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

[Paul Davis]

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 <https://github.com/ponderworthy/MultiJACK>, 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
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