Honestly, this shouldn’t even be a problem in the first place. I did all the A/B work to figure out the “problem” in the OP.
AMD’s not entirely without blame, either their driver or the card itself doesn’t like DXVA2-CB with 10-bit HEVC. Except DXVA2 might as well be obsolete in and of itself, along with DirectShow!
I’d understand if it was the older PMP that was “stuck” using DXVA2, but you kind of have to go out of your way to force it to use it! “Plex Classic” defaults to D3D11VA. LAV’s decoder (example) defaults to D3D11VA. Even when I use an OpenGL renderer in another app (tone mapping HDR->SDR in VLC = D3D11VA decode, drawn using OpenGL output) I don’t end up with these artifacts.
Plex overhauled and replaced their desktop app and dropped back from Media Foundation to DirectShow video decoding…
The worst part is I don’t even think it was an intentional change. Someone overlooked some parameter somewhere. If the “guts” are still the same (they are, it’s still mpv, is it not?) getting it back to using D3D11VA should’ve been as trivial as asking mpv to use D3D11VA, which we know still works on a standalone instance of mpv, and works correctly.
