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Diffstat (limited to 'Documentation/DocBook/media/v4l/vidioc-g-audio.xml')
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1 files changed, 172 insertions, 0 deletions
diff --git a/Documentation/DocBook/media/v4l/vidioc-g-audio.xml b/Documentation/DocBook/media/v4l/vidioc-g-audio.xml new file mode 100644 index 00000000..d7bb9b37 --- /dev/null +++ b/Documentation/DocBook/media/v4l/vidioc-g-audio.xml @@ -0,0 +1,172 @@ +<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> |