What I want to do, is to use the resources I have to run multiple signal generation and processing chains asynchronously, in parallel, and then use the final audio-hardware-synchronized chain to resample them all into one, perhaps using the Zita tools.  Anyone know if this is possible?  I saw this flow structure work very well in the video domain, quite a few years ago.

That's not what you want to do at all.

JACK is designed to be a *synchronous* system. All clients process audio corresponding to the same period of time, precisely in sync with each other. You do not want to "resample them all into one", and certainly not with the zita tools.

A "correct" digital audio processing and/or synthesis environment consists of a single audio interface (or at least, a single digital sample ("word") clock). You can run any number of JACK clients, connected in arbitrary ways. But using multiple audio interfaces (which is what the zita tools are related to) is not  the right thing to do unless you are forced to by lack of funds or inappropriate hardware.
 


I do understand that JACK is designed to be completely synchronous.  But a good pipelined architecture, can take multiple synchronous processing chains running independently (asynchronously to each other), and then merge them at the output end.  What I want to do is the equivalent using JACK at the synchronous level, so that I take advantage of more of my computing power.  Eventually I will want to do exactly the same using four or five RPi-compatibles, with just one of them having the audio output; but right now I have about 75% of my CPU and 6+ gigabytes of RAM not being touched, so clearly the testbed is waiting :-).  The video processing pipeline I saw a while ago used a proprietary bus (it was a while ago), I am thinking IP is probably the simplest now, over localhost within this box, and through a good switch whenever I start work on RPis (which is probably not soon but is worth contemplating).

And to use the Zita tools, I was going to see if there was an audio-over-IP transport which delivered ALSA ports :-)  I don't quite remember, it has been about eight months since I looked.  If there is, I would expect the existing Zita tools would do wonderfully for the resampling connectors.  If not, I wonder what best to use for JACK-to-JACK resampling?

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Jonathan E. Brickman   jeb@ponderworthy.com   (785)233-9977
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