Based on kernel version 4.7.2. Page generated on 2016-08-22 22:45 EST.
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 11 attributes</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; 63 and call the <constant>VIDIOC_G_AUDIO</constant> ioctl with a pointer 64 to 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 66 with the current video input.</para> 67 68 <para>Audio inputs have one writable property, the audio mode. To 69 select the current audio input <emphasis>and</emphasis> change the 70 audio mode, applications initialize the 71 <structfield>index</structfield> and <structfield>mode</structfield> 72 fields, 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 76 different audio mode if the request cannot be satisfied. However, this 77 is a write-only ioctl, it does not return the actual new audio 78 mode.</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 89 driver 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 95 string, for example: "Line In". This information is intended for the 96 user, 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 114 applications 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 129 automatically disable stereo recording etc. when the signal is always 130 monaural. The API provides no means to detect if stereo is 131 <emphasis>received</emphasis>, unless the audio input belongs to a 132 tuner.</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, 166 or the number of the selected audio input is out of bounds or it does 167 not combine.</para> 168 </listitem> 169 </varlistentry> 170 </variablelist> 171 </refsect1> 172 </refentry>
