[FFmpeg-trac] #10525(undetermined:new): Video⁄audio desync between segments in MPV and in VLC is delay between segments and missing subtitles

[FFmpeg]

#10525: Video⁄audio desync between segments in MPV and in VLC is delay between
segments and missing subtitles
-------------------------------------+-------------------------------------
             Reporter:  456325       |                     Type:  defect
               Status:  new          |                 Priority:  normal
            Component:               |                  Version:  git-
  undetermined                       |  master
             Keywords:  subtitles    |               Blocked By:
             Blocking:               |  Reproduced by developer:  0
Analyzed by developer:  0            |
-------------------------------------+-------------------------------------
 Summary of the bug:
 When i cut into 2 segments an .mp4 file that contains also subtitles and
 then merge the segments, it cause issue:
 MPV player: desynchronization between segments
 VLC player: delay between segments and missing subtitles

 When i exclude subtitles, it plays without problem.

 How to reproduce:

 # put source.mp4 ( [https://drive.proton.me/urls/TDNV2GN8QG#xUQpyO0Gna09
 download-here] ) into some directory (in my case /dev/shm/) and go to that
 directory inside a Linux terminal:

 cd /dev/shm/

 ffmpeg -hide_banner -ss '22.10829' -i 'source.mp4' -t '3.25325'
 -avoid_negative_ts make_zero -map '0:0' '-c:0' copy -map '0:1' '-c:1' copy
 -map '0:2' '-c:2' copy -map_metadata 0 -default_mode infer_no_subs
 -ignore_unknown -f mp4 -y 'source-seg2.mp4.mp4'

 ffmpeg -hide_banner -ss '11.13900' -i 'source.mp4' -t '1.00100'
 -avoid_negative_ts make_zero -map '0:0' '-c:0' copy -map '0:1' '-c:1' copy
 -map '0:2' '-c:2' copy -map_metadata 0 -default_mode infer_no_subs
 -ignore_unknown -f mp4 -y 'source-seg1.mp4.mp4'

 echo -e "file 'file:source-seg1.mp4.mp4'\nfile 'file:source-seg2.mp4.mp4'"
 | ffmpeg -hide_banner -f concat -safe 0 -protocol_whitelist 'file,pipe,fd'
 -i - -map '0:0' '-c:0' copy '-disposition:0' default -map '0:1' '-c:1'
 copy '-disposition:1' default -map '0:2' '-c:2' copy '-disposition:2'
 default -default_mode infer_no_subs -ignore_unknown -f mp4 -y
 'destination-merged.mp4'

 # Play to see described issue:
 vlc destination-merged.mp4
 mpv destination-merged.mp4

 # When excluding subtitles, it plays without apparent problem:

 ffmpeg -hide_banner -ss '22.10829' -i 'source.mp4' -t '3.25325'
 -avoid_negative_ts make_zero -map '0:0' '-c:0' copy -map '0:1' '-c:1' copy
 -map_metadata 0 -default_mode infer_no_subs -ignore_unknown -f mp4 -y
 'source-seg2-nosubs.mp4.mp4'

 ffmpeg -hide_banner -ss '11.13900' -i 'source.mp4' -t '1.00100'
 -avoid_negative_ts make_zero -map '0:0' '-c:0' copy -map '0:1' '-c:1' copy
 -map_metadata 0 -default_mode infer_no_subs -ignore_unknown -f mp4 -y
 'source-seg1-nosubs.mp4.mp4'

 echo -e "file 'file:source-seg1-nosubs.mp4.mp4'\nfile 'file:source-
 seg2-nosubs.mp4.mp4'" | ffmpeg -hide_banner -f concat -safe 0
 -protocol_whitelist 'file,pipe,fd' -i - -map '0:0' '-c:0' copy
 '-disposition:0' default -map '0:1' '-c:1' copy '-disposition:1' default
 -default_mode infer_no_subs -ignore_unknown -f mp4 -y 'destination-merged-
 nosubs.mp4'

 # Play to see no issue:
 vlc destination-merged-nosubs.mp4
 mpv destination-merged-nosubs.mp4
-- 
Ticket URL: <https://trac.ffmpeg.org/ticket/10525>
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