BlueALSA - andy3471/GBD GitHub Wiki

Background

BlueALSA is a Bluetooth audio ALSA backend. It adds ALSA support to BlueZ v5 and greater.

Bluez acts as a middleware between audio modules which implement Bluetooth audio profiles, and Bluetooth audio devices. BlueALSA registers all known Bluetooth audio profiles in Bluez, and supports an ALSA PCM I/O plugin which allows an ordinary audio application to access a Bluetooth audio stream.

NOTE: BlueALSA services are incompatible with PulseAudio Bluetooth. Most desktop distro's have PA installed as the default sound server. In the interests of consistency, only BlueALSA configurations will be considered. Also check out section Disabling PulseAudio Bluetooth.

On the other hand, a pristine Raspbian v9.4 (Stretch) installation doesn't ship with PA installed. A quick check could be:
```
pi@raspberrypi:~ $ apt-cache policy pulseaudio
pulseaudio:
  Installed: (none)
  Candidate: 10.0-1+deb9u1
  Version table:
     10.0-1+deb9u1 500
     500 http://raspb[...]/raspbian stretch/main armhf Packages
```

BlueALSA on Raspberry PI

The official Raspbian Stretch should ship with BlueALSA pre-installed. For instance, a quick check can be done with:

pi@raspberrypi:~ $ apt-cache policy bluealsa
bluealsa:
  Installed: 0.7
  Candidate: 0.7

pi@raspberrypi:~ $ ps ax | egrep '(bluetoothd|bluealsa)' | grep -v grep 
  658 ?        Ss     0:00 /usr/lib/bluetooth/bluetoothd
  665 ?        Ssl    0:00 /usr/bin/bluealsa

Otherwise, BlueALSA can be installed from the repositories via apt:

pi@rapberrypi:~ $ sudo apt-get install bluealsa

To check whether your Raspberry Pi's on-board BT device has audio capabilities (performed on a RPi Model 3B):
```
pi@raspberrypi:~ $ hciconfig -a hci0 | grep Audio
Service Classes: Rendering, Capturing, Audio, Telephony
```
Note that the bluealsa daemon should be running before executing this command; bluealsa is what provides the Bluetooth audio services on top of Bluez.

BlueALSA on Desktop GNU/Linux

This configuration is mainly relevant for economy GBD setups (see GBD Architecutre). Some distro's have native package support for BlueALSA. On the other hand, for instance, Ubuntu 16.04 LTS does not include BlueALSA in its official repos and a build from source is required. Please consult the appropriate distro documentation for instructions on BlueALSA build/installation.

Bluetooth Audio Services and Discovery

Before attempting to use BT audio in a GBD setup, check whether the BT devices support BT Audio services. With respect to GNU/Linux, BT Audio services will be available only if the bluealsa daemon is running (i.e. not considering PulseAudio BT services).

For instance, to perform Service Discovery Protocol (SDP) inquiries via sdptool(1):

First perform a BT ping between the devices to make sure that they can see each other.

SDP request from GNU/Linux PC to RPi:

$ sdptool browse 11:22:33:68:BC:15 | grep 'Service Name'  | grep Audio
Service Name: Audio Source
Service Name: Audio Sink

SDP request from RPi to GNU/Linux PC:

$ sdptool browse 43:29:12:DF:78:CD | grep 'Service Name' | grep Audio
Service Name: Audio Source

Alternatively, the info command via the bluetoothctl(1) interface could be used for SDP inquiries. However, it's output (although more verbose/detailed) seems to be less reliable.