[FFmpeg-trac] #1582(swscale:open): Banding/discoloration in darker gradients when converting to rgb24

[FFmpeg]

#1582: Banding/discoloration in darker gradients when converting to rgb24
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             Reporter:  y3kcjd5      |                    Owner:
                 Type:  defect       |                   Status:  open
             Priority:  normal       |                Component:  swscale
              Version:  git-master   |               Resolution:
             Keywords:  swscale,     |               Blocked By:
  bounty                             |
             Blocking:               |  Reproduced by developer:  1
Analyzed by developer:  0            |
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Comment (by gdgsdg123):

 Extended tests have been done regarding this issue.
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 Command:
 {{{
 C:\>FOR /R "INPUT" %X IN (*) DO ffmpeg -report -i "%X" -compression_level
 10 -pred mixed -pix_fmt rgb24 -sws_flags
 +print_info+accurate_rnd+full_chroma_int "%~nX.png"
 C:\>FOR /R "INPUT" %X IN (*) DO ffmpeg -report -i "%X" -compression_level
 10 -pred mixed -pix_fmt rgb24 -sws_flags +print_info+accurate_rnd
 ".\-full_chroma_int_%~nX.png"
 C:\>FOR /R "INPUT" %X IN (*) DO ffmpeg -report -i "%X" -compression_level
 10 -pred mixed -pix_fmt rgb24 -sws_flags +print_info+full_chroma_int
 ".\-accurate_rnd_%~nX.png"

 }}}
 (INPUT: yuv420p, yuv420p10le, yuv422p, yuv422p10le, yuv444p, yuv444p10le)
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 Files attached.

 Influenced files are marked with ! in filename.
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 Highlight:

 line 91 in "!-full_chroma_int_yuv420p.log":
 {{{
 [swscaler] chr srcW=720 srcH=418 dstW=720 dstH=836 xInc=65536 yInc=32768
 }}}
 line 91 in "yuv420p.log":
 {{{
 [swscaler] chr srcW=720 srcH=418 dstW=1440 dstH=836 xInc=32768 yInc=32768
 }}}
 line 92 in "!-accurate_rnd_yuv420p.log":
 {{{
 [swscaler] using unscaled yuv420p -> rgb24 special converter
 }}}

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Ticket URL: <https://trac.ffmpeg.org/ticket/1582#comment:16>
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