[LAU] How to play multiple bluetooth (BT 4.0) audio receiver ?

Winfried Ritsch ritsch at iem.at
Sun Aug 27 11:14:57 UTC 2017


To answer myself for archive, since I got some spare time to experiment:

summary : 

>From specification of Bluetooth 4.0, only one audio connection (known as 
profile) can be achieved from one sender, so there might be BT-adapter or cards 
which can handle more, but the Bluez implementation does not implement this, 
rumours are there OS-X bluetooth stack did. 
The solution on Linux is to add one BT-Adapter for each speaker to be 
addressed, (adding some EUR 5.- to the EUR 5.70 of the receiver board), but 
additional tests have to be done.

Anyhow maybe wait until devices with BT 5.0 broadcast will appear on the 

Addendum to Ralf questions:

For my application: inspired by Acousmatics (Akusmonium)  speakers have to 
sound different, so classical situation is playing one radiophone source (Mono 
or stereo) to multiple speakers and controlling them live or automated. 
Therefore a special mixer (done with Pd) has 2 Ins and multichannel out, where 
each out channel has EQ, Delay, etc... to be controlled and adapted (I do it 
mostly by hearing). A measurement tool can propose the delays of each out 
channel, combining streaming via ethernet, wifi, bluetooth and soundcard, 
everything within 30ms (equal ~10m distance of speaker) is fine, if roughly 
constant...,  (I know stereo means to respect interaural time differences 0.5 
ms but thats moving the head 15cm)
Anyhow BT is really not the first choice and try to avoid, but an addition if 

 winfried ritsch

Thursday Winfried Ritsch
> Thanks for the answers.
> The question was about using bluetooth audio and linux experiences.
> The main question was, how can I play multiple BT receiver from a linux
> machine. Anybody done this ?
> On my further research BT-audio is not multicast per se and so I asume the
> sender have to manage many connection in parallel, MacOS-X user reported
> sucess, so I thought linux can do also but it didnt find a solution until
> now, ... maybe many dongles.

Thursday Ralf Mardorf:
> You want to send digital audio signals to at least two receivers. The
> two audio signals belong to the same sound source e.g. left and right
> channel or just one channel, but still send to 2 receivers. Assumed you
> should solve the issue of your request, then how would you sync the
> audio signal of the two receivers?

Wednesday  Ralf Mardorf:
> On Wed, 16 Aug 2017 12:32:55 -0700 (PDT), Len Ovens wrote:
> >I think if it was me and I had to use separate lines for left and
> >right, I would choose mono and add speakers as needed to cover the
> >area. (stereo in a live crowd situation is over rated anyway :)
> Hi,
> it doesn't matter if "stereo in a live crowd situation" should or
> shouldn't be over rated. I agree that mono usually should be good
> enough, but OTOH you still need to care about time differences when
> using more than one mono speaker, if you e.g. care about good audio
> quality for music or an easy to understand talker. A "sound
> installation" might be based on strong stereo usage, but not
> necessarily require good sync for the 2 channels. IOW mono might render
> it useless, if it should be important that the duck is quacking 10
> seconds from the right side only and after that 10 seconds from the
> left side only ;), so sync would be completely irrelevant.
> Regards,
> Ralf
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- ao.Univ.Prof. DI Winfried Ritsch 
- ritsch at iem.at - http://iem.at/ritsch
- Institut of Elektronic Music and Acoustics
- University of Music and Dramatic Art Graz
- Tel. ++43-316-389-3510 (3170) Fax ++43-316-389-3171 

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