Played around with a checkout from master branch on Sat, and the decoder fails with --tune=ssim
and --best during scene changes. I then just did a build with their current code, which merged in some goodies from their experimental branch. Now --tune=ssim breaks the encoder instead with "segmentation fault 11" during the first 16 frames of pass 2. Maybe it's auto-alt-ref related, but either way, looks like they definitely aren't developing for SSIM...
With the older build, I did quick 2pass runs of a dark, slightly grainy source and no tunings on either encoders. VP9 had a lot higher PSNR (maybe it defaults to this tuning) and slightly higher SSIM than x264 placebo (forgot to match keyint though whoops), but x264 fared better visually, especially in scenes of grain against a flat background. VP9 also had this weird thing where grain suddenly reappeared for 1 frame and then goes away again, and the contrast is extreme enough to be noticeable in normal playback.
I think there's definitely still some qp and rc tunings to be done. In terms of objective metrics, however, things are at least very promising.
Code:
vpxenc -p 2 -t 1 --codec=vp9 --best --cpu-used=0 \
--target-bitrate=1500 --end-usage=vbr \
--auto-alt-ref=1 -v \
--minsection-pct=5 --maxsection-pct=800 \
--lag-in-frames=16 --kf-min-dist=0 --kf-max-dist=360 \
--token-parts=2 --static-thresh=0 --drop-frame=0 \
--min-q=0 --max-q=60 \
-o .webm .y4m
No hard numbers because I only wanted tune-ssim results and deleted everything after visual inspection.
