[FFmpeg-trac] #7855(avformat:reopened): Last subtitle in MP4 is displayed forever

[FFmpeg]

#7855: Last subtitle in MP4 is displayed forever
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             Reporter:  fumoboy007   |                    Owner:
                 Type:  defect       |                   Status:  reopened
             Priority:  normal       |                Component:  avformat
              Version:  git-master   |               Resolution:
             Keywords:  mp4,         |               Blocked By:
  mov_text                           |
             Blocking:               |  Reproduced by developer:  1
Analyzed by developer:  0            |
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Comment (by fumoboy007):

 Replying to [comment:5 mkver]:

 >  b) The sample from this issue is different: It has two samples (for one
 line of subtitles) and two entries in the stts containing two dts deltas:
 5s and 3s, so that the dts of the first sample (the "empty" sample) is 0s
 and the time of the second sample (containing the actual subtitle) is 5s.
 And if there were another sample, then this sample would have a dts of 8s.
 But there isn't. Furthermore, the track as a whole has a duration of 8s. I
 am not sure whether this file is completely spec-compliant; I am leaning
 to yes.

 I would like to help debug this, but I have no knowledge of the format. Is
 there somewhere I can freely download the MPEG-4 Timed Text specification
 (is that the right one?) or is there some document that summarizes the
 specification?

 > 5. Modified versions of FFmpeg are even more unsupported than release
 versions. So you actually should not rebase your own commits on current
 git head, but just test current git head.\\
 >  The rationale for this policy is that it would waste developer's time
 to test something that might already have been fixed.

 Oh, I see git head is more than a thousand commits ahead of the releases.
 OK, I will spend the extra time to test on git head for future bug reports
 in case the issue is already fixed.

 > 6. The comment cehoyos wants you to suppress is surely "I’m surprised
 this bug made it through!". The claim you base this on is btw wrong as the
 sample from #6341 shows.

 Sorry for the false claim. My “surprised” comment was not meant to be
 accusatory; sorry if it came off that way. That being said, it would have
 been more productive to post a concrete rejection of the claim rather than
 a passive-aggressive response.

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Ticket URL: <https://trac.ffmpeg.org/ticket/7855#comment:7>
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