1.. -*- coding: utf-8; mode: rst -*-
2
3.. _VIDIOC_G_AUDIO:
4
5************************************
6ioctl VIDIOC_G_AUDIO, VIDIOC_S_AUDIO
7************************************
8
9Name
10====
11
12VIDIOC_G_AUDIO - VIDIOC_S_AUDIO - Query or select the current audio input and its attributes
13
14
15Synopsis
16========
17
18.. c:function:: int ioctl( int fd, VIDIOC_G_AUDIO, struct v4l2_audio *argp )
19    :name: VIDIOC_G_AUDIO
20
21.. c:function:: int ioctl( int fd, VIDIOC_S_AUDIO, const struct v4l2_audio *argp )
22    :name: VIDIOC_S_AUDIO
23
24
25Arguments
26=========
27
28``fd``
29    File descriptor returned by :ref:`open() <func-open>`.
30
31``argp``
32    Pointer to struct :c:type:`v4l2_audio`.
33
34
35Description
36===========
37
38To query the current audio input applications zero out the ``reserved``
39array 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
41the rest of the structure or return an ``EINVAL`` error code when the device
42has no audio inputs, or none which combine with the current video input.
43
44Audio inputs have one writable property, the audio mode. To select the
45current audio input *and* change the audio mode, applications initialize
46the ``index`` and ``mode`` fields, and the ``reserved`` array of a
47struct :c:type:`v4l2_audio` structure and call the :ref:`VIDIOC_S_AUDIO <VIDIOC_G_AUDIO>`
48ioctl. Drivers may switch to a different audio mode if the request
49cannot be satisfied. However, this is a write-only ioctl, it does not
50return the actual new audio mode.
51
52
53.. tabularcolumns:: |p{4.4cm}|p{4.4cm}|p{8.7cm}|
54
55.. c:type:: v4l2_audio
56
57.. flat-table:: struct v4l2_audio
58    :header-rows:  0
59    :stub-columns: 0
60    :widths:       1 1 2
61
62    * - __u32
63      - ``index``
64      - Identifies the audio input, set by the driver or application.
65    * - __u8
66      - ``name``\ [32]
67      - Name of the audio input, a NUL-terminated ASCII string, for
68	example: "Line In". This information is intended for the user,
69	preferably the connector label on the device itself.
70    * - __u32
71      - ``capability``
72      - Audio capability flags, see :ref:`audio-capability`.
73    * - __u32
74      - ``mode``
75      - Audio mode flags set by drivers and applications (on
76	:ref:`VIDIOC_S_AUDIO <VIDIOC_G_AUDIO>` ioctl), see :ref:`audio-mode`.
77    * - __u32
78      - ``reserved``\ [2]
79      - Reserved for future extensions. Drivers and applications must set
80	the array to zero.
81
82
83
84.. tabularcolumns:: |p{6.6cm}|p{2.2cm}|p{8.7cm}|
85
86.. _audio-capability:
87
88.. flat-table:: Audio Capability Flags
89    :header-rows:  0
90    :stub-columns: 0
91    :widths:       3 1 4
92
93    * - ``V4L2_AUDCAP_STEREO``
94      - 0x00001
95      - This is a stereo input. The flag is intended to automatically
96	disable stereo recording etc. when the signal is always monaural.
97	The API provides no means to detect if stereo is *received*,
98	unless the audio input belongs to a tuner.
99    * - ``V4L2_AUDCAP_AVL``
100      - 0x00002
101      - Automatic Volume Level mode is supported.
102
103
104
105.. tabularcolumns:: |p{6.6cm}|p{2.2cm}|p{8.7cm}|
106
107.. _audio-mode:
108
109.. flat-table:: Audio Mode Flags
110    :header-rows:  0
111    :stub-columns: 0
112    :widths:       3 1 4
113
114    * - ``V4L2_AUDMODE_AVL``
115      - 0x00001
116      - AVL mode is on.
117
118
119Return Value
120============
121
122On success 0 is returned, on error -1 and the ``errno`` variable is set
123appropriately. The generic error codes are described at the
124:ref:`Generic Error Codes <gen-errors>` chapter.
125
126EINVAL
127    No audio inputs combine with the current video input, or the number
128    of the selected audio input is out of bounds or it does not combine.
129