Porting xf86-video-v4l to use textured video
Mauro Carvalho Chehab
mchehab at infradead.org
Tue Feb 8 02:39:24 PST 2011
I'm currently working on make xawtv and xf86-video-v4l fully functional, in order to
allow us to test the overlay part of the V4L2 API.
I just sent a big patch replacing the old API to the new one, so the driver should be
working now. However, only a very few set of drivers will benefit from it, as the
driver still uses the deprecated overlays at the Xv extension.
I suspect that it shouldn't be hard to convert it to use textured video.
What the driver basically does is to check the Xv extension of the screen, using
xf86XVQueryOffscreenImages(), selecting a FOURCC mode that it is compatible with
a video capture board. Then, it passes a memory address at the video board where
the overlay should be placed to the kernel driver. The kernel driver will then
program the device's DMA to do data transfer from the capture board into the
For it to work with textured video, probably, all we need to to is to replace the
probe code that gets the XV info from the PutVideo operation, making it work
with the PutImage operation, but I'm not sure how to do it.
Could someone give me some pointers on how to do such change?
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