Multiple BLE Audio Source Devices Outputting to a BLE Audio Sink Device

[John]

Hello,

I am exploring different Bluetooth LE audio options and I have a question about capabilities.

• Is it possible to connect to multiple Bluetooth LE audio source devices (microphones) to 1 central device?
• Can the central output all of the audio source streams to a singular Bluetooth LE audio sink device?

I don't know if syncing all of the devices will be an issue.

[ovrebekk]

Hi

Unfortunately it is still a bit early days for LE Audio. The full profile specification is not yet released by the Bluetooth SIG, and as such we don't have support for it in our Bluetooth stacks or examples.

Is it possible to connect to multiple Bluetooth LE audio source devices (microphones) to 1 central device?

Theoretically this is possible, but it is not a primary use case for LE Audio.
The problem of this use case is that the different audio sources will not be synchronized, so you might have timing conflicts between them on the central device leading to packet loss. 

Can the central output all of the audio source streams to a singular Bluetooth LE audio sink device?

This is possible, yes. 

Please note that I am just talking about what the specification allows, since we don't yet have an implementation.

Best regards
Torbjørn

[chethan26]

Hi,

I am also looking for same concept, is there any possibility to do with NRF53?

Best Regards,

Chethan kumar

[ovrebekk]

Hi Chethan

I don't think there is an easy way to do this unfortunately, but I will ask the audio team for some input. 

We are planning to add support for bidirectional audio on one headset in a future update, but there are no current plans for adding bidirectional audio to two headsets at the same time. 

Best regards
Torbjørn

[Alan Low]

ovrebekk said:

the Bluetooth stack we use should support up to 4 concurrent connections. 

Hi Ovrebekk,

So can I say that "5 sources to 1 sink device" is not possible with current Nordic BLE stack?

[ovrebekk]

Hi Alan

Alan Low said:

So can I say that "5 sources to 1 sink device" is not possible with current Nordic BLE stack?

Correct, this can not be done. 

Also it is important to keep in mind that in addition to needing support in the Bluetooth stack for the right number of connections the CPU would need to have the sufficient performance to decode or encode all the LC3 streams. 

Best regards
Torbjørn

[Alan Low]

Hi Torbjørn,

Thanks for your clarification.

How about 4 sources to 1 sink device? If 4 to 1 is possible, does Nordic have any of such sample code to provide us for reference?

[ovrebekk]

Hi Alan

No, the LE Audio sample is limited to two audio channels, and the gateway will be the source, not the sink. 

One of the developers made an unofficial modification of the example, available here, which adds a single audio return channel, but it is far away from 4 to 1. 

I will check with the team if they have any relevant news to share, but for the time being I don't think we can cover this use case in our examples. 

Best regards
Torbjørn 

[ovrebekk]

Hi again

The team confirmed that we don't have any demos for this unfortunately. 

Best regards
Torbjørn

[Alan Low]

Hi Torbjørn,

Thanks for the clarification!

[Eggz]

Hello Torbjørn, regarding the "unofficial" modification: could you explain how this is set up? Are both sources in Le audio broadcast mode? How are the timeslots aligned with 2 sources/microphones active simultaneously?  Thanks 

[ovrebekk]

Hi Egil

This demo is using CIS channels, not BIS. 

Technically the demo is receiving MIC data from both headsets, but decoding and processing two incoming data streams is not currently supported so only the MIC stream from the left headset will actually be processed. 
For this reason there is no synchronization between the two incoming data streams. 

Best regards
Torbjørn

[Eggz]

Ok, thanks! I appreciate it!