Quote:
Originally Posted by benwaggoner
AWCY doesn’t include any metrics that are well demonstrated to be able to finely discriminate between quality of different encoders and codecs. VMAF is the least-bad we’ve ever had, but can still be off quite a bit for individual clips, especially if the use codec features or psychovisual optimizations that weren’t included in their test clips.
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Isn't there also the possibility that there's a sort of implicit "training" for this metric included in one codec/encoder and not the other?
I don't know whether VMAF was used in some x265 tuning, but given the age of all the significant parts of x264 codebase, I am fairly sure that there has been no attempts to do this.
Meanwhile VMAF was IIRC used during development of Daala and AV1 and maybe AOMenc/Rav1e? In that case, there could be some inherent bias in the metric towards those codecs that would then add some imaginary advantage above their real compression quality into the numbers, when measured by VMAF. Simply because their output was implicitly tuned to get better VMAF, because VMAF was used to test new tools/analysis/RDO and so on.