Damian Hobson-Garcia 70086fda22 v4l2src: Add support for cropping at capture source input
Add properties to control input cropping in the V4L2 device.
The input cropping is applied before composing the result to the
capture buffer.  By default the capture size will be set to the same
size as the crop region, but it can be scaled to a different output
frame size if supported by the V4L2 device.
If scaling is not supported, the cropped image will
be composed as is into the top-left corner of the capture buffer.

Part-of: <https://gitlab.freedesktop.org/gstreamer/gstreamer/-/merge_requests/1089>
2022-03-11 15:02:08 +00:00
..

v4l2 plugins
============

The idea is a bit the same as the idea for the v4l1 plugins. We want
one generic v4l2element, and a few child objects (probably only two:
v4l2src and v4l2sink):

                /-------- v4l2src
v4l2element ---=
                \-------- v4l2sink

Both v4l2src and v4l2sink have a uncompressed and a compressed
recording-/playback-mode. Since this is all part of v4l2, the 'client'
of these elements, i.e. an application using v4l2src/v4l2sink, will
hardly notice this. All capsnego stuff is done inside, and the plugin
knows which formats are compressed and which are not.

Please note that the v4l1 and the v4l2 plugins are *not* compatible
concerning properties. Naming has been kept the same where possible,
but in some cases, properties had to be removed or added to make
full use of v4l2.

V4L2 API: http://linux.bytesex.org/v4l2/.
          http://v4l2spec.bytesex.org/
          /usr/include/linux/videodev2.h or

Kernel patches available from
          http://dl.bytesex.org/patches/.

Articles:
          http://lwn.net/Articles/203924/