[music-dsp] oscillator problems help....
hplus at mindcontrol.org
Sat Feb 23 20:04:24 EST 2002
> > The reason higher frequency tones have a lower amplitude is probably
> > because your lowpass filter filters those tones and thus they get
> > softer (well, that's what a lowpass DOES :-)
> well, it attenuates on the high freqs and amplifies the lower without a
> lopass filter on the output. The oscillator itself (-2*cos(w)*y1-y2, a
> standard lopass with radius set to 1 for ocillation)contains this kind of
> behaviour(at least in this case).
Do you re-set the oscillator memory when you change the coefficients?
If not, that can cause these issues. Of course, re-setting the memory
means that you re-set the current phase, too, which is why you need some
form of phase recovery and re-initialization for the oscillator.
> but if i preserve phase won't I get an sinusoid-oscillator with varying
> phase from case to case then?
Yes. That's great, because that's what you want. If the sinusoid is
formulated as sin( tw + p ) then you want the p that keeps the function
continuous (and retains the sign of the derivative) for minimum glitch
artifacts. This means adjusting p accordingly.
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