Do you know if there is any references on PD in the
literature. Apart from the simple descriptions on Casio
manuals, I never saw anything else. 

yes, the PD technique as I understand it does not seem
to be bandlimited. But I wonder if there are any tricks
that are not documented anywhere.

Also do you know how to produce the resonant version
of PD? That was an interesting sound.

Interesting to see the classic topic of waveshaping being 
discussed, as well. In these days of fast computers, people
seemed to forget about these great ways of economically
synthesising complex spectra.

Victor


----- Original Message -----
From: Anthony Kozar <anthonykozar@sbcglobal.net>
Date: Wednesday, December 5, 2007 7:40 pm
Subject: Re: [Cs-dev] New opcodes useful?
To: Csound Developer list <csound-devel@lists.sourceforge.net>

> Well, if my intuitions are correct, using continuous k-rate 
> coefficientswith either the polynomial or chebyshevpoly opcodes 
> should produce smooth
> and continuous changes in the output.  I have tested the 
> latter by
> controlling several harmonics independently and I got smooth 
> changes just as
> if I had used additive synthesis with multiple 
> oscillators.  I would be
> interested to know if there is some mathematical problem that I am
> overlooking.
> 
> Regarding the phase distortion opcodes:  the reason I was 
> questioning their
> utility is that they DO produce aliasing because the derivative 
> of the
> resulting signal is discontinuous.  I think -- but am not 
> sure -- that
> Casio's original implementation of this technique was not 100% 
> digital.  But
> depending on the genre of music, aliasing is not always a bad 
> thing :)
> 
> Another use for the PD opcodes is to use them on audio signals 
> instead of
> phasors, in which case they behave as piecewise-linear transfer 
> functions.This also produces aliasing, but they have definite 
> applications as
> alternative distortion techniques.  powershape is also 
> excellent for
> distortion, although it can produce milder, bandlimited changes too.
> 
> At least this is my understanding of everything -- I am not a 
> DSP guru ...
> 
> Anthony Kozar
> anthonykozar AT sbcglobal DOT net
> http://anthonykozar.net/
> 
> 
> > Victor.Lazzarini@nuim.ie wrote on 12/5/07 4:00 AM:
> > 
> > Interesting... I am wondering if radical changes tothe the 
> transfer function
> > would cause discontinuities inthe output signal. Never thought 
> of the
> > question. I'll love to try them. Coincidentally, I was only
> > yesterdayteaching
> > a class on waveshaping.
> 
> >> Victor.Lazzarini@nuim.ie wrote on 12/5/07 2:54 AM:
> >> 
> >>> PD seem useful. UDOs are also good because they're 
> didactical, can you
> >>> do both?
> >> 
> >> Thanks.  I wrote the phase dist. opcodes (and powershape 
> below) a while ago
> >> but I will make UDOs too.
> >> 
> >>> How do the waveshaping opcodes you mention
> >>> differ from simply building them with oscillator and table
> >>> lookup?
> >> 
> >> They allow for _dynamic_ waveshaping where the transfer 
> function varies over
> >> time.  I have written the following opcodes so far and 
> hope to come up with
> >> some more:
> >> 
> >> aout  powershape    ain, kShapeAmount [, 
> ifullscale]>> aout  polynomial    ain, ka0 
> [, ka1 [, ka2 [...]]]
> >> aout  chebyshevpoly ain, ka0 [, ka1 [, ka2 [...]]]
> 
> 
> -----------------------------------------------------------------
> --------
> SF.Net email is sponsored by: The Future of Linux Business White Paper
> from Novell.  From the desktop to the data center, Linux is going
> mainstream.  Let it simplify your IT future.
> http://altfarm.mediaplex.com/ad/ck/8857-50307-18918-4
> _______________________________________________
> Csound-devel mailing list
> Csound-devel@lists.sourceforge.net
> https://lists.sourceforge.net/lists/listinfo/csound-devel

-------------------------------------------------------------------------
SF.Net email is sponsored by: The Future of Linux Business White Paper
from Novell.  From the desktop to the data center, Linux is going
mainstream.  Let it simplify your IT future.
http://altfarm.mediaplex.com/ad/ck/8857-50307-18918-4
_______________________________________________
Csound-devel mailing list
Csound-devel@lists.sourceforge.net