[FFmpeg-trac] #2696(undetermined:new): Audio/Video sync issues when reducing fps from 59.94 to 29.97

FFmpeg trac at avcodec.org
Fri Jun 28 12:58:04 CEST 2013


#2696: Audio/Video sync issues when reducing fps from 59.94 to 29.97
-------------------------------------+-------------------------------------
             Reporter:  smblr75      |                    Owner:
                 Type:  defect       |                   Status:  new
             Priority:  normal       |                Component:
              Version:  unspecified  |  undetermined
             Keywords:               |               Resolution:
             Blocking:               |               Blocked By:
Analyzed by developer:  0            |  Reproduced by developer:  0
-------------------------------------+-------------------------------------

Comment (by smblr75):

 Ok, I think I have zeroed down on the problem, its only while playing this
 mp4 file using a flash player (which is the way we surface videos for our
 users), we see lots of sync issues but these go away (almost) when we use
 a quicktime player or play the video in chrome. This makes me believe that
 may be flash player is ignoring some of the header info which is different
 from the file transcoded by ffmpeg and that transcoded by rhozet.

 I could notice two differences, one using ffprobe and other using
 mediainfo.


 1) Difference in start times:
 ffmpeg transcoded file :
 {{{
   Duration: 00:02:41.37, start: 0.021333, bitrate: 663 kb/s
 }}}

 rhozet transcoded file:
 {{{
   Duration: 00:02:41.40, start: 0.000000, bitrate: 1169 kb/s
 }}}

 2) Difference in Audio delay reported by mediainfo in Audio section
 For ffmpeg transcoded file:
 {{{
 Delay relative to video                  : 67ms

 }}}

 In rhozet transcoded file there is no such line about "Delay relative to
 video"


 Can any of the above make a difference when being played by a flash
 player?

 Thanks,

-- 
Ticket URL: <https://ffmpeg.org/trac/ffmpeg/ticket/2696#comment:12>
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