1 .. -*- coding: utf-8; mode: rst -*-
5 **************************************
6 ioctl VIDIOC_G_AUDOUT, VIDIOC_S_AUDOUT
7 **************************************
12 VIDIOC_G_AUDOUT - VIDIOC_S_AUDOUT - Query or select the current audio output
18 .. cpp:function:: int ioctl( int fd, int request, struct v4l2_audioout *argp )
20 .. cpp:function:: int ioctl( int fd, int request, const struct v4l2_audioout *argp )
27 File descriptor returned by :ref:`open() <func-open>`.
30 VIDIOC_G_AUDOUT, VIDIOC_S_AUDOUT
38 To query the current audio output applications zero out the ``reserved``
39 array of a struct :ref:`v4l2_audioout <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
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 :ref:`struct v4l2_audioout <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.
54 .. note:: Connectors on a TV card to loop back the received audio signal
55 to a sound card are not audio outputs in this sense.
60 .. flat-table:: struct v4l2_audioout
72 - Identifies the audio output, set by the driver or application.
80 - Name of the audio output, a NUL-terminated ASCII string, for
81 example: "Line Out". This information is intended for the user,
82 preferably the connector label on the device itself.
90 - Audio capability flags, none defined yet. Drivers must set this
99 - Audio mode, none defined yet. Drivers and applications (on
100 ``VIDIOC_S_AUDOUT``) must set this field to zero.
108 - Reserved for future extensions. Drivers and applications must set
115 On success 0 is returned, on error -1 and the ``errno`` variable is set
116 appropriately. The generic error codes are described at the
117 :ref:`Generic Error Codes <gen-errors>` chapter.
120 No audio outputs combine with the current video output, or the
121 number of the selected audio output is out of bounds or it does not