[FFmpeg-trac] #5152(undetermined:reopened): Broken B frames while copying MPEG-2 ibp without recompression from some point

FFmpeg trac at avcodec.org
Tue Jan 12 14:14:39 CET 2016


#5152: Broken B frames while copying MPEG-2 ibp without recompression from some
point
-------------------------------------+-------------------------------------
             Reporter:               |                    Owner:
  Aleksandr_Slobodeniuk              |                   Status:  reopened
                 Type:  defect       |                Component:
             Priority:  normal       |  undetermined
              Version:  git-master   |               Resolution:
             Keywords:               |               Blocked By:
             Blocking:               |  Reproduced by developer:  0
Analyzed by developer:  0            |
-------------------------------------+-------------------------------------

Comment (by cehoyos):

 Replying to [comment:12 Aleksandr_Slobodeniuk]:
 > 1) result must be from 3:00 to 3:24

 This is impossible for {{{-vcodec copy}}} and the file you provided, and
 this is not a deficiency of FFmpeg.

 > 2) if you type (it's 25 frames)
 >
 > {{{
 > ffmpeg -i result.mov %d.jpg
 > }}}
 > you'll see that
 > - first 11 frames show 3:11 (because ffmpeg can't decode 11 b frames
 because they are from the middle of the gop)

 You have to use {{{-vsync 0}}} to avoid the command duplicating frames,
 the eleven frames are not part of result.mov, the first available frame is
 "3:11" and this is not related to FFmpeg but the format of the given input
 file.

 > - last 2 frames show 3:24 and 4:01 , 4:00 is missing (because it was not
 read. 4:01 is I frame that goes before 4:00 in the file, and it was pulled
 out with nullptr to avcodec_decode_video)

 How should FFmpeg behave in your opinion?

--
Ticket URL: <https://trac.ffmpeg.org/ticket/5152#comment:13>
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