[FFmpeg-trac] #7923(avcodec:reopened): alpha info is lost during transcode to gif from apng or animated webp

[FFmpeg]

#7923: alpha info is lost during transcode to gif from apng or animated webp
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             Reporter:  gbp.gap      |                    Owner:
                 Type:  defect       |                   Status:  reopened
             Priority:  normal       |                Component:  avcodec
              Version:  git-master   |               Resolution:
             Keywords:  apng, gif,   |               Blocked By:
  alpha, webp                        |
             Blocking:               |  Reproduced by developer:  0
Analyzed by developer:  0            |
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Changes (by gbp.gap):

 * status:  closed => reopened
 * resolution:  wontfix =>


Comment:

 With the command with palettegen,paletteuse as below, the unexpected red
 boundary lines are produced, which is different with the input apng file
 alpha.apng

 ./ffmpeg  -i alpha.apng -filter_complex
 "[0]split[a][b];[a]palettegen[p];[b][p]paletteuse " alpha_pale.gif

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Ticket URL: <https://trac.ffmpeg.org/ticket/7923#comment:3>
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