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Q & A

LDAC receiver?

Not implemented because Sony only open-sourced LDAC encoder.

See https://android.googlesource.com/platform/external/libldac & https://github.com/EHfive/ldacBT

In this module, LDAC only works when you sending audio from PulseAudio (this module as source, Headphone/Speaker as sink).

Which codec currently activated?

answer 1

Simply check your pulseaudio profiles selecting menu.

answer 2

Run pactl list sinks | grep -e bluez -e a2dp_codec or pactl list sources | grep -e bluez -e a2dp_codec .

How to choose codec ?

1. Install latest pulseaudio-modules-bt.
2. Install bluez >= 5.51.
3. Edit bluetooth.service, append -E to /usr/lib/bluetoothd; Run systemctl daemon-reload Step not needed after bluez 5.52

# /usr/lib/systemd/system/bluetooth.service
[Unit]
Description=Bluetooth service
Documentation=man:bluetoothd(8)
ConditionPathIsDirectory=/sys/class/bluetooth

[Service]
Type=dbus
BusName=org.bluez
ExecStart=/usr/lib/bluetoothd -E
NotifyAccess=main
#WatchdogSec=10
#Restart=on-failure
CapabilityBoundingSet=CAP_NET_ADMIN CAP_NET_BIND_SERVICE
LimitNPROC=1
ProtectHome=true
ProtectSystem=full

[Install]
WantedBy=bluetooth.target

4. Restart bluetooth, pulseaudio (pulseaudio -k or systemctl --user restart pulseaudio)
5. Select codec profile in Pulseaudio device/card profiles menu, or, use command pactl set-card-profile

LDAC Bitrate Table

abrQualityModeID	LDAC encoding quality	Input PCM frequency	Bitrate
0	High Quality	48khz, 96khz	999kbps
		44.1khz, 88.2khz	909kbps
1	Standard Quality	48khz, 96khz	660kbps
		44.1khz, 88.2khz	606kbps
2	(ABR only)	48khz, 96khz	492kbps
		44.1khz, 88.2khz	452kbps
3	(ABR only)	48khz, 96khz	396kbps
		44.1khz, 88.2khz	363kbps
4	Mobile use Quality	48khz, 96khz	330kbps
		44.1khz, 88.2khz	303kbps

In LDAC Adaptive Bit Rate (ABR) mode, LDAC ABR library would detect transmission quality (mostly related with radio environment) and choosing reasonable LDAC encoding quality profile.

(You can find abrQualityModeID in libldac source code)

Are there any plans to upstream this into PulseAudio?

No. See #1.