A2DP is the "Advanced Audio Distribution Profile" which describes how Bluetooth devices can stream stereo-quality audio to remote devices. It enables connecting high quality audio bluetooth devices, such as headphones and speakers, to your system.

Requirements

To connect to a given device you need working bluetooth on your machine and the following packages, one of which is non-free software which will require you to enable the non-free repository in your /etc/apt/source.list file.

apt-get install pulseaudio pulseaudio-module-bluetooth pavucontrol bluez-firmware

Once you have installed these packages, it may be necessary to restart the bluetooth and pulseaudio services:

service bluetooth restart

killall pulseaudio

Pairing

It is also highly recommended to install a graphical pairing tool. If you are using GNOME as your desktop environment, bluetooth-applet should already be installed from the gnome-bluetooth package.

If you are using an alternative desktop environment that does not already include graphical bluetooth tools, you can use the blueman-applet from the blueman package:

apt-get install blueman

Both of these applets will appear in the notification area of your desktop environment and will provide options for pairing and connecting to your speakers or headphones.

Pair your device as usual and give it the "trust" attribute. The "trust" attribute allows the device to automatically establish a connection to your machine when turned on and in range.

Configuring

Using pavucontrol from the pavucontrol package, it is really easy to setup A2DP for your device, and map connections to it. Your paired headphones should appear as an option to output audio.

Don't forget to put it in high quality mode (A2DP) in the configuration tab. This is necessary for some devices that have mixed mode.

Compatible devices

Any A2DP device should work out of the box.

If you still didn't bought one, the Creative WP-300 works very well and has a very very nice sound.

Troubleshooting

Refused to switch profile to a2dp_sink: Not connected

Bluetooth headset is connected, but ALSA/PulseAudio fails to pick up the connected device or there's no device to pick. This happens because GDM captures A2DP sink on session start, as GDM needs pulseaudio in the gdm session for accessibility. For example, the screen reader requires it. See 805414 for some discussion.

Workaround 1: disable pulseaudio in gdm

In order to prevent GDM from capturing the A2DP sink on session start, edit /var/lib/gdm3/.config/pulse/client.conf (or create it, if it doesn't exist):

autospawn = no
daemon-binary = /bin/true

After that you have to grant access to this file to Debian-gdm user:

chown Debian-gdm:Debian-gdm /var/lib/gdm3/.config/pulse/client.conf

You will also need to disable pulseaudio startup:

rm /var/lib/gdm3/.config/systemd/user/sockets.target.wants/pulseaudio.socket

In order to auto-connect a2dp for some devices, add this to /etc/pulse/default.pa:

load-module module-switch-on-connect

Reboot.

Now the sound device (bluetooth headset) should be accessible through pavucontrol and standard audio device manager.

Workaround 2: disable bluetooth in gdm

The actual solution package maintainers are looking into next is to simply disable the bluetooth sink in the gdm pulseaudio daemon so that it doesn't take over the device. Add this to /var/lib/gdm3/.config/pulse/default.pa:

#

# load system wide configuration
.include /etc/pulse/default.pa

### unload driver modules for Bluetooth hardware
.ifexists module-bluetooth-policy.so
  unload-module module-bluetooth-policy
.endif

.ifexists module-bluetooth-discover.so
  unload-module module-bluetooth-discover
.endif

This was first discovered in the Arch wiki.

Solution

The actual solution is for pulseaudio to release the Bluetooth device when it is not in use. This is discussed in the Pulseaudio 845938 which has a few upstream bugs pending as well that are related.