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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.</para>
168 </listitem>
169 </varlistentry>
170 </variablelist>
171 </refsect1>
172</refentry>
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