BlueZ5 and A2DP
A2DP stands for Advanced Audio Distribution Profile. This is the Bluetooth Stereo profile which defines how high quality stereo audio can be streamed from one device to another over a Bluetooth connection - for example, music streamed from a mobile phone to wireless headphones.
Although many products may have Bluetooth enabled for voice calls, in order for music to be streamed from one Bluetooth device to another, both devices will need to have this A2DP profile. If both devices to do not contain this profile, you may still be able to connect using a standard Headset or Handsfree profile, however these profiles will not support stereo music.
BlueZ5 configuration currently support A2DP both in server and client mode.
server mode
In server mode, you can connect via BT the board to a PC or a mobile phone and play an A2DP audio stream using onboard headphones. connector.
1. Start the device in A2DP server mode, running the following command (Into console of device):
# /opt/var-bluetooth-snd-dev/bluetooth-snd-server.sh
2. Scan and connecting the external device to Variscite board over bluetooth
3. Trust external device to Variscite board
# /opt/var-bluetooth-snd-dev/bluetooth-snd-server.sh -t C8:14:79:27:F1:82
where "bd address" we can get with command "hcitool scan"
For example:
# /opt/var-bluetooth-snd-dev/bluetooth-snd-server.sh
.. connect external device via bluetooth
# /opt/var-bluetooth-snd-dev/bluetooth-snd-server.sh -t C8:14:79:27:F1:82 [NEW] Controller F8:DC:7A:07:8D:A6 VAR-A2DP [default] [NEW] Device C8:14:79:27:F1:82 SM-T315 [bluetooth]# trust C8:14:79:27:F1:82 [bluetooth]# quit [DEL] Controller F8:DC:7A:07:8D:A6 VAR-A2DP [default]
On the client side, connect to the device VAR-A2DP and play sound through it.
For audio playback, make sure headphones or speakers are connected to the onboard headphones connector.
client mode
In client mode, you can connect and play A2DP audio stream using bluetooth headphones.
connect
Into console of device:
1. Start utility "bluetoothctl":
root@imx6ul-var-dart:~# bluetoothctl
example:
root@imx6ul-var-dart:~# bluetoothctl [NEW] Controller F8:DC:7A:07:8D:A6 VAR-A2DP [default] [NEW] Device C8:14:79:27:F1:82 SM-T315 [bluetooth]#
2. Prepare to сonnection:
[bluetooth]# power on [bluetooth]# agent on [bluetooth]# default-agent
example:
[bluetooth]# power on Changing power on succeeded [bluetooth]# agent on Agent registered [bluetooth]# default-agent Default agent request successful [bluetooth]#
3. The first time only, to connect BT headphones, make sure they are in pairing mode. They need to show up.
4. Enable scanning
[bluetooth]# scan on
example:
[NEW] Device 68:DF:DD:5D:CF:96 malupas [NEW] Device 00:06:F7:B3:E9:ED MM100 [NEW] Device 00:07:80:41:68:15 KTS540_0000000 [NEW] Device C8:14:79:27:F1:82 SM-T315 [bluetooth]# scan on Discovery started [CHG] Controller F8:DC:7A:07:8D:A6 Discovering: yes [CHG] Device 00:06:F7:B3:E9:ED RSSI: -57 [CHG] Device 00:07:80:41:68:15 RSSI: -65 [CHG] Device 68:DF:DD:5D:CF:96 RSSI: -98 [CHG] Device 00:07:80:41:68:15 RSSI: -73
"[NEW] Device 00:06:F7:B3:E9:ED MM100" are BT headphones.
5. Disable scanning
[bluetooth]# scan off
example:
[bluetooth]# scan off Discovery stopped [CHG] Controller F8:DC:7A:07:8D:A6 Discovering: no [bluetooth]#
6. Pair the device
[bluetooth]# pair 00:06:F7:B3:E9:ED
7. Connect the device
[bluetooth]# connect 00:06:F7:B3:E9:ED
example:
[bluetooth]# connect 00:06:F7:B3:E9:ED Attempting to connect to 00:06:F7:B3:E9:ED [CHG] Device 00:06:F7:B3:E9:ED Connected: yes Connection successful [MM100]#
8. Trust the device
[MM100]# trust 00:06:F7:B3:E9:ED
example:
[MM100]# trust 00:06:F7:B3:E9:ED [CHG] Device 00:06:F7:B3:E9:ED Trusted: yes Changing 00:06:F7:B3:E9:ED trust succeeded [MM100]#
9. quit from bluetoothctl console
[MM100]# quit
example:
[MM100]# quit [DEL] Controller F8:DC:7A:07:8D:A6 VAR-A2DP [default] root@imx6ul-var-dart:~#
play test sound using MM100 headphones
1. Check cards availability.
# pactl list cards
example:
root@imx6ul-var-dart:~# pactl list cards
Card #0
Name: alsa_card.platform-sound
Driver: module-alsa-card.c
Owner Module: 6
Properties:
alsa.card = "0"
alsa.card_name = "wm8731-audio"
alsa.long_card_name = "wm8731-audio"
device.bus_path = "platform-sound"
sysfs.path = "/devices/platform/sound/sound/card0"
device.string = "0"
device.description = "wm8731-audio"
module-udev-detect.discovered = "1"
device.icon_name = "audio-card"
Profiles:
input:analog-mono: Analog Mono Input (sinks: 0, sources: 1, priority: 2, available: yes)
input:analog-stereo: Analog Stereo Input (sinks: 0, sources: 1, priority: 60, available: yes)
output:analog-mono: Analog Mono Output (sinks: 1, sources: 0, priority: 200, available: yes)
output:analog-mono+input:analog-mono: Analog Mono Duplex (sinks: 1, sources: 1, priority: 202, available: yes)
output:analog-stereo: Analog Stereo Output (sinks: 1, sources: 0, priority: 6000, available: yes)
output:analog-stereo+input:analog-stereo: Analog Stereo Duplex (sinks: 1, sources: 1, priority: 6060, available: yes)
off: Off (sinks: 0, sources: 0, priority: 0, available: yes)
Active Profile: output:analog-stereo+input:analog-stereo
Ports:
analog-input-mic: Microphone (priority: 8700, latency offset: 0 usec)
Properties:
device.icon_name = "audio-input-microphone"
Part of profile(s): input:analog-mono, input:analog-stereo, output:analog-mono+input:analog-mono, output:analog-stereo+input:analog-stereo
analog-input-linein: Line In (priority: 8100, latency offset: 0 usec)
Part of profile(s): input:analog-mono, input:analog-stereo, output:analog-mono+input:analog-mono, output:analog-stereo+input:analog-stereo
analog-output: Analog Output (priority: 9900, latency offset: 0 usec)
Part of profile(s): output:analog-mono, output:analog-mono+input:analog-mono, output:analog-stereo, output:analog-stereo+input:analog-stereo
Card #6
Name: bluez_card.00_06_F7_B3_E9_ED
Driver: module-bluez5-device.c
Owner Module: 37
Properties:
device.description = "MM100"
device.string = "00:06:F7:B3:E9:ED"
device.api = "bluez"
device.class = "sound"
device.bus = "bluetooth"
device.form_factor = "headset"
bluez.path = "/org/bluez/hci0/dev_00_06_F7_B3_E9_ED"
bluez.class = "0x240404"
bluez.alias = "MM100"
device.icon_name = "audio-headset-bluetooth"
device.intended_roles = "phone"
Profiles:
headset_head_unit: Headset Head Unit (HSP/HFP) (sinks: 1, sources: 1, priority: 20, available: yes)
a2dp_sink: High Fidelity Playback (A2DP Sink) (sinks: 1, sources: 0, priority: 10, available: yes)
off: Off (sinks: 0, sources: 0, priority: 0, available: yes)
Active Profile: headset_head_unit
Ports:
headset-output: Headset (priority: 0, latency offset: 0 usec)
Part of profile(s): headset_head_unit, a2dp_sink
headset-input: Headset (priority: 0, latency offset: 0 usec)
Part of profile(s): headset_head_unit
We are interested in Card # 6.
2. Switch a2dp profile
# pactl set-card-profile <card #id from item 1> a2dp_sink
example:
root@imx6ul-var-dart:~# pactl set-card-profile 6 a2dp_sink root@imx6ul-var-dart:~#
3. play wav file from pulse subsystem to bluetooth headphones
# paplay -p --device=bluez_sink.XX_XX_XX_XX_XX_XX /usr/share/sounds/alsa/Front_Center.wav
Where:
XX_XX_XX_XX_XX_XX - bd_add from item 1 /usr/share/sounds/alsa/Front_Center.wav - is the file to be played
example:
root@imx6ul-var-dart:~# paplay -p --device=bluez_sink.00_06_F7_B3_E9_ED /usr/share/sounds/alsa/Front_Center.wav
FAQ
1. The sound doesn't play using headphones connector (board in server mode) or BT headphones (board in client mode).
ALSA may be configured incorrectly, use this command:
# amixer set 'Output Mixer HiFi' on
Pulseaudio server may be not started, use this command:
# pactl list cards
HCI interface may be down, use this command:
# hciconfig hci0 up