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Based on kernel version 3.16. Page generated on 2014-08-06 21:39 EST.

1	<refentry id="vidioc-g-audioout">
2	  <refmeta>
3	    <refentrytitle>ioctl VIDIOC_G_AUDOUT, VIDIOC_S_AUDOUT</refentrytitle>
4	    &manvol;
5	  </refmeta>
6	
7	  <refnamediv>
8	    <refname>VIDIOC_G_AUDOUT</refname>
9	    <refname>VIDIOC_S_AUDOUT</refname>
10	    <refpurpose>Query or select the current audio output</refpurpose>
11	  </refnamediv>
12	
13	  <refsynopsisdiv>
14	    <funcsynopsis>
15	      <funcprototype>
16		<funcdef>int <function>ioctl</function></funcdef>
17		<paramdef>int <parameter>fd</parameter></paramdef>
18		<paramdef>int <parameter>request</parameter></paramdef>
19		<paramdef>struct v4l2_audioout *<parameter>argp</parameter></paramdef>
20	      </funcprototype>
21	    </funcsynopsis>
22	    <funcsynopsis>
23	      <funcprototype>
24		<funcdef>int <function>ioctl</function></funcdef>
25		<paramdef>int <parameter>fd</parameter></paramdef>
26		<paramdef>int <parameter>request</parameter></paramdef>
27		<paramdef>const struct v4l2_audioout *<parameter>argp</parameter></paramdef>
28	      </funcprototype>
29	    </funcsynopsis>
30	  </refsynopsisdiv>
31	
32	  <refsect1>
33	    <title>Arguments</title>
34	
35	    <variablelist>
36	      <varlistentry>
37		<term><parameter>fd</parameter></term>
38		<listitem>
39		  <para>&fd;</para>
40		</listitem>
41	      </varlistentry>
42	      <varlistentry>
43		<term><parameter>request</parameter></term>
44		<listitem>
45		  <para>VIDIOC_G_AUDOUT, VIDIOC_S_AUDOUT</para>
46		</listitem>
47	      </varlistentry>
48	      <varlistentry>
49		<term><parameter>argp</parameter></term>
50		<listitem>
51		  <para></para>
52		</listitem>
53	      </varlistentry>
54	    </variablelist>
55	  </refsect1>
56	
57	  <refsect1>
58	    <title>Description</title>
59	
60	    <para>To query the current audio output applications zero out the
61	<structfield>reserved</structfield> array of a &v4l2-audioout; and
62	call the <constant>VIDIOC_G_AUDOUT</constant> ioctl with a pointer
63	to this structure. Drivers fill the rest of the structure or return an
64	&EINVAL; when the device has no audio inputs, or none which combine
65	with the current video output.</para>
66	
67	    <para>Audio outputs have no writable properties. Nevertheless, to
68	select the current audio output applications can initialize the
69	<structfield>index</structfield> field and
70	<structfield>reserved</structfield> array (which in the future may
71	contain writable properties) of a
72	<structname>v4l2_audioout</structname> structure and call the
73	<constant>VIDIOC_S_AUDOUT</constant> ioctl. Drivers switch to the
74	requested output or return the &EINVAL; when the index is out of
75	bounds. This is a write-only ioctl, it does not return the current
76	audio output attributes as <constant>VIDIOC_G_AUDOUT</constant>
77	does.</para>
78	
79	    <para>Note connectors on a TV card to loop back the received audio
80	signal to a sound card are not audio outputs in this sense.</para>
81	
82	    <table pgwide="1" frame="none" id="v4l2-audioout">
83	      <title>struct <structname>v4l2_audioout</structname></title>
84	      <tgroup cols="3">
85		&cs-str;
86		<tbody valign="top">
87		  <row>
88		    <entry>__u32</entry>
89		    <entry><structfield>index</structfield></entry>
90		    <entry>Identifies the audio output, set by the
91	driver or application.</entry>
92		  </row>
93		  <row>
94		    <entry>__u8</entry>
95		    <entry><structfield>name</structfield>[32]</entry>
96		    <entry>Name of the audio output, a NUL-terminated ASCII
97	string, for example: "Line Out". This information is intended for the
98	user, preferably the connector label on the device itself.</entry>
99		  </row>
100		  <row>
101		    <entry>__u32</entry>
102		    <entry><structfield>capability</structfield></entry>
103		    <entry>Audio capability flags, none defined yet. Drivers
104	must set this field to zero.</entry>
105		  </row>
106		  <row>
107		    <entry>__u32</entry>
108		    <entry><structfield>mode</structfield></entry>
109		    <entry>Audio mode, none defined yet. Drivers and
110	applications (on <constant>VIDIOC_S_AUDOUT</constant>) must set this
111	field to zero.</entry>
112		  </row>
113		  <row>
114		    <entry>__u32</entry>
115		    <entry><structfield>reserved</structfield>[2]</entry>
116		    <entry>Reserved for future extensions. Drivers and
117	applications must set the array to zero.</entry>
118		  </row>
119		</tbody>
120	      </tgroup>
121	    </table>
122	  </refsect1>
123	
124	  <refsect1>
125	    &return-value;
126	
127	    <variablelist>
128	      <varlistentry>
129		<term><errorcode>EINVAL</errorcode></term>
130		<listitem>
131		  <para>No audio outputs combine with the current video
132	output, or the number of the selected audio output is out of bounds or
133	it does not combine.</para>
134		</listitem>
135	      </varlistentry>
136	    </variablelist>
137	  </refsect1>
138	</refentry>
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