On my ArchLinux KDE plasma setup, BT headphone will use A2DP only when connected by pairing; after disconnect and reconnect, only HSP/HFP is available

According to EHfive/pulseaudio-modules-bt#14 (comment), this should soon become unnecessary

this workaround deploys a udev-rules to detect changes of BT dev and systemctl start fix-bt-a2dp to call fix-bt-a2dp.rb in background with correct user

basically a rewrite from https://gist.github.com/EHfive/c4f1218a75f95b076f0387403246de78, mainly because I want to avoid slowing down connecting of other BT devs

install this AUR first:

yay -S fix-bt-a2dp

run this command with root to set GUI session owner:

/usr/bin/fix-bt-a2dp set-user [user]

recently pulseaudio-modules-bt has added codec name after a2dp_sink profile, and pacmd list-cards tells that my MDR-1ABT only supports AptX...so I finally came up with a solution by telling fix-bt-a2dp what profile should be used for a device manually...(so fix-bt-a2dp will set card profile to what you assigned when connected)

bluetoothctl devices
# => Device 10:4F:A8:CE:DB:D2 MDR-1ABT
fix-bt-a2dp set-device-profile MDR-1ABT a2dp_sink_ldac
# currently known profiles are
#   a2dp_sink_sbc a2dp_sink_aac a2dp_sink_aptx a2dp_sink_aptx_hd a2dp_sink_ldac