1 .. Permission is granted to copy, distribute and/or modify this
2 .. document under the terms of the GNU Free Documentation License,
3 .. Version 1.1 or any later version published by the Free Software
4 .. Foundation, with no Invariant Sections, no Front-Cover Texts
5 .. and no Back-Cover Texts. A copy of the license is included at
6 .. Documentation/media/uapi/fdl-appendix.rst.
8 .. TODO: replace it to GFDL-1.1-or-later WITH no-invariant-sections
12 ************************************
13 ioctl VIDIOC_G_AUDIO, VIDIOC_S_AUDIO
14 ************************************
19 VIDIOC_G_AUDIO - VIDIOC_S_AUDIO - Query or select the current audio input and its attributes
25 .. c:function:: int ioctl( int fd, VIDIOC_G_AUDIO, struct v4l2_audio *argp )
28 .. c:function:: int ioctl( int fd, VIDIOC_S_AUDIO, const struct v4l2_audio *argp )
36 File descriptor returned by :ref:`open() <func-open>`.
39 Pointer to struct :c:type:`v4l2_audio`.
45 To query the current audio input applications zero out the ``reserved``
46 array of a struct :c:type:`v4l2_audio` and call the
47 :ref:`VIDIOC_G_AUDIO <VIDIOC_G_AUDIO>` ioctl with a pointer to this structure. Drivers fill
48 the rest of the structure or return an ``EINVAL`` error code when the device
49 has no audio inputs, or none which combine with the current video input.
51 Audio inputs have one writable property, the audio mode. To select the
52 current audio input *and* change the audio mode, applications initialize
53 the ``index`` and ``mode`` fields, and the ``reserved`` array of a
54 struct :c:type:`v4l2_audio` structure and call the :ref:`VIDIOC_S_AUDIO <VIDIOC_G_AUDIO>`
55 ioctl. Drivers may switch to a different audio mode if the request
56 cannot be satisfied. However, this is a write-only ioctl, it does not
57 return the actual new audio mode.
60 .. tabularcolumns:: |p{4.4cm}|p{4.4cm}|p{8.7cm}|
62 .. c:type:: v4l2_audio
64 .. flat-table:: struct v4l2_audio
71 - Identifies the audio input, set by the driver or application.
74 - Name of the audio input, a NUL-terminated ASCII string, for
75 example: "Line In". This information is intended for the user,
76 preferably the connector label on the device itself.
79 - Audio capability flags, see :ref:`audio-capability`.
82 - Audio mode flags set by drivers and applications (on
83 :ref:`VIDIOC_S_AUDIO <VIDIOC_G_AUDIO>` ioctl), see :ref:`audio-mode`.
86 - Reserved for future extensions. Drivers and applications must set
91 .. tabularcolumns:: |p{6.6cm}|p{2.2cm}|p{8.7cm}|
95 .. flat-table:: Audio Capability Flags
100 * - ``V4L2_AUDCAP_STEREO``
102 - This is a stereo input. The flag is intended to automatically
103 disable stereo recording etc. when the signal is always monaural.
104 The API provides no means to detect if stereo is *received*,
105 unless the audio input belongs to a tuner.
106 * - ``V4L2_AUDCAP_AVL``
108 - Automatic Volume Level mode is supported.
112 .. tabularcolumns:: |p{6.6cm}|p{2.2cm}|p{8.7cm}|
116 .. flat-table:: Audio Mode Flags
121 * - ``V4L2_AUDMODE_AVL``
129 On success 0 is returned, on error -1 and the ``errno`` variable is set
130 appropriately. The generic error codes are described at the
131 :ref:`Generic Error Codes <gen-errors>` chapter.
134 No audio inputs combine with the current video input, or the number
135 of the selected audio input is out of bounds or it does not combine.