[FFmpeg-trac] #6905(undetermined:closed): When copying video from .avi to .mp4, frames have incorrect pts values

[FFmpeg]

#6905: When copying video from .avi to .mp4, frames have incorrect pts values
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             Reporter:  Misaki       |                    Owner:
                 Type:  defect       |                   Status:  closed
             Priority:  normal       |                Component:
              Version:  git-master   |  undetermined
             Keywords:               |               Resolution:
             Blocking:               |  needs_more_info
Analyzed by developer:  0            |               Blocked By:
                                     |  Reproduced by developer:  0
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Comment (by Misaki):

 I didn't know about that option, but it does not make a difference. The
 warning messages '[mp4 @ 0x5569f707bea0] Timestamps are unset in a packet
 for stream 0. This is deprecated and will stop working in the future. Fix
 your code to set the timestamps properly' and '[mp4 @ 0x5569f707bea0] pts
 has no value' x30 for the test file are still there, and timestamps in the
 output file are the same as without the option.

 Reproducing is easy, just copy the video stream in any avi with B-frames
 to mp4 format. Confirming that the output is such that it will stutter in
 Chrome, even though it has almost no problems in most players, is more
 difficult, and that's where it helps to start with an mp4 so you can see
 that the start and end files are clearly different.

 Symptom is that if examined with ffprobe, a stutter-prone file will have
 same dts as pts with -show_packets, while normal mp4s have same with
 -show_frames.

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Ticket URL: <https://trac.ffmpeg.org/ticket/6905#comment:8>
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