Bluetooth

Bluetooth on Linux

• Bluetooth headset - Archlinux wiki

Lot of detailed information.

Bluetooth codecs

Some detailed information:

• Understanding Bluetooth codecs - SOUNDGUYS.
• The ultimate guide to Bluetooth headphones: Wired is still king for quality - SOUNDGUYS

Mention the new SONY WH-1000XM3 !

• Audio quality of SBC XQ Bluetooth audio codec - SoundExpert

Including a long discussion on the support of SBC_XQ on PulseAudio, available patches, and faulty devices.

Tips

Sony WH-1000XM3

Reference

• https://www.redpill-linpro.com/techblog/2021/05/31/better-bluetooth-headset-audio-with-msbc.html
• https://blog.oblivioncoding.pro/sony-wh-1000mx3-linux-fix/

• However tip on headset-roles seems outdated (does not seem necessary).

• https://gitlab.freedesktop.org/pipewire/pipewire/-/issues/604
• See also Pipewire.

Troubleshooting

bluetoothctl info 38:18:4C:4B:6A:3A
bluetoothctl info 38:18:4C:4B:6A:3A | grep -i battery

Tips

• For better support, install latest pipewire wireplumber package.
• Best playback codec is SBC_XQ. Select it in Gnome setting - Sound, or through pactl:

pactl set-card-profile bluez_card.38_18_4C_4B_6A_3A a2dp-sink-sbc_xq

• For confcall, use the mSBC codec. Again select it Gnome settings - Sound, or:

pactl set-card-profile bluez_card.38_18_4C_4B_6A_3A headset-head-unit-msbc

• View headset battery level in Gnome settings - Power. This requires enabling the bluetooth expiremental API [1]:

sudo systemctl edit bluetooth.service
# Edit file as:
# (file is /etc/systemd/system/bluetooth.service.d/override.conf)
#
#     [Service]
#     ExecStart=
#     ExecStart=/usr/libexec/bluetooth/bluetoothd --experimental
#
sudo systemctl restart bluetooth.service

Media control

• MPRIS - archlinux Here they say that WH-1000XM3 supports AVRCP, and that MPRIS-bluetooth is not required. It only requires to setup keyboard shortcuts.

• Key is detected by xev.
• In Gnome Settings - Keyboard, we can indeed register a custom shortcut with the headset tap as event (key is called Audio play).
• ... however eventhough we can register an event, this event is never triggered (we still see an icon with circle + cross being displayed)
• See AskUbuntu User reports various findings. Also one fix could be that some applications (Chrome...) were grabbing the event already.

• Volume control (swipe up / down), only works while Gnome Settings is opened.
• Tapping event.

We start dbus-monitor, and tap on the right headset. We see:

dbus-monitor
# ...
# signal time=1651003988.635770 sender=:1.41 -> destination=:1.76 serial=3196 path=/org/gnome/Shell; interface=org.gnome.Shell; member=AcceleratorActivated
#    uint32 121
#    array [
#       dict entry(
#          string "timestamp"
#          variant             uint32 6735577
#       )
#       dict entry(
#          string "action-mode"
#          variant             uint32 1
#       )
#       dict entry(
#          string "device-node"
#          variant             string "/dev/input/event13"
#       )
#    ]
# ...

If we connect to given device, we get a string whenever we tap on the headset:

sudo cat /dev/input/event13 | xxd
# 00000000: 8653 6862 0000 0000 9822 0e00 0000 0000  .Shb....."......
# 00000010: 0100 c800 0100 0000 8653 6862 0000 0000  .........Shb....
# 00000020: 9822 0e00 0000 0000 0000 0000 0000 0000  ."..............
# 00000030: 8653 6862 0000 0000 ec4d 0e00 0000 0000  .Shb.....M......
# 00000040: 0100 c800 0000 0000 8653 6862 0000 0000  .........Shb....
# 00000050: ec4d 0e00 0000 0000 0000 0000 0000 0000  .M..............
# ...