I am trying to get the four channels available from puredata into the Jack audio server. I have selected 4 channels in the audio output settings.

For some reason, Jack only appears with 2. Anyone know why this is the case and how I might go about getting the other two channels appear? I am trying to achieve this so I can send audio from puredata to different speakers in a bluetooth syste (two seperate bluetooth modules, with a stereo channels).

The same thing happens with pipewire- only two channels are available in the virtual audio stream. Ive also attached photos for both of these audio servers. Help would be greatly appreciated.

The channels DO appear in pulseaudio however, and I have included pictures of this

Thanks for your help. Below photos demonstrating some of the settings. I am running linux mint

pd media settings

the four channels setup to go to ALSA: jack

there are only two channels appearing in Jack from puredata, not four

however, the channels do appear in pulseaudio volume control

but also does not appear in pipewire

@bobfred I see you still have portaudio selected rather than alsa or jack, before you opened audio settings... maybe that has an effect?
Could it be that only 2 channels are made available from Pd because "system" only has 2 output channels?
Is there a way to aggregate your 2 Bluetooth devices as a 4-chan device in a similar way to creating an aggregate device on a Mac or using Asio4All in windows.
I think that for a 4-chan stream to be accepted as an input you will need a 4-chan device as output because it will in fact be a single (probably interleaved) stream so that timing is preserved between the channels.
For that you might be able to specify the system output by changing ~/.asoundrc like this...... https://stackoverflow.com/questions/15592187/5-1-channels-with-portaudio
....but that is a wild guess and I think you should google "Linux aggregate device".
It seems that Jack has an "aggregate device editor" and pipewire probably has something similar....
David.

It works out of the box on Debian sid but with jack checked not portaudio:

$ jackd --version
jackdmp version 1.9.22 tmpdir /dev/shm protocol 9
$ pactl --version
pactl 17.0
Compiled with libpulse 17.0.0
Linked with libpulse 17.0.0
$ pd -version
Pd-0.55.2 ("") compiled for Debian (0.55.2+ds-1) on 2024/11/17 at 16:07:58 UTC

I think this idea about the "system" only have 2 output channels is a good intuitive guess, only because it resonates with something I was supposing. Still not sure why or how thats the case it would impact it, nor how to change it.

However, ass FFWs post below displays, they are successful getting it to work on Debian.

@FFW said:

It works out of the box on Debian sid but with jack checked not portaudio

I was able to achieve this also, but the issue with jack is that it is not displaying bluetooth output devices.
Jack cannot support Bluetooth and it seems bluetooth headphone support is handled exclusively by PulseAudio (not even ALSA). How can I view a bluetooth output in jack so I can send these outputs independently to seperate devices?

thanks for confirming that jack supports the multiple inputs. I must have missed something... any idea why it wont work with pipewire? I am happy to use jack so long as I can get access to the bluetooth output.

@bobfred said:

How can I view a bluetooth output in jack so I can send these outputs independently to seperate devices?

JACK cannot do this. Period. JACK's timing requirements are far too strict for BT. Period.

(For sake of completeness: Some years ago, I tried to hack it using bluez-alsa and I did actually get JACK piping into Bluetooth earpieces for a short time, with a ridiculous buffer size of 8192 samples x 2 periods, like a quarter-second latency But then JACK would always hang within 15 minutes, and it was impossible to restart the JACK server without rebooting the whole system. So I found that this was not an especially joyful way to work and I gave it up.)

Pipewire might be able to do this.

hjh

@ddw_music I'm guessing this had SuperCollider in the mix so you had to use jack? With pd you could do it all with alsa, latency will still be poor but that is not always an issue, but this could end up meaning lots of alsa loopback device fun depending on requirements.

@oid said:

@ddw_music I'm guessing this had SuperCollider in the mix so you had to use jack?

Yes.

With pd you could do it all with alsa...

Sure. The question was, how to get the Bluetooth headphones to show up in JACK, and the answer was about why that isn't a good idea.

FWIW I'm planning to upgrade Ubuntu Studio over the weekend, after which I would be fully on Pipewire. I will try Bluetooth with that. I don't have high expectations, but let's see.

hjh

@ddw_music Yeah, I was just mentioning it because it may be a solution for @bobfred since pipewire can also speak alsa or at least expose alsa ports without shutting down, not sure if he is doing anything which actually requires jack. I have no experience with bluetooth beyond the idiot proof connection of my phone to my stereo, figured you would be able to answer if using alsa was actually viable so I tagged you, did not want to send bobfred down a rabbit hole out of my own ignorance.

@oid I had a similar opinion and similar worries.
Bluetooth pairing with a pairing password in Android sometimes ties the device to a single app, the data stream..... and even the connection state.... then not being available to any other.
No idea how that is dealt with in Linux..... so no comment except that the information will have to be found in Linux forums I think.
David.

@ddw_music said:

FWIW I'm planning to upgrade Ubuntu Studio over the weekend, after which I would be fully on Pipewire. I will try Bluetooth with that. I don't have high expectations, but let's see.

Finally did that upgrade (Ubuntu Studio 24.04): Pipewire could automatically switch between built-in audio, USB soundcard, and Bluetooth earpieces, and SC server (JACK app) could route audio to the Bluetooth earpieces without an apparent glitch (though I didn't try to push the CPU, so I don't know where the limit is).

So I'd say, if @bobfred needs JACK-ish behavior with a BT headset, Pipewire is very likely to be a good way to go.

hjh