| .. -*- coding: utf-8; mode: rst -*- |
| |
| .. _video: |
| |
| ************************ |
| Video Inputs and Outputs |
| ************************ |
| |
| Video inputs and outputs are physical connectors of a device. These can |
| be for example RF connectors (antenna/cable), CVBS a.k.a. Composite |
| Video, S-Video or RGB connectors. Video and VBI capture devices have |
| inputs. Video and VBI output devices have outputs, at least one each. |
| Radio devices have no video inputs or outputs. |
| |
| To learn about the number and attributes of the available inputs and |
| outputs applications can enumerate them with the |
| :ref:`VIDIOC_ENUMINPUT` and |
| :ref:`VIDIOC_ENUMOUTPUT` ioctl, respectively. The |
| struct :ref:`v4l2_input <v4l2-input>` returned by the |
| :ref:`VIDIOC_ENUMINPUT` ioctl also contains signal |
| :status information applicable when the current video input is queried. |
| |
| The :ref:`VIDIOC_G_INPUT <VIDIOC_G_INPUT>` and |
| :ref:`VIDIOC_G_OUTPUT <VIDIOC_G_OUTPUT>` ioctls return the index of |
| the current video input or output. To select a different input or output |
| applications call the :ref:`VIDIOC_S_INPUT <VIDIOC_G_INPUT>` and |
| :ref:`VIDIOC_S_OUTPUT <VIDIOC_G_OUTPUT>` ioctls. Drivers must |
| implement all the input ioctls when the device has one or more inputs, |
| all the output ioctls when the device has one or more outputs. |
| |
| .. code-block:: c |
| :caption: Example 1.1. Information about the current video input |
| |
| struct v4l2_input input; |
| int index; |
| |
| if (-1 == ioctl(fd, VIDIOC_G_INPUT, &index)) { |
| perror("VIDIOC_G_INPUT"); |
| exit(EXIT_FAILURE); |
| } |
| |
| memset(&input, 0, sizeof(input)); |
| input.index = index; |
| |
| if (-1 == ioctl(fd, VIDIOC_ENUMINPUT, &input)) { |
| perror("VIDIOC_ENUMINPUT"); |
| exit(EXIT_FAILURE); |
| } |
| |
| printf("Current input: %s\\n", input.name); |
| |
| |
| .. code-block:: c |
| :caption: Example 1.2. Switching to the first video input |
| |
| int index; |
| |
| index = 0; |
| |
| if (-1 == ioctl(fd, VIDIOC_S_INPUT, &index)) { |
| perror("VIDIOC_S_INPUT"); |
| exit(EXIT_FAILURE); |
| } |