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diff --git a/linux/Documentation/DocBook/v4l/compat.xml b/linux/Documentation/DocBook/v4l/compat.xml new file mode 100644 index 000000000..4d1902a54 --- /dev/null +++ b/linux/Documentation/DocBook/v4l/compat.xml @@ -0,0 +1,2457 @@ + <title>Changes</title> + + <para>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.</para> + + <section id="diff-v4l"> + <title>Differences between V4L and V4L2</title> + + <para>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 <filename>videodev</filename> kernel module translating ioctls on +the fly. For a transition period not all drivers will support the V4L2 +API.</para> + + <section> + <title>Opening and Closing Devices</title> + + <para>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 <xref linkend="devices" /> and below in <xref + linkend="v4l-dev" />.</para> + + <para>The V4L <filename>videodev</filename> 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.</para> + + <table id="v4l-dev"> + <title>V4L Device Types, Names and Numbers</title> + <tgroup cols="3"> + <thead> + <row> + <entry>Device Type</entry> + <entry>File Name</entry> + <entry>Minor Numbers</entry> + </row> + </thead> + <tbody valign="top"> + <row> + <entry>Video capture and overlay</entry> + <entry><para><filename>/dev/video</filename> and +<filename>/dev/bttv0</filename><footnote> <para>According to +Documentation/devices.txt these should be symbolic links to +<filename>/dev/video0</filename>. Note the original bttv interface is +not compatible with V4L or V4L2.</para> </footnote>, +<filename>/dev/video0</filename> to +<filename>/dev/video63</filename></para></entry> + <entry>0-63</entry> + </row> + <row> + <entry>Radio receiver</entry> + <entry><para><filename>/dev/radio</filename><footnote> + <para>According to +<filename>Documentation/devices.txt</filename> a symbolic link to +<filename>/dev/radio0</filename>.</para> + </footnote>, <filename>/dev/radio0</filename> to +<filename>/dev/radio63</filename></para></entry> + <entry>64-127</entry> + </row> + <row> + <entry>Teletext decoder</entry> + <entry><para><filename>/dev/vtx</filename>, +<filename>/dev/vtx0</filename> to +<filename>/dev/vtx31</filename></para></entry> + <entry>192-223</entry> + </row> + <row> + <entry>Raw VBI capture</entry> + <entry><para><filename>/dev/vbi</filename>, +<filename>/dev/vbi0</filename> to +<filename>/dev/vbi31</filename></para></entry> + <entry>224-255</entry> + </row> + </tbody> + </tgroup> + </table> + + <para>V4L prohibits (or used to prohibit) multiple opens of a +device file. V4L2 drivers <emphasis>may</emphasis> support multiple +opens, see <xref linkend="open" /> for details and consequences.</para> + + <para>V4L drivers respond to V4L2 ioctls with an &EINVAL;. The +compatibility layer in the V4L2 <filename>videodev</filename> 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 <xref + linkend="driver" />.</para> + </section> + + <section> + <title>Querying Capabilities</title> + + <para>The V4L <constant>VIDIOCGCAP</constant> ioctl is +equivalent to V4L2's &VIDIOC-QUERYCAP;.</para> + + <para>The <structfield>name</structfield> field in struct +<structname>video_capability</structname> became +<structfield>card</structfield> in &v4l2-capability;, +<structfield>type</structfield> was replaced by +<structfield>capabilities</structfield>. 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 <xref linkend="open" /> for an +introduction.<informaltable> + <tgroup cols="3"> + <thead> + <row> + <entry>struct +<structname>video_capability</structname> +<structfield>type</structfield></entry> + <entry>&v4l2-capability; +<structfield>capabilities</structfield> flags</entry> + <entry>Purpose</entry> + </row> + </thead> + <tbody valign="top"> + <row> + <entry><constant>VID_TYPE_CAPTURE</constant></entry> + <entry><constant>V4L2_CAP_VIDEO_CAPTURE</constant></entry> + <entry>The <link linkend="capture">video +capture</link> interface is supported.</entry> + </row> + <row> + <entry><constant>VID_TYPE_TUNER</constant></entry> + <entry><constant>V4L2_CAP_TUNER</constant></entry> + <entry>The device has a <link linkend="tuner">tuner or +modulator</link>.</entry> + </row> + <row> + <entry><constant>VID_TYPE_TELETEXT</constant></entry> + <entry><constant>V4L2_CAP_VBI_CAPTURE</constant></entry> + <entry>The <link linkend="raw-vbi">raw VBI +capture</link> interface is supported.</entry> + </row> + <row> + <entry><constant>VID_TYPE_OVERLAY</constant></entry> + <entry><constant>V4L2_CAP_VIDEO_OVERLAY</constant></entry> + <entry>The <link linkend="overlay">video +overlay</link> interface is supported.</entry> + </row> + <row> + <entry><constant>VID_TYPE_CHROMAKEY</constant></entry> + <entry><constant>V4L2_FBUF_CAP_CHROMAKEY</constant> in +field <structfield>capability</structfield> of +&v4l2-framebuffer;</entry> + <entry>Whether chromakey overlay is supported. For +more information on overlay see +<xref linkend="overlay" />.</entry> + </row> + <row> + <entry><constant>VID_TYPE_CLIPPING</constant></entry> + <entry><constant>V4L2_FBUF_CAP_LIST_CLIPPING</constant> +and <constant>V4L2_FBUF_CAP_BITMAP_CLIPPING</constant> in field +<structfield>capability</structfield> of &v4l2-framebuffer;</entry> + <entry>Whether clipping the overlaid image is +supported, see <xref linkend="overlay" />.</entry> + </row> + <row> + <entry><constant>VID_TYPE_FRAMERAM</constant></entry> + <entry><constant>V4L2_FBUF_CAP_EXTERNOVERLAY</constant> +<emphasis>not set</emphasis> in field +<structfield>capability</structfield> of &v4l2-framebuffer;</entry> + <entry>Whether overlay overwrites frame buffer memory, +see <xref linkend="overlay" />.</entry> + </row> + <row> + <entry><constant>VID_TYPE_SCALES</constant></entry> + <entry><constant>-</constant></entry> + <entry>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 <xref + linkend="crop" />.</entry> + </row> + <row> + <entry><constant>VID_TYPE_MONOCHROME</constant></entry> + <entry><constant>-</constant></entry> + <entry>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 <xref linkend="pixfmt" />.</entry> + </row> + <row> + <entry><constant>VID_TYPE_SUBCAPTURE</constant></entry> + <entry><constant>-</constant></entry> + <entry>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 <xref + linkend="crop" />.</entry> + </row> + <row> + <entry><constant>VID_TYPE_MPEG_DECODER</constant></entry> + <entry><constant>-</constant></entry> + <entry>Applications can enumerate the supported image +formats with the &VIDIOC-ENUM-FMT; ioctl to determine if the device +supports MPEG streams.</entry> + </row> + <row> + <entry><constant>VID_TYPE_MPEG_ENCODER</constant></entry> + <entry><constant>-</constant></entry> + <entry>See above.</entry> + </row> + <row> + <entry><constant>VID_TYPE_MJPEG_DECODER</constant></entry> + <entry><constant>-</constant></entry> + <entry>See above.</entry> + </row> + <row> + <entry><constant>VID_TYPE_MJPEG_ENCODER</constant></entry> + <entry><constant>-</constant></entry> + <entry>See above.</entry> + </row> + </tbody> + </tgroup> + </informaltable></para> + + <para>The <structfield>audios</structfield> field was replaced +by <structfield>capabilities</structfield> flag +<constant>V4L2_CAP_AUDIO</constant>, indicating +<emphasis>if</emphasis> 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 <xref + linkend="audio" />.</para> + + <para>The <structfield>maxwidth</structfield>, +<structfield>maxheight</structfield>, +<structfield>minwidth</structfield> and +<structfield>minheight</structfield> 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.</para> + </section> + + <section> + <title>Video Sources</title> + + <para>V4L provides the <constant>VIDIOCGCHAN</constant> and +<constant>VIDIOCSCHAN</constant> ioctl using struct +<structname>video_channel</structname> 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 <xref linkend="video" />.</para> + + <para>The <structfield>channel</structfield> field counting +inputs was renamed to <structfield>index</structfield>, the video +input types were renamed as follows: <informaltable> + <tgroup cols="2"> + <thead> + <row> + <entry>struct <structname>video_channel</structname> +<structfield>type</structfield></entry> + <entry>&v4l2-input; +<structfield>type</structfield></entry> + </row> + </thead> + <tbody valign="top"> + <row> + <entry><constant>VIDEO_TYPE_TV</constant></entry> + <entry><constant>V4L2_INPUT_TYPE_TUNER</constant></entry> + </row> + <row> + <entry><constant>VIDEO_TYPE_CAMERA</constant></entry> + <entry><constant>V4L2_INPUT_TYPE_CAMERA</constant></entry> + </row> + </tbody> + </tgroup> + </informaltable></para> + + <para>Unlike the <structfield>tuners</structfield> 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 <structfield>tuner</structfield> of +&v4l2-input;. Enumeration of tuners is discussed in <xref + linkend="tuner" />.</para> + + <para>The redundant <constant>VIDEO_VC_TUNER</constant> flag was +dropped. Video inputs associated with a tuner are of type +<constant>V4L2_INPUT_TYPE_TUNER</constant>. The +<constant>VIDEO_VC_AUDIO</constant> flag was replaced by the +<structfield>audioset</structfield> field. V4L2 considers devices with +up to 32 audio inputs. Each set bit in the +<structfield>audioset</structfield> field represents one audio input +this video input combines with. For information about audio inputs and +how to switch between them see <xref linkend="audio" />.</para> + + <para>The <structfield>norm</structfield> field describing the +supported video standards was replaced by +<structfield>std</structfield>. The V4L specification mentions a flag +<constant>VIDEO_VC_NORM</constant> indicating whether the standard can +be changed. This flag was a later addition together with the +<structfield>norm</structfield> field and has been removed in the +meantime. V4L2 has a similar, albeit more comprehensive approach +to video standards, see <xref linkend="standard" /> for more +information.</para> + </section> + + <section> + <title>Tuning</title> + + <para>The V4L <constant>VIDIOCGTUNER</constant> and +<constant>VIDIOCSTUNER</constant> ioctl and struct +<structname>video_tuner</structname> 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 <xref linkend="tuner" />.</para> + + <para>The <structfield>tuner</structfield> field counting tuners +was renamed to <structfield>index</structfield>. The fields +<structfield>name</structfield>, <structfield>rangelow</structfield> +and <structfield>rangehigh</structfield> remained unchanged.</para> + + <para>The <constant>VIDEO_TUNER_PAL</constant>, +<constant>VIDEO_TUNER_NTSC</constant> and +<constant>VIDEO_TUNER_SECAM</constant> flags indicating the supported +video standards were dropped. This information is now contained in the +associated &v4l2-input;. No replacement exists for the +<constant>VIDEO_TUNER_NORM</constant> flag indicating whether the +video standard can be switched. The <structfield>mode</structfield> +field to select a different video standard was replaced by a whole new +set of ioctls and structures described in <xref linkend="standard" />. +Due to its ubiquity it should be mentioned the BTTV driver supports +several standards in addition to the regular +<constant>VIDEO_MODE_PAL</constant> (0), +<constant>VIDEO_MODE_NTSC</constant>, +<constant>VIDEO_MODE_SECAM</constant> and +<constant>VIDEO_MODE_AUTO</constant> (3). Namely N/PAL Argentina, +M/PAL, N/PAL, and NTSC Japan with numbers 3-6 (sic).</para> + + <para>The <constant>VIDEO_TUNER_STEREO_ON</constant> flag +indicating stereo reception became +<constant>V4L2_TUNER_SUB_STEREO</constant> in field +<structfield>rxsubchans</structfield>. 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 +<constant>VIDEO_TUNER_RDS_ON</constant> and +<constant>VIDEO_TUNER_MBS_ON</constant> flags.</para> + + <para> The <constant>VIDEO_TUNER_LOW</constant> flag was renamed +to <constant>V4L2_TUNER_CAP_LOW</constant> in the &v4l2-tuner; +<structfield>capability</structfield> field.</para> + + <para>The <constant>VIDIOCGFREQ</constant> and +<constant>VIDIOCSFREQ</constant> 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.</para> + </section> + + <section id="v4l-image-properties"> + <title>Image Properties</title> + + <para>V4L2 has no equivalent of the +<constant>VIDIOCGPICT</constant> and <constant>VIDIOCSPICT</constant> +ioctl and struct <structname>video_picture</structname>. The following +fields where replaced by V4L2 controls accessible with the +&VIDIOC-QUERYCTRL;, &VIDIOC-G-CTRL; and &VIDIOC-S-CTRL; ioctls:<informaltable> + <tgroup cols="2"> + <thead> + <row> + <entry>struct <structname>video_picture</structname></entry> + <entry>V4L2 Control ID</entry> + </row> + </thead> + <tbody valign="top"> + <row> + <entry><structfield>brightness</structfield></entry> + <entry><constant>V4L2_CID_BRIGHTNESS</constant></entry> + </row> + <row> + <entry><structfield>hue</structfield></entry> + <entry><constant>V4L2_CID_HUE</constant></entry> + </row> + <row> + <entry><structfield>colour</structfield></entry> + <entry><constant>V4L2_CID_SATURATION</constant></entry> + </row> + <row> + <entry><structfield>contrast</structfield></entry> + <entry><constant>V4L2_CID_CONTRAST</constant></entry> + </row> + <row> + <entry><structfield>whiteness</structfield></entry> + <entry><constant>V4L2_CID_WHITENESS</constant></entry> + </row> + </tbody> + </tgroup> + </informaltable></para> + + <para>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 <xref +linkend="control" />.</para> + + <para>The <structfield>depth</structfield> (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 <structfield>palette</structfield> field +moved into the &v4l2-pix-format;:<informaltable> + <tgroup cols="2"> + <thead> + <row> + <entry>struct <structname>video_picture</structname> +<structfield>palette</structfield></entry> + <entry>&v4l2-pix-format; +<structfield>pixfmt</structfield></entry> + </row> + </thead> + <tbody valign="top"> + <row> + <entry><constant>VIDEO_PALETTE_GREY</constant></entry> + <entry><para><link +linkend="V4L2-PIX-FMT-GREY"><constant>V4L2_PIX_FMT_GREY</constant></link></para></entry> + </row> + <row> + <entry><constant>VIDEO_PALETTE_HI240</constant></entry> + <entry><para><link +linkend="pixfmt-reserved"><constant>V4L2_PIX_FMT_HI240</constant></link><footnote> + <para>This is a custom format used by the BTTV +driver, not one of the V4L2 standard formats.</para> + </footnote></para></entry> + </row> + <row> + <entry><constant>VIDEO_PALETTE_RGB565</constant></entry> + <entry><para><link +linkend="pixfmt-rgb"><constant>V4L2_PIX_FMT_RGB565</constant></link></para></entry> + </row> + <row> + <entry><constant>VIDEO_PALETTE_RGB555</constant></entry> + <entry><para><link +linkend="pixfmt-rgb"><constant>V4L2_PIX_FMT_RGB555</constant></link></para></entry> + </row> + <row> + <entry><constant>VIDEO_PALETTE_RGB24</constant></entry> + <entry><para><link +linkend="pixfmt-rgb"><constant>V4L2_PIX_FMT_BGR24</constant></link></para></entry> + </row> + <row> + <entry><constant>VIDEO_PALETTE_RGB32</constant></entry> + <entry><para><link +linkend="pixfmt-rgb"><constant>V4L2_PIX_FMT_BGR32</constant></link><footnote> + <para>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 <xref linkend="pixfmt-rgb" />.</para> + </footnote></para></entry> + </row> + <row> + <entry><constant>VIDEO_PALETTE_YUV422</constant></entry> + <entry><para><link +linkend="V4L2-PIX-FMT-YUYV"><constant>V4L2_PIX_FMT_YUYV</constant></link></para></entry> + </row> + <row> + <entry><para><constant>VIDEO_PALETTE_YUYV</constant><footnote> + <para><constant>VIDEO_PALETTE_YUV422</constant> +and <constant>VIDEO_PALETTE_YUYV</constant> are the same formats. Some +V4L drivers respond to one, some to the other.</para> + </footnote></para></entry> + <entry><para><link +linkend="V4L2-PIX-FMT-YUYV"><constant>V4L2_PIX_FMT_YUYV</constant></link></para></entry> + </row> + <row> + <entry><constant>VIDEO_PALETTE_UYVY</constant></entry> + <entry><para><link +linkend="V4L2-PIX-FMT-UYVY"><constant>V4L2_PIX_FMT_UYVY</constant></link></para></entry> + </row> + <row> + <entry><constant>VIDEO_PALETTE_YUV420</constant></entry> + <entry>None</entry> + </row> + <row> + <entry><constant>VIDEO_PALETTE_YUV411</constant></entry> + <entry><para><link +linkend="V4L2-PIX-FMT-Y41P"><constant>V4L2_PIX_FMT_Y41P</constant></link><footnote> + <para>Not to be confused with +<constant>V4L2_PIX_FMT_YUV411P</constant>, which is a planar +format.</para> </footnote></para></entry> + </row> + <row> + <entry><constant>VIDEO_PALETTE_RAW</constant></entry> + <entry><para>None<footnote> <para>V4L explains this +as: "RAW capture (BT848)"</para> </footnote></para></entry> + </row> + <row> + <entry><constant>VIDEO_PALETTE_YUV422P</constant></entry> + <entry><para><link +linkend="V4L2-PIX-FMT-YUV422P"><constant>V4L2_PIX_FMT_YUV422P</constant></link></para></entry> + </row> + <row> + <entry><constant>VIDEO_PALETTE_YUV411P</constant></entry> + <entry><para><link +linkend="V4L2-PIX-FMT-YUV411P"><constant>V4L2_PIX_FMT_YUV411P</constant></link><footnote> + <para>Not to be confused with +<constant>V4L2_PIX_FMT_Y41P</constant>, which is a packed +format.</para> </footnote></para></entry> + </row> + <row> + <entry><constant>VIDEO_PALETTE_YUV420P</constant></entry> + <entry><para><link +linkend="V4L2-PIX-FMT-YVU420"><constant>V4L2_PIX_FMT_YVU420</constant></link></para></entry> + </row> + <row> + <entry><constant>VIDEO_PALETTE_YUV410P</constant></entry> + <entry><para><link +linkend="V4L2-PIX-FMT-YVU410"><constant>V4L2_PIX_FMT_YVU410</constant></link></para></entry> + </row> + </tbody> + </tgroup> + </informaltable></para> + + <para>V4L2 image formats are defined in <xref +linkend="pixfmt" />. The image format can be selected with the +&VIDIOC-S-FMT; ioctl.</para> + </section> + + <section> + <title>Audio</title> + + <para>The <constant>VIDIOCGAUDIO</constant> and +<constant>VIDIOCSAUDIO</constant> ioctl and struct +<structname>video_audio</structname> 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 <xref linkend="audio" />.</para> + + <para>The <structfield>audio</structfield> "channel number" +field counting audio inputs was renamed to +<structfield>index</structfield>.</para> + + <para>On <constant>VIDIOCSAUDIO</constant> the +<structfield>mode</structfield> field selects <emphasis>one</emphasis> +of the <constant>VIDEO_SOUND_MONO</constant>, +<constant>VIDEO_SOUND_STEREO</constant>, +<constant>VIDEO_SOUND_LANG1</constant> or +<constant>VIDEO_SOUND_LANG2</constant> audio demodulation modes. When +the current audio standard is BTSC +<constant>VIDEO_SOUND_LANG2</constant> refers to SAP and +<constant>VIDEO_SOUND_LANG1</constant> is meaningless. Also +undocumented in the V4L specification, there is no way to query the +selected mode. On <constant>VIDIOCGAUDIO</constant> the driver returns +the <emphasis>actually received</emphasis> audio programmes in this +field. In the V4L2 API this information is stored in the &v4l2-tuner; +<structfield>rxsubchans</structfield> and +<structfield>audmode</structfield> fields, respectively. See <xref +linkend="tuner" /> 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.</para> + + <para>The following fields where replaced by V4L2 controls +accessible with the &VIDIOC-QUERYCTRL;, &VIDIOC-G-CTRL; and +&VIDIOC-S-CTRL; ioctls:<informaltable> + <tgroup cols="2"> + <thead> + <row> + <entry>struct +<structname>video_audio</structname></entry> + <entry>V4L2 Control ID</entry> + </row> + </thead> + <tbody valign="top"> + <row> + <entry><structfield>volume</structfield></entry> + <entry><constant>V4L2_CID_AUDIO_VOLUME</constant></entry> + </row> + <row> + <entry><structfield>bass</structfield></entry> + <entry><constant>V4L2_CID_AUDIO_BASS</constant></entry> + </row> + <row> + <entry><structfield>treble</structfield></entry> + <entry><constant>V4L2_CID_AUDIO_TREBLE</constant></entry> + </row> + <row> + <entry><structfield>balance</structfield></entry> + <entry><constant>V4L2_CID_AUDIO_BALANCE</constant></entry> + </row> + </tbody> + </tgroup> + </informaltable></para> + + <para>To determine which of these controls are supported by a +driver V4L provides the <structfield>flags</structfield> +<constant>VIDEO_AUDIO_VOLUME</constant>, +<constant>VIDEO_AUDIO_BASS</constant>, +<constant>VIDEO_AUDIO_TREBLE</constant> and +<constant>VIDEO_AUDIO_BALANCE</constant>. In the V4L2 API the +&VIDIOC-QUERYCTRL; ioctl reports if the respective control is +supported. Accordingly the <constant>VIDEO_AUDIO_MUTABLE</constant> +and <constant>VIDEO_AUDIO_MUTE</constant> flags where replaced by the +boolean <constant>V4L2_CID_AUDIO_MUTE</constant> control.</para> + + <para>All V4L2 controls have a <structfield>step</structfield> +attribute replacing the struct <structname>video_audio</structname> +<structfield>step</structfield> 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 <xref linkend="control" />.</para> + </section> + + <section> + <title>Frame Buffer Overlay</title> + + <para>The V4L2 ioctls equivalent to +<constant>VIDIOCGFBUF</constant> and <constant>VIDIOCSFBUF</constant> +are &VIDIOC-G-FBUF; and &VIDIOC-S-FBUF;. The +<structfield>base</structfield> field of struct +<structname>video_buffer</structname> remained unchanged, except V4L2 +defines a flag to indicate non-destructive overlays instead of a +<constant>NULL</constant> pointer. All other fields moved into the +&v4l2-pix-format; <structfield>fmt</structfield> substructure of +&v4l2-framebuffer;. The <structfield>depth</structfield> field was +replaced by <structfield>pixelformat</structfield>. See <xref + linkend="pixfmt-rgb" /> for a list of RGB formats and their +respective color depths.</para> + + <para>Instead of the special ioctls +<constant>VIDIOCGWIN</constant> and <constant>VIDIOCSWIN</constant> +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 <structfield>win</structfield> +member of the <structfield>fmt</structfield> union is used, a +&v4l2-window;.</para> + + <para>The <structfield>x</structfield>, +<structfield>y</structfield>, <structfield>width</structfield> and +<structfield>height</structfield> fields of struct +<structname>video_window</structname> moved into &v4l2-rect; +substructure <structfield>w</structfield> of struct +<structname>v4l2_window</structname>. The +<structfield>chromakey</structfield>, +<structfield>clips</structfield>, and +<structfield>clipcount</structfield> fields remained unchanged. Struct +<structname>video_clip</structname> was renamed to &v4l2-clip;, also +containing a struct <structname>v4l2_rect</structname>, but the +semantics are still the same.</para> + + <para>The <constant>VIDEO_WINDOW_INTERLACE</constant> flag was +dropped. Instead applications must set the +<structfield>field</structfield> field to +<constant>V4L2_FIELD_ANY</constant> or +<constant>V4L2_FIELD_INTERLACED</constant>. The +<constant>VIDEO_WINDOW_CHROMAKEY</constant> flag moved into +&v4l2-framebuffer;, under the new name +<constant>V4L2_FBUF_FLAG_CHROMAKEY</constant>.</para> + + <para>In V4L, storing a bitmap pointer in +<structfield>clips</structfield> and setting +<structfield>clipcount</structfield> to +<constant>VIDEO_CLIP_BITMAP</constant> (-1) requests bitmap +clipping, using a fixed size bitmap of 1024 × 625 bits. Struct +<structname>v4l2_window</structname> has a separate +<structfield>bitmap</structfield> pointer field for this purpose and +the bitmap size is determined by <structfield>w.width</structfield> and +<structfield>w.height</structfield>.</para> + + <para>The <constant>VIDIOCCAPTURE</constant> ioctl to enable or +disable overlay was renamed to &VIDIOC-OVERLAY;.</para> + </section> + + <section> + <title>Cropping</title> + + <para>To capture only a subsection of the full picture V4L +defines the <constant>VIDIOCGCAPTURE</constant> and +<constant>VIDIOCSCAPTURE</constant> ioctls using struct +<structname>video_capture</structname>. 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 +<xref linkend="crop" /> for details.</para> + + <para>The <structfield>x</structfield>, +<structfield>y</structfield>, <structfield>width</structfield> and +<structfield>height</structfield> fields moved into &v4l2-rect; +substructure <structfield>c</structfield> of struct +<structname>v4l2_crop</structname>. The +<structfield>decimation</structfield> 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.</para> + + <para>The <constant>VIDEO_CAPTURE_ODD</constant> +and <constant>VIDEO_CAPTURE_EVEN</constant> flags to capture only the +odd or even field, respectively, were replaced by +<constant>V4L2_FIELD_TOP</constant> and +<constant>V4L2_FIELD_BOTTOM</constant> in the field named +<structfield>field</structfield> of &v4l2-pix-format; and +&v4l2-window;. These structures are used to select a capture or +overlay format with the &VIDIOC-S-FMT; ioctl.</para> + </section> + + <section> + <title>Reading Images, Memory Mapping</title> + + <section> + <title>Capturing using the read method</title> + + <para>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.</para> + + <para>To select an image format and size, V4L provides the +<constant>VIDIOCSPICT</constant> and <constant>VIDIOCSWIN</constant> +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 +<structfield>pix</structfield> of its <structfield>fmt</structfield> +union is used.</para> + + <para>For more information about the V4L2 read interface see +<xref linkend="rw" />.</para> + </section> + <section> + <title>Capturing using memory mapping</title> + + <para>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.</para> + + <informaltable> + <tgroup cols="2"> + <thead> + <row> + <entry>V4L</entry> + <entry>V4L2</entry> + </row> + </thead> + <tbody valign="top"> + <row> + <entry></entry> + <entry>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.</entry> + </row> + <row> + <entry><para>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.</para></entry> + <entry><para>The &VIDIOC-REQBUFS; ioctl allocates the +desired number of buffers, this is a required step in the initialization +sequence.</para></entry> + </row> + <row> + <entry><para>Drivers map all buffers as one contiguous +range of memory. The <constant>VIDIOCGMBUF</constant> 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.</para></entry> + <entry><para>Buffers are individually mapped. The +offset and size of each buffer can be determined with the +&VIDIOC-QUERYBUF; ioctl.</para></entry> + </row> + <row> + <entry><para>The <constant>VIDIOCMCAPTURE</constant> +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.</para><para>The <constant>VIDIOCSYNC</constant> ioctl +suspends execution until a particular buffer has been +filled.</para></entry> + <entry><para>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.</para></entry> + </row> + </tbody> + </tgroup> + </informaltable> + + <para>For a more in-depth discussion of memory mapping and +examples, see <xref linkend="mmap" />.</para> + </section> + </section> + + <section> + <title>Reading Raw VBI Data</title> + + <para>Originally the V4L API did not specify a raw VBI capture +interface, only the device file <filename>/dev/vbi</filename> 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:<informaltable> + <tgroup cols="2"> + <thead> + <row> + <entry>&v4l2-vbi-format;</entry> + <entry>V4L, BTTV driver</entry> + </row> + </thead> + <tbody valign="top"> + <row> + <entry>sampling_rate</entry> + <entry>28636363 Hz NTSC (or any other 525-line +standard); 35468950 Hz PAL and SECAM (625-line standards)</entry> + </row> + <row> + <entry>offset</entry> + <entry>?</entry> + </row> + <row> + <entry>samples_per_line</entry> + <entry>2048</entry> + </row> + <row> + <entry>sample_format</entry> + <entry>V4L2_PIX_FMT_GREY. The last four bytes (a +machine endianess integer) contain a frame counter.</entry> + </row> + <row> + <entry>start[]</entry> + <entry>10, 273 NTSC; 22, 335 PAL and SECAM</entry> + </row> + <row> + <entry>count[]</entry> + <entry><para>16, 16<footnote><para>Old driver +versions used different values, eventually the custom +<constant>BTTV_VBISIZE</constant> ioctl was added to query the +correct values.</para></footnote></para></entry> + </row> + <row> + <entry>flags</entry> + <entry>0</entry> + </row> + </tbody> + </tgroup> + </informaltable></para> + + <para>Undocumented in the V4L specification, in Linux 2.3 the +<constant>VIDIOCGVBIFMT</constant> and +<constant>VIDIOCSVBIFMT</constant> ioctls using struct +<structname>vbi_format</structname> were added to determine the VBI +image parameters. These ioctls are only partially compatible with the +V4L2 VBI interface specified in <xref linkend="raw-vbi" />.</para> + + <para>An <structfield>offset</structfield> field does not +exist, <structfield>sample_format</structfield> is supposed to be +<constant>VIDEO_PALETTE_RAW</constant>, equivalent to +<constant>V4L2_PIX_FMT_GREY</constant>. The remaining fields are +probably equivalent to &v4l2-vbi-format;.</para> + + <para>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 +<constant>VIDIOCSVBIFMT</constant> always returns an &EINVAL; if the +parameters are invalid.</para> + </section> + + <section> + <title>Miscellaneous</title> + + <para>V4L2 has no equivalent of the +<constant>VIDIOCGUNIT</constant> 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 +<xref linkend="open" />.</para> + + <para>No replacement exists for <constant>VIDIOCKEY</constant>, +and the V4L functions for microcode programming. A new interface for +MPEG compression and playback devices is documented in <xref + linkend="extended-controls" />.</para> + </section> + + </section> + + <section id="hist-v4l2"> + <title>Changes of the V4L2 API</title> + + <para>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.</para> + + <section> + <title>Early Versions</title> + <para>1998-08-20: First version.</para> + + <para>1998-08-27: The &func-select; function was introduced.</para> + + <para>1998-09-10: New video standard interface.</para> + + <para>1998-09-18: The <constant>VIDIOC_NONCAP</constant> ioctl +was replaced by the otherwise meaningless <constant>O_TRUNC</constant> +&func-open; flag, and the aliases <constant>O_NONCAP</constant> and +<constant>O_NOIO</constant> were defined. Applications can set this +flag if they intend to access controls only, as opposed to capture +applications which need exclusive access. The +<constant>VIDEO_STD_XXX</constant> identifiers are now ordinals +instead of flags, and the <function>video_std_construct()</function> +helper function takes id and transmission arguments.</para> + + <para>1998-09-28: Revamped video standard. Made video controls +individually enumerable.</para> + + <para>1998-10-02: The <structfield>id</structfield> field was +removed from struct <structname>video_standard</structname> 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.</para> + + <para>1998-11-08: Many minor changes. Most symbols have been +renamed. Some material changes to &v4l2-capability;.</para> + + <para>1998-11-12: The read/write directon of some ioctls was misdefined.</para> + + <para>1998-11-14: <constant>V4L2_PIX_FMT_RGB24</constant> +changed to <constant>V4L2_PIX_FMT_BGR24</constant>, and +<constant>V4L2_PIX_FMT_RGB32</constant> changed to +<constant>V4L2_PIX_FMT_BGR32</constant>. Audio controls are now +accessible with the &VIDIOC-G-CTRL; and &VIDIOC-S-CTRL; ioctls under +names starting with <constant>V4L2_CID_AUDIO</constant>. The +<constant>V4L2_MAJOR</constant> define was removed from +<filename>videodev.h</filename> since it was only used once in the +<filename>videodev</filename> kernel module. The +<constant>YUV422</constant> and <constant>YUV411</constant> planar +image formats were added.</para> + + <para>1998-11-28: A few ioctl symbols changed. Interfaces for codecs and +video output devices were added.</para> + + <para>1999-01-14: A raw VBI capture interface was added.</para> + + <para>1999-01-19: The <constant>VIDIOC_NEXTBUF</constant> ioctl + was removed.</para> + </section> + + <section> + <title>V4L2 Version 0.16 1999-01-31</title> + <para>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.</para> + </section> + + <!-- Where's 0.17? mhs couldn't find that videodev.h, perhaps Bill + forgot to bump the version number or never released it. --> + + <section> + <title>V4L2 Version 0.18 1999-03-16</title> + <para>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.</para> + </section> + + <section> + <title>V4L2 Version 0.19 1999-06-05</title> + <para>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.</para> + <para>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.</para> + <para>1999-04-04: Added a few more control IDs.</para> + <para>1999-04-07: Added the button control type.</para> + <para>1999-05-02: Fixed a typo in videodev.h, and added the +V4L2_CTRL_FLAG_GRAYED (later V4L2_CTRL_FLAG_GRABBED) flag.</para> + <para>1999-05-20: Definition of VIDIOC_G_CTRL was wrong causing +a malfunction of this ioctl.</para> + <para>1999-06-05: Changed the value of +V4L2_CID_WHITENESS.</para> + </section> + + <section> + <title>V4L2 Version 0.20 (1999-09-10)</title> + + <para>Version 0.20 introduced a number of changes which were +<emphasis>not backward compatible</emphasis> 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.</para> + + <orderedlist> + <listitem> + <para>Some typos in <constant>V4L2_FMT_FLAG</constant> +symbols were fixed. &v4l2-clip; was changed for compatibility with +v4l. (1999-08-30)</para> + </listitem> + + <listitem> + <para><constant>V4L2_TUNER_SUB_LANG1</constant> was added. +(1999-09-05)</para> + </listitem> + + <listitem> + <para>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 +<programlisting> +err = ioctl (fd, VIDIOC_XXX, V4L2_XXX); +</programlisting> becomes <programlisting> +int a = V4L2_XXX; err = ioctl(fd, VIDIOC_XXX, &a); +</programlisting> + </para> + </listitem> + + <listitem> + <para>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.</para> + + <para>This change obsoletes the following ioctls: +<constant>VIDIOC_S_INFMT</constant>, +<constant>VIDIOC_G_INFMT</constant>, +<constant>VIDIOC_S_OUTFMT</constant>, +<constant>VIDIOC_G_OUTFMT</constant>, +<constant>VIDIOC_S_VBIFMT</constant> and +<constant>VIDIOC_G_VBIFMT</constant>. The image format structure +<structname>v4l2_format</structname> was renamed to &v4l2-pix-format;, +while &v4l2-format; is now the envelopping structure for all format +negotiations.</para> + </listitem> + + <listitem> + <para>Similar to the changes above, the +<constant>VIDIOC_G_PARM</constant> and +<constant>VIDIOC_S_PARM</constant> ioctls were merged with +<constant>VIDIOC_G_OUTPARM</constant> and +<constant>VIDIOC_S_OUTPARM</constant>. A +<structfield>type</structfield> field in the new &v4l2-streamparm; +selects the respective union member.</para> + + <para>This change obsoletes the +<constant>VIDIOC_G_OUTPARM</constant> and +<constant>VIDIOC_S_OUTPARM</constant> ioctls.</para> + </listitem> + + <listitem> + <para>Control enumeration was simplified, and two new +control flags were introduced and one dropped. The +<structfield>catname</structfield> field was replaced by a +<structfield>group</structfield> field.</para> + + <para>Drivers can now flag unsupported and temporarily +unavailable controls with <constant>V4L2_CTRL_FLAG_DISABLED</constant> +and <constant>V4L2_CTRL_FLAG_GRABBED</constant> respectively. The +<structfield>group</structfield> name indicates a possibly narrower +classification than the <structfield>category</structfield>. 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.</para> + </listitem> + + <listitem> + <para>The &v4l2-buffer; <structfield>timestamp</structfield> +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.</para> + </listitem> + + <listitem> + <para>A <structfield>sequence</structfield> field was added +to &v4l2-buffer;. The <structfield>sequence</structfield> 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.</para> + </listitem> + </orderedlist> + </section> + + <section> + <title>V4L2 Version 0.20 incremental changes</title> + <!-- Version number didn't change anymore, reason unknown. --> + + <para>1999-12-23: In &v4l2-vbi-format; the +<structfield>reserved1</structfield> field became +<structfield>offset</structfield>. Previously drivers were required to +clear the <structfield>reserved1</structfield> field.</para> + + <para>2000-01-13: The + <constant>V4L2_FMT_FLAG_NOT_INTERLACED</constant> flag was added.</para> + + <para>2000-07-31: The <filename>linux/poll.h</filename> header +is now included by <filename>videodev.h</filename> for compatibility +with the original <filename>videodev.h</filename> file.</para> + + <para>2000-11-20: <constant>V4L2_TYPE_VBI_OUTPUT</constant> and +<constant>V4L2_PIX_FMT_Y41P</constant> were added.</para> + + <para>2000-11-25: <constant>V4L2_TYPE_VBI_INPUT</constant> was +added.</para> + + <para>2000-12-04: A couple typos in symbol names were fixed.</para> + + <para>2001-01-18: To avoid namespace conflicts the +<constant>fourcc</constant> macro defined in the +<filename>videodev.h</filename> header file was renamed to +<constant>v4l2_fourcc</constant>.</para> + + <para>2001-01-25: A possible driver-level compatibility problem +between the <filename>videodev.h</filename> file in Linux 2.4.0 and +the <filename>videodev.h</filename> file included in the +<filename>videodevX</filename> patch was fixed. Users of an earlier +version of <filename>videodevX</filename> on Linux 2.4.0 should +recompile their V4L and V4L2 drivers.</para> + + <para>2001-01-26: A possible kernel-level incompatibility +between the <filename>videodev.h</filename> file in the +<filename>videodevX</filename> patch and the +<filename>videodev.h</filename> file in Linux 2.2.x with devfs patches +applied was fixed.</para> + + <para>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?]</para> + + <para>2001-04-13: Big endian 16-bit RGB formats were added.</para> + + <para>2001-09-17: New YUV formats and the &VIDIOC-G-FREQUENCY; and +&VIDIOC-S-FREQUENCY; ioctls were added. (The old +<constant>VIDIOC_G_FREQ</constant> and +<constant>VIDIOC_S_FREQ</constant> ioctls did not take multiple tuners +into account.)</para> + + <para>2000-09-18: <constant>V4L2_BUF_TYPE_VBI</constant> was +added. This may <emphasis>break compatibility</emphasis> as the +&VIDIOC-G-FMT; and &VIDIOC-S-FMT; ioctls may fail now if the struct +<structname>v4l2_fmt</structname> <structfield>type</structfield> +field does not contain <constant>V4L2_BUF_TYPE_VBI</constant>. In the +documentation of the &v4l2-vbi-format; +<structfield>offset</structfield> field the ambiguous phrase "rising +edge" was changed to "leading edge".</para> + </section> + + <section> + <title>V4L2 Version 0.20 2000-11-23</title> + + <para>A number of changes were made to the raw VBI +interface.</para> + + <orderedlist> + <listitem> + <para>Figures clarifying the line numbering scheme were +added to the V4L2 API specification. The +<structfield>start</structfield>[0] and +<structfield>start</structfield>[1] fields no longer count line +numbers beginning at zero. Rationale: a) The previous definition was +unclear. b) The <structfield>start</structfield>[] 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.</para> + </listitem> + + <listitem> + <para>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 <structfield>count</structfield> values will usually be equal is +misleading and pointless and has been removed. This change +<emphasis>breaks compatibility</emphasis> with earlier versions: +Drivers may return EINVAL, applications may not function +correctly.</para> + </listitem> + + <listitem> + <para>Drivers are again permitted to return negative +(unknown) start values as proposed earlier. Why this feature was +dropped is unclear. This change may <emphasis>break +compatibility</emphasis> with applications depending on the start +values being positive. The use of <constant>EBUSY</constant> and +<constant>EINVAL</constant> error codes with the &VIDIOC-S-FMT; ioctl +was clarified. The &EBUSY; was finally documented, and the +<structfield>reserved2</structfield> field which was previously +mentioned only in the <filename>videodev.h</filename> header +file.</para> + </listitem> + + <listitem> + <para>New buffer types +<constant>V4L2_TYPE_VBI_INPUT</constant> and +<constant>V4L2_TYPE_VBI_OUTPUT</constant> were added. The former is an +alias for the old <constant>V4L2_TYPE_VBI</constant>, the latter was +missing in the <filename>videodev.h</filename> file.</para> + </listitem> + </orderedlist> + </section> + + <section> + <title>V4L2 Version 0.20 2002-07-25</title> + <para>Added sliced VBI interface proposal.</para> + </section> + + <section> + <title>V4L2 in Linux 2.5.46, 2002-10</title> + + <para>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.</para> + + <orderedlist> + <listitem> + <para>As specified in <xref linkend="related" />, drivers +must make related device functions available under all minor device +numbers.</para> + </listitem> + + <listitem> + <para>The &func-open; function requires access mode +<constant>O_RDWR</constant> regardless of the device type. All V4L2 +drivers exchanging data with applications must support the +<constant>O_NONBLOCK</constant> flag. The <constant>O_NOIO</constant> +flag, a V4L2 symbol which aliased the meaningless +<constant>O_TRUNC</constant> 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 +<xref linkend="open" />.</para> + </listitem> + + <listitem> + <para>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.</para> + + <para>There are new fields to identify the driver, a new RDS +device function <constant>V4L2_CAP_RDS_CAPTURE</constant>, the +<constant>V4L2_CAP_AUDIO</constant> flag indicates if the device has +any audio connectors, another I/O capability +<constant>V4L2_CAP_ASYNCIO</constant> can be flagged. In response to +these changes the <structfield>type</structfield> field became a bit +set and was merged into the <structfield>flags</structfield> field. +<constant>V4L2_FLAG_TUNER</constant> was renamed to +<constant>V4L2_CAP_TUNER</constant>, +<constant>V4L2_CAP_VIDEO_OVERLAY</constant> replaced +<constant>V4L2_FLAG_PREVIEW</constant> and +<constant>V4L2_CAP_VBI_CAPTURE</constant> and +<constant>V4L2_CAP_VBI_OUTPUT</constant> replaced +<constant>V4L2_FLAG_DATA_SERVICE</constant>. +<constant>V4L2_FLAG_READ</constant> and +<constant>V4L2_FLAG_WRITE</constant> were merged into +<constant>V4L2_CAP_READWRITE</constant>.</para> + + <para>The redundant fields +<structfield>inputs</structfield>, <structfield>outputs</structfield> +and <structfield>audios</structfield> were removed. These properties +can be determined as described in <xref linkend="video" /> and <xref +linkend="audio" />.</para> + + <para>The somewhat volatile and therefore barely useful +fields <structfield>maxwidth</structfield>, +<structfield>maxheight</structfield>, +<structfield>minwidth</structfield>, +<structfield>minheight</structfield>, +<structfield>maxframerate</structfield> were removed. This information +is available as described in <xref linkend="format" /> and +<xref linkend="standard" />.</para> + + <para><constant>V4L2_FLAG_SELECT</constant> 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 <constant>V4L2_FLAG_MONOCHROME</constant> flag was removed, +this information is available as described in <xref + linkend="format" />.</para> + </listitem> + + <listitem> + <para>In &v4l2-input; the +<structfield>assoc_audio</structfield> field and the +<structfield>capability</structfield> field and its only flag +<constant>V4L2_INPUT_CAP_AUDIO</constant> was replaced by the new +<structfield>audioset</structfield> field. Instead of linking one +video input to one audio input this field reports all audio inputs +this video input combines with.</para> + + <para>New fields are <structfield>tuner</structfield> +(reversing the former link from tuners to video inputs), +<structfield>std</structfield> and +<structfield>status</structfield>.</para> + + <para>Accordingly &v4l2-output; lost its +<structfield>capability</structfield> and +<structfield>assoc_audio</structfield> fields. +<structfield>audioset</structfield>, +<structfield>modulator</structfield> and +<structfield>std</structfield> where added instead.</para> + </listitem> + + <listitem> + <para>The &v4l2-audio; field +<structfield>audio</structfield> was renamed to +<structfield>index</structfield>, for consistency with other +structures. A new capability flag +<constant>V4L2_AUDCAP_STEREO</constant> was added to indicated if the +audio input in question supports stereo sound. +<constant>V4L2_AUDCAP_EFFECTS</constant> and the corresponding +<constant>V4L2_AUDMODE</constant> flags where removed. This can be +easily implemented using controls. (However the same applies to AVL +which is still there.)</para> + + <para>Again for consistency the &v4l2-audioout; field +<structfield>audio</structfield> was renamed to +<structfield>index</structfield>.</para> + </listitem> + + <listitem> + <para>The &v4l2-tuner; +<structfield>input</structfield> field was replaced by an +<structfield>index</structfield> field, permitting devices with +multiple tuners. The link between video inputs and tuners is now +reversed, inputs point to their tuner. The +<structfield>std</structfield> substructure became a +simple set (more about this below) and moved into &v4l2-input;. A +<structfield>type</structfield> field was added.</para> + + <para>Accordingly in &v4l2-modulator; the +<structfield>output</structfield> was replaced by an +<structfield>index</structfield> field.</para> + + <para>In &v4l2-frequency; the +<structfield>port</structfield> field was replaced by a +<structfield>tuner</structfield> field containing the respective tuner +or modulator index number. A tuner <structfield>type</structfield> +field was added and the <structfield>reserved</structfield> field +became larger for future extensions (satellite tuners in +particular).</para> + </listitem> + + <listitem> + <para>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 +<filename>videodev2.h</filename> header file. For details see <xref + linkend="standard" />. 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 +<structfield>index</structfield> field was added for &VIDIOC-ENUMSTD;. +A &v4l2-std-id; field named <structfield>id</structfield> was added as +machine readable identifier, also replacing the +<structfield>transmission</structfield> field. The misleading +<structfield>framerate</structfield> field was renamed +to <structfield>frameperiod</structfield>. The now obsolete +<structfield>colorstandard</structfield> information, originally +needed to distguish between variations of standards, were +removed.</para> + + <para>Struct <structname>v4l2_enumstd</structname> 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 <structfield>std</structfield>, +respectively.</para> + </listitem> + + <listitem> + <para>The &v4l2-queryctrl; fields +<structfield>category</structfield> and +<structfield>group</structfield> did not catch on and/or were not +implemented as expected and therefore removed.</para> + </listitem> + + <listitem> + <para>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.</para> + + <para>In &v4l2-format; the <structfield>fmt</structfield> +union was extended to contain &v4l2-window;. All image format +negotiations are now possible with <constant>VIDIOC_G_FMT</constant>, +<constant>VIDIOC_S_FMT</constant> and +<constant>VIDIOC_TRY_FMT</constant>; ioctl. The +<constant>VIDIOC_G_WIN</constant> and +<constant>VIDIOC_S_WIN</constant> ioctls to prepare for a video +overlay were removed. The <structfield>type</structfield> field +changed to type &v4l2-buf-type; and the buffer type names changed as +follows.<informaltable> + <tgroup cols="2"> + <thead> + <row> + <entry>Old defines</entry> + <entry>&v4l2-buf-type;</entry> + </row> + </thead> + <tbody valign="top"> + <row> + <entry><constant>V4L2_BUF_TYPE_CAPTURE</constant></entry> + <entry><constant>V4L2_BUF_TYPE_VIDEO_CAPTURE</constant></entry> + </row> + <row> + <entry><constant>V4L2_BUF_TYPE_CODECIN</constant></entry> + <entry>Omitted for now</entry> + </row> + <row> + <entry><constant>V4L2_BUF_TYPE_CODECOUT</constant></entry> + <entry>Omitted for now</entry> + </row> + <row> + <entry><constant>V4L2_BUF_TYPE_EFFECTSIN</constant></entry> + <entry>Omitted for now</entry> + </row> + <row> + <entry><constant>V4L2_BUF_TYPE_EFFECTSIN2</constant></entry> + <entry>Omitted for now</entry> + </row> + <row> + <entry><constant>V4L2_BUF_TYPE_EFFECTSOUT</constant></entry> + <entry>Omitted for now</entry> + </row> + <row> + <entry><constant>V4L2_BUF_TYPE_VIDEOOUT</constant></entry> + <entry><constant>V4L2_BUF_TYPE_VIDEO_OUTPUT</constant></entry> + </row> + <row> + <entry><constant>-</constant></entry> + <entry><constant>V4L2_BUF_TYPE_VIDEO_OVERLAY</constant></entry> + </row> + <row> + <entry><constant>-</constant></entry> + <entry><constant>V4L2_BUF_TYPE_VBI_CAPTURE</constant></entry> + </row> + <row> + <entry><constant>-</constant></entry> + <entry><constant>V4L2_BUF_TYPE_VBI_OUTPUT</constant></entry> + </row> + <row> + <entry><constant>-</constant></entry> + <entry><constant>V4L2_BUF_TYPE_SLICED_VBI_CAPTURE</constant></entry> + </row> + <row> + <entry><constant>-</constant></entry> + <entry><constant>V4L2_BUF_TYPE_SLICED_VBI_OUTPUT</constant></entry> + </row> + <row> + <entry><constant>V4L2_BUF_TYPE_PRIVATE_BASE</constant></entry> + <entry><constant>V4L2_BUF_TYPE_PRIVATE</constant></entry> + </row> + </tbody> + </tgroup> + </informaltable></para> + </listitem> + + <listitem> + <para>In &v4l2-fmtdesc; a &v4l2-buf-type; field named +<structfield>type</structfield> was added as in &v4l2-format;. The +<constant>VIDIOC_ENUM_FBUFFMT</constant> ioctl is no longer needed and +was removed. These calls can be replaced by &VIDIOC-ENUM-FMT; with +type <constant>V4L2_BUF_TYPE_VIDEO_OVERLAY</constant>.</para> + </listitem> + + <listitem> + <para>In &v4l2-pix-format; the +<structfield>depth</structfield> 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 +<constant>V4L2_FMT_FLAG_COMPRESSED</constant> flag. The +<constant>V4L2_FMT_FLAG_SWCONVECOMPRESSED</constant> 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 +<constant>V4L2_FMT_FLAG_BYTESPERLINE</constant> flag was redundant. +Applications can set the <structfield>bytesperline</structfield> field +to zero to get a reasonable default. Since the remaining flags were +replaced as well, the <structfield>flags</structfield> field itself +was removed.</para> + <para>The interlace flags were replaced by a &v4l2-field; +value in a newly added <structfield>field</structfield> +field.<informaltable> + <tgroup cols="2"> + <thead> + <row> + <entry>Old flag</entry> + <entry>&v4l2-field;</entry> + </row> + </thead> + <tbody valign="top"> + <row> + <entry><constant>V4L2_FMT_FLAG_NOT_INTERLACED</constant></entry> + <entry>?</entry> + </row> + <row> + <entry><constant>V4L2_FMT_FLAG_INTERLACED</constant> += <constant>V4L2_FMT_FLAG_COMBINED</constant></entry> + <entry><constant>V4L2_FIELD_INTERLACED</constant></entry> + </row> + <row> + <entry><constant>V4L2_FMT_FLAG_TOPFIELD</constant> += <constant>V4L2_FMT_FLAG_ODDFIELD</constant></entry> + <entry><constant>V4L2_FIELD_TOP</constant></entry> + </row> + <row> + <entry><constant>V4L2_FMT_FLAG_BOTFIELD</constant> += <constant>V4L2_FMT_FLAG_EVENFIELD</constant></entry> + <entry><constant>V4L2_FIELD_BOTTOM</constant></entry> + </row> + <row> + <entry><constant>-</constant></entry> + <entry><constant>V4L2_FIELD_SEQ_TB</constant></entry> + </row> + <row> + <entry><constant>-</constant></entry> + <entry><constant>V4L2_FIELD_SEQ_BT</constant></entry> + </row> + <row> + <entry><constant>-</constant></entry> + <entry><constant>V4L2_FIELD_ALTERNATE</constant></entry> + </row> + </tbody> + </tgroup> + </informaltable></para> + + <para>The color space flags were replaced by a +&v4l2-colorspace; value in a newly added +<structfield>colorspace</structfield> field, where one of +<constant>V4L2_COLORSPACE_SMPTE170M</constant>, +<constant>V4L2_COLORSPACE_BT878</constant>, +<constant>V4L2_COLORSPACE_470_SYSTEM_M</constant> or +<constant>V4L2_COLORSPACE_470_SYSTEM_BG</constant> replaces +<constant>V4L2_FMT_CS_601YUV</constant>.</para> + </listitem> + + <listitem> + <para>In &v4l2-requestbuffers; the +<structfield>type</structfield> field was properly defined as +&v4l2-buf-type;. Buffer types changed as mentioned above. A new +<structfield>memory</structfield> field of type &v4l2-memory; was +added to distinguish between I/O methods using buffers allocated +by the driver or the application. See <xref linkend="io" /> for +details.</para> + </listitem> + + <listitem> + <para>In &v4l2-buffer; the <structfield>type</structfield> +field was properly defined as &v4l2-buf-type;. Buffer types changed as +mentioned above. A <structfield>field</structfield> 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 +<structfield>timestamp</structfield> field changed back from type +stamp_t, an unsigned 64 bit integer expressing the sample time in +nanoseconds, to struct <structname>timeval</structname>. With the +addition of a second memory mapping method the +<structfield>offset</structfield> field moved into union +<structfield>m</structfield>, and a new +<structfield>memory</structfield> field of type &v4l2-memory; was +added to distinguish between I/O methods. See <xref linkend="io" /> +for details.</para> + + <para>The <constant>V4L2_BUF_REQ_CONTIG</constant> +flag was used by the V4L compatibility layer, after changes to this +code it was no longer needed. The +<constant>V4L2_BUF_ATTR_DEVICEMEM</constant> 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.</para> + </listitem> + + <listitem> + <para>In &v4l2-framebuffer; the +<structfield>base[3]</structfield> array anticipating double- and +triple-buffering in off-screen video memory, however without defining +a synchronization mechanism, was replaced by a single pointer. The +<constant>V4L2_FBUF_CAP_SCALEUP</constant> and +<constant>V4L2_FBUF_CAP_SCALEDOWN</constant> flags were removed. +Applications can determine this capability more accurately using the +new cropping and scaling interface. The +<constant>V4L2_FBUF_CAP_CLIPPING</constant> flag was replaced by +<constant>V4L2_FBUF_CAP_LIST_CLIPPING</constant> and +<constant>V4L2_FBUF_CAP_BITMAP_CLIPPING</constant>.</para> + </listitem> + + <listitem> + <para>In &v4l2-clip; the <structfield>x</structfield>, +<structfield>y</structfield>, <structfield>width</structfield> and +<structfield>height</structfield> field moved into a +<structfield>c</structfield> substructure of type &v4l2-rect;. The +<structfield>x</structfield> and <structfield>y</structfield> fields +were renamed to <structfield>left</structfield> and +<structfield>top</structfield>, &ie; offsets to a context dependent +origin.</para> + </listitem> + + <listitem> + <para>In &v4l2-window; the <structfield>x</structfield>, +<structfield>y</structfield>, <structfield>width</structfield> and +<structfield>height</structfield> field moved into a +<structfield>w</structfield> substructure as above. A +<structfield>field</structfield> field of type %v4l2-field; was added +to distinguish between field and frame (interlaced) overlay.</para> + </listitem> + + <listitem> + <para>The digital zoom interface, including struct +<structname>v4l2_zoomcap</structname>, struct +<structname>v4l2_zoom</structname>, +<constant>V4L2_ZOOM_NONCAP</constant> and +<constant>V4L2_ZOOM_WHILESTREAMING</constant> was replaced by a new +cropping and scaling interface. The previously unused struct +<structname>v4l2_cropcap</structname> and +<structname>v4l2_crop</structname> where redefined for this purpose. +See <xref linkend="crop" /> for details.</para> + </listitem> + + <listitem> + <para>In &v4l2-vbi-format; the +<structfield>SAMPLE_FORMAT</structfield> field now contains a +four-character-code as used to identify video image formats and +<constant>V4L2_PIX_FMT_GREY</constant> replaces the +<constant>V4L2_VBI_SF_UBYTE</constant> define. The +<structfield>reserved</structfield> field was extended.</para> + </listitem> + + <listitem> + <para>In &v4l2-captureparm; the type of the +<structfield>timeperframe</structfield> 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 +<structfield>readbuffers</structfield> was added to control the driver +behaviour in read I/O mode.</para> + + <para>Similar changes were made to &v4l2-outputparm;.</para> + </listitem> + + <listitem> + <para>The struct <structname>v4l2_performance</structname> +and <constant>VIDIOC_G_PERF</constant> ioctl were dropped. Except when +using the <link linkend="rw">read/write I/O method</link>, which is +limited anyway, this information is already available to +applications.</para> + </listitem> + + <listitem> + <para>The example transformation from RGB to YCbCr color +space in the old V4L2 documentation was inaccurate, this has been +corrected in <xref linkend="pixfmt" />.<!-- 0.5670G should be +0.587, and 127/112 != 255/224 --></para> + </listitem> + </orderedlist> + </section> + + <section> + <title>V4L2 2003-06-19</title> + + <orderedlist> + <listitem> + <para>A new capability flag +<constant>V4L2_CAP_RADIO</constant> was added for radio devices. Prior +to this change radio devices would identify solely by having exactly one +tuner whose type field reads <constant>V4L2_TUNER_RADIO</constant>.</para> + </listitem> + + <listitem> + <para>An optional driver access priority mechanism was +added, see <xref linkend="app-pri" /> for details.</para> + </listitem> + + <listitem> + <para>The audio input and output interface was found to be +incomplete.</para> + <para>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 +<constant>VIDIOC_G_AUDIO</constant> was renamed to +<constant>VIDIOC_G_AUDIO_OLD</constant>, 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.</para> + <para>The same changes were made to &VIDIOC-G-AUDOUT; and +&VIDIOC-ENUMAUDOUT;.</para> + <para>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.</para> + </listitem> + + <listitem> + <para>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 <constant>VIDIOC_OVERLAY_OLD</constant>. 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.</para> + </listitem> + + <listitem> + <para><xref linkend="overlay" /> incorrectly stated that +clipping rectangles define regions where the video can be seen. +Correct is that clipping rectangles define regions where +<emphasis>no</emphasis> video shall be displayed and so the graphics +surface can be seen.</para> + </listitem> + + <listitem> + <para>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 +<constant>_OLD</constant> 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.</para> + </listitem> + </orderedlist> + </section> + + <section> + <title>V4L2 2003-11-05</title> + <orderedlist> + <listitem> + <para>In <xref linkend="pixfmt-rgb" /> the following pixel +formats were incorrectly transferred from Bill Dirks' V4L2 +specification. Descriptions below refer to bytes in memory, in +ascending address order.<informaltable> + <tgroup cols="3"> + <thead> + <row> + <entry>Symbol</entry> + <entry>In this document prior to revision +0.5</entry> + <entry>Corrected</entry> + </row> + </thead> + <tbody valign="top"> + <row> + <entry><constant>V4L2_PIX_FMT_RGB24</constant></entry> + <entry>B, G, R</entry> + <entry>R, G, B</entry> + </row> + <row> + <entry><constant>V4L2_PIX_FMT_BGR24</constant></entry> + <entry>R, G, B</entry> + <entry>B, G, R</entry> + </row> + <row> + <entry><constant>V4L2_PIX_FMT_RGB32</constant></entry> + <entry>B, G, R, X</entry> + <entry>R, G, B, X</entry> + </row> + <row> + <entry><constant>V4L2_PIX_FMT_BGR32</constant></entry> + <entry>R, G, B, X</entry> + <entry>B, G, R, X</entry> + </row> + </tbody> + </tgroup> + </informaltable> The +<constant>V4L2_PIX_FMT_BGR24</constant> example was always +correct.</para> + <para>In <xref linkend="v4l-image-properties" /> the mapping +of the V4L <constant>VIDEO_PALETTE_RGB24</constant> and +<constant>VIDEO_PALETTE_RGB32</constant> formats to V4L2 pixel formats +was accordingly corrected.</para> + </listitem> + + <listitem> + <para>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 <xref + linkend="pixfmt-rgb" />.</para> + </listitem> + </orderedlist> + </section> + + <section> + <title>V4L2 in Linux 2.6.6, 2004-05-09</title> + <orderedlist> + <listitem> + <para>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 +<constant>VIDIOC_CROPCAP_OLD</constant>. The old ioctl will be removed +in the future.</para> + </listitem> + </orderedlist> + </section> + + <section> + <title>V4L2 in Linux 2.6.8</title> + <orderedlist> + <listitem> + <para>A new field <structfield>input</structfield> (former +<structfield>reserved[0]</structfield>) 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 <constant>V4L2_BUF_FLAG_INPUT</constant> +flag. The <structfield>flags</structfield> field is no longer +read-only.</para> + </listitem> + </orderedlist> + </section> + + <section> + <title>V4L2 spec erratum 2004-08-01</title> + + <orderedlist> + <listitem> + <para>The return value of the +<xref linkend="func-open" /> function was incorrectly documented.</para> + </listitem> + + <listitem> + <para>Audio output ioctls end in -AUDOUT, not -AUDIOOUT.</para> + </listitem> + + <listitem> + <para>In the Current Audio Input example the +<constant>VIDIOC_G_AUDIO</constant> ioctl took the wrong +argument.</para> + </listitem> + + <listitem> + <para>The documentation of the &VIDIOC-QBUF; and +&VIDIOC-DQBUF; ioctls did not mention the &v4l2-buffer; +<structfield>memory</structfield> field. It was also missing from +examples. Also on the <constant>VIDIOC_DQBUF</constant> page the &EIO; +was not documented.</para> + </listitem> + </orderedlist> + </section> + + <section> + <title>V4L2 in Linux 2.6.14</title> + <orderedlist> + <listitem> + <para>A new sliced VBI interface was added. It is documented +in <xref linkend="sliced" /> and replaces the interface first +proposed in V4L2 specification 0.8.</para> + </listitem> + </orderedlist> + </section> + + <section> + <title>V4L2 in Linux 2.6.15</title> + <orderedlist> + <listitem> + <para>The &VIDIOC-LOG-STATUS; ioctl was added.</para> + </listitem> + + <listitem> + <para>New video standards +<constant>V4L2_STD_NTSC_443</constant>, +<constant>V4L2_STD_SECAM_LC</constant>, +<constant>V4L2_STD_SECAM_DK</constant> (a set of SECAM D, K and K1), +and <constant>V4L2_STD_ATSC</constant> (a set of +<constant>V4L2_STD_ATSC_8_VSB</constant> and +<constant>V4L2_STD_ATSC_16_VSB</constant>) were defined. Note the +<constant>V4L2_STD_525_60</constant> set now includes +<constant>V4L2_STD_NTSC_443</constant>. See also <xref + linkend="v4l2-std-id" />.</para> + </listitem> + + <listitem> + <para>The <constant>VIDIOC_G_COMP</constant> and +<constant>VIDIOC_S_COMP</constant> ioctl were renamed to +<constant>VIDIOC_G_MPEGCOMP</constant> and +<constant>VIDIOC_S_MPEGCOMP</constant> respectively. Their argument +was replaced by a struct +<structname>v4l2_mpeg_compression</structname> pointer. (The +<constant>VIDIOC_G_MPEGCOMP</constant> and +<constant>VIDIOC_S_MPEGCOMP</constant> ioctls where removed in Linux +2.6.25.)</para> + </listitem> + </orderedlist> + </section> + + <section> + <title>V4L2 spec erratum 2005-11-27</title> + <para>The capture example in <xref linkend="capture-example" /> +called the &VIDIOC-S-CROP; ioctl without checking if cropping is +supported. In the video standard selection example in +<xref linkend="standard" /> the &VIDIOC-S-STD; call used the wrong +argument type.</para> + </section> + + <section> + <title>V4L2 spec erratum 2006-01-10</title> + <orderedlist> + <listitem> + <para>The <constant>V4L2_IN_ST_COLOR_KILL</constant> 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.)</para> + </listitem> + + <listitem> + <para>&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.</para> + </listitem> + </orderedlist> + </section> + + <section> + <title>V4L2 spec erratum 2006-02-03</title> + <orderedlist> + <listitem> + <para>In &v4l2-captureparm; and &v4l2-outputparm; the +<structfield>timeperframe</structfield> field gives the time in +seconds, not microseconds.</para> + </listitem> + </orderedlist> + </section> + + <section> + <title>V4L2 spec erratum 2006-02-04</title> + <orderedlist> + <listitem> + <para>The <structfield>clips</structfield> field in +&v4l2-window; must point to an array of &v4l2-clip;, not a linked +list, because drivers ignore the struct +<structname>v4l2_clip</structname>.<structfield>next</structfield> +pointer.</para> + </listitem> + </orderedlist> + </section> + + <section> + <title>V4L2 in Linux 2.6.17</title> + <orderedlist> + <listitem> + <para>New video standard macros were added: +<constant>V4L2_STD_NTSC_M_KR</constant> (NTSC M South Korea), and the +sets <constant>V4L2_STD_MN</constant>, +<constant>V4L2_STD_B</constant>, <constant>V4L2_STD_GH</constant> and +<constant>V4L2_STD_DK</constant>. The +<constant>V4L2_STD_NTSC</constant> and +<constant>V4L2_STD_SECAM</constant> sets now include +<constant>V4L2_STD_NTSC_M_KR</constant> and +<constant>V4L2_STD_SECAM_LC</constant> respectively.</para> + </listitem> + + <listitem> + <para>A new <constant>V4L2_TUNER_MODE_LANG1_LANG2</constant> +was defined to record both languages of a bilingual program. The +use of <constant>V4L2_TUNER_MODE_STEREO</constant> for this purpose +is deprecated now. See the &VIDIOC-G-TUNER; section for +details.</para> + </listitem> + </orderedlist> + </section> + + <section> + <title>V4L2 spec erratum 2006-09-23 (Draft 0.15)</title> + <orderedlist> + <listitem> + <para>In various places +<constant>V4L2_BUF_TYPE_SLICED_VBI_CAPTURE</constant> and +<constant>V4L2_BUF_TYPE_SLICED_VBI_OUTPUT</constant> of the sliced VBI +interface were not mentioned along with other buffer types.</para> + </listitem> + + <listitem> + <para>In <xref linkend="vidioc-g-audio" /> it was clarified +that the &v4l2-audio; <structfield>mode</structfield> field is a flags +field.</para> + </listitem> + + <listitem> + <para><xref linkend="vidioc-querycap" /> did not mention the +sliced VBI and radio capability flags.</para> + </listitem> + + <listitem> + <para>In <xref linkend="vidioc-g-frequency" /> it was +clarified that applications must initialize the tuner +<structfield>type</structfield> field of &v4l2-frequency; before +calling &VIDIOC-S-FREQUENCY;.</para> + </listitem> + + <listitem> + <para>The <structfield>reserved</structfield> array +in &v4l2-requestbuffers; has 2 elements, not 32.</para> + </listitem> + + <listitem> + <para>In <xref linkend="output" /> and <xref + linkend="raw-vbi" /> the device file names +<filename>/dev/vout</filename> which never caught on were replaced +by <filename>/dev/video</filename>.</para> + </listitem> + + <listitem> + <para>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 +<filename>/dev/vbi0</filename> to <filename>/dev/vbi31</filename> are +possible now.</para> + </listitem> + </orderedlist> + </section> + + <section> + <title>V4L2 in Linux 2.6.18</title> + <orderedlist> + <listitem> + <para>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 +<constant>V4L2_CTRL_TYPE_INTEGER64</constant> and +<constant>V4L2_CTRL_TYPE_CTRL_CLASS</constant> (<xref + linkend="v4l2-ctrl-type" />), and new control flags +<constant>V4L2_CTRL_FLAG_READ_ONLY</constant>, +<constant>V4L2_CTRL_FLAG_UPDATE</constant>, +<constant>V4L2_CTRL_FLAG_INACTIVE</constant> and +<constant>V4L2_CTRL_FLAG_SLIDER</constant> (<xref + linkend="control-flags" />). See <xref + linkend="extended-controls" /> for details.</para> + </listitem> + </orderedlist> + </section> + + <section> + <title>V4L2 in Linux 2.6.19</title> + <orderedlist> + <listitem> + <para>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 <emphasis>break the +compatibility</emphasis> with older drivers and applications.</para> + </listitem> + + <listitem> + <para>The ioctls &VIDIOC-ENUM-FRAMESIZES; and +&VIDIOC-ENUM-FRAMEINTERVALS; were added.</para> + </listitem> + + <listitem> + <para>A new pixel format <constant>V4L2_PIX_FMT_RGB444</constant> (<xref +linkend="rgb-formats" />) was added.</para> + </listitem> + </orderedlist> + </section> + + <section> + <title>V4L2 spec erratum 2006-10-12 (Draft 0.17)</title> + <orderedlist> + <listitem> + <para><constant>V4L2_PIX_FMT_HM12</constant> (<xref +linkend="reserved-formats" />) is a YUV 4:2:0, not 4:2:2 format.</para> + </listitem> + </orderedlist> + </section> + + <section> + <title>V4L2 in Linux 2.6.21</title> + <orderedlist> + <listitem> + <para>The <filename>videodev2.h</filename> header file is +now dual licensed under GNU General Public License version two or +later, and under a 3-clause BSD-style license.</para> + </listitem> + </orderedlist> + </section> + + <section> + <title>V4L2 in Linux 2.6.22</title> + <orderedlist> + <listitem> + <para>Two new field orders + <constant>V4L2_FIELD_INTERLACED_TB</constant> and + <constant>V4L2_FIELD_INTERLACED_BT</constant> were + added. See <xref linkend="v4l2-field" /> for details.</para> + </listitem> + + <listitem> + <para>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.</para> + <para>A new <structfield>global_alpha</structfield> field +was added to <link +linkend="v4l2-window"><structname>v4l2_window</structname></link>, +extending the structure. This may <emphasis>break +compatibility</emphasis> with applications using a struct +<structname>v4l2_window</structname> directly. However the <link +linkend="vidioc-g-fmt">VIDIOC_G/S/TRY_FMT</link> ioctls, which take a +pointer to a <link linkend="v4l2-format">v4l2_format</link> parent +structure with padding bytes at the end, are not affected.</para> + </listitem> + + <listitem> + <para>The format of the <structfield>chromakey</structfield> +field in &v4l2-window; changed from "host order RGB32" to a pixel +value in the same format as the framebuffer. This may <emphasis>break +compatibility</emphasis> with existing applications. Drivers +supporting the "host order RGB32" format are not known.</para> + </listitem> + + </orderedlist> + </section> + + <section> + <title>V4L2 in Linux 2.6.24</title> + <orderedlist> + <listitem> + <para>The pixel formats +<constant>V4L2_PIX_FMT_PAL8</constant>, +<constant>V4L2_PIX_FMT_YUV444</constant>, +<constant>V4L2_PIX_FMT_YUV555</constant>, +<constant>V4L2_PIX_FMT_YUV565</constant> and +<constant>V4L2_PIX_FMT_YUV32</constant> were added.</para> + </listitem> + </orderedlist> + </section> + + <section> + <title>V4L2 in Linux 2.6.25</title> + <orderedlist> + <listitem> + <para>The pixel formats <link linkend="V4L2-PIX-FMT-Y16"> +<constant>V4L2_PIX_FMT_Y16</constant></link> and <link +linkend="V4L2-PIX-FMT-SBGGR16"> +<constant>V4L2_PIX_FMT_SBGGR16</constant></link> were added.</para> + </listitem> + <listitem> + <para>New <link linkend="control">controls</link> +<constant>V4L2_CID_POWER_LINE_FREQUENCY</constant>, +<constant>V4L2_CID_HUE_AUTO</constant>, +<constant>V4L2_CID_WHITE_BALANCE_TEMPERATURE</constant>, +<constant>V4L2_CID_SHARPNESS</constant> and +<constant>V4L2_CID_BACKLIGHT_COMPENSATION</constant> were added. The +controls <constant>V4L2_CID_BLACK_LEVEL</constant>, +<constant>V4L2_CID_WHITENESS</constant>, +<constant>V4L2_CID_HCENTER</constant> and +<constant>V4L2_CID_VCENTER</constant> were deprecated. +</para> + </listitem> + <listitem> + <para>A <link linkend="camera-controls">Camera controls +class</link> was added, with the new controls +<constant>V4L2_CID_EXPOSURE_AUTO</constant>, +<constant>V4L2_CID_EXPOSURE_ABSOLUTE</constant>, +<constant>V4L2_CID_EXPOSURE_AUTO_PRIORITY</constant>, +<constant>V4L2_CID_PAN_RELATIVE</constant>, +<constant>V4L2_CID_TILT_RELATIVE</constant>, +<constant>V4L2_CID_PAN_RESET</constant>, +<constant>V4L2_CID_TILT_RESET</constant>, +<constant>V4L2_CID_PAN_ABSOLUTE</constant>, +<constant>V4L2_CID_TILT_ABSOLUTE</constant>, +<constant>V4L2_CID_FOCUS_ABSOLUTE</constant>, +<constant>V4L2_CID_FOCUS_RELATIVE</constant> and +<constant>V4L2_CID_FOCUS_AUTO</constant>.</para> + </listitem> + <listitem> + <para>The <constant>VIDIOC_G_MPEGCOMP</constant> and +<constant>VIDIOC_S_MPEGCOMP</constant> ioctls, which were superseded +by the <link linkend="extended-controls">extended controls</link> +interface in Linux 2.6.18, where finally removed from the +<filename>videodev2.h</filename> header file.</para> + </listitem> + </orderedlist> + </section> + + <section> + <title>V4L2 in Linux 2.6.26</title> + <orderedlist> + <listitem> + <para>The pixel formats +<constant>V4L2_PIX_FMT_Y16</constant> and +<constant>V4L2_PIX_FMT_SBGGR16</constant> were added.</para> + </listitem> + <listitem> + <para>Added user controls +<constant>V4L2_CID_CHROMA_AGC</constant> and +<constant>V4L2_CID_COLOR_KILLER</constant>.</para> + </listitem> + </orderedlist> + </section> + + <section> + <title>V4L2 in Linux 2.6.27</title> + <orderedlist> + <listitem> + <para>The &VIDIOC-S-HW-FREQ-SEEK; ioctl and the +<constant>V4L2_CAP_HW_FREQ_SEEK</constant> capability were added.</para> + </listitem> + <listitem> + <para>The pixel formats +<constant>V4L2_PIX_FMT_YVYU</constant>, +<constant>V4L2_PIX_FMT_PCA501</constant>, +<constant>V4L2_PIX_FMT_PCA505</constant>, +<constant>V4L2_PIX_FMT_PCA508</constant>, +<constant>V4L2_PIX_FMT_PCA561</constant>, +<constant>V4L2_PIX_FMT_SGBRG8</constant>, +<constant>V4L2_PIX_FMT_PAC207</constant> and +<constant>V4L2_PIX_FMT_PJPG</constant> were added.</para> + </listitem> + </orderedlist> + </section> + + <section> + <title>V4L2 in Linux 2.6.28</title> + <orderedlist> + <listitem> + <para>Added <constant>V4L2_MPEG_AUDIO_ENCODING_AAC</constant> and +<constant>V4L2_MPEG_AUDIO_ENCODING_AC3</constant> MPEG audio encodings.</para> + </listitem> + <listitem> + <para>Added <constant>V4L2_MPEG_VIDEO_ENCODING_MPEG_4_AVC</constant> MPEG +video encoding.</para> + </listitem> + <listitem> + <para>The pixel formats +<constant>V4L2_PIX_FMT_SGRBG10</constant> and +<constant>V4L2_PIX_FMT_SGRBG10DPCM8</constant> were added.</para> + </listitem> + </orderedlist> + </section> + + <section> + <title>V4L2 in Linux 2.6.29</title> + <orderedlist> + <listitem> + <para>The <constant>VIDIOC_G_CHIP_IDENT</constant> ioctl was renamed +to <constant>VIDIOC_G_CHIP_IDENT_OLD</constant> and &VIDIOC-DBG-G-CHIP-IDENT; +was introduced in its place. The old struct <structname>v4l2_chip_ident</structname> +was renamed to <structname id="v4l2-chip-ident-old">v4l2_chip_ident_old</structname>.</para> + </listitem> + <listitem> + <para>The pixel formats +<constant>V4L2_PIX_FMT_VYUY</constant>, +<constant>V4L2_PIX_FMT_NV16</constant> and +<constant>V4L2_PIX_FMT_NV61</constant> were added.</para> + </listitem> + <listitem> + <para>Added camera controls +<constant>V4L2_CID_ZOOM_ABSOLUTE</constant>, +<constant>V4L2_CID_ZOOM_RELATIVE</constant>, +<constant>V4L2_CID_ZOOM_CONTINUOUS</constant> and +<constant>V4L2_CID_PRIVACY</constant>.</para> + </listitem> + </orderedlist> + </section> + <section> + <title>V4L2 in Linux 2.6.30</title> + <orderedlist> + <listitem> + <para>New control flag <constant>V4L2_CTRL_FLAG_WRITE_ONLY</constant> was added.</para> + </listitem> + <listitem> + <para>New control <constant>V4L2_CID_COLORFX</constant> was added.</para> + </listitem> + </orderedlist> + </section> + <section> + <title>V4L2 in Linux 2.6.32</title> + <orderedlist> + <listitem> + <para>In order to be easier to compare a V4L2 API and a kernel +version, now V4L2 API is numbered using the Linux Kernel version numeration.</para> + </listitem> + <listitem> + <para>Finalized the RDS capture API. See <xref linkend="rds" /> for +more information.</para> + </listitem> + <listitem> + <para>Added new capabilities for modulators and RDS encoders.</para> + </listitem> + <listitem> + <para>Add description for libv4l API.</para> + </listitem> + <listitem> + <para>Added support for string controls via new type <constant>V4L2_CTRL_TYPE_STRING</constant>.</para> + </listitem> + <listitem> + <para>Added <constant>V4L2_CID_BAND_STOP_FILTER</constant> documentation.</para> + </listitem> + <listitem> + <para>Added FM Modulator (FM TX) Extended Control Class: <constant>V4L2_CTRL_CLASS_FM_TX</constant> and their Control IDs.</para> + </listitem> + <listitem> + <para>Added Remote Controller chapter, describing the default Remote Controller mapping for media devices.</para> + </listitem> + </orderedlist> + </section> + </section> + + <section id="other"> + <title>Relation of V4L2 to other Linux multimedia APIs</title> + + <section id="xvideo"> + <title>X Video Extension</title> + + <para>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<footnote> + <para>This is not implemented in XFree86.</para> + </footnote>. With their implementation XFree86 makes the +extension available across many operating systems and +architectures.</para> + + <para>Because the driver is embedded into the X server Xv has a +number of advantages over the V4L2 <link linkend="overlay">video +overlay interface</link>. 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.</para> + + <para>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 +<filename>/etc/X11/XF86Config</filename> must contain these lines:</para> + <para><screen> +Section "Module" + Load "v4l" +EndSection</screen></para> + + <para>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 <xref + linkend="overlay" /> apply.</para> + + <para>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.</para> + </section> + + <section> + <title>Digital Video</title> + + <para>V4L2 does not support digital terrestrial, cable or +satellite broadcast. A separate project aiming at digital receivers +exists. You can find its homepage at <ulink +url="http://linuxtv.org">http://linuxtv.org</ulink>. The Linux DVB API +has no connection to the V4L2 API except that drivers for hybrid +hardware may support both.</para> + </section> + + <section> + <title>Audio Interfaces</title> + + <para>[to do - OSS/ALSA]</para> + </section> + </section> + + <section id="experimental"> + <title>Experimental API Elements</title> + + <para>The following V4L2 API elements are currently experimental +and may change in the future.</para> + + <itemizedlist> + <listitem> + <para>Video Output Overlay (OSD) Interface, <xref + linkend="osd" />.</para> + </listitem> + <listitem> + <para><constant>V4L2_BUF_TYPE_VIDEO_OUTPUT_OVERLAY</constant>, + &v4l2-buf-type;, <xref linkend="v4l2-buf-type" />.</para> + </listitem> + <listitem> + <para><constant>V4L2_CAP_VIDEO_OUTPUT_OVERLAY</constant>, +&VIDIOC-QUERYCAP; ioctl, <xref linkend="device-capabilities" />.</para> + </listitem> + <listitem> + <para>&VIDIOC-ENUM-FRAMESIZES; and +&VIDIOC-ENUM-FRAMEINTERVALS; ioctls.</para> + </listitem> + <listitem> + <para>&VIDIOC-G-ENC-INDEX; ioctl.</para> + </listitem> + <listitem> + <para>&VIDIOC-ENCODER-CMD; and &VIDIOC-TRY-ENCODER-CMD; +ioctls.</para> + </listitem> + <listitem> + <para>&VIDIOC-DBG-G-REGISTER; and &VIDIOC-DBG-S-REGISTER; +ioctls.</para> + </listitem> + <listitem> + <para>&VIDIOC-DBG-G-CHIP-IDENT; ioctl.</para> + </listitem> + </itemizedlist> + </section> + + <section id="obsolete"> + <title>Obsolete API Elements</title> + + <para>The following V4L2 API elements were superseded by new +interfaces and should not be implemented in new drivers.</para> + + <itemizedlist> + <listitem> + <para><constant>VIDIOC_G_MPEGCOMP</constant> and +<constant>VIDIOC_S_MPEGCOMP</constant> ioctls. Use Extended Controls, +<xref linkend="extended-controls" />.</para> + </listitem> + </itemizedlist> + </section> + + <!-- +Local Variables: +mode: sgml +sgml-parent-document: "v4l2.sgml" +indent-tabs-mode: nil +End: + --> |