RFE: Support for AptX LL (Low-Latency) codec

[pasikarkkainen]

AptX-LL (Low Latency) is meant for "Vital synchronised audio and video for gaming and multimedia applications". AptX LL has audio latency of around 32-40ms, which is much less than the other codec options currently available for Bluetooth audio. Currently supported AptX and AptX-HD codecs in libopenaptx have higher latency compared to AptX-LL.

[pali]

I do not have codec details for aptX Low Latency yet, nor any reference implementation for testing.

[pasikarkkainen]

Yep. For testing there are multiple BT receiver/transmitter dongles (with 3,5 mm analog audio connectors) out there, based on the Qualcomm CSR8670 chip, which support AptX LL. There's also the Qualcomm CSR8675 / BC8675, which also supports AptX HD in addition to Low Latency. Many of these devices can indicate the codec used with LEDs, and are OK for testing this stuff.

I personally have one of these devices, and can help with testing, if information about LL becomes available one day and can be implemented in libopenaptx.

Examples of such external devices: Inateck BR1006 / BR1008, Sonru Bluetooth 5.0 Transmitter Receiver, or Avantree Audikast. There are many other devices out there aswell.

[pali]

External HW player is not enough. For testing it is needed something which generates (or receive) aptX LL and decodes it to PCM. Some equivalent of decoder.

[pali]

Also aptX LL encoded samples are needed for development.

[pali]

@pasikarkkainen now from all information which I have, aptX Low Latency codec is just normal (non-hd) aptX codec with different A2DP parameters (smaller frame / mtu size, different vendor, configuration...).

Therefore available encoder in libopenaptx (and openaptxenc util) should be already able to generate aptX Low Latency stream and decoder should be able to decode it.

A2DP configuration and initialization is part of bluetooth stack, not codec library. Therefore I'm closing this issue as encoder+decoder for aptX Low Latency is already there.

[ValdikSS]

Can confirm that current version of libopenaptx successfully decodes aptX Low Latency-encoded audio.

[pali]

I have already experimental aptX-LL patches for pulseaudio and I will send them to mailing list after we fix issues around API and other stuff which is now more important.

[ashleysommer]

@pali any chance you can look at whether you can push your aptX-LL functionality into Pipewire a2dp?

[pali]

@pali any chance you can look at

yes, I have looked.

you can push your aptX-LL functionality into Pipewire a2dp?

No, I cannot. Devs&admins disallowed me to do it.

[ashleysommer]

I'm talking about Pipewire, not Pulseaudio. I thought the pipewire devs were much more receptive?

[pali]

They too, they have banned me from that project too.

[ashleysommer]

😞

[cleveHEX]

They too, they have banned me from that project too.

May I ask you why? Your contributions are very important for me, any chance it will be working in future?

[pali]

You are asking on wrong place. And there is no chance for future.