[FFmpeg-trac] #9520(ffmpeg:new): Invalid pal8 -> gbrp conversion

[FFmpeg]

#9520: Invalid pal8 -> gbrp conversion
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             Reporter:  Robin        |                    Owner:  (none)
                 Type:  defect       |                   Status:  new
             Priority:  normal       |                Component:  ffmpeg
              Version:  4.4.1        |               Resolution:
             Keywords:  pal8, gbrp,  |               Blocked By:
  pix_fmt                            |
             Blocking:               |  Reproduced by developer:  0
Analyzed by developer:  0            |
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Comment (by Robin):

 Looks like it maybe related to #1286 which doesn't give me much hope this
 will ever be fixed since has been opened for a decade.

 However that ticket is reporting color conversion errors TO pal8. This
 ticket is showing conversions errors are occurring FROM pal8 TO specific
 formats.

 produces errors: pal8 -> gbrp
 correct: pal8 -> bgr0
 correct: pal8 -> bgr0 -> gbrp
 correct: pal8 -> pal8

 #1286:
 produces errors: rgb24 -> pal8
 correct: pal8 -> pal8

 On a sidenote, it appears Irfanview also gives incorrect results
 converting to pal8. However, both ffmpeg and irfanview give different
 results when converting to pal8.

 I confirmed by taking a bgr24 BMP and performing a down conversion to pal8
 and then back to bgr24. The resulting pal8 BMPs were different from each
 other and the following bgr24 were also different, both from each other
 and from the reference bgr24 BMP.

 Both Irfanview and ffmpeg give the same results up converting pal8 BMPs to
 bgr24 BMPs.
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Ticket URL: <https://trac.ffmpeg.org/ticket/9520#comment:2>
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