0001 .. SPDX-License-Identifier: GFDL-1.1-no-invariants-or-later
0002
0003 .. _video:
0004
0005 ************************
0006 Video Inputs and Outputs
0007 ************************
0008
0009 Video inputs and outputs are physical connectors of a device. These can
0010 be for example: RF connectors (antenna/cable), CVBS a.k.a. Composite
0011 Video, S-Video and RGB connectors. Camera sensors are also considered to
0012 be a video input. Video and VBI capture devices have inputs. Video and
0013 VBI output devices have outputs, at least one each. Radio devices have
0014 no video inputs or outputs.
0015
0016 To learn about the number and attributes of the available inputs and
0017 outputs applications can enumerate them with the
0018 :ref:`VIDIOC_ENUMINPUT` and
0019 :ref:`VIDIOC_ENUMOUTPUT` ioctl, respectively. The
0020 struct :c:type:`v4l2_input` returned by the
0021 :ref:`VIDIOC_ENUMINPUT` ioctl also contains signal
0022 status information applicable when the current video input is queried.
0023
0024 The :ref:`VIDIOC_G_INPUT <VIDIOC_G_INPUT>` and
0025 :ref:`VIDIOC_G_OUTPUT <VIDIOC_G_OUTPUT>` ioctls return the index of
0026 the current video input or output. To select a different input or output
0027 applications call the :ref:`VIDIOC_S_INPUT <VIDIOC_G_INPUT>` and
0028 :ref:`VIDIOC_S_OUTPUT <VIDIOC_G_OUTPUT>` ioctls. Drivers must
0029 implement all the input ioctls when the device has one or more inputs,
0030 all the output ioctls when the device has one or more outputs.
0031
0032 Example: Information about the current video input
0033 ==================================================
0034
0035 .. code-block:: c
0036
0037 struct v4l2_input input;
0038 int index;
0039
0040 if (-1 == ioctl(fd, VIDIOC_G_INPUT, &index)) {
0041 perror("VIDIOC_G_INPUT");
0042 exit(EXIT_FAILURE);
0043 }
0044
0045 memset(&input, 0, sizeof(input));
0046 input.index = index;
0047
0048 if (-1 == ioctl(fd, VIDIOC_ENUMINPUT, &input)) {
0049 perror("VIDIOC_ENUMINPUT");
0050 exit(EXIT_FAILURE);
0051 }
0052
0053 printf("Current input: %s\\n", input.name);
0054
0055
0056 Example: Switching to the first video input
0057 ===========================================
0058
0059 .. code-block:: c
0060
0061 int index;
0062
0063 index = 0;
0064
0065 if (-1 == ioctl(fd, VIDIOC_S_INPUT, &index)) {
0066 perror("VIDIOC_S_INPUT");
0067 exit(EXIT_FAILURE);
0068 }
