Re: [linux-audio-dev] matrix model vs. memory

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Subject: Re: [linux-audio-dev] matrix model vs. memory
From: Tom Pincince (stillone_AT_snowcrest.net)
Date: Sun May 20 2001 - 21:58:07 EEST


> > >> both of these seem suboptimal to me. as i said, there is already an
> > >> implicit matrix of port connections; exposing it and attaching a gain
> > >> at each node of the matrix seems like a really cool idea to me.
> > >
> > >As an *option*, otherwise you limit efficiency also when this is not
> > >needed. This would be a symptom of a bad design.
> >
> > In your own recent message, you mentioned the need for two helper
> > functions to transfer data from port to port sometimes. Either they
> > includes the concept of gain, or they don't. True?
>
>
> Yes, but I don't have excluded the possibility to have buffer sharing.
> Of course this is feasible only for a subclass of static gain matrix.

It may be useful to consider the percentage of connections that are
static gain. If this number is very small then the efficiency loss is
worth the simplicity of having only one kind of connection. In
situations where the user is using just a simple app, such as for
playback, the efficiency may go down by a large percentage, but the
total demand on the system is so low in this case that preserving
efficiency is not an issue. So if we look at a complex studio setup,
and classify each connection as static or variable gain, the answer will
reveal itself. Most connections have variable gain so the static case
will be small. The approach that comes to mind is to begin listing
every static connection that we can think of and see if they add up to
an amount that is worth addressing as a special case. Here is my
(probably incomplete) list.
1) Every connection from an audio interface input. (see A below)
2) Every connection to an audio interface output. (see B below)
3) Every connection to a recorder.
4) Every connection from a mixer channel strip that uses the strip's
fader or pan output gain level as its own, such as direct out, main bus,
sub busses, solo. For clarity, an example of a connection from a
channel strip's fader output that requires its own gain coefficient is
an aux send to a multi-in multi-out fx processor.

A) This is true for certain approaches to UI design that allow audio
interface inputs to be routed only to a mixer channel strip or a
recorder.

B) This is true only if each audio interface output receives its signal
exclusively from its master fader. This master fader would be a plugin
that would sum all relevant plugin outputs and have gain as its only
process.

Tom


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