Enable bluetooth A2DP on Raspberry-PI via pulseaudio. To install, edit /etc/udev/rules.d/99-input.rules and add the line: SUBSYSTEM=="bluetooth", RUN+="/usr/lib/udev/bluetooth" Then save this script as /usr/lib/udev/bluetooth and set it executable. Bluetooth devices must be linked first.

bluetooth-a2dp

#!/bin/bash
# This script is called by udev when you link a bluetooth device with your computer
# It's called to add or remove the device from pulseaudio
#
#

# Output to this file
LOGFILE="/var/log/bluetooth_dev"

# Name of the local sink in this computer
# You can get it by calling : pactl list short sinks
AUDIOSINK="alsa_output.platform-bcm2835_AUD0.0.analog-stereo"

# User used to execute pulseaudio, an active session must be open to avoid errors
USER="pi"

# Audio Output for raspberry-pi
# 0=auto, 1=headphones, 2=hdmi. 
AUDIO_OUTPUT=1

# If on, this computer is not discovearable when an audio device is connected
# 0=off, 1=on
ENABLE_BT_DISCOVER=1

echo "For output see $LOGFILE"

## This function add the pulseaudio loopback interface from source to sink
## The source is set by the bluetooth mac address using XX_XX_XX_XX_XX_XX format.
## param: XX_XX_XX_XX_XX_XX
## return 0 on success
add_from_mac(){
  if [ -z "$1" ] # zero params
	then
		echo "Mac not found" >> $LOGFILE
	else
		mac=$1 # Mac is parameter-1
		
		# Setting source name
		bluez_dev=bluez_source.$mac
		echo "bluez source: $mac"  >> $LOGFILE
		
		# This script is called early, we just wait to be sure that pulseaudio discovered the device
		sleep 1
		# Very that the source is present
		CONFIRM=`sudo -u pi pactl list short | grep $bluez_dev`
		if [ ! -z "$CONFIRM" ]
		then
			echo "Adding the loopback interface:  $bluez_dev"  >> $LOGFILE
			echo "sudo -u $USER pactl load-module module-loopback source=$bluez_dev sink=$AUDIOSINK rate=44100 adjust_time=0"  >> $LOGFILE
			
			# This command route audio from bluetooth source to the local sink..
			# it's the main goal of this script
			sudo -u $USER pactl load-module module-loopback source=$bluez_dev sink=$AUDIOSINK rate=44100 adjust_time=0  >> $LOGFILE
			return $?
		else
			echo "Unable to find a bluetooth device compatible with pulsaudio using the following device: $bluez_dev" >> $LOGFILE
			return -1
		fi
	fi
}

## This function set volume to maximum and choose the right output
## return 0 on success
volume_max(){
	# Set the audio OUTPUT on raspberry pi
	# amixer cset numid=3 <n> 
	# where n is 0=auto, 1=headphones, 2=hdmi. 
	amixer cset numid=3 $AUDIO_OUTPUT  >> $LOGFILE

	# Set volume level to 100 percent
	amixer set Master 100%   >> $LOGFILE
	pacmd set-sink-volume 0 65537   >> $LOGFILE
	return $?
}

## This function will detect the bluetooth mac address from input device and configure it.
## Lots of devices are seen as input devices. But Mac OS X is not detected as input
## return 0 on success
detect_mac_from_input(){
	ERRORCODE=-1
	
	echo "Detecting mac from input devices" >> $LOGFILE
	for dev in $(find /sys/devices/virtual/input/ -name input*)
	do
		if [ -f "$dev/name" ]
		then
			mac=$(cat "$dev/name" | sed 's/:/_/g')
			add_from_mac $mac
			
			# Endfor if the command is successfull
			ERRORCODE=$?
			if [ $ERRORCODE -eq 0]; then
				return 0
			fi
		fi
	done
	# Error
	return $ERRORCODE
}
## This function will detect the bt mac address from dev-path and configure it.
## Devpath is set by udev on device link
## return 0 on success
detect_mac_from_devpath(){
	ERRORCODE=-1
	if [ ! -z "$DEVPATH" ]; then
		echo "Detecting mac from DEVPATH"  >> $LOGFILE
		for dev in $(find /sys$DEVPATH -name address)
		do
			mac=$(cat "$dev" | sed 's/:/_/g')
			add_from_mac $mac

			# Endfor if the command is successfull
			ERRORCODE=$?
			if [ $ERRORCODE -eq 0]; then
				return 0
			fi

		done
		return $ERRORCODE;
	else
		echo "DEVPATH not set, wrong bluetooth device? " >> $LOGFILE
		return -2
	fi
	return $ERRORCODE
}


## Detecting if an action is set
if [ -z "$ACTION" ]; then
	echo "The script must be called from udev." >> $LOGFILE
	exit -1;
fi
## Getting the action
ACTION=$(expr "$ACTION" : "\([a-zA-Z]\+\).*")

# Switch case
case "$ACTION" in
"add")

	# Turn off bluetooth discovery before connecting existing BT device to audio
	if [ $ENABLE_BT_DISCOVER -eq 1]; then
		echo "Stet computer as hidden" >> $LOGFILE
		hciconfig hci0 noscan
	fi
	
	# Turn volume to max
	volume_max
	
	# Detect BT Mac Address from input devices
	detect_mac_from_input
	OK=$?
	
	# Detect BT Mac address from device path on a bluetooth event
	if [ $OK != 0 ]; then
		if [ "$SUBSYSTEM" == "bluetooth" ]; then
			detect_mac_from_devpath
			OK=$?
		fi
	fi

	# Check if the add was successfull, otherwise display all available sources
	if [ $OK != 0 ]; then
		echo "Your bluetooth device is not detected !" >> $LOGFILE
		echo "Available sources are:" >> $LOGFILE
		sudo -u $USER pactl list short sources >> $LOGFILE
	else
		echo "Device successfully added " >> $LOGFILE
	fi
	;;
	
"remove")
	# Turn on bluetooth discovery if device disconnects
	if [ $ENABLE_BT_DISCOVER -eq 1]; then
		echo "Set computer as visible" >> $LOGFILE
		sudo hciconfig hci0 piscan
	fi
	echo "Removed" >> $LOGFILE
	;;
	
#	
*)
	echo "Unsuported action $action" >> $LOGFILE
	;;
esac
echo "--" >> $LOGFILE

Thanks for this script!

I just put the script in my home directory with some changes since I'm not using pulseaudio. Its working, but the logfile isn't being created so I'm having a hard time troubleshooting. Does it have to run from /usr/lib/udev to make the log or something?

My bluetooth device is not getting detected. Any hints how to solve this?

Unable to find a bluetooth device compatible with pulsaudio using the following device: bluez_source.XX_XX_XX_XX_XX
Your bluetooth device is not detected !
Available sources are:
0	alsa_output.platform-soc_audio.analog-stereo.monitor	module-alsa-card.c	s16le 2ch 44100Hz	IDLE
--

@mschwarzer
I have same problem.

@malteos @00xBIT
This check is done by sudo -u $USER pactl list short sources and under sudo sources are not shown:

$ pactl list short sources
0	alsa_output.usb-Burr-Brown_from_TI_USB_Audio_DAC-00.analog-stereo.monitor
24	bluez_source.xx_xx_xx_xx_xx_xx.a2dp_source
$ sudo -u openhabian pactl list short sources
0	alsa_output.usb-Burr-Brown_from_TI_USB_Audio_DAC-00.analog-stereo.monitor

I haven't found solution for this problem, but I found out that audio is routing correctly without this script (probably newer pulseaudio or bluez is smarter). The only thing that I had to configure is setting default sink in /etc/pulse/client.conf:

; default-sink = alsa_output.usb-Burr-Brown_from_TI_USB_Audio_DAC-00.analog-stereo

My setup:

Operating System: Raspbian GNU/Linux 9 (stretch)
Kernel: Linux 4.14.94-v7+

Package: pulseaudio
Version: 10.0-1+deb9u1

Package: bluez
Version: 5.43-2+rpt2+deb9u2

There is a nice up to date project that you can use instead: https://github.com/nicokaiser/rpi-audio-receiver