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<refentry id="vidioc-g-audio">
<refmeta>
<refentrytitle>ioctl VIDIOC_G_AUDIO, VIDIOC_S_AUDIO</refentrytitle>
&manvol;
</refmeta>
<refnamediv>
<refname>VIDIOC_G_AUDIO</refname>
<refname>VIDIOC_S_AUDIO</refname>
<refpurpose>Query or select the current audio input and its
attributes</refpurpose>
</refnamediv>
<refsynopsisdiv>
<funcsynopsis>
<funcprototype>
<funcdef>int <function>ioctl</function></funcdef>
<paramdef>int <parameter>fd</parameter></paramdef>
<paramdef>int <parameter>request</parameter></paramdef>
<paramdef>struct v4l2_audio *<parameter>argp</parameter></paramdef>
</funcprototype>
</funcsynopsis>
<funcsynopsis>
<funcprototype>
<funcdef>int <function>ioctl</function></funcdef>
<paramdef>int <parameter>fd</parameter></paramdef>
<paramdef>int <parameter>request</parameter></paramdef>
<paramdef>const struct v4l2_audio *<parameter>argp</parameter></paramdef>
</funcprototype>
</funcsynopsis>
</refsynopsisdiv>
<refsect1>
<title>Arguments</title>
<variablelist>
<varlistentry>
<term><parameter>fd</parameter></term>
<listitem>
<para>&fd;</para>
</listitem>
</varlistentry>
<varlistentry>
<term><parameter>request</parameter></term>
<listitem>
<para>VIDIOC_G_AUDIO, VIDIOC_S_AUDIO</para>
</listitem>
</varlistentry>
<varlistentry>
<term><parameter>argp</parameter></term>
<listitem>
<para></para>
</listitem>
</varlistentry>
</variablelist>
</refsect1>
<refsect1>
<title>Description</title>
<para>To query the current audio input applications zero out the
<structfield>reserved</structfield> array of a &v4l2-audio;
and call the <constant>VIDIOC_G_AUDIO</constant> ioctl with a pointer
to this structure. Drivers fill the rest of the structure or return an
&EINVAL; when the device has no audio inputs, or none which combine
with the current video input.</para>
<para>Audio inputs have one writable property, the audio mode. To
select the current audio input <emphasis>and</emphasis> change the
audio mode, applications initialize the
<structfield>index</structfield> and <structfield>mode</structfield>
fields, and the
<structfield>reserved</structfield> array of a
<structname>v4l2_audio</structname> structure and call the
<constant>VIDIOC_S_AUDIO</constant> ioctl. Drivers may switch to a
different audio mode if the request cannot be satisfied. However, this
is a write-only ioctl, it does not return the actual new audio
mode.</para>
<table pgwide="1" frame="none" id="v4l2-audio">
<title>struct <structname>v4l2_audio</structname></title>
<tgroup cols="3">
&cs-str;
<tbody valign="top">
<row>
<entry>__u32</entry>
<entry><structfield>index</structfield></entry>
<entry>Identifies the audio input, set by the
driver or application.</entry>
</row>
<row>
<entry>__u8</entry>
<entry><structfield>name</structfield>[32]</entry>
<entry>Name of the audio input, a NUL-terminated ASCII
string, for example: "Line In". This information is intended for the
user, preferably the connector label on the device itself.</entry>
</row>
<row>
<entry>__u32</entry>
<entry><structfield>capability</structfield></entry>
<entry>Audio capability flags, see <xref
linkend="audio-capability" />.</entry>
</row>
<row>
<entry>__u32</entry>
<entry><structfield>mode</structfield></entry>
<entry>Audio mode flags set by drivers and applications (on
<constant>VIDIOC_S_AUDIO</constant> ioctl), see <xref linkend="audio-mode" />.</entry>
</row>
<row>
<entry>__u32</entry>
<entry><structfield>reserved</structfield>[2]</entry>
<entry>Reserved for future extensions. Drivers and
applications must set the array to zero.</entry>
</row>
</tbody>
</tgroup>
</table>
<table pgwide="1" frame="none" id="audio-capability">
<title>Audio Capability Flags</title>
<tgroup cols="3">
&cs-def;
<tbody valign="top">
<row>
<entry><constant>V4L2_AUDCAP_STEREO</constant></entry>
<entry>0x00001</entry>
<entry>This is a stereo input. The flag is intended to
automatically disable stereo recording etc. when the signal is always
monaural. The API provides no means to detect if stereo is
<emphasis>received</emphasis>, unless the audio input belongs to a
tuner.</entry>
</row>
<row>
<entry><constant>V4L2_AUDCAP_AVL</constant></entry>
<entry>0x00002</entry>
<entry>Automatic Volume Level mode is supported.</entry>
</row>
</tbody>
</tgroup>
</table>
<table pgwide="1" frame="none" id="audio-mode">
<title>Audio Mode Flags</title>
<tgroup cols="3">
&cs-def;
<tbody valign="top">
<row>
<entry><constant>V4L2_AUDMODE_AVL</constant></entry>
<entry>0x00001</entry>
<entry>AVL mode is on.</entry>
</row>
</tbody>
</tgroup>
</table>
</refsect1>
<refsect1>
&return-value;
<variablelist>
<varlistentry>
<term><errorcode>EINVAL</errorcode></term>
<listitem>
<para>No audio inputs combine with the current video input,
or the number of the selected audio input is out of bounds or it does
not combine.</para>
</listitem>
</varlistentry>
</variablelist>
</refsect1>
</refentry>
|
