[PD] is this a spectral gate?

David Powers cyborgk at gmail.com
Wed Feb 21 19:41:33 CET 2007

This looks sweet, thanks Frank! Hoping to have a play with this as
soon as I get to do some actual music making later this week. By the
way, I thought I'd clarify what I meant with the example of Plogue
Bidule. The website invites one to: "Transform audio in the spectral
domain, with Bidule's FFT modules. Time domain audio is split into two
types of data, frequencies and magnitudes, which can be manipulated
using a wide variety of spectral bidules."

So basically, in most of the "simple" fft software, they split the
signal into freq and amplitude. You can see in the screenshot this is
represented by yellow and orange connectors, and they have specific
objects so you can play with a whole bunch of crazy transformations on
both freq and amp, and then you can resynthesize it back with an
inverse fft module.

I see that I can also get the freq and amplitude info from PD's fft,
once I'm awake enough to follow your math anyway! But I'm wondering
where the phase comes in exactly - in Plogue I'm assuming the phases
are somehow calculated auto-magically? They DO let you set the
blocksize of the signal with the fft. Also, how does this relate to
[fiddle~], because fiddle I understand, it gives me a fundamental freq
and the amplitude of some number of harmonics, and I could take that
info (for instance) to resynthesize stuff in some additive synth.


On 2/21/07, Frank Barknecht <fbar at footils.org> wrote:
> Hallo,
> David Powers hat gesagt: // David Powers wrote:
> > I wish there was an "fft for dumbies" ... or, I guess, some kind of
> > fft "black boxes" to play with, where you don't need to understand the
> > math. Frank's recent post completely lost me,
> Now I'm disappointed ...
> > though given a bit of study I can probably decode it.
> ... ah, and relieved a bit again. ;)
> > But, for instance, in Reaktor or Plogue Bidule, you can move stuff
> > into fft, mess with it, and resynthesize, without having any idea what
> > the hell the math is. In comparison, I really couldn't understand the
> > PD fft examples at all, it's just been too many years since I had a
> > math class.
> The power of Pd of course is, that you can influence things on a much
> lower level than NI allows you to do in Reaktor - although I admit,
> that I only know Reaktor from screenshots. The downside is, that you
> have to dig deeper to make the most out of Pd. This is especially true
> for FFT applications. The actual FFT patches often are very simple and
> they contain just of a handful of objects. It's the knowledge hidden
> inside that makes them difficult to understand.
> While you can skip a lot of the math, you cannot do FFT in Pd without
> at least understanding what kind of data is generated by the two
> [rfft~] outlets. Because without understanding this, you cannot even
> "fool around" with the data in between [rfft~] and [rifft~] in a
> meaningful way.
> Anyway, to give you a blackbox maybe like in Reaktor, attached is a
> Spectral Delay GOP abstraction ready to be dropped into any glitch
> patch.
> Ciao
> --
>  Frank Barknecht                 _ ______footils.org_ __goto10.org__
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