LE Audio Codec Sample Rate Configuration Issue with nRF5340-Based Hardware

[similingus]

I'm working with an nRF5340-based custom hardware setup that includes an audio codec and a microphone, and I'm testing LE Audio functionalities. My setup involves running the Audio Application Unicast server provided by Nordic (Ref: docs.nordicsemi.com/.../index.html) with a custom device tree and driver software for the additional hardware components.

I'm facing an issue with audio quality related to sample rate settings. Specifically, when configuring the AUDIO_SYSTEM_SAMPLE_RATE in /nrf5340_audio/src/audio/Kconfig to AUDIO_SAMPLE_RATE_48000_HZ, and the LC3 codec sample rate is settled with 16000 Hz or 24000 Hz, the audio transmitted from my device becomes severely distorted into loud noise on the receiving device, such as a phone. The noise is so loud that it sounds like it's hitting the maximum volume. Other combinations of LC3 sample rates and AUDIO_SYSTEM_SAMPLE_RATE do not produce this issue.

choice AUDIO_SYSTEM_SAMPLE_RATE
	prompt "System audio sample rate"
	default AUDIO_SAMPLE_RATE_48000_HZ
	help
	  This configuration reflects the system sample rate, but the audio data may be resampled to
	  another sample rate before encoding, and after decoding.

Why do the configurations cause such noise, and how can I avoid this problem?

I’m using NCS version 2.6.1.

Thank you for your assistance!

[similingus]

Hi Edvin,

Thank you for your response.

It does not occur when using an Audio DK.

For the HW codec, I’m using DA7212. The codec has its own sample rate setting register and supports common sample rates, including 16k, 24k 48k Hz, but changing it did not affect the observed trend of what combination produces the noise. I’m not sure about how it relates to the AUDIO_SYSTEM_SAMPLE_RATE and the LC3 codec’s sample rate from the HW codec’s datasheet.

Best,

Miho