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<html xmlns="http://www.w3.org/1999/xhtml"><head><meta http-equiv="Content-Type" content="text/html; charset=ANSI_X3.4-1968" /><title>Chapter 7. Changes</title><meta name="generator" content="DocBook XSL Stylesheets V1.75.2" /><link rel="home" href="index.html" title="LINUX MEDIA INFRASTRUCTURE API" /><link rel="up" href="pt01.html" title="Part I. Video for Linux Two API Specification" /><link rel="prev" href="ch06.html" title="Chapter 6. Libv4l Userspace Library" /><link rel="next" href="ch07s02.html" title="Changes of the V4L2 API" /></head><body><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="3" align="center">Chapter 7. Changes</th></tr><tr><td width="20%" align="left"><a accesskey="p" href="ch06.html">Prev</a> </td><th width="60%" align="center">Part I. Video for Linux Two API Specification</th><td width="20%" align="right"> <a accesskey="n" href="ch07s02.html">Next</a></td></tr></table><hr /></div><div class="chapter" title="Chapter 7. Changes"><div class="titlepage"><div><div><h2 class="title"><a id="compat"></a>Chapter 7. Changes</h2></div></div></div><div class="toc"><p><b>Table of Contents</b></p><dl><dt><span class="section"><a href="ch07.html#diff-v4l">Differences between V4L and V4L2</a></span></dt><dd><dl><dt><span class="section"><a href="ch07.html#id2665771">Opening and Closing Devices</a></span></dt><dt><span class="section"><a href="ch07.html#id2667495">Querying Capabilities</a></span></dt><dt><span class="section"><a href="ch07.html#id2668054">Video Sources</a></span></dt><dt><span class="section"><a href="ch07.html#id2668280">Tuning</a></span></dt><dt><span class="section"><a href="ch07.html#v4l-image-properties">Image Properties</a></span></dt><dt><span class="section"><a href="ch07.html#id2669086">Audio</a></span></dt><dt><span class="section"><a href="ch07.html#id2669409">Frame Buffer Overlay</a></span></dt><dt><span class="section"><a href="ch07.html#id2669683">Cropping</a></span></dt><dt><span class="section"><a href="ch07.html#id2669828">Reading Images, Memory Mapping</a></span></dt><dt><span class="section"><a href="ch07.html#id2670176">Reading Raw VBI Data</a></span></dt><dt><span class="section"><a href="ch07.html#id2670390">Miscellaneous</a></span></dt></dl></dd><dt><span class="section"><a href="ch07s02.html">Changes of the V4L2 API</a></span></dt><dd><dl><dt><span class="section"><a href="ch07s02.html#id2670451">Early Versions</a></span></dt><dt><span class="section"><a href="ch07s02.html#id2670665">V4L2 Version 0.16 1999-01-31</a></span></dt><dt><span class="section"><a href="ch07s02.html#id2670680">V4L2 Version 0.18 1999-03-16</a></span></dt><dt><span class="section"><a href="ch07s02.html#id2670696">V4L2 Version 0.19 1999-06-05</a></span></dt><dt><span class="section"><a href="ch07s02.html#id2670741">V4L2 Version 0.20 (1999-09-10)</a></span></dt><dt><span class="section"><a href="ch07s02.html#id2671044">V4L2 Version 0.20 incremental changes</a></span></dt><dt><span class="section"><a href="ch07s02.html#id2671293">V4L2 Version 0.20 2000-11-23</a></span></dt><dt><span class="section"><a href="ch07s02.html#id2671440">V4L2 Version 0.20 2002-07-25</a></span></dt><dt><span class="section"><a href="ch07s02.html#id2671451">V4L2 in Linux 2.5.46, 2002-10</a></span></dt><dt><span class="section"><a href="ch07s02.html#id2673058">V4L2 2003-06-19</a></span></dt><dt><span class="section"><a href="ch07s02.html#id2673241">V4L2 2003-11-05</a></span></dt><dt><span class="section"><a href="ch07s02.html#id2673398">V4L2 in Linux 2.6.6, 2004-05-09</a></span></dt><dt><span class="section"><a href="ch07s02.html#id2673433">V4L2 in Linux 2.6.8</a></span></dt><dt><span class="section"><a href="ch07s02.html#id2673480">V4L2 spec erratum 2004-08-01</a></span></dt><dt><span class="section"><a href="ch07s02.html#id2673559">V4L2 in Linux 2.6.14</a></span></dt><dt><span class="section"><a href="ch07s02.html#id2673599">V4L2 in Linux 2.6.15</a></span></dt><dt><span class="section"><a href="ch07s02.html#id2673710">V4L2 spec erratum 2005-11-27</a></span></dt><dt><span class="section"><a href="ch07s02.html#id2673750">V4L2 spec erratum 2006-01-10</a></span></dt><dt><span class="section"><a href="ch07s02.html#id2673800">V4L2 spec erratum 2006-02-03</a></span></dt><dt><span class="section"><a href="ch07s02.html#id2673842">V4L2 spec erratum 2006-02-04</a></span></dt><dt><span class="section"><a href="ch07s02.html#id2673890">V4L2 in Linux 2.6.17</a></span></dt><dt><span class="section"><a href="ch07s02.html#id2673969">V4L2 spec erratum 2006-09-23 (Draft 0.15)</a></span></dt><dt><span class="section"><a href="ch07s02.html#id2674140">V4L2 in Linux 2.6.18</a></span></dt><dt><span class="section"><a href="ch07s02.html#id2674234">V4L2 in Linux 2.6.19</a></span></dt><dt><span class="section"><a href="ch07s02.html#id2674320">V4L2 spec erratum 2006-10-12 (Draft 0.17)</a></span></dt><dt><span class="section"><a href="ch07s02.html#id2674351">V4L2 in Linux 2.6.21</a></span></dt><dt><span class="section"><a href="ch07s02.html#id2674381">V4L2 in Linux 2.6.22</a></span></dt><dt><span class="section"><a href="ch07s02.html#id2674505">V4L2 in Linux 2.6.24</a></span></dt><dt><span class="section"><a href="ch07s02.html#id2674545">V4L2 in Linux 2.6.25</a></span></dt><dt><span class="section"><a href="ch07s02.html#id2674723">V4L2 in Linux 2.6.26</a></span></dt><dt><span class="section"><a href="ch07s02.html#id2674767">V4L2 in Linux 2.6.27</a></span></dt><dt><span class="section"><a href="ch07s02.html#id2674836">V4L2 in Linux 2.6.28</a></span></dt><dt><span class="section"><a href="ch07s02.html#id2674894">V4L2 in Linux 2.6.29</a></span></dt><dt><span class="section"><a href="ch07s02.html#id2674986">V4L2 in Linux 2.6.30</a></span></dt><dt><span class="section"><a href="ch07s02.html#id2675021">V4L2 in Linux 2.6.32</a></span></dt></dl></dd><dt><span class="section"><a href="ch07s03.html">Relation of V4L2 to other Linux multimedia APIs</a></span></dt><dd><dl><dt><span class="section"><a href="ch07s03.html#xvideo">X Video Extension</a></span></dt><dt><span class="section"><a href="ch07s03.html#id2675221">Digital Video</a></span></dt><dt><span class="section"><a href="ch07s03.html#id2675242">Audio Interfaces</a></span></dt></dl></dd><dt><span class="section"><a href="ch07s04.html">Experimental API Elements</a></span></dt><dt><span class="section"><a href="ch07s05.html">Obsolete API Elements</a></span></dt></dl></div><p>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.</p><div class="section" title="Differences between V4L and V4L2"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="diff-v4l"></a>Differences between V4L and V4L2</h2></div></div></div><div class="toc"><dl><dt><span class="section"><a href="ch07.html#id2665771">Opening and Closing Devices</a></span></dt><dt><span class="section"><a href="ch07.html#id2667495">Querying Capabilities</a></span></dt><dt><span class="section"><a href="ch07.html#id2668054">Video Sources</a></span></dt><dt><span class="section"><a href="ch07.html#id2668280">Tuning</a></span></dt><dt><span class="section"><a href="ch07.html#v4l-image-properties">Image Properties</a></span></dt><dt><span class="section"><a href="ch07.html#id2669086">Audio</a></span></dt><dt><span class="section"><a href="ch07.html#id2669409">Frame Buffer Overlay</a></span></dt><dt><span class="section"><a href="ch07.html#id2669683">Cropping</a></span></dt><dt><span class="section"><a href="ch07.html#id2669828">Reading Images, Memory Mapping</a></span></dt><dt><span class="section"><a href="ch07.html#id2670176">Reading Raw VBI Data</a></span></dt><dt><span class="section"><a href="ch07.html#id2670390">Miscellaneous</a></span></dt></dl></div><p>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 <code class="filename">videodev</code> kernel module translating ioctls on
the fly. For a transition period not all drivers will support the V4L2
API.</p><div class="section" title="Opening and Closing Devices"><div class="titlepage"><div><div><h3 class="title"><a id="id2665771"></a>Opening and Closing Devices</h3></div></div></div><p>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 <a class="xref" href="ch04.html" title="Chapter 4. Interfaces">Chapter 4, <i>Interfaces</i></a> and below in <a class="xref" href="ch07.html#v4l-dev" title="Table 7.1. V4L Device Types, Names and Numbers">Table 7.1, “V4L Device Types, Names and Numbers”</a>.</p><p>The V4L <code class="filename">videodev</code> 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.</p><div class="table"><a id="v4l-dev"></a><p class="title"><b>Table 7.1. V4L Device Types, Names and Numbers</b></p><div class="table-contents"><table summary="V4L Device Types, Names and Numbers" border="1"><colgroup><col /><col /><col /></colgroup><thead><tr><th>Device Type</th><th>File Name</th><th>Minor Numbers</th></tr></thead><tbody valign="top"><tr><td valign="top">Video capture and overlay</td><td valign="top"><p><code class="filename">/dev/video</code> and
<code class="filename">/dev/bttv0</code><sup>[<a id="id2667308" href="#ftn.id2667308" class="footnote">a</a>]</sup>,
<code class="filename">/dev/video0</code> to
<code class="filename">/dev/video63</code></p></td><td valign="top">0-63</td></tr><tr><td valign="top">Radio receiver</td><td valign="top"><p><code class="filename">/dev/radio</code><sup>[<a id="id2667356" href="#ftn.id2667356" class="footnote">b</a>]</sup>, <code class="filename">/dev/radio0</code> to
<code class="filename">/dev/radio63</code></p></td><td valign="top">64-127</td></tr><tr><td valign="top">Teletext decoder</td><td valign="top"><p><code class="filename">/dev/vtx</code>,
<code class="filename">/dev/vtx0</code> to
<code class="filename">/dev/vtx31</code></p></td><td valign="top">192-223</td></tr><tr><td valign="top">Raw VBI capture</td><td valign="top"><p><code class="filename">/dev/vbi</code>,
<code class="filename">/dev/vbi0</code> to
<code class="filename">/dev/vbi31</code></p></td><td valign="top">224-255</td></tr></tbody><tbody class="footnotes"><tr><td colspan="3"><div class="footnote"><p><sup>[<a id="ftn.id2667308" href="#id2667308" class="para">a</a>] </sup>According to
Documentation/devices.txt these should be symbolic links to
<code class="filename">/dev/video0</code>. Note the original bttv interface is
not compatible with V4L or V4L2.</p></div><div class="footnote"><p><sup>[<a id="ftn.id2667356" href="#id2667356" class="para">b</a>] </sup>According to
<code class="filename">Documentation/devices.txt</code> a symbolic link to
<code class="filename">/dev/radio0</code>.</p></div></td></tr></tbody></table></div></div><br class="table-break" /><p>V4L prohibits (or used to prohibit) multiple opens of a
device file. V4L2 drivers <span class="emphasis"><em>may</em></span> support multiple
opens, see <a class="xref" href="ch01.html#open" title="Opening and Closing Devices">the section called “Opening and Closing Devices”</a> for details and consequences.</p><p>V4L drivers respond to V4L2 ioctls with an <span class="errorcode">EINVAL</span> error code. The
compatibility layer in the V4L2 <code class="filename">videodev</code> 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 <a class="xref" href="ch05.html" title="Chapter 5. V4L2 Driver Programming">Chapter 5, <i>V4L2 Driver Programming</i></a>.</p></div><div class="section" title="Querying Capabilities"><div class="titlepage"><div><div><h3 class="title"><a id="id2667495"></a>Querying Capabilities</h3></div></div></div><p>The V4L <code class="constant">VIDIOCGCAP</code> ioctl is
equivalent to V4L2's <a class="link" href="re56.html" title="ioctl VIDIOC_QUERYCAP"><code class="constant">VIDIOC_QUERYCAP</code></a>.</p><p>The <em class="structfield"><code>name</code></em> field in struct
<span class="structname">video_capability</span> became
<em class="structfield"><code>card</code></em> in struct <a class="link" href="re56.html#v4l2-capability" title="Table A.66. struct v4l2_capability">v4l2_capability</a>,
<em class="structfield"><code>type</code></em> was replaced by
<em class="structfield"><code>capabilities</code></em>. 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 <a class="xref" href="ch01.html#open" title="Opening and Closing Devices">the section called “Opening and Closing Devices”</a> for an
introduction.</p><div class="informaltable"><table border="1"><colgroup><col /><col /><col /></colgroup><thead><tr><th>struct
<span class="structname">video_capability</span>
<em class="structfield"><code>type</code></em></th><th>struct <a class="link" href="re56.html#v4l2-capability" title="Table A.66. struct v4l2_capability">v4l2_capability</a>
<em class="structfield"><code>capabilities</code></em> flags</th><th>Purpose</th></tr></thead><tbody valign="top"><tr><td valign="top"><code class="constant">VID_TYPE_CAPTURE</code></td><td valign="top"><code class="constant">V4L2_CAP_VIDEO_CAPTURE</code></td><td valign="top">The <a class="link" href="ch04.html#capture" title="Video Capture Interface">video
capture</a> interface is supported.</td></tr><tr><td valign="top"><code class="constant">VID_TYPE_TUNER</code></td><td valign="top"><code class="constant">V4L2_CAP_TUNER</code></td><td valign="top">The device has a <a class="link" href="ch01s06.html" title="Tuners and Modulators">tuner or
modulator</a>.</td></tr><tr><td valign="top"><code class="constant">VID_TYPE_TELETEXT</code></td><td valign="top"><code class="constant">V4L2_CAP_VBI_CAPTURE</code></td><td valign="top">The <a class="link" href="ch04s07.html" title="Raw VBI Data Interface">raw VBI
capture</a> interface is supported.</td></tr><tr><td valign="top"><code class="constant">VID_TYPE_OVERLAY</code></td><td valign="top"><code class="constant">V4L2_CAP_VIDEO_OVERLAY</code></td><td valign="top">The <a class="link" href="ch04s02.html" title="Video Overlay Interface">video
overlay</a> interface is supported.</td></tr><tr><td valign="top"><code class="constant">VID_TYPE_CHROMAKEY</code></td><td valign="top"><code class="constant">V4L2_FBUF_CAP_CHROMAKEY</code> in
field <em class="structfield"><code>capability</code></em> of
struct <a class="link" href="re40.html#v4l2-framebuffer" title="Table A.43. struct v4l2_framebuffer">v4l2_framebuffer</a></td><td valign="top">Whether chromakey overlay is supported. For
more information on overlay see
<a class="xref" href="ch04s02.html" title="Video Overlay Interface">the section called “Video Overlay Interface”</a>.</td></tr><tr><td valign="top"><code class="constant">VID_TYPE_CLIPPING</code></td><td valign="top"><code class="constant">V4L2_FBUF_CAP_LIST_CLIPPING</code>
and <code class="constant">V4L2_FBUF_CAP_BITMAP_CLIPPING</code> in field
<em class="structfield"><code>capability</code></em> of struct <a class="link" href="re40.html#v4l2-framebuffer" title="Table A.43. struct v4l2_framebuffer">v4l2_framebuffer</a></td><td valign="top">Whether clipping the overlaid image is
supported, see <a class="xref" href="ch04s02.html" title="Video Overlay Interface">the section called “Video Overlay Interface”</a>.</td></tr><tr><td valign="top"><code class="constant">VID_TYPE_FRAMERAM</code></td><td valign="top"><code class="constant">V4L2_FBUF_CAP_EXTERNOVERLAY</code>
<span class="emphasis"><em>not set</em></span> in field
<em class="structfield"><code>capability</code></em> of struct <a class="link" href="re40.html#v4l2-framebuffer" title="Table A.43. struct v4l2_framebuffer">v4l2_framebuffer</a></td><td valign="top">Whether overlay overwrites frame buffer memory,
see <a class="xref" href="ch04s02.html" title="Video Overlay Interface">the section called “Video Overlay Interface”</a>.</td></tr><tr><td valign="top"><code class="constant">VID_TYPE_SCALES</code></td><td valign="top"><code class="constant">-</code></td><td valign="top">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 <a class="link" href="re36.html" title="ioctl VIDIOC_G_CROP, VIDIOC_S_CROP"><code class="constant">VIDIOC_S_CROP</code></a> and <a class="link" href="re41.html" title="ioctl VIDIOC_G_FMT, VIDIOC_S_FMT, VIDIOC_TRY_FMT"><code class="constant">VIDIOC_S_FMT</code></a>
ioctl, respectively. The driver returns the closest sizes possible.
For more information on cropping and scaling see <a class="xref" href="ch01s11.html" title="Image Cropping, Insertion and Scaling">the section called “Image Cropping, Insertion and Scaling”</a>.</td></tr><tr><td valign="top"><code class="constant">VID_TYPE_MONOCHROME</code></td><td valign="top"><code class="constant">-</code></td><td valign="top">Applications can enumerate the supported image
formats with the <a class="link" href="re28.html" title="ioctl VIDIOC_ENUM_FMT"><code class="constant">VIDIOC_ENUM_FMT</code></a> ioctl to determine if the device
supports grey scale capturing only. For more information on image
formats see <a class="xref" href="ch02.html" title="Chapter 2. Image Formats">Chapter 2, <i>Image Formats</i></a>.</td></tr><tr><td valign="top"><code class="constant">VID_TYPE_SUBCAPTURE</code></td><td valign="top"><code class="constant">-</code></td><td valign="top">Applications can call the <a class="link" href="re36.html" title="ioctl VIDIOC_G_CROP, VIDIOC_S_CROP"><code class="constant">VIDIOC_G_CROP</code></a> ioctl
to determine if the device supports capturing a subsection of the full
picture ("cropping" in V4L2). If not, the ioctl returns the <span class="errorcode">EINVAL</span> error code.
For more information on cropping and scaling see <a class="xref" href="ch01s11.html" title="Image Cropping, Insertion and Scaling">the section called “Image Cropping, Insertion and Scaling”</a>.</td></tr><tr><td valign="top"><code class="constant">VID_TYPE_MPEG_DECODER</code></td><td valign="top"><code class="constant">-</code></td><td valign="top">Applications can enumerate the supported image
formats with the <a class="link" href="re28.html" title="ioctl VIDIOC_ENUM_FMT"><code class="constant">VIDIOC_ENUM_FMT</code></a> ioctl to determine if the device
supports MPEG streams.</td></tr><tr><td valign="top"><code class="constant">VID_TYPE_MPEG_ENCODER</code></td><td valign="top"><code class="constant">-</code></td><td valign="top">See above.</td></tr><tr><td valign="top"><code class="constant">VID_TYPE_MJPEG_DECODER</code></td><td valign="top"><code class="constant">-</code></td><td valign="top">See above.</td></tr><tr><td valign="top"><code class="constant">VID_TYPE_MJPEG_ENCODER</code></td><td valign="top"><code class="constant">-</code></td><td valign="top">See above.</td></tr></tbody></table></div><p>The <em class="structfield"><code>audios</code></em> field was replaced
by <em class="structfield"><code>capabilities</code></em> flag
<code class="constant">V4L2_CAP_AUDIO</code>, indicating
<span class="emphasis"><em>if</em></span> the device has any audio inputs or outputs. To
determine their number applications can enumerate audio inputs with
the <a class="link" href="re34.html" title="ioctl VIDIOC_G_AUDIO, VIDIOC_S_AUDIO"><code class="constant">VIDIOC_G_AUDIO</code></a> ioctl. The audio ioctls are described in <a class="xref" href="ch01s05.html" title="Audio Inputs and Outputs">the section called “Audio Inputs and Outputs”</a>.</p><p>The <em class="structfield"><code>maxwidth</code></em>,
<em class="structfield"><code>maxheight</code></em>,
<em class="structfield"><code>minwidth</code></em> and
<em class="structfield"><code>minheight</code></em> fields were removed. Calling the
<a class="link" href="re41.html" title="ioctl VIDIOC_G_FMT, VIDIOC_S_FMT, VIDIOC_TRY_FMT"><code class="constant">VIDIOC_S_FMT</code></a> or <a class="link" href="re41.html" title="ioctl VIDIOC_G_FMT, VIDIOC_S_FMT, VIDIOC_TRY_FMT"><code class="constant">VIDIOC_TRY_FMT</code></a> ioctl with the desired dimensions
returns the closest size possible, taking into account the current
video standard, cropping and scaling limitations.</p></div><div class="section" title="Video Sources"><div class="titlepage"><div><div><h3 class="title"><a id="id2668054"></a>Video Sources</h3></div></div></div><p>V4L provides the <code class="constant">VIDIOCGCHAN</code> and
<code class="constant">VIDIOCSCHAN</code> ioctl using struct
<span class="structname">video_channel</span> to enumerate
the video inputs of a V4L device. The equivalent V4L2 ioctls
are <a class="link" href="re31.html" title="ioctl VIDIOC_ENUMINPUT"><code class="constant">VIDIOC_ENUMINPUT</code></a>, <a class="link" href="re43.html" title="ioctl VIDIOC_G_INPUT, VIDIOC_S_INPUT"><code class="constant">VIDIOC_G_INPUT</code></a> and <a class="link" href="re43.html" title="ioctl VIDIOC_G_INPUT, VIDIOC_S_INPUT"><code class="constant">VIDIOC_S_INPUT</code></a>
using struct <a class="link" href="re31.html#v4l2-input" title="Table A.22. struct v4l2_input">v4l2_input</a> as discussed in <a class="xref" href="ch01s04.html" title="Video Inputs and Outputs">the section called “Video Inputs and Outputs”</a>.</p><p>The <em class="structfield"><code>channel</code></em> field counting
inputs was renamed to <em class="structfield"><code>index</code></em>, the video
input types were renamed as follows: </p><div class="informaltable"><table border="1"><colgroup><col /><col /></colgroup><thead><tr><th>struct <span class="structname">video_channel</span>
<em class="structfield"><code>type</code></em></th><th>struct <a class="link" href="re31.html#v4l2-input" title="Table A.22. struct v4l2_input">v4l2_input</a>
<em class="structfield"><code>type</code></em></th></tr></thead><tbody valign="top"><tr><td valign="top"><code class="constant">VIDEO_TYPE_TV</code></td><td valign="top"><code class="constant">V4L2_INPUT_TYPE_TUNER</code></td></tr><tr><td valign="top"><code class="constant">VIDEO_TYPE_CAMERA</code></td><td valign="top"><code class="constant">V4L2_INPUT_TYPE_CAMERA</code></td></tr></tbody></table></div><p>Unlike the <em class="structfield"><code>tuners</code></em> 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, i. e. 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 <em class="structfield"><code>tuner</code></em> of
struct <a class="link" href="re31.html#v4l2-input" title="Table A.22. struct v4l2_input">v4l2_input</a>. Enumeration of tuners is discussed in <a class="xref" href="ch01s06.html" title="Tuners and Modulators">the section called “Tuners and Modulators”</a>.</p><p>The redundant <code class="constant">VIDEO_VC_TUNER</code> flag was
dropped. Video inputs associated with a tuner are of type
<code class="constant">V4L2_INPUT_TYPE_TUNER</code>. The
<code class="constant">VIDEO_VC_AUDIO</code> flag was replaced by the
<em class="structfield"><code>audioset</code></em> field. V4L2 considers devices with
up to 32 audio inputs. Each set bit in the
<em class="structfield"><code>audioset</code></em> field represents one audio input
this video input combines with. For information about audio inputs and
how to switch between them see <a class="xref" href="ch01s05.html" title="Audio Inputs and Outputs">the section called “Audio Inputs and Outputs”</a>.</p><p>The <em class="structfield"><code>norm</code></em> field describing the
supported video standards was replaced by
<em class="structfield"><code>std</code></em>. The V4L specification mentions a flag
<code class="constant">VIDEO_VC_NORM</code> indicating whether the standard can
be changed. This flag was a later addition together with the
<em class="structfield"><code>norm</code></em> field and has been removed in the
meantime. V4L2 has a similar, albeit more comprehensive approach
to video standards, see <a class="xref" href="ch01s07.html" title="Video Standards">the section called “Video Standards”</a> for more
information.</p></div><div class="section" title="Tuning"><div class="titlepage"><div><div><h3 class="title"><a id="id2668280"></a>Tuning</h3></div></div></div><p>The V4L <code class="constant">VIDIOCGTUNER</code> and
<code class="constant">VIDIOCSTUNER</code> ioctl and struct
<span class="structname">video_tuner</span> can be used to enumerate the
tuners of a V4L TV or radio device. The equivalent V4L2 ioctls are
<a class="link" href="re51.html" title="ioctl VIDIOC_G_TUNER, VIDIOC_S_TUNER"><code class="constant">VIDIOC_G_TUNER</code></a> and <a class="link" href="re51.html" title="ioctl VIDIOC_G_TUNER, VIDIOC_S_TUNER"><code class="constant">VIDIOC_S_TUNER</code></a> using struct <a class="link" href="re51.html#v4l2-tuner" title="Table A.60. struct v4l2_tuner">v4l2_tuner</a>. Tuners are
covered in <a class="xref" href="ch01s06.html" title="Tuners and Modulators">the section called “Tuners and Modulators”</a>.</p><p>The <em class="structfield"><code>tuner</code></em> field counting tuners
was renamed to <em class="structfield"><code>index</code></em>. The fields
<em class="structfield"><code>name</code></em>, <em class="structfield"><code>rangelow</code></em>
and <em class="structfield"><code>rangehigh</code></em> remained unchanged.</p><p>The <code class="constant">VIDEO_TUNER_PAL</code>,
<code class="constant">VIDEO_TUNER_NTSC</code> and
<code class="constant">VIDEO_TUNER_SECAM</code> flags indicating the supported
video standards were dropped. This information is now contained in the
associated struct <a class="link" href="re31.html#v4l2-input" title="Table A.22. struct v4l2_input">v4l2_input</a>. No replacement exists for the
<code class="constant">VIDEO_TUNER_NORM</code> flag indicating whether the
video standard can be switched. The <em class="structfield"><code>mode</code></em>
field to select a different video standard was replaced by a whole new
set of ioctls and structures described in <a class="xref" href="ch01s07.html" title="Video Standards">the section called “Video Standards”</a>.
Due to its ubiquity it should be mentioned the BTTV driver supports
several standards in addition to the regular
<code class="constant">VIDEO_MODE_PAL</code> (0),
<code class="constant">VIDEO_MODE_NTSC</code>,
<code class="constant">VIDEO_MODE_SECAM</code> and
<code class="constant">VIDEO_MODE_AUTO</code> (3). Namely N/PAL Argentina,
M/PAL, N/PAL, and NTSC Japan with numbers 3-6 (sic).</p><p>The <code class="constant">VIDEO_TUNER_STEREO_ON</code> flag
indicating stereo reception became
<code class="constant">V4L2_TUNER_SUB_STEREO</code> in field
<em class="structfield"><code>rxsubchans</code></em>. This field also permits the
detection of monaural and bilingual audio, see the definition of
struct <a class="link" href="re51.html#v4l2-tuner" title="Table A.60. struct v4l2_tuner">v4l2_tuner</a> for details. Presently no replacement exists for the
<code class="constant">VIDEO_TUNER_RDS_ON</code> and
<code class="constant">VIDEO_TUNER_MBS_ON</code> flags.</p><p> The <code class="constant">VIDEO_TUNER_LOW</code> flag was renamed
to <code class="constant">V4L2_TUNER_CAP_LOW</code> in the struct <a class="link" href="re51.html#v4l2-tuner" title="Table A.60. struct v4l2_tuner">v4l2_tuner</a>
<em class="structfield"><code>capability</code></em> field.</p><p>The <code class="constant">VIDIOCGFREQ</code> and
<code class="constant">VIDIOCSFREQ</code> ioctl to change the tuner frequency
where renamed to <a class="link" href="re42.html" title="ioctl VIDIOC_G_FREQUENCY, VIDIOC_S_FREQUENCY"><code class="constant">VIDIOC_G_FREQUENCY</code></a> and <a class="link" href="re42.html" title="ioctl VIDIOC_G_FREQUENCY, VIDIOC_S_FREQUENCY"><code class="constant">VIDIOC_S_FREQUENCY</code></a>. They
take a pointer to a struct <a class="link" href="re42.html#v4l2-frequency" title="Table A.47. struct v4l2_frequency">v4l2_frequency</a> instead of an unsigned long
integer.</p></div><div class="section" title="Image Properties"><div class="titlepage"><div><div><h3 class="title"><a id="v4l-image-properties"></a>Image Properties</h3></div></div></div><p>V4L2 has no equivalent of the
<code class="constant">VIDIOCGPICT</code> and <code class="constant">VIDIOCSPICT</code>
ioctl and struct <span class="structname">video_picture</span>. The following
fields where replaced by V4L2 controls accessible with the
<a class="link" href="re57.html" title="ioctl VIDIOC_QUERYCTRL, VIDIOC_QUERYMENU"><code class="constant">VIDIOC_QUERYCTRL</code></a>, <a class="link" href="re37.html" title="ioctl VIDIOC_G_CTRL, VIDIOC_S_CTRL"><code class="constant">VIDIOC_G_CTRL</code></a> and <a class="link" href="re37.html" title="ioctl VIDIOC_G_CTRL, VIDIOC_S_CTRL"><code class="constant">VIDIOC_S_CTRL</code></a> ioctls:</p><div class="informaltable"><table border="1"><colgroup><col /><col /></colgroup><thead><tr><th>struct <span class="structname">video_picture</span></th><th>V4L2 Control ID</th></tr></thead><tbody valign="top"><tr><td valign="top"><em class="structfield"><code>brightness</code></em></td><td valign="top"><code class="constant">V4L2_CID_BRIGHTNESS</code></td></tr><tr><td valign="top"><em class="structfield"><code>hue</code></em></td><td valign="top"><code class="constant">V4L2_CID_HUE</code></td></tr><tr><td valign="top"><em class="structfield"><code>colour</code></em></td><td valign="top"><code class="constant">V4L2_CID_SATURATION</code></td></tr><tr><td valign="top"><em class="structfield"><code>contrast</code></em></td><td valign="top"><code class="constant">V4L2_CID_CONTRAST</code></td></tr><tr><td valign="top"><em class="structfield"><code>whiteness</code></em></td><td valign="top"><code class="constant">V4L2_CID_WHITENESS</code></td></tr></tbody></table></div><p>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 <a class="link" href="re57.html" title="ioctl VIDIOC_QUERYCTRL, VIDIOC_QUERYMENU"><code class="constant">VIDIOC_QUERYCTRL</code></a>
ioctl. For general information about controls see <a class="xref" href="ch01s08.html" title="User Controls">the section called “User Controls”</a>.</p><p>The <em class="structfield"><code>depth</code></em> (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 <em class="structfield"><code>palette</code></em> field
moved into the struct <a class="link" href="ch02.html#v4l2-pix-format" title="Table 2.1. struct v4l2_pix_format">v4l2_pix_format</a>:</p><div class="informaltable"><table border="1"><colgroup><col /><col /></colgroup><thead><tr><th>struct <span class="structname">video_picture</span>
<em class="structfield"><code>palette</code></em></th><th>struct <a class="link" href="ch02.html#v4l2-pix-format" title="Table 2.1. struct v4l2_pix_format">v4l2_pix_format</a>
<em class="structfield"><code>pixfmt</code></em></th></tr></thead><tbody valign="top"><tr><td valign="top"><code class="constant">VIDEO_PALETTE_GREY</code></td><td valign="top"><p><a class="link" href="re07.html" title="V4L2_PIX_FMT_GREY ('GREY')"><code class="constant">V4L2_PIX_FMT_GREY</code></a></p></td></tr><tr><td valign="top"><code class="constant">VIDEO_PALETTE_HI240</code></td><td valign="top"><p><a class="link" href="ch02s07.html" title="Reserved Format Identifiers"><code class="constant">V4L2_PIX_FMT_HI240</code></a><sup>[<a id="id2668755" href="#ftn.id2668755" class="footnote">a</a>]</sup></p></td></tr><tr><td valign="top"><code class="constant">VIDEO_PALETTE_RGB565</code></td><td valign="top"><p><a class="link" href="ch02s04.html" title="RGB Formats"><code class="constant">V4L2_PIX_FMT_RGB565</code></a></p></td></tr><tr><td valign="top"><code class="constant">VIDEO_PALETTE_RGB555</code></td><td valign="top"><p><a class="link" href="ch02s04.html" title="RGB Formats"><code class="constant">V4L2_PIX_FMT_RGB555</code></a></p></td></tr><tr><td valign="top"><code class="constant">VIDEO_PALETTE_RGB24</code></td><td valign="top"><p><a class="link" href="ch02s04.html" title="RGB Formats"><code class="constant">V4L2_PIX_FMT_BGR24</code></a></p></td></tr><tr><td valign="top"><code class="constant">VIDEO_PALETTE_RGB32</code></td><td valign="top"><p><a class="link" href="ch02s04.html" title="RGB Formats"><code class="constant">V4L2_PIX_FMT_BGR32</code></a><sup>[<a id="id2668835" href="#ftn.id2668835" class="footnote">b</a>]</sup></p></td></tr><tr><td valign="top"><code class="constant">VIDEO_PALETTE_YUV422</code></td><td valign="top"><p><a class="link" href="re09.html" title="V4L2_PIX_FMT_YUYV ('YUYV')"><code class="constant">V4L2_PIX_FMT_YUYV</code></a></p></td></tr><tr><td valign="top"><p><code class="constant">VIDEO_PALETTE_YUYV</code><sup>[<a id="id2668876" href="#ftn.id2668876" class="footnote">c</a>]</sup></p></td><td valign="top"><p><a class="link" href="re09.html" title="V4L2_PIX_FMT_YUYV ('YUYV')"><code class="constant">V4L2_PIX_FMT_YUYV</code></a></p></td></tr><tr><td valign="top"><code class="constant">VIDEO_PALETTE_UYVY</code></td><td valign="top"><p><a class="link" href="re10.html" title="V4L2_PIX_FMT_UYVY ('UYVY')"><code class="constant">V4L2_PIX_FMT_UYVY</code></a></p></td></tr><tr><td valign="top"><code class="constant">VIDEO_PALETTE_YUV420</code></td><td valign="top">None</td></tr><tr><td valign="top"><code class="constant">VIDEO_PALETTE_YUV411</code></td><td valign="top"><p><a class="link" href="re13.html" title="V4L2_PIX_FMT_Y41P ('Y41P')"><code class="constant">V4L2_PIX_FMT_Y41P</code></a><sup>[<a id="id2668948" href="#ftn.id2668948" class="footnote">d</a>]</sup></p></td></tr><tr><td valign="top"><code class="constant">VIDEO_PALETTE_RAW</code></td><td valign="top"><p>None<sup>[<a id="id2668971" href="#ftn.id2668971" class="footnote">e</a>]</sup></p></td></tr><tr><td valign="top"><code class="constant">VIDEO_PALETTE_YUV422P</code></td><td valign="top"><p><a class="link" href="re16.html" title="V4L2_PIX_FMT_YUV422P ('422P')"><code class="constant">V4L2_PIX_FMT_YUV422P</code></a></p></td></tr><tr><td valign="top"><code class="constant">VIDEO_PALETTE_YUV411P</code></td><td valign="top"><p><a class="link" href="re17.html" title="V4L2_PIX_FMT_YUV411P ('411P')"><code class="constant">V4L2_PIX_FMT_YUV411P</code></a><sup>[<a id="id2669015" href="#ftn.id2669015" class="footnote">f</a>]</sup></p></td></tr><tr><td valign="top"><code class="constant">VIDEO_PALETTE_YUV420P</code></td><td valign="top"><p><a class="link" href="re14.html#V4L2-PIX-FMT-YVU420"><code class="constant">V4L2_PIX_FMT_YVU420</code></a></p></td></tr><tr><td valign="top"><code class="constant">VIDEO_PALETTE_YUV410P</code></td><td valign="top"><p><a class="link" href="re15.html#V4L2-PIX-FMT-YVU410"><code class="constant">V4L2_PIX_FMT_YVU410</code></a></p></td></tr></tbody><tbody class="footnotes"><tr><td colspan="2"><div class="footnote"><p><sup>[<a id="ftn.id2668755" href="#id2668755" class="para">a</a>] </sup>This is a custom format used by the BTTV
driver, not one of the V4L2 standard formats.</p></div><div class="footnote"><p><sup>[<a id="ftn.id2668835" href="#id2668835" class="para">b</a>] </sup>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 <a class="xref" href="ch02s04.html" title="RGB Formats">the section called “RGB Formats”</a>.</p></div><div class="footnote"><p><sup>[<a id="ftn.id2668876" href="#id2668876" class="para">c</a>] </sup><code class="constant">VIDEO_PALETTE_YUV422</code>
and <code class="constant">VIDEO_PALETTE_YUYV</code> are the same formats. Some
V4L drivers respond to one, some to the other.</p></div><div class="footnote"><p><sup>[<a id="ftn.id2668948" href="#id2668948" class="para">d</a>] </sup>Not to be confused with
<code class="constant">V4L2_PIX_FMT_YUV411P</code>, which is a planar
format.</p></div><div class="footnote"><p><sup>[<a id="ftn.id2668971" href="#id2668971" class="para">e</a>] </sup>V4L explains this
as: "RAW capture (BT848)"</p></div><div class="footnote"><p><sup>[<a id="ftn.id2669015" href="#id2669015" class="para">f</a>] </sup>Not to be confused with
<code class="constant">V4L2_PIX_FMT_Y41P</code>, which is a packed
format.</p></div></td></tr></tbody></table></div><p>V4L2 image formats are defined in <a class="xref" href="ch02.html" title="Chapter 2. Image Formats">Chapter 2, <i>Image Formats</i></a>. The image format can be selected with the
<a class="link" href="re41.html" title="ioctl VIDIOC_G_FMT, VIDIOC_S_FMT, VIDIOC_TRY_FMT"><code class="constant">VIDIOC_S_FMT</code></a> ioctl.</p></div><div class="section" title="Audio"><div class="titlepage"><div><div><h3 class="title"><a id="id2669086"></a>Audio</h3></div></div></div><p>The <code class="constant">VIDIOCGAUDIO</code> and
<code class="constant">VIDIOCSAUDIO</code> ioctl and struct
<span class="structname">video_audio</span> are used to enumerate the
audio inputs of a V4L device. The equivalent V4L2 ioctls are
<a class="link" href="re34.html" title="ioctl VIDIOC_G_AUDIO, VIDIOC_S_AUDIO"><code class="constant">VIDIOC_G_AUDIO</code></a> and <a class="link" href="re34.html" title="ioctl VIDIOC_G_AUDIO, VIDIOC_S_AUDIO"><code class="constant">VIDIOC_S_AUDIO</code></a> using struct <a class="link" href="re34.html#v4l2-audio" title="Table A.31. struct v4l2_audio">v4l2_audio</a> as
discussed in <a class="xref" href="ch01s05.html" title="Audio Inputs and Outputs">the section called “Audio Inputs and Outputs”</a>.</p><p>The <em class="structfield"><code>audio</code></em> "channel number"
field counting audio inputs was renamed to
<em class="structfield"><code>index</code></em>.</p><p>On <code class="constant">VIDIOCSAUDIO</code> the
<em class="structfield"><code>mode</code></em> field selects <span class="emphasis"><em>one</em></span>
of the <code class="constant">VIDEO_SOUND_MONO</code>,
<code class="constant">VIDEO_SOUND_STEREO</code>,
<code class="constant">VIDEO_SOUND_LANG1</code> or
<code class="constant">VIDEO_SOUND_LANG2</code> audio demodulation modes. When
the current audio standard is BTSC
<code class="constant">VIDEO_SOUND_LANG2</code> refers to SAP and
<code class="constant">VIDEO_SOUND_LANG1</code> is meaningless. Also
undocumented in the V4L specification, there is no way to query the
selected mode. On <code class="constant">VIDIOCGAUDIO</code> the driver returns
the <span class="emphasis"><em>actually received</em></span> audio programmes in this
field. In the V4L2 API this information is stored in the struct <a class="link" href="re51.html#v4l2-tuner" title="Table A.60. struct v4l2_tuner">v4l2_tuner</a>
<em class="structfield"><code>rxsubchans</code></em> and
<em class="structfield"><code>audmode</code></em> fields, respectively. See <a class="xref" href="ch01s06.html" title="Tuners and Modulators">the section called “Tuners and Modulators”</a> for more information on tuners. Related to audio
modes struct <a class="link" href="re34.html#v4l2-audio" title="Table A.31. struct v4l2_audio">v4l2_audio</a> also reports if this is a mono or stereo
input, regardless if the source is a tuner.</p><p>The following fields where replaced by V4L2 controls
accessible with the <a class="link" href="re57.html" title="ioctl VIDIOC_QUERYCTRL, VIDIOC_QUERYMENU"><code class="constant">VIDIOC_QUERYCTRL</code></a>, <a class="link" href="re37.html" title="ioctl VIDIOC_G_CTRL, VIDIOC_S_CTRL"><code class="constant">VIDIOC_G_CTRL</code></a> and
<a class="link" href="re37.html" title="ioctl VIDIOC_G_CTRL, VIDIOC_S_CTRL"><code class="constant">VIDIOC_S_CTRL</code></a> ioctls:</p><div class="informaltable"><table border="1"><colgroup><col /><col /></colgroup><thead><tr><th>struct
<span class="structname">video_audio</span></th><th>V4L2 Control ID</th></tr></thead><tbody valign="top"><tr><td valign="top"><em class="structfield"><code>volume</code></em></td><td valign="top"><code class="constant">V4L2_CID_AUDIO_VOLUME</code></td></tr><tr><td valign="top"><em class="structfield"><code>bass</code></em></td><td valign="top"><code class="constant">V4L2_CID_AUDIO_BASS</code></td></tr><tr><td valign="top"><em class="structfield"><code>treble</code></em></td><td valign="top"><code class="constant">V4L2_CID_AUDIO_TREBLE</code></td></tr><tr><td valign="top"><em class="structfield"><code>balance</code></em></td><td valign="top"><code class="constant">V4L2_CID_AUDIO_BALANCE</code></td></tr></tbody></table></div><p>To determine which of these controls are supported by a
driver V4L provides the <em class="structfield"><code>flags</code></em>
<code class="constant">VIDEO_AUDIO_VOLUME</code>,
<code class="constant">VIDEO_AUDIO_BASS</code>,
<code class="constant">VIDEO_AUDIO_TREBLE</code> and
<code class="constant">VIDEO_AUDIO_BALANCE</code>. In the V4L2 API the
<a class="link" href="re57.html" title="ioctl VIDIOC_QUERYCTRL, VIDIOC_QUERYMENU"><code class="constant">VIDIOC_QUERYCTRL</code></a> ioctl reports if the respective control is
supported. Accordingly the <code class="constant">VIDEO_AUDIO_MUTABLE</code>
and <code class="constant">VIDEO_AUDIO_MUTE</code> flags where replaced by the
boolean <code class="constant">V4L2_CID_AUDIO_MUTE</code> control.</p><p>All V4L2 controls have a <em class="structfield"><code>step</code></em>
attribute replacing the struct <span class="structname">video_audio</span>
<em class="structfield"><code>step</code></em> 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 <a class="link" href="re57.html" title="ioctl VIDIOC_QUERYCTRL, VIDIOC_QUERYMENU"><code class="constant">VIDIOC_QUERYCTRL</code></a> ioctl. For general information about
controls see <a class="xref" href="ch01s08.html" title="User Controls">the section called “User Controls”</a>.</p></div><div class="section" title="Frame Buffer Overlay"><div class="titlepage"><div><div><h3 class="title"><a id="id2669409"></a>Frame Buffer Overlay</h3></div></div></div><p>The V4L2 ioctls equivalent to
<code class="constant">VIDIOCGFBUF</code> and <code class="constant">VIDIOCSFBUF</code>
are <a class="link" href="re40.html" title="ioctl VIDIOC_G_FBUF, VIDIOC_S_FBUF"><code class="constant">VIDIOC_G_FBUF</code></a> and <a class="link" href="re40.html" title="ioctl VIDIOC_G_FBUF, VIDIOC_S_FBUF"><code class="constant">VIDIOC_S_FBUF</code></a>. The
<em class="structfield"><code>base</code></em> field of struct
<span class="structname">video_buffer</span> remained unchanged, except V4L2
defines a flag to indicate non-destructive overlays instead of a
<code class="constant">NULL</code> pointer. All other fields moved into the
struct <a class="link" href="ch02.html#v4l2-pix-format" title="Table 2.1. struct v4l2_pix_format">v4l2_pix_format</a> <em class="structfield"><code>fmt</code></em> substructure of
struct <a class="link" href="re40.html#v4l2-framebuffer" title="Table A.43. struct v4l2_framebuffer">v4l2_framebuffer</a>. The <em class="structfield"><code>depth</code></em> field was
replaced by <em class="structfield"><code>pixelformat</code></em>. See <a class="xref" href="ch02s04.html" title="RGB Formats">the section called “RGB Formats”</a> for a list of RGB formats and their
respective color depths.</p><p>Instead of the special ioctls
<code class="constant">VIDIOCGWIN</code> and <code class="constant">VIDIOCSWIN</code>
V4L2 uses the general-purpose data format negotiation ioctls
<a class="link" href="re41.html" title="ioctl VIDIOC_G_FMT, VIDIOC_S_FMT, VIDIOC_TRY_FMT"><code class="constant">VIDIOC_G_FMT</code></a> and <a class="link" href="re41.html" title="ioctl VIDIOC_G_FMT, VIDIOC_S_FMT, VIDIOC_TRY_FMT"><code class="constant">VIDIOC_S_FMT</code></a>. They take a pointer to a
struct <a class="link" href="re41.html#v4l2-format" title="Table A.46. struct v4l2_format">v4l2_format</a> as argument. Here the <em class="structfield"><code>win</code></em>
member of the <em class="structfield"><code>fmt</code></em> union is used, a
struct <a class="link" href="ch04s02.html#v4l2-window" title="Table 4.1. struct v4l2_window">v4l2_window</a>.</p><p>The <em class="structfield"><code>x</code></em>,
<em class="structfield"><code>y</code></em>, <em class="structfield"><code>width</code></em> and
<em class="structfield"><code>height</code></em> fields of struct
<span class="structname">video_window</span> moved into struct <a class="link" href="ch04s02.html#v4l2-rect" title="Table 4.3. struct v4l2_rect">v4l2_rect</a>
substructure <em class="structfield"><code>w</code></em> of struct
<span class="structname">v4l2_window</span>. The
<em class="structfield"><code>chromakey</code></em>,
<em class="structfield"><code>clips</code></em>, and
<em class="structfield"><code>clipcount</code></em> fields remained unchanged. Struct
<span class="structname">video_clip</span> was renamed to struct <a class="link" href="ch04s02.html#v4l2-clip" title="Table 4.2. struct v4l2_clip">v4l2_clip</a>, also
containing a struct <span class="structname">v4l2_rect</span>, but the
semantics are still the same.</p><p>The <code class="constant">VIDEO_WINDOW_INTERLACE</code> flag was
dropped. Instead applications must set the
<em class="structfield"><code>field</code></em> field to
<code class="constant">V4L2_FIELD_ANY</code> or
<code class="constant">V4L2_FIELD_INTERLACED</code>. The
<code class="constant">VIDEO_WINDOW_CHROMAKEY</code> flag moved into
struct <a class="link" href="re40.html#v4l2-framebuffer" title="Table A.43. struct v4l2_framebuffer">v4l2_framebuffer</a>, under the new name
<code class="constant">V4L2_FBUF_FLAG_CHROMAKEY</code>.</p><p>In V4L, storing a bitmap pointer in
<em class="structfield"><code>clips</code></em> and setting
<em class="structfield"><code>clipcount</code></em> to
<code class="constant">VIDEO_CLIP_BITMAP</code> (-1) requests bitmap
clipping, using a fixed size bitmap of 1024 × 625 bits. Struct
<span class="structname">v4l2_window</span> has a separate
<em class="structfield"><code>bitmap</code></em> pointer field for this purpose and
the bitmap size is determined by <em class="structfield"><code>w.width</code></em> and
<em class="structfield"><code>w.height</code></em>.</p><p>The <code class="constant">VIDIOCCAPTURE</code> ioctl to enable or
disable overlay was renamed to <a class="link" href="re53.html" title="ioctl VIDIOC_OVERLAY"><code class="constant">VIDIOC_OVERLAY</code></a>.</p></div><div class="section" title="Cropping"><div class="titlepage"><div><div><h3 class="title"><a id="id2669683"></a>Cropping</h3></div></div></div><p>To capture only a subsection of the full picture V4L
defines the <code class="constant">VIDIOCGCAPTURE</code> and
<code class="constant">VIDIOCSCAPTURE</code> ioctls using struct
<span class="structname">video_capture</span>. The equivalent V4L2 ioctls are
<a class="link" href="re36.html" title="ioctl VIDIOC_G_CROP, VIDIOC_S_CROP"><code class="constant">VIDIOC_G_CROP</code></a> and <a class="link" href="re36.html" title="ioctl VIDIOC_G_CROP, VIDIOC_S_CROP"><code class="constant">VIDIOC_S_CROP</code></a> using struct <a class="link" href="re36.html#v4l2-crop" title="Table A.35. struct v4l2_crop">v4l2_crop</a>, and the related
<a class="link" href="re22.html" title="ioctl VIDIOC_CROPCAP"><code class="constant">VIDIOC_CROPCAP</code></a> ioctl. This is a rather complex matter, see
<a class="xref" href="ch01s11.html" title="Image Cropping, Insertion and Scaling">the section called “Image Cropping, Insertion and Scaling”</a> for details.</p><p>The <em class="structfield"><code>x</code></em>,
<em class="structfield"><code>y</code></em>, <em class="structfield"><code>width</code></em> and
<em class="structfield"><code>height</code></em> fields moved into struct <a class="link" href="ch04s02.html#v4l2-rect" title="Table 4.3. struct v4l2_rect">v4l2_rect</a>
substructure <em class="structfield"><code>c</code></em> of struct
<span class="structname">v4l2_crop</span>. The
<em class="structfield"><code>decimation</code></em> 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.</p><p>The <code class="constant">VIDEO_CAPTURE_ODD</code>
and <code class="constant">VIDEO_CAPTURE_EVEN</code> flags to capture only the
odd or even field, respectively, were replaced by
<code class="constant">V4L2_FIELD_TOP</code> and
<code class="constant">V4L2_FIELD_BOTTOM</code> in the field named
<em class="structfield"><code>field</code></em> of struct <a class="link" href="ch02.html#v4l2-pix-format" title="Table 2.1. struct v4l2_pix_format">v4l2_pix_format</a> and
struct <a class="link" href="ch04s02.html#v4l2-window" title="Table 4.1. struct v4l2_window">v4l2_window</a>. These structures are used to select a capture or
overlay format with the <a class="link" href="re41.html" title="ioctl VIDIOC_G_FMT, VIDIOC_S_FMT, VIDIOC_TRY_FMT"><code class="constant">VIDIOC_S_FMT</code></a> ioctl.</p></div><div class="section" title="Reading Images, Memory Mapping"><div class="titlepage"><div><div><h3 class="title"><a id="id2669828"></a>Reading Images, Memory Mapping</h3></div></div></div><div class="toc"><dl><dt><span class="section"><a href="ch07.html#id2669834">Capturing using the read method</a></span></dt><dt><span class="section"><a href="ch07.html#id2669945">Capturing using memory mapping</a></span></dt></dl></div><div class="section" title="Capturing using the read method"><div class="titlepage"><div><div><h4 class="title"><a id="id2669834"></a>Capturing using the read method</h4></div></div></div><p>There is no essential difference between reading images
from a V4L or V4L2 device using the <a class="link" href="re66.html" title="V4L2 read()"><code class="function">read()</code></a> function, however V4L2
drivers are not required to support this I/O method. Applications can
determine if the function is available with the <a class="link" href="re56.html" title="ioctl VIDIOC_QUERYCAP"><code class="constant">VIDIOC_QUERYCAP</code></a>
ioctl. All V4L2 devices exchanging data with applications must support
the <a class="link" href="re67.html" title="V4L2 select()"><code class="function">select()</code></a> and <a class="link" href="re65.html" title="V4L2 poll()"><code class="function">poll()</code></a> functions.</p><p>To select an image format and size, V4L provides the
<code class="constant">VIDIOCSPICT</code> and <code class="constant">VIDIOCSWIN</code>
ioctls. V4L2 uses the general-purpose data format negotiation ioctls
<a class="link" href="re41.html" title="ioctl VIDIOC_G_FMT, VIDIOC_S_FMT, VIDIOC_TRY_FMT"><code class="constant">VIDIOC_G_FMT</code></a> and <a class="link" href="re41.html" title="ioctl VIDIOC_G_FMT, VIDIOC_S_FMT, VIDIOC_TRY_FMT"><code class="constant">VIDIOC_S_FMT</code></a>. They take a pointer to a
struct <a class="link" href="re41.html#v4l2-format" title="Table A.46. struct v4l2_format">v4l2_format</a> as argument, here the struct <a class="link" href="ch02.html#v4l2-pix-format" title="Table 2.1. struct v4l2_pix_format">v4l2_pix_format</a> named
<em class="structfield"><code>pix</code></em> of its <em class="structfield"><code>fmt</code></em>
union is used.</p><p>For more information about the V4L2 read interface see
<a class="xref" href="ch03.html#rw" title="Read/Write">the section called “Read/Write”</a>.</p></div><div class="section" title="Capturing using memory mapping"><div class="titlepage"><div><div><h4 class="title"><a id="id2669945"></a>Capturing using memory mapping</h4></div></div></div><p>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.</p><div class="informaltable"><table border="1"><colgroup><col /><col /></colgroup><thead><tr><th>V4L</th><th>V4L2</th></tr></thead><tbody valign="top"><tr><td valign="top"> </td><td valign="top">The image format must be selected before
buffers are allocated, with the <a class="link" href="re41.html" title="ioctl VIDIOC_G_FMT, VIDIOC_S_FMT, VIDIOC_TRY_FMT"><code class="constant">VIDIOC_S_FMT</code></a> ioctl. When no format
is selected the driver may use the last, possibly by another
application requested format.</td></tr><tr><td valign="top"><p>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.</p></td><td valign="top"><p>The <a class="link" href="re59.html" title="ioctl VIDIOC_REQBUFS"><code class="constant">VIDIOC_REQBUFS</code></a> ioctl allocates the
desired number of buffers, this is a required step in the initialization
sequence.</p></td></tr><tr><td valign="top"><p>Drivers map all buffers as one contiguous
range of memory. The <code class="constant">VIDIOCGMBUF</code> 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 <a class="link" href="re62.html" title="V4L2 mmap()"><code class="function">mmap()</code></a>
function.</p></td><td valign="top"><p>Buffers are individually mapped. The
offset and size of each buffer can be determined with the
<a class="link" href="re55.html" title="ioctl VIDIOC_QUERYBUF"><code class="constant">VIDIOC_QUERYBUF</code></a> ioctl.</p></td></tr><tr><td valign="top"><p>The <code class="constant">VIDIOCMCAPTURE</code>
ioctl prepares a buffer for capturing. It also determines the image
format for this buffer. The ioctl returns immediately, eventually with
an <span class="errorcode">EAGAIN</span> error code 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.</p><p>The <code class="constant">VIDIOCSYNC</code> ioctl
suspends execution until a particular buffer has been
filled.</p></td><td valign="top"><p>Drivers maintain an incoming and outgoing
queue. <a class="link" href="re54.html" title="ioctl VIDIOC_QBUF, VIDIOC_DQBUF"><code class="constant">VIDIOC_QBUF</code></a> enqueues any empty buffer into the incoming
queue. Filled buffers are dequeued from the outgoing queue with the
<a class="link" href="re54.html" title="ioctl VIDIOC_QBUF, VIDIOC_DQBUF"><code class="constant">VIDIOC_DQBUF</code></a> ioctl. To wait until filled buffers become available this
function, <a class="link" href="re67.html" title="V4L2 select()"><code class="function">select()</code></a> or <a class="link" href="re65.html" title="V4L2 poll()"><code class="function">poll()</code></a> can be used. The
<a class="link" href="re61.html" title="ioctl VIDIOC_STREAMON, VIDIOC_STREAMOFF"><code class="constant">VIDIOC_STREAMON</code></a> ioctl must be called once after enqueuing one or
more buffers to start capturing. Its counterpart
<a class="link" href="re61.html" title="ioctl VIDIOC_STREAMON, VIDIOC_STREAMOFF"><code class="constant">VIDIOC_STREAMOFF</code></a> stops capturing and dequeues all buffers from both
queues. Applications can query the signal status, if known, with the
<a class="link" href="re31.html" title="ioctl VIDIOC_ENUMINPUT"><code class="constant">VIDIOC_ENUMINPUT</code></a> ioctl.</p></td></tr></tbody></table></div><p>For a more in-depth discussion of memory mapping and
examples, see <a class="xref" href="ch03s02.html" title="Streaming I/O (Memory Mapping)">the section called “Streaming I/O (Memory Mapping)”</a>.</p></div></div><div class="section" title="Reading Raw VBI Data"><div class="titlepage"><div><div><h3 class="title"><a id="id2670176"></a>Reading Raw VBI Data</h3></div></div></div><p>Originally the V4L API did not specify a raw VBI capture
interface, only the device file <code class="filename">/dev/vbi</code> 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:</p><div class="informaltable"><table border="1"><colgroup><col /><col /></colgroup><thead><tr><th>struct <a class="link" href="ch04s07.html#v4l2-vbi-format" title="Table 4.4. struct v4l2_vbi_format">v4l2_vbi_format</a></th><th>V4L, BTTV driver</th></tr></thead><tbody valign="top"><tr><td valign="top">sampling_rate</td><td valign="top">28636363 Hz NTSC (or any other 525-line
standard); 35468950 Hz PAL and SECAM (625-line standards)</td></tr><tr><td valign="top">offset</td><td valign="top">?</td></tr><tr><td valign="top">samples_per_line</td><td valign="top">2048</td></tr><tr><td valign="top">sample_format</td><td valign="top">V4L2_PIX_FMT_GREY. The last four bytes (a
machine endianess integer) contain a frame counter.</td></tr><tr><td valign="top">start[]</td><td valign="top">10, 273 NTSC; 22, 335 PAL and SECAM</td></tr><tr><td valign="top">count[]</td><td valign="top"><p>16, 16<sup>[<a id="id2670287" href="#ftn.id2670287" class="footnote">a</a>]</sup></p></td></tr><tr><td valign="top">flags</td><td valign="top">0</td></tr></tbody><tbody class="footnotes"><tr><td colspan="2"><div class="footnote"><p><sup>[<a id="ftn.id2670287" href="#id2670287" class="para">a</a>] </sup>Old driver
versions used different values, eventually the custom
<code class="constant">BTTV_VBISIZE</code> ioctl was added to query the
correct values.</p></div></td></tr></tbody></table></div><p>Undocumented in the V4L specification, in Linux 2.3 the
<code class="constant">VIDIOCGVBIFMT</code> and
<code class="constant">VIDIOCSVBIFMT</code> ioctls using struct
<span class="structname">vbi_format</span> were added to determine the VBI
image parameters. These ioctls are only partially compatible with the
V4L2 VBI interface specified in <a class="xref" href="ch04s07.html" title="Raw VBI Data Interface">the section called “Raw VBI Data Interface”</a>.</p><p>An <em class="structfield"><code>offset</code></em> field does not
exist, <em class="structfield"><code>sample_format</code></em> is supposed to be
<code class="constant">VIDEO_PALETTE_RAW</code>, equivalent to
<code class="constant">V4L2_PIX_FMT_GREY</code>. The remaining fields are
probably equivalent to struct <a class="link" href="ch04s07.html#v4l2-vbi-format" title="Table 4.4. struct v4l2_vbi_format">v4l2_vbi_format</a>.</p><p>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 <a class="link" href="re64.html" title="V4L2 open()"><code class="function">open()</code></a> and
<code class="constant">VIDIOCSVBIFMT</code> always returns an <span class="errorcode">EINVAL</span> error code if the
parameters are invalid.</p></div><div class="section" title="Miscellaneous"><div class="titlepage"><div><div><h3 class="title"><a id="id2670390"></a>Miscellaneous</h3></div></div></div><p>V4L2 has no equivalent of the
<code class="constant">VIDIOCGUNIT</code> 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
<a class="xref" href="ch01.html#open" title="Opening and Closing Devices">the section called “Opening and Closing Devices”</a>.</p><p>No replacement exists for <code class="constant">VIDIOCKEY</code>,
and the V4L functions for microcode programming. A new interface for
MPEG compression and playback devices is documented in <a class="xref" href="ch01s09.html" title="Extended Controls">the section called “Extended Controls”</a>.</p></div></div></div><div class="navfooter"><hr /><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="ch06.html">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="pt01.html">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="ch07s02.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top">Chapter 6. Libv4l Userspace Library </td><td width="20%" align="center"><a accesskey="h" href="index.html">Home</a></td><td width="40%" align="right" valign="top"> Changes of the V4L2 API</td></tr></table></div></body></html>
