[FFmpeg-trac] #9491(avfilter:new): ass/subtitle filter incorectly handles colorspaces

FFmpeg trac at avcodec.org
Sun Oct 31 22:42:54 EET 2021

#9491: ass/subtitle filter incorectly handles colorspaces
             Reporter:               |                     Type:  defect
  alwinramirus                       |
               Status:  new          |                 Priority:  normal
            Component:  avfilter     |                  Version:  git-
                                     |  master
             Keywords:  ass          |               Blocked By:
             Blocking:               |  Reproduced by developer:  0
Analyzed by developer:  0            |
 Summary of the bug:
 I am trying to burn in ass subtitles on to a video. The resulting video
 differs in color to what media players and subtitle editors display.
 The video is in BT.709 limited and the ass subtitles file contains the
 header line YCbCr Matrix: TV.709.
 What I assume happens:
 The ass videofilter incorrectly converts the RGB values to BT.601 instead
 of BT.709 resulting in shifted colors.
 How to reproduce:
 % ffmpeg -i video.mp4 -vf ass=subtitles.ass out.mp4
 ffmpeg version N-104454-gd92fdc7144-20211031 Copyright (c) 2000-2021 the
 FFmpeg developers
 I have attached the files used for testing.
Ticket URL: <https://trac.ffmpeg.org/ticket/9491>
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