[FFmpeg-trac] #10927(avcodec:new): Converting EIA-608 to ASS can have multiple \pos tags

[FFmpeg]

#10927: Converting EIA-608 to ASS can have multiple \pos tags
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             Reporter:  SuperrSonic  |                     Type:  defect
               Status:  new          |                 Priority:  wish
            Component:  avcodec      |                  Version:
                                     |  unspecified
             Keywords:               |               Blocked By:
             Blocking:               |  Reproduced by developer:  0
Analyzed by developer:  0            |
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 Summary of the bug:

 As described here: https://github.com/libass/libass/issues/738
 libass rendering doesn't allow more than 1 \pos per line/event.

 At the end I include a command line tool that can split the \N on each
 line to a new dialogue event line, this allows the extra \pos tags to be
 used, producing an accurate look to the TV's CC decoder.

 I could try modifying ffmpeg but I wanted to find out if there's a better
 way to fix this, or a reason why this shouldn't be done.

 The code here seems to be what adds the \N it's always followed by a \pos,
 so replacing this code to make it into a new dialogue event should be
 enough to fix it. How to do that, I am still not sure.
 https://github.com/FFmpeg/FFmpeg/blob/master/libavcodec/ccaption_dec.c#L601


 How to reproduce:
 {{{
 % ffmpeg -f lavfi -i movie=video.m2v[out0+subcc] -map 0:s -c:s ass
 video_cc.ass

 ffmpeg version N-113881-gf7545e90df-20240301
 }}}

 I've been ripping a lot of my collection to contain these captions, but
 the tools I've used, like makemkv remove the original caption data, so I
 don't have any samples right now.
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Ticket URL: <https://trac.ffmpeg.org/ticket/10927>
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