Bluetooth Audio for (headless) PiOS systems

Introduction

Audio on Linux systems has always been rather complicated. ALSA (Advanced Linux Sound Architecture) is advanced indeed and thus even simple setups are complicated.

Bluetooth adds another level of complexity. And therefore the forums are full of posts asking for help on how to connect a Linux system with a bluetooth speaker or headset. This is no different with PiOs (Raspian).

You have two options: either use PulseAudio (fat, inflates a PiOS-lite installation by 50%), or bluez-alsa. Don't use "bluesalsa", an early fork of "bluez-alsa" which worked with Stretch, was broken with Buster and was removed from Bullseye.

This project aims to simplify the setup of bluez-alsa for Pi-systems. It does not support all kinds of configurations, its main aim is to support single-device setups, i.e. a Pi using a dedicated BT-speaker for audio output.

Note that functionality and stability of bluez-alsa varies with different hardware versions and OS-versions. The current status with bluez-alsa (version 3.1.0-78) for me:

• Buster 2021-05 works for Pi-Zero-W and Pi3B+
• Buster 2021-05 fails for Pi4 (BT speaker does not connect)
• Bullseye 2021-11 works, but BT speaker does not autoconnect

Prerequisites

To use bluez-alsa, you first have to manually pair the Pi with your device and establish a trust. This is done using the program bluetoothctl. Note that you have to add your user (typically pi) to the group bluetooth if necessary (check with e.g. id pi) and login again:

sudo usermod -a -G bluetooth pi

Pairing uses the commands from the following screenshot: .

You don't have to type all these numbers, just type the first few and then press the TAB key for autocompletion.

After pairing, note down the MAC address of your bluetooth-device, you will need it later for configuring ALSA.

Install bluez-alsa

Note that Raspbian/PiOS had a package "bluealsa" (removed in Bullseye). This package is broken, don't install it!

You can install bluez-alsa either from source (recommended), or using the deb-package provided from this project.

Installation from source is straightforward, the commands are from the bluez-alsa wiki:

tools/build-bluez-alsa

The drawback is that installation from source requires many development packages on your system. They are automatically downloaded but not everybody likes development tools on productive systems.

You might have to adapt the configure-command in that script, which currently only does a default build (plus systemd-support).

Installing the deb-package is much simpler, but that package was built for PiOS buster-lite (version 2021-05) using checkinstall and might or might not work for you:

sudo dpkg -i deb/arkq-bluez-alsa_3.1.0-78_armhf.deb
sudo apt-get -f -y install

The first command will give some errors, which the second command should fix (hopefully).

As a third alternative, you can build from source on one machine, create a deb-package and install it on another machine:

sudo apt-get -y update
sudo apt-get -y install checkinstall
tools/build-bluez-alsa deb

This will create the deb-package in the directory bluez-alsa/build.

Installation

To install all necessary software and the template configuration files, run the following commands:

git clone https://github.com/bablokb/pi-btaudio.git
cd pi-btaudio
sudo tools/install

The install script will

• install prerequisite-packages (see list in tools/install)
• create a sample /etc/asound.conf which will make your bluetooth-device the system-wide default audio-device
• install the utiliy-scripts btaudio-connect and btaudio-disconnect to manually connect and disconnect to the device

Configuration

After installation, edit the file /etc/asound.conf and insert the MAC address of your bluetooth-device in the line starting with defaults.bluealsa.device:

pcm.!default "bluealsa"
ctl.!default "bluealsa"
defaults.bluealsa.interface "hci0"
defaults.bluealsa.device "32:54:03:BB:CC:28"
defaults.bluealsa.profile "a2dp"

Note that you can run

bluetoothctl devices

which should give you the MAC-address of your bluetooth-speaker.

That's it for configuration, all scripts and daemons will use this MAC-address.

Now is the time to restart your system. After booting has finished and all daemons are up and running, your Pi should automatically connect to your speaker or headset. If not, run btaudio-connect.