I have a multichannel microphone connected to an android phone (pixel 3) through usb. I'm trying to use MediaRecorder API for recording audio. However, there doesn't seem to be a way to setup multichannel recording with MediaRecorder even though Android USB audio documentation seems to say it allows multichannel input. I know recording multi channel audio is possible, as there are apps that already do that (see ntrack). I'm trying to figure out how to do this and hoping it doesn't involve writing usb driver (like these developers).
If you can see your microphones as separate input devices using audioService.getDevices(AudioManager.GET_DEVICES_INPUTS) then you can use the AAudio API (preferably using Oboe library) to access each of these microphones by opening stream for each.