Subject: [linux-audio-dev] Blockless processing
From: Steve Harris (S.W.Harris_AT_ecs.soton.ac.uk)
Date: Fri Dec 13 2002 - 00:22:11 EET
I couldn't resist it so I hacked up a quick script to try the blockless,
dynamicly compiled processing we were discussing the other day.
http://plugin.org.uk/blockless/
just "make" if you want to test it
Its really hacky insomnia perl code, so dont look at it ;)
It works by defining graphs (.g), that are made up of atoms (C code) and
other graphs. The perl script turns it all into one giant lump of C and
builds it.
Graph files look like eg (pinknoise.g):
noise n(); // declares an instance n
zm1 d();
mix2to1 m();
gain half(0.5f);
n:out -> m:in1; // connect the 'out' port of n to the 'in' port of m
n:out -> d:in;
d:out -> m:in2;
m:out -> half:in;
half:out -> this:out; // an output from this module to the parent graph
I went as far as defining a biquad filter in the graph format
(http://plugin.org.uk/blockless/blockless/modules/biquad.g), but it
dosen't quite work because the execution order is more or less random.
I used the biquad in a simple toplevel graph
(http://plugin.org.uk/blockless/blockless/graphs/test4.g), it takes about
50 cycles per sample on PIII (interestingly its compiles to slightly worse
code in gcc3.2), the source my script produces is very tangled and
funtion-y, but gcc manages to untagle it and inline it all, eg.
http://plugin.org.uk/blockless/blockless/intem/test4.c
Its too much work to create a reasonably complex synth or anything in this
as theres no UI and keeping all the links straight in your head is
painful, so I dont know how well it scales up.
Its quite cool building up modules from gain and z^-1 units though :)
- Steve
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