It seems that LAVfilters v0.73 / MPC-HC v1.8.3 improves AV1 performance a tad (~20% faster), but it's multi-threaded utilization is still poor (only ~26% utilization with 4c/8t Nehalem).
The biggest benefit I found is that only using dual core no longer completely tanks performance.
Utilizing a Nehalem Xeon x3470, I had the following performance when trying to decode the 1080p AV1 video-only stream from
Gus Kenworthy & Tom Wallisch X Games Slopestyle GoPro Preview in MPC-HC v1.8.3 64bit:
- 4c/8t @ 2.93GHz: ~20fps
- 4c/8t @ 3.20GHz: ~22fps
- 3c/3t @ 3.20GHz: ~22fps
- 2c/4t @ 3.46GHz: ~20fps
- 2c/2t @ 3.46GHz: ~20fps
Anything above 3c/3t still sees no benefit, and SMT still sees no utilization (though Nehalem's implementation of SMT is certainly going to be weaker than more modern implementations e.g. Ryzen).