1.. SPDX-License-Identifier: GFDL-1.1-no-invariants-or-later
2
3.. _video:
4
5************************
6Video Inputs and Outputs
7************************
8
9Video inputs and outputs are physical connectors of a device. These can
10be for example: RF connectors (antenna/cable), CVBS a.k.a. Composite
11Video, S-Video and RGB connectors. Camera sensors are also considered to
12be a video input. Video and VBI capture devices have inputs. Video and
13VBI output devices have outputs, at least one each. Radio devices have
14no video inputs or outputs.
15
16To learn about the number and attributes of the available inputs and
17outputs applications can enumerate them with the
18:ref:`VIDIOC_ENUMINPUT` and
19:ref:`VIDIOC_ENUMOUTPUT` ioctl, respectively. The
20struct :c:type:`v4l2_input` returned by the
21:ref:`VIDIOC_ENUMINPUT` ioctl also contains signal
22status information applicable when the current video input is queried.
23
24The :ref:`VIDIOC_G_INPUT <VIDIOC_G_INPUT>` and
25:ref:`VIDIOC_G_OUTPUT <VIDIOC_G_OUTPUT>` ioctls return the index of
26the current video input or output. To select a different input or output
27applications call the :ref:`VIDIOC_S_INPUT <VIDIOC_G_INPUT>` and
28:ref:`VIDIOC_S_OUTPUT <VIDIOC_G_OUTPUT>` ioctls. Drivers must
29implement all the input ioctls when the device has one or more inputs,
30all the output ioctls when the device has one or more outputs.
31
32Example: Information about the current video input
33==================================================
34
35.. code-block:: c
36
37    struct v4l2_input input;
38    int index;
39
40    if (-1 == ioctl(fd, VIDIOC_G_INPUT, &index)) {
41	perror("VIDIOC_G_INPUT");
42	exit(EXIT_FAILURE);
43    }
44
45    memset(&input, 0, sizeof(input));
46    input.index = index;
47
48    if (-1 == ioctl(fd, VIDIOC_ENUMINPUT, &input)) {
49	perror("VIDIOC_ENUMINPUT");
50	exit(EXIT_FAILURE);
51    }
52
53    printf("Current input: %s\\n", input.name);
54
55
56Example: Switching to the first video input
57===========================================
58
59.. code-block:: c
60
61    int index;
62
63    index = 0;
64
65    if (-1 == ioctl(fd, VIDIOC_S_INPUT, &index)) {
66	perror("VIDIOC_S_INPUT");
67	exit(EXIT_FAILURE);
68    }
69