OPUS encoder sampling rate upper limits

[msat]

Hello,

I recently started looking through the Smart Remote 3 code as I'm interested in potentially using a suitable nRF device + I2S ADC to encode and stream music using OPUS/CELT. Since I'm new to nRF products, there's a lot to digest here. Looking at sr3_config_nrf52832_custom.h, max sample rate is listed as 32kHz, and in drv_audio_codec_opus.c, the highest frequency is 24kHz.

What is the reason for these limits in the code? Is it RAM and/or CPU limitations? Is 48kHz sampling rate a possibility?

Thanks,

Mark

[Kenneth]

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

[msat]

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.