Can NRF Connect SDK 2.5.0 handles 7.5 ms ISO Interval for LE Audio?

[airfox230103]

Hi, 
I am using NRF5340 with SDK 2.5.0 RC2 to develop a low latency headset prototype, my target configuration is 24KHz sampling rate with 7.5ms SDU Interval.

But when I trace the code I found the SDK uses "Interger Veriable" and Macro to handle floating point arithmetic. For example, in "audio_datapath_stream_out()", the sentence "if (pcm_size != (BLK_STEREO_SIZE_OCTETS * NUM_BLKS_IN_FRAME))"  will always be true since the NUM_BLKS_IN_FRAME in 7.5ms ISO interval will be 7500/1000 = 7 but not 7.5 since it is a macro.

After fix this issue, I can connect NR5340 Headset to Win11 Audio Source Platform and play audio stream, unfortunately the audio stream sound obscure and noisy. And "

audio_datapath_i2s_blk_complete()" always shows "Data received, total underruns: xxx".

I wonder if NRF5340_Audio application in SDK 2.5.0 RC2 can be configured  in 24KHz with 7.5ms SDU interval, please you advise me the proper configuration, thanks.

 

 

[ovrebekk]

Hi 

Unfortunately we only support an SDU interval of 10ms, so this configuration will not be possible. We hope to support 7.5ms interval at some point in the future, but it is too early to tell when this will be ready. 

Out of curiosity, did you ever test with a 10ms SDU interval in Windows? We have had limited success getting LE Audio streaming to work with Windows hosts internally. 

Best regards
Torbjørn