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