[PD] a little pitchshifter

Mike McGonagle mjmogo at gmail.com
Mon Mar 5 21:15:26 CET 2007

I don't want to change the subject (and if needed, we can start a new
thread), but as this might be a related topic, here it is...

What would it take to turn this into a "Slowdown" abstraction?
Basically, I am interested in slowing down the tempo of a sound, but
NOT changing the pitch...

Am I off-base on this? Or can this be used as the starting point for
what I described?



On 3/5/07, Frank Barknecht <fbar at footils.org> wrote:
> Hallo,
> Kyle Klipowicz hat gesagt: // Kyle Klipowicz wrote:
> > Could aliasing be avoided by using a multi-pole low pass filter at
> > nyquist before sending the signal to the dac?
> No: Alias frequencies aren't too high, they are wrong frequencies,
> that have been mirrored at the Nyquist border. As soon as you try to
> play a sinewave at Nyquist + x, what you get is a sine at Nyquist - x,
> and you cannot lowpass out this frequency after it has been
> introduced.
> You can however upsample your signal first, then use a lowpass filter,
> then downsample again. See this chapter in The Book for more info:
> http://crca.ucsd.edu/~msp/techniques/latest/book-html/node194.html
> and J07.oversampling.pd
> Ciao
> --
>  Frank Barknecht                 _ ______footils.org_ __goto10.org__
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