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

- [ ] I looked for a similar issue and couldn't find any.
- [ ] I tried with the latest version of GPAC. Installers available at https://gpac.io/downloads/gpac-nightly-builds/
- [ ] 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

System: macOS Sonoma 14.5

Hello!

I've tried injecting multiple channels to mv-hevc mov prores file using the Mp4box, but the number of channels is always reduced down to 3. 

Is it possible, and how, to inject multiple channels (like ambisonics or dolby 5.1)?

This is the command I used:
```shell
mp4box -new -add /path/video.mov -add /path/audio.aac  /path/finalvideo.mov
``` 

Injecting multichannel to mv-hevc with mp4box
This is a GitHub Issue
repo:gpac
owner:gpac
Title : Injecting multichannel to mv-hevc with mp4box
Issue date:

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

- [ ] I looked for a similar issue and couldn't find any.
- [ ] I tried with the latest version of GPAC. Installers available at https://gpac.io/downloads/gpac-nightly-builds/
- [ ] 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

System: macOS Sonoma 14.5

Hello!

I've tried injecting multiple channels to mv-hevc mov prores file using the Mp4box, but the number of channels is always reduced down to 3. 

Is it possible, and how, to inject multiple channels (like ambisonics or dolby 5.1)?

This is the command I used:
```shell
mp4box -new -add /path/video.mov -add /path/audio.aac  /path/finalvideo.mov
``` 

--- end body ---
