Quoting Michael Niedermayer (2023-10-31 09:40:44) > On Mon, Oct 30, 2023 at 02:11:27PM +0100, Andreas Rheinhardt wrote: > > Section 7.4.4 of the MPEG-2 specifications requires that the > > last bit of the last coefficient be toggled so that the sum > > of all coefficients is odd; both our decoder and encoder > > did this only if the bitexact flag has been set (although > > stuff like this should be behind AV_CODEC_FLAG2_FAST). > > This patch changes this by removing the spec-incompliant > > functions. > > This commit message should include benchamarks documenting the speed loss > (of the unquantize, the IDCT and overall) > It is expected that the speed of some IDCTs will be impacted negativly > as the non zero terms will prevent the skiping of some significant code > > as well as information about how much PSNR improves (to the encoder input) > > Also the change is a +-1 in one spot before the IDCT, the IDCT is not > bitexactly > specified in MPEG-2 so one could think of this as a > correct implementation followed by a IDCT that was sometimes +-1 off > instead of spec non compliance > > Only after the benchmarks and PSNR is presented should we decide if this > is a change we want
I disagree that the burden of proof should be on Andreas here. It should be up to whoever wants to keep this code to show that it is useful. -- Anton Khirnov _______________________________________________ ffmpeg-devel mailing list ffmpeg-devel@ffmpeg.org https://ffmpeg.org/mailman/listinfo/ffmpeg-devel To unsubscribe, visit link above, or email ffmpeg-devel-requ...@ffmpeg.org with subject "unsubscribe".
