[FFmpeg-trac] #9002(undetermined:new): subtitles filter fails to display all ASS subtitles

[FFmpeg]

#9002: subtitles filter fails to display all ASS subtitles
-------------------------------------+-------------------------------------
             Reporter:  aphysically  |                     Type:  defect
               Status:  new          |                 Priority:  normal
            Component:               |                  Version:  git-
  undetermined                       |  master
             Keywords:               |               Blocked By:
             Blocking:               |  Reproduced by developer:  0
Analyzed by developer:  0            |
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 Summary of the bug: For some files it seems ffmpeg's subtitles filter
 fails to display all the ASS subtitles that mpv displays. libass version
 is 0.15.0
 How to reproduce: Download testfile (2.1 MB)
 [https://gably.net/testcase/demo.mkv]
 Hardsub the subtitles in the file with the subtitles filter as follows:
 {{{
 #!/bin/bash
 rm -f log.txt
 ffmpeg -loglevel debug -i demo.mkv -vf subtitles=demo.mkv -c:v libx264
 -b:v 600k -c:a libopus -b:a 96k -map 0:v -map 0:a -y hardsubdemo.mkv
 >>log.txt 2>&1
 }}}
 Observe the subtitles where the leaf is talking aren't hardsubbed into
 `hardsubdemo.mkv`, but the line at the end is hardsubbed fine. Both
 subtitle lines can be observed by viewing the original file with mpv.

 I will attach log at `-loglevel debug` that shows build information and
 output.

--
Ticket URL: <https://trac.ffmpeg.org/ticket/9002>
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