1<html><head><meta http-equiv="Content-Type" content="text/html; charset=ANSI_X3.4-1968"><title>ioctl VIDIOC_G_AUDIO, VIDIOC_S_AUDIO</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 A. Function Reference"><link rel="prev" href="vidioc-expbuf.html" title="ioctl VIDIOC_EXPBUF"><link rel="next" href="vidioc-g-audioout.html" title="ioctl VIDIOC_G_AUDOUT, VIDIOC_S_AUDOUT"></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_G_AUDIO, VIDIOC_S_AUDIO</th></tr><tr><td width="20%" align="left"><a accesskey="p" href="vidioc-expbuf.html">Prev</a> </td><th width="60%" align="center">Appendix A. Function Reference</th><td width="20%" align="right"> <a accesskey="n" href="vidioc-g-audioout.html">Next</a></td></tr></table><hr></div><div class="refentry"><a name="vidioc-g-audio"></a><div class="titlepage"></div><div class="refnamediv"><h2>Name</h2><p>VIDIOC_G_AUDIO, VIDIOC_S_AUDIO — Query or select the current audio input and its 2attributes</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> </td><td>int <var class="pdparam">request</var>, </td></tr><tr><td> </td><td>struct v4l2_audio *<var class="pdparam">argp</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer"> </div></div><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> </td><td>int <var class="pdparam">request</var>, </td></tr><tr><td> </td><td>const struct v4l2_audio *<var class="pdparam">argp</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer"> </div></div></div><div class="refsect1"><a name="idp1113629372"></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_G_AUDIO, VIDIOC_S_AUDIO</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="idp1113633436"></a><h2>Description</h2><p>To query the current audio input applications zero out the 3<em class="structfield"><code>reserved</code></em> array of a struct <a class="link" href="vidioc-g-audio.html#v4l2-audio" title="Table A.51. struct v4l2_audio">v4l2_audio</a> 4and call the <code class="constant">VIDIOC_G_AUDIO</code> ioctl with a pointer 5to this structure. Drivers fill the rest of the structure or return an 6<span class="errorcode">EINVAL</span> error code when the device has no audio inputs, or none which combine 7with the current video input.</p><p>Audio inputs have one writable property, the audio mode. To 8select the current audio input <span class="emphasis"><em>and</em></span> change the 9audio mode, applications initialize the 10<em class="structfield"><code>index</code></em> and <em class="structfield"><code>mode</code></em> 11fields, and the 12<em class="structfield"><code>reserved</code></em> array of a 13<span class="structname">v4l2_audio</span> structure and call the 14<code class="constant">VIDIOC_S_AUDIO</code> ioctl. Drivers may switch to a 15different audio mode if the request cannot be satisfied. However, this 16is a write-only ioctl, it does not return the actual new audio 17mode.</p><div class="table"><a name="v4l2-audio"></a><p class="title"><b>Table A.51. struct <span class="structname">v4l2_audio</span></b></p><div class="table-contents"><table summary="struct v4l2_audio" width="100%" border="0"><colgroup><col class="c1"><col class="c2"><col class="c3"></colgroup><tbody valign="top"><tr><td valign="top">__u32</td><td valign="top"><em class="structfield"><code>index</code></em></td><td valign="top">Identifies the audio input, set by the 18driver or application.</td></tr><tr><td valign="top">__u8</td><td valign="top"><em class="structfield"><code>name</code></em>[32]</td><td valign="top">Name of the audio input, a NUL-terminated ASCII 19string, for example: "Line In". This information is intended for the 20user, preferably the connector label on the device itself.</td></tr><tr><td valign="top">__u32</td><td valign="top"><em class="structfield"><code>capability</code></em></td><td valign="top">Audio capability flags, see <a class="xref" href="vidioc-g-audio.html#audio-capability" title="Table A.52. Audio Capability Flags">Table A.52, “Audio Capability Flags”</a>.</td></tr><tr><td valign="top">__u32</td><td valign="top"><em class="structfield"><code>mode</code></em></td><td valign="top">Audio mode flags set by drivers and applications (on 21 <code class="constant">VIDIOC_S_AUDIO</code> ioctl), see <a class="xref" href="vidioc-g-audio.html#audio-mode" title="Table A.53. Audio Mode Flags">Table A.53, “Audio Mode 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 and 22applications must set the array to zero.</td></tr></tbody></table></div></div><br class="table-break"><div class="table"><a name="audio-capability"></a><p class="title"><b>Table A.52. Audio Capability Flags</b></p><div class="table-contents"><table summary="Audio Capability Flags" width="100%" border="0"><colgroup><col class="c1"><col class="c2"><col class="c3"></colgroup><tbody valign="top"><tr><td valign="top"><code class="constant">V4L2_AUDCAP_STEREO</code></td><td valign="top">0x00001</td><td valign="top">This is a stereo input. The flag is intended to 23automatically disable stereo recording etc. when the signal is always 24monaural. The API provides no means to detect if stereo is 25<span class="emphasis"><em>received</em></span>, unless the audio input belongs to a 26tuner.</td></tr><tr><td valign="top"><code class="constant">V4L2_AUDCAP_AVL</code></td><td valign="top">0x00002</td><td valign="top">Automatic Volume Level mode is supported.</td></tr></tbody></table></div></div><br class="table-break"><div class="table"><a name="audio-mode"></a><p class="title"><b>Table A.53. Audio Mode Flags</b></p><div class="table-contents"><table summary="Audio Mode Flags" width="100%" border="0"><colgroup><col class="c1"><col class="c2"><col class="c3"></colgroup><tbody valign="top"><tr><td valign="top"><code class="constant">V4L2_AUDMODE_AVL</code></td><td valign="top">0x00001</td><td valign="top">AVL mode is on.</td></tr></tbody></table></div></div><br class="table-break"></div><div class="refsect1"><a name="idp1113655732"></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 19.1. Generic error codes">Generic Error Codes</a> chapter.</p><div class="variablelist"><dl class="variablelist"><dt><span class="term"><span class="errorcode">EINVAL</span></span></dt><dd><p>No audio inputs combine with the current video input, 27or the number of the selected audio input is out of bounds or it does 28not combine.</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-expbuf.html">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="user-func.html">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="vidioc-g-audioout.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top">ioctl VIDIOC_EXPBUF </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_AUDOUT, VIDIOC_S_AUDOUT</td></tr></table></div></body></html> 29