[Enhancement] Bluetooth audio using bluez-alsa

[andrew-ws]

Starting a new issue as I think this is different enough from the related Circuit Sword issue and the forum discussion. With a Pi Zero W bluetooth works right out of the box (as it's on the board) but audio is a bit trickier to set up. Pulse-audio is an option but probably requires reworking a large part of the audio configuration.

I've stumbled upon bluez-alsa (bluealsa on the repos) which provides an alsa backend for bluez. Just installing it gets me pretty far, lets me connect successfully to the headphones and play sounds from the CLI using aplay -D bluealsa:HCI=hci0,DEV=<mac>,PROFILE=a2dp <file> (from here). Also capable of controlling the volume in a similar way. So, getting pretty close.

The problem is I know very little about ALSA, or how retropie is interfacing with it. I tried following the last few steps in this retropie tutorial but it didn't seem to register in emulationstation and I'm not getting sound from anything. Also have no idea how to set it up so it can do both and switch automatically, which would be nice to have.

Going to keep looking at this but would appreciate some help from someone who understands the audio configuration here. This is most immediately relevant to the Circuit Gem but seems like it would be useful for people who got bluetooth working on the Sword as well.