This gist will show how to setup Raspbian Stretch as a headless Bluetooth A2DP audio sink. This will allow your phone, laptop or other Bluetooth device to play audio wirelessly through a Rasperry Pi.
A quick search will turn up a plethora of tutorials on setting up A2DP on the Raspberry Pi. However, I felt this gist was necessary because this solution is:
- Automatic & Headless - Once setup, the system is entirely automatic. No user iteration is required to pair, connect or start playback. Therefore the Raspberry Pi can be run headless.
- Simple - This solution has few dependencies, readily available packages and minimal configuration.
- Up to date - As of December 2017. Written for Raspbian Stretch & Bluez 5.43
- Raspbian Stretch - I used the Lite version as this is a headless setup. See the official guide if you need help.
- Bluez-alsa - Available in the Raspbian package repo. This software allows us to stream A2DP audio over Bluetooth without PulseAudio.
- Raspberry Pi with Bluetooth - The Raspberry Pi 3 has integrated Bluetooth, however there is a known bug when the WiFi is used simultaneously. Cheap USB Bluetooth dongles work equally well.
Disabling Integrated Bluetooth
If you are using a separate USB Bluetooth dongle, disable the integrated Bluetooth to prevent conflicts.
To disable the integrated Bluetooth add the following
# Disable onboard Bluetooth dtoverlay=pi3-disable-bt
/boot/config.txt and execute the following command
sudo systemctl disable hciuart.service
First make sure the system is up to date using the following commands.
sudo apt-get update sudo apt-get upgrade
Then reboot the Pi to ensure the latest kernel is loaded.
Now install the required packages.
sudo apt-get install bluealsa python-dbus
Make Bluetooth Discoverable
Normally a Bluetooth device is only discoverable for a limited amount of time. Since this is a headless setup we want the device to always be discoverable.
- Set the DiscoverableTimeout in
# How long to stay in discoverable mode before going back to non-discoverable # The value is in seconds. Default is 180, i.e. 3 minutes. # 0 = disable timer, i.e. stay discoverable forever DiscoverableTimeout = 0
- Enable discovery on the Bluetooth controller
sudo bluetoothctl power on discoverable on exit
Install The A2DP Bluetooth Agent
A Bluetooth agent is a piece of software that handles pairing and authorization of Bluetooth devices. The following agent allows the Raspberry Pi to automatically pair and accept A2DP connections from Bluetooth devices. All other Bluetooth services are rejected.
Copy the included file a2dp-agent to
/usr/local/bin and make the file executable with
sudo chmod +x /usr/local/bin/a2dp-agent
Testing The Agent
Before continuing, verify that the agent is functional. The Raspberry Pi should be discoverable, pairable and recognized as an audio device.
Note: At this point the device will not output any audio. This step is only to verify the Bluetooth is discoverable and bindable.
- Manually run the agent by executing
- Attempt to pair and connect with the Raspberry Pi using your phone or computer.
- The agent should output the accepted and rejected Bluetooth UUIDs
A2DP Agent Registered AuthorizeService (/org/bluez/hci0/dev_94_01_C2_47_01_AA, 0000111E-0000-1000-8000-00805F9B34FB) Rejecting non-A2DP Service AuthorizeService (/org/bluez/hci0/dev_94_01_C2_47_01_AA, 0000110d-0000-1000-8000-00805f9b34fb) Authorized A2DP Service AuthorizeService (/org/bluez/hci0/dev_94_01_C2_47_01_AA, 0000111E-0000-1000-8000-00805F9B34FB) Rejecting non-A2DP Service
If the Raspberry Pi is not recognized as a audio device, ensure that the bluealsa package was installed as part of the Initial Setup
Install The A2DP Bluetooth Agent As A Service
To make the A2DP Bluetooth Agent run on boot copy the included file bt-agent-a2dp.service to
Now run the following command to enable the A2DP Agent service
sudo systemctl enable bt-agent-a2dp.service
Bluetooth devices should now be able to discover, pair and connect to the Raspberry Pi without any user intervention.
Testing Audio Playback
Now that Bluetooth devices can pair and connect with the Raspberry Pi we can test the audio playback.
bluealsa-aplay is used to forward audio from the Bluetooth device to the ALSA output device (sound card).
Execute the following command to accept A2DP audio from any connected Bluetooth device.
bluealsa-aplay -vv 00:00:00:00:00:00
Play a song on the Bluetooth device and the Raspberry Pi should output audio on either the headphone jack or the HDMI port. See this guide for configuring the audio output device of the Raspberry Pi.
Install The Audio Playback As A Service
To make the audio playback run on boot copy the included file a2dp-playback.service to
Now run the following command to enable A2DP Playback service
sudo systemctl enable a2dp-playback.service
Reboot and enjoy!
Low Volume Output
If you are experiencing low volume output, run
alsamixer and increase the volume of the Pi's soundcard.