Author Topic: Low Latency Wireless Audio - Need advice  (Read 1438 times)

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Offline neo__04

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Low Latency Wireless Audio - Need advice
« on: March 17, 2017, 01:58:17 am »
Hi all,

Working on a little wireless audio project.

Its wireless audio for a metal detector. So i need as minimal latency audio as possible.

There are commercial products available that utilize 2.4ghz audio, not bluetooth, but 2.4ghz somehow.

I've been playing with FM radios, but having a bit of trouble amplifying the signal due to noise etc.

Can anyone suggest a better option?

Open to suggestions as I'm struggling for ideas.


 

Offline evb149

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Re: Low Latency Wireless Audio - Need advice
« Reply #1 on: March 17, 2017, 03:01:00 am »
Bluetooth and Bluetooth  low energy are just  protocols that run on top of particular radio modems.
The modems in the IC send and receive bits / bytes / packets at a certain rate and the protocol handles that data in certain ways.

There are Bluetooth modules that support headset profile and hands free profile that are intended to be able to send audio to a bluetooth headset / earpiece and hands free speaker phone arrangement used in cell phones. 
Obviously you can buy off the shelf bluetooth speakers / headsets / earpieces.
So a simple solution would be to use a bluetooth module that supports the encoding end of the chosen one of those profiles and then use an off the shelf bluetooth device as the receiver / speaker.  The latency will not be minimal due to the protocol overhead but it should be within several milliseconds or less which seems likely acceptable.

2.4GHz radio modems that are not Bluetootth are available and have lower latency (maybe) because of not having the encoding and protocol overhead of Bluetooth audio profiles and protocols.

There are also just 2.4GHz (or other frequency) analog transmitters that send analog signals and are not modems.  Sometimes some old baby monitors or something might use this sort of thing, though more commonly new devices use digital modems and digital audio of some kind.

Anyway another possibility if you want to build it would be to use a EM coupling that is not a RF transmitter but is basically just a transformer (air core) that couples a transmitter coil to a receiver coil with a signal that is modulated in the high kHz or low MHz range.  There are "telecoil" and "induction loop" devices that work like that to send audio to special headsets that can receive the signal over a short distance.  Hearing aids use a baseband magnetic field coupling to receive audio from phone earpieces.  And the former kind of telecoil devices would be used for instance in museums where they broadcast some audio information about the exhibit you are standing near to headsets you can wear that pick up the signal over a distance of a few feet.  The receivers can work basically like a crystal radio, though you can use a battery and amplifier if you want louder audio with lower quality headphones.
https://en.wikipedia.org/wiki/Audio_induction_loop

You could also just audio modulate an IR LED and then receive the audio with an IR receiver that converts the IR signal modulation to headphone driving audio.  It doesn't get much lower latency than that and as long as you have a line of sight from the transmitter to the receiver it would work fine.

   
 


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