Cannot choose arbitrary number of channels for JACK in Linux

[edumeneses]

As we're exploring using SpatGRIS in Linux systems at SAT, we realized it is impossible to choose an arbitrary number of channels when using JACK as the audio device type. The current behaviour is creating the same number as the chosen output device.

Choosing an arbitrary number of channels is helpful to route to non-default interfaces using Pipewire. Is there a way to do that?

Maybe a good suggestion is to add the option to choose how many input and output channels we want when using JACK, or creating as many channels as speakers configured at the speaker setup.

[edumeneses]

To add more info:

• Tested on Pop!_OS (Ubuntu-based) 22.04 using both ALSA and JACK (via Pipewire)
• ALSA behaves as expected: the inputs and outputs match the selected audio interface
• JACK behaves similarly to ALSA on my Linux system: I am forced to choose an interface (rather than choose an arbitrary number of channels)
• One workaround is to create a dummy (sink) Pipewire interface with the number of channels we want and choose the sink in SpatGRIS audio settings. After that, one can route the output of SPATGRUIS using Pipewire.

So this is more of a feature request than a bug. Having the option to choose the number of INs/OUTs independently helps with routing using Pipewire (which seems to be the audio server choice in modern Linux distributions).