Hello! I'm here as a Gentoo Linux developer. We support a very broad range of hardware, but our RPi support has been a bit lacking in recent years, with old versions of the legacy stack still present in our package repository. I get the impression that not many people use video on RPi under Gentoo, but I'd like to change that.
I've started putting the changes together to throw out the legacy stack, and I've been testing the video performance against mpv and Kodi. I quickly became aware that vanilla ffmpeg was not going to cut it, even for some 1080p videos on a Pi 3b. I tried various branches from various forks against 6.0 and 6.1, and while these generally worked for mpv, only jc-kynesim's test/6.0.1/main branch worked for Kodi.
I have seen that you only apply this patchset specifically for your RPi build, while you apply Kwiboo's v4l2-request and lrusak's v4l2-drmprime patchsets on most other devices. I know that these patchsets cannot be combined, and I can see that while there are some similarities, the RPi set is not a superset. Does this mean the RPi patchset is useless on other devices? Or perhaps you're trying not to deviate from upstream more than you need to on those devices? Being a source-based distro, Gentoo does not need to force the same patches on everyone, but I'd rather only have one set to deal with here, if possible.
Carrying these patches has the potential to make life difficult for Gentoo maintainers, as we may want to move on from older ffmpeg versions before these patchsets are available for newer versions. I did start rebasing jc-kynesim's branch against 6.1, and while I didn't get stuck, it looked like it was going to take a while, and I didn't want to continue without knowing whether I would succeed unless I really had to. 6.0 is still quite recent though, so I'm not too worried.
I hope and believe that you are still interested in getting these efforts upstreamed. I appreciate this has been a long road, and there may still be some distance to go yet. I don't know whether I can help in this regard, but perhaps another distro adopting this puts some weight behind it. What is the strategy when we have seemingly competing patchsets though?