NRF5340 Audio DK - LC3 SNR testing

[OVJA]

Hello,

I am wondering if anyone has any measurements of the LC3 SNR / Distortion measurments on the NRF5340.

I have tried with the Audio DK but beleve im just running into the limitations of the microphone / codec.

Or if anyone has a USB to USB audio bridge firmware that would only limit it to the preformance of the LC3 codec that would be super helpfull.

Regards

Jack 

[Maria Gilje]

Hello Jack,

It is important to know that measurements of SNR and distortion is not a good way to gauge the performance of the LC3 codec. This is because the testing method used to optimize the codec is a perceived quality test. The perceived quality is based on human hearing and audio masking is used to further increase the perceived quality. This audio masking may negatively impact the measurements for SNR and distortion while positively impacting the perceived quality.

We have performed tests with our hardware to measure SNR and distortion, but I am still waiting for data. And while these measurements are not suited to judge the performance of the codec, it may shed some light on the audio chain on the nRF5340 Audio DKs.

Hope this clears some things up.

Kind Regards,
Maria

[OVJA]

Hello Maria,

Any updates on the results. I understand the the codec is a precieved audio quality and will act dynamicaly on the signal. however knowing these values will show what it does to the actual signal.

Kind Regards

Jack

[Maria Gilje]

Hello Jack,

No updates, sorry about that. I have asked again.

Thank you for your patience.

Kind Regards,
Maria

[Maria Gilje]

Hello again,

I have been informed that I can't share the measurements for the LC3.

Here are some resources for you to gain a better understanding of the LC3 codec:

1. A Technical Overview of LC3 from Bluetooth. This article presents LE Audio and also links to a demonstration of the audio after it has been encoded and decoded.
2. The LC3 codec is optimized w.r.t. speech and music. The Wikipedia articles on PESQ and PEAQ has some information on how perceptual testing works.
3. Chapter 5 of Introducing Bluetooth LE Audio book by Nick Hunn contains technical information on the LC3 codec. It is free to download.
4. Google has a standalone tool for encoding and decoding audio. You could take a look at that as well.

Kind Regards,
Maria