[LAU] Multiple asynchronous JACK chains resampled?

[Jonathan Brickman]

>     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?

-- 
Jonathan E. Brickman   jeb at ponderworthy.com   (785)233-9977
Hear us at http://ponderworthy.com -- CDs and MP3 now available! 
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