[LAD] PipeWire, and "a more generic seeking and timing framework"

[Jonathan E. Brickman]

Many thanks, Paul, for this and much more.  My lame excuse is I have
had a chunk of my head buried in a singular problem for a long time and
those librarians are very tired :-)
Given reality-check, then, maybe the institution of multiple JACK
subgraphs, with time-decoupling by Pulse-style transport, is a way to
get everything done!
J.E.B.
On Mon, 2018-02-19 at 18:04 -0500, Paul Davis wrote:
> JACK is already much closer to the hardware than the networking
> stack.
> 
> At the conclusion of the jack process callback, it writes samples
> *directly into the memory mapped buffer being used by the audio
> hardware*. The process callback is  preemptively (and with realtime
> scheduling) triggered directly from the interrupt handler of the
> audio interface.
> 
> JACK does not use a round-robin approach to its clients. It creates a
> data (flow) graph based on their interconnections and executes them
> (serially or in parallel) in the order dictated by the graph. 
> 
> 
> 
> On Mon, Feb 19, 2018 at 5:57 PM, Jonathan Brickman <jeb at ponderworthy.
> com> wrote:
> > Not really sure the subgraph is so good -- one of the things JACK
> > gives us is the extremely solid knowledge of what it just did, is
> > doing now, and will do next period.  If I run Pulse with JACK, it's
> > JACK controlling the hardware and Pulse feeding into it, not the
> > other way around, because Pulse is not tightly synchronized,
> > whereas JACK is.  But if you can make it work as well, more power
> > to you.
> > 
> > Concerning seeking and timing, though, I have had to wonder.  My
> > impression of JACK for a long time (and more learned ladies and
> > gentlemen, please correct) is that it uses a basically round-robin
> > approach to its clients, with variation.  I have had to wonder,
> > especially given my need for this, how practical a model might be
> > possible, using preemptive multitasking or even Ethernet-style
> > collision avoidance through entropic data, at current CPU speeds. 
> > It's chopped into frames, right?  Couldn't audio and MIDI data be
> > mapped into networking frames and then thrown around using the
> > kernel networking stack?  The timestamps are there...the
> > connectivity is there...have to do interesting translations... :-)  
> > Could be done at the IP level or even lower I would think.  The
> > lower you go, the more power you get, because you're closer to the
> > kernel at every step.
> > 
> > 
-- 
Jonathan E. Brickman   jeb at ponderworthy.com   (785)233-9977
Hear us at http://ponderworthy.comcom -- CDs and MP3 now available!
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