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

[Maria Gilje]

Hello,

I will look into this and get back to you as soon as I can.

Kind Regards,
Maria

[Maria Gilje]

Hello,

How to stream stereo audio to 2 sink DK from a source DK?

You can configure your gateway to connect to two headsets. The left and right channels of the stereo audio can be sent over one CIS. For the headsets to be able to decode stereo sound you need to configure the decoder setting.

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)

There may be a limit of two ACL links in connected stream mode (CIS). I have asked internally for more information on this. I will get back to you when I know more.

With four separate audios you would likely run out of processing power. The encoding needs a significant amount of the CPU, and as the encoder is a mono encoder, encoding stereo doubles the amount of processing power needed. For the current stage of our LE Audio implementation, the maximum number of channels which can be encoded at the same time is three or four. For four separate stereo audios you will unfortunately not have enough CPU power available on the nRF5340 Audio DK.

Kind Regards,
Maria

[Bala4nRF]

Maria Gilje said:

The left and right channels of the stereo audio can be sent over one CIS

I see Bluetooth SIG community mentioned max limit of CIS to be 31. Here does left and right channels contribute 2 CIS or they combine to form 1 CIS?
How can I connect 3rd(2nd) CIS to 3rd headset(nrf5340 DK) from gateway(nrf5340) with new audio channel(not the left and right channels which is active in 1st CIS) 

With nRF5340 user guide, I could only see that the configurations can be set to transmit same audio(left/right) to 'n' no of headsets(DK) using CIS. 
My motive is to stream multiple audio tracks(2 diff song) through different channel to different DK,

Thanks for your support

[Maria Gilje]

Hello,

I am doing a little more research on this and will get back to you tomorrow.

Thank you for your patience.

Kind Regards,
Maria

[Maria Gilje]

Bala4nRF said:

I see Bluetooth SIG community mentioned max limit of CIS to be 31. Here does left and right channels contribute 2 CIS or they combine to form 1 CIS?

The limit of 31 CIS in one CIG is from the Bluetooth specification. For the LE Audio Controller Subsystem for nRF53, the maximum CIS per CIG is two. Also, there is a maximum of two ACL links with the nRF53 LE Audio controller. Each ACL link can control one CIG or both CIS in the same CIG separately.

The left and right channels can be combined to form 1 CIS.

Bala4nRF said:

How can I connect 3rd(2nd) CIS to 3rd headset(nrf5340 DK) from gateway(nrf5340) with new audio channel(not the left and right channels which is active in 1st CIS) 

This is not possible with the current controller. Each connected device needs an ACL and the maximum number of ACL links is 2. The BIS mode is the only mode supporting streaming to more than two devices at this point.

Bala4nRF said:

With nRF5340 user guide, I could only see that the configurations can be set to transmit same audio(left/right) to 'n' no of headsets(DK) using CIS. 

Yes, this is the way the application implements stereo -- two kits needed for left and right output. 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.

Bala4nRF said:

My motive is to stream multiple audio tracks(2 diff song) through different channel to different DK,

Two different songs with stereo audio will need four channels to be encoded, which will surpass the processing power available. You are free to test if a lower sample rate for the audio will make the processing power decrease enough to make it work. This is just speculation from my side, though.

Kind Regards,
Maria