[FFmpeg-trac] #3345(swscale:open): Bias in planar YUV to YUV bit depth conversion

FFmpeg trac at avcodec.org
Wed Sep 8 17:06:20 EEST 2021

#3345: Bias in planar YUV to YUV bit depth conversion
             Reporter:  abc123      |                    Owner:  (none)
                 Type:  defect      |                   Status:  open
             Priority:  normal      |                Component:  swscale
              Version:  git-master  |               Resolution:
             Keywords:  bounty      |               Blocked By:
             Blocking:              |  Reproduced by developer:  0
Analyzed by developer:  0           |
Comment (by pdr0):

 Replying to [comment:13 Balling]:
 > Are results worse with dither? I suppose the problem here is that
 strange double color dither even with dither none, you reproduced that on
 that AV1 file, rememember? Why I somehow did not.
 > >fluctuates a bit, almost as if output is dithered
 > https://trac.ffmpeg.org/ticket/9167#comment:10

 Yes, results are worse with dither. I'll revisit the other ticket later

 For this ticket , I attached a 1280x720 yuv444p10le .yuv frame, single
 color YUV 523,503,559 so it's easier to reproduce the issue and ease of

 ffmpeg -pix_fmt yuv444p10le -s 1280x720 -i
 1280x720_yuv444p10le_523_503_559.yuv -vf zscale=dither=none,format=yuv444p
 -f rawvideo test02_zscale_nodither.yuv
 YUV 130,125,139

 ffmpeg -pix_fmt yuv444p10le -s 1280x720 -i
 1280x720_yuv444p10le_523_503_559.yuv -vf
 scale=sws_dither=none,format=yuv444p -f rawvideo
 YUV 131,126,140

 I tried some sws flags such as accurate_rnd, but no change
Ticket URL: <https://trac.ffmpeg.org/ticket/3345#comment:14>
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