memory +area. + + + + EINTR + + The call was interrupted by a signal. + + + + EINVAL + + The nfds argument is less than +zero or greater than FD_SETSIZE. + + + + + + + diff --git a/v4l2-spec/func-write.sgml b/v4l2-spec/func-write.sgml new file mode 100644 index 000000000..2c09c0937 --- /dev/null +++ b/v4l2-spec/func-write.sgml @@ -0,0 +1,136 @@ + + + V4L2 write() + &manvol; + + + + v4l2-write + Write to a V4L2 device + + + + + #include <unistd.h> + + ssize_t write + int fd + void *buf + size_t count + + + + + + Arguments + + + + fd + + &fd; + + + + buf + + + + + + count + + + + + + + + + Description + + write() writes up to +count bytes to the device referenced by the +file descriptor fd from the buffer starting at +buf. When the hardware outputs are not active +yet, this function enables them. When count is +zero, write() returns +0 without any other effect. + + When the application does not provide more data in time, the +previous video frame, raw VBI image, sliced VPS or WSS data is +displayed again. Sliced Teletext or Closed Caption data is not +repeated, the driver inserts a blank line instead. + + + + Return Value + + On success, the number of bytes written are returned. Zero +indicates nothing was written. On error, -1 +is returned, and the errno variable is set +appropriately. In this case the next write will start at the beginning +of a new frame. Possible error codes are: + + + + EAGAIN + + Non-blocking I/O has been selected using the O_NONBLOCK flag and no +buffer space was available to write the data immediately. + + + + EBADF + + fd is not a valid file +descriptor or is not open for writing. + + + + EBUSY + + The driver does not support multiple write streams and the +device is already in use. + + + + EFAULT + + buf references an inaccessible +memory area. + + + + EINTR + + The call was interrupted by a signal before any +data was written. + + + + EIO + + I/O error. This indicates some hardware problem. + + + + EINVAL + + The write() function is not +supported by this driver, not on this device, or generally not on this +type of device. + + + + + + + diff --git a/v4l2-spec/io.sgml b/v4l2-spec/io.sgml new file mode 100644 index 000000000..957ffa0bc --- /dev/null +++ b/v4l2-spec/io.sgml @@ -0,0 +1,1073 @@ + Input/Output + + The V4L2 API defines several different methods to read from or +write to a device. All drivers exchanging data with applications must +support at least one of them. + + The classic I/O method using the read() +and write() function is automatically selected +after opening a V4L2 device. When the driver does not support this +method attempts to read or write will fail at any time. + + Other methods must be negotiated. To select the streaming I/O +method with memory mapped or user buffers applications call the +&VIDIOC-REQBUFS; ioctl. The asynchronous I/O method is not defined +yet. + + Video overlay can be considered another I/O method, although +the application does not directly receive the image data. It is +selected by initiating video overlay with the &VIDIOC-S-FMT; ioctl. +For more information see . + + Generally exactly one I/O method, including overlay, is +associated with each file descriptor. The only exceptions are +applications not exchanging data with a driver ("panel applications", +see ) and drivers permitting simultaneous video capturing +and overlay using the same file descriptor, for compatibility with V4L +and earlier versions of V4L2. + + VIDIOC_S_FMT and +VIDIOC_REQBUFS would permit this to some degree, +but for simplicity drivers need not support switching the I/O method +(after first switching away from read/write) other than by closing +and reopening the device. + + The following sections describe the various I/O methods in +more detail. + +
+ Read/Write + + Input and output devices support the +read() and write() function, +respectively, when the V4L2_CAP_READWRITE flag in +the capabilities field of &v4l2-capability; +returned by the &VIDIOC-QUERYCAP; ioctl is set. + + Drivers may need the CPU to copy the data, but they may also +support DMA to or from user memory, so this I/O method is not +necessarily less efficient than other methods merely exchanging buffer +pointers. It is considered inferior though because no meta-information +like frame counters or timestamps are passed. This information is +necessary to recognize frame dropping and to synchronize with other +data streams. However this is also the simplest I/O method, requiring +little or no setup to exchange data. It permits command line stunts +like this (the vidctrl tool is +fictitious): + + + +> vidctrl /dev/video --input=0 --format=YUYV --size=352x288 +> dd if=/dev/video of=myimage.422 bs=202752 count=1 + + + + To read from the device applications use the +&func-read; function, to write the &func-write; function. +Drivers must implement one I/O method if they +exchange data with applications, but it need not be this. + It would be desirable if applications could depend on +drivers supporting all I/O interfaces, but as much as the complex +memory mapping I/O can be inadequate for some devices we have no +reason to require this interface, which is most useful for simple +applications capturing still images. + When reading or writing is supported, the driver +must also support the &func-select; and &func-poll; +function. + At the driver level select() and +poll() are the same, and +select() is too important to be optional. + +
+ +
+ Streaming I/O (Memory Mapping) + + Input and output devices support this I/O method when the +V4L2_CAP_STREAMING flag in the +capabilities field of &v4l2-capability; +returned by the &VIDIOC-QUERYCAP; ioctl is set. There are two +streaming methods, to determine if the memory mapping flavor is +supported applications must call the &VIDIOC-REQBUFS; ioctl. + + Streaming is an I/O method where only pointers to buffers +are exchanged between application and driver, the data itself is not +copied. Memory mapping is primarily intended to map buffers in device +memory into the application's address space. Device memory can be for +example the video memory on a graphics card with a video capture +add-on. However, being the most efficient I/O method available for a +long time, many other drivers support streaming as well, allocating +buffers in DMA-able main memory. + + A driver can support many sets of buffers. Each set is +identified by a unique buffer type value. The sets are independent and +each set can hold a different type of data. To access different sets +at the same time different file descriptors must be used. + One could use one file descriptor and set the buffer +type field accordingly when calling &VIDIOC-QBUF; etc., but it makes +the select() function ambiguous. We also like the +clean approach of one file descriptor per logical stream. Video +overlay for example is also a logical stream, although the CPU is not +needed for continuous operation. + + + To allocate device buffers applications call the +&VIDIOC-REQBUFS; ioctl with the desired number of buffers and buffer +type, for example V4L2_BUF_TYPE_VIDEO_CAPTURE. +This ioctl can also be used to change the number of buffers or to free +the allocated memory, provided none of the buffers are still +mapped. + + Before applications can access the buffers they must map +them into their address space with the &func-mmap; function. The +location of the buffers in device memory can be determined with the +&VIDIOC-QUERYBUF; ioctl. The m.offset and +length returned in a &v4l2-buffer; are +passed as sixth and second parameter to the +mmap() function. The offset and length values +must not be modified. Remember the buffers are allocated in physical +memory, as opposed to virtual memory which can be swapped out to disk. +Applications should free the buffers as soon as possible with the +&func-munmap; function. + + + Mapping buffers + + +&v4l2-requestbuffers; reqbuf; +struct { + void *start; + size_t length; +} *buffers; +unsigned int i; + +memset (&reqbuf, 0, sizeof (reqbuf)); +reqbuf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE; +reqbuf.memory = V4L2_MEMORY_MMAP; +reqbuf.count = 20; + +if (-1 == ioctl (fd, &VIDIOC-REQBUFS;, &reqbuf)) { + if (errno == EINVAL) + printf ("Video capturing or mmap-streaming is not supported\n"); + else + perror ("VIDIOC_REQBUFS"); + + exit (EXIT_FAILURE); +} + +/* We want at least five buffers. */ + +if (reqbuf.count < 5) { + /* You may need to free the buffers here. */ + printf ("Not enough buffer memory\n"); + exit (EXIT_FAILURE); +} + +buffers = calloc (reqbuf.count, sizeof (*buffers)); +assert (buffers != NULL); + +for (i = 0; i < reqbuf.count; i++) { + &v4l2-buffer; buffer; + + memset (&buffer, 0, sizeof (buffer)); + buffer.type = reqbuf.type; + buffer.memory = V4L2_MEMORY_MMAP; + buffer.index = i; + + if (-1 == ioctl (fd, &VIDIOC-QUERYBUF;, &buffer)) { + perror ("VIDIOC_QUERYBUF"); + exit (EXIT_FAILURE); + } + + buffers[i].length = buffer.length; /* remember for munmap() */ + + buffers[i].start = mmap (NULL, buffer.length, + PROT_READ | PROT_WRITE, /* recommended */ + MAP_SHARED, /* recommended */ + fd, buffer.m.offset); + + if (MAP_FAILED == buffers[i].start) { + /* If you do not exit here you should unmap() and free() + the buffers mapped so far. */ + perror ("mmap"); + exit (EXIT_FAILURE); + } +} + +/* Cleanup. */ + +for (i = 0; i < reqbuf.count; i++) + munmap (buffers[i].start, buffers[i].length); + + + + Conceptually streaming drivers maintain two buffer queues, an incoming +and an outgoing queue. They separate the synchronous capture or output +operation locked to a video clock from the application which is +subject to random disk or network delays and preemption by +other processes, thereby reducing the probability of data loss. +The queues are organized as FIFOs, buffers will be +output in the order enqueued in the incoming FIFO, and were +captured in the order dequeued from the outgoing FIFO. + + The driver may require a minimum number of buffers enqueued +at all times to function, apart of this no limit exists on the number +of buffers applications can enqueue in advance, or dequeue and +process. They can also enqueue in a different order than buffers have +been dequeued, and the driver can fill enqueued +empty buffers in any order. + Random enqueue order permits applications processing +images out of order (such as video codecs) to return buffers earlier, +reducing the probability of data loss. Random fill order allows +drivers to reuse buffers on a LIFO-basis, taking advantage of caches +holding scatter-gather lists and the like. + The index number of a buffer (&v4l2-buffer; +index) plays no role here, it only +identifies the buffer. + + Initially all mapped buffers are in dequeued state, +inaccessible by the driver. For capturing applications it is customary +to first enqueue all mapped buffers, then to start capturing and enter +the read loop. Here the application waits until a filled buffer can be +dequeued, and re-enqueues the buffer when the data is no longer +needed. Output applications fill and enqueue buffers, when enough +buffers are stacked up the output is started with +VIDIOC_STREAMON. In the write loop, when +the application runs out of free buffers, it must wait until an empty +buffer can be dequeued and reused. + + To enqueue and dequeue a buffer applications use the +&VIDIOC-QBUF; and &VIDIOC-DQBUF; ioctl. The status of a buffer being +mapped, enqueued, full or empty can be determined at any time using the +&VIDIOC-QUERYBUF; ioctl. Two methods exist to suspend execution of the +application until one or more buffers can be dequeued. By default +VIDIOC_DQBUF blocks when no buffer is in the +outgoing queue. When the O_NONBLOCK flag was +given to the &func-open; function, VIDIOC_DQBUF +returns immediately with an &EAGAIN; when no buffer is available. The +&func-select; or &func-poll; function are always available. + + To start and stop capturing or output applications call the +&VIDIOC-STREAMON; and &VIDIOC-STREAMOFF; ioctl. Note +VIDIOC_STREAMOFF removes all buffers from both +queues as a side effect. Since there is no notion of doing anything +"now" on a multitasking system, if an application needs to synchronize +with another event it should examine the &v4l2-buffer; +timestamp of captured buffers, or set the +field before enqueuing buffers for output. + + Drivers implementing memory mapping I/O must +support the VIDIOC_REQBUFS, +VIDIOC_QUERYBUF, +VIDIOC_QBUF, VIDIOC_DQBUF, +VIDIOC_STREAMON and +VIDIOC_STREAMOFF ioctl, the +mmap(), munmap(), +select() and poll() +function. + At the driver level select() and +poll() are the same, and +select() is too important to be optional. The +rest should be evident. + + + [capture example] + +
+ +
+ Streaming I/O (User Pointers) + + Input and output devices support this I/O method when the +V4L2_CAP_STREAMING flag in the +capabilities field of &v4l2-capability; +returned by the &VIDIOC-QUERYCAP; ioctl is set. If the particular user +pointer method (not only memory mapping) is supported must be +determined by calling the &VIDIOC-REQBUFS; ioctl. + + This I/O method combines advantages of the read/write and +memory mapping methods. Buffers are allocated by the application +itself, and can reside for example in virtual or shared memory. Only +pointers to data are exchanged, these pointers and meta-information +are passed in &v4l2-buffer;. The driver must be switched +into user pointer I/O mode by calling the &VIDIOC-REQBUFS; with the +desired buffer type. No buffers are allocated beforehands, +consequently they are not indexed and cannot be queried like mapped +buffers with the VIDIOC_QUERYBUF ioctl. + + + Initiating streaming I/O with user pointers + + +&v4l2-requestbuffers; reqbuf; + +memset (&reqbuf, 0, sizeof (reqbuf)); +reqbuf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE; +reqbuf.memory = V4L2_MEMORY_USERPTR; + +if (ioctl (fd, &VIDIOC-REQBUFS;, &reqbuf) == -1) { + if (errno == EINVAL) + printf ("Video capturing or user pointer streaming is not supported\n"); + else + perror ("VIDIOC_REQBUFS"); + + exit (EXIT_FAILURE); +} + + + + Buffer addresses and sizes are passed on the fly with the +&VIDIOC-QBUF; ioctl. Although buffers are commonly cycled, +applications can pass different addresses and sizes at each +VIDIOC_QBUF call. If required by the hardware the +driver swaps memory pages within physical memory to create a +continuous area of memory. This happens transparently to the +application in the virtual memory subsystem of the kernel. When buffer +pages have been swapped out to disk they are brought back and finally +locked in physical memory for DMA. + We expect that frequently used buffers are typically not +swapped out. Anyway, the process of swapping, locking or generating +scatter-gather lists may be time consuming. The delay can be masked by +the depth of the incoming buffer queue, and perhaps by maintaining +caches assuming a buffer will be soon enqueued again. On the other +hand, to optimize memory usage drivers can limit the number of buffers +locked in advance and recycle the most recently used buffers first. Of +course, the pages of empty buffers in the incoming queue need not be +saved to disk. Output buffers must be saved on the incoming and +outgoing queue because an application may share them with other +processes. + + + Filled or displayed buffers are dequeued with the +&VIDIOC-DQBUF; ioctl. The driver can unlock the memory pages at any +time between the completion of the DMA and this ioctl. The memory is +also unlocked when &VIDIOC-STREAMOFF; is called, &VIDIOC-REQBUFS;, or +when the device is closed. Applications must take care not to free +buffers without dequeuing. For once, the buffers remain locked until +further, wasting physical memory. Second the driver will not be +notified when the memory is returned to the application's free list +and subsequently reused for other purposes, possibly completing the +requested DMA and overwriting valuable data. + + For capturing applications it is customary to enqueue a +number of empty buffers, to start capturing and enter the read loop. +Here the application waits until a filled buffer can be dequeued, and +re-enqueues the buffer when the data is no longer needed. Output +applications fill and enqueue buffers, when enough buffers are stacked +up output is started. In the write loop, when the application +runs out of free buffers it must wait until an empty buffer can be +dequeued and reused. Two methods exist to suspend execution of the +application until one or more buffers can be dequeued. By default +VIDIOC_DQBUF blocks when no buffer is in the +outgoing queue. When the O_NONBLOCK flag was +given to the &func-open; function, VIDIOC_DQBUF +returns immediately with an &EAGAIN; when no buffer is available. The +&func-select; or &func-poll; function are always available. + + To start and stop capturing or output applications call the +&VIDIOC-STREAMON; and &VIDIOC-STREAMOFF; ioctl. Note +VIDIOC_STREAMOFF removes all buffers from both +queues and unlocks all buffers as a side effect. Since there is no +notion of doing anything "now" on a multitasking system, if an +application needs to synchronize with another event it should examine +the &v4l2-buffer; timestamp of captured +buffers, or set the field before enqueuing buffers for output. + + Drivers implementing user pointer I/O must +support the VIDIOC_REQBUFS, +VIDIOC_QBUF, VIDIOC_DQBUF, +VIDIOC_STREAMON and +VIDIOC_STREAMOFF ioctl, the +select() and poll() function. + At the driver level select() and +poll() are the same, and +select() is too important to be optional. The +rest should be evident. + +
+ +
+ Asynchronous I/O + + This method is not defined yet. +
+ +
+ Buffers + + A buffer contains data exchanged by application and +driver using one of the Streaming I/O methods. Only pointers to +buffers are exchanged, the data itself is not copied. These pointers, +together with meta-information like timestamps or field parity, are +stored in a struct v4l2_buffer, argument to +the &VIDIOC-QUERYBUF;, &VIDIOC-QBUF; and &VIDIOC-DQBUF; ioctl. + + Nominally timestamps refer to the first data byte transmitted. +In practice however the wide range of hardware covered by the V4L2 API +limits timestamp accuracy. Often an interrupt routine will +sample the system clock shortly after the field or frame was stored +completely in memory. So applications must expect a constant +difference up to one field or frame period plus a small (few scan +lines) random error. The delay and error can be much +larger due to compression or transmission over an external bus when +the frames are not properly stamped by the sender. This is frequently +the case with USB cameras. Here timestamps refer to the instant the +field or frame was received by the driver, not the capture time. These +devices identify by not enumerating any video standards, see . + + Similar limitations apply to output timestamps. Typically +the video hardware locks to a clock controlling the video timing, the +horizontal and vertical synchronization pulses. At some point in the +line sequence, possibly the vertical blanking, an interrupt routine +samples the system clock, compares against the timestamp and programs +the hardware to repeat the previous field or frame, or to display the +buffer contents. + + Apart of limitations of the video device and natural +inaccuracies of all clocks, it should be noted system time itself is +not perfectly stable. It can be affected by power saving cycles, +warped to insert leap seconds, or even turned back or forth by the +system administrator affecting long term measurements. + Since no other Linux multimedia +API supports unadjusted time it would be foolish to introduce here. We +must use a universally supported clock to synchronize different media, +hence time of day. + + + + struct <structname>v4l2_buffer</structname> + + &cs-ustr; + + + __u32 + index + + Number of the buffer, set by the application. This +field is only used for memory mapping I/O +and can range from zero to the number of buffers allocated +with the &VIDIOC-REQBUFS; ioctl (&v4l2-requestbuffers; count) minus one. + + + &v4l2-buf-type; + type + + Type of the buffer, same as &v4l2-format; +type or &v4l2-requestbuffers; +type, set by the application. + + + __u32 + bytesused + + The number of bytes occupied by the data in the +buffer. It depends on the negotiated data format and may change with +each buffer for compressed variable size data like JPEG images. +Drivers must set this field when type +refers to an input stream, applications when an output stream. + + + __u32 + flags + + Flags set by the application or driver, see . + + + &v4l2-field; + field + + Indicates the field order of the image in the +buffer, see . This field is not used when +the buffer contains VBI data. Drivers must set it when +type refers to an input stream, +applications when an output stream. + + + struct timeval + timestamp + + For input streams this is the +system time (as returned by the gettimeofday() +function) when the first data byte was captured. For output streams +the data will not be displayed before this time, secondary to the +nominal frame rate determined by the current video standard in +enqueued order. Applications can for example zero this field to +display frames as soon as possible. The driver stores the time at +which the first data byte was actually sent out in the +timestamp field. This permits +applications to monitor the drift between the video and system +clock. + + + &v4l2-timecode; + timecode + + When type is +V4L2_BUF_TYPE_VIDEO_CAPTURE and the +V4L2_BUF_FLAG_TIMECODE flag is set in +flags, this structure contains a frame +timecode. In V4L2_FIELD_ALTERNATE +mode the top and bottom field contain the same timecode. +Timecodes are intended to help video editing and are typically recorded on +video tapes, but also embedded in compressed formats like MPEG. This +field is independent of the timestamp and +sequence fields. + + + __u32 + sequence + + Set by the driver, counting the frames in the +sequence. + + + In V4L2_FIELD_ALTERNATE mode the top and +bottom field have the same sequence number. The count starts at zero +and includes dropped or repeated frames. A dropped frame was received +by an input device but could not be stored due to lack of free buffer +space. A repeated frame was displayed again by an output device +because the application did not pass new data in +time.Note this may count the frames received +e.g. over USB, without taking into account the frames dropped by the +remote hardware due to limited compression throughput or bus +bandwidth. These devices identify by not enumerating any video +standards, see . + + + &v4l2-memory; + memory + + This field must be set by applications and/or drivers +in accordance with the selected I/O method. + + + union + m + + + + __u32 + offset + When memory is +V4L2_MEMORY_MMAP this is the offset of the buffer +from the start of the device memory. The value is returned by the +driver and apart of serving as parameter to the &func-mmap; function +not useful for applications. See for details. + + + + unsigned long + userptr + When memory is +V4L2_MEMORY_USERPTR this is a pointer to the +buffer (casted to unsigned long type) in virtual memory, set by the +application. See for details. + + + __u32 + length + + Size of the buffer (not the payload) in bytes. + + + __u32 + input + + Some video capture drivers support rapid and +synchronous video input changes, a function useful for example in +video surveillance applications. For this purpose applications set the +V4L2_BUF_FLAG_INPUT flag, and this field to the +number of a video input as in &v4l2-input; field +index. + + + __u32 + reserved + + A place holder for future extensions and custom +(driver defined) buffer types +V4L2_BUF_TYPE_PRIVATE and higher. + + + +
+ + + enum v4l2_buf_type + + &cs-def; + + + V4L2_BUF_TYPE_VIDEO_CAPTURE + 1 + Buffer of a video capture stream, see . + + + V4L2_BUF_TYPE_VIDEO_OUTPUT + 2 + Buffer of a video output stream, see . + + + V4L2_BUF_TYPE_VIDEO_OVERLAY + 3 + Buffer for video overlay, see . + + + V4L2_BUF_TYPE_VBI_CAPTURE + 4 + Buffer of a raw VBI capture stream, see . + + + V4L2_BUF_TYPE_VBI_OUTPUT + 5 + Buffer of a raw VBI output stream, see . + + + V4L2_BUF_TYPE_SLICED_VBI_CAPTURE + 6 + Buffer of a sliced VBI capture stream, see . + + + V4L2_BUF_TYPE_SLICED_VBI_OUTPUT + 7 + Buffer of a sliced VBI output stream, see . + + + V4L2_BUF_TYPE_VIDEO_OUTPUT_OVERLAY + 8 + Buffer for video output overlay (OSD), see . Status: Experimental. + + + V4L2_BUF_TYPE_PRIVATE + 0x80 + This and higher values are reserved for custom +(driver defined) buffer types. + + + +
+ + + Buffer Flags + + &cs-def; + + + V4L2_BUF_FLAG_MAPPED + 0x0001 + The buffer resides in device memory and has been mapped +into the application's address space, see for details. +Drivers set or clear this flag when the +VIDIOC_QUERYBUF, VIDIOC_QBUF or VIDIOC_DQBUF ioctl is called. Set by the driver. + + + V4L2_BUF_FLAG_QUEUED + 0x0002 + Internally drivers maintain two buffer queues, an +incoming and outgoing queue. When this flag is set, the buffer is +currently on the incoming queue. It automatically moves to the +outgoing queue after the buffer has been filled (capture devices) or +displayed (output devices). Drivers set or clear this flag when the +VIDIOC_QUERYBUF ioctl is called. After +(successful) calling the VIDIOC_QBUF ioctl it is +always set and after VIDIOC_DQBUF always +cleared. + + + V4L2_BUF_FLAG_DONE + 0x0004 + When this flag is set, the buffer is currently on +the outgoing queue, ready to be dequeued from the driver. Drivers set +or clear this flag when the VIDIOC_QUERYBUF ioctl +is called. After calling the VIDIOC_QBUF or +VIDIOC_DQBUF it is always cleared. Of course a +buffer cannot be on both queues at the same time, the +V4L2_BUF_FLAG_QUEUED and +V4L2_BUF_FLAG_DONE flag are mutually exclusive. +They can be both cleared however, then the buffer is in "dequeued" +state, in the application domain to say so. + + + V4L2_BUF_FLAG_KEYFRAME + 0x0008 + Drivers set or clear this flag when calling the +VIDIOC_DQBUF ioctl. It may be set by video +capture devices when the buffer contains a compressed image which is a +key frame (or field), &ie; can be decompressed on its own. + + + V4L2_BUF_FLAG_PFRAME + 0x0010 + Similar to V4L2_BUF_FLAG_KEYFRAME +this flags predicted frames or fields which contain only differences to a +previous key frame. + + + V4L2_BUF_FLAG_BFRAME + 0x0020 + Similar to V4L2_BUF_FLAG_PFRAME + this is a bidirectional predicted frame or field. [ooc tbd] + + + V4L2_BUF_FLAG_TIMECODE + 0x0100 + The timecode field is valid. +Drivers set or clear this flag when the VIDIOC_DQBUF +ioctl is called. + + + V4L2_BUF_FLAG_INPUT + 0x0200 + The input field is valid. +Applications set or clear this flag before calling the +VIDIOC_QBUF ioctl. + + + +
+ + + enum v4l2_memory + + &cs-def; + + + V4L2_MEMORY_MMAP + 1 + The buffer is used for memory +mapping I/O. + + + V4L2_MEMORY_USERPTR + 2 + The buffer is used for user +pointer I/O. + + + V4L2_MEMORY_OVERLAY + 3 + [to do] + + + +
+ +
+ Timecodes + + The v4l2_timecode structure is +designed to hold a or similar timecode. +(struct timeval timestamps are stored in +&v4l2-buffer; field timestamp.) + + + struct <structname>v4l2_timecode</structname> + + &cs-str; + + + __u32 + type + Frame rate the timecodes are based on, see . + + + __u32 + flags + Timecode flags, see . + + + __u8 + frames + Frame count, 0 ... 23/24/29/49/59, depending on the + type of timecode. + + + __u8 + seconds + Seconds count, 0 ... 59. This is a binary, not BCD number. + + + __u8 + minutes + Minutes count, 0 ... 59. This is a binary, not BCD number. + + + __u8 + hours + Hours count, 0 ... 29. This is a binary, not BCD number. + + + __u8 + userbits[4] + The "user group" bits from the timecode. + + + +
+ + + Timecode Types + + &cs-def; + + + V4L2_TC_TYPE_24FPS + 1 + 24 frames per second, i. e. film. + + + V4L2_TC_TYPE_25FPS + 2 + 25 frames per second, &ie; PAL or SECAM video. + + + V4L2_TC_TYPE_30FPS + 3 + 30 frames per second, &ie; NTSC video. + + + V4L2_TC_TYPE_50FPS + 4 + + + + V4L2_TC_TYPE_60FPS + 5 + + + + +
+ + + Timecode Flags + + &cs-def; + + + V4L2_TC_FLAG_DROPFRAME + 0x0001 + Indicates "drop frame" semantics for counting frames +in 29.97 fps material. When set, frame numbers 0 and 1 at the start of +each minute, except minutes 0, 10, 20, 30, 40, 50 are omitted from the +count. + + + V4L2_TC_FLAG_COLORFRAME + 0x0002 + The "color frame" flag. + + + V4L2_TC_USERBITS_field + 0x000C + Field mask for the "binary group flags". + + + V4L2_TC_USERBITS_USERDEFINED + 0x0000 + Unspecified format. + + + V4L2_TC_USERBITS_8BITCHARS + 0x0008 + 8-bit ISO characters. + + + +
+
+
+ +
+ Field Order + + We have to distinguish between progressive and interlaced +video. Progressive video transmits all lines of a video image +sequentially. Interlaced video divides an image into two fields, +containing only the odd and even lines of the image, respectively. +Alternating the so called odd and even field are transmitted, and due +to a small delay between fields a cathode ray TV displays the lines +interleaved, yielding the original frame. This curious technique was +invented because at refresh rates similar to film the image would +fade out too quickly. Transmitting fields reduces the flicker without +the necessity of doubling the frame rate and with it the bandwidth +required for each channel. + + It is important to understand a video camera does not expose +one frame at a time, merely transmitting the frames separated into +fields. The fields are in fact captured at two different instances in +time. An object on screen may well move between one field and the +next. For applications analysing motion it is of paramount importance +to recognize which field of a frame is older, the temporal +order. + + When the driver provides or accepts images field by field +rather than interleaved, it is also important applications understand +how the fields combine to frames. We distinguish between top and +bottom fields, the spatial order: The first line +of the top field is the first line of an interlaced frame, the first +line of the bottom field is the second line of that frame. + + However because fields were captured one after the other, +arguing whether a frame commences with the top or bottom field is +pointless. Any two successive top and bottom, or bottom and top fields +yield a valid frame. Only when the source was progressive to begin +with, ⪚ when transferring film to video, two fields may come from +the same frame, creating a natural order. + + Counter to intuition the top field is not necessarily the +older field. Whether the older field contains the top or bottom lines +is a convention determined by the video standard. Hence the +distinction between temporal and spatial order of fields. The diagrams +below should make this clearer. + + All video capture and output devices must report the current +field order. Some drivers may permit the selection of a different +order, to this end applications initialize the +field field of &v4l2-pix-format; before +calling the &VIDIOC-S-FMT; ioctl. If this is not desired it should +have the value V4L2_FIELD_ANY (0). + + + enum v4l2_field + + &cs-def; + + + V4L2_FIELD_ANY + 0 + Applications request this field order when any +one of the V4L2_FIELD_NONE, +V4L2_FIELD_TOP, +V4L2_FIELD_BOTTOM, or +V4L2_FIELD_INTERLACED formats is acceptable. +Drivers choose depending on hardware capabilities or e. g. the +requested image size, and return the actual field order. &v4l2-buffer; +field can never be +V4L2_FIELD_ANY. + + + V4L2_FIELD_NONE + 1 + Images are in progressive format, not interlaced. +The driver may also indicate this order when it cannot distinguish +between V4L2_FIELD_TOP and +V4L2_FIELD_BOTTOM. + + + V4L2_FIELD_TOP + 2 + Images consist of the top field only. + + + V4L2_FIELD_BOTTOM + 3 + Images consist of the bottom field only. +Applications may wish to prevent a device from capturing interlaced +images because they will have "comb" or "feathering" artefacts around +moving objects. + + + V4L2_FIELD_INTERLACED + 4 + Images contain both fields, interleaved line by +line. The temporal order of the fields (whether the top or bottom +field is first transmitted) depends on the current video standard. +M/NTSC transmits the bottom field first, all other standards the top +field first. + + + V4L2_FIELD_SEQ_TB + 5 + Images contain both fields, the top field lines +are stored first in memory, immediately followed by the bottom field +lines. Fields are always stored in temporal order, the older one first +in memory. Image sizes refer to the frame, not fields. + + + V4L2_FIELD_SEQ_BT + 6 + Images contain both fields, the bottom field +lines are stored first in memory, immediately followed by the top +field lines. Fields are always stored in temporal order, the older one +first in memory. Image sizes refer to the frame, not fields. + + + V4L2_FIELD_ALTERNATE + 7 + The two fields of a frame are passed in separate +buffers, in temporal order, &ie; the older one first. To indicate the field +parity (whether the current field is a top or bottom field) the driver +or application, depending on data direction, must set &v4l2-buffer; +field to +V4L2_FIELD_TOP or +V4L2_FIELD_BOTTOM. Any two successive fields pair +to build a frame. If fields are successive, without any dropped fields +between them (fields can drop individually), can be determined from +the &v4l2-buffer; sequence field. Image +sizes refer to the frame, not fields. This format cannot be selected +when using the read/write I/O method. + + + V4L2_FIELD_INTERLACED_TB + 8 + Images contain both fields, interleaved line by +line, top field first. The top field is transmitted first. + + + V4L2_FIELD_INTERLACED_BT + 9 + Images contain both fields, interleaved line by +line, top field first. The bottom field is transmitted first. + + + +
+ +
+ Field Order, Top Field First Transmitted + + + + + + + + +
+ +
+ Field Order, Bottom Field First Transmitted + + + + + + + + +
+
+ + diff --git a/v4l2-spec/pixfmt-grey.sgml b/v4l2-spec/pixfmt-grey.sgml new file mode 100644 index 000000000..271814c53 --- /dev/null +++ b/v4l2-spec/pixfmt-grey.sgml @@ -0,0 +1,70 @@ + + + V4L2_PIX_FMT_GREY ('GREY') + &manvol; + + + V4L2_PIX_FMT_GREY + Grey-scale image + + + Description + + This is a grey-scale image. It is really a degenerate +Y'CbCr format which simply contains no Cb or Cr data. + + + <constant>V4L2_PIX_FMT_GREY</constant> 4 × 4 +pixel image + + + Byte Order. + Each cell is one byte. + + + + + + start + 0: + Y'00 + Y'01 + Y'02 + Y'03 + + + start + 4: + Y'10 + Y'11 + Y'12 + Y'13 + + + start + 8: + Y'20 + Y'21 + Y'22 + Y'23 + + + start + 12: + Y'30 + Y'31 + Y'32 + Y'33 + + + + + + + + + + + diff --git a/v4l2-spec/pixfmt-nv12.sgml b/v4l2-spec/pixfmt-nv12.sgml new file mode 100644 index 000000000..ec3aec6a0 --- /dev/null +++ b/v4l2-spec/pixfmt-nv12.sgml @@ -0,0 +1,151 @@ + + + V4L2_PIX_FMT_NV12 ('NV12'), V4L2_PIX_FMT_NV21 ('NV21') + &manvol; + + + V4L2_PIX_FMT_NV12 + V4L2_PIX_FMT_NV21 + Formats with ½ horizontal and vertical +chroma resolution, also known as YUV 4:2:0. One luminance and one +chrominance plane with alternating chroma samples as opposed to +V4L2_PIX_FMT_YVU420 + + + Description + + These are two-plane versions of the YUV 4:2:0 format. +The three components are separated into two sub-images or planes. The +Y plane is first. The Y plane has one byte per pixel. For +V4L2_PIX_FMT_NV12, a combined CbCr plane +immediately follows the Y plane in memory. The CbCr plane is the same +width, in bytes, as the Y plane (and of the image), but is half as +tall in pixels. Each CbCr pair belongs to four pixels. For example, +Cb0/Cr0 belongs to +Y'00, Y'01, +Y'10, Y'11. +V4L2_PIX_FMT_NV21 is the same except the Cb and +Cr bytes are swapped, the CrCb plane starts with a Cr byte. + + If the Y plane has pad bytes after each row, then the +CbCr plane has as many pad bytes after its rows. + + + <constant>V4L2_PIX_FMT_NV12</constant> 4 × 4 +pixel image + + + Byte Order. + Each cell is one byte. + + + + + + start + 0: + Y'00 + Y'01 + Y'02 + Y'03 + + + start + 4: + Y'10 + Y'11 + Y'12 + Y'13 + + + start + 8: + Y'20 + Y'21 + Y'22 + Y'23 + + + start + 12: + Y'30 + Y'31 + Y'32 + Y'33 + + + start + 16: + Cb00 + Cr00 + Cb01 + Cr01 + + + start + 20: + Cb10 + Cr10 + Cb11 + Cr11 + + + + + + + + + Color Sample Location. + + + + + + + 01 + 23 + + + 0 + YY + YY + + + + C + C + + + 1 + YY + YY + + + + + + 2 + YY + YY + + + + C + C + + + 3 + YY + YY + + + + + + + + + + + diff --git a/v4l2-spec/pixfmt-packed-rgb.sgml b/v4l2-spec/pixfmt-packed-rgb.sgml new file mode 100644 index 000000000..8c32db3c2 --- /dev/null +++ b/v4l2-spec/pixfmt-packed-rgb.sgml @@ -0,0 +1,862 @@ + + + Packed RGB formats + &manvol; + + + Packed RGB formats + Packed RGB formats + + + Description + + These formats are designed to match the pixel formats of +typical PC graphics frame buffers. They occupy 8, 16, 24 or 32 bits +per pixel. These are all packed-pixel formats, meaning all the data +for a pixel lie next to each other in memory. + + When one of these formats is used, drivers shall report the +colorspace V4L2_COLORSPACE_SRGB. + + + Packed RGB Image Formats + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + Identifier + Code +   + Byte 0 in memory + Byte 1 + Byte 2 + Byte 3 + + +   +   + Bit + 7 + 6 + 5 + 4 + 3 + 2 + 1 + 0 +   + 7 + 6 + 5 + 4 + 3 + 2 + 1 + 0 +   + 7 + 6 + 5 + 4 + 3 + 2 + 1 + 0 +   + 7 + 6 + 5 + 4 + 3 + 2 + 1 + 0 + + + + + V4L2_PIX_FMT_RGB332 + 'RGB1' + + b1 + b0 + g2 + g1 + g0 + r2 + r1 + r0 + + + V4L2_PIX_FMT_RGB444 + 'R444' + + g3 + g2 + g1 + g0 + b3 + b2 + b1 + b0 + + a3 + a2 + a1 + a0 + r3 + r2 + r1 + r0 + + + V4L2_PIX_FMT_RGB555 + 'RGBO' + + g2 + g1 + g0 + r4 + r3 + r2 + r1 + r0 + + a + b4 + b3 + b2 + b1 + b0 + g4 + g3 + + + V4L2_PIX_FMT_RGB565 + 'RGBP' + + g2 + g1 + g0 + r4 + r3 + r2 + r1 + r0 + + b4 + b3 + b2 + b1 + b0 + g5 + g4 + g3 + + + V4L2_PIX_FMT_RGB555X + 'RGBQ' + + a + b4 + b3 + b2 + b1 + b0 + g4 + g3 + + g2 + g1 + g0 + r4 + r3 + r2 + r1 + r0 + + + V4L2_PIX_FMT_RGB565X + 'RGBR' + + b4 + b3 + b2 + b1 + b0 + g5 + g4 + g3 + + g2 + g1 + g0 + r4 + r3 + r2 + r1 + r0 + + + V4L2_PIX_FMT_BGR24 + 'BGR3' + + b7 + b6 + b5 + b4 + b3 + b2 + b1 + b0 + + g7 + g6 + g5 + g4 + g3 + g2 + g1 + g0 + + r7 + r6 + r5 + r4 + r3 + r2 + r1 + r0 + + + V4L2_PIX_FMT_RGB24 + 'RGB3' + + r7 + r6 + r5 + r4 + r3 + r2 + r1 + r0 + + g7 + g6 + g5 + g4 + g3 + g2 + g1 + g0 + + b7 + b6 + b5 + b4 + b3 + b2 + b1 + b0 + + + V4L2_PIX_FMT_BGR32 + 'BGR4' + + b7 + b6 + b5 + b4 + b3 + b2 + b1 + b0 + + g7 + g6 + g5 + g4 + g3 + g2 + g1 + g0 + + r7 + r6 + r5 + r4 + r3 + r2 + r1 + r0 + + a7 + a6 + a5 + a4 + a3 + a2 + a1 + a0 + + + V4L2_PIX_FMT_RGB32 + 'RGB4' + + r7 + r6 + r5 + r4 + r3 + r2 + r1 + r0 + + g7 + g6 + g5 + g4 + g3 + g2 + g1 + g0 + + b7 + b6 + b5 + b4 + b3 + b2 + b1 + b0 + + a7 + a6 + a5 + a4 + a3 + a2 + a1 + a0 + + + +
+ + Bit 7 is the most significant bit. The value of a = alpha +bits is undefined when reading from the driver, ignored when writing +to the driver, except when alpha blending has been negotiated for a +Video Overlay or Video Output Overlay. + + + <constant>V4L2_PIX_FMT_BGR24</constant> 4 × 4 pixel +image + + + Byte Order. + Each cell is one byte. + + + + + + start + 0: + B00 + G00 + R00 + B01 + G01 + R01 + B02 + G02 + R02 + B03 + G03 + R03 + + + start + 12: + B10 + G10 + R10 + B11 + G11 + R11 + B12 + G12 + R12 + B13 + G13 + R13 + + + start + 24: + B20 + G20 + R20 + B21 + G21 + R21 + B22 + G22 + R22 + B23 + G23 + R23 + + + start + 36: + B30 + G30 + R30 + B31 + G31 + R31 + B32 + G32 + R32 + B33 + G33 + R33 + + + + + + + + + + Drivers may interpret these formats differently. + + + Some RGB formats above are uncommon and were probably +defined in error. Drivers may interpret them as in . + + + Packed RGB Image Formats (corrected) + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + Identifier + Code +   + Byte 0 in memory + Byte 1 + Byte 2 + Byte 3 + + +   +   + Bit + 7 + 6 + 5 + 4 + 3 + 2 + 1 + 0 +   + 7 + 6 + 5 + 4 + 3 + 2 + 1 + 0 +   + 7 + 6 + 5 + 4 + 3 + 2 + 1 + 0 +   + 7 + 6 + 5 + 4 + 3 + 2 + 1 + 0 + + + + + V4L2_PIX_FMT_RGB332 + 'RGB1' + + r2 + r1 + r0 + g2 + g1 + g0 + b1 + b0 + + + V4L2_PIX_FMT_RGB444 + 'R444' + + g3 + g2 + g1 + g0 + b3 + b2 + b1 + b0 + + a3 + a2 + a1 + a0 + r3 + r2 + r1 + r0 + + + V4L2_PIX_FMT_RGB555 + 'RGBO' + + g2 + g1 + g0 + b4 + b3 + b2 + b1 + b0 + + a + r4 + r3 + r2 + r1 + r0 + g4 + g3 + + + V4L2_PIX_FMT_RGB565 + 'RGBP' + + g2 + g1 + g0 + b4 + b3 + b2 + b1 + b0 + + r4 + r3 + r2 + r1 + r0 + g5 + g4 + g3 + + + V4L2_PIX_FMT_RGB555X + 'RGBQ' + + a + r4 + r3 + r2 + r1 + r0 + g4 + g3 + + g2 + g1 + g0 + b4 + b3 + b2 + b1 + b0 + + + V4L2_PIX_FMT_RGB565X + 'RGBR' + + r4 + r3 + r2 + r1 + r0 + g5 + g4 + g3 + + g2 + g1 + g0 + b4 + b3 + b2 + b1 + b0 + + + V4L2_PIX_FMT_BGR24 + 'BGR3' + + b7 + b6 + b5 + b4 + b3 + b2 + b1 + b0 + + g7 + g6 + g5 + g4 + g3 + g2 + g1 + g0 + + r7 + r6 + r5 + r4 + r3 + r2 + r1 + r0 + + + V4L2_PIX_FMT_RGB24 + 'RGB3' + + r7 + r6 + r5 + r4 + r3 + r2 + r1 + r0 + + g7 + g6 + g5 + g4 + g3 + g2 + g1 + g0 + + b7 + b6 + b5 + b4 + b3 + b2 + b1 + b0 + + + V4L2_PIX_FMT_BGR32 + 'BGR4' + + b7 + b6 + b5 + b4 + b3 + b2 + b1 + b0 + + g7 + g6 + g5 + g4 + g3 + g2 + g1 + g0 + + r7 + r6 + r5 + r4 + r3 + r2 + r1 + r0 + + a7 + a6 + a5 + a4 + a3 + a2 + a1 + a0 + + + V4L2_PIX_FMT_RGB32 + 'RGB4' + + a7 + a6 + a5 + a4 + a3 + a2 + a1 + a0 + + r7 + r6 + r5 + r4 + r3 + r2 + r1 + r0 + + g7 + g6 + g5 + g4 + g3 + g2 + g1 + g0 + + b7 + b6 + b5 + b4 + b3 + b2 + b1 + b0 + + + +
+ + A test utility to determine which RGB formats a driver +actually supports is available from the LinuxTV v4l-dvb repository. +See &v4l-dvb; for access instructions. + + + + + diff --git a/v4l2-spec/pixfmt-packed-yuv.sgml b/v4l2-spec/pixfmt-packed-yuv.sgml new file mode 100644 index 000000000..7ad8d924a --- /dev/null +++ b/v4l2-spec/pixfmt-packed-yuv.sgml @@ -0,0 +1,244 @@ + + + Packed YUV formats + &manvol; + + + Packed YUV formats + Packed YUV formats + + + Description + + Similar to the packed RGB formats these formats store +the Y, Cb and Cr component of each pixel in one 16 or 32 bit +word. + + + Packed YUV Image Formats + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + Identifier + Code +   + Byte 0 in memory + Byte 1 + Byte 2 + Byte 3 + + +   +   + Bit + 7 + 6 + 5 + 4 + 3 + 2 + 1 + 0 +   + 7 + 6 + 5 + 4 + 3 + 2 + 1 + 0 +   + 7 + 6 + 5 + 4 + 3 + 2 + 1 + 0 +   + 7 + 6 + 5 + 4 + 3 + 2 + 1 + 0 + + + + + V4L2_PIX_FMT_YUV444 + 'Y444' + + Cb3 + Cb2 + Cb1 + Cb0 + Cr3 + Cr2 + Cr1 + Cr0 + + a3 + a2 + a1 + a0 + Y'3 + Y'2 + Y'1 + Y'0 + + + + V4L2_PIX_FMT_YUV555 + 'YUVO' + + Cb2 + Cb1 + Cb0 + Cr4 + Cr3 + Cr2 + Cr1 + Cr0 + + a + Y'4 + Y'3 + Y'2 + Y'1 + Y'0 + Cb4 + Cb3 + + + + V4L2_PIX_FMT_YUV565 + 'YUVP' + + Cb2 + Cb1 + Cb0 + Cr4 + Cr3 + Cr2 + Cr1 + Cr0 + + Y'4 + Y'3 + Y'2 + Y'1 + Y'0 + Cb5 + Cb4 + Cb3 + + + + V4L2_PIX_FMT_YUV32 + 'YUV4' + + a7 + a6 + a5 + a4 + a3 + a2 + a1 + a0 + + Y'7 + Y'6 + Y'5 + Y'4 + Y'3 + Y'2 + Y'1 + Y'0 + + Cb7 + Cb6 + Cb5 + Cb4 + Cb3 + Cb2 + Cb1 + Cb0 + + Cr7 + Cr6 + Cr5 + Cr4 + Cr3 + Cr2 + Cr1 + Cr0 + + + +
+ + Bit 7 is the most significant bit. The value of a = alpha +bits is undefined when reading from the driver, ignored when writing +to the driver, except when alpha blending has been negotiated for a +Video Overlay or Video Output Overlay. + + + + + diff --git a/v4l2-spec/pixfmt-sbggr16.sgml b/v4l2-spec/pixfmt-sbggr16.sgml new file mode 100644 index 000000000..262a20c12 --- /dev/null +++ b/v4l2-spec/pixfmt-sbggr16.sgml @@ -0,0 +1,91 @@ + + + V4L2_PIX_FMT_SBGGR16 ('BA82') + &manvol; + + + V4L2_PIX_FMT_SBGGR16 + Bayer RGB format + + + Description + + This format is similar to +V4L2_PIX_FMT_SBGGR8, except each pixel has +a depth of 16 bits. The least significant byte is stored at lower +memory addresses (little-endian). Note the actual sampling precision +may be lower than 16 bits, for example 10 bits per pixel with values +in range 0 to 1023. + + + <constant>V4L2_PIX_FMT_SBGGR16</constant> 4 × 4 +pixel image + + + Byte Order. + Each cell is one byte. + + + + + + start + 0: + B00low + B00high + G01low + G01high + B02low + B02high + G03low + G03high + + + start + 8: + G10low + G10high + R11low + R11high + G12low + G12high + R13low + R13high + + + start + 16: + B20low + B20high + G21low + G21high + B22low + B22high + G23low + G23high + + + start + 24: + G30low + G30high + R31low + R31high + G32low + G32high + R33low + R33high + + + + + + + + + + + diff --git a/v4l2-spec/pixfmt-sbggr8.sgml b/v4l2-spec/pixfmt-sbggr8.sgml new file mode 100644 index 000000000..37805fe11 --- /dev/null +++ b/v4l2-spec/pixfmt-sbggr8.sgml @@ -0,0 +1,75 @@ + + + V4L2_PIX_FMT_SBGGR8 ('BA81') + &manvol; + + + V4L2_PIX_FMT_SBGGR8 + Bayer RGB format + + + Description + + This is commonly the native format of digital cameras, +reflecting the arrangement of sensors on the CCD device. Only one red, +green or blue value is given for each pixel. Missing components must +be interpolated from neighbouring pixels. From left to right the first +row consists of a blue and green value, the second row of a green and +red value. This scheme repeats to the right and down for every two +columns and rows. + + + <constant>V4L2_PIX_FMT_SBGGR8</constant> 4 × 4 +pixel image + + + Byte Order. + Each cell is one byte. + + + + + + start + 0: + B00 + G01 + B02 + G03 + + + start + 4: + G10 + R11 + G12 + R13 + + + start + 8: + B20 + G21 + B22 + G23 + + + start + 12: + G30 + R31 + G32 + R33 + + + + + + + + + + + diff --git a/v4l2-spec/pixfmt-uyvy.sgml b/v4l2-spec/pixfmt-uyvy.sgml new file mode 100644 index 000000000..4c33e06cc --- /dev/null +++ b/v4l2-spec/pixfmt-uyvy.sgml @@ -0,0 +1,128 @@ + + + V4L2_PIX_FMT_UYVY ('UYVY') + &manvol; + + + V4L2_PIX_FMT_UYVY + Variation of +V4L2_PIX_FMT_YUYV with different order of samples +in memory + + + Description + + In this format each four bytes is two pixels. Each four +bytes is two Y's, a Cb and a Cr. Each Y goes to one of the pixels, and +the Cb and Cr belong to both pixels. As you can see, the Cr and Cb +components have half the horizontal resolution of the Y +component. + + + <constant>V4L2_PIX_FMT_UYVY</constant> 4 × 4 +pixel image + + + Byte Order. + Each cell is one byte. + + + + + + start + 0: + Cb00 + Y'00 + Cr00 + Y'01 + Cb01 + Y'02 + Cr01 + Y'03 + + + start + 8: + Cb10 + Y'10 + Cr10 + Y'11 + Cb11 + Y'12 + Cr11 + Y'13 + + + start + 16: + Cb20 + Y'20 + Cr20 + Y'21 + Cb21 + Y'22 + Cr21 + Y'23 + + + start + 24: + Cb30 + Y'30 + Cr30 + Y'31 + Cb31 + Y'32 + Cr31 + Y'33 + + + + + + + + + Color Sample Location. + + + + + + + 01 + 23 + + + 0 + YCY + YCY + + + 1 + YCY + YCY + + + 2 + YCY + YCY + + + 3 + YCY + YCY + + + + + + + + + + + diff --git a/v4l2-spec/pixfmt-y16.sgml b/v4l2-spec/pixfmt-y16.sgml new file mode 100644 index 000000000..98a550b19 --- /dev/null +++ b/v4l2-spec/pixfmt-y16.sgml @@ -0,0 +1,89 @@ + + + V4L2_PIX_FMT_Y16 ('Y16 ') + &manvol; + + + V4L2_PIX_FMT_Y16 + Grey-scale image + + + Description + + This is a grey-scale image with a depth of 16 bits per +pixel. The least significant byte is stored at lower memory addresses +(little-endian). Note the actual sampling precision may be lower than +16 bits, for example 10 bits per pixel with values in range 0 to +1023. + + + <constant>V4L2_PIX_FMT_Y16</constant> 4 × 4 +pixel image + + + Byte Order. + Each cell is one byte. + + + + + + start + 0: + Y'00low + Y'00high + Y'01low + Y'01high + Y'02low + Y'02high + Y'03low + Y'03high + + + start + 8: + Y'10low + Y'10high + Y'11low + Y'11high + Y'12low + Y'12high + Y'13low + Y'13high + + + start + 16: + Y'20low + Y'20high + Y'21low + Y'21high + Y'22low + Y'22high + Y'23low + Y'23high + + + start + 24: + Y'30low + Y'30high + Y'31low + Y'31high + Y'32low + Y'32high + Y'33low + Y'33high + + + + + + + + + + + diff --git a/v4l2-spec/pixfmt-y41p.sgml b/v4l2-spec/pixfmt-y41p.sgml new file mode 100644 index 000000000..c18aae440 --- /dev/null +++ b/v4l2-spec/pixfmt-y41p.sgml @@ -0,0 +1,157 @@ + + + V4L2_PIX_FMT_Y41P ('Y41P') + &manvol; + + + V4L2_PIX_FMT_Y41P + Format with ¼ horizontal chroma +resolution, also known as YUV 4:1:1 + + + Description + + In this format each 12 bytes is eight pixels. In the +twelve bytes are two CbCr pairs and eight Y's. The first CbCr pair +goes with the first four Y's, and the second CbCr pair goes with the +other four Y's. The Cb and Cr components have one fourth the +horizontal resolution of the Y component. + + Do not confuse this format with V4L2_PIX_FMT_YUV411P. +Y41P is derived from "YUV 4:1:1 packed", while +YUV411P stands for "YUV 4:1:1 planar". + + + <constant>V4L2_PIX_FMT_Y41P</constant> 8 × 4 +pixel image + + + Byte Order + Each cell is one byte. + + + + + + start + 0: + Cb00 + Y'00 + Cr00 + Y'01 + Cb01 + Y'02 + Cr01 + Y'03 + Y'04 + Y'05 + Y'06 + Y'07 + + + start + 12: + Cb10 + Y'10 + Cr10 + Y'11 + Cb11 + Y'12 + Cr11 + Y'13 + Y'14 + Y'15 + Y'16 + Y'17 + + + start + 24: + Cb20 + Y'20 + Cr20 + Y'21 + Cb21 + Y'22 + Cr21 + Y'23 + Y'24 + Y'25 + Y'26 + Y'27 + + + start + 36: + Cb30 + Y'30 + Cr30 + Y'31 + Cb31 + Y'32 + Cr31 + Y'33 + Y'34 + Y'35 + Y'36 + Y'37 + + + + + + + + Color Sample Location. + + + + + + + 01 + 23 + 45 + 67 + + + 0 + YYC + YY + YYC + YY + + + 1 + YYC + YY + YYC + YY + + + 2 + YYC + YY + YYC + YY + + + 3 + YYC + YY + YYC + YY + + + + + + + + + + + diff --git a/v4l2-spec/pixfmt-yuv410.sgml b/v4l2-spec/pixfmt-yuv410.sgml new file mode 100644 index 000000000..fb989204c --- /dev/null +++ b/v4l2-spec/pixfmt-yuv410.sgml @@ -0,0 +1,141 @@ + + + V4L2_PIX_FMT_YVU410 ('YVU9'), V4L2_PIX_FMT_YUV410 ('YUV9') + &manvol; + + + V4L2_PIX_FMT_YVU410 + V4L2_PIX_FMT_YUV410 + Planar formats with ¼ horizontal and +vertical chroma resolution, also known as YUV 4:1:0 + + + Description + + These are planar formats, as opposed to a packed format. +The three components are separated into three sub-images or planes. +The Y plane is first. The Y plane has one byte per pixel. For +V4L2_PIX_FMT_YVU410, the Cr plane immediately +follows the Y plane in memory. The Cr plane is ¼ the width and +¼ the height of the Y plane (and of the image). Each Cr belongs +to 16 pixels, a four-by-four square of the image. Following the Cr +plane is the Cb plane, just like the Cr plane. +V4L2_PIX_FMT_YUV410 is the same, except the Cb +plane comes first, then the Cr plane. + + If the Y plane has pad bytes after each row, then the Cr +and Cb planes have ¼ as many pad bytes after their rows. In +other words, four Cx rows (including padding) are exactly as long as +one Y row (including padding). + + + <constant>V4L2_PIX_FMT_YVU410</constant> 4 × 4 +pixel image + + + Byte Order. + Each cell is one byte. + + + + + + start + 0: + Y'00 + Y'01 + Y'02 + Y'03 + + + start + 4: + Y'10 + Y'11 + Y'12 + Y'13 + + + start + 8: + Y'20 + Y'21 + Y'22 + Y'23 + + + start + 12: + Y'30 + Y'31 + Y'32 + Y'33 + + + start + 16: + Cr00 + + + start + 17: + Cb00 + + + + + + + + + Color Sample Location. + + + + + + + 01 + 23 + + + 0 + YY + YY + + + + + + 1 + YY + YY + + + + C + + + + 2 + YY + YY + + + + + + 3 + YY + YY + + + + + + + + + + + diff --git a/v4l2-spec/pixfmt-yuv411p.sgml b/v4l2-spec/pixfmt-yuv411p.sgml new file mode 100644 index 000000000..8de4e8c94 --- /dev/null +++ b/v4l2-spec/pixfmt-yuv411p.sgml @@ -0,0 +1,155 @@ + + + V4L2_PIX_FMT_YUV411P ('411P') + &manvol; + + + V4L2_PIX_FMT_YUV411P + Format with ¼ horizontal chroma resolution, +also known as YUV 4:1:1. Planar layout as opposed to +V4L2_PIX_FMT_Y41P + + + Description + + This format is not commonly used. This is a planar +format similar to the 4:2:2 planar format except with half as many +chroma. The three components are separated into three sub-images or +planes. The Y plane is first. The Y plane has one byte per pixel. The +Cb plane immediately follows the Y plane in memory. The Cb plane is +¼ the width of the Y plane (and of the image). Each Cb belongs +to 4 pixels all on the same row. For example, +Cb0 belongs to Y'00, +Y'01, Y'02 and +Y'03. Following the Cb plane is the Cr plane, +just like the Cb plane. + + If the Y plane has pad bytes after each row, then the Cr +and Cb planes have ¼ as many pad bytes after their rows. In +other words, four C x rows (including padding) is exactly as long as +one Y row (including padding). + + + <constant>V4L2_PIX_FMT_YUV411P</constant> 4 × 4 +pixel image + + + Byte Order. + Each cell is one byte. + + + + + + start + 0: + Y'00 + Y'01 + Y'02 + Y'03 + + + start + 4: + Y'10 + Y'11 + Y'12 + Y'13 + + + start + 8: + Y'20 + Y'21 + Y'22 + Y'23 + + + start + 12: + Y'30 + Y'31 + Y'32 + Y'33 + + + start + 16: + Cb00 + + + start + 17: + Cb10 + + + start + 18: + Cb20 + + + start + 19: + Cb30 + + + start + 20: + Cr00 + + + start + 21: + Cr10 + + + start + 22: + Cr20 + + + start + 23: + Cr30 + + + + + + + + + Color Sample Location. + + + + + + + 01 + 23 + + + 0 + YYC + YY + + + 1 + YYC + YY + + + 2 + YYC + YY + + + 3 + YYC + YY + + + + + + + + + + + diff --git a/v4l2-spec/pixfmt-yuv420.sgml b/v4l2-spec/pixfmt-yuv420.sgml new file mode 100644 index 000000000..0b0b57cd5 --- /dev/null +++ b/v4l2-spec/pixfmt-yuv420.sgml @@ -0,0 +1,157 @@ + + + V4L2_PIX_FMT_YVU420 ('YV12'), V4L2_PIX_FMT_YUV420 ('YU12') + &manvol; + + + V4L2_PIX_FMT_YVU420 + V4L2_PIX_FMT_YUV420 + Planar formats with ½ horizontal and +vertical chroma resolution, also known as YUV 4:2:0 + + + Description + + These are planar formats, as opposed to a packed format. +The three components are separated into three sub- images or planes. +The Y plane is first. The Y plane has one byte per pixel. For +V4L2_PIX_FMT_YVU420, the Cr plane immediately +follows the Y plane in memory. The Cr plane is half the width and half +the height of the Y plane (and of the image). Each Cr belongs to four +pixels, a two-by-two square of the image. For example, +Cr0 belongs to Y'00, +Y'01, Y'10, and +Y'11. Following the Cr plane is the Cb plane, +just like the Cr plane. V4L2_PIX_FMT_YUV420 is +the same except the Cb plane comes first, then the Cr plane. + + If the Y plane has pad bytes after each row, then the Cr +and Cb planes have half as many pad bytes after their rows. In other +words, two Cx rows (including padding) is exactly as long as one Y row +(including padding). + + + <constant>V4L2_PIX_FMT_YVU420</constant> 4 × 4 +pixel image + + + Byte Order. + Each cell is one byte. + + + + + + start + 0: + Y'00 + Y'01 + Y'02 + Y'03 + + + start + 4: + Y'10 + Y'11 + Y'12 + Y'13 + + + start + 8: + Y'20 + Y'21 + Y'22 + Y'23 + + + start + 12: + Y'30 + Y'31 + Y'32 + Y'33 + + + start + 16: + Cr00 + Cr01 + + + start + 18: + Cr10 + Cr11 + + + start + 20: + Cb00 + Cb01 + + + start + 22: + Cb10 + Cb11 + + + + + + + + + Color Sample Location. + + + + + + + 01 + 23 + + + 0 + YY + YY + + + + C + C + + + 1 + YY + YY + + + + + + 2 + YY + YY + + + + C + C + + + 3 + YY + YY + + + + + + + + + + + diff --git a/v4l2-spec/pixfmt-yuv422p.sgml b/v4l2-spec/pixfmt-yuv422p.sgml new file mode 100644 index 000000000..5a295eb0d --- /dev/null +++ b/v4l2-spec/pixfmt-yuv422p.sgml @@ -0,0 +1,161 @@ + + + V4L2_PIX_FMT_YUV422P ('422P') + &manvol; + + + V4L2_PIX_FMT_YUV422P + Format with ½ horizontal chroma resolution, +also known as YUV 4:2:2. Planar layout as opposed to +V4L2_PIX_FMT_YUYV + + + Description + + This format is not commonly used. This is a planar +version of the YUYV format. The three components are separated into +three sub-images or planes. The Y plane is first. The Y plane has one +byte per pixel. The Cb plane immediately follows the Y plane in +memory. The Cb plane is half the width of the Y plane (and of the +image). Each Cb belongs to two pixels. For example, +Cb0 belongs to Y'00, +Y'01. Following the Cb plane is the Cr plane, +just like the Cb plane. + + If the Y plane has pad bytes after each row, then the Cr +and Cb planes have half as many pad bytes after their rows. In other +words, two Cx rows (including padding) is exactly as long as one Y row +(including padding). + + + <constant>V4L2_PIX_FMT_YUV422P</constant> 4 × 4 +pixel image + + + Byte Order. + Each cell is one byte. + + + + + + start + 0: + Y'00 + Y'01 + Y'02 + Y'03 + + + start + 4: + Y'10 + Y'11 + Y'12 + Y'13 + + + start + 8: + Y'20 + Y'21 + Y'22 + Y'23 + + + start + 12: + Y'30 + Y'31 + Y'32 + Y'33 + + + start + 16: + Cb00 + Cb01 + + + start + 18: + Cb10 + Cb11 + + + start + 20: + Cb20 + Cb21 + + + start + 22: + Cb30 + Cb31 + + + start + 24: + Cr00 + Cr01 + + + start + 26: + Cr10 + Cr11 + + + start + 28: + Cr20 + Cr21 + + + start + 30: + Cr30 + Cr31 + + + + + + + + + Color Sample Location. + + + + + + + 01 + 23 + + + 0 + YCY + YCY + + + 1 + YCY + YCY + + + 2 + YCY + YCY + + + 3 + YCY + YCY + + + + + + + + + + + diff --git a/v4l2-spec/pixfmt-yuyv.sgml b/v4l2-spec/pixfmt-yuyv.sgml new file mode 100644 index 000000000..4f083b3be --- /dev/null +++ b/v4l2-spec/pixfmt-yuyv.sgml @@ -0,0 +1,128 @@ + + + V4L2_PIX_FMT_YUYV ('YUYV') + &manvol; + + + V4L2_PIX_FMT_YUYV + Packed format with ½ horizontal chroma +resolution, also known as YUV 4:2:2 + + + Description + + In this format each four bytes is two pixels. Each four +bytes is two Y's, a Cb and a Cr. Each Y goes to one of the pixels, and +the Cb and Cr belong to both pixels. As you can see, the Cr and Cb +components have half the horizontal resolution of the Y component. +V4L2_PIX_FMT_YUYV is known in the Windows +environment as YUY2. + + + <constant>V4L2_PIX_FMT_YUYV</constant> 4 × 4 +pixel image + + + Byte Order. + Each cell is one byte. + + + + + start + 0: + Y'00 + Cb00 + Y'01 + Cr00 + Y'02 + Cb01 + Y'03 + Cr01 + + + start + 8: + Y'10 + Cb10 + Y'11 + Cr10 + Y'12 + Cb11 + Y'13 + Cr11 + + + start + 16: + Y'20 + Cb20 + Y'21 + Cr20 + Y'22 + Cb21 + Y'23 + Cr21 + + + start + 24: + Y'30 + Cb30 + Y'31 + Cr30 + Y'32 + Cb31 + Y'33 + Cr31 + + + + + + + + + Color Sample Location. + + + + + + + 01 + 23 + + + 0 + YCY + YCY + + + 1 + YCY + YCY + + + 2 + YCY + YCY + + + 3 + YCY + YCY + + + + + + + + + + + diff --git a/v4l2-spec/pixfmt.sgml b/v4l2-spec/pixfmt.sgml new file mode 100644 index 000000000..10bf435e0 --- /dev/null +++ b/v4l2-spec/pixfmt.sgml @@ -0,0 +1,728 @@ + Image Formats + + The V4L2 API was primarily designed for devices exchanging +image data with applications. The +v4l2_pix_format structure defines the format +and layout of an image in memory. Image formats are negotiated with +the &VIDIOC-S-FMT; ioctl. (The explanations here focus on video +capturing and output, for overlay frame buffer formats see also +&VIDIOC-G-FBUF;.) + + + struct <structname>v4l2_pix_format</structname> + + &cs-str; + + + __u32 + width + Image width in pixels. + + + __u32 + height + Image height in pixels. + + + Applications set these fields to +request an image size, drivers return the closest possible values. In +case of planar formats the width and +height applies to the largest plane. To +avoid ambiguities drivers must return values rounded up to a multiple +of the scale factor of any smaller planes. For example when the image +format is YUV 4:2:0, width and +height must be multiples of two. + + + __u32 + pixelformat + The pixel format or type of compression, set by the +application. This is a little endian four character code. V4L2 defines +standard RGB formats in , YUV formats in , and reserved codes in + + + &v4l2-field; + field + Video images are typically interlaced. Applications +can request to capture or output only the top or bottom field, or both +fields interlaced or sequentially stored in one buffer or alternating +in separate buffers. Drivers return the actual field order selected. +For details see . + + + __u32 + bytesperline + Distance in bytes between the leftmost pixels in two +adjacent lines. + + + Both applications and drivers +can set this field to request padding bytes at the end of each line. +Drivers however may ignore the value requested by the application, +returning width times bytes per pixel or a +larger value required by the hardware. That implies applications can +just set this field to zero to get a reasonable +default.Video hardware may access padding bytes, +therefore they must reside in accessible memory. Consider cases where +padding bytes after the last line of an image cross a system page +boundary. Input devices may write padding bytes, the value is +undefined. Output devices ignore the contents of padding +bytes.When the image format is planar the +bytesperline value applies to the largest +plane and is divided by the same factor as the +width field for any smaller planes. For +example the Cb and Cr planes of a YUV 4:2:0 image have half as many +padding bytes following each line as the Y plane. To avoid ambiguities +drivers must return a bytesperline value +rounded up to a multiple of the scale factor. + + + __u32 + sizeimage + Size in bytes of the buffer to hold a complete image, +set by the driver. Usually this is +bytesperline times +height. When the image consists of variable +length compressed data this is the maximum number of bytes required to +hold an image. + + + &v4l2-colorspace; + colorspace + This information supplements the +pixelformat and must be set by the driver, +see . + + + __u32 + priv + Reserved for custom (driver defined) additional +information about formats. When not used drivers and applications must +set this field to zero. + + + +
+ +
+ Standard Image Formats + + In order to exchange images between drivers and +applications, it is necessary to have standard image data formats +which both sides will interpret the same way. V4L2 includes several +such formats, and this section is intended to be an unambiguous +specification of the standard image data formats in V4L2. + + V4L2 drivers are not limited to these formats, however. +Driver-specific formats are possible. In that case the application may +depend on a codec to convert images to one of the standard formats +when needed. But the data can still be stored and retrieved in the +proprietary format. For example, a device may support a proprietary +compressed format. Applications can still capture and save the data in +the compressed format, saving much disk space, and later use a codec +to convert the images to the X Windows screen format when the video is +to be displayed. + + Even so, ultimately, some standard formats are needed, so +the V4L2 specification would not be complete without well-defined +standard formats. + + The V4L2 standard formats are mainly uncompressed formats. The +pixels are always arranged in memory from left to right, and from top +to bottom. The first byte of data in the image buffer is always for +the leftmost pixel of the topmost row. Following that is the pixel +immediately to its right, and so on until the end of the top row of +pixels. Following the rightmost pixel of the row there may be zero or +more bytes of padding to guarantee that each row of pixel data has a +certain alignment. Following the pad bytes, if any, is data for the +leftmost pixel of the second row from the top, and so on. The last row +has just as many pad bytes after it as the other rows. + + In V4L2 each format has an identifier which looks like +PIX_FMT_XXX, defined in the videodev.h header file. These identifiers +represent four character codes +which are also listed below, however they are not the same as those +used in the Windows world. +
+ +
+ Colorspaces + + [intro] + + + + + + + Gamma Correction + + [to do] + E'R = f(R) + E'G = f(G) + E'B = f(B) + + + + Construction of luminance and color-difference +signals + + [to do] + E'Y = +CoeffR E'R ++ CoeffG E'G ++ CoeffB E'B + (E'R - E'Y) = E'R +- CoeffR E'R +- CoeffG E'G +- CoeffB E'B + (E'B - E'Y) = E'B +- CoeffR E'R +- CoeffG E'G +- CoeffB E'B + + + + Re-normalized color-difference signals + + The color-difference signals are scaled back to unity +range [-0.5;+0.5]: + KB = 0.5 / (1 - CoeffB) + KR = 0.5 / (1 - CoeffR) + PB = +KB (E'B - E'Y) = + 0.5 (CoeffR / CoeffB) E'R ++ 0.5 (CoeffG / CoeffB) E'G ++ 0.5 E'B + PR = +KR (E'R - E'Y) = + 0.5 E'R ++ 0.5 (CoeffG / CoeffR) E'G ++ 0.5 (CoeffB / CoeffR) E'B + + + + Quantization + + [to do] + Y' = (Lum. Levels - 1) · E'Y + Lum. Offset + CB = (Chrom. Levels - 1) +· PB + Chrom. Offset + CR = (Chrom. Levels - 1) +· PR + Chrom. Offset + Rounding to the nearest integer and clamping to the range +[0;255] finally yields the digital color components Y'CbCr +stored in YUV images. + + + + + + + ITU-R Rec. BT.601 color conversion + + Forward Transformation + + +int ER, EG, EB; /* gamma corrected RGB input [0;255] */ +int Y1, Cb, Cr; /* output [0;255] */ + +double r, g, b; /* temporaries */ +double y1, pb, pr; + +int +clamp (double x) +{ + int r = x; /* round to nearest */ + + if (r < 0) return 0; + else if (r > 255) return 255; + else return r; +} + +r = ER / 255.0; +g = EG / 255.0; +b = EB / 255.0; + +y1 = 0.299 * r + 0.587 * g + 0.114 * b; +pb = -0.169 * r - 0.331 * g + 0.5 * b; +pr = 0.5 * r - 0.419 * g - 0.081 * b; + +Y1 = clamp (219 * y1 + 16); +Cb = clamp (224 * pb + 128); +Cr = clamp (224 * pr + 128); + +/* or shorter */ + +y1 = 0.299 * ER + 0.587 * EG + 0.114 * EB; + +Y1 = clamp ( (219 / 255.0) * y1 + 16); +Cb = clamp (((224 / 255.0) / (2 - 2 * 0.114)) * (EB - y1) + 128); +Cr = clamp (((224 / 255.0) / (2 - 2 * 0.299)) * (ER - y1) + 128); + + + Inverse Transformation + + +int Y1, Cb, Cr; /* gamma pre-corrected input [0;255] */ +int ER, EG, EB; /* output [0;255] */ + +double r, g, b; /* temporaries */ +double y1, pb, pr; + +int +clamp (double x) +{ + int r = x; /* round to nearest */ + + if (r < 0) return 0; + else if (r > 255) return 255; + else return r; +} + +y1 = (255 / 219.0) * (Y1 - 16); +pb = (255 / 224.0) * (Cb - 128); +pr = (255 / 224.0) * (Cr - 128); + +r = 1.0 * y1 + 0 * pb + 1.402 * pr; +g = 1.0 * y1 - 0.344 * pb - 0.714 * pr; +b = 1.0 * y1 + 1.772 * pb + 0 * pr; + +ER = clamp (r * 255); /* [ok? one should prob. limit y1,pb,pr] */ +EG = clamp (g * 255); +EB = clamp (b * 255); + + + + + enum v4l2_colorspace + + + + + + + + + + + + + + + + + + Identifier + Value + Description + Chromaticities + The coordinates of the color primaries are +given in the CIE system (1931) + + White Point + Gamma Correction + Luminance E'Y + Quantization + + + Red + Green + Blue + Y' + Cb, Cr + + + + + V4L2_COLORSPACE_SMPTE170M + 1 + NTSC/PAL according to , + + x = 0.630, y = 0.340 + x = 0.310, y = 0.595 + x = 0.155, y = 0.070 + x = 0.3127, y = 0.3290, + Illuminant D65 + E' = 4.5 I for I ≤0.018, +1.099 I0.45 - 0.099 for 0.018 < I + 0.299 E'R ++ 0.587 E'G ++ 0.114 E'B + 219 E'Y + 16 + 224 PB,R + 128 + + + V4L2_COLORSPACE_SMPTE240M + 2 + 1125-Line (US) HDTV, see + x = 0.630, y = 0.340 + x = 0.310, y = 0.595 + x = 0.155, y = 0.070 + x = 0.3127, y = 0.3290, + Illuminant D65 + E' = 4 I for I ≤0.0228, +1.1115 I0.45 - 0.1115 for 0.0228 < I + 0.212 E'R ++ 0.701 E'G ++ 0.087 E'B + 219 E'Y + 16 + 224 PB,R + 128 + + + V4L2_COLORSPACE_REC709 + 3 + HDTV and modern devices, see + x = 0.640, y = 0.330 + x = 0.300, y = 0.600 + x = 0.150, y = 0.060 + x = 0.3127, y = 0.3290, + Illuminant D65 + E' = 4.5 I for I ≤0.018, +1.099 I0.45 - 0.099 for 0.018 < I + 0.2125 E'R ++ 0.7154 E'G ++ 0.0721 E'B + 219 E'Y + 16 + 224 PB,R + 128 + + + V4L2_COLORSPACE_BT878 + 4 + Broken Bt878 extents + The ubiquitous Bt878 video capture chip +quantizes E'Y to 238 levels, yielding a range +of Y' = 16 … 253, unlike Rec. 601 Y' = 16 … +235. This is not a typo in the Bt878 documentation, it has been +implemented in silicon. The chroma extents are unclear. + , + ? + ? + ? + ? + ? + 0.299 E'R ++ 0.587 E'G ++ 0.114 E'B + 237 E'Y + 16 + 224 PB,R + 128 (probably) + + + V4L2_COLORSPACE_470_SYSTEM_M + 5 + M/NTSC + No identifier exists for M/PAL which uses +the chromaticities of M/NTSC, the remaining parameters are equal to B and +G/PAL. + according to , + x = 0.67, y = 0.33 + x = 0.21, y = 0.71 + x = 0.14, y = 0.08 + x = 0.310, y = 0.316, Illuminant C + ? + 0.299 E'R ++ 0.587 E'G ++ 0.114 E'B + 219 E'Y + 16 + 224 PB,R + 128 + + + V4L2_COLORSPACE_470_SYSTEM_BG + 6 + 625-line PAL and SECAM systems according to , + x = 0.64, y = 0.33 + x = 0.29, y = 0.60 + x = 0.15, y = 0.06 + x = 0.313, y = 0.329, +Illuminant D65 + ? + 0.299 E'R ++ 0.587 E'G ++ 0.114 E'B + 219 E'Y + 16 + 224 PB,R + 128 + + + V4L2_COLORSPACE_JPEG + 7 + JPEG Y'CbCr, see , + ? + ? + ? + ? + ? + 0.299 E'R ++ 0.587 E'G ++ 0.114 E'B + 256 E'Y + 16 + Note JFIF quantizes +Y'PBPR in range [0;+1] and +[-0.5;+0.5] to 257 levels, however Y'CbCr signals +are still clamped to [0;255]. + + 256 PB,R + 128 + + + V4L2_COLORSPACE_SRGB + 8 + [?] + x = 0.640, y = 0.330 + x = 0.300, y = 0.600 + x = 0.150, y = 0.060 + x = 0.3127, y = 0.3290, + Illuminant D65 + E' = 4.5 I for I ≤0.018, +1.099 I0.45 - 0.099 for 0.018 < I + n/a + + + +
+
+ +
+ Indexed Format + + In this format each pixel is represented by an 8 bit index +into a 256 entry ARGB palette. It is intended for Video Output Overlays only. There are no ioctls to +access the palette, this must be done with ioctls of the Linux framebuffer API. + + + Indexed Image Format + + + + + + + + + + + + + + + + + + + + + Identifier + Code +   + Byte 0 + + +   +   + Bit + 7 + 6 + 5 + 4 + 3 + 2 + 1 + 0 + + + + + V4L2_PIX_FMT_PAL8 + 'PAL8' + + i7 + i6 + i5 + i4 + i3 + i2 + i1 + i0 + + + +
+
+ +
+ RGB Formats + + &sub-packed-rgb; + &sub-sbggr8; + &sub-sbggr16; +
+ +
+ YUV Formats + + YUV is the format native to TV broadcast and composite video +signals. It separates the brightness information (Y) from the color +information (U and V or Cb and Cr). The color information consists of +red and blue color difference signals, this way +the green component can be reconstructed by subtracting from the +brightness component. See for conversion +examples. YUV was chosen because early television would only transmit +brightness information. To add color in a way compatible with existing +receivers a new signal carrier was added to transmit the color +difference signals. Secondary in the YUV format the U and V components +usually have lower resolution than the Y component. This is an analog +video compression technique taking advantage of a property of the +human visual system, being more sensitive to brightness +information. + + &sub-packed-yuv; + &sub-grey; + &sub-y16; + &sub-yuyv; + &sub-uyvy; + &sub-y41p; + &sub-yuv420; + &sub-yuv410; + &sub-yuv422p; + &sub-yuv411p; + &sub-nv12; +
+ +
+ Compressed Formats + + + Compressed Image Formats + + &cs-def; + + + Identifier + Code + Details + + + + + V4L2_PIX_FMT_JPEG + 'JPEG' + TBD. See also &VIDIOC-G-JPEGCOMP;, + &VIDIOC-S-JPEGCOMP;. + + + V4L2_PIX_FMT_MPEG + 'MPEG' + MPEG stream. The actual format is determined by +extended control V4L2_CID_MPEG_STREAM_TYPE, see +. + + + +
+
+ +
+ Reserved Format Identifiers + + These formats are not defined by this specification, they +are just listed for reference and to avoid naming conflicts. If you +want to register your own format, send an e-mail to the V4L mailing +list &v4l-ml; for inclusion in the videodev.h +file. If you want to share your format with other developers add a +link to your documentation and send a copy to the maintainer of this +document, Michael Schimek mschimek@gmx.at, for +inclusion in this section. If you think your format should be listed +in a standard format section please make a proposal on the V4L mailing +list. + + + Reserved Image Formats + + &cs-def; + + + Identifier + Code + Details + + + + + V4L2_PIX_FMT_DV + 'dvsd' + unknown + + + V4L2_PIX_FMT_ET61X251 + 'E625' + Compressed format of the ET61X251 driver. + + + V4L2_PIX_FMT_HI240 + 'HI24' + 8 bit RGB format used by the BTTV driver, +http://bytesex.org/bttv/ + + + V4L2_PIX_FMT_HM12 + 'HM12' + YUV 4:2:0 format used by the +IVTV driver, +http://www.ivtvdriver.org/The format is documented in the +kernel sources in the file Documentation/video4linux/cx2341x/README.hm12 + + + + V4L2_PIX_FMT_MJPEG + 'MJPG' + Compressed format used by the Zoran driver + + + V4L2_PIX_FMT_PWC1 + 'PWC1' + Compressed format of the PWC driver. + + + V4L2_PIX_FMT_PWC2 + 'PWC2' + Compressed format of the PWC driver. + + + V4L2_PIX_FMT_SN9C10X + 'S910' + Compressed format of the SN9C102 driver. + + + V4L2_PIX_FMT_WNVA + 'WNVA' + Used by the Winnov Videum driver, +http://www.thedirks.org/winnov/ + + + V4L2_PIX_FMT_YYUV + 'YYUV' + unknown + + + +
+
+ + diff --git a/v4l2-spec/v4l2.sgml b/v4l2-spec/v4l2.sgml new file mode 100644 index 000000000..710943aac --- /dev/null +++ b/v4l2-spec/v4l2.sgml @@ -0,0 +1,465 @@ + %entities; + + + + +open()."> +2C"> +Return ValueOn success 0 is returned, on error -1 and the errno variable is set appropriately:"> +2"> + + +"> +"> +"> + + +https://listman.redhat.com/mailman/listinfo/video4linux-list"> + + +http://linuxtv.org/repo/"> + +]> + + + + Video for Linux Two API Specification + Revision 0.24 + + + + Michael + Schimek + H + +
+ mschimek@gmx.at +
+ + + + + Bill + Dirks + + Original author of the V4L2 API and +documentation. + + + + Hans + Verkuil + + Designed and documented the VIDIOC_LOG_STATUS ioctl, +the extended control ioctls and major parts of the sliced VBI +API. + + + + Martin + Rubli + + Designed and documented the VIDIOC_ENUM_FRAMESIZES +and VIDIOC_ENUM_FRAMEINTERVALS ioctls. + + + + + 1999 + 2000 + 2001 + 2002 + 2003 + 2004 + 2005 + 2006 + 2007 + 2008 + Bill Dirks, Michael H. Schimek, Hans Verkuil, Martin +Rubli + + + + This document is copyrighted © 1999-2008 by Bill +Dirks, Michael H. Schimek, Hans Verkuil and Martin Rubli. + + Permission is granted to copy, distribute and/or modify +this document under the terms of the GNU Free Documentation License, +Version 1.1 or any later version published by the Free Software +Foundation; with no Invariant Sections, with no Front-Cover Texts, and +with no Back-Cover Texts. A copy of the license is included in the +appendix entitled "GNU Free Documentation License". + + Programming examples can be used and distributed without +restrictions. + + + + + + + + 0.24 + 2008-03-04 + mhs + Added pixel format Y16 and SBGGR16, new controls +and a camera controls class. Removed VIDIOC_G/S_MPEGCOMP. + + + + 0.23 + 2007-08-30 + mhs + Fixed a typo in VIDIOC_DBG_G/S_REGISTER. +Clarified the byte order of packed pixel formats. + + + + 0.22 + 2007-08-29 + mhs + Added the Video Output Overlay interface, new MPEG +controls, V4L2_FIELD_INTERLACED_TB and V4L2_FIELD_INTERLACED_BT, +VIDIOC_DBG_G/S_REGISTER, VIDIOC_(TRY_)ENCODER_CMD, +VIDIOC_G_CHIP_IDENT, VIDIOC_G_ENC_INDEX, new pixel formats. +Clarifications in the cropping chapter, about RGB pixel formats, the +mmap(), poll(), select(), read() and write() functions. Typographical +fixes. + + + + 0.21 + 2006-12-19 + mhs + Fixed a link in the VIDIOC_G_EXT_CTRLS section. + + + + 0.20 + 2006-11-24 + mhs + Clarified the purpose of the audioset field in +struct v4l2_input and v4l2_output. + + + + 0.19 + 2006-10-19 + mhs + Documented V4L2_PIX_FMT_RGB444. + + + + 0.18 + 2006-10-18 + mhs + Added the description of extended controls by Hans +Verkuil. Linked V4L2_PIX_FMT_MPEG to V4L2_CID_MPEG_STREAM_TYPE. + + + + 0.17 + 2006-10-12 + mhs + Corrected V4L2_PIX_FMT_HM12 description. + + + + 0.16 + 2006-10-08 + mhs + VIDIOC_ENUM_FRAMESIZES and +VIDIOC_ENUM_FRAMEINTERVALS are now part of the API. + + + + 0.15 + 2006-09-23 + mhs + Cleaned up the bibliography, added BT.653 and +BT.1119. capture.c/start_capturing() for user pointer I/O did not +initialize the buffer index. Documented the V4L MPEG and MJPEG +VID_TYPEs and V4L2_PIX_FMT_SBGGR8. Updated the list of reserved pixel +formats. See the history chapter for API changes. + + + + 0.14 + 2006-09-14 + mr + Added VIDIOC_ENUM_FRAMESIZES and +VIDIOC_ENUM_FRAMEINTERVALS proposal for frame format enumeration of +digital devices. + + + + 0.13 + 2006-04-07 + mhs + Corrected the description of struct v4l2_window +clips. New V4L2_STD_ and V4L2_TUNER_MODE_LANG1_LANG2 +defines. + + + + 0.12 + 2006-02-03 + mhs + Corrected the description of struct +v4l2_captureparm and v4l2_outputparm. + + + + 0.11 + 2006-01-27 + mhs + Improved the description of struct +v4l2_tuner. + + + + 0.10 + 2006-01-10 + mhs + VIDIOC_G_INPUT and VIDIOC_S_PARM +clarifications. + + + + 0.9 + 2005-11-27 + mhs + Improved the 525 line numbering diagram. Hans +Verkuil and I rewrote the sliced VBI section. He also contributed a +VIDIOC_LOG_STATUS page. Fixed VIDIOC_S_STD call in the video standard +selection example. Various updates. + + + + 0.8 + 2004-10-04 + mhs + Somehow a piece of junk slipped into the capture +example, removed. + + + + 0.7 + 2004-09-19 + mhs + Fixed video standard selection, control +enumeration, downscaling and aspect example. Added read and user +pointer i/o to video capture example. + + + + 0.6 + 2004-08-01 + mhs + v4l2_buffer changes, added video capture example, +various corrections. + + + + 0.5 + 2003-11-05 + mhs + Pixel format erratum. + + + + 0.4 + 2003-09-17 + mhs + Corrected source and Makefile to generate a PDF. +SGML fixes. Added latest API changes. Closed gaps in the history +chapter. + + + + 0.3 + 2003-02-05 + mhs + Another draft, more corrections. + + + + 0.2 + 2003-01-15 + mhs + Second draft, with corrections pointed out by Gerd +Knorr. + + + + 0.1 + 2002-12-01 + mhs + First draft, based on documentation by Bill Dirks +and discussions on the V4L mailing list. + + + + + + + + + Introduction + + Video For Linux Two is the second version of the Video For +Linux API, a kernel interface for analog radio and video capture and +output drivers. + + Early drivers used ad-hoc interfaces. These were replaced in +Linux 2.2 by Alan Cox' V4L API, based on the interface of the bttv +driver. In 1999 Bill Dirks started the development of V4L2 to fix some +shortcomings of V4L and to support a wider range of devices. The API +was revised again in 2002 prior to its inclusion in Linux 2.5/2.6, and +work continues on improvements and additions while maintaining +compatibility with existing drivers and applications. In 2006/2007 +efforts began on FreeBSD drivers with a V4L2 interface. + + This book documents the V4L2 API. Intended audience are +driver and application writers. + + If you have questions or ideas regarding the API, please +write to the Video4Linux mailing list: &v4l-ml;. For inquiries about +the V4L2 specification contact the maintainer mschimek@gmx.at. + + The latest version of this document and the DocBook SGML +sources are hosted at http://v4l2spec.bytesex.org, +and http://linuxtv.org/downloads/video4linux/API/V4L2_API. + + + + &sub-common; + + + + &sub-pixfmt; + + + + &sub-io; + + + + Interfaces + +
&sub-dev-capture;
+
&sub-dev-overlay;
+
&sub-dev-output;
+
&sub-dev-osd;
+
&sub-dev-codec;
+
&sub-dev-effect;
+
&sub-dev-raw-vbi;
+
&sub-dev-sliced-vbi;
+
&sub-dev-teletext;
+
&sub-dev-radio;
+
&sub-dev-rds;
+ + + + Function Reference + + + + &sub-close; + &sub-ioctl; + + &sub-cropcap; + &sub-dbg-g-register; + &sub-encoder-cmd; + &sub-enumaudio; + &sub-enumaudioout; + &sub-enum-fmt; + &sub-enum-framesizes; + &sub-enum-frameintervals; + &sub-enuminput; + &sub-enumoutput; + &sub-enumstd; + &sub-g-audio; + &sub-g-audioout; + &sub-g-chip-ident; + &sub-g-crop; + &sub-g-ctrl; + &sub-g-enc-index; + &sub-g-ext-ctrls; + &sub-g-fbuf; + &sub-g-fmt; + &sub-g-frequency; + &sub-g-input; + &sub-g-jpegcomp; + &sub-g-modulator; + &sub-g-output; + &sub-g-parm; + &sub-g-priority; + &sub-g-sliced-vbi-cap; + &sub-g-std; + &sub-g-tuner; + &sub-log-status; + &sub-overlay; + &sub-qbuf; + &sub-querybuf; + &sub-querycap; + &sub-queryctrl; + &sub-querystd; + &sub-reqbufs; + &sub-streamon; + + &sub-mmap; + &sub-munmap; + &sub-open; + &sub-poll; + &sub-read; + &sub-select; + &sub-write; + + + + &sub-driver; + + + + &sub-compat; + + + + Video For Linux Two Header File + &sub-videodev2-h; + + + + Video Capture Example + &sub-capture-c; + + + &sub-fdl-appendix; + + &sub-indices; + + &sub-biblio; + + diff --git a/v4l2-spec/vbi_525.gif b/v4l2-spec/vbi_525.gif new file mode 100644 index 000000000..5580b690d Binary files /dev/null and b/v4l2-spec/vbi_525.gif differ diff --git a/v4l2-spec/vbi_525.pdf b/v4l2-spec/vbi_525.pdf new file mode 100644 index 000000000..9e72c25b2 Binary files /dev/null and b/v4l2-spec/vbi_525.pdf differ diff --git a/v4l2-spec/vbi_625.gif b/v4l2-spec/vbi_625.gif new file mode 100644 index 000000000..34e325198 Binary files /dev/null and b/v4l2-spec/vbi_625.gif differ diff --git a/v4l2-spec/vbi_625.pdf b/v4l2-spec/vbi_625.pdf new file mode 100644 index 000000000..765235e33 Binary files /dev/null and b/v4l2-spec/vbi_625.pdf differ diff --git a/v4l2-spec/vbi_hsync.gif b/v4l2-spec/vbi_hsync.gif new file mode 100644 index 000000000..b02434d3b Binary files /dev/null and b/v4l2-spec/vbi_hsync.gif differ diff --git a/v4l2-spec/vbi_hsync.pdf b/v4l2-spec/vbi_hsync.pdf new file mode 100644 index 000000000..200b66818 Binary files /dev/null and b/v4l2-spec/vbi_hsync.pdf differ diff --git a/v4l2-spec/vidioc-dbg-g-register.sgml b/v4l2-spec/vidioc-dbg-g-register.sgml new file mode 100644 index 000000000..03f3150d9 --- /dev/null +++ b/v4l2-spec/vidioc-dbg-g-register.sgml @@ -0,0 +1,238 @@ + + + ioctl VIDIOC_DBG_G_REGISTER, VIDIOC_DBG_S_REGISTER + &manvol; + + + + VIDIOC_DBG_G_REGISTER + VIDIOC_DBG_S_REGISTER + Read or write hardware registers + + + + + + int ioctl + int fd + int request + struct v4l2_register *argp + + + + + int ioctl + int fd + int request + const struct v4l2_register +*argp + + + + + + Arguments + + + + fd + + &fd; + + + + request + + VIDIOC_DBG_G_REGISTER, VIDIOC_DBG_S_REGISTER + + + + argp + + + + + + + + + Description + + + Experimental + + This is an experimental +interface and may change in the future. + + + For driver debugging purposes these ioctls allow test +applications to access hardware registers directly. Regular +applications should not use them. + + Since writing or even reading registers can jeopardize the +system security, its stability and damage the hardware, both ioctls +require superuser privileges. Additionally the Linux kernel must be +compiled with the CONFIG_VIDEO_ADV_DEBUG option +to enable these ioctls. + + To write a register applications must initialize all fields +of a &v4l2-register; and call +VIDIOC_DBG_S_REGISTER with a pointer to this +structure. The match_type and +match_chip fields select a chip on the TV +card, the reg field specifies a register +number and the val field the value to be +written into the register. + + To read a register applications must initialize the +match_type, +match_chip and +reg fields, and call +VIDIOC_DBG_G_REGISTER with a pointer to this +structure. On success the driver stores the register value in the +val field. On failure the structure remains +unchanged. + + When match_type is +V4L2_CHIP_MATCH_HOST, +match_chip selects the nth non-&i2c; chip +on the TV card. Drivers may also interpret +match_chip as a random ID, but we recommend +against that. The number zero always selects the host chip, ⪚ the +chip connected to the PCI bus. You can find out which chips are +present with the &VIDIOC-G-CHIP-IDENT; ioctl. + + When match_type is +V4L2_CHIP_MATCH_I2C_DRIVER, +match_chip contains a driver ID as defined +in the linux/i2c-id.h header file. For instance +I2C_DRIVERID_SAA7127 will match any chip +supported by the saa7127 driver, regardless of its &i2c; bus address. +When multiple chips supported by the same driver are present, the +effect of these ioctls is undefined. Again with the +&VIDIOC-G-CHIP-IDENT; ioctl you can find out which &i2c; chips are +present. + + When match_type is +V4L2_CHIP_MATCH_I2C_ADDR, +match_chip selects a chip by its 7 bit &i2c; +bus address. + + + Success not guaranteed + + Due to a flaw in the Linux &i2c; bus driver these ioctls may +return successfully without actually reading or writing a register. To +catch the most likely failure we recommend a &VIDIOC-G-CHIP-IDENT; +call confirming the presence of the selected &i2c; chip. + + + These ioctls are optional, not all drivers may support them. +However when a driver supports these ioctls it must also support +&VIDIOC-G-CHIP-IDENT;. Conversely it may support +VIDIOC_G_CHIP_IDENT but not these ioctls. + + VIDIOC_DBG_G_REGISTER and +VIDIOC_DBG_S_REGISTER were introduced in Linux +2.6.21. + + We recommended the v4l2-dbg +utility over calling these ioctls directly. It is available from the +LinuxTV v4l-dvb repository; see http://linuxtv.org/repo/ for +access instructions. + + + struct <structname>v4l2_register</structname> + + + + + + + __u32 + match_type + See for a list of + possible types. + + + __u32 + match_chip + Match a chip by this number, interpreted according +to the match_type field. + + + __u64 + reg + A register number. + + + __u64 + val + The value read from, or to be written into the +register. + + + +
+ + + + Chip Match Types + + &cs-def; + + + V4L2_CHIP_MATCH_HOST + 0 + Match the nth chip on the card, zero for the + host chip. Does not match &i2c; chips. + + + V4L2_CHIP_MATCH_I2C_DRIVER + 1 + Match an &i2c; chip by its driver ID from the +linux/i2c-id.h header file. + + + V4L2_CHIP_MATCH_I2C_ADDR + 2 + Match a chip by its 7 bit &i2c; bus address. + + + +
+ + + + &return-value; + + + + EINVAL + + The driver does not support this ioctl, or the kernel +was not compiled with the CONFIG_VIDEO_ADV_DEBUG +option, or the match_type is invalid, or the +selected chip or register does not exist. + + + + EPERM + + Insufficient permissions. Root privileges are required +to execute these ioctls. + + + + + + + diff --git a/v4l2-spec/vidioc-encoder-cmd.sgml b/v4l2-spec/vidioc-encoder-cmd.sgml new file mode 100644 index 000000000..144b61c66 --- /dev/null +++ b/v4l2-spec/vidioc-encoder-cmd.sgml @@ -0,0 +1,204 @@ + + + ioctl VIDIOC_ENCODER_CMD, VIDIOC_TRY_ENCODER_CMD + &manvol; + + + + VIDIOC_ENCODER_CMD + VIDIOC_TRY_ENCODER_CMD + Execute an encoder command + + + + + + int ioctl + int fd + int request + struct v4l2_encoder_cmd *argp + + + + + + Arguments + + + + fd + + &fd; + + + + request + + VIDIOC_ENCODER_CMD, VIDIOC_TRY_ENCODER_CMD + + + + argp + + + + + + + + + Description + + + Experimental + + This is an experimental +interface and may change in the future. + + + These ioctls control an audio/video (usually MPEG-) encoder. +VIDIOC_ENCODER_CMD sends a command to the +encoder, VIDIOC_TRY_ENCODER_CMD can be used to +try a command without actually executing it. + + To send a command applications must initialize all fields of a + &v4l2-encoder-cmd; and call + VIDIOC_ENCODER_CMD or + VIDIOC_TRY_ENCODER_CMD with a pointer to this + structure. + + The cmd field must contain the +command code. The flags field is currently +only used by the STOP command and contains one bit: If the +V4L2_ENC_CMD_STOP_AT_GOP_END flag is set, +encoding will continue until the end of the current Group +Of Pictures, otherwise it will stop immediately. + + A read() call sends a START command to +the encoder if it has not been started yet. After a STOP command, +read() calls will read the remaining data +buffered by the driver. When the buffer is empty, +read() will return zero and the next +read() call will restart the encoder. + + A close() call sends an immediate STOP +to the encoder, and all buffered data is discarded. + + These ioctls are optional, not all drivers may support +them. They were introduced in Linux 2.6.21. + + + struct <structname>v4l2_encoder_cmd</structname> + + &cs-str; + + + __u32 + cmd + The encoder command, see . + + + __u32 + flags + Flags to go with the command, see . If no flags are defined for +this command, drivers and applications must set this field to +zero. + + + __u32 + data[8] + Reserved for future extensions. Drivers and +applications must set the array to zero. + + + +
+ + + Encoder Commands + + &cs-def; + + + V4L2_ENC_CMD_START + 0 + Start the encoder. When the encoder is already +running or paused, this command does nothing. No flags are defined for +this command. + + + V4L2_ENC_CMD_STOP + 1 + Stop the encoder. When the +V4L2_ENC_CMD_STOP_AT_GOP_END flag is set, +encoding will continue until the end of the current Group +Of Pictures, otherwise encoding will stop immediately. +When the encoder is already stopped, this command does +nothing. + + + V4L2_ENC_CMD_PAUSE + 2 + Pause the encoder. When the encoder has not been +started yet, the driver will return an &EPERM;. When the encoder is +already paused, this command does nothing. No flags are defined for +this command. + + + V4L2_ENC_CMD_RESUME + 3 + Resume encoding after a PAUSE command. When the +encoder has not been started yet, the driver will return an &EPERM;. +When the encoder is already running, this command does nothing. No +flags are defined for this command. + + + +
+ + + Encoder Command Flags + + &cs-def; + + + V4L2_ENC_CMD_STOP_AT_GOP_END + 0x0001 + Stop encoding at the end of the current Group Of +Pictures, rather than immediately. + + + +
+ + + + &return-value; + + + + EINVAL + + The driver does not support this ioctl, or the +cmd field is invalid. + + + + EPERM + + The application sent a PAUSE or RESUME command when +the encoder was not running. + + + + + + + diff --git a/v4l2-spec/vidioc-enum-fmt.sgml b/v4l2-spec/vidioc-enum-fmt.sgml new file mode 100644 index 000000000..5e0c7c770 --- /dev/null +++ b/v4l2-spec/vidioc-enum-fmt.sgml @@ -0,0 +1,157 @@ + + + ioctl VIDIOC_ENUM_FMT + &manvol; + + + + VIDIOC_ENUM_FMT + Enumerate image formats + + + + + + int ioctl + int fd + int request + struct v4l2_fmtdesc +*argp + + + + + + Arguments + + + + fd + + &fd; + + + + request + + VIDIOC_ENUM_FMT + + + + argp + + + + + + + + + Description + + To enumerate image formats applications initialize the +type and index +field of &v4l2-fmtdesc; and call the +VIDIOC_ENUM_FMT ioctl with a pointer to this +structure. Drivers fill the rest of the structure or return an +&EINVAL;. All formats are enumerable by beginning at index zero and +incrementing by one until EINVAL is +returned. + + + struct <structname>v4l2_fmtdesc</structname> + + &cs-str; + + + __u32 + index + Number of the format in the enumeration, set by +the application. This is in no way related to the +pixelformat field. + + + &v4l2-buf-type; + type + Type of the data stream, set by the application. +Only these types are valid here: +V4L2_BUF_TYPE_VIDEO_CAPTURE, +V4L2_BUF_TYPE_VIDEO_OUTPUT, +V4L2_BUF_TYPE_VIDEO_OVERLAY, and custom (driver +defined) types with code V4L2_BUF_TYPE_PRIVATE +and higher. + + + __u32 + flags + See + + + __u8 + description[32] + Description of the format, a NUL-terminated ASCII +string. This information is intended for the user, for example: "YUV +4:2:2". + + + __u32 + pixelformat + The image format identifier. This is a +four character code as computed by the v4l2_fourcc() +macro: + + + +#define v4l2_fourcc(a,b,c,d) (((__u32)(a)<<0)|((__u32)(b)<<8)|((__u32)(c)<<16)|((__u32)(d)<<24)) +Several image formats are already +defined by this specification in . Note these +codes are not the same as those used in the Windows world. + + + __u32 + reserved[4] + Reserved for future extensions. Drivers must set +the array to zero. + + + +
+ + + Image Format Description Flags + + &cs-def; + + + V4L2_FMT_FLAG_COMPRESSED + 0x0001 + This is a compressed format. + + + +
+ + + + &return-value; + + + + EINVAL + + The &v4l2-fmtdesc; type +is not supported or the index is out of +bounds. + + + + + + + diff --git a/v4l2-spec/vidioc-enum-frameintervals.sgml b/v4l2-spec/vidioc-enum-frameintervals.sgml new file mode 100644 index 000000000..fa0ac3616 --- /dev/null +++ b/v4l2-spec/vidioc-enum-frameintervals.sgml @@ -0,0 +1,270 @@ + + + + ioctl VIDIOC_ENUM_FRAMEINTERVALS + &manvol; + + + + VIDIOC_ENUM_FRAMEINTERVALS + Enumerate frame intervals + + + + + + int ioctl + int fd + int request + struct v4l2_frmivalenum *argp + + + + + + Arguments + + + + fd + + &fd; + + + + request + + VIDIOC_ENUM_FRAMEINTERVALS + + + + argp + + Pointer to a &v4l2-frmivalenum; structure that +contains a pixel format and size and receives a frame interval. + + + + + + + Description + + This ioctl allows applications to enumerate all frame +intervals that the device supports for the given pixel format and +frame size. + The supported pixel formats and frame sizes can be obtained +by using the &VIDIOC-ENUM-FMT; and &VIDIOC-ENUM-FRAMESIZES; +functions. + The return value and the content of the +v4l2_frmivalenum.type field depend on the +type of frame intervals the device supports. Here are the semantics of +the function for the different cases: + + + Discrete: The function +returns success if the given index value (zero-based) is valid. The +application should increase the index by one for each call until +EINVAL is returned. The `v4l2_frmivalenum.type` +field is set to `V4L2_FRMIVAL_TYPE_DISCRETE` by the driver. Of the +union only the `discrete` member is valid. + + + Step-wise: The function +returns success if the given index value is zero and +EINVAL for any other index value. The +v4l2_frmivalenum.type field is set to +V4L2_FRMIVAL_TYPE_STEPWISE by the driver. Of the +union only the stepwise member is +valid. + + + Continuous: This is a +special case of the step-wise type above. The function returns success +if the given index value is zero and EINVAL for +any other index value. The +v4l2_frmivalenum.type field is set to +V4L2_FRMIVAL_TYPE_CONTINUOUS by the driver. Of +the union only the stepwise member is valid +and the step value is set to 1. + + + + When the application calls the function with index zero, it +must check the type field to determine the +type of frame interval enumeration the device supports. Only for the +V4L2_FRMIVAL_TYPE_DISCRETE type does it make +sense to increase the index value to receive more frame +intervals. + Note that the order in which the frame intervals are +returned has no special meaning. In particular does it not say +anything about potential default frame intervals. + Applications can assume that the enumeration data does not +change without any interaction from the application itself. This means +that the enumeration data is consistent if the application does not +perform any other ioctl calls while it runs the frame interval +enumeration. + + + + Notes + + + + Frame intervals and frame +rates: The V4L2 API uses frame intervals instead of frame +rates. Given the frame interval the frame rate can be computed as +follows:frame_rate = 1 / frame_interval + + + + + + + Structs + + In the structs below, IN denotes a +value that has to be filled in by the application, +OUT denotes values that the driver fills in. The +application should zero out all members except for the +IN fields. + + + struct <structname>v4l2_frmival_stepwise</structname> + + &cs-str; + + + &v4l2-fract; + min + Minimum frame interval [s]. + + + &v4l2-fract; + max + Maximum frame interval [s]. + + + &v4l2-fract; + step + Frame interval step size [s]. + + + +
+ + + struct <structname>v4l2_frmivalenum</structname> + + + + + + + + __u32 + index + + IN: Index of the given frame interval in the +enumeration. + + + __u32 + pixel_format + + IN: Pixel format for which the frame intervals are +enumerated. + + + __u32 + width + + IN: Frame width for which the frame intervals are +enumerated. + + + __u32 + height + + IN: Frame height for which the frame intervals are +enumerated. + + + __u32 + type + + OUT: Frame interval type the device supports. + + + union + + + OUT: Frame interval with the given index. + + + + &v4l2-fract; + discrete + Frame interval [s]. + + + + &v4l2-frmival-stepwise; + stepwise + + + + __u32 + reserved[2] + + Reserved space for future use. + + + +
+ + + + Enums + + + enum <structname>v4l2_frmivaltypes</structname> + + &cs-def; + + + V4L2_FRMIVAL_TYPE_DISCRETE + 1 + Discrete frame interval. + + + V4L2_FRMIVAL_TYPE_CONTINUOUS + 2 + Continuous frame interval. + + + V4L2_FRMIVAL_TYPE_STEPWISE + 3 + Step-wise defined frame interval. + + + +
+ + + + &return-value; + + See the description section above for a list of return +values that errno can have. + + + + + diff --git a/v4l2-spec/vidioc-enum-framesizes.sgml b/v4l2-spec/vidioc-enum-framesizes.sgml new file mode 100644 index 000000000..909cda68b --- /dev/null +++ b/v4l2-spec/vidioc-enum-framesizes.sgml @@ -0,0 +1,282 @@ + + + + ioctl VIDIOC_ENUM_FRAMESIZES + &manvol; + + + + VIDIOC_ENUM_FRAMESIZES + Enumerate frame sizes + + + + + + int ioctl + int fd + int request + struct v4l2_frmsizeenum *argp + + + + + + Arguments + + + + fd + + &fd; + + + + request + + VIDIOC_ENUM_FRAMESIZES + + + + argp + + Pointer to a &v4l2-frmsizeenum; that contains an index +and pixel format and receives a frame width and height. + + + + + + + Description + + + Experimental + + This is an experimental +interface and may change in the future. + + + This ioctl allows applications to enumerate all frame sizes +(&ie; width and height in pixels) that the device supports for the +given pixel format. + The supported pixel formats can be obtained by using the +&VIDIOC-ENUM-FMT; function. + The return value and the content of the +v4l2_frmsizeenum.type field depend on the +type of frame sizes the device supports. Here are the semantics of the +function for the different cases: + + + + Discrete: The function +returns success if the given index value (zero-based) is valid. The +application should increase the index by one for each call until +EINVAL is returned. The +v4l2_frmsizeenum.type field is set to +V4L2_FRMSIZE_TYPE_DISCRETE by the driver. Of the +union only the discrete member is +valid. + + + Step-wise: The function +returns success if the given index value is zero and +EINVAL for any other index value. The +v4l2_frmsizeenum.type field is set to +V4L2_FRMSIZE_TYPE_STEPWISE by the driver. Of the +union only the stepwise member is +valid. + + + Continuous: This is a +special case of the step-wise type above. The function returns success +if the given index value is zero and EINVAL for +any other index value. The +v4l2_frmsizeenum.type field is set to +V4L2_FRMSIZE_TYPE_CONTINUOUS by the driver. Of +the union only the stepwise member is valid +and the step_width and +step_height values are set to 1. + + + + When the application calls the function with index zero, it +must check the type field to determine the +type of frame size enumeration the device supports. Only for the +V4L2_FRMSIZE_TYPE_DISCRETE type does it make +sense to increase the index value to receive more frame sizes. + Note that the order in which the frame sizes are returned +has no special meaning. In particular does it not say anything about +potential default format sizes. + Applications can assume that the enumeration data does not +change without any interaction from the application itself. This means +that the enumeration data is consistent if the application does not +perform any other ioctl calls while it runs the frame size +enumeration. + + + + Structs + + In the structs below, IN denotes a +value that has to be filled in by the application, +OUT denotes values that the driver fills in. The +application should zero out all members except for the +IN fields. + + + struct <structname>v4l2_frmsize_discrete</structname> + + &cs-str; + + + __u32 + width + Width of the frame [pixel]. + + + __u32 + height + Height of the frame [pixel]. + + + +
+ + + struct <structname>v4l2_frmsize_stepwise</structname> + + &cs-str; + + + __u32 + min_width + Minimum frame width [pixel]. + + + __u32 + max_width + Maximum frame width [pixel]. + + + __u32 + step_width + Frame width step size [pixel]. + + + __u32 + min_height + Minimum frame height [pixel]. + + + __u32 + max_height + Maximum frame height [pixel]. + + + __u32 + step_height + Frame height step size [pixel]. + + + +
+ + + struct <structname>v4l2_frmsizeenum</structname> + + + + + + + + __u32 + index + + IN: Index of the given frame size in the enumeration. + + + __u32 + pixel_format + + IN: Pixel format for which the frame sizes are enumerated. + + + __u32 + type + + OUT: Frame size type the device supports. + + + union + + + OUT: Frame size with the given index. + + + + &v4l2-frmsize-discrete; + discrete + + + + + &v4l2-frmsize-stepwise; + stepwise + + + + __u32 + reserved[2] + + Reserved space for future use. + + + +
+ + + + Enums + + + enum <structname>v4l2_frmsizetypes</structname> + + &cs-def; + + + V4L2_FRMSIZE_TYPE_DISCRETE + 1 + Discrete frame size. + + + V4L2_FRMSIZE_TYPE_CONTINUOUS + 2 + Continuous frame size. + + + V4L2_FRMSIZE_TYPE_STEPWISE + 3 + Step-wise defined frame size. + + + +
+ + + + &return-value; + + See the description section above for a list of return +values that errno can have. + + + + diff --git a/v4l2-spec/vidioc-enumaudio.sgml b/v4l2-spec/vidioc-enumaudio.sgml new file mode 100644 index 000000000..2cd9e020d --- /dev/null +++ b/v4l2-spec/vidioc-enumaudio.sgml @@ -0,0 +1,86 @@ + + + ioctl VIDIOC_ENUMAUDIO + &manvol; + + + + VIDIOC_ENUMAUDIO + Enumerate audio inputs + + + + + + int ioctl + int fd + int request + struct v4l2_audio *argp + + + + + + Arguments + + + + fd + + &fd; + + + + request + + VIDIOC_ENUMAUDIO + + + + argp + + + + + + + + + Description + + To query the attributes of an audio input applications +initialize the index field and zero out the +reserved array of a &v4l2-audio; +and call the VIDIOC_ENUMAUDIO ioctl with a pointer +to this structure. Drivers fill the rest of the structure or return an +&EINVAL; when the index is out of bounds. To enumerate all audio +inputs applications shall begin at index zero, incrementing by one +until the driver returns EINVAL. + + See for a description of +&v4l2-audio;. + + + + &return-value; + + + + EINVAL + + The number of the audio input is out of bounds, or +there are no audio inputs at all and this ioctl is not +supported. + + + + + + + diff --git a/v4l2-spec/vidioc-enumaudioout.sgml b/v4l2-spec/vidioc-enumaudioout.sgml new file mode 100644 index 000000000..5c51e3bfe --- /dev/null +++ b/v4l2-spec/vidioc-enumaudioout.sgml @@ -0,0 +1,89 @@ + + + ioctl VIDIOC_ENUMAUDOUT + &manvol; + + + + VIDIOC_ENUMAUDOUT + Enumerate audio outputs + + + + + + int ioctl + int fd + int request + struct v4l2_audioout *argp + + + + + + Arguments + + + + fd + + &fd; + + + + request + + VIDIOC_ENUMAUDOUT + + + + argp + + + + + + + + + Description + + To query the attributes of an audio output applications +initialize the index field and zero out the +reserved array of a &v4l2-audioout; and +call the VIDIOC_G_AUDOUT ioctl with a pointer +to this structure. Drivers fill the rest of the structure or return an +&EINVAL; when the index is out of bounds. To enumerate all audio +outputs applications shall begin at index zero, incrementing by one +until the driver returns EINVAL. + + Note connectors on a TV card to loop back the received audio +signal to a sound card are not audio outputs in this sense. + + See for a description of +&v4l2-audioout;. + + + + &return-value; + + + + EINVAL + + The number of the audio output is out of bounds, or +there are no audio outputs at all and this ioctl is not +supported. + + + + + + + diff --git a/v4l2-spec/vidioc-enuminput.sgml b/v4l2-spec/vidioc-enuminput.sgml new file mode 100644 index 000000000..1c1486b43 --- /dev/null +++ b/v4l2-spec/vidioc-enuminput.sgml @@ -0,0 +1,270 @@ + + + ioctl VIDIOC_ENUMINPUT + &manvol; + + + + VIDIOC_ENUMINPUT + Enumerate video inputs + + + + + + int ioctl + int fd + int request + struct v4l2_input +*argp + + + + + + Arguments + + + + fd + + &fd; + + + + request + + VIDIOC_ENUMINPUT + + + + argp + + + + + + + + + Description + + To query the attributes of a video input applications +initialize the index field of &v4l2-input; +and call the VIDIOC_ENUMINPUT ioctl with a +pointer to this structure. Drivers fill the rest of the structure or +return an &EINVAL; when the index is out of bounds. To enumerate all +inputs applications shall begin at index zero, incrementing by one +until the driver returns EINVAL. + + + struct <structname>v4l2_input</structname> + + &cs-str; + + + __u32 + index + Identifies the input, set by the +application. + + + __u8 + name[32] + Name of the video input, a NUL-terminated ASCII +string, for example: "Vin (Composite 2)". This information is intended +for the user, preferably the connector label on the device itself. + + + __u32 + type + Type of the input, see . + + + __u32 + audioset + Drivers can enumerate up to 32 video and +audio inputs. This field shows which audio inputs were selectable as +audio source if this was the currently selected video input. It is a +bit mask. The LSB corresponds to audio input 0, the MSB to input 31. +Any number of bits can be set, or none.When the driver +does not enumerate audio inputs no bits must be set. Applications +shall not interpret this as lack of audio support. Some drivers +automatically select audio sources and do not enumerate them since +there is no choice anyway.For details on audio inputs and +how to select the current input see . + + + __u32 + tuner + Capture devices can have zero or more tuners (RF +demodulators). When the type is set to +V4L2_INPUT_TYPE_TUNER this is an RF connector and +this field identifies the tuner. It corresponds to +&v4l2-tuner; field index. For details on +tuners see . + + + &v4l2-std-id; + std + Every video input supports one or more different +video standards. This field is a set of all supported standards. For +details on video standards and how to switch see . + + + __u32 + status + This field provides status information about the +input. See for flags. +status is only valid when this is the +current input. + + + __u32 + reserved[4] + Reserved for future extensions. Drivers must set +the array to zero. + + + +
+ + + Input Types + + &cs-def; + + + V4L2_INPUT_TYPE_TUNER + 1 + This input uses a tuner (RF demodulator). + + + V4L2_INPUT_TYPE_CAMERA + 2 + Analog baseband input, for example CVBS / +Composite Video, S-Video, RGB. + + + +
+ + + + + Input Status Flags + + + + + + + + General + + + V4L2_IN_ST_NO_POWER + 0x00000001 + Attached device is off. + + + V4L2_IN_ST_NO_SIGNAL + 0x00000002 + + + + V4L2_IN_ST_NO_COLOR + 0x00000004 + The hardware supports color decoding, but does not +detect color modulation in the signal. + + + Analog Video + + + V4L2_IN_ST_NO_H_LOCK + 0x00000100 + No horizontal sync lock. + + + V4L2_IN_ST_COLOR_KILL + 0x00000200 + A color killer circuit automatically disables color +decoding when it detects no color modulation. When this flag is set +the color killer is enabled and has shut off +color decoding. + + + Digital Video + + + V4L2_IN_ST_NO_SYNC + 0x00010000 + No synchronization lock. + + + V4L2_IN_ST_NO_EQU + 0x00020000 + No equalizer lock. + + + V4L2_IN_ST_NO_CARRIER + 0x00040000 + Carrier recovery failed. + + + VCR and Set-Top Box + + + V4L2_IN_ST_MACROVISION + 0x01000000 + Macrovision is an analog copy prevention system +mangling the video signal to confuse video recorders. When this +flag is set Macrovision has been detected. + + + V4L2_IN_ST_NO_ACCESS + 0x02000000 + Conditional access denied. + + + V4L2_IN_ST_VTR + 0x04000000 + VTR time constant. [?] + + + +
+ + + + &return-value; + + + + EINVAL + + The &v4l2-input; index is +out of bounds. + + + + + + + diff --git a/v4l2-spec/vidioc-enumoutput.sgml b/v4l2-spec/vidioc-enumoutput.sgml new file mode 100644 index 000000000..7e3481203 --- /dev/null +++ b/v4l2-spec/vidioc-enumoutput.sgml @@ -0,0 +1,172 @@ + + + ioctl VIDIOC_ENUMOUTPUT + &manvol; + + + + VIDIOC_ENUMOUTPUT + Enumerate video outputs + + + + + + int ioctl + int fd + int request + struct v4l2_output *argp + + + + + + Arguments + + + + fd + + &fd; + + + + request + + VIDIOC_ENUMOUTPUT + + + + argp + + + + + + + + + Description + + To query the attributes of a video outputs applications +initialize the index field of &v4l2-output; +and call the VIDIOC_ENUMOUTPUT ioctl with a +pointer to this structure. Drivers fill the rest of the structure or +return an &EINVAL; when the index is out of bounds. To enumerate all +outputs applications shall begin at index zero, incrementing by one +until the driver returns EINVAL. + + + struct <structname>v4l2_output</structname> + + &cs-str; + + + __u32 + index + Identifies the output, set by the +application. + + + __u8 + name[32] + Name of the video output, a NUL-terminated ASCII +string, for example: "Vout". This information is intended for the +user, preferably the connector label on the device itself. + + + __u32 + type + Type of the output, see . + + + __u32 + audioset + Drivers can enumerate up to 32 video and +audio outputs. This field shows which audio outputs were +selectable as the current output if this was the currently selected +video output. It is a bit mask. The LSB corresponds to audio output 0, +the MSB to output 31. Any number of bits can be set, or +none.When the driver does not enumerate audio outputs no +bits must be set. Applications shall not interpret this as lack of +audio support. Drivers may automatically select audio outputs without +enumerating them.For details on audio outputs and how to +select the current output see . + + + __u32 + modulator + Output devices can have zero or more RF modulators. +When the type is +V4L2_OUTPUT_TYPE_MODULATOR this is an RF +connector and this field identifies the modulator. It corresponds to +&v4l2-modulator; field index. For details +on modulators see . + + + &v4l2-std-id; + std + Every video output supports one or more different +video standards. This field is a set of all supported standards. For +details on video standards and how to switch see . + + + __u32 + reserved[4] + Reserved for future extensions. Drivers must set +the array to zero. + + + +
+ + + Output Type + + &cs-def; + + + V4L2_OUTPUT_TYPE_MODULATOR + 1 + This output is an analog TV modulator. + + + V4L2_OUTPUT_TYPE_ANALOG + 2 + Analog baseband output, for example Composite / +CVBS, S-Video, RGB. + + + V4L2_OUTPUT_TYPE_ANALOGVGAOVERLAY + 3 + [?] + + + +
+ + + + &return-value; + + + + EINVAL + + The &v4l2-output; index +is out of bounds. + + + + + + + diff --git a/v4l2-spec/vidioc-enumstd.sgml b/v4l2-spec/vidioc-enumstd.sgml new file mode 100644 index 000000000..c775671bd --- /dev/null +++ b/v4l2-spec/vidioc-enumstd.sgml @@ -0,0 +1,391 @@ + + + ioctl VIDIOC_ENUMSTD + &manvol; + + + + VIDIOC_ENUMSTD + Enumerate supported video standards + + + + + + int ioctl + int fd + int request + struct v4l2_standard *argp + + + + + + Arguments + + + + fd + + &fd; + + + + request + + VIDIOC_ENUMSTD + + + + argp + + + + + + + + + Description + + To query the attributes of a video standard, +especially a custom (driver defined) one, applications initialize the +index field of &v4l2-standard; and call the +VIDIOC_ENUMSTD ioctl with a pointer to this +structure. Drivers fill the rest of the structure or return an +&EINVAL; when the index is out of bounds. To enumerate all standards +applications shall begin at index zero, incrementing by one until the +driver returns EINVAL. Drivers may enumerate a +different set of standards after switching the video input or +output. + The supported standards may overlap and we need an +unambiguous set to find the current standard returned by +VIDIOC_G_STD. + + + + struct <structname>v4l2_standard</structname> + + &cs-str; + + + __u32 + index + Number of the video standard, set by the +application. + + + &v4l2-std-id; + id + The bits in this field identify the standard as +one of the common standards listed in , +or if bits 32 to 63 are set as custom standards. Multiple bits can be +set if the hardware does not distinguish between these standards, +however separate indices do not indicate the opposite. The +id must be unique. No other enumerated +v4l2_standard structure, for this input or +output anyway, can contain the same set of bits. + + + __u8 + name[24] + Name of the standard, a NUL-terminated ASCII +string, for example: "PAL-B/G", "NTSC Japan". This information is +intended for the user. + + + &v4l2-fract; + frameperiod + The frame period (not field period) is numerator +/ denominator. For example M/NTSC has a frame period of 1001 / +30000 seconds. + + + __u32 + framelines + Total lines per frame including blanking, +e. g. 625 for B/PAL. + + + __u32 + reserved[4] + Reserved for future extensions. Drivers must set +the array to zero. + + + +
+ + + struct <structname>v4l2_fract</structname> + + &cs-str; + + + __u32 + numerator + + + + __u32 + denominator + + + + +
+ + + typedef <structname>v4l2_std_id</structname> + + &cs-str; + + + __u64 + v4l2_std_id + This type is a set, each bit representing another +video standard as listed below and in . The 32 most significant bits are reserved +for custom (driver defined) video standards. + + + +
+ + +#define V4L2_STD_PAL_B ((v4l2_std_id)0x00000001) +#define V4L2_STD_PAL_B1 ((v4l2_std_id)0x00000002) +#define V4L2_STD_PAL_G ((v4l2_std_id)0x00000004) +#define V4L2_STD_PAL_H ((v4l2_std_id)0x00000008) +#define V4L2_STD_PAL_I ((v4l2_std_id)0x00000010) +#define V4L2_STD_PAL_D ((v4l2_std_id)0x00000020) +#define V4L2_STD_PAL_D1 ((v4l2_std_id)0x00000040) +#define V4L2_STD_PAL_K ((v4l2_std_id)0x00000080) + +#define V4L2_STD_PAL_M ((v4l2_std_id)0x00000100) +#define V4L2_STD_PAL_N ((v4l2_std_id)0x00000200) +#define V4L2_STD_PAL_Nc ((v4l2_std_id)0x00000400) +#define V4L2_STD_PAL_60 ((v4l2_std_id)0x00000800) +V4L2_STD_PAL_60 is +a hybrid standard with 525 lines, 60 Hz refresh rate, and PAL color +modulation with a 4.43 MHz color subcarrier. Some PAL video recorders +can play back NTSC tapes in this mode for display on a 50/60 Hz agnostic +PAL TV. +#define V4L2_STD_NTSC_M ((v4l2_std_id)0x00001000) +#define V4L2_STD_NTSC_M_JP ((v4l2_std_id)0x00002000) +#define V4L2_STD_NTSC_443 ((v4l2_std_id)0x00004000) +V4L2_STD_NTSC_443 +is a hybrid standard with 525 lines, 60 Hz refresh rate, and NTSC +color modulation with a 4.43 MHz color +subcarrier. +#define V4L2_STD_NTSC_M_KR ((v4l2_std_id)0x00008000) + +#define V4L2_STD_SECAM_B ((v4l2_std_id)0x00010000) +#define V4L2_STD_SECAM_D ((v4l2_std_id)0x00020000) +#define V4L2_STD_SECAM_G ((v4l2_std_id)0x00040000) +#define V4L2_STD_SECAM_H ((v4l2_std_id)0x00080000) +#define V4L2_STD_SECAM_K ((v4l2_std_id)0x00100000) +#define V4L2_STD_SECAM_K1 ((v4l2_std_id)0x00200000) +#define V4L2_STD_SECAM_L ((v4l2_std_id)0x00400000) +#define V4L2_STD_SECAM_LC ((v4l2_std_id)0x00800000) + +/* ATSC/HDTV */ +#define V4L2_STD_ATSC_8_VSB ((v4l2_std_id)0x01000000) +#define V4L2_STD_ATSC_16_VSB ((v4l2_std_id)0x02000000) +V4L2_STD_ATSC_8_VSB and +V4L2_STD_ATSC_16_VSB are U.S. terrestrial digital +TV standards. Presently the V4L2 API does not support digital TV. See +also the Linux DVB API at http://linuxtv.org. + +#define V4L2_STD_PAL_BG (V4L2_STD_PAL_B |\ + V4L2_STD_PAL_B1 |\ + V4L2_STD_PAL_G) +#define V4L2_STD_B (V4L2_STD_PAL_B |\ + V4L2_STD_PAL_B1 |\ + V4L2_STD_SECAM_B) +#define V4L2_STD_GH (V4L2_STD_PAL_G |\ + V4L2_STD_PAL_H |\ + V4L2_STD_SECAM_G |\ + V4L2_STD_SECAM_H) +#define V4L2_STD_PAL_DK (V4L2_STD_PAL_D |\ + V4L2_STD_PAL_D1 |\ + V4L2_STD_PAL_K) +#define V4L2_STD_PAL (V4L2_STD_PAL_BG |\ + V4L2_STD_PAL_DK |\ + V4L2_STD_PAL_H |\ + V4L2_STD_PAL_I) +#define V4L2_STD_NTSC (V4L2_STD_NTSC_M |\ + V4L2_STD_NTSC_M_JP |\ + V4L2_STD_NTSC_M_KR) +#define V4L2_STD_MN (V4L2_STD_PAL_M |\ + V4L2_STD_PAL_N |\ + V4L2_STD_PAL_Nc |\ + V4L2_STD_NTSC) +#define V4L2_STD_SECAM_DK (V4L2_STD_SECAM_D |\ + V4L2_STD_SECAM_K |\ + V4L2_STD_SECAM_K1) +#define V4L2_STD_DK (V4L2_STD_PAL_DK |\ + V4L2_STD_SECAM_DK) + +#define V4L2_STD_SECAM (V4L2_STD_SECAM_B |\ + V4L2_STD_SECAM_G |\ + V4L2_STD_SECAM_H |\ + V4L2_STD_SECAM_DK |\ + V4L2_STD_SECAM_L |\ + V4L2_STD_SECAM_LC) + +#define V4L2_STD_525_60 (V4L2_STD_PAL_M |\ + V4L2_STD_PAL_60 |\ + V4L2_STD_NTSC |\ + V4L2_STD_NTSC_443) +#define V4L2_STD_625_50 (V4L2_STD_PAL |\ + V4L2_STD_PAL_N |\ + V4L2_STD_PAL_Nc |\ + V4L2_STD_SECAM) + +#define V4L2_STD_UNKNOWN 0 +#define V4L2_STD_ALL (V4L2_STD_525_60 |\ + V4L2_STD_625_50) + + + + Video Standards (based on [<xref linkend="itu470">]) + + + + + + + + + + + + + + + + Characteristics + M/NTSCJapan uses a standard +similar to M/NTSC +(V4L2_STD_NTSC_M_JP). + M/PAL + N/PAL The values in +brackets apply to the combination N/PAL a.k.a. +NC used in Argentina +(V4L2_STD_PAL_Nc). + B, B1, G/PAL + D, D1, K/PAL + H/PAL + I/PAL + B, G/SECAM + D, K/SECAM + K1/SECAM + L/SECAM + + + + + Frame lines + 525 + 625 + + + Frame period (s) + 1001/30000 + 1/25 + + + Chrominance sub-carrier frequency (Hz) + 3579545 ± 10 + 3579611.49 ± 10 + 4433618.75 ± 5 (3582056.25 +± 5) + 4433618.75 ± 5 + 4433618.75 ± 1 + fOR = +4406250 ± 2000, fOB = 4250000 +± 2000 + + + Nominal radio-frequency channel bandwidth +(MHz) + 6 + 6 + 6 + B: 7; B1, G: 8 + 8 + 8 + 8 + 8 + 8 + 8 + 8 + + + Sound carrier relative to vision carrier +(MHz) + + 4.5 + + 4.5 + + 4.5 + + 5.5 ± 0.001 +In the Federal Republic of Germany, Austria, Italy, +the Netherlands, Slovakia and Switzerland a system of two sound +carriers is used, the frequency of the second carrier being +242.1875 kHz above the frequency of the first sound carrier. For +stereophonic sound transmissions a similar system is used in +Australia. New Zealand uses a sound +carrier displaced 5.4996 ± 0.0005 MHz from the vision +carrier. In Denmark, Finland, New +Zealand, Sweden and Spain a system of two sound carriers is used. In +Iceland, Norway and Poland the same system is being introduced. The +second carrier is 5.85 MHz above the vision carrier and is DQPSK +modulated with 728 kbit/s sound and data multiplex. (NICAM +system) In the United Kingdom, a +system of two sound carriers is used. The second sound carrier is +6.552 MHz above the vision carrier and is DQPSK modulated with a +728 kbit/s sound and data multiplex able to carry two sound +channels. (NICAM system) + + 6.5 ± 0.001 + + 5.5 + + 5.9996 ± 0.0005 + + 5.5 ± 0.001 + + 6.5 ± 0.001 + + 6.5 + + 6.5 In France, a +digital carrier 5.85 MHz away from the vision carrier may be used in +addition to the main sound carrier. It is modulated in differentially +encoded QPSK with a 728 kbit/s sound and data multiplexer capable of +carrying two sound channels. (NICAM +system) + + + +
+ + + + &return-value; + + + + EINVAL + + The &v4l2-standard; index +is out of bounds. + + + + + + + diff --git a/v4l2-spec/vidioc-g-audio.sgml b/v4l2-spec/vidioc-g-audio.sgml new file mode 100644 index 000000000..8b929158e --- /dev/null +++ b/v4l2-spec/vidioc-g-audio.sgml @@ -0,0 +1,188 @@ + + + ioctl VIDIOC_G_AUDIO, VIDIOC_S_AUDIO + &manvol; + + + + VIDIOC_G_AUDIO + VIDIOC_S_AUDIO + Query or select the current audio input and its +attributes + + + + + + int ioctl + int fd + int request + struct v4l2_audio *argp + + + + + int ioctl + int fd + int request + const struct v4l2_audio *argp + + + + + + Arguments + + + + fd + + &fd; + + + + request + + VIDIOC_G_AUDIO, VIDIOC_S_AUDIO + + + + argp + + + + + + + + + Description + + To query the current audio input applications zero out the +reserved array of a &v4l2-audio; +and call the VIDIOC_G_AUDIO ioctl with a pointer +to this structure. Drivers fill the rest of the structure or return an +&EINVAL; when the device has no audio inputs, or none which combine +with the current video input. + + Audio inputs have one writable property, the audio mode. To +select the current audio input and change the +audio mode, applications initialize the +index and mode +fields, and the +reserved array of a +v4l2_audio structure and call the +VIDIOC_S_AUDIO ioctl. Drivers may switch to a +different audio mode if the request cannot be satisfied. However, this +is a write-only ioctl, it does not return the actual new audio +mode. + + + struct <structname>v4l2_audio</structname> + + &cs-str; + + + __u32 + index + Identifies the audio input, set by the +driver or application. + + + __u8 + name[32] + Name of the audio input, a NUL-terminated ASCII +string, for example: "Line In". This information is intended for the +user, preferably the connector label on the device itself. + + + __u32 + capability + Audio capability flags, see . + + + __u32 + mode + Audio mode flags set by drivers and applications (on + VIDIOC_S_AUDIO ioctl), see . + + + __u32 + reserved[2] + Reserved for future extensions. Drivers and +applications must set the array to zero. + + + +
+ + + Audio Capability Flags + + &cs-def; + + + V4L2_AUDCAP_STEREO + 0x00001 + This is a stereo input. The flag is intended to +automatically disable stereo recording etc. when the signal is always +monaural. The API provides no means to detect if stereo is +received, unless the audio input belongs to a +tuner. + + + V4L2_AUDCAP_AVL + 0x00002 + Automatic Volume Level mode is supported. + + + +
+ + + Audio Mode Flags + + &cs-def; + + + V4L2_AUDMODE_AVL + 0x00001 + AVL mode is on. + + + +
+ + + + &return-value; + + + + EINVAL + + No audio inputs combine with the current video input, +or the number of the selected audio input is out of bounds or it does +not combine, or there are no audio inputs at all and the ioctl is not +supported. + + + + EBUSY + + I/O is in progress, the input cannot be +switched. + + + + + + + diff --git a/v4l2-spec/vidioc-g-audioout.sgml b/v4l2-spec/vidioc-g-audioout.sgml new file mode 100644 index 000000000..3632730c5 --- /dev/null +++ b/v4l2-spec/vidioc-g-audioout.sgml @@ -0,0 +1,154 @@ + + + ioctl VIDIOC_G_AUDOUT, VIDIOC_S_AUDOUT + &manvol; + + + + VIDIOC_G_AUDOUT + VIDIOC_S_AUDOUT + Query or select the current audio output + + + + + + int ioctl + int fd + int request + struct v4l2_audioout *argp + + + + + int ioctl + int fd + int request + const struct v4l2_audioout *argp + + + + + + Arguments + + + + fd + + &fd; + + + + request + + VIDIOC_G_AUDOUT, VIDIOC_S_AUDOUT + + + + argp + + + + + + + + + Description + + To query the current audio output applications zero out the +reserved array of a &v4l2-audioout; and +call the VIDIOC_G_AUDOUT ioctl with a pointer +to this structure. Drivers fill the rest of the structure or return an +&EINVAL; when the device has no audio inputs, or none which combine +with the current video output. + + Audio outputs have no writable properties. Nevertheless, to +select the current audio output applications can initialize the +index field and +reserved array (which in the future may +contain writable properties) of a +v4l2_audioout structure and call the +VIDIOC_S_AUDOUT ioctl. Drivers switch to the +requested output or return the &EINVAL; when the index is out of +bounds. This is a write-only ioctl, it does not return the current +audio output attributes as VIDIOC_G_AUDOUT +does. + + Note connectors on a TV card to loop back the received audio +signal to a sound card are not audio outputs in this sense. + + + struct <structname>v4l2_audioout</structname> + + &cs-str; + + + __u32 + index + Identifies the audio output, set by the +driver or application. + + + __u8 + name[32] + Name of the audio output, a NUL-terminated ASCII +string, for example: "Line Out". This information is intended for the +user, preferably the connector label on the device itself. + + + __u32 + capability + Audio capability flags, none defined yet. Drivers +must set this field to zero. + + + __u32 + mode + Audio mode, none defined yet. Drivers and +applications (on VIDIOC_S_AUDOUT) must set this +field to zero. + + + __u32 + reserved[2] + Reserved for future extensions. Drivers and +applications must set the array to zero. + + + +
+ + + + &return-value; + + + + EINVAL + + No audio outputs combine with the current video +output, or the number of the selected audio output is out of bounds or +it does not combine, or there are no audio outputs at all and the +ioctl is not supported. + + + + EBUSY + + I/O is in progress, the output cannot be +switched. + + + + + + + diff --git a/v4l2-spec/vidioc-g-chip-ident.sgml b/v4l2-spec/vidioc-g-chip-ident.sgml new file mode 100644 index 000000000..4f3cc59a7 --- /dev/null +++ b/v4l2-spec/vidioc-g-chip-ident.sgml @@ -0,0 +1,236 @@ + + + ioctl VIDIOC_G_CHIP_IDENT + &manvol; + + + + VIDIOC_G_CHIP_IDENT + Identify the chips on a TV card + + + + + + int ioctl + int fd + int request + struct v4l2_chip_ident +*argp + + + + + + Arguments + + + + fd + + &fd; + + + + request + + VIDIOC_G_CHIP_IDENT + + + + argp + + + + + + + + + Description + + + Experimental + + This is an experimental interface and may change in +the future. + + + For driver debugging purposes this ioctl allows test +applications to query the driver about the chips present on the TV +card. Regular applications should not use it. When you found a chip +specific bug, please contact the Video4Linux mailing list (&v4l-ml;) +so it can be fixed. + + To query the driver applications must initialize the +match_type and +match_chip fields of a &v4l2-chip-ident; +and call VIDIOC_G_CHIP_IDENT with a pointer to +this structure. On success the driver stores information about the +selected chip in the ident and +revision fields. On failure the structure +remains unchanged. + + When match_type is +V4L2_CHIP_MATCH_HOST, +match_chip selects the nth non-&i2c; chip +on the TV card. You can enumerate all chips by starting at zero and +incrementing match_chip by one until +VIDIOC_G_CHIP_IDENT fails with an &EINVAL;. +Drivers may also interpret match_chip as a +random ID, but we recommend against that. The number zero always +selects the host chip, ⪚ the chip connected to the PCI bus. + + When match_type is +V4L2_CHIP_MATCH_I2C_DRIVER, +match_chip contains a driver ID as defined +in the linux/i2c-id.h header file. For instance +I2C_DRIVERID_SAA7127 will match any chip +supported by the saa7127 driver, regardless of its &i2c; bus address. +When multiple chips supported by the same driver are present, the +ioctl will return V4L2_IDENT_AMBIGUOUS in the +ident field. + + When match_type is +V4L2_CHIP_MATCH_I2C_ADDR, +match_chip selects a chip by its 7 bit +&i2c; bus address. + + On success, the ident field will +contain a chip ID from the Linux +media/v4l2-chip-ident.h header file, and the +revision field will contain a driver +specific value, or zero if no particular revision is associated with +this chip. + + When the driver could not identify the selected chip, +ident will contain +V4L2_IDENT_UNKNOWN. When no chip matched +match_type and +match_chip, the ioctl will succeed but the +ident field will contain +V4L2_IDENT_NONE. If multiple chips matched, +ident will contain +V4L2_IDENT_AMBIGUOUS. In all these cases the +revision field remains unchanged. + + This ioctl is optional, not all drivers may support it. It +was introduced in Linux 2.6.21. + + We recommended the v4l2-dbg +utility over calling this ioctl directly. It is available from the +LinuxTV v4l-dvb repository; see http://linuxtv.org/repo/ for +access instructions. + + + struct <structname>v4l2_chip_ident</structname> + + &cs-str; + + + __u32 + match_type + See for a list of +possible types. + + + __u32 + match_chip + Match a chip by this number, interpreted according +to the match_type field. + + + __u32 + ident + A chip identifier as defined in the Linux +media/v4l2-chip-ident.h header file, or one of +the values from . + + + __u32 + revision + A chip revision, chip and driver specific. + + + +
+ + + + Chip Match Types + + &cs-def; + + + V4L2_CHIP_MATCH_HOST + 0 + Match the nth chip on the card, zero for the + host chip. Does not match &i2c; chips. + + + V4L2_CHIP_MATCH_I2C_DRIVER + 1 + Match an &i2c; chip by its driver ID from the +linux/i2c-id.h header file. + + + V4L2_CHIP_MATCH_I2C_ADDR + 2 + Match a chip by its 7 bit &i2c; bus address. + + + +
+ + + + Chip Identifiers + + &cs-def; + + + V4L2_IDENT_NONE + 0 + No chip matched. + + + V4L2_IDENT_AMBIGUOUS + 1 + Multiple chips matched. + + + V4L2_IDENT_UNKNOWN + 2 + A chip is present at this address, but the driver +could not identify it. + + + +
+ + + + &return-value; + + + + EINVAL + + The driver does not support this ioctl, or the +match_type is invalid. + + + + + + + diff --git a/v4l2-spec/vidioc-g-crop.sgml b/v4l2-spec/vidioc-g-crop.sgml new file mode 100644 index 000000000..d235b1ded --- /dev/null +++ b/v4l2-spec/vidioc-g-crop.sgml @@ -0,0 +1,143 @@ + + + ioctl VIDIOC_G_CROP, VIDIOC_S_CROP + &manvol; + + + + VIDIOC_G_CROP + VIDIOC_S_CROP + Get or set the current cropping rectangle + + + + + + int ioctl + int fd + int request + struct v4l2_crop *argp + + + + + int ioctl + int fd + int request + const struct v4l2_crop *argp + + + + + + Arguments + + + + fd + + &fd; + + + + request + + VIDIOC_G_CROP, VIDIOC_S_CROP + + + + argp + + + + + + + + + Description + + To query the cropping rectangle size and position +applications set the type field of a +v4l2_crop structure to the respective buffer +(stream) type and call the VIDIOC_G_CROP ioctl +with a pointer to this structure. The driver fills the rest of the +structure or returns the &EINVAL; if cropping is not supported. + + To change the cropping rectangle applications initialize the +type and &v4l2-rect; substructure named +c of a v4l2_crop structure and call the +VIDIOC_S_CROP ioctl with a pointer to this +structure. + + The driver first adjusts the requested dimensions against +hardware limits, &ie; the bounds given by the capture/output window, +and it rounds to the closest possible values of horizontal and +vertical offset, width and height. In particular the driver must round +the vertical offset of the cropping rectangle to frame lines modulo +two, such that the field order cannot be confused. + + Second the driver adjusts the image size (the opposite +rectangle of the scaling process, source or target depending on the +data direction) to the closest size possible while maintaining the +current horizontal and vertical scaling factor. + + Finally the driver programs the hardware with the actual +cropping and image parameters. VIDIOC_S_CROP is a +write-only ioctl, it does not return the actual parameters. To query +them applications must call VIDIOC_G_CROP and +&VIDIOC-G-FMT;. When the parameters are unsuitable the application may +modify the cropping or image parameters and repeat the cycle until +satisfactory parameters have been negotiated. + + When cropping is not supported then no parameters are +changed and VIDIOC_S_CROP returns the +&EINVAL;. + + + struct <structname>v4l2_crop</structname> + + &cs-str; + + + &v4l2-buf-type; + type + Type of the data stream, set by the application. +Only these types are valid here: V4L2_BUF_TYPE_VIDEO_CAPTURE, +V4L2_BUF_TYPE_VIDEO_OUTPUT, +V4L2_BUF_TYPE_VIDEO_OVERLAY, and custom (driver +defined) types with code V4L2_BUF_TYPE_PRIVATE +and higher. + + + &v4l2-rect; + c + Cropping rectangle. The same co-ordinate system as +for &v4l2-cropcap; bounds is used. + + + +
+ + + + &return-value; + + + + EINVAL + + Cropping is not supported. + + + + + + + diff --git a/v4l2-spec/vidioc-g-ctrl.sgml b/v4l2-spec/vidioc-g-ctrl.sgml new file mode 100644 index 000000000..8b5e6ff7f --- /dev/null +++ b/v4l2-spec/vidioc-g-ctrl.sgml @@ -0,0 +1,130 @@ + + + ioctl VIDIOC_G_CTRL, VIDIOC_S_CTRL + &manvol; + + + + VIDIOC_G_CTRL + VIDIOC_S_CTRL + Get or set the value of a control + + + + + + int ioctl + int fd + int request + struct v4l2_control +*argp + + + + + + Arguments + + + + fd + + &fd; + + + + request + + VIDIOC_G_CTRL, VIDIOC_S_CTRL + + + + argp + + + + + + + + + Description + + To get the current value of a control applications +initialize the id field of a struct +v4l2_control and call the +VIDIOC_G_CTRL ioctl with a pointer to this +structure. To change the value of a control applications initialize +the id and value +fields of a struct v4l2_control and call the +VIDIOC_S_CTRL ioctl. + + When the id is invalid drivers +return an &EINVAL;. When the value is out +of bounds drivers can choose to take the closest valid value or return +an &ERANGE;, whatever seems more appropriate. However, +VIDIOC_S_CTRL is a write-only ioctl, it does not +return the actual new value. + + These ioctls work only with user controls. For other +control classes the &VIDIOC-G-EXT-CTRLS;, &VIDIOC-S-EXT-CTRLS; or +&VIDIOC-TRY-EXT-CTRLS; must be used. + + + struct <structname>v4l2_control</structname> + + &cs-str; + + + __u32 + id + Identifies the control, set by the +application. + + + __s32 + value + New value or current value. + + + +
+ + + + &return-value; + + + + EINVAL + + The &v4l2-control; id is +invalid. + + + + ERANGE + + The &v4l2-control; value +is out of bounds. + + + + EBUSY + + The control is temporarily not changeable, possibly +because another applications took over control of the device function +this control belongs to. + + + + + + + diff --git a/v4l2-spec/vidioc-g-enc-index.sgml b/v4l2-spec/vidioc-g-enc-index.sgml new file mode 100644 index 000000000..bc4153647 --- /dev/null +++ b/v4l2-spec/vidioc-g-enc-index.sgml @@ -0,0 +1,213 @@ + + + ioctl VIDIOC_G_ENC_INDEX + &manvol; + + + + VIDIOC_G_ENC_INDEX + Get meta data about a compressed video stream + + + + + + int ioctl + int fd + int request + struct v4l2_enc_idx *argp + + + + + + Arguments + + + + fd + + &fd; + + + + request + + VIDIOC_G_ENC_INDEX + + + + argp + + + + + + + + + Description + + + Experimental + + This is an experimental +interface and may change in the future. + + + The VIDIOC_G_ENC_INDEX ioctl provides +meta data about a compressed video stream the same or another +application currently reads from the driver, which is useful for +random access into the stream without decoding it. + + To read the data applications must call +VIDIOC_G_ENC_INDEX with a pointer to a +&v4l2-enc-idx;. On success the driver fills the +entry array, stores the number of elements +written in the entries field, and +initializes the entries_cap field. + + Each element of the entry array +contains meta data about one picture. A +VIDIOC_G_ENC_INDEX call reads up to +V4L2_ENC_IDX_ENTRIES entries from a driver +buffer, which can hold up to entries_cap +entries. This number can be lower or higher than +V4L2_ENC_IDX_ENTRIES, but not zero. When the +application fails to read the meta data in time the oldest entries +will be lost. When the buffer is empty or no capturing/encoding is in +progress, entries will be zero. + + Currently this ioctl is only defined for MPEG-2 program +streams and video elementary streams. + + + struct <structname>v4l2_enc_idx</structname> + + &cs-str; + + + __u32 + entries + The number of entries the driver stored in the +entry array. + + + __u32 + entries_cap + The number of entries the driver can +buffer. Must be greater than zero. + + + __u32 + reserved[4] + Reserved for future extensions. +Drivers must set the array to zero. + + + &v4l2-enc-idx-entry; + entry[V4L2_ENC_IDX_ENTRIES] + Meta data about a compressed video stream. Each +element of the array corresponds to one picture, sorted in ascending +order by their offset. + + + +
+ + + struct <structname>v4l2_enc_idx_entry</structname> + + &cs-str; + + + __u64 + offset + The offset in bytes from the beginning of the +compressed video stream to the beginning of this picture, that is a +PES packet header as defined in or a picture +header as defined in . When +the encoder is stopped, the driver resets the offset to zero. + + + __u64 + pts + The 33 bit Presentation Time +Stamp of this picture as defined in . + + + __u32 + length + The length of this picture in bytes. + + + __u32 + flags + Flags containing the coding type of this picture, see . + + + __u32 + reserved[2] + Reserved for future extensions. +Drivers must set the array to zero. + + + +
+ + + Index Entry Flags + + &cs-def; + + + V4L2_ENC_IDX_FRAME_I + 0x00 + This is an Intra-coded picture. + + + V4L2_ENC_IDX_FRAME_P + 0x01 + This is a Predictive-coded picture. + + + V4L2_ENC_IDX_FRAME_B + 0x02 + This is a Bidirectionally predictive-coded +picture. + + + V4L2_ENC_IDX_FRAME_MASK + 0x0F + AND the flags field with +this mask to obtain the picture coding type. + + + +
+ + + + &return-value; + + + + EINVAL + + The driver does not support this ioctl. + + + + + + + diff --git a/v4l2-spec/vidioc-g-ext-ctrls.sgml b/v4l2-spec/vidioc-g-ext-ctrls.sgml new file mode 100644 index 000000000..510520254 --- /dev/null +++ b/v4l2-spec/vidioc-g-ext-ctrls.sgml @@ -0,0 +1,254 @@ + + + ioctl VIDIOC_G_EXT_CTRLS, VIDIOC_S_EXT_CTRLS, +VIDIOC_TRY_EXT_CTRLS + &manvol; + + + + VIDIOC_G_EXT_CTRLS + VIDIOC_S_EXT_CTRLS + VIDIOC_TRY_EXT_CTRLS + Get or set the value of several controls, try control +values + + + + + + int ioctl + int fd + int request + struct v4l2_ext_controls +*argp + + + + + + Arguments + + + + fd + + &fd; + + + + request + + VIDIOC_G_EXT_CTRLS, VIDIOC_S_EXT_CTRLS, +VIDIOC_TRY_EXT_CTRLS + + + + argp + + + + + + + + + Description + + These ioctls allow the caller to get or set multiple +controls atomically. Control IDs are grouped into control classes (see +) and all controls in the control array +must belong to the same control class. + + Applications must always fill in the +count, +ctrl_class, +controls and +reserved fields of &v4l2-ext-controls;, and +initialize the &v4l2-ext-control; array pointed to by the +controls fields. + + To get the current value of a set of controls applications +initialize the id field of each +&v4l2-ext-control; and call the +VIDIOC_G_EXT_CTRLS ioctl. + + To change the value of a set of controls applications +initialize the id and +value fields of a &v4l2-ext-control; and +call the VIDIOC_S_EXT_CTRLS ioctl. The controls +will only be set if all control values are +valid. + + To check if the a set of controls have correct values +applications initialize the id and +value fields of a &v4l2-ext-control; and +call the VIDIOC_TRY_EXT_CTRLS ioctl. It is up to +the driver whether wrong values are automatically adjusted to a valid +value or if an error is returned. + + When the id or +ctrl_class is invalid drivers return an +&EINVAL;. When the value is out of bounds drivers can choose to take +the closest valid value or return an &ERANGE;, whatever seems more +appropriate. In the first case the new value is set in +&v4l2-ext-control;. + + The driver will only set/get these controls if all control +values are correct. This prevents the situation where only some of the +controls were set/get. Only low-level errors (⪚ a failed i2c +command) can still cause this situation. + + + struct <structname>v4l2_ext_control</structname> + + &cs-ustr; + + + __u32 + id + + Identifies the control, set by the +application. + + + __u32 + reserved2[2] + + Reserved for future extensions. Drivers and +applications must set the array to zero. + + + union + (anonymous) + + + + __s32 + value + New value or current value. + + + + __s64 + value64 + New value or current value. + + + + void * + reserved + Reserved for future pointer-type controls. Currently unused. + + + +
+ + + struct <structname>v4l2_ext_controls</structname> + + &cs-str; + + + __u32 + ctrl_class + The control class to which all controls belong, see +. + + + __u32 + count + The number of controls in the controls array. May +also be zero. + + + __u32 + error_idx + Set by the driver in case of an error. It is the +index of the control causing the error or equal to 'count' when the +error is not associated with a particular control. Undefined when the +ioctl returns 0 (success). + + + __u32 + reserved[2] + Reserved for future extensions. Drivers and +applications must set the array to zero. + + + &v4l2-ext-control; * + controls + Pointer to an array of +count v4l2_ext_control structures. Ignored +if count equals zero. + + + +
+ + + Control classes + + &cs-def; + + + V4L2_CTRL_CLASS_USER + 0x980000 + The class containing user controls. These controls +are described in . All controls that can be set +using the &VIDIOC-S-CTRL; and &VIDIOC-G-CTRL; ioctl belong to this +class. + + + V4L2_CTRL_CLASS_MPEG + 0x990000 + The class containing MPEG compression controls. +These controls are described in section . + + + +
+ + + + + &return-value; + + + + EINVAL + + The &v4l2-ext-control; id +is invalid or the &v4l2-ext-controls; +ctrl_class is invalid. This error code is +also returned by the VIDIOC_S_EXT_CTRLS and +VIDIOC_TRY_EXT_CTRLS ioctls if two or more +control values are in conflict. + + + + ERANGE + + The &v4l2-ext-control; value +is out of bounds. + + + + EBUSY + + The control is temporarily not changeable, possibly +because another applications took over control of the device function +this control belongs to. + + + + + + + diff --git a/v4l2-spec/vidioc-g-fbuf.sgml b/v4l2-spec/vidioc-g-fbuf.sgml new file mode 100644 index 000000000..3e4ac2952 --- /dev/null +++ b/v4l2-spec/vidioc-g-fbuf.sgml @@ -0,0 +1,435 @@ + + + ioctl VIDIOC_G_FBUF, VIDIOC_S_FBUF + &manvol; + + + + VIDIOC_G_FBUF + VIDIOC_S_FBUF + Get or set frame buffer overlay parameters + + + + + + int ioctl + int fd + int request + struct v4l2_framebuffer *argp + + + + + int ioctl + int fd + int request + const struct v4l2_framebuffer *argp + + + + + + Arguments + + + + fd + + &fd; + + + + request + + VIDIOC_G_FBUF, VIDIOC_S_FBUF + + + + argp + + + + + + + + + Description + + Applications can use the VIDIOC_G_FBUF and +VIDIOC_S_FBUF ioctl to get and set the +framebuffer parameters for a Video +Overlay or Video Output Overlay +(OSD). The type of overlay is implied by the device type (capture or +output device) and can be determined with the &VIDIOC-QUERYCAP; ioctl. +One /dev/videoN device must not support both +kinds of overlay. + + The V4L2 API distinguishes destructive and non-destructive +overlays. A destructive overlay copies captured video images into the +video memory of a graphics card. A non-destructive overlay blends +video images into a VGA signal or graphics into a video signal. +Video Output Overlays are always +non-destructive. + + To get the current parameters applications call the +VIDIOC_G_FBUF ioctl with a pointer to a +v4l2_framebuffer structure. The driver fills +all fields of the structure or returns an &EINVAL; when overlays are +not supported. + + To set the parameters for a Video Output +Overlay, applications must initialize the +flags field of a struct +v4l2_framebuffer. Since the framebuffer is +implemented on the TV card all other parameters are determined by the +driver. When an application calls VIDIOC_S_FBUF +with a pointer to this structure, the driver prepares for the overlay +and returns the framebuffer parameters as +VIDIOC_G_FBUF does, or it returns an error +code. + + To set the parameters for a non-destructive +Video Overlay, applications must initialize the +flags field, the +fmt substructure, and call +VIDIOC_S_FBUF. Again the driver prepares for the +overlay and returns the framebuffer parameters as +VIDIOC_G_FBUF does, or it returns an error +code. + + For a destructive Video Overlay +applications must additionally provide a +base address. Setting up a DMA to a +random memory location can jeopardize the system security, its +stability or even damage the hardware, therefore only the superuser +can set the parameters for a destructive video overlay. + + + + + struct <structname>v4l2_framebuffer</structname> + + &cs-ustr; + + + __u32 + capability + + Overlay capability flags set by the driver, see +. + + + __u32 + flags + + Overlay control flags set by application and +driver, see + + + void * + base + + Physical base address of the framebuffer, +that is the address of the pixel in the top left corner of the +framebuffer.A physical base address may not suit all +platforms. GK notes in theory we should pass something like PCI device ++ memory region + offset instead. If you encounter problems please +discuss on the Video4Linux mailing list: +&v4l-ml;.This field is irrelevant to +non-destructive Video Overlays. For +destructive Video Overlays applications must +provide a base address. The driver may accept only base addresses +which are a multiple of two, four or eight bytes. For +Video Output Overlays the driver must return +a valid base address, so applications can find the corresponding Linux +framebuffer device (see ). + + + &v4l2-pix-format; + fmt + + Layout of the frame buffer. The +v4l2_pix_format structure is defined in , for clarification the fields and acceptable values + are listed below: + + + + __u32 + width + Width of the frame buffer in pixels. + + + + __u32 + height + Height of the frame buffer in pixels. + + + + __u32 + pixelformat + The pixel format of the +framebuffer.For non-destructive Video +Overlays this field only defines a format for the +&v4l2-window; chromakey +field.For destructive Video +Overlays applications must initialize this field. For +Video Output Overlays the driver must return +a valid format.Usually this is an RGB format (for example +V4L2_PIX_FMT_RGB565) +but YUV formats (only packed YUV formats when chroma keying is used, +not including V4L2_PIX_FMT_YUYV and +V4L2_PIX_FMT_UYVY) and the +V4L2_PIX_FMT_PAL8 format are also permitted. The +behavior of the driver when an application requests a compressed +format is undefined. See for information on +pixel formats. + + + + &v4l2-field; + field + Drivers and applications shall ignore this field. +If applicable, the field order is selected with the &VIDIOC-S-FMT; +ioctl, using the field field of +&v4l2-window;. + + + + __u32 + bytesperline + Distance in bytes between the leftmost pixels in +two adjacent lines. + + + This field is irrelevant to +non-destructive Video +Overlays.For destructive Video +Overlays both applications and drivers can set this field +to request padding bytes at the end of each line. Drivers however may +ignore the requested value, returning width +times bytes-per-pixel or a larger value required by the hardware. That +implies applications can just set this field to zero to get a +reasonable default.For Video Output +Overlays the driver must return a valid +value.Video hardware may access padding bytes, therefore +they must reside in accessible memory. Consider for example the case +where padding bytes after the last line of an image cross a system +page boundary. Capture devices may write padding bytes, the value is +undefined. Output devices ignore the contents of padding +bytes.When the image format is planar the +bytesperline value applies to the largest +plane and is divided by the same factor as the +width field for any smaller planes. For +example the Cb and Cr planes of a YUV 4:2:0 image have half as many +padding bytes following each line as the Y plane. To avoid ambiguities +drivers must return a bytesperline value +rounded up to a multiple of the scale factor. + + + + __u32 + sizeimage + This field is irrelevant to +non-destructive Video Overlays. For +destructive Video Overlays applications must +initialize this field. For Video Output +Overlays the driver must return a valid +format.Together with base it +defines the framebuffer memory accessible by the +driver. + + + + &v4l2-colorspace; + colorspace + This information supplements the +pixelformat and must be set by the driver, +see . + + + + __u32 + priv + Reserved for additional information about custom +(driver defined) formats. When not used drivers and applications must +set this field to zero. + + + +
+ + + Frame Buffer Capability Flags + + &cs-def; + + + V4L2_FBUF_CAP_EXTERNOVERLAY + 0x0001 + The device is capable of non-destructive overlays. +When the driver clears this flag, only destructive overlays are +supported. There are no drivers yet which support both destructive and +non-destructive overlays. + + + V4L2_FBUF_CAP_CHROMAKEY + 0x0002 + The device supports clipping by chroma-keying the +images. That is, image pixels replace pixels in the VGA or video +signal only where the latter assume a certain color. Chroma-keying +makes no sense for destructive overlays. + + + V4L2_FBUF_CAP_LIST_CLIPPING + 0x0004 + The device supports clipping using a list of clip +rectangles. + + + V4L2_FBUF_CAP_BITMAP_CLIPPING + 0x0008 + The device supports clipping using a bit mask. + + + V4L2_FBUF_CAP_LOCAL_ALPHA + 0x0010 + The device supports clipping/blending using the +alpha channel of the framebuffer or VGA signal. Alpha blending makes +no sense for destructive overlays. + + + V4L2_FBUF_CAP_GLOBAL_ALPHA + 0x0020 + The device supports alpha blending using a global +alpha value. Alpha blending makes no sense for destructive overlays. + + + V4L2_FBUF_CAP_LOCAL_INV_ALPHA + 0x0040 + The device supports clipping/blending using the +inverted alpha channel of the framebuffer or VGA signal. Alpha +blending makes no sense for destructive overlays. + + + +
+ + + Frame Buffer Flags + + &cs-def; + + + V4L2_FBUF_FLAG_PRIMARY + 0x0001 + The framebuffer is the primary graphics surface. +In other words, the overlay is destructive. [?] + + + V4L2_FBUF_FLAG_OVERLAY + 0x0002 + The frame buffer is an overlay surface the same +size as the capture. [?] + + + The purpose of +V4L2_FBUF_FLAG_PRIMARY and +V4L2_FBUF_FLAG_OVERLAY was never quite clear. +Most drivers seem to ignore these flags. For compatibility with the +bttv driver applications should set the +V4L2_FBUF_FLAG_OVERLAY flag. + + + V4L2_FBUF_FLAG_CHROMAKEY + 0x0004 + Use chroma-keying. The chroma-key color is +determined by the chromakey field of +&v4l2-window; and negotiated with the &VIDIOC-S-FMT; ioctl, see +and + . + + + There are no flags to enable +clipping using a list of clip rectangles or a bitmap. These methods +are negotiated with the &VIDIOC-S-FMT; ioctl, see and . + + + V4L2_FBUF_FLAG_LOCAL_ALPHA + 0x0008 + Use the alpha channel of the framebuffer to clip or +blend framebuffer pixels with video images. The blend +function is: output = framebuffer pixel * alpha + video pixel * (1 - +alpha). The actual alpha depth depends on the framebuffer pixel +format. + + + V4L2_FBUF_FLAG_GLOBAL_ALPHA + 0x0010 + Use a global alpha value to blend the framebuffer +with video images. The blend function is: output = (framebuffer pixel +* alpha + video pixel * (255 - alpha)) / 255. The alpha value is +determined by the global_alpha field of +&v4l2-window; and negotiated with the &VIDIOC-S-FMT; ioctl, see +and . + + + V4L2_FBUF_FLAG_LOCAL_INV_ALPHA + 0x0020 + Like +V4L2_FBUF_FLAG_LOCAL_ALPHA, use the alpha channel +of the framebuffer to clip or blend framebuffer pixels with video +images, but with an inverted alpha value. The blend function is: +output = framebuffer pixel * (1 - alpha) + video pixel * alpha. The +actual alpha depth depends on the framebuffer pixel format. + + + +
+ + + + &return-value; + + + + EPERM + + VIDIOC_S_FBUF can only be called +by a privileged user to negotiate the parameters for a destructive +overlay. + + + + EBUSY + + The framebuffer parameters cannot be changed at this +time because overlay is already enabled, or capturing is enabled +and the hardware cannot capture and overlay simultaneously. + + + + EINVAL + + The ioctl is not supported or the +VIDIOC_S_FBUF parameters are unsuitable. + + + + + + + diff --git a/v4l2-spec/vidioc-g-fmt.sgml b/v4l2-spec/vidioc-g-fmt.sgml new file mode 100644 index 000000000..0a466b2c7 --- /dev/null +++ b/v4l2-spec/vidioc-g-fmt.sgml @@ -0,0 +1,201 @@ + + + ioctl VIDIOC_G_FMT, VIDIOC_S_FMT, +VIDIOC_TRY_FMT + &manvol; + + + + VIDIOC_G_FMT + VIDIOC_S_FMT + VIDIOC_TRY_FMT + Get or set the data format, try a format + + + + + + int ioctl + int fd + int request + struct v4l2_format +*argp + + + + + + Arguments + + + + fd + + &fd; + + + + request + + VIDIOC_G_FMT, VIDIOC_S_FMT, VIDIOC_TRY_FMT + + + + argp + + + + + + + + + Description + + These ioctls are used to negotiate the format of data +(typically image format) exchanged between driver and +application. + + To query the current parameters applications set the +type field of a struct +v4l2_format to the respective buffer (stream) +type. For example video capture devices use +V4L2_BUF_TYPE_VIDEO_CAPTURE. When the application +calls the VIDIOC_G_FMT ioctl with a pointer to +this structure the driver fills the respective member of the +fmt union. In case of video capture devices +that is the &v4l2-pix-format; pix member. +When the requested buffer type is not supported drivers return an +&EINVAL;. + + To change the current format parameters applications +initialize the type field and all +fields of the respective fmt +union member. For details see the documentation of the various devices +types in . Good practice is to query the +current parameters first, and to +modify only those parameters not suitable for the application. When +the application calls the VIDIOC_S_FMT ioctl +with a pointer to a v4l2_format structure +the driver checks +and adjusts the parameters against hardware abilities. Drivers +should not return an error code unless the input is ambiguous, this is +a mechanism to fathom device capabilities and to approach parameters +acceptable for both the application and driver. On success the driver +may program the hardware, allocate resources and generally prepare for +data exchange. +Finally the VIDIOC_S_FMT ioctl returns the +current format parameters as VIDIOC_G_FMT does. +Very simple, inflexible devices may even ignore all input and always +return the default parameters. However all V4L2 devices exchanging +data with the application must implement the +VIDIOC_G_FMT and +VIDIOC_S_FMT ioctl. When the requested buffer +type is not supported drivers return an &EINVAL; on a +VIDIOC_S_FMT attempt. When I/O is already in +progress or the resource is not available for other reasons drivers +return the &EBUSY;. + + The VIDIOC_TRY_FMT ioctl is equivalent +to VIDIOC_S_FMT with one exception: it does not +change driver state. It can also be called at any time, never +returning EBUSY. This function is provided to +negotiate parameters, to learn about hardware limitations, without +disabling I/O or possibly time consuming hardware preparations. +Although strongly recommended drivers are not required to implement +this ioctl. + + + struct <structname>v4l2_format</structname> + + + + + + + + &v4l2-buf-type; + type + + Type of the data stream, see . + + + union + fmt + + + + &v4l2-pix-format; + pix + Definition of an image format, see , used by video capture and output +devices. + + + + &v4l2-window; + win + Definition of an overlaid image, see , used by video overlay devices. + + + + &v4l2-vbi-format; + vbi + Raw VBI capture or output parameters. This is +discussed in more detail in . Used by raw VBI +capture and output devices. + + + + &v4l2-sliced-vbi-format; + sliced + Sliced VBI capture or output parameters. See + for details. Used by sliced VBI +capture and output devices. + + + + __u8 + raw_data[200] + Place holder for future extensions and custom +(driver defined) formats with type +V4L2_BUF_TYPE_PRIVATE and higher. + + + +
+ + + + &return-value; + + + + EBUSY + + The data format cannot be changed at this +time, for example because I/O is already in progress. + + + + EINVAL + + The &v4l2-format; type +field is invalid, the requested buffer type not supported, or +VIDIOC_TRY_FMT was called and is not +supported with this buffer type. + + + + + + + diff --git a/v4l2-spec/vidioc-g-frequency.sgml b/v4l2-spec/vidioc-g-frequency.sgml new file mode 100644 index 000000000..e655a61ff --- /dev/null +++ b/v4l2-spec/vidioc-g-frequency.sgml @@ -0,0 +1,145 @@ + + + ioctl VIDIOC_G_FREQUENCY, VIDIOC_S_FREQUENCY + &manvol; + + + + VIDIOC_G_FREQUENCY + VIDIOC_S_FREQUENCY + Get or set tuner or modulator radio +frequency + + + + + + int ioctl + int fd + int request + struct v4l2_frequency +*argp + + + + + int ioctl + int fd + int request + const struct v4l2_frequency +*argp + + + + + + Arguments + + + + fd + + &fd; + + + + request + + VIDIOC_G_FREQUENCY, VIDIOC_S_FREQUENCY + + + + argp + + + + + + + + + Description + + To get the current tuner or modulator radio frequency +applications set the tuner field of a +&v4l2-frequency; to the respective tuner or modulator number (only +input devices have tuners, only output devices have modulators), zero +out the reserved array and +call the VIDIOC_G_FREQUENCY ioctl with a pointer +to this structure. The driver stores the current frequency in the +frequency field. + + To change the current tuner or modulator radio frequency +applications initialize the tuner, +type and +frequency fields, and the +reserved array of a &v4l2-frequency; and +call the VIDIOC_S_FREQUENCY ioctl with a pointer +to this structure. When the requested frequency is not possible the +driver assumes the closest possible value. However +VIDIOC_S_FREQUENCY is a write-only ioctl, it does +not return the actual new frequency. + + + struct <structname>v4l2_frequency</structname> + + &cs-str; + + + __u32 + tuner + The tuner or modulator index number. This is the +same value as in the &v4l2-input; tuner +field and the &v4l2-tuner; index field, or +the &v4l2-output; modulator field and the +&v4l2-modulator; index field. + + + &v4l2-tuner-type; + type + The tuner type. This is the same value as in the +&v4l2-tuner; type field. The field is not +applicable to modulators, &ie; ignored by drivers. + + + __u32 + frequency + Tuning frequency in units of 62.5 kHz, or if the +&v4l2-tuner; or &v4l2-modulator; capabilities flag +V4L2_TUNER_CAP_LOW is set, in units of 62.5 +Hz. + + + __u32 + reserved[8]; + Reserved for future extensions. Drivers and + applications must set the array to zero. + + + +
+ + + + &return-value; + + + + EINVAL + + The tuner index is out of +bounds or the value in the type field is +wrong. + + + + + + + diff --git a/v4l2-spec/vidioc-g-input.sgml b/v4l2-spec/vidioc-g-input.sgml new file mode 100644 index 000000000..ed076e927 --- /dev/null +++ b/v4l2-spec/vidioc-g-input.sgml @@ -0,0 +1,100 @@ + + + ioctl VIDIOC_G_INPUT, VIDIOC_S_INPUT + &manvol; + + + + VIDIOC_G_INPUT + VIDIOC_S_INPUT + Query or select the current video input + + + + + + int ioctl + int fd + int request + int *argp + + + + + + Arguments + + + + fd + + &fd; + + + + request + + VIDIOC_G_INPUT, VIDIOC_S_INPUT + + + + argp + + + + + + + + + Description + + To query the current video input applications call the +VIDIOC_G_INPUT ioctl with a pointer to an integer +where the driver stores the number of the input, as in the +&v4l2-input; index field. This ioctl will +fail only when there are no video inputs, returning +EINVAL. + + To select a video input applications store the number of the +desired input in an integer and call the +VIDIOC_S_INPUT ioctl with a pointer to this +integer. Side effects are possible. For example inputs may support +different video standards, so the driver may implicitly switch the +current standard. It is good practice to select an input before +querying or negotiating any other parameters. + + Information about video inputs is available using the +&VIDIOC-ENUMINPUT; ioctl. + + + + &return-value; + + + + EINVAL + + The number of the video input is out of bounds, or +there are no video inputs at all and this ioctl is not +supported. + + + + EBUSY + + I/O is in progress, the input cannot be +switched. + + + + + + + diff --git a/v4l2-spec/vidioc-g-jpegcomp.sgml b/v4l2-spec/vidioc-g-jpegcomp.sgml new file mode 100644 index 000000000..0755b834b --- /dev/null +++ b/v4l2-spec/vidioc-g-jpegcomp.sgml @@ -0,0 +1,180 @@ + + + ioctl VIDIOC_G_JPEGCOMP, VIDIOC_S_JPEGCOMP + &manvol; + + + + VIDIOC_G_JPEGCOMP + VIDIOC_S_JPEGCOMP + + + + + + + int ioctl + int fd + int request + v4l2_jpegcompression *argp + + + + + int ioctl + int fd + int request + const v4l2_jpegcompression *argp + + + + + + Arguments + + + + fd + + &fd; + + + + request + + VIDIOC_G_JPEGCOMP, VIDIOC_S_JPEGCOMP + + + + argp + + + + + + + + + Description + + [to do] + + Ronald Bultje elaborates: + + + + APP is some application-specific information. The +application can set it itself, and it'll be stored in the JPEG-encoded +fields (eg; interlacing information for in an AVI or so). COM is the +same, but it's comments, like 'encoded by me' or so. + + jpeg_markers describes whether the huffman tables, +quantization tables and the restart interval information (all +JPEG-specific stuff) should be stored in the JPEG-encoded fields. +These define how the JPEG field is encoded. If you omit them, +applications assume you've used standard encoding. You usually do want +to add them. + + + + + struct <structname>v4l2_jpegcompression</structname> + + &cs-str; + + + int + quality + + + + int + APPn + + + + int + APP_len + + + + char + APP_data[60] + + + + int + COM_len + + + + char + COM_data[60] + + + + __u32 + jpeg_markers + See . + + + +
+ + + JPEG Markers Flags + + &cs-def; + + + V4L2_JPEG_MARKER_DHT + (1<<3) + Define Huffman Tables + + + V4L2_JPEG_MARKER_DQT + (1<<4) + Define Quantization Tables + + + V4L2_JPEG_MARKER_DRI + (1<<5) + Define Restart Interval + + + V4L2_JPEG_MARKER_COM + (1<<6) + Comment segment + + + V4L2_JPEG_MARKER_APP + (1<<7) + App segment, driver will always use APP0 + + + +
+ + + + &return-value; + + + + EINVAL + + This ioctl is not supported. + + + + + + + diff --git a/v4l2-spec/vidioc-g-modulator.sgml b/v4l2-spec/vidioc-g-modulator.sgml new file mode 100644 index 000000000..e5d4a3f24 --- /dev/null +++ b/v4l2-spec/vidioc-g-modulator.sgml @@ -0,0 +1,240 @@ + + + ioctl VIDIOC_G_MODULATOR, VIDIOC_S_MODULATOR + &manvol; + + + + VIDIOC_G_MODULATOR + VIDIOC_S_MODULATOR + Get or set modulator attributes + + + + + + int ioctl + int fd + int request + struct v4l2_modulator +*argp + + + + + int ioctl + int fd + int request + const struct v4l2_modulator +*argp + + + + + + Arguments + + + + fd + + &fd; + + + + request + + VIDIOC_G_MODULATOR, VIDIOC_S_MODULATOR + + + + argp + + + + + + + + + Description + + To query the attributes of a modulator applications initialize +the index field and zero out the +reserved array of a &v4l2-modulator; and +call the VIDIOC_G_MODULATOR ioctl with a pointer +to this structure. Drivers fill the rest of the structure or return an +&EINVAL; when the index is out of bounds. To enumerate all modulators +applications shall begin at index zero, incrementing by one until the +driver returns EINVAL. + + Modulators have two writable properties, an audio +modulation set and the radio frequency. To change the modulated audio +subprograms, applications initialize the index + and txsubchans fields and the +reserved array and call the +VIDIOC_S_MODULATOR ioctl. Drivers may choose a +different audio modulation if the request cannot be satisfied. However +this is a write-only ioctl, it does not return the actual audio +modulation selected. + + To change the radio frequency the &VIDIOC-S-FREQUENCY; ioctl +is available. + + + struct <structname>v4l2_modulator</structname> + + &cs-str; + + + __u32 + index + Identifies the modulator, set by the +application. + + + __u8 + name[32] + Name of the modulator, a NUL-terminated ASCII +string. This information is intended for the user. + + + __u32 + capability + Modulator capability flags. No flags are defined +for this field, the tuner flags in &v4l2-tuner; +are used accordingly. The audio flags indicate the ability +to encode audio subprograms. They will not +change for example with the current video standard. + + + __u32 + rangelow + The lowest tunable frequency in units of 62.5 +KHz, or if the capability flag +V4L2_TUNER_CAP_LOW is set, in units of 62.5 +Hz. + + + __u32 + rangehigh + The highest tunable frequency in units of 62.5 +KHz, or if the capability flag +V4L2_TUNER_CAP_LOW is set, in units of 62.5 +Hz. + + + __u32 + txsubchans + With this field applications can determine how +audio sub-carriers shall be modulated. It contains a set of flags as +defined in . Note the tuner +rxsubchans flags are reused, but the +semantics are different. Video output devices are assumed to have an +analog or PCM audio input with 1-3 channels. The +txsubchans flags select one or more +channels for modulation, together with some audio subprogram +indicator, for example a stereo pilot tone. + + + __u32 + reserved[4] + Reserved for future extensions. Drivers and +applications must set the array to zero. + + + +
+ + + Modulator Audio Transmission Flags + + &cs-def; + + + V4L2_TUNER_SUB_MONO + 0x0001 + Modulate channel 1 as mono audio, when the input +has more channels, a down-mix of channel 1 and 2. This flag does not +combine with V4L2_TUNER_SUB_STEREO or +V4L2_TUNER_SUB_LANG1. + + + V4L2_TUNER_SUB_STEREO + 0x0002 + Modulate channel 1 and 2 as left and right +channel of a stereo audio signal. When the input has only one channel +or two channels and V4L2_TUNER_SUB_SAP is also +set, channel 1 is encoded as left and right channel. This flag does +not combine with V4L2_TUNER_SUB_MONO or +V4L2_TUNER_SUB_LANG1. When the driver does not +support stereo audio it shall fall back to mono. + + + V4L2_TUNER_SUB_LANG1 + 0x0008 + Modulate channel 1 and 2 as primary and secondary +language of a bilingual audio signal. When the input has only one +channel it is used for both languages. It is not possible to encode +the primary or secondary language only. This flag does not combine +with V4L2_TUNER_SUB_MONO or +V4L2_TUNER_SUB_STEREO. If the hardware does not +support the respective audio matrix, or the current video standard +does not permit bilingual audio the +VIDIOC_S_MODULATOR ioctl shall return an &EINVAL; +and the driver shall fall back to mono or stereo mode. + + + V4L2_TUNER_SUB_LANG2 + 0x0004 + Same effect as +V4L2_TUNER_SUB_LANG1. + + + V4L2_TUNER_SUB_SAP + 0x0004 + When combined with V4L2_TUNER_SUB_MONO + the first channel is encoded as mono audio, the last +channel as Second Audio Program. When the input has only one channel +it is used for both audio tracks. When the input has three channels +the mono track is a down-mix of channel 1 and 2. When combined with +V4L2_TUNER_SUB_STEREO channel 1 and 2 are +encoded as left and right stereo audio, channel 3 as Second Audio +Program. When the input has only two channels, the first is encoded as +left and right channel and the second as SAP. When the input has only +one channel it is used for all audio tracks. It is not possible to +encode a Second Audio Program only. This flag must combine with +V4L2_TUNER_SUB_MONO or +V4L2_TUNER_SUB_STEREO. If the hardware does not +support the respective audio matrix, or the current video standard +does not permit SAP the VIDIOC_S_MODULATOR ioctl +shall return an &EINVAL; and driver shall fall back to mono or stereo +mode. + + + +
+ + + + &return-value; + + + + EINVAL + + The &v4l2-modulator; +index is out of bounds. + + + + + + + diff --git a/v4l2-spec/vidioc-g-output.sgml b/v4l2-spec/vidioc-g-output.sgml new file mode 100644 index 000000000..3ea8c0ed8 --- /dev/null +++ b/v4l2-spec/vidioc-g-output.sgml @@ -0,0 +1,100 @@ + + + ioctl VIDIOC_G_OUTPUT, VIDIOC_S_OUTPUT + &manvol; + + + + VIDIOC_G_OUTPUT + VIDIOC_S_OUTPUT + Query or select the current video output + + + + + + int ioctl + int fd + int request + int *argp + + + + + + Arguments + + + + fd + + &fd; + + + + request + + VIDIOC_G_OUTPUT, VIDIOC_S_OUTPUT + + + + argp + + + + + + + + + Description + + To query the current video output applications call the +VIDIOC_G_OUTPUT ioctl with a pointer to an integer +where the driver stores the number of the output, as in the +&v4l2-output; index field. This ioctl +will fail only when there are no video outputs, returning the +&EINVAL;. + + To select a video output applications store the number of the +desired output in an integer and call the +VIDIOC_S_OUTPUT ioctl with a pointer to this integer. +Side effects are possible. For example outputs may support different +video standards, so the driver may implicitly switch the current +standard. It is good practice to select an output before querying or +negotiating any other parameters. + + Information about video outputs is available using the +&VIDIOC-ENUMOUTPUT; ioctl. + + + + &return-value; + + + + EINVAL + + The number of the video output is out of bounds, or +there are no video outputs at all and this ioctl is not +supported. + + + + EBUSY + + I/O is in progress, the output cannot be +switched. + + + + + + + diff --git a/v4l2-spec/vidioc-g-parm.sgml b/v4l2-spec/vidioc-g-parm.sgml new file mode 100644 index 000000000..6ad43823e --- /dev/null +++ b/v4l2-spec/vidioc-g-parm.sgml @@ -0,0 +1,332 @@ + + + ioctl VIDIOC_G_PARM, VIDIOC_S_PARM + &manvol; + + + + VIDIOC_G_PARM + VIDIOC_S_PARM + Get or set streaming parameters + + + + + + int ioctl + int fd + int request + v4l2_streamparm *argp + + + + + + Arguments + + + + fd + + &fd; + + + + request + + VIDIOC_G_PARM, VIDIOC_S_PARM + + + + argp + + + + + + + + + Description + + The current video standard determines a nominal number of +frames per second. If less than this number of frames is to be +captured or output, applications can request frame skipping or +duplicating on the driver side. This is especially useful when using +the read() or write(), which +are not augmented by timestamps or sequence counters, and to avoid +unneccessary data copying. + + Further these ioctls can be used to determine the number of +buffers used internally by a driver in read/write mode. For +implications see the section discussing the &func-read; +function. + + To get and set the streaming parameters applications call +the VIDIOC_G_PARM and +VIDIOC_S_PARM ioctl, respectively. They take a +pointer to a struct v4l2_streamparm which +contains a union holding separate parameters for input and output +devices. + + + struct <structname>v4l2_streamparm</structname> + + &cs-ustr; + + + &v4l2-buf-type; + type + + The buffer (stream) type, same as &v4l2-format; +type, set by the application. + + + union + parm + + + + + + &v4l2-captureparm; + capture + Parameters for capture devices, used when +type is +V4L2_BUF_TYPE_VIDEO_CAPTURE. + + + + &v4l2-outputparm; + output + Parameters for output devices, used when +type is +V4L2_BUF_TYPE_VIDEO_OUTPUT. + + + + __u8 + raw_data[200] + A place holder for future extensions and custom +(driver defined) buffer types V4L2_BUF_TYPE_PRIVATE and +higher. + + + +
+ + + struct <structname>v4l2_captureparm</structname> + + &cs-str; + + + __u32 + capability + See . + + + __u32 + capturemode + Set by drivers and applications, see . + + + &v4l2-fract; + timeperframe + This is is the desired period between +successive frames captured by the driver, in seconds. The +field is intended to skip frames on the driver side, saving I/O +bandwidth.Applications store here the desired frame +period, drivers return the actual frame period, which must be greater +or equal to the nominal frame period determined by the current video +standard (&v4l2-standard; frameperiod +field). Changing the video standard (also implicitly by switching the +video input) may reset this parameter to the nominal frame period. To +reset manually applications can just set this field to +zero.Drivers support this function only when they set the +V4L2_CAP_TIMEPERFRAME flag in the +capability field. + + + __u32 + extendedmode + Custom (driver specific) streaming parameters. When +unused, applications and drivers must set this field to zero. +Applications using this field should check the driver name and +version, see . + + + __u32 + readbuffers + Applications set this field to the desired number +of buffers used internally by the driver in &func-read; mode. Drivers +return the actual number of buffers. When an application requests zero +buffers, drivers should just return the current setting rather than +the minimum or an error code. For details see . + + + __u32 + reserved[4] + Reserved for future extensions. Drivers and +applications must set the array to zero. + + + +
+ + + struct <structname>v4l2_outputparm</structname> + + &cs-str; + + + __u32 + capability + See . + + + __u32 + outputmode + Set by drivers and applications, see . + + + &v4l2-fract; + timeperframe + This is is the desired period between +successive frames output by the driver, in seconds. + + + The field is intended to +repeat frames on the driver side in &func-write; mode (in streaming +mode timestamps can be used to throttle the output), saving I/O +bandwidth.Applications store here the desired frame +period, drivers return the actual frame period, which must be greater +or equal to the nominal frame period determined by the current video +standard (&v4l2-standard; frameperiod +field). Changing the video standard (also implicitly by switching the +video output) may reset this parameter to the nominal frame period. To +reset manually applications can just set this field to +zero.Drivers support this function only when they set the +V4L2_CAP_TIMEPERFRAME flag in the +capability field. + + + __u32 + extendedmode + Custom (driver specific) streaming parameters. When +unused, applications and drivers must set this field to zero. +Applications using this field should check the driver name and +version, see . + + + __u32 + writebuffers + Applications set this field to the desired number +of buffers used internally by the driver in +write() mode. Drivers return the actual number of +buffers. When an application requests zero buffers, drivers should +just return the current setting rather than the minimum or an error +code. For details see . + + + __u32 + reserved[4] + Reserved for future extensions. Drivers and +applications must set the array to zero. + + + +
+ + + Streaming Parameters Capabilites + + &cs-def; + + + V4L2_CAP_TIMEPERFRAME + 0x1000 + The frame skipping/repeating controlled by the +timeperframe field is supported. + + + +
+ + + Capture Parameters Flags + + &cs-def; + + + V4L2_MODE_HIGHQUALITY + 0x0001 + High quality imaging mode. High quality mode +is intended for still imaging applications. The idea is to get the +best possible image quality that the hardware can deliver. It is not +defined how the driver writer may achieve that; it will depend on the +hardware and the ingenuity of the driver writer. High quality mode is +a different mode from the the regular motion video capture modes. In +high quality mode: + + The driver may be able to capture higher +resolutions than for motion capture. + + + The driver may support fewer pixel formats +than motion capture (eg; true color). + + + The driver may capture and arithmetically +combine multiple successive fields or frames to remove color edge +artifacts and reduce the noise in the video data. + + + + The driver may capture images in slices like +a scanner in order to handle larger format images than would otherwise +be possible. + + + An image capture operation may be +significantly slower than motion capture. + + + Moving objects in the image might have +excessive motion blur. + + + Capture might only work through the +read() call. + + + + + +
+ + + + + &return-value; + + + + EINVAL + + This ioctl is not supported. + + + + + + + diff --git a/v4l2-spec/vidioc-g-priority.sgml b/v4l2-spec/vidioc-g-priority.sgml new file mode 100644 index 000000000..5fb001978 --- /dev/null +++ b/v4l2-spec/vidioc-g-priority.sgml @@ -0,0 +1,144 @@ + + + ioctl VIDIOC_G_PRIORITY, VIDIOC_S_PRIORITY + &manvol; + + + + VIDIOC_G_PRIORITY + VIDIOC_S_PRIORITY + Query or request the access priority associated with a +file descriptor + + + + + + int ioctl + int fd + int request + enum v4l2_priority *argp + + + + + int ioctl + int fd + int request + const enum v4l2_priority *argp + + + + + + Arguments + + + + fd + + &fd; + + + + request + + VIDIOC_G_PRIORITY, VIDIOC_S_PRIORITY + + + + argp + + Pointer to an enum v4l2_priority type. + + + + + + + Description + + To query the current access priority +applications call the VIDIOC_G_PRIORITY ioctl +with a pointer to an enum v4l2_priority variable where the driver stores +the current priority. + + To request an access priority applications store the +desired priority in an enum v4l2_priority variable and call +VIDIOC_S_PRIORITY ioctl with a pointer to this +variable. + + + enum v4l2_priority + + &cs-def; + + + V4L2_PRIORITY_UNSET + 0 + + + + V4L2_PRIORITY_BACKGROUND + 1 + Lowest priority, usually applications running in +background, for example monitoring VBI transmissions. A proxy +application running in user space will be necessary if multiple +applications want to read from a device at this priority. + + + V4L2_PRIORITY_INTERACTIVE + 2 + + + + V4L2_PRIORITY_DEFAULT + 2 + Medium priority, usually applications started and +interactively controlled by the user. For example TV viewers, Teletext +browsers, or just "panel" applications to change the channel or video +controls. This is the default priority unless an application requests +another. + + + V4L2_PRIORITY_RECORD + 3 + Highest priority. Only one file descriptor can have +this priority, it blocks any other fd from changing device properties. +Usually applications which must not be interrupted, like video +recording. + + + +
+ + + + &return-value; + + + + EINVAL + + The requested priority value is invalid, or the +driver does not support access priorities. + + + + EBUSY + + Another application already requested higher +priority. + + + + + + + diff --git a/v4l2-spec/vidioc-g-sliced-vbi-cap.sgml b/v4l2-spec/vidioc-g-sliced-vbi-cap.sgml new file mode 100644 index 000000000..3568bacf1 --- /dev/null +++ b/v4l2-spec/vidioc-g-sliced-vbi-cap.sgml @@ -0,0 +1,264 @@ + + + ioctl VIDIOC_G_SLICED_VBI_CAP + &manvol; + + + + VIDIOC_G_SLICED_VBI_CAP + Query sliced VBI capabilities + + + + + + int ioctl + int fd + int request + struct v4l2_sliced_vbi_cap *argp + + + + + + Arguments + + + + fd + + &fd; + + + + request + + VIDIOC_G_SLICED_VBI_CAP + + + + argp + + + + + + + + + Description + + To find out which data services are supported by a sliced +VBI capture or output device, applications initialize the +type field of a &v4l2-sliced-vbi-cap;, +clear the reserved array and +call the VIDIOC_G_SLICED_VBI_CAP ioctl. The +driver fills in the remaining fields or returns an &EINVAL; if the +sliced VBI API is unsupported or type +is invalid. + + Note the type field was added, +and the ioctl changed from read-only to write-read, in Linux 2.6.19. + + + struct <structname>v4l2_sliced_vbi_cap</structname> + + + + + + + + + + __u16 + service_set + A set of all data services +supported by the driver. Equal to the union of all elements of the +service_lines array. + + + __u16 + service_lines[2][24] + Each element of this array +contains a set of data services the hardware can look for or insert +into a particular scan line. Data services are defined in . Array indices map to ITU-R +line numbers (see also and ) as follows: + + + + + Element + 525 line systems + 625 line systems + + + + + service_lines[0][1] + 1 + 1 + + + + + service_lines[0][23] + 23 + 23 + + + + + service_lines[1][1] + 264 + 314 + + + + + service_lines[1][23] + 286 + 336 + + + + + + + + The number of VBI lines the +hardware can capture or output per frame, or the number of services it +can identify on a given line may be limited. For example on PAL line +16 the hardware may be able to look for a VPS or Teletext signal, but +not both at the same time. Applications can learn about these limits +using the &VIDIOC-S-FMT; ioctl as described in . + + + + + + + + Drivers must set +service_lines[0][0] and +service_lines[1][0] to zero. + + + &v4l2-buf-type; + type + Type of the data stream, see . Should be +V4L2_BUF_TYPE_SLICED_VBI_CAPTURE or +V4L2_BUF_TYPE_SLICED_VBI_OUTPUT. + + + __u32 + reserved[3] + This array is reserved for future +extensions. Applications and drivers must set it to zero. + + + +
+ + + + Sliced VBI services + + + + + + + + + + Symbol + Value + Reference + Lines, usually + Payload + + + + + V4L2_SLICED_TELETEXT_B (Teletext +System B) + 0x0001 + , + PAL/SECAM line 7-22, 320-335 (second field 7-22) + Last 42 of the 45 byte Teletext packet, that is +without clock run-in and framing code, lsb first transmitted. + + + V4L2_SLICED_VPS + 0x0400 + + PAL line 16 + Byte number 3 to 15 according to Figure 9 of +ETS 300 231, lsb first transmitted. + + + V4L2_SLICED_CAPTION_525 + 0x1000 + + NTSC line 21, 284 (second field 21) + Two bytes in transmission order, including parity +bit, lsb first transmitted. + + + V4L2_SLICED_WSS_625 + 0x4000 + , + PAL/SECAM line 23 + +Byte 0 1 + msb lsb msb lsb +Bit 7 6 5 4 3 2 1 0 x x 13 12 11 10 9 + + + + V4L2_SLICED_VBI_525 + 0x1000 + Set of services applicable to 525 +line systems. + + + V4L2_SLICED_VBI_625 + 0x4401 + Set of services applicable to 625 +line systems. + + + +
+ + + + + &return-value; + + + + EINVAL + + The device does not support sliced VBI capturing or +output, or the value in the type field is +wrong. + + + + + + + diff --git a/v4l2-spec/vidioc-g-std.sgml b/v4l2-spec/vidioc-g-std.sgml new file mode 100644 index 000000000..b6f5d267e --- /dev/null +++ b/v4l2-spec/vidioc-g-std.sgml @@ -0,0 +1,99 @@ + + + ioctl VIDIOC_G_STD, VIDIOC_S_STD + &manvol; + + + + VIDIOC_G_STD + VIDIOC_S_STD + Query or select the video standard of the current input + + + + + + int ioctl + int fd + int request + v4l2_std_id +*argp + + + + + int ioctl + int fd + int request + const v4l2_std_id +*argp + + + + + + Arguments + + + + fd + + &fd; + + + + request + + VIDIOC_G_STD, VIDIOC_S_STD + + + + argp + + + + + + + + + Description + + To query and select the current video standard applications +use the VIDIOC_G_STD and VIDIOC_S_STD ioctls which take a pointer to a +&v4l2-std-id; type as argument. VIDIOC_G_STD can +return a single flag or a set of flags as in &v4l2-standard; field +id. The flags must be unambiguous such +that they appear in only one enumerated v4l2_standard structure. + + VIDIOC_S_STD accepts one or more +flags, being a write-only ioctl it does not return the actual new standard as +VIDIOC_G_STD does. When no flags are given or +the current input does not support the requested standard the driver +returns an &EINVAL;. When the standard set is ambiguous drivers may +return EINVAL or choose any of the requested +standards. + + + + &return-value; + + + + EINVAL + + This ioctl is not supported, or the +VIDIOC_S_STD parameter was unsuitable. + + + + + + + diff --git a/v4l2-spec/vidioc-g-tuner.sgml b/v4l2-spec/vidioc-g-tuner.sgml new file mode 100644 index 000000000..6285c18de --- /dev/null +++ b/v4l2-spec/vidioc-g-tuner.sgml @@ -0,0 +1,524 @@ + + + ioctl VIDIOC_G_TUNER, VIDIOC_S_TUNER + &manvol; + + + + VIDIOC_G_TUNER + VIDIOC_S_TUNER + Get or set tuner attributes + + + + + + int ioctl + int fd + int request + struct v4l2_tuner +*argp + + + + + int ioctl + int fd + int request + const struct v4l2_tuner +*argp + + + + + + Arguments + + + + fd + + &fd; + + + + request + + VIDIOC_G_TUNER, VIDIOC_S_TUNER + + + + argp + + + + + + + + + Description + + To query the attributes of a tuner applications initialize the +index field and zero out the +reserved array of a &v4l2-tuner; and call the +VIDIOC_G_TUNER ioctl with a pointer to this +structure. Drivers fill the rest of the structure or return an +&EINVAL; when the index is out of bounds. To enumerate all tuners +applications shall begin at index zero, incrementing by one until the +driver returns EINVAL. + + Tuners have two writable properties, the audio mode and +the radio frequency. To change the audio mode, applications initialize +the index, +audmode and +reserved fields and call the +VIDIOC_S_TUNER ioctl. This will +not change the current tuner, which is determined +by the current video input. Drivers may choose a different audio mode +if the requested mode is invalid or unsupported. Since this is a +write-only ioctl, it does not return the actually +selected audio mode. + + To change the radio frequency the &VIDIOC-S-FREQUENCY; ioctl +is available. + + + struct <structname>v4l2_tuner</structname> + + + + + + + + + __u32 + index + Identifies the tuner, set by the +application. + + + __u8 + name[32] + Name of the tuner, a +NUL-terminated ASCII string. This information is intended for the +user. + + + &v4l2-tuner-type; + type + Type of the tuner, see . + + + __u32 + capability + Tuner capability flags, see +. Audio flags indicate the ability +to decode audio subprograms. They will not +change, for example with the current video standard.When +the structure refers to a radio tuner only the +V4L2_TUNER_CAP_LOW and +V4L2_TUNER_CAP_STEREO flags can be +set. + + + __u32 + rangelow + The lowest tunable frequency in +units of 62.5 kHz, or if the capability +flag V4L2_TUNER_CAP_LOW is set, in units of 62.5 +Hz. + + + __u32 + rangehigh + The highest tunable frequency in +units of 62.5 kHz, or if the capability +flag V4L2_TUNER_CAP_LOW is set, in units of 62.5 +Hz. + + + __u32 + rxsubchans + Some tuners or audio +decoders can determine the received audio subprograms by analyzing +audio carriers, pilot tones or other indicators. To pass this +information drivers set flags defined in in this field. For +example: + + + + + V4L2_TUNER_SUB_MONO + receiving mono audio + + + + + STEREO | SAP + receiving stereo audio and a secondary audio +program + + + + + MONO | STEREO + receiving mono or stereo audio, the hardware cannot +distinguish + + + + + LANG1 | LANG2 + receiving bilingual audio + + + + + MONO | STEREO | LANG1 | LANG2 + receiving mono, stereo or bilingual +audio + + + + + When the +V4L2_TUNER_CAP_STEREO, +_LANG1, _LANG2 or +_SAP flag is cleared in the +capability field, the corresponding +V4L2_TUNER_SUB_ flag must not be set +here.This field is valid only if this is the tuner of the +current video input, or when the structure refers to a radio +tuner. + + + __u32 + audmode + The selected audio mode, see + for valid values. The audio mode does +not affect audio subprogram detection, and like a control it does not automatically change +unless the requested mode is invalid or unsupported. See for possible results when +the selected and received audio programs do not +match.Currently this is the only field of struct +v4l2_tuner applications can +change. + + + __u32 + signal + The signal strength if known, ranging +from 0 to 65535. Higher values indicate a better signal. + + + __s32 + afc + Automatic frequency control: When the +afc value is negative, the frequency is too +low, when positive too high. + + + __u32 + reserved[4] + Reserved for future extensions. Drivers and +applications must set the array to zero. + + + +
+ + + enum v4l2_tuner_type + + &cs-def; + + + V4L2_TUNER_RADIO + 1 + + + + V4L2_TUNER_ANALOG_TV + 2 + + + + +
+ + + Tuner and Modulator Capability Flags + + &cs-def; + + + V4L2_TUNER_CAP_LOW + 0x0001 + When set, tuning frequencies are expressed in units of +62.5 Hz, otherwise in units of 62.5 kHz. + + + V4L2_TUNER_CAP_NORM + 0x0002 + This is a multi-standard tuner; the video standard +can or must be switched. (B/G PAL tuners for example are typically not + considered multi-standard because the video standard is automatically + determined from the frequency band.) The set of supported video + standards is available from the &v4l2-input; pointing to this tuner, + see the description of ioctl &VIDIOC-ENUMINPUT; for details. Only + V4L2_TUNER_ANALOG_TV tuners can have this capability. + + + V4L2_TUNER_CAP_STEREO + 0x0010 + Stereo audio reception is supported. + + + V4L2_TUNER_CAP_LANG1 + 0x0040 + Reception of the primary language of a bilingual +audio program is supported. Bilingual audio is a feature of +two-channel systems, transmitting the primary language monaural on the +main audio carrier and a secondary language monaural on a second +carrier. Only + V4L2_TUNER_ANALOG_TV tuners can have this capability. + + + V4L2_TUNER_CAP_LANG2 + 0x0020 + Reception of the secondary language of a bilingual +audio program is supported. Only + V4L2_TUNER_ANALOG_TV tuners can have this capability. + + + V4L2_TUNER_CAP_SAP + 0x0020 + Reception of a secondary audio program is +supported. This is a feature of the BTSC system which accompanies the +NTSC video standard. Two audio carriers are available for mono or +stereo transmissions of a primary language, and an independent third +carrier for a monaural secondary language. Only + V4L2_TUNER_ANALOG_TV tuners can have this capability.Note the +V4L2_TUNER_CAP_LANG2 and +V4L2_TUNER_CAP_SAP flags are synonyms. +V4L2_TUNER_CAP_SAP applies when the tuner +supports the V4L2_STD_NTSC_M video +standard. + + + +
+ + + Tuner Audio Reception Flags + + &cs-def; + + + V4L2_TUNER_SUB_MONO + 0x0001 + The tuner receives a mono audio signal. + + + V4L2_TUNER_SUB_STEREO + 0x0002 + The tuner receives a stereo audio signal. + + + V4L2_TUNER_SUB_LANG1 + 0x0008 + The tuner receives the primary language of a +bilingual audio signal. Drivers must clear this flag when the current +video standard is V4L2_STD_NTSC_M. + + + V4L2_TUNER_SUB_LANG2 + 0x0004 + The tuner receives the secondary language of a +bilingual audio signal (or a second audio program). + + + V4L2_TUNER_SUB_SAP + 0x0004 + The tuner receives a Second Audio Program. Note the +V4L2_TUNER_SUB_LANG2 and +V4L2_TUNER_SUB_SAP flags are synonyms. The +V4L2_TUNER_SUB_SAP flag applies when the +current video standard is V4L2_STD_NTSC_M. + + + +
+ + + Tuner Audio Modes + + &cs-def; + + + V4L2_TUNER_MODE_MONO + 0 + Play mono audio. When the tuner receives a stereo +signal this a down-mix of the left and right channel. When the tuner +receives a bilingual or SAP signal this mode selects the primary +language. + + + V4L2_TUNER_MODE_STEREO + 1 + Play stereo audio. When the tuner receives +bilingual audio it may play different languages on the left and right +channel or the primary language on both channels. behave as in mono +mode.Playing different languages in this mode is +deprecated. New drivers should do this only in +MODE_LANG1_LANG2.When the tuner +receives no stereo signal or does not support stereo reception the +driver shall fall back to MODE_MONO. + + + V4L2_TUNER_MODE_LANG1 + 3 + Play the primary language, mono or stereo. Only +V4L2_TUNER_ANALOG_TV tuners support this +mode. + + + V4L2_TUNER_MODE_LANG2 + 2 + Play the secondary language, mono. When the tuner +receives no bilingual audio or SAP, or their reception is not +supported the driver shall fall back to mono or stereo mode. Only +V4L2_TUNER_ANALOG_TV tuners support this +mode. + + + V4L2_TUNER_MODE_SAP + 2 + Play the Second Audio Program. When the tuner +receives no bilingual audio or SAP, or their reception is not +supported the driver shall fall back to mono or stereo mode. Only +V4L2_TUNER_ANALOG_TV tuners support this mode. +Note the V4L2_TUNER_MODE_LANG2 and +V4L2_TUNER_MODE_SAP are synonyms. + + + V4L2_TUNER_MODE_LANG1_LANG2 + 4 + Play the primary language on the left channel, the +secondary language on the right channel. When the tuner receives no +bilingual audio or SAP, it shall fall back to +MODE_LANG1 or MODE_MONO. +Only V4L2_TUNER_ANALOG_TV tuners support this +mode. + + + +
+ + + Tuner Audio Matrix + + + + + + + + + + + Selected +V4L2_TUNER_MODE_ + + + Received V4L2_TUNER_SUB_ + MONO + STEREO + LANG1 + LANG2 = SAP + LANG1_LANG2This +mode has been added in Linux 2.6.17 and may not be supported by older +drivers. + + + + + MONO + Mono + Mono/Mono + Mono + Mono + Mono/Mono + + + MONO | SAP + Mono + Mono/Mono + Mono + SAP + Mono/SAP (preferred) or Mono/Mono + + + STEREO + L+R + L/R + Stereo L/R (preferred) or Mono L+R + Stereo L/R (preferred) or Mono L+R + L/R (preferred) or L+R/L+R + + + STEREO | SAP + L+R + L/R + Stereo L/R (preferred) or Mono L+R + SAP + L+R/SAP (preferred) or L/R or L+R/L+R + + + LANG1 | LANG2 + Language 1 + Lang1/Lang2 (deprecatedPlayback of +both languages in MODE_STEREO is deprecated. In +the future drivers should produce only the primary language in this +mode. Applications should request +MODE_LANG1_LANG2 to record both languages or a +stereo signal.) or +Lang1/Lang1 + Language 1 + Language 2 + Lang1/Lang2 (preferred) or Lang1/Lang1 + + + +
+ + + + &return-value; + + + + EINVAL + + The &v4l2-tuner; index is +out of bounds. + + + + + + + diff --git a/v4l2-spec/vidioc-log-status.sgml b/v4l2-spec/vidioc-log-status.sgml new file mode 100644 index 000000000..2634b7c88 --- /dev/null +++ b/v4l2-spec/vidioc-log-status.sgml @@ -0,0 +1,58 @@ + + + ioctl VIDIOC_LOG_STATUS + &manvol; + + + + VIDIOC_LOG_STATUS + Log driver status information + + + + + + int ioctl + int fd + int request + + + + + + Description + + As the video/audio devices become more complicated it +becomes harder to debug problems. When this ioctl is called the driver +will output the current device status to the kernel log. This is +particular useful when dealing with problems like no sound, no video +and incorrectly tuned channels. Also many modern devices autodetect +video and audio standards and this ioctl will report what the device +thinks what the standard is. Mismatches may give an indication where +the problem is. + + This ioctl is optional and not all drivers support it. It +was introduced in Linux 2.6.15. + + + + &return-value; + + + + EINVAL + + The driver does not support this ioctl. + + + + + + + diff --git a/v4l2-spec/vidioc-overlay.sgml b/v4l2-spec/vidioc-overlay.sgml new file mode 100644 index 000000000..d16709fd1 --- /dev/null +++ b/v4l2-spec/vidioc-overlay.sgml @@ -0,0 +1,83 @@ + + + ioctl VIDIOC_OVERLAY + &manvol; + + + + VIDIOC_OVERLAY + Start or stop video overlay + + + + + + int ioctl + int fd + int request + const int *argp + + + + + + Arguments + + + + fd + + &fd; + + + + request + + VIDIOC_OVERLAY + + + + argp + + + + + + + + + Description + + This ioctl is part of the video + overlay I/O method. Applications call + VIDIOC_OVERLAY to start or stop the + overlay. It takes a pointer to an integer which must be set to + zero by the application to stop overlay, to one to start. + + Drivers do not support &VIDIOC-STREAMON; or +&VIDIOC-STREAMOFF; with V4L2_BUF_TYPE_VIDEO_OVERLAY. + + + + &return-value; + + + + EINVAL + + Video overlay is not supported, or the +parameters have not been set up. See for the necessary steps. + + + + + + + diff --git a/v4l2-spec/vidioc-qbuf.sgml b/v4l2-spec/vidioc-qbuf.sgml new file mode 100644 index 000000000..f02debb8c --- /dev/null +++ b/v4l2-spec/vidioc-qbuf.sgml @@ -0,0 +1,168 @@ + + + ioctl VIDIOC_QBUF, VIDIOC_DQBUF + &manvol; + + + + VIDIOC_QBUF + VIDIOC_DQBUF + Exchange a buffer with the driver + + + + + + int ioctl + int fd + int request + struct v4l2_buffer *argp + + + + + + Arguments + + + + fd + + &fd; + + + + request + + VIDIOC_QBUF, VIDIOC_DQBUF + + + + argp + + + + + + + + + Description + + Applications call the VIDIOC_QBUF ioctl +to enqueue an empty (capturing) or filled (output) buffer in the +driver's incoming queue. The semantics depend on the selected I/O +method. + + To enqueue a memory mapped +buffer applications set the type field of a +&v4l2-buffer; to the same buffer type as previously &v4l2-format; +type and &v4l2-requestbuffers; +type, the memory +field to V4L2_MEMORY_MMAP and the +index field. Valid index numbers range from +zero to the number of buffers allocated with &VIDIOC-REQBUFS; +(&v4l2-requestbuffers; count) minus one. The +contents of the struct v4l2_buffer returned +by a &VIDIOC-QUERYBUF; ioctl will do as well. When the buffer is +intended for output (type is +V4L2_BUF_TYPE_VIDEO_OUTPUT or +V4L2_BUF_TYPE_VBI_OUTPUT) applications must also +initialize the bytesused, +field and +timestamp fields. See for details. When +VIDIOC_QBUF is called with a pointer to this +structure the driver sets the +V4L2_BUF_FLAG_MAPPED and +V4L2_BUF_FLAG_QUEUED flags and clears the +V4L2_BUF_FLAG_DONE flag in the +flags field, or it returns an +&EINVAL;. + + To enqueue a user pointer +buffer applications set the type field of a +&v4l2-buffer; to the same buffer type as previously &v4l2-format; +type and &v4l2-requestbuffers; +type, the memory +field to V4L2_MEMORY_USERPTR and the +m.userptr field to the address of the +buffer and length to its size. When the +buffer is intended for output additional fields must be set as above. +When VIDIOC_QBUF is called with a pointer to this +structure the driver sets the V4L2_BUF_FLAG_QUEUED +flag and clears the V4L2_BUF_FLAG_MAPPED and +V4L2_BUF_FLAG_DONE flags in the +flags field, or it returns an error code. +This ioctl locks the memory pages of the buffer in physical memory, +they cannot be swapped out to disk. Buffers remain locked until +dequeued, until the &VIDIOC-STREAMOFF; or &VIDIOC-REQBUFS; ioctl are +called, or until the device is closed. + + Applications call the VIDIOC_DQBUF +ioctl to dequeue a filled (capturing) or displayed (output) buffer +from the driver's outgoing queue. They just set the +type and memory +fields of a &v4l2-buffer; as above, when VIDIOC_DQBUF +is called with a pointer to this structure the driver fills the +remaining fields or returns an error code. + + By default VIDIOC_DQBUF blocks when no +buffer is in the outgoing queue. When the +O_NONBLOCK flag was given to the &func-open; +function, VIDIOC_DQBUF returns immediately +with an &EAGAIN; when no buffer is available. + + The v4l2_buffer structure is +specified in . + + + + &return-value; + + + + EAGAIN + + Non-blocking I/O has been selected using +O_NONBLOCK and no buffer was in the outgoing +queue. + + + + EINVAL + + The buffer type is not +supported, or the index is out of bounds, +or no buffers have been allocated yet, or the +userptr or +length are invalid. + + + + ENOMEM + + Not enough physical or virtual memory was available to +enqueue a user pointer buffer. + + + + EIO + + VIDIOC_DQBUF failed due to an +internal error. Can also indicate temporary problems like signal +loss. Note the driver might dequeue an (empty) buffer despite +returning an error, or even stop capturing. + + + + + + + diff --git a/v4l2-spec/vidioc-querybuf.sgml b/v4l2-spec/vidioc-querybuf.sgml new file mode 100644 index 000000000..e5fb5ac7a --- /dev/null +++ b/v4l2-spec/vidioc-querybuf.sgml @@ -0,0 +1,103 @@ + + + ioctl VIDIOC_QUERYBUF + &manvol; + + + + VIDIOC_QUERYBUF + Query the status of a buffer + + + + + + int ioctl + int fd + int request + struct v4l2_buffer *argp + + + + + + Arguments + + + + fd + + &fd; + + + + request + + VIDIOC_QUERYBUF + + + + argp + + + + + + + + + Description + + This ioctl is part of the memory +mapping I/O method. It can be used to query the status of a +buffer at any time after buffers have been allocated with the +&VIDIOC-REQBUFS; ioctl. + + Applications set the type field + of a &v4l2-buffer; to the same buffer type as previously +&v4l2-format; type and &v4l2-requestbuffers; +type, and the index + field. Valid index numbers range from zero +to the number of buffers allocated with &VIDIOC-REQBUFS; + (&v4l2-requestbuffers; count) minus one. +After calling VIDIOC_QUERYBUF with a pointer to + this structure drivers return an error code or fill the rest of +the structure. + + In the flags field the +V4L2_BUF_FLAG_MAPPED, +V4L2_BUF_FLAG_QUEUED and +V4L2_BUF_FLAG_DONE flags will be valid. The +memory field will be set to +V4L2_MEMORY_MMAP, the m.offset +contains the offset of the buffer from the start of the device memory, +the length field its size. The driver may +or may not set the remaining fields and flags, they are meaningless in +this context. + + The v4l2_buffer structure is + specified in . + + + + &return-value; + + + + EINVAL + + The buffer type is not +supported, or the index is out of bounds. + + + + + + + diff --git a/v4l2-spec/vidioc-querycap.sgml b/v4l2-spec/vidioc-querycap.sgml new file mode 100644 index 000000000..89aa84cf6 --- /dev/null +++ b/v4l2-spec/vidioc-querycap.sgml @@ -0,0 +1,270 @@ + + + ioctl VIDIOC_QUERYCAP + &manvol; + + + + VIDIOC_QUERYCAP + Query device capabilities + + + + + + int ioctl + int fd + int request + struct v4l2_capability *argp + + + + + + Arguments + + + + fd + + &fd; + + + + request + + VIDIOC_QUERYCAP + + + + argp + + + + + + + + + Description + + All V4L2 devices support the +VIDIOC_QUERYCAP ioctl. It is used to identify +kernel devices compatible with this specification and to obtain +information about driver and hardware capabilities. The ioctl takes a +pointer to a &v4l2-capability; which is filled by the driver. When the +driver is not compatible with this specification the ioctl returns an +&EINVAL;. + + + struct <structname>v4l2_capability</structname> + + &cs-str; + + + __u8 + driver[16] + Name of the driver, a unique NUL-terminated +ASCII string. For example: "bttv". Driver specific applications can +use this information to verify the driver identity. It is also useful +to work around known bugs, or to identify drivers in error reports. +The driver version is stored in the version +field.Storing strings in fixed sized arrays is bad +practice but unavoidable here. Drivers and applications should take +precautions to never read or write beyond the end of the array and to +make sure the strings are properly NUL-terminated. + + + __u8 + card[32] + Name of the device, a NUL-terminated ASCII string. +For example: "Yoyodyne TV/FM". One driver may support different brands +or models of video hardware. This information is intended for users, +for example in a menu of available devices. Since multiple TV cards of +the same brand may be installed which are supported by the same +driver, this name should be combined with the character device file +name (⪚ /dev/video2) or the +bus_info string to avoid +ambiguities. + + + __u8 + bus_info[32] + Location of the device in the system, a +NUL-terminated ASCII string. For example: "PCI Slot 4". This +information is intended for users, to distinguish multiple +identical devices. If no such information is available the field may +simply count the devices controlled by the driver, or contain the +empty string (bus_info[0] = 0). + + + __u32 + version + Version number of the driver. Together with +the driver field this identifies a +particular driver. The version number is formatted using the +KERNEL_VERSION() macro: + + + + +#define KERNEL_VERSION(a,b,c) (((a) << 16) + ((b) << 8) + (c)) + +__u32 version = KERNEL_VERSION(0, 8, 1); + +printf ("Version: %u.%u.%u\n", + (version >> 16) & 0xFF, + (version >> 8) & 0xFF, + version & 0xFF); + + + + __u32 + capabilities + Device capabilities, see . + + + __u32 + reserved[4] + Reserved for future extensions. Drivers must set +this array to zero. + + + +
+ + + Device Capabilities Flags + + &cs-def; + + + V4L2_CAP_VIDEO_CAPTURE + 0x00000001 + The device supports the Video Capture interface. + + + V4L2_CAP_VIDEO_OUTPUT + 0x00000002 + The device supports the Video Output interface. + + + V4L2_CAP_VIDEO_OVERLAY + 0x00000004 + The device supports the Video Overlay interface. A video overlay device +typically stores captured images directly in the video memory of a +graphics card, with hardware clipping and scaling. + + + V4L2_CAP_VBI_CAPTURE + 0x00000010 + The device supports the Raw +VBI Capture interface, providing Teletext and Closed Caption +data. + + + V4L2_CAP_VBI_OUTPUT + 0x00000020 + The device supports the Raw VBI Output interface. + + + V4L2_CAP_SLICED_VBI_CAPTURE + 0x00000040 + The device supports the Sliced VBI Capture interface. + + + V4L2_CAP_SLICED_VBI_OUTPUT + 0x00000080 + The device supports the Sliced VBI Output interface. + + + V4L2_CAP_RDS_CAPTURE + 0x00000100 + [to be defined] + + + V4L2_CAP_VIDEO_OUTPUT_OVERLAY + 0x00000200 + The device supports the Video +Output Overlay (OSD) interface. Unlike the Video +Overlay interface, this is a secondary function of video +output devices and overlays an image onto an outgoing video signal. +When the driver sets this flag, it must clear the +V4L2_CAP_VIDEO_OVERLAY flag and vice +versa.The &v4l2-framebuffer; lacks an +&v4l2-buf-type; field, therefore the type of overlay is implied by the +driver capabilities. + + + V4L2_CAP_TUNER + 0x00010000 + The device has some sort of tuner or modulator to +receive or emit RF-modulated video signals. For more information about +tuner and modulator programming see +. + + + V4L2_CAP_AUDIO + 0x00020000 + The device has audio inputs or outputs. It may or +may not support audio recording or playback, in PCM or compressed +formats. PCM audio support must be implemented as ALSA or OSS +interface. For more information on audio inputs and outputs see . + + + V4L2_CAP_RADIO + 0x00040000 + This is a radio receiver. + + + V4L2_CAP_READWRITE + 0x01000000 + The device supports the read() and/or write() +I/O methods. + + + V4L2_CAP_ASYNCIO + 0x02000000 + The device supports the asynchronous I/O methods. + + + V4L2_CAP_STREAMING + 0x04000000 + The device supports the streaming I/O method. + + + +
+ + + + &return-value; + + + + EINVAL + + The device is not compatible with this +specification. + + + + + + + + diff --git a/v4l2-spec/vidioc-queryctrl.sgml b/v4l2-spec/vidioc-queryctrl.sgml new file mode 100644 index 000000000..20c4147eb --- /dev/null +++ b/v4l2-spec/vidioc-queryctrl.sgml @@ -0,0 +1,391 @@ + + + ioctl VIDIOC_QUERYCTRL, VIDIOC_QUERYMENU + &manvol; + + + + VIDIOC_QUERYCTRL + VIDIOC_QUERYMENU + Enumerate controls and menu control items + + + + + + int ioctl + int fd + int request + struct v4l2_queryctrl *argp + + + + + int ioctl + int fd + int request + struct v4l2_querymenu *argp + + + + + + Arguments + + + + fd + + &fd; + + + + request + + VIDIOC_QUERYCTRL, VIDIOC_QUERYMENU + + + + argp + + + + + + + + + Description + + To query the attributes of a control applications set the +id field of a &v4l2-queryctrl; and call the +VIDIOC_QUERYCTRL ioctl with a pointer to this +structure. The driver fills the rest of the structure or returns an +&EINVAL; when the id is invalid. + + It is possible to enumerate controls by calling +VIDIOC_QUERYCTRL with successive +id values starting from +V4L2_CID_BASE up to and exclusive +V4L2_CID_BASE_LASTP1. Drivers may return +EINVAL if a control in this range is not +supported. Further applications can enumerate private controls, which +are not defined in this specification, by starting at +V4L2_CID_PRIVATE_BASE and incrementing +id until the driver returns +EINVAL. + + In both cases, when the driver sets the +V4L2_CTRL_FLAG_DISABLED flag in the +flags field this control is permanently +disabled and should be ignored by the application. + V4L2_CTRL_FLAG_DISABLED was +intended for two purposes: Drivers can skip predefined controls not +supported by the hardware (although returning EINVAL would do as +well), or disable predefined and private controls after hardware +detection without the trouble of reordering control arrays and indices +(EINVAL cannot be used to skip private controls because it would +prematurely end the enumeration). + + When the application ORs id with +V4L2_CTRL_FLAG_NEXT_CTRL the driver returns the +next supported control, or EINVAL if there is +none. Drivers which do not support this flag yet always return +EINVAL. + + Additional information is required for menu controls, the +name of menu items. To query them applications set the +id and index +fields of &v4l2-querymenu; and call the +VIDIOC_QUERYMENU ioctl with a pointer to this +structure. The driver fills the rest of the structure or returns an +&EINVAL; when the id or +index is invalid. Menu items are enumerated +by calling VIDIOC_QUERYMENU with successive +index values from &v4l2-queryctrl; +minimum (0) to +maximum, inclusive. + + See also the examples in . + + + struct <structname>v4l2_queryctrl</structname> + + &cs-str; + + + __u32 + id + Identifies the control, set by the application. See + for predefined IDs. When the ID is ORed +with V4L2_CTRL_FLAG_NEXT_CTRL the driver clears the flag and returns +the first control with a higher ID. Drivers which do not support this +flag yet always return an &EINVAL;. + + + &v4l2-ctrl-type; + type + Type of control, see . + + + __u8 + name[32] + Name of the control, a NUL-terminated ASCII +string. This information is intended for the user. + + + __s32 + minimum + Minimum value, inclusive. This field gives a lower +bound for V4L2_CTRL_TYPE_INTEGER controls. It may +not be valid for any other type of control, including +V4L2_CTRL_TYPE_INTEGER64 controls. Note this is a +signed value. + + + __s32 + maximum + Maximum value, inclusive. This field gives an upper +bound for V4L2_CTRL_TYPE_INTEGER controls and the +highest valid index for V4L2_CTRL_TYPE_MENU +controls. It may not be valid for any other type of control, including +V4L2_CTRL_TYPE_INTEGER64 controls. Note this is a +signed value. + + + __s32 + step + This field gives a step size for +V4L2_CTRL_TYPE_INTEGER controls. It may not be +valid for any other type of control, including +V4L2_CTRL_TYPE_INTEGER64 +controls.Generally drivers should not scale hardware +control values. It may be necessary for example when the +name or id imply +a particular unit and the hardware actually accepts only multiples of +said unit. If so, drivers must take care values are properly rounded +when scaling, such that errors will not accumulate on repeated +read-write cycles.This field gives the smallest change of +an integer control actually affecting hardware. Often the information +is needed when the user can change controls by keyboard or GUI +buttons, rather than a slider. When for example a hardware register +accepts values 0-511 and the driver reports 0-65535, step should be +128.Note although signed, the step value is supposed to +be always positive. + + + __s32 + default_value + The default value of a +V4L2_CTRL_TYPE_INTEGER, +_BOOLEAN or _MENU control. +Not valid for other types of controls. Drivers reset controls only +when the driver is loaded, not later, in particular not when the +func-open; is called. + + + __u32 + flags + Control flags, see . + + + __u32 + reserved[2] + Reserved for future extensions. Drivers must set +the array to zero. + + + +
+ + + struct <structname>v4l2_querymenu</structname> + + &cs-str; + + + __u32 + id + Identifies the control, set by the application +from the respective &v4l2-queryctrl; +id. + + + __u32 + index + Index of the menu item, starting at zero, set by + the application. + + + __u8 + name[32] + Name of the menu item, a NUL-terminated ASCII +string. This information is intended for the user. + + + __u32 + reserved + Reserved for future extensions. Drivers must set +the array to zero. + + + +
+ + + enum v4l2_ctrl_type + + + + + + + + + Type + minimum + step + maximum + Description + + + + + V4L2_CTRL_TYPE_INTEGER + any + any + any + An integer-valued control ranging from minimum to +maximum inclusive. The step value indicates the increment between +values which are actually different on the hardware. + + + V4L2_CTRL_TYPE_BOOLEAN + 0 + 1 + 1 + A boolean-valued control. Zero corresponds to +"disabled", and one means "enabled". + + + V4L2_CTRL_TYPE_MENU + 0 + 1 + N-1 + The control has a menu of N choices. The names of +the menu items can be enumerated with the +VIDIOC_QUERYMENU ioctl. + + + V4L2_CTRL_TYPE_BUTTON + 0 + 0 + 0 + A control which performs an action when set. +Drivers must ignore the value passed with +VIDIOC_S_CTRL and return an &EINVAL; on a +VIDIOC_G_CTRL attempt. + + + V4L2_CTRL_TYPE_INTEGER64 + n/a + n/a + n/a + A 64-bit integer valued control. Minimum, maximum +and step size cannot be queried. + + + V4L2_CTRL_TYPE_CTRL_CLASS + n/a + n/a + n/a + This is not a control. When +VIDIOC_QUERYCTRL is called with a control ID +equal to a control class code (see ), the +ioctl returns the name of the control class and this control type. +Older drivers which do not support this feature return an +&EINVAL;. + + + +
+ + + Control Flags + + &cs-def; + + + V4L2_CTRL_FLAG_DISABLED + 0x0001 + This control is permanently disabled and should be +ignored by the application. Any attempt to change the control will +result in an &EINVAL;. + + + V4L2_CTRL_FLAG_GRABBED + 0x0002 + This control is temporarily unchangeable, for +example because another application took over control of the +respective resource. Such controls may be displayed specially in a +user interface. Attempts to change the control may result in an +&EBUSY;. + + + V4L2_CTRL_FLAG_READ_ONLY + 0x0004 + This control is permanently readable only. Any +attempt to change the control will result in an &EINVAL;. + + + V4L2_CTRL_FLAG_UPDATE + 0x0008 + A hint that changing this control may affect the +value of other controls within the same control class. Applications +should update their user interface accordingly. + + + V4L2_CTRL_FLAG_INACTIVE + 0x0010 + This control is not applicable to the current +configuration and should be displayed accordingly in a user interface. +For example the flag may be set on a MPEG audio level 2 bitrate +control when MPEG audio encoding level 1 was selected with another +control. + + + V4L2_CTRL_FLAG_SLIDER + 0x0020 + A hint that this control is best represented as a +slider-like element in a user interface. + + + +
+ + + + &return-value; + + + + EINVAL + + The &v4l2-queryctrl; id +is invalid. The &v4l2-querymenu; id or +index is invalid. + + + + + + + diff --git a/v4l2-spec/vidioc-querystd.sgml b/v4l2-spec/vidioc-querystd.sgml new file mode 100644 index 000000000..b5a7ff934 --- /dev/null +++ b/v4l2-spec/vidioc-querystd.sgml @@ -0,0 +1,83 @@ + + + ioctl VIDIOC_QUERYSTD + &manvol; + + + + VIDIOC_QUERYSTD + Sense the video standard received by the current +input + + + + + + int ioctl + int fd + int request + v4l2_std_id *argp + + + + + + Arguments + + + + fd + + &fd; + + + + request + + VIDIOC_QUERYSTD + + + + argp + + + + + + + + + Description + + The hardware may be able to detect the current video +standard automatically. To do so, applications call +VIDIOC_QUERYSTD with a pointer to a &v4l2-std-id; type. The +driver stores here a set of candidates, this can be a single flag or a +set of supported standards if for example the hardware can only +distinguish between 50 and 60 Hz systems. When detection is not +possible or fails, the set must contain all standards supported by the +current video input or output. + + + + + &return-value; + + + + EINVAL + + This ioctl is not supported. + + + + + + + diff --git a/v4l2-spec/vidioc-reqbufs.sgml b/v4l2-spec/vidioc-reqbufs.sgml new file mode 100644 index 000000000..fe3f63019 --- /dev/null +++ b/v4l2-spec/vidioc-reqbufs.sgml @@ -0,0 +1,160 @@ + + + ioctl VIDIOC_REQBUFS + &manvol; + + + + VIDIOC_REQBUFS + Initiate Memory Mapping or User Pointer I/O + + + + + + int ioctl + int fd + int request + struct v4l2_requestbuffers *argp + + + + + + Arguments + + + + fd + + &fd; + + + + request + + VIDIOC_REQBUFS + + + + argp + + + + + + + + + Description + + This ioctl is used to initiate memory +mapped or user pointer +I/O. Memory mapped buffers are located in device memory and must be +allocated with this ioctl before they can be mapped into the +application's address space. User buffers are allocated by +applications themselves, and this ioctl is merely used to switch the +driver into user pointer I/O mode. + + To allocate device buffers applications initialize three +fields of a v4l2_requestbuffers structure. +They set the type field to the respective +stream or buffer type, the count field to +the desired number of buffers, and memory +must be set to V4L2_MEMORY_MMAP. When the ioctl +is called with a pointer to this structure the driver attempts to +allocate the requested number of buffers and stores the actual number +allocated in the count field. It can be +smaller than the number requested, even zero, when the driver runs out +of free memory. A larger number is possible when the driver requires +more buffers to function correctly. + For example video output requires at least two buffers, +one displayed and one filled by the application. + When memory mapping I/O is not supported the ioctl +returns an &EINVAL;. + + Applications can call VIDIOC_REQBUFS +again to change the number of buffers, however this cannot succeed +when any buffers are still mapped. A count +value of zero frees all buffers, after aborting or finishing any DMA +in progress, an implicit &VIDIOC-STREAMOFF;. + + To negotiate user pointer I/O, applications initialize only +the type field and set +memory to +V4L2_MEMORY_USERPTR. When the ioctl is called +with a pointer to this structure the driver prepares for user pointer +I/O, when this I/O method is not supported the ioctl returns an +&EINVAL;. + + + struct <structname>v4l2_requestbuffers</structname> + + &cs-str; + + + __u32 + count + The number of buffers requested or granted. This +field is only used when memory is set to +V4L2_MEMORY_MMAP. + + + &v4l2-buf-type; + type + Type of the stream or buffers, this is the same +as the &v4l2-format; type field. See for valid values. + + + &v4l2-memory; + memory + Applications set this field to +V4L2_MEMORY_MMAP or +V4L2_MEMORY_USERPTR. + + + __u32 + reserved[2] + A place holder for future extensions and custom +(driver defined) buffer types V4L2_BUF_TYPE_PRIVATE and +higher. + + + +
+ + + + &return-value; + + + + EBUSY + + The driver supports multiple opens and I/O is already +in progress, or reallocation of buffers was attempted although one or +more are still mapped. + + + + EINVAL + + The buffer type (type field) or the +requested I/O method (memory) is not +supported. + + + + + + + diff --git a/v4l2-spec/vidioc-streamon.sgml b/v4l2-spec/vidioc-streamon.sgml new file mode 100644 index 000000000..e42bff1f2 --- /dev/null +++ b/v4l2-spec/vidioc-streamon.sgml @@ -0,0 +1,106 @@ + + + ioctl VIDIOC_STREAMON, VIDIOC_STREAMOFF + &manvol; + + + + VIDIOC_STREAMON + VIDIOC_STREAMOFF + Start or stop streaming I/O + + + + + + int ioctl + int fd + int request + const int *argp + + + + + + Arguments + + + + fd + + &fd; + + + + request + + VIDIOC_STREAMON, VIDIOC_STREAMOFF + + + + argp + + + + + + + + + Description + + The VIDIOC_STREAMON and +VIDIOC_STREAMOFF ioctl start and stop the capture +or output process during streaming (memory +mapping or user pointer) I/O. + + Specifically the capture hardware is disabled and no input +buffers are filled (if there are any empty buffers in the incoming +queue) until VIDIOC_STREAMON has been called. +Accordingly the output hardware is disabled, no video signal is +produced until VIDIOC_STREAMON has been called. +The ioctl will succeed only when at least one output buffer is in the +incoming queue. + + The VIDIOC_STREAMOFF ioctl, apart of +aborting or finishing any DMA in progress, unlocks any user pointer +buffers locked in physical memory, and it removes all buffers from the +incoming and outgoing queues. That means all images captured but not +dequeued yet will be lost, likewise all images enqueued for output but +not transmitted yet. I/O returns to the same state as after calling +&VIDIOC-REQBUFS; and can be restarted accordingly. + + Both ioctls take a pointer to an integer, the desired buffer or +stream type. This is the same as &v4l2-requestbuffers; +type. + + Note applications can be preempted for unknown periods right +before or after the VIDIOC_STREAMON or +VIDIOC_STREAMOFF calls, there is no notion of +starting or stopping "now". Buffer timestamps can be used to +synchronize with other events. + + + + &return-value; + + + + EINVAL + + Streaming I/O is not supported, the buffer +type is not supported, or no buffers have +been allocated (memory mapping) or enqueued (output) yet. + + + + + + + -- cgit v1.2.3