Does anyone know how to remux and keep enhanced AC-3 with joint object control (JOC) with FFmpeg.
I'm remuxing a number of video files from MKV to MP4\M4V so they play on the Apple platform (including the TV App). It's important not to convert, but to remux.
I have achieved the ability to remux 4K HDR with Dolby Digital Plus in a .MKV to 4K HDR with Dolby Digtial 5.1. MP4. The issue is retaining the Dolby Digital Plus including JOC. This contains the Atmos information for object based sound.
The mediainfo tool reports Dolby Digital Plus with JOC for the MKV and Dolby Digital Plus without JOC for MP4. I know Dolby Labs to allow free remuxing of Dolby Digital Plus / Atmos with sample code and information they have uploaded onto GitHub for developers.
I'm using the following FFmpeg command:
ffmpeg -i original.mkv -c:v copy -c:a eac3 -tag:v hvc1 output.mp4
Resulting output from MediaInfo (note .MKV contains only 1 video and 1 audio track)
Audio (Original.mkv):
- ID: 2
- Format : E-AC-3 JOC
- Format/Info: Enhanced AC-3 with Joint Object Coding
- Commercial name: Dolby Digital Plus with Dolby Atmos
- Codec ID: **A_**EAC3
- Duration: 51 min 51 s
Audio (Remuxed.mp4):
- ID: 2
- Format: E-AC-3
- Format/Info: Enhanced AC-3
- Commercial name: Dolby Digital Plus
- Codec ID: ec-3
- Duration: 51 min 51 s
The remux operation finished in about 1 minute for a 8Gb 4k video file, so I know there is no reencoding.
I can see that the MP4 can take E-AC-3 Joint Object Control (JOC) with the demo files from Dolby labs.
I've also remuxed an MKV to MKV and able to see the same result. The JOC markings have been removed with FFmpeg.
