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NRF5340: CIS Groups, and Streams: Stereo headset + stereo gateway + NUS?

EchoCharlieWhiskey

I have a CIS gateway (unicast client) and a CIS headset (unicast server). The BLE 5.4 spec seems to say each stream is bi-directional. So for my stereo headset and gateway, that is one CIG with two CIS? If I want them to be always-on, does that mean it needs to be one CIG with four CIS (as shown in the tested topologies)?

What if I want to add NUS? (See Integrate NUS into BLE Audio code post.) Does that consume one directional CIS? Or two CIS? 

Which of these are possible with NRF5340 SDK 2.5.1?

  1. Stereo headset and stereo gateway consume two bidirectional CIS. NUS uses one bidirectional CIS. There is CIS one open for the future.
  2. Stereo headset and mono gateway consume three CIS. NUS consumes the last one. 
  3. NUS consumes two CIS leaving only space for mono headset and mono gateway.

Does it matter what is running on the network core? (I'm planning to use LC3 but haven't gotten the paperwork done.)

Thank you!

ecw

  • 0 in reply to dejans

    Thank you, Dejan.

    From what you are saying, I understand I can't have stereo gateway to headset, mono headset to gateway with one unicast server. (This is surprising as I have it mostly working with only some I2S issues with my external codec. Though I would be worried about not doing supported things. There are many posts here about stereo functionality  (RE: nrf5340 Stereo Audio is the one i used to get stereo to my headset and mono back.)

    So you recommend, to get my desired functionality of stereo to headset, mono to gateway, I need to have two servers and use 8ii.

    Or if I want to have stereo to headset, stereo to gateway, I need to use two servers and 11ii.

    And I need to synchronize the stereo streams?

    Does that sound right?


  • 0 in reply to EchoCharlieWhiskey

    Hi,

    Which board do you use?

    EchoCharlieWhiskey said:
    So you recommend, to get my desired functionality of stereo to headset, mono to gateway, I need to have two servers and use 8ii.

    Or if I want to have stereo to headset, stereo to gateway, I need to use two servers and 11ii.

    Do you plan to use 2 physical devices in both cases?

    Best regards,
    Dejan

  • 0 in reply to dejans

    Yes, two physical devices, currently two nRF5340 Audio DK. 

    I have an external codec that can collect and output stereo audio, communicating via I2S to the nRF5340.

    Eventually, we will move to a a custom board and an Android application. 



  • +1 in reply to EchoCharlieWhiskey

    Hi,

    I had a discussion with our developers. Below are some points to have in mind.
    CIS is a connected ISO stream. An audio stream is unidirectional stream which means there can be up to 2 audio streams in a single CIS. Each of the 2 audio streams could go different way as CIS can be bidirectional. It is possible to have multiple audio channels in a single audio stream. In other words, it is possible to have stereo in a single audio stream. Furthermore, it is possible to have bidirectional stereo in a single CIS.
    BAP is significantly more flexible than the audio application, which could restrict some options/flexibility. There are no specific recommendations on using one audio channel per audio stream vs using multiple audio channels in a single audio stream. With direct use of BAP or CAP API, you should be able to do anything that is allowed by the BAP specification, being limited only by the radio time.

    Best regards,
    Dejan

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