64Alpha8: Bluetooth: Volume not consistent after disconnect-reconnect

[baldrianbandit]

Describe the bug
Bluetooth volume is relatively low in general, I think. When connecting and setting a volume level, then disconnecting and reconnecting, the volume level is low again and - according to pulsemixer on my bluetooth client - different (lower) every time I reconnect it.

HiFiBerryOS version
64Alpha8

To Reproduce

1. Connect client via bluetoothctl connect
2. Start pulsemixer on client, see volume level, close pulsemixer
3. Disconnect client, then reconnect
4. Start pulsemixer on client, see volume level

Expected behavior
Bluetooth should either remember its last volume level or start at a fixed level on client connect.

Another suggestion: Using spotify-connect a lot, I disabled volume control of vollibrespot, so its output responds to global volume control only. I'd prefer that for bluetooth as well.

HifiberryOS is great! Thank you!

[baldrianbandit]

Extra info: To see the volume change in pulsemixer, there must be a source playing on bluetooth client. Otherwise, volume level will show 100%.

[hifiberry]

While this is a common problem as different BT devices use different volume implementations. Unfortunately there's nothing we can do about this to.

[baldrianbandit]

@hifiberry Workaround: Revert volume when device connects via bluetooth

1. Create udev rule

$ /etc/udev/rules.d/bt-add-event.rules
ACTION=="add", SUBSYSTEM=="bluetooth", TAG+="systemd", ENV{SYSTEMD_WANTS}="bt-add-event.service"

2. Create systemd unit

[Unit]
Description=Runs when bluetooth connection is added
Requires=bluetooth.target
After=bluetooth.target

[Service]
ExecStart=/usr/bin/bt-add-event.sh
Type=exec
Restart=always

[Install]
WantedBy=multi-user.target

3. Create script to reset volume

#!/usr/bin/sh
amixer sset DSPVolume 250

Further idea: Save volume on disconnect to a file and restore on reconnect