diff options
Diffstat (limited to 'Documentation/DocBook/v4l/common.xml')
-rw-r--r-- | Documentation/DocBook/v4l/common.xml | 35 |
1 files changed, 35 insertions, 0 deletions
diff --git a/Documentation/DocBook/v4l/common.xml b/Documentation/DocBook/v4l/common.xml index b1a81d2..c65f0ac 100644 --- a/Documentation/DocBook/v4l/common.xml +++ b/Documentation/DocBook/v4l/common.xml @@ -716,6 +716,41 @@ if (-1 == ioctl (fd, &VIDIOC-S-STD;, &std_id)) { } </programlisting> </example> + <section id="dv-timings"> + <title>Digital Video (DV) Timings</title> + <para> + The video standards discussed so far has 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 &v4l2-std-id; due to +the limited bits available, a new set of IOCTLs is added to set/get video timings at +the input and output: </para><itemizedlist> + <listitem> + <para>DV Presets: Digital Video (DV) presets. These are IDs representing a +video timing at the input/output. Presets are pre-defined timings implemented +by the hardware according to video standards. A __u32 data type is used to represent +a preset unlike the bit mask that is used in &v4l2-std-id; allowing future extensions +to support as many different presets as needed.</para> + </listitem> + <listitem> + <para>Custom DV Timings: This will allow applications to define more detailed +custom video timings for the interface. This includes parameters such as width, height, +polarities, frontporch, backporch etc. + </para> + </listitem> + </itemizedlist> + <para>To enumerate and query the attributes of DV presets supported by a device, +applications use the &VIDIOC-ENUM-DV-PRESETS; ioctl. To get the current DV preset, +applications use the &VIDIOC-G-DV-PRESET; ioctl and to set a preset they use the +&VIDIOC-S-DV-PRESET; ioctl.</para> + <para>To set custom DV timings for the device, applications use the +&VIDIOC-S-DV-TIMINGS; ioctl and to get current custom DV timings they use the +&VIDIOC-G-DV-TIMINGS; ioctl.</para> + <para>Applications can make use of the <xref linkend="input-capabilities" /> and +<xref linkend="output-capabilities"/> flags to decide what ioctls are available to set the +video timings for the device.</para> + </section> </section> &sub-controls; |