Quote:
Originally Posted by CSMR
In this study HEVC codecs do well compared with AV1. But among HEVC codecs, the HHI solution is way ahead: "HHI HEVC encoder provides coding gain of 12.7%, while the encoding is more than 10 times faster compared to x265". Another study included the Intel Media SDK and that was way ahead.
Overall HEVC does well against other formats for free use (e.g. with the x265 codec), but blows everything away for commercial use (with HHI or Intel Media SDK).
Of course it will be great if x265 can significantly narrow the gap with the commercial encoders, or alternatively if the commercial encoders release free versions for non-commercial use.
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I am pretty cautious when trying to extrapolate from this kind of study. The test was only done in a particular config that isn't close to a real-world tuning. Fixed QP, no rate control! It seems like every block of every frame is identical, so no psychovisual tuning, no adaptive quant, no cu-tree, 1 sec fixed GOP, etcetera. So not particularly close to a real-world scenario. And there wasn't any subjective testing done.
Plus if you wanted to do a real placebo full test of x265, you'd include
--tskip --cu-lossless --bframes 16 --subme 7. And (if --tune psnr doesn't turn them off)
--psy-rd 0 --psy-rdoq 0 --aq-mode 0.
And comparing encoder speed in this whacked-out scenario is pretty meaningless. Placebo is slow by design, and not intended for any reasonable price/performance tradeoff. And turning off all threading makes it even less real-world relevant.
Moreover, PSNR in itself is the objective metric with the least correlation with subjective quality.
This is really more of an Excel comparison of a highly artificial scenario than actionable info. I'm not going to care much about a suggested video quality difference without seeing some video in a relevant scenario.
But such is the way of academic codec research. They do it this way because they've always done it this way.