OPUS encoder sampling rate upper limits

RE: OPUS encoder sampling rate upper limits

Kenneth — Thu, 31 Mar 2022 08:03:11 GMT

The smart remote 3 was designed to transfer audio commands, not music, so the quality just needed to be good enough for the purpose and of course a trade-off between throughput/latency/power consumpton. I am not aware of any reason using better quality should not work (given you don't care about latency), but it's 3 years since it was launched, so I don't expect the developers have all the details anymore, I suggest if you want to change anyhthing you try it out and work through the issues you may see, it might also be that RAM/CPU will be the bottleneck.

Kenneth

RE: OPUS encoder sampling rate upper limits

Eggz — Thu, 31 Mar 2022 07:41:03 GMT

Mark,

We're using 16kHz sample rate in our application, so I'm afraid I'm not able to tell you if you're able to go beyond 32kHz. We have been focusing on minimizing system latency, and it works really well. Opus does a good job in terms of sound quality and we use 5ms frame size. Nordic team should be able to answer your sample rate question since they have experience with it from the SR3 demo. Opus codec can naturally support 48kHz, so this not the problem. My guess is that the only limitation limitation would be related to RAM/CPU as you suggest, but we haven't checked.

RE: OPUS encoder sampling rate upper limits

msat — Wed, 30 Mar 2022 22:02:06 GMT

Eggz,

Can you tell me about the sampling rate you're using? I want to know if allowing higher rates than those available in the SR3 demo is just a matter of changing the ifdefs to not return an error (ignoring RAM/CPU limitations for now), rather than it being some inherent limitation in the codec library itself.

RE: OPUS encoder sampling rate upper limits

Eggz — Wed, 30 Mar 2022 07:50:49 GMT

Hello Mark,
We are running Opus codec on nRF52840 and it works well, both on encoding and de-coding. We have developed a proprietary protocol based on ESB. There is quite a bit of work required on your side, but the good news is that it's possible. Nordic is talking about the off-the-shelf LE Audio solution on nRF5340, and if this doesn't work for you your original idea should be possible. Good luck.

RE: OPUS encoder sampling rate upper limits

msat — Sat, 26 Mar 2022 11:00:03 GMT

Hello Kenneth,

Thanks for the reply. The project I am working on will not be streaming [compressed] audio to something like a speaker, but rather to a client device (such as phone/tablet) acting as remote storage. In other words, the device is part of a wireless recording system. In this use case, OPUS/CELT encoding is nearly ideal. Using the LC3 codec from the LE audio spec in a custom implementation isn't out of the realm of possibility I suppose, but finding libraries that can transcode LC3 to something else later on in the chain is far more limited than using OPUS. LE audio, as such, is not useful for my project's needs.

RE: OPUS encoder sampling rate upper limits

Kenneth — Fri, 25 Mar 2022 13:27:21 GMT

Hello,

For audio streaming you should check out:
https://www.nordicsemi.com/Products/Bluetooth-LE-Audio

There is no plans for audio streaming on the nRF52-series (the smart remote 3 supported short "audio commands", but not audio streaming), you will need to use the nRF5340 for audio streaming. Currently you might find this useful:
https://www.packetcraft.com/post/packetcraft-s-bluetooth-le-audio-solution-supports-the-nordic-semiconductor-nrf5340-wireless-soc

To get more more information about Nordic Audio offering moving forward you will need to contact one of our regional sales manager.

Best regards,
Kenneth