[feature] Output to Output Routing #58

What problem does this solve?

I am using the Audeze Maxwell 2 headphones via a 3.5mm cable that goes to an audio mixamp that I have. I want to use the USB-C dongle that is included with the headphones to make them truly wireless. However, in order to do that I have to be able to route audio from the 3.5mm headphone output on the mixamp to the USB-C dongle that comes with the headphones. I am using the "Giabuao USB C to 3.5mm Audio Adapter with CX31993+MAX97220 DAC Amplifier" to adapt the 3.5mm output to USB to be able to plug into the Raspberry Pi 5 8GB edition that I have. The problem I have is that I cannot seem to route the output from one speaker to another.

Proposed solution

Perhaps I am doing something wrong, which I am fully open to, but otherwise I think the easiest solution is to allow routing from one output to another.

Alternatives considered

I have tried the project hAudio which is designed for a raspberry pi. However, it expects the USB device chosen to have both an input and an output. The mixamp is only an output so the USB-C adapter for that doesn't have an input and therefore the project doesn't work for me as intended

Additional context

The normal project install via AppImage or .deb file doesn't work natively on the Pi because its arm64. I have compiled the source and after some dependency chasing got it to work. Aside from the below error I believe everything is working as it should.

(splitwave:139721): Gtk-CRITICAL **: 10:16:07.018: gtk_widget_hide: assertion 'GTK_IS_WIDGET (widget)' failed

I think the project is fantastic. Thank you for creating it and considering this enhancement.