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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

Bitrate of LDAC

abrQualityModeID	LDAC encoding quality ⬇ | Input PCM frequency ➡	48khz, 96khz	44.1khz, 88.2khz
0	High Quality	990kbps	909kbps
1	Standard Quality	660kbps	606kbps
2	(ABR only)	492kbps	452kbps
3	(ABR only)	396kbps	363kbps
4	Mobile use Quality	330kbps	303kbps

LDAC Adaptive Bit Rate (ABR) mode detect the transmission quality and choosing LDAC encode quality as higher as possible.

Are there any plans to upstream this into Pulseaudio?

No. See #1.