[FFmpeg-trac] #8856(undetermined:new): Wrong colors (pink overlay) in webm video created from png image

[FFmpeg]

#8856: Wrong colors (pink overlay) in webm video created from png image
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             Reporter:  bers         |                     Type:  defect
               Status:  new          |                 Priority:  normal
            Component:               |                  Version:
  undetermined                       |  unspecified
             Keywords:               |               Blocked By:
             Blocking:               |  Reproduced by developer:  0
Analyzed by developer:  0            |
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 Summary of the bug:
 The file output_bad.webm has wrong colors (pink overlay):
 - when shown as a preview icon in Windows 10
 - when played in Google Chrome 84
 - when included in a MS PowerPoint (2016) presentation

 How to reproduce:
 {{{
 # Get image file
 curl
 https://upload.wikimedia.org/wikipedia/commons/thumb/6/66/SMPTE_Color_Bars.svg
 /500px-SMPTE_Color_Bars.svg.png > input.png

 # Convert according to instructions:
 https://trac.ffmpeg.org/wiki/Encode/VP9#constantq:~:text=Constant%20Quality,-In
 ffmpeg -i input.png -c:v libvpx-vp9 -crf 30 -b:v 0 output_bad.webm

 ffmpeg -i input.png -c:v libvpx-vp9 output_also_bad.webm

 # Compare to other format
 ffmpeg -i input.png output_good.mp4

 # I also tried a palette like here https://stackoverflow.com/q/58832085/
 ffmpeg -i input.png -vf palettegen palette.png
 ffmpeg -i input.png -i palette.png -lavfi paletteuse -c:v libvpx-vp9 -crf
 30 -b:v 0 output_still_bad.webm
 }}}

 Reproduced using ffmpeg 3 on OpenSUSE LEAP 15.1, and using ffmpeg 4.3 on
 Windows 10.

 With some different input data (different set of png files), the problem
 only occurs only with "-crf 30 -b:v 0", but not without. With yet
 different input data, it does not happen at all.

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Ticket URL: <https://trac.ffmpeg.org/ticket/8856>
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