[linux-audio-dev] Re: detune

[mlang]

"Bill Schottstaedt" <bil at ccrma.Stanford.EDU> writes:

> Another method, related to the vocoder but more "real-time" oriented
> (i.e. sample-by-sample, not fft block processed) uses a bank of Hilbert
> transforms (for the pitch shift) and a bank of bandpass filters (each
> harmonic shifted individually to maintain harmonic relations) --
> see ssb-bank et al in dsp.scm in the Snd tarball (ssb refers to the
> single sideband suppressed carrier amplitude modulation generator).
> sndscm.html has examples.

And here is a minimalistic class for SuperCollider to
do this (sort of).

FreqShift : UGen {
	*ar { arg input, shift, mul=1.0, add=0.0;
		var sin1, sin2, cos1, cos2, constFreq, filtFreq;
		constFreq = SampleRate.ir * 0.25;
		filtFreq = constFreq * 0.75;
		cos1 = FSinOsc.ar(constFreq, 0);
		sin1 = FSinOsc.ar(constFreq, pi/2);
		cos2 = SinOsc.ar(constFreq + shift, 0);
		sin2 = SinOsc.ar(constFreq + shift, pi/2);
		^(LPF.ar(LPF.ar(input * cos1, filtFreq), filtFreq) * cos2) +
		 (LPF.ar(LPF.ar(input * sin1, filtFreq), filtFreq) * sin2) *
		 mul + add;
	}
}


-- 
CYa,
  Mario