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media: Documentation: vivid.rst: Remove documentation for Capture Overlay

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Modifying documentation to remove 'Capture Overlay section' as
destructive capture overlay support was removed.

See commit ccaa9d50ca ("media: vivid: drop overlay support")

Signed-off-by: Dorcas Anono Litunya <anonolitunya@gmail.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
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Dorcas Anono Litunya 2024-06-24 12:52:57 +03:00 committed by Hans Verkuil
parent 3883822e17
commit 0bc9574a7a
1 changed files with 0 additions and 68 deletions
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Documentation/admin-guide/media/vivid.rst
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@ -1282,74 +1282,6 @@ data_offset to be non-zero, so this is a useful feature for testing applications
Video output will also honor any data_offset that the application set.
Capture Overlay
---------------
Note: capture overlay support is implemented primarily to test the existing
V4L2 capture overlay API. In practice few if any GPUs support such overlays
anymore, and neither are they generally needed anymore since modern hardware
is so much more capable. By setting flag 0x10000 in the node_types module
option the vivid driver will create a simple framebuffer device that can be
used for testing this API. Whether this API should be used for new drivers is
questionable.
This driver has support for a destructive capture overlay with bitmap clipping
and list clipping (up to 16 rectangles) capabilities. Overlays are not
supported for multiplanar formats. It also honors the struct v4l2_window field
setting: if it is set to FIELD_TOP or FIELD_BOTTOM and the capture setting is
FIELD_ALTERNATE, then only the top or bottom fields will be copied to the overlay.
The overlay only works if you are also capturing at that same time. This is a
vivid limitation since it copies from a buffer to the overlay instead of
filling the overlay directly. And if you are not capturing, then no buffers
are available to fill.
In addition, the pixelformat of the capture format and that of the framebuffer
must be the same for the overlay to work. Otherwise VIDIOC_OVERLAY will return
an error.
In order to really see what it going on you will need to create two vivid
instances: the first with a framebuffer enabled. You configure the capture
overlay of the second instance to use the framebuffer of the first, then
you start capturing in the second instance. For the first instance you setup
the output overlay for the video output, turn on video looping and capture
to see the blended framebuffer overlay that's being written to by the second
instance. This setup would require the following commands:
.. code-block:: none
$ sudo modprobe vivid n_devs=2 node_types=0x10101,0x1
$ v4l2-ctl -d1 --find-fb
/dev/fb1 is the framebuffer associated with base address 0x12800000
$ sudo v4l2-ctl -d2 --set-fbuf fb=1
$ v4l2-ctl -d1 --set-fbuf fb=1
$ v4l2-ctl -d0 --set-fmt-video=pixelformat='AR15'
$ v4l2-ctl -d1 --set-fmt-video-out=pixelformat='AR15'
$ v4l2-ctl -d2 --set-fmt-video=pixelformat='AR15'
$ v4l2-ctl -d0 -i2
$ v4l2-ctl -d2 -i2
$ v4l2-ctl -d2 -c horizontal_movement=4
$ v4l2-ctl -d1 --overlay=1
$ v4l2-ctl -d0 -c loop_video=1
$ v4l2-ctl -d2 --stream-mmap --overlay=1
And from another console:
.. code-block:: none
$ v4l2-ctl -d1 --stream-out-mmap
And yet another console:
.. code-block:: none
$ qv4l2
and start streaming.
As you can see, this is not for the faint of heart...
Output Overlay
--------------