[FFmpeg-trac] #786(avformat:new): GXF file frame rate double what it should be for some files.

FFmpeg trac at avcodec.org
Mon Dec 19 18:40:09 CET 2011

#786: GXF file frame rate double what it should be for some files.
             Reporter:  ryaowe      |                    Owner:
                 Type:  defect      |                   Status:  new
             Priority:  normal      |                Component:  avformat
              Version:  git-master  |               Resolution:
             Keywords:              |               Blocked By:
             Blocking:              |  Reproduced by developer:  0
Analyzed by developer:  0           |

Comment (by reimar):

 This is a bit difficult since I don't have the spec available, but
 basically it says that for the time stamps that even ones always indicate
 the first field and odd ones the second field (independent of number of
 fields per frame). So for progressive the time stamps should always the
 even and increment by 2.
 Thus the time stamp always increases by two per frame regardless of
 progressive or interlaced, and the time base is 1/(2*fps) in both cases.
 If your video is indeed 60 fps progressive that sounds like the timestamps
 are not encoded the way they are required by the specification (as I
 remember it) and that would make things a bit difficult.
 Now it's not impossible that my understanding is based on misunderstanding
 the specification, but I was convinced enough to change it (the code was
 originally the way you suggest to change it).
 Note the issue number is from the old roundup tracker, it seems a copy of
 it exists here: http://roundup.libav.org/issue1766

 commit 192c14fa5510e8b5e13ed5796ae87aabbfad84d6
 Author: Reimar Döffinger <Reimar.Doeffinger at gmx.de>
 Date:   Sat Mar 6 22:20:33 2010 +0000

     GXF time base is always based on "fields" per second even for
     non-interlaced video.
     Should fix issue 1766.

     Originally committed as revision 22256 to

Ticket URL: <https://ffmpeg.org/trac/ffmpeg/ticket/786#comment:6>
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