Getting Multi channel audio to work

[stevefromNewcastle]

FPP 8.4.1
Pi 5
USB Soundcard Fasttrack Ultra 8R or Hifi Berry DAC8X

I am trying again to get multichannel audio playback to work on either of these sound cards and cannot get anything to output correctly.
I have 5.1 and 7.1 test files from https://fraunhofer.de/ in wav and mp4 format niether output correctly. Either they output the correct left and right audio but nothing on the other channels, or, all of the channels are played through the left and the right.

I have the files outputting correctly from cvlc but I cannot get fpp to output more than 2 channels.
Having looked at the logs it seems the file is passed through the SDL library where the audio is prepped according to the layout options of fpp.
Does anyone have a working test file that they have managed to get multi channel audio working on a soundcard not the HDMI?
Thanks for any help on this.
Steve

[patdelaney]

What would the use case be for this? Is this something that the average user would do? I don't know of any transmitters can take that input.

How would we test it?

[stevefromNewcastle]

It is already a feature i am just trying to get a working setup. For me it would be useful to have multiple outputs that I can run to separate powered speakers.

[darylc]

None of the developers have multi channel sound cards to work on this as far as we can tell.

[stevefromNewcastle]

I am more than happy to donate a couple of sound cards if that would help with this. How would I go about doing this?
S

[stevefromNewcastle]

As an update to this, I can get multi channel audio working on a USB soundcard upto 5.1 but not 7.1 On th 8 channel Dac, I can only get stereo, .
In cvlc I can get it to work correctly but I need to provide the addition --alsa-audio-channels 4967 to get it to work.
One option would be instead of the audio output device, you could select a device listed in aplay -L.