[FFmpeg-trac] #6421(undetermined:open): PTS incorrectly fixed up to be negative

[FFmpeg]

#6421: PTS incorrectly fixed up to be negative
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             Reporter:  sandersd     |                    Owner:  isasi
                 Type:  defect       |                   Status:  open
             Priority:  important    |                Component:
              Version:  git-master   |  undetermined
             Keywords:  mov h264     |               Resolution:
  edts regression                    |               Blocked By:
             Blocking:               |  Reproduced by developer:  0
Analyzed by developer:  0            |
-------------------------------------+-------------------------------------
Changes (by isasi):

 * owner:   => isasi
 * status:  new => open


Comment:

 This is a bug in the edit list fix index code. This line
 http://git.videolan.org/?p=ffmpeg.git;a=blob;f=libavformat/mov.c;h=3845e63b5359a135ea322acd28729dbdb2722019;hb=HEAD#l3087
 , causes the PTS to be negative. The intention of the line is to make the
 first pts to be zero. But the problem here is that the first packet in the
 decoding order is not the first packet in the presentation order, and in
 that line we are subtracting by the timestamp of the first packet in
 decoding order. What we need to do is find the first packet in the
 presentation order and its resulting PTS after edit list is applied, and
 then offset all the timestamps to make that PTS zero. I am working on that
 fix.

 You can do -advanced_editlist=0 to disable the fix index feature, but keep
 in mind that without that feature you will have AVSync issues anyway,
 because the timestamps are not adjusted properly according to the edit
 list.

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Ticket URL: <https://trac.ffmpeg.org/ticket/6421#comment:5>
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