Quote:
Originally Posted by utack
Netflix dropped a new article.
H264/H265/VP9 comparison using HVMAF with reference encoders and production encoders.
libvpx is doing mediocre'ish, EVE does well
Relative Bitrate savings for low and high quality using three test sets:
https://medium.com/netflix-techblog/...e-d45d0183ca95 |
Now VMAF gives different scores for mobile, 1080p, and UHD screen sizes. They don’t seem to specify which they used here.
Or perhaps this was done with an older VMAF implementation?
I’m having a hard time figuring out what settings they are actually using. It sounds like it’s fixed QP, with one psychovisual parameter added for each “perceptual” tuned mode. So are x264 and x265 fixed QP encodes with psy-rd=1? Is aq-mode=0? And really QP instead of CRF? And when aiming for PSNR, why not --tune psnr which is EXACTLY for that scenario! Psy-rd=0 is NOT tuning for PNSR!
And odd libvpx gets to use 2 passes while everything else is 1. Although that wouldn’t really matter that much if it’s truly a fixed QP encode with no rate control. But if using --tune psnr for x26? multipass encoding should help mean and harmonic mean PSNR.
This seems a quite poor study for predicting the real-world subjective quality different encoders can produce, as it will substantially underestimate the achievable perceptual quality the x26x codecs can deliver in the real world. I’d expect just adding --tune film to x264 would improve VMAF a bunch in the perceptual case.
It sort of conflates encoder psychovisual tuning and bitstream capabilities. I imagine a port of x264’s psyovisual stuff to a vp9 encoder would offer big improvements, like was seen when x264 algorithms got ported into x265.