[FFmpeg-trac] #10264(swscale:open): DXV encoded video playback contains horizontal lines

FFmpeg trac at avcodec.org
Sat Mar 18 13:24:16 EET 2023

#10264: DXV encoded video playback contains horizontal lines
             Reporter:  low-batt    |                    Owner:  (none)
                 Type:  defect      |                   Status:  open
             Priority:  normal      |                Component:  swscale
              Version:  git-master  |               Resolution:
             Keywords:              |               Blocked By:
             Blocking:              |  Reproduced by developer:  0
Analyzed by developer:  0           |
Changes (by Balling):

 * status:  new => open
 * component:  ffplay => swscale


 The bug is not in ffplay. Same happens with ffmpeg.exe -i
 Samoan_20_Ring_Into.mov  -compression_level 9 -pred mixed bugggy.png

 but not with

 ffmpeg.exe -i Samoan_20_Ring_Into.mov -frames:v 1 -crf 0 -cpu-used 0

 so the problem is with transperency, since we do not support AVIF with
 transperency yet and indeed you can see alpha plane is buggy with

 ffplay.exe -i bugggy.png -vf extractplanes=a

 Moreover same happens in windows 11. Maybe gcc 12.2 and Apple clang bug?
 Though unlikely two compilers having same bug.

 Looks like the bug is in swscale with alpha. Please attach output of
 ffmpeg -i Samoan_20_Ring_Into.mov -compression_level 9 -pred mixed
 here too. Thanks.

 Unfortunately it is possible this is just a buggy file.

 Remember VLC does not really support trasperancy like that, you need to
 use mpv and that is even worse artefacts.
Ticket URL: <https://trac.ffmpeg.org/ticket/10264#comment:4>
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