39 строки
1.7 KiB
ReStructuredText
39 строки
1.7 KiB
ReStructuredText
.. -*- coding: utf-8; mode: rst -*-
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.. _dv-timings:
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**************************
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Digital Video (DV) Timings
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**************************
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The video standards discussed so far have been dealing with Analog TV
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and the corresponding video timings. Today there are many more different
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hardware interfaces such as High Definition TV interfaces (HDMI), VGA,
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DVI connectors etc., that carry video signals and there is a need to
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extend the API to select the video timings for these interfaces. Since
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it is not possible to extend the :ref:`v4l2_std_id <v4l2-std-id>`
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due to the limited bits available, a new set of ioctls was added to
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set/get video timings at the input and output.
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These ioctls deal with the detailed digital video timings that define
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each video format. This includes parameters such as the active video
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width and height, signal polarities, frontporches, backporches, sync
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widths etc. The ``linux/v4l2-dv-timings.h`` header can be used to get
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the timings of the formats in the :ref:`cea861` and :ref:`vesadmt`
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standards.
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To enumerate and query the attributes of the DV timings supported by a
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device applications use the
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:ref:`VIDIOC_ENUM_DV_TIMINGS` and
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:ref:`VIDIOC_DV_TIMINGS_CAP` ioctls. To set
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DV timings for the device applications use the
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:ref:`VIDIOC_S_DV_TIMINGS <VIDIOC_G_DV_TIMINGS>` ioctl and to get
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current DV timings they use the
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:ref:`VIDIOC_G_DV_TIMINGS <VIDIOC_G_DV_TIMINGS>` ioctl. To detect
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the DV timings as seen by the video receiver applications use the
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:ref:`VIDIOC_QUERY_DV_TIMINGS` ioctl.
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Applications can make use of the :ref:`input-capabilities` and
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:ref:`output-capabilities` flags to determine whether the digital
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video ioctls can be used with the given input or output.
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