[FFmpeg-trac] #377(undetermined:new): ffmpeg reports inaccurate length of some gxf files

FFmpeg trac at avcodec.org
Tue Aug 2 20:51:08 CEST 2011

#377: ffmpeg reports inaccurate length of some gxf files
Reporter:  acloutier              |       Owner:
    Type:  defect                 |      Status:  new
Priority:  important              |   Component:  undetermined
 Version:  git                    |  Resolution:
Keywords:  gxf ffmpeg length bug  |  Blocked By:
Blocking:                         |  Reproduced:  0
Analyzed:  0                      |

Comment (by reimar):

 By my understanding of the format, the best guess it does right now is the
 best that is possible reliably.
 The problem with this file is that it does not contain FPS in the track
 So FFmpeg is forced to fall back to the UMF tag (which is rather
 That one specifies 60 FPS, i.e. 120 fields per second (which is obviously
 not correct).
 The file also claims to contain 438170 fields.
 And that gives the calculated result.
 Obviously it would be possible to just guess that 120 fields per second is
 not correct, but that does not seem like a good solution to me.
 So unless you can give me some other info my conclusion would be that the
 file is broken and will only work correctly with programs/equipment that
 will break if you ever want to use it with 60 fps / 120 fields per second

Ticket URL: <https://avcodec.org/trac/ffmpeg/ticket/377#comment:4>
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