1 .. SPDX-License-Identifier: GFDL-1.1-no-invariants-or-later
2 .. c:namespace:: V4L
3
4 .. _VIDIOC_G_AUDOUT:
5
6 **************************************
7 ioctl VIDIOC_G_AUDOUT, VIDIOC_S_AUDOUT
8 **************************************
9
10 Name
11 ====
12
13 VIDIOC_G_AUDOUT - VIDIOC_S_AUDOUT - Query or select the current audio output
14
15 Synopsis
16 ========
17
18 .. c:macro:: VIDIOC_G_AUDOUT
19
20 ``int ioctl(int fd, VIDIOC_G_AUDOUT, struct v4l2_audioout *argp)``
21
22 .. c:macro:: VIDIOC_S_AUDOUT
23
24 ``int ioctl(int fd, VIDIOC_S_AUDOUT, const struct v4l2_audioout *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_audioout`.
34
35 Description
36 ===========
37
38 To query the current audio output applications zero out the ``reserved``
39 array of a struct :c:type:`v4l2_audioout` and call the
40 ``VIDIOC_G_AUDOUT`` 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
43 output.
44
45 Audio outputs have no writable properties. Nevertheless, to select the
46 current audio output applications can initialize the ``index`` field and
47 ``reserved`` array (which in the future may contain writable properties)
48 of a struct :c:type:`v4l2_audioout` structure and call the
49 ``VIDIOC_S_AUDOUT`` ioctl. Drivers switch to the requested output or
50 return the ``EINVAL`` error code when the index is out of bounds. This is a
51 write-only ioctl, it does not return the current audio output attributes
52 as ``VIDIOC_G_AUDOUT`` does.
53
54 .. note::
55
56 Connectors on a TV card to loop back the received audio signal
57 to a sound card are not audio outputs in this sense.
58
59 .. c:type:: v4l2_audioout
60
61 .. tabularcolumns:: |p{4.4cm}|p{4.4cm}|p{8.5cm}|
62
63 .. flat-table:: struct v4l2_audioout
64 :header-rows: 0
65 :stub-columns: 0
66 :widths: 1 1 2
67
68 * - __u32
69 - ``index``
70 - Identifies the audio output, set by the driver or application.
71 * - __u8
72 - ``name``\ [32]
73 - Name of the audio output, a NUL-terminated ASCII string, for
74 example: "Line Out". This information is intended for the user,
75 preferably the connector label on the device itself.
76 * - __u32
77 - ``capability``
78 - Audio capability flags, none defined yet. Drivers must set this
79 field to zero.
80 * - __u32
81 - ``mode``
82 - Audio mode, none defined yet. Drivers and applications (on
83 ``VIDIOC_S_AUDOUT``) must set this field to zero.
84 * - __u32
85 - ``reserved``\ [2]
86 - Reserved for future extensions. Drivers and applications must set
87 the array to zero.
88
89 Return Value
90 ============
91
92 On success 0 is returned, on error -1 and the ``errno`` variable is set
93 appropriately. The generic error codes are described at the
94 :ref:`Generic Error Codes <gen-errors>` chapter.
95
96 EINVAL
97 No audio outputs combine with the current video output, or the
98 number of the selected audio output is out of bounds or it does not
99 combine.
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