HW accelerated VP9 decoding on RDNA2 causes freezes, stutters, and hangs in playback.

When in Firefox and using VAAPI, alt tabbing out of a video will cause it to hang and flicker for anywhere between 5 to 10 seconds every time. Using mpv and VAAPI will just generally stutter on VP9 based videos even without user input. Notably, these stutters and lost frames are not picked up by "Stats for nerds".

Recorded snippets of seen behavior: Youtube and alt tabbing and MPV stuttering

Used example VP9 video on youtube: https://www.youtube.com/watch?v=Gq9duUdnCfc

Used mpv command with problems: mpv "https://www.youtube.com/watch?v=Gq9duUdnCfc" --hwdec=vaapi

Noticed under kernels: linux-zen 6.6.0, linux-zen 6.6.1, and linux 6.6.1.

Dmesg: dmesg-log.txt

OpenGL: OpenGL renderer string: AMD Radeon RX 6950 XT (navi21, LLVM 16.0.6, DRM 3.54, 6.6.1)

Downstream issue: https://github.com/NixOS/nixpkgs/issues/269016

Please give advice/pointers for any further debug logs you would like, as dmesg shows no messages, and MOZ_LOG="FFmpegVideo:5" firefox does not show anything alarming at least to me.