nrf5340 audio: Minimal audio latency

[Reskyllr]

We are using the nrf5340 audio demo, and the audio delay currently tested in BIS mode is about 40ms.
We are trying to achieve lower transmission latency, without considering other factors.
Current attempts include: SDU size, number of retransmissions, CONFIG_BT_AUDIO_PRESENTATION_DELAY_US.
The above doesn't seem to reduce my latency.
Do you have any relevant suggestions? What configurations can be used to reduce it?

[Karl Ylvisaker]

Hello,

We are using the nrf5340 audio demo, and the audio delay currently tested in BIS mode is about 40ms.
We are trying to achieve lower transmission latency, without considering other factors.
Current attempts include: SDU size, number of retransmissions, CONFIG_BT_AUDIO_PRESENTATION_DELAY_US.
The above doesn't seem to reduce my latency.

Could you elaborate on how you made these modifications, and if you were able to verify whether they went into effect?
Could you also elaborate on your test setup for how you have measured the latency - is this the end-to-end latency you are measuring?

Best regards,
Karl

[Reskyllr]

Hi,Karl,

I modified it by
CONFIG_BT_AUDIO_MAX_TRANSPORT_LATENCY_MS=10
CONFIG_BT_AUDIO_RETRANSMITS=1
CONFIG_LC3_BITRATE=32000

Then,I measured the audio waveform at the analog input/output location and found the phase difference in.

Best regards,

Reskyllr

[Karl Ylvisaker]

Hello again, Reskyllr

Thank you for your extreme patience with this.
I have been out of office for some time, but now I am back.

Thank you for clarifying on what you did previously, and how you set up your test.
Please make sure to also change the presentation delay kconfig and let me know if you still do not see any impact on your latency.

Best regards,
Karl

[Ahmed Moheb]

Hi Reskyllr ,

Were you able to achieve a better end-to-end latency?

With previous SDK (version 2.4.0), I was able to measure ~31 ms for end-to-end test.
With SDK version 2.6.0, I got ~46 ms.

I couldn't find any major changes that should affect the latency and I've also tried tunning the presentation delay with no noticable effect to reduce the latency (increasing the PD increases the latency, but reducing it below 10 ms doesn't make a difference).

Thanks,

Ahmed

[Reskyllr]

Hi,Ahmed,

Please try the configuration above, I have now achieved an end-to-end latency (BIS) of 26ms.

Best regards,

Reskyllr

[Ahmed Moheb]

Hi Reskyllr ,

Thanks for sharing the configuration, I appreciate it.

Thanks,
Ahmed