Bluetooth audio output

That’s interesting – and excellent news. Since I was under the impression that it no longer worked under Debian stretch, could you tell us if you did anything, other than what has already been discussed here?

It’s fantastically sporadic. In my testing I found that once it worked, it seemed to work permanently

About the audio synchronization, I don’t think it’s a Pulseaudio issue. I have just connected my bluetooth dongle and it is working perfectly. But I had to sacrifice wifi, it stopped being stable.

By the way I was testing Xiaomi TV Box and I have returned it to the seller because of same bluetooth audio lag. Maybe it is somehow connected with Amlogic chipsets.

Are you saying the audio lag has disappeared when using the external bluetooth dongle?

Yes

The AMLogic SoC and WiFi module are completely separate components.
Were you also using the on-board WiFi module, and were you connected to a 2.4Ghz network?

Connecting to a 2.4Ghz network will obviously degrade performance if you use Bluetooth simultaneously due to the proximity of the radios.

PulseAudio uses large buffers which can cause delays.
If there were issues with the on-board Bluetooth I’d expect you to experience dropouts / crackling.

Sam

No, nothing like dropouts, crackling or lags. It was clear all the time 2 second delay.

And yes, I have 2.4GHz WiFi. But when I connected external dongle, delay was gone even on WiFi.

As you seem familiar with Linux, you might want to look at GitHub - arkq/bluez-alsa: Bluetooth Audio ALSA Backend. This is what we would like to use in the future. It removes the need for PulseAudio.

Did you actually disable the internal Bluetooth adapter to confirm you were using the external one?
Did you confirm that disabling WiFi while using the internal adapter reduced latency?

I have not disabled internal Bluetooth, I have just switched to external one (select in bluetoothctl) and paired the receiver again. About disabled WiFi together with internal Bluetooth, I will try that.

You were right. Using internal bluetooth with wifi disabled, audio is synchronized. When I turn on the wifi, it starts to be out of sync. However it remains out of sync even after wifi is turned off. Vero needs to be rebooted to go back in sync.

Do you have a 5Ghz network? I’d be interested to know the results

I suspect when you disconnect from 2.4G the chip doesn’t idle and as such the issue isn’t remedied until reboot.

Sorry, I don’t have 5GHz router.

Understood. For playing back 4K content (which Vero 4K is intended for), you’ll want to avoid WiFi.

Sam