On 17/08/2020 14:09, Stefan Witzel wrote: > Hello, > > I am not a V4L developer so if this is not the right place to bring up > the issue please tell me who to contact instead. > The page [1] documents a problem with a particular device "Elgato Cam > Link 4K" which provides various format options among which most software > does not consciously pick the one which it implicitly expects leading to > problems. There is a software workaround, transcoding and looping > through a virtual device and a hardware fix flashing the problematic > profiles away. > However it appears to me that the most satisfactory solution is hinted > at in the sentence > >> I couldn't find any option in V4L to force selection of 'YUYV 4:2:2', so instead > > So my question is: what changes would be necessary to allow v4l2-ctl to > enforce a particular format and who would be the right person to ask to > make such changes? It's there already: v4l2-ctl -v pixelformat=YUYV That will do the trick. If you plug in the device and run 'v4l2-ctl -V', which pixelformat does it report? I would expect it to be YUYV since that's first in the list. If apps like Discord pick YU12 instead, then that's weird. That's something that the application does, and v4l2-ctl won't help with that. I.e., it appears to be an application bug. One other alternative is that the device has broken 4:2:0 support, i.e. it reports these formats, but they don't actually work. You can use qv4l2 or qvidcap to test if these 4:2:0 formats are working. Regards, Hans > > Best regards, > Stefan > > > [1] https://assortedhackery.com/patching-cam-link-to-play-nicer-on-linux/ >
