[FFmpeg-trac] #259(undetermined:open): framerate detection does not work properly. (mkv with default duration != actual average duration)

[FFmpeg]

#259: framerate detection does not work properly. (mkv with default duration !=
actual average duration)
-------------------------------------+-------------------------------------
             Reporter:  mbosner      |                    Owner:
                 Type:  defect       |                   Status:  open
             Priority:  normal       |                Component:
              Version:  unspecified  |  undetermined
             Keywords:  vc1          |               Resolution:
  pulldown mkv fps                   |               Blocked By:
             Blocking:               |  Reproduced by developer:  0
Analyzed by developer:  1            |
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Comment (by gjdfgh):

 This happens all the time. The most fun issue I've hit was when the
 framerate stored in the file was based on a frame duration... rounded to
 milliseconds. mkvinfo said "Default duration: 42.000ms (23.810
 frames/fields per second for a video track)". Even thouhg the file was
 actually 23.976, and there were frames with 41 ms duration. (Keep in mind
 that Matroska rounds timestamps to milliseconds.)

 But IMO libavformat shouldn't try to guess this. This belongs into a layer
 somewhere above the decoder. And it would need to be adaptive: what do you
 do about VFR files?

 Also, since such broken files can be remuxed to other formats, other
 formats can exhibit the same issue. I've seen it e.g. in a HLS stream too.

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Ticket URL: <https://trac.ffmpeg.org/ticket/259#comment:10>
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