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

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

Winfried Ritsch
Hello,

I just did some research but couldn't find any satisfying answer and I am not
an BT specialist. So before digging deeper in the BT-world I want  ask here if
anybody already has an solution and if it could work theoretically ?

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.

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.

Any ideas are appreciated.

mfg
 winfried

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

[1] https://git.kernel.org/pub/scm/bluetooth/bluez.git/commit/?
id=4ff9b99292eca193dc0c149722328cb0b1ab0818

[2] https://github.com/Arkq/bluez-alsa

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Re: 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

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Re: How to play multiple bluetooth (BT 4.0) audio receiver ?

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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Re: How to play multiple bluetooth (BT 4.0) audio receiver ?

Winfried Ritsch
Hello,

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.

Am Mittwoch, 16. August 2017, 22:12:09 CEST schrieb 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.
>
...  it is not about audio quality, nor mono or stereo or delays very much ...  
its about using  e.g. (here) BK8000 modules  for EUR 5,70 for DIY  speaker
which  can receive Audio (stereo) and control some GPIOs,  (also they have
quite good audio quality) ... also its not about stereo or mono, the stereo
was my first attempt, I want autonomous solar powered speaker of any kind as an
loudspeaker orchestra or acousmatic, like french artists name this...  outside
in nature. ...

mfg
 winfried


> Regards,
> Ralf
> _______________________________________________
> Linux-audio-user mailing list
> [hidden email]
> https://lists.linuxaudio.org/listinfo/linux-audio-user


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Re: How to play multiple bluetooth (BT 4.0) audio receiver ?

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?
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Re: How to play multiple bluetooth (BT 4.0) audio receiver ?

Winfried Ritsch
In reply to this post by Ralf Mardorf
Hello,

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
DIYverse.

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
available.

mfg
 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
> _______________________________________________
> Linux-audio-user mailing list
> [hidden email]
> https://lists.linuxaudio.org/listinfo/linux-audio-user


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- [hidden email] - 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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