/Documentation/DocBook/v4l/vidioc-g-audio.xml
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Possible License(s): GPL-2.0, LGPL-2.0, AGPL-1.0
1<refentry id="vidioc-g-audio">
2 <refmeta>
3 <refentrytitle>ioctl VIDIOC_G_AUDIO, VIDIOC_S_AUDIO</refentrytitle>
4 &manvol;
5 </refmeta>
6
7 <refnamediv>
8 <refname>VIDIOC_G_AUDIO</refname>
9 <refname>VIDIOC_S_AUDIO</refname>
10 <refpurpose>Query or select the current audio input and its
11attributes</refpurpose>
12 </refnamediv>
13
14 <refsynopsisdiv>
15 <funcsynopsis>
16 <funcprototype>
17 <funcdef>int <function>ioctl</function></funcdef>
18 <paramdef>int <parameter>fd</parameter></paramdef>
19 <paramdef>int <parameter>request</parameter></paramdef>
20 <paramdef>struct v4l2_audio *<parameter>argp</parameter></paramdef>
21 </funcprototype>
22 </funcsynopsis>
23 <funcsynopsis>
24 <funcprototype>
25 <funcdef>int <function>ioctl</function></funcdef>
26 <paramdef>int <parameter>fd</parameter></paramdef>
27 <paramdef>int <parameter>request</parameter></paramdef>
28 <paramdef>const struct v4l2_audio *<parameter>argp</parameter></paramdef>
29 </funcprototype>
30 </funcsynopsis>
31 </refsynopsisdiv>
32
33 <refsect1>
34 <title>Arguments</title>
35
36 <variablelist>
37 <varlistentry>
38 <term><parameter>fd</parameter></term>
39 <listitem>
40 <para>&fd;</para>
41 </listitem>
42 </varlistentry>
43 <varlistentry>
44 <term><parameter>request</parameter></term>
45 <listitem>
46 <para>VIDIOC_G_AUDIO, VIDIOC_S_AUDIO</para>
47 </listitem>
48 </varlistentry>
49 <varlistentry>
50 <term><parameter>argp</parameter></term>
51 <listitem>
52 <para></para>
53 </listitem>
54 </varlistentry>
55 </variablelist>
56 </refsect1>
57
58 <refsect1>
59 <title>Description</title>
60
61 <para>To query the current audio input applications zero out the
62<structfield>reserved</structfield> array of a &v4l2-audio;
63and call the <constant>VIDIOC_G_AUDIO</constant> ioctl with a pointer
64to this structure. Drivers fill the rest of the structure or return an
65&EINVAL; when the device has no audio inputs, or none which combine
66with the current video input.</para>
67
68 <para>Audio inputs have one writable property, the audio mode. To
69select the current audio input <emphasis>and</emphasis> change the
70audio mode, applications initialize the
71<structfield>index</structfield> and <structfield>mode</structfield>
72fields, and the
73<structfield>reserved</structfield> array of a
74<structname>v4l2_audio</structname> structure and call the
75<constant>VIDIOC_S_AUDIO</constant> ioctl. Drivers may switch to a
76different audio mode if the request cannot be satisfied. However, this
77is a write-only ioctl, it does not return the actual new audio
78mode.</para>
79
80 <table pgwide="1" frame="none" id="v4l2-audio">
81 <title>struct <structname>v4l2_audio</structname></title>
82 <tgroup cols="3">
83 &cs-str;
84 <tbody valign="top">
85 <row>
86 <entry>__u32</entry>
87 <entry><structfield>index</structfield></entry>
88 <entry>Identifies the audio input, set by the
89driver or application.</entry>
90 </row>
91 <row>
92 <entry>__u8</entry>
93 <entry><structfield>name</structfield>[32]</entry>
94 <entry>Name of the audio input, a NUL-terminated ASCII
95string, for example: "Line In". This information is intended for the
96user, preferably the connector label on the device itself.</entry>
97 </row>
98 <row>
99 <entry>__u32</entry>
100 <entry><structfield>capability</structfield></entry>
101 <entry>Audio capability flags, see <xref
102 linkend="audio-capability" />.</entry>
103 </row>
104 <row>
105 <entry>__u32</entry>
106 <entry><structfield>mode</structfield></entry>
107 <entry>Audio mode flags set by drivers and applications (on
108 <constant>VIDIOC_S_AUDIO</constant> ioctl), see <xref linkend="audio-mode" />.</entry>
109 </row>
110 <row>
111 <entry>__u32</entry>
112 <entry><structfield>reserved</structfield>[2]</entry>
113 <entry>Reserved for future extensions. Drivers and
114applications must set the array to zero.</entry>
115 </row>
116 </tbody>
117 </tgroup>
118 </table>
119
120 <table pgwide="1" frame="none" id="audio-capability">
121 <title>Audio Capability Flags</title>
122 <tgroup cols="3">
123 &cs-def;
124 <tbody valign="top">
125 <row>
126 <entry><constant>V4L2_AUDCAP_STEREO</constant></entry>
127 <entry>0x00001</entry>
128 <entry>This is a stereo input. The flag is intended to
129automatically disable stereo recording etc. when the signal is always
130monaural. The API provides no means to detect if stereo is
131<emphasis>received</emphasis>, unless the audio input belongs to a
132tuner.</entry>
133 </row>
134 <row>
135 <entry><constant>V4L2_AUDCAP_AVL</constant></entry>
136 <entry>0x00002</entry>
137 <entry>Automatic Volume Level mode is supported.</entry>
138 </row>
139 </tbody>
140 </tgroup>
141 </table>
142
143 <table pgwide="1" frame="none" id="audio-mode">
144 <title>Audio Mode Flags</title>
145 <tgroup cols="3">
146 &cs-def;
147 <tbody valign="top">
148 <row>
149 <entry><constant>V4L2_AUDMODE_AVL</constant></entry>
150 <entry>0x00001</entry>
151 <entry>AVL mode is on.</entry>
152 </row>
153 </tbody>
154 </tgroup>
155 </table>
156 </refsect1>
157
158 <refsect1>
159 &return-value;
160
161 <variablelist>
162 <varlistentry>
163 <term><errorcode>EINVAL</errorcode></term>
164 <listitem>
165 <para>No audio inputs combine with the current video input,
166or the number of the selected audio input is out of bounds or it does
167not combine, or there are no audio inputs at all and the ioctl is not
168supported.</para>
169 </listitem>
170 </varlistentry>
171 <varlistentry>
172 <term><errorcode>EBUSY</errorcode></term>
173 <listitem>
174 <para>I/O is in progress, the input cannot be
175switched.</para>
176 </listitem>
177 </varlistentry>
178 </variablelist>
179 </refsect1>
180</refentry>
181
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