[FFmpeg-trac] #1678(undetermined:new): Regression with -vsync 1

[FFmpeg]

#1678: Regression with -vsync 1
-------------------------------------+-------------------------------------
             Reporter:  jwjwjw       |                    Owner:
                 Type:  defect       |                   Status:  new
             Priority:  important    |                Component:
              Version:  git-master   |  undetermined
             Keywords:  regression   |               Resolution:
             Blocking:               |               Blocked By:
Analyzed by developer:  0            |  Reproduced by developer:  0
-------------------------------------+-------------------------------------

Comment (by jwjwjw):

 Yes, I carried out further testing of the http://jwjwjw.com/ffmpeg
 /bbcnews-original.mp4 source file using a basic command line to rule out
 any other options or external libraries:

 {{{
 ffmpeg -i bbcnews-original.mp4 -c:v mpeg4 -c:a aac -strict experimental
 output.mp4
 }}}

 It yields the following results in different versions of ffmpeg:

 c5ea3a0 onwards up to and including git-master (file is out of sync):
 {{{
   Duration: 00:01:37.84, start: 0.000000
 }}}

 8f5bb35 (file is out of sync):
 {{{
   Duration: 00:01:37.80, start: 0.000000
 }}}

 pre-8f5bb35 (file is in sync perfectly):
 {{{
   Duration: 00:01:37.76, start: 0.000000
 }}}

 The following command shows that there are additional frames at the start
 of the out of sync output that are not present in the in sync output,
 whilst the audio is the same in all 3 clips (so the sync is out by the
 number of additional frames):

 {{{
 ffmpeg -i output.mp4 output%d.jpg
 }}}

 So it seems to be a regression since 8f5bb35 but something also changed in
 c5ea3a0 too.

-- 
Ticket URL: <https://ffmpeg.org/trac/ffmpeg/ticket/1678#comment:8>
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