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Attention:

LDAC only works when you sending audio from PulseAudio (PA play as source, your Headphone/Speaker play as sink).

Cause we don't have a LDAC decoder library.

Which codec am I using?

Update on Fri, 15 Feb 2019 21:47:08 +0800 :

Simply check your pulseaudio profiles selecting menu.

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

Can I choose codec ?

Update on Fri, 15 Feb 2019 21:47:08 +0800 :

Yes.

1. Build&Install the latest pulseaudio-modules-bt from git.
2. Build&Install the latest bluez from git.
3. Edit bluetooth.service, append -E to /usr/lib/bluetoothd

# /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

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No, A2DP codec is chosen by bluez. Though the order of codecs is declared in this module, it is arranged by quality of codec(LDAC > APTX HD > APTX > SBC). It means if your device support APTX,LDAC,SBC, bluez will choose LDAC codec as primary codec.

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?

Updated: Check #1

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There still have several works to do. I will post all changes to PA after that.

Legacy: Sure，but I will wait Pali Rohár who at work on adding APTX support for Pulseaudio. You can check it at pulseaudio-discuss maillist . I will not join discussion about LDAC before they have a final solution about how multiply codec in pulseaudio mixed up. And my poor English is also a barrier.