![Mauro Carvalho Chehab](/assets/img/avatar_default.png)
The V4L and DVB API's are there for a long time. however, up to now, no efforts were done to merge them to kernel DocBook. This patch adds the current versions of the specs as an unique compendium. Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>
189 lines
5.5 KiB
XML
189 lines
5.5 KiB
XML
<refentry id="vidioc-g-audio">
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<refmeta>
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<refentrytitle>ioctl VIDIOC_G_AUDIO, VIDIOC_S_AUDIO</refentrytitle>
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&manvol;
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</refmeta>
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<refnamediv>
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<refname>VIDIOC_G_AUDIO</refname>
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<refname>VIDIOC_S_AUDIO</refname>
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<refpurpose>Query or select the current audio input and its
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attributes</refpurpose>
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</refnamediv>
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<refsynopsisdiv>
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<funcsynopsis>
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<funcprototype>
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<funcdef>int <function>ioctl</function></funcdef>
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<paramdef>int <parameter>fd</parameter></paramdef>
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<paramdef>int <parameter>request</parameter></paramdef>
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<paramdef>struct v4l2_audio *<parameter>argp</parameter></paramdef>
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</funcprototype>
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</funcsynopsis>
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<funcsynopsis>
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<funcprototype>
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<funcdef>int <function>ioctl</function></funcdef>
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<paramdef>int <parameter>fd</parameter></paramdef>
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<paramdef>int <parameter>request</parameter></paramdef>
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<paramdef>const struct v4l2_audio *<parameter>argp</parameter></paramdef>
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</funcprototype>
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</funcsynopsis>
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</refsynopsisdiv>
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<refsect1>
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<title>Arguments</title>
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<variablelist>
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<varlistentry>
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<term><parameter>fd</parameter></term>
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<listitem>
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<para>&fd;</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><parameter>request</parameter></term>
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<listitem>
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<para>VIDIOC_G_AUDIO, VIDIOC_S_AUDIO</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><parameter>argp</parameter></term>
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<listitem>
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<para></para>
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</listitem>
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</varlistentry>
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</variablelist>
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</refsect1>
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<refsect1>
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<title>Description</title>
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<para>To query the current audio input applications zero out the
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<structfield>reserved</structfield> array of a &v4l2-audio;
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and call the <constant>VIDIOC_G_AUDIO</constant> ioctl with a pointer
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to this structure. Drivers fill the rest of the structure or return an
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&EINVAL; when the device has no audio inputs, or none which combine
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with the current video input.</para>
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<para>Audio inputs have one writable property, the audio mode. To
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select the current audio input <emphasis>and</emphasis> change the
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audio mode, applications initialize the
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<structfield>index</structfield> and <structfield>mode</structfield>
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fields, and the
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<structfield>reserved</structfield> array of a
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<structname>v4l2_audio</structname> structure and call the
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<constant>VIDIOC_S_AUDIO</constant> ioctl. Drivers may switch to a
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different audio mode if the request cannot be satisfied. However, this
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is a write-only ioctl, it does not return the actual new audio
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mode.</para>
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<table pgwide="1" frame="none" id="v4l2-audio">
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<title>struct <structname>v4l2_audio</structname></title>
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<tgroup cols="3">
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&cs-str;
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<tbody valign="top">
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<row>
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<entry>__u32</entry>
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<entry><structfield>index</structfield></entry>
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<entry>Identifies the audio input, set by the
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driver or application.</entry>
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</row>
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<row>
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<entry>__u8</entry>
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<entry><structfield>name</structfield>[32]</entry>
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<entry>Name of the audio input, a NUL-terminated ASCII
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string, for example: "Line In". This information is intended for the
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user, preferably the connector label on the device itself.</entry>
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</row>
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<row>
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<entry>__u32</entry>
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<entry><structfield>capability</structfield></entry>
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<entry>Audio capability flags, see <xref
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linkend="audio-capability" />.</entry>
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</row>
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<row>
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<entry>__u32</entry>
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<entry><structfield>mode</structfield></entry>
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<entry>Audio mode flags set by drivers and applications (on
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<constant>VIDIOC_S_AUDIO</constant> ioctl), see <xref linkend="audio-mode" />.</entry>
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</row>
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<row>
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<entry>__u32</entry>
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<entry><structfield>reserved</structfield>[2]</entry>
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<entry>Reserved for future extensions. Drivers and
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applications must set the array to zero.</entry>
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</row>
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</tbody>
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</tgroup>
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</table>
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<table pgwide="1" frame="none" id="audio-capability">
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<title>Audio Capability Flags</title>
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<tgroup cols="3">
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&cs-def;
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<tbody valign="top">
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<row>
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<entry><constant>V4L2_AUDCAP_STEREO</constant></entry>
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<entry>0x00001</entry>
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<entry>This is a stereo input. The flag is intended to
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automatically disable stereo recording etc. when the signal is always
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monaural. The API provides no means to detect if stereo is
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<emphasis>received</emphasis>, unless the audio input belongs to a
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tuner.</entry>
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</row>
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<row>
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<entry><constant>V4L2_AUDCAP_AVL</constant></entry>
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<entry>0x00002</entry>
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<entry>Automatic Volume Level mode is supported.</entry>
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</row>
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</tbody>
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</tgroup>
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</table>
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<table pgwide="1" frame="none" id="audio-mode">
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<title>Audio Mode Flags</title>
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<tgroup cols="3">
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&cs-def;
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<tbody valign="top">
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<row>
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<entry><constant>V4L2_AUDMODE_AVL</constant></entry>
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<entry>0x00001</entry>
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<entry>AVL mode is on.</entry>
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</row>
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</tbody>
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</tgroup>
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</table>
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</refsect1>
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<refsect1>
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&return-value;
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<variablelist>
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<varlistentry>
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<term><errorcode>EINVAL</errorcode></term>
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<listitem>
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<para>No audio inputs combine with the current video input,
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or the number of the selected audio input is out of bounds or it does
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not combine, or there are no audio inputs at all and the ioctl is not
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supported.</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><errorcode>EBUSY</errorcode></term>
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<listitem>
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<para>I/O is in progress, the input cannot be
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switched.</para>
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</listitem>
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</varlistentry>
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</variablelist>
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</refsect1>
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</refentry>
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<!--
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Local Variables:
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mode: sgml
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sgml-parent-document: "v4l2.sgml"
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indent-tabs-mode: nil
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End:
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-->
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