[x265] Issue #26: v0.7: Severe quantizer difference between {...faster} and {fast...} presets (multicoreware/x265)

[Mario Rohkrämer]

New issue 26: v0.7: Severe quantizer difference between {...faster} and {fast...} presets
https://bitbucket.org/multicoreware/x265/issue/26/v07-severe-quantizer-difference-between

Mario Rohkrämer:

With default options (CRF 28), all presets {'faster' *and faster*} produce a much larger result and also much better visual quality than all presets {'fast' *and slower*}.

This means about 5:1 the size and -5 dB SSIM with CUTree enabled, and about 4:1 the size and -4 dB SSIM with CUTree disabled (for the faster group, it is disabled anyway; but it appears to be not the main reason).

Values for a specific CRF value are similar, confirming the groups of presets in general.

Because there is no current Evaluators' Guide for v0.7, I can't be certain which defaults changed between these presets.

BTW: This bug tracker needs more entries in the "Version" selector.