SOLVED: Unstable: Firefox/Chromium not playing AV1

[TheDreadPirate]

I'm using a debian distro called DietPie, since I have an Intel Arc gpu I had to update the lastet kernel "6.10.6+bpo-amd64" to make it work.
All x264 transcoding works without any problem.

I've been monitoring the GPU usage when I watch a video in AV1 with Jellyfin Media Player (which is where it works).
If the video is displayed in original quality the GPU usage is 0% (obviously). When I reduce the quality the GPU starts working randomly, that is, it uses it intermittently, making it appear and disappear from the monitor (screenshots). But when it's x264 the GPU usage is constant. This causes the video to stutter, jump, or freeze while the audio continues to play.

Do you think it's too early to use AV1?

I encode all my media in AV1 with ffmpeg.  And for my media still in HEVC, MPEG2, and older codecs, they get transcoded to AV1 no problem.  No stuttering.  Most of my devices can direct play it, including Chrome/Chromium.

I spun up my 10.10 unstable container and I also wasn't able to reproduce your problem.  Both for direct streaming (video direct played, audio transcoded), full direct play, and full transcodes.

I'm not familiar with Fastflix.  I've always used Handbrake on Windows.  Maybe Fastflix is doing something during encoding that is breaking the video?

Give Handbrake a try.