[FFmpeg-trac] #7927(undetermined:closed): Video copy from mkv to mp4 causes variable frame rate from constant frame rate

[FFmpeg]

#7927: Video copy from mkv to mp4 causes variable frame rate from constant frame
rate
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             Reporter:  Mads         |                    Owner:  (none)
  Johansen                           |
                 Type:  defect       |                   Status:  closed
             Priority:  normal       |                Component:
                                     |  undetermined
              Version:  git-master   |               Resolution:  invalid
             Keywords:               |               Blocked By:
             Blocking:               |  Reproduced by developer:  0
Analyzed by developer:  0            |
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Comment (by dojima):

 Is anyone able to take ''any'' MKV file and copy it to an MP4 container
 with ffmpeg and have it remain at a constant framerate?  I'm no expert, so
 I can't begin to guess why this doesn't work intuitively.  The only way I
 am able to do this is by using {{{-video_track_timescale}}}, but it
 doesn't work with 59.94 or presumably 29.97, 23.976, etc.  In order to
 convert a 59.94 constant MKV to MP4, I had to output it as a raw stream
 with mkvextract and then put that into an MP4 container with MP4Box.

 Replying to [comment:9 Balling]:
 > But this is the point. You original file is recognized as VFR! So if
 there is a bug it is in the initial parser of the original file. And that
 is due to it 30/1.001 fps. If you used 25.000 it will not be a problem.
 > {{{
 > ffmpeg -i Convert_to_mp4_ConstantFramerate_to_VariableFramerate.mkv -vf
 vfrdet -an -f null -
 > }}}
 Near as I can tell, any MKV run with that command will show VFR.  Is that
 intended behavior?
-- 
Ticket URL: <https://trac.ffmpeg.org/ticket/7927#comment:16>
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