Query - nRF5340 Audio DK - Configuration to Stream Multiple Stereo Audio

[Bala4nRF]

Hello,

I have 3 nRF5340 Audio DK. With the steps mentioned in below links, I configured Json file to stream left/right audios and I'm able to achieve it.

https://developer.nordicsemi.com/nRF_Connect_SDK/doc/2.0.2/nrf/applications/nrf5340_audio/README.html
https://www.youtube.com/watch?v=ZtNflUO8IC0

How to stream stereo audio to 2 sink DK from a source DK?
How to do multi-streaming to 3 or more DK? (Usecase: I want to stream 4 separate audios at a same time to 4 separate sinks from a source)

Thanks

[Bala4nRF]

Thanks for the detailed information.

Could you please clarify some additional points here,

Maria Gilje said:

The BIS mode is the only mode supporting streaming to more than two devices at this point.

Is auracast possible with nRF5340? As BIS is connectionless, how many streams possible in BIS mode?
Usecase : Stream 2 stereo audios / 4 Mono audios in BS mode from source. Headsets can tune into whatever they want.

Maria Gilje said:

You can modify the application to be able to stream stereo by combining the left and right channel after encoding and before sending the audio. In the application code, the combination needs to be done before streamctrl_encoded_data_send() is called in the encoder_thread() in src/audio/audio_system.

If I do this, both left and right channels will be able to receive same stereo audio? How can stereo be streamed through single channel of CIS? Are we merging two audios(left & right) to from mono, stream it via CIS and at the receiver(headset) do some logic to get stereo audio from mono?

Maria Gilje said:

You are free to test if a lower sample rate for the audio will make the processing power decrease enough to make it work.

I understand we can try to stream to more than 2 channels(CIS) even if its works, its expected to have some loss with low sampling rate. Here, is it possible to do changes in code such that source DK be able to take 2 stereo audio inputs at low sample rate, process and stream to 2 CIS at low sample rate. (Audio quality not important)

Instead of giving audio inputs from type c/3.5mm jack, Is it possible to change source code to take input from SD card having mp3 files? Could you point me code where I could start checking

Thanks once again!

[Maria Gilje]

Hello,

Bala4nRF said:

Thanks for the detailed information.

Happy to help!

Bala4nRF said:

Is auracast possible with nRF5340?

Currently, this is not supported, but it is planned.

Bala4nRF said:

As BIS is connectionless, how many streams possible in BIS mode?
Usecase : Stream 2 stereo audios / 4 Mono audios in BS mode from source. Headsets can tune into whatever they want.

Currently, the maximum amount of streams supported in the audio application is two. Note that any amount of headsets can subscribe to the stream. The maximum is the broadcast streams from the gateway.

I do not have conclusive information on how stereo streaming in BIS mode works in terms of channels in a BIS within a BIG. I can ask the developers for this information, and report back to you after the weekend.

Bala4nRF said:

If I do this, both left and right channels will be able to receive same stereo audio? How can stereo be streamed through single channel of CIS?

The receiving device will receive a merged stream which can be decoded and separated into the left and right channel. So when streaming the encoded audio stream, the left and right channels is merged into one isochronous stream.

Bala4nRF said:

Are we merging two audios(left & right) to from mono, stream it via CIS and at the receiver(headset) do some logic to get stereo audio from mono?

Yes we are merging the left and right channel mono audio into one stream. At the receiving device, some work is required to get the timing right.

This reply to a case and this case contains some useful information on how to get started with merging and separating streams.

Bala4nRF said:

I understand we can try to stream to more than 2 channels(CIS) even if its works, its expected to have some loss with low sampling rate. Here, is it possible to do changes in code such that source DK be able to take 2 stereo audio inputs at low sample rate, process and stream to 2 CIS at low sample rate. (Audio quality not important)

Yes, this is what I am suggesting as an experiment for you.

Bala4nRF said:

Instead of giving audio inputs from type c/3.5mm jack, Is it possible to change source code to take input from SD card having mp3 files? Could you point me code where I could start checking

Yes, this is possible. The Audio DK has an SD card holder. and you can find some reference code in the sd_card header and source files in nrf5340_audio/src/modules.

You can also encode the audio before loading it onto the SD card by using a standalone LC3 encoder. This will free up the CPU when running the application as well as storage space on the SD card.

Kind Regards,
Maria

[pfishburn]

"Bala4nRF said:

Is auracast possible with nRF5340?

Currently, this is not supported, but it is planned."

I see in the changelog for ncs 2.2.99 that "Possibility to create a Public Broadcast Announcement (PBA) needed for Auracast.". Is Auracast protocol implementation and a Auracast sample still being developed?

[Maria Gilje]

Hello,

Support for Auracast (TM) is not implemented yet. You can keep up to date with the supported features of the nRF5340 Audio application by looking at the feature support matrix in the intro section for the application.

Best Regards,
Maria

[RajendraN]

Hi Maria,

I am currently working on communicating between the nRF5340 DK and the nRF5340 Audio DK over BLE. Could you please share the information flow?

Warm regards,
Rajendra.