[chuck-dev] Anti-aliased oscillators

pibsid at suomi24.fi pibsid at suomi24.fi
Sun Jan 13 04:49:39 EST 2008

I recently posted anti-aliased versions of the basic oscillators in the 
chuck forums. They're based on integrating the oscillator's function 
over phase changes to get the average value over one sample. 
Here's an example of an anti-aliased saw wave taking the current phase 
and the difference to the next phase as arguments:

fun float fun_aa_saw(float t,float delta_t) { 
    t-Math.floor(t+0.5) => float t1;
    t+delta_t-Math.floor(t+delta_t+0.5) => float t2;
    return (t2*t2-t1*t1)/Std.fabs(delta_t);

They're quite heavy on the CPU because they need to ticked every 
sample in ChucK so it would be nice to imlement them on the source 
We do have the Blit versions of the oscillators but they only 
reproduce the sound of the osc they're band-limiting. Average-anti-
alias keep the waveform more intact while still considerably reducing 
frequency leaking.

How do I design oscillators on the source level of ChucK?

 Pyry Pakkanen

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