1 .. SPDX-License-Identifier: GFDL-1.1-no-invariants-or-later
2 .. c:namespace:: V4L
3
4 .. _VIDIOC_G_AUDIO:
5
6 ************************************
7 ioctl VIDIOC_G_AUDIO, VIDIOC_S_AUDIO
8 ************************************
9
10 Name
11 ====
12
13 VIDIOC_G_AUDIO - VIDIOC_S_AUDIO - Query or select the current audio input and its attributes
14
15 Synopsis
16 ========
17
18 .. c:macro:: VIDIOC_G_AUDIO
19
20 ``int ioctl(int fd, VIDIOC_G_AUDIO, struct v4l2_audio *argp)``
21
22 .. c:macro:: VIDIOC_S_AUDIO
23
24 ``int ioctl(int fd, VIDIOC_S_AUDIO, const struct v4l2_audio *argp)``
25
26 Arguments
27 =========
28
29 ``fd``
30 File descriptor returned by :c:func:`open()`.
31
32 ``argp``
33 Pointer to struct :c:type:`v4l2_audio`.
34
35 Description
36 ===========
37
38 To query the current audio input applications zero out the ``reserved``
39 array of a struct :c:type:`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.
43
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 struct :c:type:`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.
51
52 .. tabularcolumns:: |p{4.4cm}|p{4.4cm}|p{8.5cm}|
53
54 .. c:type:: v4l2_audio
55
56 .. flat-table:: struct v4l2_audio
57 :header-rows: 0
58 :stub-columns: 0
59 :widths: 1 1 2
60
61 * - __u32
62 - ``index``
63 - Identifies the audio input, set by the driver or application.
64 * - __u8
65 - ``name``\ [32]
66 - Name of the audio input, a NUL-terminated ASCII string, for
67 example: "Line In". This information is intended for the user,
68 preferably the connector label on the device itself.
69 * - __u32
70 - ``capability``
71 - Audio capability flags, see :ref:`audio-capability`.
72 * - __u32
73 - ``mode``
74 - Audio mode flags set by drivers and applications (on
75 :ref:`VIDIOC_S_AUDIO <VIDIOC_G_AUDIO>` ioctl), see :ref:`audio-mode`.
76 * - __u32
77 - ``reserved``\ [2]
78 - Reserved for future extensions. Drivers and applications must set
79 the array to zero.
80
81
82 .. tabularcolumns:: |p{6.6cm}|p{2.2cm}|p{8.5cm}|
83
84 .. _audio-capability:
85
86 .. flat-table:: Audio Capability Flags
87 :header-rows: 0
88 :stub-columns: 0
89 :widths: 3 1 4
90
91 * - ``V4L2_AUDCAP_STEREO``
92 - 0x00001
93 - This is a stereo input. The flag is intended to automatically
94 disable stereo recording etc. when the signal is always monaural.
95 The API provides no means to detect if stereo is *received*,
96 unless the audio input belongs to a tuner.
97 * - ``V4L2_AUDCAP_AVL``
98 - 0x00002
99 - Automatic Volume Level mode is supported.
100
101
102 .. tabularcolumns:: |p{6.6cm}|p{2.2cm}|p{8.5cm}|
103
104 .. _audio-mode:
105
106 .. flat-table:: Audio Mode Flags
107 :header-rows: 0
108 :stub-columns: 0
109 :widths: 3 1 4
110
111 * - ``V4L2_AUDMODE_AVL``
112 - 0x00001
113 - AVL mode is on.
114
115 Return Value
116 ============
117
118 On success 0 is returned, on error -1 and the ``errno`` variable is set
119 appropriately. The generic error codes are described at the
120 :ref:`Generic Error Codes <gen-errors>` chapter.
121
122 EINVAL
123 No audio inputs combine with the current video input, or the number
124 of the selected audio input is out of bounds or it does not combine.
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