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- <refentry id="vidioc-g-audioout">
- <refmeta>
- <refentrytitle>ioctl VIDIOC_G_AUDOUT, VIDIOC_S_AUDOUT</refentrytitle>
- &manvol;
- </refmeta>
- <refnamediv>
- <refname>VIDIOC_G_AUDOUT</refname>
- <refname>VIDIOC_S_AUDOUT</refname>
- <refpurpose>Query or select the current audio output</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_audioout *<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_audioout *<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_AUDOUT, VIDIOC_S_AUDOUT</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 output applications zero out the
- <structfield>reserved</structfield> array of a &v4l2-audioout; and
- call the <constant>VIDIOC_G_AUDOUT</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 output.</para>
- <para>Audio outputs have no writable properties. Nevertheless, to
- select the current audio output applications can initialize the
- <structfield>index</structfield> field and
- <structfield>reserved</structfield> array (which in the future may
- contain writable properties) of a
- <structname>v4l2_audioout</structname> structure and call the
- <constant>VIDIOC_S_AUDOUT</constant> ioctl. Drivers switch to the
- requested output or return the &EINVAL; when the index is out of
- bounds. This is a write-only ioctl, it does not return the current
- audio output attributes as <constant>VIDIOC_G_AUDOUT</constant>
- does.</para>
- <para>Note connectors on a TV card to loop back the received audio
- signal to a sound card are not audio outputs in this sense.</para>
- <table pgwide="1" frame="none" id="v4l2-audioout">
- <title>struct <structname>v4l2_audioout</structname></title>
- <tgroup cols="3">
- &cs-str;
- <tbody valign="top">
- <row>
- <entry>__u32</entry>
- <entry><structfield>index</structfield></entry>
- <entry>Identifies the audio output, set by the
- driver or application.</entry>
- </row>
- <row>
- <entry>__u8</entry>
- <entry><structfield>name</structfield>[32]</entry>
- <entry>Name of the audio output, a NUL-terminated ASCII
- string, for example: "Line Out". 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, none defined yet. Drivers
- must set this field to zero.</entry>
- </row>
- <row>
- <entry>__u32</entry>
- <entry><structfield>mode</structfield></entry>
- <entry>Audio mode, none defined yet. Drivers and
- applications (on <constant>VIDIOC_S_AUDOUT</constant>) must set this
- field to zero.</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>
- </refsect1>
- <refsect1>
- &return-value;
- <variablelist>
- <varlistentry>
- <term><errorcode>EINVAL</errorcode></term>
- <listitem>
- <para>No audio outputs combine with the current video
- output, or the number of the selected audio output is out of bounds or
- it does not combine.</para>
- </listitem>
- </varlistentry>
- </variablelist>
- </refsect1>
- </refentry>
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