Stuttering and delays with AV1 decoding in Mesa 24 using VAAPI on AMD Phoenix, works fine on Mesa 23
Mesa 24 introduced a change to AV1 hardware decoding on AMD that is causing delays/lockups in vending of decoded frames to a VASurface with 2160p videos. If you start decoding a video stream, everything goes fine for about 1 second, then decoding stops for no reason for 1-1.5 seconds, then picks back up. It's intermittent lockups from there. The delays are repeatable and triggered by the arrangement of data in the video file, presumably. The issue is definitely within the libva/VAAPI realm, as just decoding without using the frames for anything still shows the problem. Decoding works fast and without issue on Mesa 23.3.6, which appears to be the last working version.
I tested this with a couple AV1 2160p videos in both 8 and 10 bit, both with B-frames. One was encoded with an Intel 12th gen HW encoder by me with a reasonable 60 frame GOP, and the other was ripped from the most popular video streaming site so it's got a very long GOP. Both have the same problem, so the bit depth or GOP length has nothing to do with it. It's possible the issue is specific to the Phoenix/7940HS APU. I haven't noticed any problems with HEVC or H.264 videos. Again, no problems on Mesa 23.