- [x] I looked for a similar issue and couldn't find any.
- [x] I tried with the latest version of GPAC. Installers available at http://gpac.io/downloads/gpac-nightly-builds/
- [x] I give enough information for contributors to reproduce my issue (meaningful title, github labels, platform and compiler, command-line ...).

Essentially the issue only seems to happen with 7.1 audio muxed with mp4box. If you play the file and do not touch seek at all, the audio will stay in sync. If you pause/seek (forwards/backwards) the audio will either not play for a while or once it does it's very very out of sync.
This only seems to be present when the 7.1 audio is encoded with Dolby Encoding Engine. 
If i encode the audio with ffmpeg, the issue is not present in the mp4. 
If i mux the DEE audio with the video into mp4 with ffmpeg the issue is not present.
If i mux the DEE audio with the video into mkv with mkvtoolnix the issue is not present.

The issue only seems to happen with audio encoded with dolby encoding engine, and muxed with mp4box.

Here is a zip file with my sample examples, using a DTS:X Demo video.
I have provided a sample of the audio encoded to eac3 with both ffmpeg and dolby encoding engine. 
If you play the DTSX Gravity Encoded - ffmpeg.mp4 in VLC media player you should see that it plays back fine even when skipping around the video.
If you play the DTSX Gravity Encoded - DEE.mp4 in VLC media player, you should see that it initially plays back fine but as soon as you start skipping around the video the audio becomes out of sync.

https://mega.nz/file/icJTzYZA#6Uy9J7zLXyThM7qZed0zdeQR5lByKymORkHa--bR_eY
7.1 E-AC3 audio out of sync in MP4 only with mp4box
This is a GitHub Issue
repo:gpac
owner:gpac
Title : 7.1 E-AC3 audio out of sync in MP4 only with mp4box
Issue date:

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- [x] I looked for a similar issue and couldn't find any.
- [x] I tried with the latest version of GPAC. Installers available at http://gpac.io/downloads/gpac-nightly-builds/
- [x] I give enough information for contributors to reproduce my issue (meaningful title, github labels, platform and compiler, command-line ...).

Essentially the issue only seems to happen with 7.1 audio muxed with mp4box. If you play the file and do not touch seek at all, the audio will stay in sync. If you pause/seek (forwards/backwards) the audio will either not play for a while or once it does it's very very out of sync.
This only seems to be present when the 7.1 audio is encoded with Dolby Encoding Engine. 
If i encode the audio with ffmpeg, the issue is not present in the mp4. 
If i mux the DEE audio with the video into mp4 with ffmpeg the issue is not present.
If i mux the DEE audio with the video into mkv with mkvtoolnix the issue is not present.

The issue only seems to happen with audio encoded with dolby encoding engine, and muxed with mp4box.

Here is a zip file with my sample examples, using a DTS:X Demo video.
I have provided a sample of the audio encoded to eac3 with both ffmpeg and dolby encoding engine. 
If you play the DTSX Gravity Encoded - ffmpeg.mp4 in VLC media player you should see that it plays back fine even when skipping around the video.
If you play the DTSX Gravity Encoded - DEE.mp4 in VLC media player, you should see that it initially plays back fine but as soon as you start skipping around the video the audio becomes out of sync.

https://mega.nz/file/icJTzYZA#6Uy9J7zLXyThM7qZed0zdeQR5lByKymORkHa--bR_eY
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