[PD] Equalizer

Frank Barknecht barknech at ph-cip.uni-koeln.de
Tue Aug 28 10:44:01 CEST 2001

Álvaro Castro hat gesagt: // Álvaro Castro wrote:

> Finally, I would like to know what's the best way to
> work with pure (or almost pure) frecuencies. That's
> the reason I want to build an equalizer. I would like
> to add, increase, delete or decrease specific
> frecuencies. Is that posible with Pure-data??

I am contemplating something similar for some days now: I would
like to have something like Native Instruments "Spectral Delay" in
PD. Using the fourier transformation is the way to go. But this is
non-trivial mathematics and DSP programming stuff and I am still in
the research phase.  You might want to look at all the patches in
4.fft.examples and for some theory read www.dspdimension.com. 

Basically you should be able to analyze audio data into the
frequency domain, cut out or change some frequencies and
resynthesize this sound with an inverse fft. 07.tinbell.pd
shows how to boost certain frequencies with fft.  I don't
know if this would be appropriate for an equalizer, though,
as the sound could get changed (frequency smear etc.) But
in a spectral delay I could live with this.

But I still don't know how to cut out the frequencies :(

Maybe some dsp guru can show this? If you find out how this is done please
post it here.

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