5

I'd like to use a Raspberry Pi to transmit (send) audio from the headphone jack (using it as an input) to multiple Bluetooth devices at once.

The purpose (I have a tutorial for receiving already) is to have multiple Raspberry Pi that receive the Bluetooth and output to the 3.5 mm jack, so multiple people can watch a movie in a room using headphones without there being any sound heard from people without headphones.

Is this possible?

2

Bluetooth uses what are called piconets. Each piconet is made up of at least one master and as many slaves as the bands will allow. No bluetooth device can be the master of more than one piconet but a bluetooth can be the slave of many.

This means that what you are looking for can only be done where each headset is the Master of its own piconet and the device delivering audio is the slave of them all. I've never tried it but I dont think the built in bluetooth for the RPi3 will handle this correctly, unless someone has come out with an epic package for that.

The only thing i can think of that would work is a splitter, something designed specifically to act as the slave of multiple BT devices. Like this one from Walmart or these ones from Amazon. Take care: a lot of them however, only work for two piconets, meaning two headsets. I don't know of any that do more, but id love to see one.

The problem comes from managing the frequency hopping that must be done to maintain paired connection. The more connections the more managements it takes to make sure the chirps don't overlap. And the master is the device that decides what clock to synchronize and what frequency schedule to maintain, further complicating things.

Haven't looked at these in a while, so shop around, maybe the tech got better and there are some out there that will do more than 2? But AFAIK its not as easy as it sounds like it should be.

EDIT:

On a side note, something I used to do a while back was get over the ear radio headphones that could pick up AM/FM frequencies. Then I set up a short range radio transmitter and used this to supply as many headphones as i desired for an outdoor movie night against a brick wall. It was a blast and worked like a charm. Bluetooth is awesome and if you want to stick with it that's fine, but it wasn't designed for this.

Just throwing it out there that technologies do exist that were designed exactly for this (think car radio). Many users, one source.

3
  • Radio is great idea. Do you know of anything like that ear radio headphones that just outputs aux to headphone jack rather than being all-in-one so users can use their own headphones? I've looked and couldn't find anything. – Robert Perry Jun 11 '17 at 1:49
  • well, if im understanding you correctly, any consumer radio device should work. most have a headphone jack. they just bring one of those too, then they can use whatever they want, either directly or via Bluetooth. So long as it connects to their radio, that is. – Nalaurien Jun 11 '17 at 1:51
  • I would have to agree, this may be possible with a Bluetooth dongle but it’s all predicated on the fact of being able to connect multiple Bluetooth devices to one rpi(not sure that is doable, haven’t tried), you would then need the remaining pis setup as a2dp sinks. Then create a pulseaudio combined sink to output to them all. Again agreeing with the answer from @Nalaurien, I’m not sure that this would get handled well. Then comes the latency issue. Fm transmission is definitely a stronger answer. You can make one for under $10 or get a car one if all receivers are in a closer proximity. – Brett Reinhard Dec 10 '17 at 1:46

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.