vidioc-g-audioout.rst (2990B)
1.. SPDX-License-Identifier: GFDL-1.1-no-invariants-or-later 2.. c:namespace:: V4L 3 4.. _VIDIOC_G_AUDOUT: 5 6************************************** 7ioctl VIDIOC_G_AUDOUT, VIDIOC_S_AUDOUT 8************************************** 9 10Name 11==== 12 13VIDIOC_G_AUDOUT - VIDIOC_S_AUDOUT - Query or select the current audio output 14 15Synopsis 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 26Arguments 27========= 28 29``fd`` 30 File descriptor returned by :c:func:`open()`. 31 32``argp`` 33 Pointer to struct :c:type:`v4l2_audioout`. 34 35Description 36=========== 37 38To query the current audio output applications zero out the ``reserved`` 39array of a struct :c:type:`v4l2_audioout` and call the 40``VIDIOC_G_AUDOUT`` 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 43output. 44 45Audio outputs have no writable properties. Nevertheless, to select the 46current audio output applications can initialize the ``index`` field and 47``reserved`` array (which in the future may contain writable properties) 48of a struct :c:type:`v4l2_audioout` structure and call the 49``VIDIOC_S_AUDOUT`` ioctl. Drivers switch to the requested output or 50return the ``EINVAL`` error code when the index is out of bounds. This is a 51write-only ioctl, it does not return the current audio output attributes 52as ``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 89Return Value 90============ 91 92On success 0 is returned, on error -1 and the ``errno`` variable is set 93appropriately. The generic error codes are described at the 94:ref:`Generic Error Codes <gen-errors>` chapter. 95 96EINVAL 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.