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 .. cpp:function:: int ioctl( int fd, int request, struct v4l2_audio *argp )
20 .. cpp:function:: int ioctl( int fd, int request, const struct v4l2_audio *argp )
27 File descriptor returned by :ref:`open() <func-open>`.
30 VIDIOC_G_AUDIO, VIDIOC_S_AUDIO
38 To query the current audio input applications zero out the ``reserved``
39 array of a struct :ref:`v4l2_audio <v4l2-audio>` and call the
40 :ref:`VIDIOC_G_AUDIO <VIDIOC_G_AUDIO>` ioctl with a pointer to this structure. Drivers fill
41 the rest of the structure or return an ``EINVAL`` error code when the device
42 has no audio inputs, or none which combine with the current video input.
44 Audio inputs have one writable property, the audio mode. To select the
45 current audio input *and* change the audio mode, applications initialize
46 the ``index`` and ``mode`` fields, and the ``reserved`` array of a
47 :ref:`struct v4l2_audio <v4l2-audio>` structure and call the :ref:`VIDIOC_S_AUDIO <VIDIOC_G_AUDIO>`
48 ioctl. Drivers may switch to a different audio mode if the request
49 cannot be satisfied. However, this is a write-only ioctl, it does not
50 return the actual new audio mode.
55 .. tabularcolumns:: |p{4.4cm}|p{4.4cm}|p{8.7cm}|
57 .. flat-table:: struct v4l2_audio
69 - Identifies the audio input, set by the driver or application.
77 - Name of the audio input, a NUL-terminated ASCII string, for
78 example: "Line In". This information is intended for the user,
79 preferably the connector label on the device itself.
87 - Audio capability flags, see :ref:`audio-capability`.
95 - Audio mode flags set by drivers and applications (on
96 :ref:`VIDIOC_S_AUDIO <VIDIOC_G_AUDIO>` ioctl), see :ref:`audio-mode`.
104 - Reserved for future extensions. Drivers and applications must set
109 .. _audio-capability:
111 .. tabularcolumns:: |p{6.6cm}|p{2.2cm}|p{8.7cm}|
113 .. flat-table:: Audio Capability Flags
121 - ``V4L2_AUDCAP_STEREO``
125 - This is a stereo input. The flag is intended to automatically
126 disable stereo recording etc. when the signal is always monaural.
127 The API provides no means to detect if stereo is *received*,
128 unless the audio input belongs to a tuner.
132 - ``V4L2_AUDCAP_AVL``
136 - Automatic Volume Level mode is supported.
142 .. tabularcolumns:: |p{6.6cm}|p{2.2cm}|p{8.7cm}|
144 .. flat-table:: Audio Mode Flags
152 - ``V4L2_AUDMODE_AVL``
162 On success 0 is returned, on error -1 and the ``errno`` variable is set
163 appropriately. The generic error codes are described at the
164 :ref:`Generic Error Codes <gen-errors>` chapter.
167 No audio inputs combine with the current video input, or the number
168 of the selected audio input is out of bounds or it does not combine.