1 .. -*- coding: utf-8; mode: rst -*-
5 ************************************
6 ioctl VIDIOC_G_AUDIO, VIDIOC_S_AUDIO
7 ************************************
12 VIDIOC_G_AUDIO - VIDIOC_S_AUDIO - Query or select the current audio input and its attributes
18 .. c:function:: int ioctl( int fd, VIDIOC_G_AUDIO, struct v4l2_audio *argp )
21 .. c:function:: int ioctl( int fd, VIDIOC_S_AUDIO, const struct v4l2_audio *argp )
29 File descriptor returned by :ref:`open() <func-open>`.
37 To query the current audio input applications zero out the ``reserved``
38 array of a struct :c:type:`v4l2_audio` and call the
39 :ref:`VIDIOC_G_AUDIO <VIDIOC_G_AUDIO>` ioctl with a pointer to this structure. Drivers fill
40 the rest of the structure or return an ``EINVAL`` error code when the device
41 has no audio inputs, or none which combine with the current video input.
43 Audio inputs have one writable property, the audio mode. To select the
44 current audio input *and* change the audio mode, applications initialize
45 the ``index`` and ``mode`` fields, and the ``reserved`` array of a
46 struct :c:type:`v4l2_audio` structure and call the :ref:`VIDIOC_S_AUDIO <VIDIOC_G_AUDIO>`
47 ioctl. Drivers may switch to a different audio mode if the request
48 cannot be satisfied. However, this is a write-only ioctl, it does not
49 return the actual new audio mode.
52 .. tabularcolumns:: |p{4.4cm}|p{4.4cm}|p{8.7cm}|
54 .. c:type:: v4l2_audio
56 .. flat-table:: struct v4l2_audio
68 - Identifies the audio input, set by the driver or application.
76 - Name of the audio input, a NUL-terminated ASCII string, for
77 example: "Line In". This information is intended for the user,
78 preferably the connector label on the device itself.
86 - Audio capability flags, see :ref:`audio-capability`.
94 - Audio mode flags set by drivers and applications (on
95 :ref:`VIDIOC_S_AUDIO <VIDIOC_G_AUDIO>` ioctl), see :ref:`audio-mode`.
103 - Reserved for future extensions. Drivers and applications must set
108 .. tabularcolumns:: |p{6.6cm}|p{2.2cm}|p{8.7cm}|
110 .. _audio-capability:
112 .. flat-table:: Audio Capability Flags
120 - ``V4L2_AUDCAP_STEREO``
124 - This is a stereo input. The flag is intended to automatically
125 disable stereo recording etc. when the signal is always monaural.
126 The API provides no means to detect if stereo is *received*,
127 unless the audio input belongs to a tuner.
131 - ``V4L2_AUDCAP_AVL``
135 - Automatic Volume Level mode is supported.
139 .. tabularcolumns:: |p{6.6cm}|p{2.2cm}|p{8.7cm}|
143 .. flat-table:: Audio Mode Flags
151 - ``V4L2_AUDMODE_AVL``
161 On success 0 is returned, on error -1 and the ``errno`` variable is set
162 appropriately. The generic error codes are described at the
163 :ref:`Generic Error Codes <gen-errors>` chapter.
166 No audio inputs combine with the current video input, or the number
167 of the selected audio input is out of bounds or it does not combine.