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TL;DR

What: doc to play sound on PI
How: via Bluetooth + PulseAudio
Aim: Synced Multi-room Audio receiver/issuer that works with as many equipment as possible

Versions

This doc will often update to add new features and stuff.
See

Configuration

Hardware

I use:

Raspberry PI 3
Hifiberry AMP+
16GB SD Card (8GB is enough)
USB WiFi dongle (because there's an issue on using Bluetooth and WiFi together)
Power Supply: Meanwell GS60A18-P1J
Speakers: 2x Scandyna MicroPod SE (not a good idea, one should prefer Eltax Monitor III)

Software

OS

I use current stable release of Raspbian: Jessie
You just have to install it on a SD flash card:

Configure Hifiberry AMP+ (optionnal)

Go to the dedicated page

Force static names for wlan interfaces

Whitelist wlan devices.

vim /lib/udev/rules.d/75-persistent-net-generator.rules
8------------------------------------------------------------------------8
- KERNEL!="ath*|msh*|ra*|sta*|ctc*|lcs*|hsi*", \
+ KERNEL!="ath*|wlan*[0-9]|msh*|ra*|sta*|ctc*|lcs*|hsi*", \
8------------------------------------------------------------------------8

/etc/udev/rules/70-persistent-net.rules file will be created after reboot containing fixed wlan names according to MAC addresses.

Disable default wireless and enable the dongle

Unload the kernel module of raspberry3 wireless card

modprobe -r -v brcmfmac
vim /etc/modprobe.d/raspi-blacklist.conf
8------------------------------------------------------------------------8
#wifi
blacklist brcmfmac
#blacklist brcmutil
8------------------------------------------------------------------------8

Configure wlan0 which is now the only wlan card

vim /etc/network/interfaces
8------------------------------------------------------------------------8
auto wlan0
allow-hotplug wlan0
iface wlan0 inet manual
    wpa-conf /etc/wpa_supplicant/wpa_supplicant.conf
8------------------------------------------------------------------------8

Edit wpa_supplicant.conf according to your WiFi specs.

Reboot and be ready

shutdown -r now

Test sound

scp some mp3 file to the PI and play it:

apt-get update
apt-get install mplayer -y
amixer sset 'Master'  -- 70%
mplayer 02.\ I\ Fink\ U\ Freeky.mp3

=> Sound should be OK.
aplay -l should output only 1 card.

Bluetooth support

Install bluez + dependency to pulseaudio

apt-get install -y pulseaudio-module-bluetooth bluez-tools

Make the Bluetooth up at startup

vim /etc/systemd/system/bluetooth.target.wants/bluetooth.service
8------------------------------------------------------------------------8
    - ExecStart=/usr/lib/bluetooth/bluetoothd
    + ExecStart=/usr/lib/bluetooth/bluetoothd --noplugin=sap
8------------------------------------------------------------------------8

Configure class of BT. It defines what capabilities your BT will have (audio only / audio + micro / etc.).

vim /etc/bluetooth/main.conf
8------------------------------------------------------------------------8
# Changing name here has no effect
Class = 0x0c0420
8------------------------------------------------------------------------8

Configure PulseAudio

We need the 'pulse' user to access bluetooth via dbus

vim /etc/dbus-1/system.d/pulseaudio-bluetooth.conf
8------------------------------------------------------------------------8
<busconfig>

  <policy user="pulse">
    <allow send_destination="org.bluez"/> 
  </policy>

</busconfig>
8------------------------------------------------------------------------8

Restart dbus with systemctl restart dbus

PulseAudio on a desktop is not started as a deamon (Check out why). For a standalone sound system, we need it to be started as a system-wide daemon.

vim /etc/systemd/system/pulseaudio.service
8------------------------------------------------------------------------8
[Unit]
Description=Pulse Audio

[Service]
Type=simple
ExecStart=/usr/bin/pulseaudio --system --disallow-exit --disable-shm

[Install]
WantedBy=multi-user.target
8------------------------------------------------------------------------8

systemctl daemon-reload

Load bluetooth modules for pulseaudio

vim /etc/pulse/system.pa
8------------------------------------------------------------------------8
### Automatically load driver modules for Bluetooth hardware
.ifexists module-bluetooth-policy.so
load-module module-bluetooth-policy
.endif

.ifexists module-bluetooth-discover.so
load-module module-bluetooth-discover
.endif
8------------------------------------------------------------------------8

As the PI is used as a dedicated device for audio : No Restrictions on PI's consumptions = Best Audio quality possible (improvements are welcome)

vim /etc/pulse/daemon.conf
8------------------------------------------------------------------------8
cpu-limit = no
high-priority = yes
nice-level = -18
realtime-scheduling = yes
realtime-priority = 5

resample-method = ffmpeg
enable-remixing = no
enable-lfe-remixing = no

default-sample-format = s32le
default-sample-rate = 44100
alternate-sample-rate = 48000
default-sample-channels = 2
8------------------------------------------------------------------------8

systemctl --system enable pulseaudio.service
systemctl --system start pulseaudio.service

Custom Bluetooth name

echo 'PRETTY_HOSTNAME=$myawesomename' >> /etc/machine-info
service bluetooth restart

Manual pairing

example from archlinux doc

bluetoothctl
# bluetoothctl 
[NEW] Controller 00:10:20:30:40:50 pi [default]
[NEW] Device 00:12:34:56:78:90 myLino
[CHG] Device 00:12:34:56:78:90 LegacyPairing: yes
[bluetooth]# pair 00:12:34:56:78:90
Attempting to pair with 00:12:34:56:78:90
[CHG] Device 00:12:34:56:78:90 Connected: yes
[CHG] Device 00:12:34:56:78:90 Connected: no
[CHG] Device 00:12:34:56:78:90 Connected: yes
Request PIN code
[agent] Enter PIN code: 1234
[CHG] Device 00:12:34:56:78:90 Paired: yes
Pairing successful
[CHG] Device 00:12:34:56:78:90 Connected: no
[bluetooth]# connect 00:12:34:56:78:90
Attempting to connect to 00:12:34:56:78:90
[CHG] Device 00:12:34:56:78:90 Connected: yes
Connection successful

One needs to trust any paired device to avoid bluetoothd: authentication error

[bluetooth]# trust 00:12:34:56:78:90

Notification sounds

Play some sounds when:

PI starts
PI shuts down
Bluetooth device connects
Bluetooth device disconnects

Sounds

scp some short samples to PI.
I used /usr/local/share/sounds/ dir.
I force a lower volume to avoid unwanted_crazy_loud notifications.

Udev triggered script

I ran udevadm monitor --environment to monitor udev and kernel events.

vim /usr/local/bin/bluetooth-udev
8------------------------------------------------------------------------8
#!/bin/bash
# This script will play sound depending of event

NORMAL_SOUND_LEVEL=$(/usr/bin/amixer get Master | awk '$0~/%/{print $5}' |head -1 | tr -d '[]')
NOTIFICATION_SOUND_LEVEL=55%

# Reduce sound
/usr/bin/amixer sset 'Master' -- ${NOTIFICATION_SOUND_LEVEL}

# Trigger correct sound for each situation
if [ "$1" == 'device' ]
then
    case $ACTION in
        add)  # when device connects
            /usr/bin/mplayer --really-quiet /usr/local/share/sounds/portal/Hello.ogg
        ;;
        remove)  # when device disconnects
            /usr/bin/mplayer --really-quiet /usr/local/share/sounds/portal/Goodbye.ogg
        ;;
        *)  # unknown action of device
            /usr/bin/mplayer --really-quiet /usr/local/share/sounds/portal/Who_are_you.ogg
        ;;
    esac
elif [ "$1" == 'card' ]
then
    case $ACTION in
        add)  # when card is activated
            /usr/bin/mplayer --really-quiet /usr/local/share/sounds/portal/Activated.ogg
        ;;
        remove)  # when card is desactivated
            /usr/bin/mplayer --really-quiet /usr/local/share/sounds/portal/Shutting_down.ogg
        ;;
        *)   # unknown action of card
            /usr/bin/mplayer --really-quiet /usr/local/share/sounds/portal/Space.ogg
        ;;
    esac
fi

# Put sound at its original level
/usr/bin/amixer sset 'Master' -- ${NORMAL_SOUND_LEVEL}

exit 0
8------------------------------------------------------------------------8

chmod +x /usr/local/bin/bluetooth-udev

Allow users to play sound

Only members of 'pulse-access' group can connect to pulse audio daemon (therefore playing sound).
Allow root (udev will executes the script as root) to connect to pulseaudio

usermod -a -G pulse-access root

Add udev rule

Trigger the script via some udev rules

vim /etc/udev/rules.d/99-custom-bluetooth.rules
8------------------------------------------------------------------------8
# Triggered when bluetooth card is enabled
ACTION=="add", SUBSYSTEM=="bluetooth", KERNEL=="hci[0-9]*", RUN+="/usr/local/bin/bluetooth-udev card"

# Triggered when bluetooth card is disabled
ACTION=="remove", SUBSYSTEM=="bluetooth", KERNEL=="hci[0-9]*", RUN+="/usr/local/bin/bluetooth-udev card"

# Triggered when bluetooth device connects
ACTION=="add", SUBSYSTEM=="bluetooth", KERNEL=="hci0:[0-9]*", RUN+="/usr/local/bin/bluetooth-udev device"

# Triggered when bluetooth device DISconnects
ACTION=="remove", SUBSYSTEM=="bluetooth", KERNEL=="hci0:[0-9]*", RUN+="/usr/local/bin/bluetooth-udev device"
8------------------------------------------------------------------------8

Result

At this point, you have:

Autonomous system: just power it up and you can connect to it via bluetooth
Audio is playing on raspi speakers with A2DP protocol
Control volume/songs/everything with bluetooth device
PI plays sample sounds when desired

Details on project

This documentation aims people who got lost trying to make audio stuff with raspberry PI.
A lot of internet docs about PI & audio are deprecated because of old PI or old Operating System.
This one is to be used for Raspberry PI 3 + Raspbian Jessie. The Idea is to make a Sonos like multiroom soundsystem.

Why Bluetooth?

I tried several options and Bluetooth really is the best.

It works with all kind of modern equipments (Android, iStuff, laptops, etc.)
It's stable for years
Already packaged for Linux with PulseAudio support

Why PulseAudio?

Already packaged for Linux
It has a lot of modules to play with like bluetooth and RTP to stream audio over network

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