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

[Len Ovens]

On Wed, 16 Aug 2017, Winfried Ritsch wrote:

> Here my  state of research:
>
> Since BLuez >= 5.0 dropped ALSA [1] I tried using pulseaudio (can route it
> trough jackd). I connected a BK8000L module (sure hifi) via bt-manager and
> pulseaudio works fine. I try to connect a second, the first one gets
> disconnected so only one is audio device seems to be  possible at the same
> time.

That would be either a limitation of pulse, the BT module or the bt 
dongle. Have you tried two BT dongles? (does tyhe kernel allow that?)

> As a second solution I tried the alsa implementation: bluez-alsa  [2], but
> I didn't succeed to use it via jackd (didnt try hard) and it has the same
> behaviour with aplay on an first try on command line.

Because of possible issues as mentioned above, have you tried this with 
pulse with no blue tooth module? That is does pulse lock the BT audio in 
the same way it does for a ALSA device?

> Purpose: simple distributed audio-system adding BT speaker for sound
> installations, the first try two BT-Speaker used each mono, forming a stereo
> pair.

What little I know about BT (that it is wireless :) would suggest that it 
would not be possible to use two bt links for a stereo pair without 
artifacts. BT audio is a stream and I would guess compressed and resampled 
for best quality. A stereo stream for a set of speakers would be a must. 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 :)

However, the big question with BT for any venue is it's relatively short 
range and interference with many people using BT headsets for their phone. 
(even someone driving past with a hands free setup). As much as we all 
hate wifi for pro audio use (for it's unreliablility) I would expect it to 
be better than BT (focused ir may be even better). It would then be 
possible to go pulse to pulse (I do not know how flexable pulse is over 
net) or jack to jack (very flexable with zita-njbridge) or even simpler an 
opus streamer of some sort. Also check out wireless personal monitoring 
systems.

One thing for sure is added latency. If overall latency is not a problem 
(streaming prerecorded material only) then icecast or similar may be the 
best option (.5 sec latency or so).

I understand the BT speakers are already available and putting together a 
powered speaker with a r-pi or similar with wifi while relatively cheap, 
does require work and assembly. I do not know if there is any such thing 
as a BT booster available though. (and BT needs bi-directional traffic)

I am not sure, but I do not think BT has a "promiscuous mode" (or 
broadcast) allowing several receivers to use one stream.

Anyway, just some thoughts off the top of my head.


--
Len Ovens
www.ovenwerks.net