[FFmpeg-devel] [PATCH] swscale_unscaled: fix DITHER_COPY macro, use it only for dst_depth == 8

Mateusz mateuszb at poczta.onet.pl
Mon Sep 25 10:49:51 EEST 2017

W dniu 2017-09-25 o 01:42, Carl Eugen Hoyos pisze:
> 2017-09-23 19:18 GMT+02:00 Mateusz <mateuszb at poczta.onet.pl>:
>> In reality -- current version of DITHER_COPY mess
>> up the average color tone.
> You could explain how we can reproduce this.

Please take any video with colors that you can see change to green color --
it could be with human faces, for example free

Copy the video to o.y4m and make some iteration of 8-bit -> 10-bit -> 8-bit conversions:
ffmpeg -i o.y4m -y -strict -1 -pix_fmt yuv420p10 t10.y4m
ffmpeg -i t10.y4m -y -strict -1 -pix_fmt yuv420p o.y4m

Please watch result video -- it should be more green, with pattern and darker.

You can watch 'KristenAndSara' video after 100 iteration

And 100th iteration of 'KristenAndSara' with '-color_range 2' option

Now DITHER_COPY works wrong in both cases (full and limited range).


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