ffmpeg: force-disable zerocopy for RPi OMX patch

[nmschulte]

Resolves #2523 and likely #2542.

[ccrisan]

Thanks! @jasaw do you think this should be enough for us to use the latest ffmpeg with OMX?

[JohanD78]

OMX works fine with no artifacts with the dev201025 release. Verified on both Pi3 and Pi4

[jasaw]

It is very interesting that we still need to patch ffmpeg to disable zerocopy because motion already disables zerocopy here: https://github.com/Motion-Project/motion/blob/0faf44fefb4126722c44020269a7593994c97102/src/ffmpeg.c#L846
Something else must be broken in ffmpeg if disabling zerocopy via av_dict_set doesn't work. :-(

[nmschulte]

I'm not sure the issue is caused by this commit, but with my build, my RPi3 video seems to freeze/break. It did not do this with the same/similar configuration on 20200606 build. Rebooting seems to resolve the issue, but motion detection etc. seems to not work when it's in this frozen/broken state.

[PhinPhin]

with the latest build I seem to got rid of the artefacts, but I now have broken videofiles every now and then, I can download the files but neither I can play it nor can MotionEyeOS create thumbnails:

Very annoying, since I use motion-detection to start recording and the motion-events are kind of important. Is there another issue that would explain this?