[FFmpeg-trac] #1924(avformat:closed): ASS subtitles are demuxed inconsistently

[FFmpeg]

#1924: ASS subtitles are demuxed inconsistently
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             Reporter:  gjdfgh       |                    Owner:
                 Type:  enhancement  |                   Status:  closed
             Priority:  normal       |                Component:  avformat
              Version:  unspecified  |               Resolution:  invalid
             Keywords:  ass          |               Blocked By:
             Blocking:               |  Reproduced by developer:  0
Analyzed by developer:  0            |
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Comment (by plorkyeran):

 > I have no idea what the ReadOrder? field is about. Looking at libass, it
 looks like a fully demuxed ASS file might behave differently from muxed
 subs that are fed per-packet as they are demuxed from an interleaved
 stream.

 ASS subtitles don't have to be sorted by time, but an interleaved stream
 obviously needs to be. Since the order of the lines effects the rendering,
 the original index of the line is stored in the ReadOrder field so that
 the renderer can reconstruct the unsorted order.

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Ticket URL: <https://ffmpeg.org/trac/ffmpeg/ticket/1924#comment:6>
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