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documentation: media: vivid: Update documentation on vivid loopback support

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Modify section "Video and Sliced VBI Looping" in Documentation to explain
the vivid loopback support for video across multiple vivid instances.
Previous documentation is out-of-date as it was explaining looping in a
single vivid instance only.

Also, in "Some Future Improvements" the item "Add support to loop
from a specific output to a specific input across vivid instances"
can be dropped since that's now implemented.

Signed-off-by: Dorcas Anono Litunya <anonolitunya@gmail.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
This commit is contained in:
Dorcas Anono Litunya 2024-06-24 12:53:06 +03:00 committed by Hans Verkuil
parent 4c4dacb052
commit f5306b757c
1 changed files with 25 additions and 19 deletions
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44
Documentation/admin-guide/media/vivid.rst
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@ -1135,27 +1135,33 @@ Metadata Capture Controls
if set, then the generated metadata stream contains Source Clock information. if set, then the generated metadata stream contains Source Clock information.
Video and Sliced VBI Looping Video, Sliced VBI and HDMI CEC Looping
---------------------------- --------------------------------------
The vivid driver supports looping of video output to video input, and VBI Video Looping functionality is supported for devices created by the same
output to VBI input. For video/VBI looping this emulates as if a cable was vivid driver instance, as well as across multiple instances of the vivid driver.
hooked up between the output and input connector. So video and VBI looping The vivid driver supports looping of video and Sliced VBI data between an S-Video output
is only supported between S-Video and HDMI inputs and outputs. and an S-Video input. It also supports looping of video and HDMI CEC data between an
VBI is only valid for S-Video as it makes no sense for HDMI. HDMI output and an HDMI input.
Looping is currently supported only between devices created by the same To enable looping, set the 'HDMI/S-Video XXX-N Is Connected To' control(s) to select
vivid driver instance. whether an input uses the Test Pattern Generator, or is disconnected, or is connected
to an output. An input can be connected to an output from any vivid instance.
The inputs and outputs are numbered XXX-N where XXX is the vivid instance number
(see module option n_devs). If there is only one vivid instance (the default), then
XXX will be 000. And N is the Nth S-Video/HDMI input or output of that instance.
If vivid is loaded without module options, then you can connect the S-Video 000-0 input
to the S-Video 000-0 output, or the HDMI 000-0 input to the HDMI 000-0 output.
This is the equivalent of connecting or disconnecting a cable between an input and an
output in a physical device.
The way to enable video/VBI looping is currently fairly crude. A 'Loop Video' If an 'HDMI/S-Video XXX-N Is Connected To' control selected an output, then the video
control is available in the "Vivid" control class of the video output will be looped to the video input provided that:
capture and VBI capture devices. When checked the video looping will be enabled.
Once enabled any video S-Video or HDMI input will show a static test pattern
until the video output has started. At that time the video output will be
looped to the video input provided that:
- the input type matches the output type. So the HDMI input cannot receive - the currently selected input matches the input indicated by the control name.
video from the S-Video output.
- in the vivid instance of the output connector, the currently selected output matches
the output indicated by the control's value.
- the video resolution of the video input must match that of the video output. - the video resolution of the video input must match that of the video output.
So it is not possible to loop a 50 Hz (720x576) S-Video output to a 60 Hz So it is not possible to loop a 50 Hz (720x576) S-Video output to a 60 Hz
@ -1182,6 +1188,8 @@ looped to the video input provided that:
"DV Timings Signal Mode" for the HDMI input should be configured so that a "DV Timings Signal Mode" for the HDMI input should be configured so that a
valid signal is passed to the video input. valid signal is passed to the video input.
If any condition is not valid, then the 'Noise' test pattern is shown.
The framerates do not have to match, although this might change in the future. The framerates do not have to match, although this might change in the future.
By default you will see the OSD text superimposed on top of the looped video. By default you will see the OSD text superimposed on top of the looped video.
@ -1344,8 +1352,6 @@ Just as a reminder and in no particular order:
- Add ARGB888 overlay support: better testing of the alpha channel - Add ARGB888 overlay support: better testing of the alpha channel
- Improve pixel aspect support in the tpg code by passing a real v4l2_fract - Improve pixel aspect support in the tpg code by passing a real v4l2_fract
- Use per-queue locks and/or per-device locks to improve throughput - Use per-queue locks and/or per-device locks to improve throughput
- Add support to loop from a specific output to a specific input across
vivid instances
- The SDR radio should use the same 'frequencies' for stations as the normal - The SDR radio should use the same 'frequencies' for stations as the normal
radio receiver, and give back noise if the frequency doesn't match up with radio receiver, and give back noise if the frequency doesn't match up with
a station frequency a station frequency