1<html><head><meta http-equiv="Content-Type" content="text/html; charset=ANSI_X3.4-1968"><title>ioctl VIDIOC_QUERYSTD</title><meta name="generator" content="DocBook XSL Stylesheets V1.78.1"><link rel="home" href="index.html" title="LINUX MEDIA INFRASTRUCTURE API"><link rel="up" href="user-func.html" title="Appendix&#160;A.&#160;Function Reference"><link rel="prev" href="vidioc-query-dv-timings.html" title="ioctl VIDIOC_QUERY_DV_TIMINGS"><link rel="next" href="vidioc-reqbufs.html" title="ioctl VIDIOC_REQBUFS"></head><body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="3" align="center">ioctl VIDIOC_QUERYSTD</th></tr><tr><td width="20%" align="left"><a accesskey="p" href="vidioc-query-dv-timings.html">Prev</a>&#160;</td><th width="60%" align="center">Appendix&#160;A.&#160;Function Reference</th><td width="20%" align="right">&#160;<a accesskey="n" href="vidioc-reqbufs.html">Next</a></td></tr></table><hr></div><div class="refentry"><a name="vidioc-querystd"></a><div class="titlepage"></div><div class="refnamediv"><h2>Name</h2><p>VIDIOC_QUERYSTD &#8212; Sense the video standard received by the current
2input</p></div><div class="refsynopsisdiv"><h2>Synopsis</h2><div class="funcsynopsis"><table border="0" class="funcprototype-table" summary="Function synopsis" style="cellspacing: 0; cellpadding: 0;"><tr><td><code class="funcdef">int <b class="fsfunc">ioctl</b>(</code></td><td>int <var class="pdparam">fd</var>, </td></tr><tr><td>&#160;</td><td>int <var class="pdparam">request</var>, </td></tr><tr><td>&#160;</td><td>v4l2_std_id *<var class="pdparam">argp</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer">&#160;</div></div></div><div class="refsect1"><a name="idp1116162772"></a><h2>Arguments</h2><div class="variablelist"><dl class="variablelist"><dt><span class="term"><em class="parameter"><code>fd</code></em></span></dt><dd><p>File descriptor returned by <a class="link" href="func-open.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_QUERYSTD</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"><a name="idp1116232948"></a><h2>Description</h2><p>The hardware may be able to detect the current video
3standard automatically. To do so, applications call <code class="constant">
4VIDIOC_QUERYSTD</code> with a pointer to a <a class="link" href="vidioc-enumstd.html#v4l2-std-id" title="Table&#160;A.48.&#160;typedef v4l2_std_id">v4l2_std_id</a> type. The
5driver stores here a set of candidates, this can be a single flag or a
6set of supported standards if for example the hardware can only
7distinguish between 50 and 60 Hz systems. If no signal was detected,
8then the driver will return V4L2_STD_UNKNOWN. When detection is not
9possible or fails, the set must contain all standards supported by the
10current video input or output.</p></div><div class="refsect1"><a name="idp1116234636"></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. The generic error codes are described at the <a class="link" href="gen_errors.html#gen-errors" title="Table&#160;19.1.&#160;Generic error codes">Generic Error Codes</a> chapter.</p><div class="variablelist"><dl class="variablelist"><dt><span class="term"><span class="errorcode">ENODATA</span></span></dt><dd><p>Standard video timings are not supported for this input or output.</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="vidioc-query-dv-timings.html">Prev</a>&#160;</td><td width="20%" align="center"><a accesskey="u" href="user-func.html">Up</a></td><td width="40%" align="right">&#160;<a accesskey="n" href="vidioc-reqbufs.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top">ioctl VIDIOC_QUERY_DV_TIMINGS&#160;</td><td width="20%" align="center"><a accesskey="h" href="index.html">Home</a></td><td width="40%" align="right" valign="top">&#160;ioctl VIDIOC_REQBUFS</td></tr></table></div></body></html>
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