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