Thanks for reporting your issue. Please make sure these boxes are checked before submitting your issue - thank you!

- [ yes] I looked for a similar issue and couldn't find any.
- [yes ] I tried with the latest version of GPAC. Installers available at http://gpac.io/downloads/gpac-nightly-builds/
- [yes ] I give enough information for contributors to reproduce my issue (meaningful title, github labels, platform and compiler, command-line ...). I can share files anonymously with this dropbox: https://www.mediafire.com/filedrop/filedrop_hosted.php?drop=eec9e058a9486fe4e99c33021481d9e1826ca9dbc242a6cfaab0fe95da5e5d95

Detailed guidelines: http://gpac.io/2013/07/16/how-to-file-a-bug-properly/




we found an a/v sync issue in mp4box converted fragment mp4 
check below command
mp4box is from gpac https://github.com/gpac/gpac/wiki/MP4Box
mp4fragment is from bento4  https://www.bento4.com/

input: normal.mp4    
mp4fragment normal.mp4 mp4frag.mp4
output: mp4frag.mp4
mp4box -dash 20000 -profile onDemand -out output.mpd normal.mp4
output: output.mpd  normal_dashinit.mp4

 files are here .   https://mega.nz/file/PagnkAzJ#-OYNK78tw9XJsyAzh42Tv4FSPisN2pl6-X7tLKfxisw

normal.mp4 and mp4frag.mp4 can be played well in mac quicktime player Version 10.5 (1086.4.2)
output.mpd and normal_dashinit.mp4 can be played well in all browser player
However mp4box output normal_dashinit.mp4 could a trigger a a/v sync issue while seeking in quicktime player
try to seek to the middle position of the mp4,  you will found the count down a/v is not sync.
and normal_dashinit.mp4 has no audio for some time in latest version VLC player(Version 3.0.16 Vetinari (Intel 64bit) )

mp4frag.mp4  and normal_dashinit.mp4 are all fragment mp4 ,  although the format is a little different.
I guess there must be some timestamps wrong in the mp4 header , it caused this av sync issue

may be related to this issue,  I am not sure.
https://stackoverflow.com/questions/63262104/fragmented-mp4-not-playing-in-ffplay-quicktime-safari-but-in-vlc







a/v sync issue in mp4box converted fragment mp4 
This is a GitHub Issue
repo:gpac
owner:gpac
Title : a/v sync issue in mp4box converted fragment mp4 
Issue date:

--- start body ---
Thanks for reporting your issue. Please make sure these boxes are checked before submitting your issue - thank you!

- [ yes] I looked for a similar issue and couldn't find any.
- [yes ] I tried with the latest version of GPAC. Installers available at http://gpac.io/downloads/gpac-nightly-builds/
- [yes ] I give enough information for contributors to reproduce my issue (meaningful title, github labels, platform and compiler, command-line ...). I can share files anonymously with this dropbox: https://www.mediafire.com/filedrop/filedrop_hosted.php?drop=eec9e058a9486fe4e99c33021481d9e1826ca9dbc242a6cfaab0fe95da5e5d95

Detailed guidelines: http://gpac.io/2013/07/16/how-to-file-a-bug-properly/




we found an a/v sync issue in mp4box converted fragment mp4 
check below command
mp4box is from gpac https://github.com/gpac/gpac/wiki/MP4Box
mp4fragment is from bento4  https://www.bento4.com/

input: normal.mp4    
mp4fragment normal.mp4 mp4frag.mp4
output: mp4frag.mp4
mp4box -dash 20000 -profile onDemand -out output.mpd normal.mp4
output: output.mpd  normal_dashinit.mp4

 files are here .   https://mega.nz/file/PagnkAzJ#-OYNK78tw9XJsyAzh42Tv4FSPisN2pl6-X7tLKfxisw

normal.mp4 and mp4frag.mp4 can be played well in mac quicktime player Version 10.5 (1086.4.2)
output.mpd and normal_dashinit.mp4 can be played well in all browser player
However mp4box output normal_dashinit.mp4 could a trigger a a/v sync issue while seeking in quicktime player
try to seek to the middle position of the mp4,  you will found the count down a/v is not sync.
and normal_dashinit.mp4 has no audio for some time in latest version VLC player(Version 3.0.16 Vetinari (Intel 64bit) )

mp4frag.mp4  and normal_dashinit.mp4 are all fragment mp4 ,  although the format is a little different.
I guess there must be some timestamps wrong in the mp4 header , it caused this av sync issue

may be related to this issue,  I am not sure.
https://stackoverflow.com/questions/63262104/fragmented-mp4-not-playing-in-ffplay-quicktime-safari-but-in-vlc







--- end body ---
