Augment AQ mode 2 with variance info for more consistent quality under high/low contrast scenes
Currently, AQ mode 2 does a great job selecting the best QP for a given scene, if such scenes are high/medium contrast (e.g. sunny, bright overcast, or even well-lit night shots). However, under low contrast scenes (e.g. dark night, heavy fog/smoke, or overexposed bright shots), quality starts suffering significantly, and requires manually lowering CRF to compensate (usually by 3-5 for a starting CRF 35 encode, but rarely up to 10). Scenes become more blurry, moving artifacts become more pronounced, or even exhibit whole-SB macroblocking in the most extreme cases. Bitrate is unnecessarily low during these low-contrast shots, so it indicates SVT-AV1 is selecting too high of a qindex under these situations.
Factoring in variance into selecting a better-suited (i.e. lower) qindex might help with maintaining consistent quality across a wider range of scenes, either by integrating some aspects of (variance-based) AQ mode 1 into delta-q decisions, or somehow improving TPL to naturally become more aware of impact of variance in subjective video quality.
Implementing this will help with content that has both high and low-contrast scenes, like Parasite and The Fifth Element. My hunch is that calculating whole-SB variance should be enough to know where to boost qindex, so processing overhead should be minimal at worst.
I can give clips of both high and low-contrast scenes upon request.