0001 .. SPDX-License-Identifier: GFDL-1.1-no-invariants-or-later
0002
0003 .. _dv-timings:
0004
0005 **************************
0006 Digital Video (DV) Timings
0007 **************************
0008
0009 The video standards discussed so far have been dealing with Analog TV
0010 and the corresponding video timings. Today there are many more different
0011 hardware interfaces such as High Definition TV interfaces (HDMI), VGA,
0012 DVI connectors etc., that carry video signals and there is a need to
0013 extend the API to select the video timings for these interfaces. Since
0014 it is not possible to extend the :ref:`v4l2_std_id <v4l2-std-id>`
0015 due to the limited bits available, a new set of ioctls was added to
0016 set/get video timings at the input and output.
0017
0018 These ioctls deal with the detailed digital video timings that define
0019 each video format. This includes parameters such as the active video
0020 width and height, signal polarities, frontporches, backporches, sync
0021 widths etc. The ``linux/v4l2-dv-timings.h`` header can be used to get
0022 the timings of the formats in the :ref:`cea861` and :ref:`vesadmt`
0023 standards.
0024
0025 To enumerate and query the attributes of the DV timings supported by a
0026 device applications use the
0027 :ref:`VIDIOC_ENUM_DV_TIMINGS` and
0028 :ref:`VIDIOC_DV_TIMINGS_CAP` ioctls. To set
0029 DV timings for the device applications use the
0030 :ref:`VIDIOC_S_DV_TIMINGS <VIDIOC_G_DV_TIMINGS>` ioctl and to get
0031 current DV timings they use the
0032 :ref:`VIDIOC_G_DV_TIMINGS <VIDIOC_G_DV_TIMINGS>` ioctl. To detect
0033 the DV timings as seen by the video receiver applications use the
0034 :ref:`VIDIOC_QUERY_DV_TIMINGS` ioctl.
0035
0036 Applications can make use of the :ref:`input-capabilities` and
0037 :ref:`output-capabilities` flags to determine whether the digital
0038 video ioctls can be used with the given input or output.
