Bluetooth audio mesh product recommendation

[k1zmt]

Hi guys,

I have an interesting idea - organize a network for realtime audio communication. Basically duplex Walkie-Talkie but using bluetooth headsets. I tried to use ESP32 audio gateway and it didn't work with Apple AirPods. This leads me to you.

I am looking for a product that:

1. Can connect to Apple AirPods like a host (like an iPhone)
2. Can transfer audio in real time from the headphones mic and back to the headphones speakers. Apple does it with excellent quality on Facetime calls.
3. Doesn't disrupt existing connection with iPhone
4. Pairing with a single button

There are few optional ideas:

• Ability to bidirectionally stream from multiple devices in realtime like it is conference call.
• Presence of analog input/output channels to stream audio back and forth to headphones

[Karl Ylvisaker]

Hello,

I do not have a lot of personal experience with Apple Airpods unfortunately, but I would suspect that they might use a proprietary radio protocol when communicating between an iPhone and Airpods specifically, and then use Bluetooth Classic for communicating with non-iPhone devices. Do you know anything about this?

None of our products support the Bluetooth Classic protocol (which is what is used for Bluetooth audio playback in most headsets today), since we focus on Bluetooth Low Energy (Bluetooth 4.0 and up). Fortunately, the LE Audio addition to the Bluetooth Low Energy protocol just released, which opens the door to a lot of new use-cases.
If you are not already familiar with the LE Audio specification, and the changes and improvements that it brings with it, you could take a look at this blogpost which summarizes it. In essence, LE Audio is the new standard for wireless audio playback.

You mention that you would like multiple devices in this network - how many devices do you have in mind?
The new LE Audio standard comes with the Auracast (previously known as 'audio sharing') feature, that could potentially be utilized for your application, depending on how many devices you intend to have in the network, and how many devices that may be transmitting concurrently.

Best regards,
Karl

[k1zmt]

Apple Airpods support Bluetooth classic. I was able to pair them to ESP32 Audio Gateway example using headset profile.

And thank you for Audio BLE info!

Karl Ylvisaker said:

how many devices do you have in mind?

So the idea is use this application for cyclists. Last time we rode there was about 16 members. We have started with larger crowd but that split at certain point. There was a Boston Midnight Marathon ride and there we had a lot of people. I wasn't able to count them but around 500. Certain rides could be fairly big. In such big rides simultaneous communication is not required. What is required is broadcast and help channel for questions/requests.

Honestly, the mesh part doesn't seem that critical. I have been thinking a lot and it seems feasible to use some of CB/FRS/GMRS frequencies to broadcast and receive analog audio. Using something like dual side band could be easy to implement and people can hear each other simultaneously. Using FM for that purpose will result in distortion and AM is simply inefficient. So I look for options that can used for hours on battery operated devices. I have been in rides as long as 10 hours. The distance between members could be different but it is usually under 1 km which is not a lot. The main problem is hilly landscape or trees. It is easy to loose someone out of site and this is exactly why we need the radio.

One of the biggest challenges for cycling is that you don't have options to use PTT button and hence you are either always online or use voice activated transmission which is hard because there is a wind blowing into the mic all the time.

I have been thinking to build a simplest proof of concept Bluethooth gateway that will work all the time and start tackling on optimizing power consumption and full duplex support.

[Karl Ylvisaker]

Hello,

k1zmt said:

thank you for Audio BLE info!

No problem at all - it really is the future of wireless audio playback, which is why you would want to at least consider it for any new wireless audio product! :) 

k1zmt said:

Apple Airpods support Bluetooth classic. I was able to pair them to ESP32 Audio Gateway example using headset profile.

Yes, they definitively support Bluetooth Classic - but I do not know if they do anything proprietary (or if they strictly use Bluetooth) when they are connected to an iPhone, as opposed to a third-party device.


Thank you for detailing the use-case more. In general, it would not be feasible to receive from such a large number of devices simultaneously, and to mix it together into a single stream for the rider to listen to - this would require a lot more computational power than what is available in most microcontrollers today.
However, you could potentially work around this issue by implementing a smart switching between which streams to listen for.
In the case with so many riders you might instead have to use a Broadcast, and then selectively decide which broadcast to receive. So for instance, the leader of the group could be the default, and then the other members could signify that they have something to say, which makes the others tune into them.
The simplest way to do this would perhaps be to just have the one broadcast available all the time, but then keep scanning for other broadcasts in the background as well, so that if another broadcast from the group is found, it tunes into this one instead, for instance.

What will the maximum distance be between two riders in the same group?

k1zmt said:

One of the biggest challenges for cycling is that you don't have options to use PTT button and hence you are either always online or use voice activated transmission which is hard because there is a wind blowing into the mic all the time.

You could perhaps use tiny Machine Learning's keyword spotting for this, but I dont know of anyone that has combined these two projects before.

k1zmt said:

I have been thinking to build a simplest proof of concept Bluethooth gateway that will work all the time and start tackling on optimizing power consumption and full duplex support.

That sounds like a good way to start! :) 
If you get some nRF5340 Audio DKs (at least 3 - one to be the BIS gateway and two to be BIS headsets) you could quickly have the broadcast set up with our reference application - then you can move on to adding the gateway capability to the headsets, and to have the other gateways tune into this gateway when it starts broadcasting.

Best regards,
Karl