<?xml version="1.0" encoding="ANSI_X3.4-1968" standalone="no"?> <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> <html xmlns="http://www.w3.org/1999/xhtml"><head><meta http-equiv="Content-Type" content="text/html; charset=ANSI_X3.4-1968" /><title>ioctl VIDIOC_G_ENC_INDEX</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="apa.html" title="Appendix A. Function Reference" /><link rel="prev" href="re37.html" title="ioctl VIDIOC_G_CTRL, VIDIOC_S_CTRL" /><link rel="next" href="re39.html" title="ioctl VIDIOC_G_EXT_CTRLS, VIDIOC_S_EXT_CTRLS, VIDIOC_TRY_EXT_CTRLS" /></head><body><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="3" align="center">ioctl VIDIOC_G_ENC_INDEX</th></tr><tr><td width="20%" align="left"><a accesskey="p" href="re37.html">Prev</a> </td><th width="60%" align="center">Appendix A. Function Reference</th><td width="20%" align="right"> <a accesskey="n" href="re39.html">Next</a></td></tr></table><hr /></div><div class="refentry" title="ioctl VIDIOC_G_ENC_INDEX"><a id="vidioc-g-enc-index"></a><div class="titlepage"></div><div class="refnamediv"><h2>Name</h2><p>VIDIOC_G_ENC_INDEX — Get meta data about a compressed video stream</p></div><div class="refsynopsisdiv" title="Synopsis"><h2>Synopsis</h2><div class="funcsynopsis"><table border="0" summary="Function synopsis" cellspacing="0" cellpadding="0" class="funcprototype-table"><tr><td><code class="funcdef">int <b class="fsfunc">ioctl</b>(</code></td><td>int <var class="pdparam">fd</var>, </td></tr><tr><td> </td><td>int <var class="pdparam">request</var>, </td></tr><tr><td> </td><td>struct v4l2_enc_idx *<var class="pdparam">argp</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer"> </div></div></div><div class="refsect1" title="Arguments"><a id="id2705685"></a><h2>Arguments</h2><div class="variablelist"><dl><dt><span class="term"><em class="parameter"><code>fd</code></em></span></dt><dd><p>File descriptor returned by <a class="link" href="re64.html" title="V4L2 open()"><code class="function">open()</code></a>.</p></dd><dt><span class="term"><em class="parameter"><code>request</code></em></span></dt><dd><p>VIDIOC_G_ENC_INDEX</p></dd><dt><span class="term"><em class="parameter"><code>argp</code></em></span></dt><dd><p></p></dd></dl></div></div><div class="refsect1" title="Description"><a id="id2706669"></a><h2>Description</h2><div class="note" title="Experimental" style="margin-left: 0.5in; margin-right: 0.5in;"><h3 class="title">Experimental</h3><p>This is an <a class="link" href="ch07s04.html" title="Experimental API Elements">experimental</a> interface and may change in the future.</p></div><p>The <code class="constant">VIDIOC_G_ENC_INDEX</code> ioctl provides meta data about a compressed video stream the same or another application currently reads from the driver, which is useful for random access into the stream without decoding it.</p><p>To read the data applications must call <code class="constant">VIDIOC_G_ENC_INDEX</code> with a pointer to a struct <a class="link" href="re38.html#v4l2-enc-idx" title="Table A.37. struct v4l2_enc_idx">v4l2_enc_idx</a>. On success the driver fills the <em class="structfield"><code>entry</code></em> array, stores the number of elements written in the <em class="structfield"><code>entries</code></em> field, and initializes the <em class="structfield"><code>entries_cap</code></em> field.</p><p>Each element of the <em class="structfield"><code>entry</code></em> array contains meta data about one picture. A <code class="constant">VIDIOC_G_ENC_INDEX</code> call reads up to <code class="constant">V4L2_ENC_IDX_ENTRIES</code> entries from a driver buffer, which can hold up to <em class="structfield"><code>entries_cap</code></em> entries. This number can be lower or higher than <code class="constant">V4L2_ENC_IDX_ENTRIES</code>, but not zero. When the application fails to read the meta data in time the oldest entries will be lost. When the buffer is empty or no capturing/encoding is in progress, <em class="structfield"><code>entries</code></em> will be zero.</p><p>Currently this ioctl is only defined for MPEG-2 program streams and video elementary streams.</p><div class="table"><a id="v4l2-enc-idx"></a><p class="title"><b>Table A.37. struct <span class="structname">v4l2_enc_idx</span></b></p><div class="table-contents"><table summary="struct v4l2_enc_idx" width="100%" border="0"><colgroup><col /><col /><col /></colgroup><tbody valign="top"><tr><td valign="top">__u32</td><td valign="top"><em class="structfield"><code>entries</code></em></td><td valign="top">The number of entries the driver stored in the <em class="structfield"><code>entry</code></em> array.</td></tr><tr><td valign="top">__u32</td><td valign="top"><em class="structfield"><code>entries_cap</code></em></td><td valign="top">The number of entries the driver can buffer. Must be greater than zero.</td></tr><tr><td valign="top">__u32</td><td valign="top"><em class="structfield"><code>reserved</code></em>[4]</td><td colspan="3" valign="top">Reserved for future extensions. Drivers must set the array to zero.</td></tr><tr><td valign="top">struct <a class="link" href="re38.html#v4l2-enc-idx-entry" title="Table A.38. struct v4l2_enc_idx_entry">v4l2_enc_idx_entry</a></td><td valign="top"><em class="structfield"><code>entry</code></em>[<code class="constant">V4L2_ENC_IDX_ENTRIES</code>]</td><td valign="top">Meta data about a compressed video stream. Each element of the array corresponds to one picture, sorted in ascending order by their <em class="structfield"><code>offset</code></em>.</td><td class="auto-generated"> </td><td class="auto-generated"> </td></tr></tbody></table></div></div><br class="table-break" /><div class="table"><a id="v4l2-enc-idx-entry"></a><p class="title"><b>Table A.38. struct <span class="structname">v4l2_enc_idx_entry</span></b></p><div class="table-contents"><table summary="struct v4l2_enc_idx_entry" width="100%" border="0"><colgroup><col /><col /><col /></colgroup><tbody valign="top"><tr><td valign="top">__u64</td><td valign="top"><em class="structfield"><code>offset</code></em></td><td valign="top">The offset in bytes from the beginning of the compressed video stream to the beginning of this picture, that is a <em class="wordasword">PES packet header</em> as defined in <a class="xref" href="bi01.html#mpeg2part1" title="ITU-T Rec. H.222.0 | ISO/IEC 13818-1 "Information technology — Generic coding of moving pictures and associated audio information: Systems"">[<abbr class="abbrev">ISO 13818-1</abbr>]</a> or a <em class="wordasword">picture header</em> as defined in <a class="xref" href="bi01.html#mpeg2part2" title="ITU-T Rec. H.262 | ISO/IEC 13818-2 "Information technology — Generic coding of moving pictures and associated audio information: Video"">[<abbr class="abbrev">ISO 13818-2</abbr>]</a>. When the encoder is stopped, the driver resets the offset to zero.</td></tr><tr><td valign="top">__u64</td><td valign="top"><em class="structfield"><code>pts</code></em></td><td valign="top">The 33 bit <em class="wordasword">Presentation Time Stamp</em> of this picture as defined in <a class="xref" href="bi01.html#mpeg2part1" title="ITU-T Rec. H.222.0 | ISO/IEC 13818-1 "Information technology — Generic coding of moving pictures and associated audio information: Systems"">[<abbr class="abbrev">ISO 13818-1</abbr>]</a>.</td></tr><tr><td valign="top">__u32</td><td valign="top"><em class="structfield"><code>length</code></em></td><td valign="top">The length of this picture in bytes.</td></tr><tr><td valign="top">__u32</td><td valign="top"><em class="structfield"><code>flags</code></em></td><td valign="top">Flags containing the coding type of this picture, see <a class="xref" href="re38.html#enc-idx-flags" title="Table A.39. Index Entry Flags">Table A.39, “Index Entry Flags”</a>.</td></tr><tr><td valign="top">__u32</td><td valign="top"><em class="structfield"><code>reserved</code></em>[2]</td><td valign="top">Reserved for future extensions. Drivers must set the array to zero.</td></tr></tbody></table></div></div><br class="table-break" /><div class="table"><a id="enc-idx-flags"></a><p class="title"><b>Table A.39. Index Entry Flags</b></p><div class="table-contents"><table summary="Index Entry Flags" width="100%" border="0"><colgroup><col /><col /><col /></colgroup><tbody valign="top"><tr><td valign="top"><code class="constant">V4L2_ENC_IDX_FRAME_I</code></td><td valign="top">0x00</td><td valign="top">This is an Intra-coded picture.</td></tr><tr><td valign="top"><code class="constant">V4L2_ENC_IDX_FRAME_P</code></td><td valign="top">0x01</td><td valign="top">This is a Predictive-coded picture.</td></tr><tr><td valign="top"><code class="constant">V4L2_ENC_IDX_FRAME_B</code></td><td valign="top">0x02</td><td valign="top">This is a Bidirectionally predictive-coded picture.</td></tr><tr><td valign="top"><code class="constant">V4L2_ENC_IDX_FRAME_MASK</code></td><td valign="top">0x0F</td><td valign="top"><em class="wordasword">AND</em> the flags field with this mask to obtain the picture coding type.</td></tr></tbody></table></div></div><br class="table-break" /></div><div class="refsect1" title="Return Value"><a id="id2707195"></a><h2>Return Value</h2><p>On success <span class="returnvalue">0</span> is returned, on error <span class="returnvalue">-1</span> and the <code class="varname">errno</code> variable is set appropriately:</p><div class="variablelist"><dl><dt><span class="term"><span class="errorcode">EINVAL</span></span></dt><dd><p>The driver does not support this ioctl.</p></dd></dl></div></div></div><div class="navfooter"><hr /><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="re37.html">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="apa.html">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="re39.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top">ioctl VIDIOC_G_CTRL, VIDIOC_S_CTRL </td><td width="20%" align="center"><a accesskey="h" href="index.html">Home</a></td><td width="40%" align="right" valign="top"> ioctl VIDIOC_G_EXT_CTRLS, VIDIOC_S_EXT_CTRLS, VIDIOC_TRY_EXT_CTRLS</td></tr></table></div></body></html>
