Subject: Re: [linux-audio-dev] more fundamental questions
From: eli+@gs211.sp.cs.cmu.edu
Date: Thu May 24 2001 - 00:24:55 EEST
Jay Ts wrote:
> I did a little more thinking on this and realized that MIDI is essentially
> a control signal, and maybe it would make sense, in a general way, to
> include control signals in the design in addition to audio, and then
> make MIDI (or some cooked version of it) a class of control signal.
Control signals are almost a must for synthesis. Two thirds and up of
your signals in a patch can be control, so running those at
control-rate gives you a factor of three in speed. Whether they're
passed between applications quite as much as that, which is what LAAGA
cares about, I don't know.
I'm not sure I want to think of MIDI as a control signal, actually. I
like a three-way distinction: audio, control, and events. Control is
synchronous with audio but at a lower sample rate, whereas events are
asynchronous. Control can and often should be interpolated; events in
general can't.
Introducing rates other than audio makes your life way more
complicated, though. Before there was just one "multiply". Now
there's audio times audio, audio times control, and control times
control, and that's without bringing in events or even "audio times
interpolated control", which you really need.
What Aura does is have you define unit generators in a specialized
mini-language, including fragments of C++. From this a multi-thousand-
line awk script (!) generates all of the necessary varieties, which
the UI then ought to hide from the user.
--
Eli Brandt | eli+@cs.cmu.edu | http://www.cs.cmu.edu/~eli/
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