[FFmpeg-devel] avcodec/prores_ks : do not call estimate_alpha at each quantification step

Martin Vignali martin.vignali at gmail.com
Sat Mar 31 20:06:35 EEST 2018

> probably ok, check that this does not break alpha encoding.
Alpha encoding still work.

In fact this patch improve quality, when alpha encoding is used. (Not
intented at the start).
The modification came from the suppression of error arg and the move of
Before this patch, estimate alpha, reset error to zero after slice
After this patch, the error value of YUV slice estim is used.

Can be see using file

./ffmpeg -i source.png -c:v prores_ks res.mov

After this patch, there is less blocking effect on edge

I will wait few days, if someone have other comments, before pushing.


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