Channels jumbled after ffmpeg converson from Dolby Atmos to 6Ch WAV

[rudolffischer]

I have an m4a (E-AC3 JOC Dolby Atmos) of Diplo's MMXX Album. I can stream it from jRiver to my Onkyo PR-SC5007 via HDMI and the Onkyo shows Digital+ and jRiver shows 'Bitstreaming' in audio path. So far so good. However playback is not smooth and frequently interrupts. I attribute this to the Onkyo or jRiver not coping correctly with the Dolby Atmos metadata.
I have now converted the m4a file into a 6Ch WAV file using the following command;
ffmpeg -i "input.eac3" -acodec pcm_s24le -ar 48000 -ac 6 "output.wav"
This file now streams smoothly, but the channels are jumbled. I have much more sound coming from the rears than from the fronts. I have tread that ffmpeg sometimes makes a mess of channel mapping when converting. I am wondering whether this 'mess' is systematic and how I would need to remap channels to get a correct (preferably 4.0) channel mapping.
The m4a Dolby Atmos file works correctly. I played it at a friend's house on a Samsung Q995B soundbar and all sounds seemed to come from logical directions.
Any help is appreciated.

[pandy]

This may help https://trac.ffmpeg.org/wiki/AudioChannelManipulation#Remapchannels

[rudolffischer]

This may help https://trac.ffmpeg.org/wiki/AudioChannelManipulation#Remapchannels

Thanks, found it and will try a few things

[ProWo]

The channels are not swapped in the eac3 to wav conversion.
In the picture above the 6 eac3 channels, in the picture below the 6 wav channels.


[Attachment 77625 - Click to enlarge]

Used ffmpeg version 2024-02-26-git-a3ca4beeaa-full_build-www.gyan.dev

[rudolffischer]

I finally figured out what is probably going on here:
This is the channel assignment of the original E-AC3 JOC Dolby Atmos file:


[Attachment 77626 - Click to enlarge]

This sounds weird and I can see why. There is much more energy in the rear channels than in the front. After front / back reversal (in the MCh FLAC) this is what it looks like and it sounds fine.


[Attachment 77627 - Click to enlarge]

I have no clue why the channels were reversed in the original Dolby Atmos file.

[pandy]

I have no clue why the channels were reversed in the original Dolby Atmos file.

Different channel layout may be signaled separately...