<!DOCTYPE book PUBLIC "-//OASIS//DTD DocBook V3.1//EN" [
<!ENTITY % entities SYSTEM "entities.sgml"> %entities;
<!ENTITY indices SYSTEM "indices.sgml">
<!ENTITY eg "e. g.">
<!ENTITY ie "i. e.">
<!ENTITY fd "File descriptor returned by <link linkend='func-open'><function>open()</function></link>.">
<!ENTITY i2c "I<superscript>2</superscript>C">
<!ENTITY return-value "<title>Return Value</title><para>On success <returnvalue>0</returnvalue> is returned, on error <returnvalue>-1</returnvalue> and the <varname>errno</varname> variable is set appropriately:</para>">
<!ENTITY manvol "<manvolnum>2</manvolnum>">
<!-- Table templates: structs, structs w/union, defines. -->
<!ENTITY cs-str "<colspec colname='c1' colwidth='1*'><colspec colname='c2' colwidth='1*'><colspec colname='c3' colwidth='2*'><spanspec spanname='hspan' namest='c1' nameend='c3'>">
<!ENTITY cs-ustr "<colspec colname='c1' colwidth='1*'><colspec colname='c2' colwidth='1*'><colspec colname='c3' colwidth='1*'><colspec colname='c4' colwidth='2*'><spanspec spanname='hspan' namest='c1' nameend='c4'>">
<!ENTITY cs-def "<colspec colname='c1' colwidth='3*'><colspec colname='c2' colwidth='1*'><colspec colname='c3' colwidth='4*'><spanspec spanname='hspan' namest='c1' nameend='c3'>">
<!-- Video for Linux mailing list address. -->
<!ENTITY v4l-ml "<ulink url='http://www.linuxtv.org/lists.php'>http://www.linuxtv.org/lists.php</ulink>">
<!-- LinuxTV v4l-dvb repository. -->
<!ENTITY v4l-dvb "<ulink url='http://linuxtv.org/repo/'>http://linuxtv.org/repo/</ulink>">
]>
<book id="v4l2spec">
<bookinfo>
<title>Video for Linux Two API Specification</title>
<subtitle>Revision 0.25</subtitle>
<authorgroup>
<author>
<firstname>Michael</firstname>
<surname>Schimek</surname>
<othername role="mi">H</othername>
<affiliation>
<address>
<email>mschimek@gmx.at</email>
</address>
</affiliation>
</author>
<author>
<firstname>Bill</firstname>
<surname>Dirks</surname>
<!-- Commented until Bill opts in to be spammed.
<affiliation>
<address>
<email>bill@thedirks.org</email>
</address>
</affiliation> -->
<contrib>Original author of the V4L2 API and
documentation.</contrib>
</author>
<author>
<firstname>Hans</firstname>
<surname>Verkuil</surname>
<contrib>Designed and documented the VIDIOC_LOG_STATUS ioctl,
the extended control ioctls and major parts of the sliced VBI
API.</contrib>
<affiliation>
<address>
<email>hverkuil@xs4all.nl</email>
</address>
</affiliation>
</author>
<author>
<firstname>Martin</firstname>
<surname>Rubli</surname>
<!--
<affiliation>
<address>
<email>martin_rubli@logitech.com</email>
</address>
</affiliation> -->
<contrib>Designed and documented the VIDIOC_ENUM_FRAMESIZES
and VIDIOC_ENUM_FRAMEINTERVALS ioctls.</contrib>
</author>
</authorgroup>
<copyright>
<year>1999</year>
<year>2000</year>
<year>2001</year>
<year>2002</year>
<year>2003</year>
<year>2004</year>
<year>2005</year>
<year>2006</year>
<year>2007</year>
<year>2008</year>
<year>2009</year>
<holder>Bill Dirks, Michael H. Schimek, Hans Verkuil, Martin
Rubli</holder>
</copyright>
<legalnotice>
<para>This document is copyrighted © 1999-2009 by Bill
Dirks, Michael H. Schimek, Hans Verkuil and Martin Rubli.</para>
<para>Permission is granted to copy, distribute and/or modify
this document under the terms of the GNU Free Documentation License,
Version 1.1 or any later version published by the Free Software
Foundation; with no Invariant Sections, with no Front-Cover Texts, and
with no Back-Cover Texts. A copy of the license is included in the
appendix entitled "GNU Free Documentation License".</para>
<para>Programming examples can be used and distributed without
restrictions.</para>
</legalnotice>
<revhistory>
<!-- Put document revisions here, newest first. -->
<!-- API revisions (changes and additions of defines, enums,
structs, ioctls) must be noted in more detail in the history chapter
(compat.sgml), along with the possible impact on existing drivers and
applications. -->
<revision>
<revnumber>0.25</revnumber>
<date>2009-01-18</date>
<authorinitials>hv</authorinitials>
<revremark>Added pixel formats VYUY, NV16 and NV61, and changed
the debug ioctls VIDIOC_DBG_G/S_REGISTER and VIDIOC_DBG_G_CHIP_IDENT.
Added camera controls V4L2_CID_ZOOM_ABSOLUTE, V4L2_CID_ZOOM_RELATIVE,
V4L2_CID_ZOOM_CONTINUOUS and V4L2_CID_PRIVACY.</revremark>
</revision>
<revision>
<revnumber>0.24</revnumber>
<date>2008-03-04</date>
<authorinitials>mhs</authorinitials>
<revremark>Added pixel formats Y16 and SBGGR16, new controls
and a camera controls class. Removed VIDIOC_G/S_MPEGCOMP.</revremark>
</revision>
<revision>
<revnumber>0.23</revnumber>
<date>2007-08-30</date>
<authorinitials>mhs</authorinitials>
<revremark>Fixed a typo in VIDIOC_DBG_G/S_REGISTER.
Clarified the byte order of packed pixel formats.</revremark>
</revision>
<revision>
<revnumber>0.22</revnumber>
<date>2007-08-29</date>
<authorinitials>mhs</authorinitials>
<revremark>Added the Video Output Overlay interface, new MPEG
controls, V4L2_FIELD_INTERLACED_TB and V4L2_FIELD_INTERLACED_BT,
VIDIOC_DBG_G/S_REGISTER, VIDIOC_(TRY_)ENCODER_CMD,
VIDIOC_G_CHIP_IDENT, VIDIOC_G_ENC_INDEX, new pixel formats.
Clarifications in the cropping chapter, about RGB pixel formats, the
mmap(), poll(), select(), read() and write() functions. Typographical
fixes.</revremark>
</revision>
<revision>
<revnumber>0.21</revnumber>
<date>2006-12-19</date>
<authorinitials>mhs</authorinitials>
<revremark>Fixed a link in the VIDIOC_G_EXT_CTRLS section.</revremark>
</revision>
<revision>
<revnumber>0.20</revnumber>
<date>2006-11-24</date>
<authorinitials>mhs</authorinitials>
<revremark>Clarified the purpose of the audioset field in
struct v4l2_input and v4l2_output.</revremark>
</revision>
<revision>
<revnumber>0.19</revnumber>
<date>2006-10-19</date>
<authorinitials>mhs</authorinitials>
<revremark>Documented V4L2_PIX_FMT_RGB444.</revremark>
</revision>
<revision>
<revnumber>0.18</revnumber>
<date>2006-10-18</date>
<authorinitials>mhs</authorinitials>
<revremark>Added the description of extended controls by Hans
Verkuil. Linked V4L2_PIX_FMT_MPEG to V4L2_CID_MPEG_STREAM_TYPE.</revremark>
</revision>
<revision>
<revnumber>0.17</revnumber>
<date>2006-10-12</date>
<authorinitials>mhs</authorinitials>
<revremark>Corrected V4L2_PIX_FMT_HM12 description.</revremark>
</revision>
<revision>
<revnumber>0.16</revnumber>
<date>2006-10-08</date>
<authorinitials>mhs</authorinitials>
<revremark>VIDIOC_ENUM_FRAMESIZES and
VIDIOC_ENUM_FRAMEINTERVALS are now part of the API.</revremark>
</revision>
<revision>
<revnumber>0.15</revnumber>
<date>2006-09-23</date>
<authorinitials>mhs</authorinitials>
<revremark>Cleaned up the bibliography, added BT.653 and
BT.1119. capture.c/start_capturing() for user pointer I/O did not
initialize the buffer index. Documented the V4L MPEG and MJPEG
VID_TYPEs and V4L2_PIX_FMT_SBGGR8. Updated the list of reserved pixel
formats. See the history chapter for API changes.</revremark>
</revision>
<revision>
<revnumber>0.14</revnumber>
<date>2006-09-14</date>
<authorinitials>mr</authorinitials>
<revremark>Added VIDIOC_ENUM_FRAMESIZES and
VIDIOC_ENUM_FRAMEINTERVALS proposal for frame format enumeration of
digital devices.</revremark>
</revision>
<revision>
<revnumber>0.13</revnumber>
<date>2006-04-07</date>
<authorinitials>mhs</authorinitials>
<revremark>Corrected the description of struct v4l2_window
clips. New V4L2_STD_ and V4L2_TUNER_MODE_LANG1_LANG2
defines.</revremark>
</revision>
<revision>
<revnumber>0.12</revnumber>
<date>2006-02-03</date>
<authorinitials>mhs</authorinitials>
<revremark>Corrected the description of struct
v4l2_captureparm and v4l2_outputparm.</revremark>
</revision>
<revision>
<revnumber>0.11</revnumber>
<date>2006-01-27</date>
<authorinitials>mhs</authorinitials>
<revremark>Improved the description of struct
v4l2_tuner.</revremark>
</revision>
<revision>
<revnumber>0.10</revnumber>
<date>2006-01-10</date>
<authorinitials>mhs</authorinitials>
<revremark>VIDIOC_G_INPUT and VIDIOC_S_PARM
clarifications.</revremark>
</revision>
<revision>
<revnumber>0.9</revnumber>
<date>2005-11-27</date>
<authorinitials>mhs</authorinitials>
<revremark>Improved the 525 line numbering diagram. Hans
Verkuil and I rewrote the sliced VBI section. He also contributed a
VIDIOC_LOG_STATUS page. Fixed VIDIOC_S_STD call in the video standard
selection example. Various updates.</revremark>
</revision>
<revision>
<revnumber>0.8</revnumber>
<date>2004-10-04</date>
<authorinitials>mhs</authorinitials>
<revremark>Somehow a piece of junk slipped into the capture
example, removed.</revremark>
</revision>
<revision>
<revnumber>0.7</revnumber>
<date>2004-09-19</date>
<authorinitials>mhs</authorinitials>
<revremark>Fixed video standard selection, control
enumeration, downscaling and aspect example. Added read and user
pointer i/o to video capture example.</revremark>
</revision>
<revision>
<revnumber>0.6</revnumber>
<date>2004-08-01</date>
<authorinitials>mhs</authorinitials>
<revremark>v4l2_buffer changes, added video capture example,
various corrections.</revremark>
</revision>
<revision>
<revnumber>0.5</revnumber>
<date>2003-11-05</date>
<authorinitials>mhs</authorinitials>
<revremark>Pixel format erratum.</revremark>
</revision>
<revision>
<revnumber>0.4</revnumber>
<date>2003-09-17</date>
<authorinitials>mhs</authorinitials>
<revremark>Corrected source and Makefile to generate a PDF.
SGML fixes. Added latest API changes. Closed gaps in the history
chapter.</revremark>
</revision>
<revision>
<revnumber>0.3</revnumber>
<date>2003-02-05</date>
<authorinitials>mhs</authorinitials>
<revremark>Another draft, more corrections.</revremark>
</revision>
<revision>
<revnumber>0.2</revnumber>
<date>2003-01-15</date>
<authorinitials>mhs</authorinitials>
<revremark>Second draft, with corrections pointed out by Gerd
Knorr.</revremark>
</revision>
<revision>
<revnumber>0.1</revnumber>
<date>2002-12-01</date>
<authorinitials>mhs</authorinitials>
<revremark>First draft, based on documentation by Bill Dirks
and discussions on the V4L mailing list.</revremark>
</revision>
</revhistory>
</bookinfo>
<toc></toc> <!-- autogenerated -->
<preface>
<title>Introduction</title>
<para>Video For Linux Two is the second version of the Video For
Linux API, a kernel interface for analog radio and video capture and
output drivers.</para>
<para>Early drivers used ad-hoc interfaces. These were replaced in
Linux 2.2 by Alan Cox' V4L API, based on the interface of the bttv
driver. In 1999 Bill Dirks started the development of V4L2 to fix some
shortcomings of V4L and to support a wider range of devices. The API
was revised again in 2002 prior to its inclusion in Linux 2.5/2.6, and
work continues on improvements and additions while maintaining
compatibility with existing drivers and applications. In 2006/2007
efforts began on FreeBSD drivers with a V4L2 interface.</para>
<para>This book documents the V4L2 API. Intended audience are
driver and application writers.</para>
<para>If you have questions or ideas regarding the API, please
write to the linux-media mailing list: &v4l-ml;.</para>
<para>The latest version of this document and the DocBook SGML
sources are part of the &v4l-dvb; repository. The online version is
available here: <ulink url="http://linuxtv.org/downloads/video4linux/API/V4L2_API">http://linuxtv.org/downloads/video4linux/API/V4L2_API</ulink>.</para>
</preface>
<chapter id="common">
&sub-common;
</chapter>
<chapter id="pixfmt">
&sub-pixfmt;
</chapter>
<chapter id="io">
&sub-io;
</chapter>
<chapter id="devices">
<title>Interfaces</title>
<section id="capture"> &sub-dev-capture; </section>
<section id="overlay"> &sub-dev-overlay; </section>
<section id="output"> &sub-dev-output; </section>
<section id="osd"> &sub-dev-osd; </section>
<section id="codec"> &sub-dev-codec; </section>
<section id="effect"> &sub-dev-effect; </section>
<section id="raw-vbi"> &sub-dev-raw-vbi; </section>
<section id="sliced"> &sub-dev-sliced-vbi; </section>
<section id="ttx"> &sub-dev-teletext; </section>
<section id="radio"> &sub-dev-radio; </section>
<section id="rds"> &sub-dev-rds; </section>
</chapter>
<reference id="user-func">
<title>Function Reference</title>
<!-- Keep this alphabetically sorted. -->
&sub-close;
&sub-ioctl;
<!-- All ioctls go here. -->
&sub-cropcap;
&sub-dbg-g-chip-ident;
&sub-dbg-g-register;
&sub-encoder-cmd;
&sub-enumaudio;
&sub-enumaudioout;
&sub-enum-fmt;
&sub-enum-framesizes;
&sub-enum-frameintervals;
&sub-enuminput;
&sub-enumoutput;
&sub-enumstd;
&sub-g-audio;
&sub-g-audioout;
&sub-g-crop;
&sub-g-ctrl;
&sub-g-enc-index;
&sub-g-ext-ctrls;
&sub-g-fbuf;
&sub-g-fmt;
&sub-g-frequency;
&sub-g-input;
&sub-g-jpegcomp;
&sub-g-modulator;
&sub-g-output;
&sub-g-parm;
&sub-g-priority;
&sub-g-sliced-vbi-cap;
&sub-g-std;
&sub-g-tuner;
&sub-log-status;
&sub-overlay;
&sub-qbuf;
&sub-querybuf;
&sub-querycap;
&sub-queryctrl;
&sub-querystd;
&sub-reqbufs;
&sub-s-hw-freq-seek;
&sub-streamon;
<!-- End of ioctls. -->
&sub-mmap;
&sub-munmap;
&sub-open;
&sub-poll;
&sub-read;
&sub-select;
&sub-write;
</reference>
<chapter id="driver">
&sub-driver;
</chapter>
<chapter id="compat">
&sub-compat;
</chapter>
<appendix id="videodev">
<title>Video For Linux Two Header File</title>
&sub-videodev2-h;
</appendix>
<appendix id="capture-example">
<title>Video Capture Example</title>
&sub-capture-c;
</appendix>
&sub-fdl-appendix;
&sub-indices;
&sub-biblio;
</book>