[PD] convolution using pd-vanilla
Alexandre Torres Porres
porres at gmail.com
Fri May 9 01:45:19 CEST 2014
and it took me quite some time to figure it out :)
2014-05-06 10:55 GMT-03:00 Oli Larkin <olilarkin at googlemail.com>:
> thanks everyone ... Alexandre that is just what i was looking for
>
>
> On 6 May 2014, at 06:09, Alexandre Torres Porres wrote:
>
> > I did one and shared on the list
> >
> > you can check it at:
> https://drive.google.com/file/d/0B3AoiT0xk8fnNU9PRHdldVVFbU0/edit?usp=sharing
> >
> >
> > 2014-05-05 16:41 GMT-03:00 katja <katjavetter at gmail.com>:
> > Brute force time domain convolution for small kernel can be done with
> > [fexpr~]. For zero phase filter kernels, fast convolution in Pd is
> > relatively simple. Multiply real and imaginary part of the signal's
> > spectrum with the filter's spectrum while using four times overlap and
> > Hann windowing before FFT and after IFFT, and normalize. Pd's FFT
> > routines assume x[0] at the start of the filter kernel, not at the
> > center, so you have to rotate your zero phase filter kernel before
> > taking it's Fourier Transform.
> >
> > Katja
> >
> > On Mon, May 5, 2014 at 8:49 PM, david medine <dmedine at ucsd.edu> wrote:
> > > For the FFT based convolution, you could easily modify the example
> patch
> > > I06.timbre.stamp.pd to do straight up convolution in the frequency
> domain. I
> > > wouldn't know how to do it in the time domain without an extern or a
> lot of
> > > painstaking work. It might be a nice thing to have, though.
> > >
> > > I can tell you, though, that the frequency domain method will out
> perform
> > > the time domain in terms of CPU usage. But, since you are windowing
> there
> > > will be a latency. Apart from that, the output is identical by both
> methods.
> > >
> > > y(n) = x(n) * g(n)
> > > Y(k) = X(k)G(k), y(n) = IDFT(Y(k))
> > >
> > > where g(n) is the impulse response, X(k) is the discrete Fourier
> transform
> > > of x(n) and * is the convolution operation.
> > >
> > >
> > > On 05/05/2014 09:33 AM, Oli Larkin wrote:
> > >>
> > >> hi,
> > >>
> > >> is anyone aware of an example of both a brute force time domain (e.g.
> > >> buffir~ in Max) and an FFT-based fast convolution patch in
> pd-vanilla? I
> > >> would like to do a comparison of the two. Can be using a small IR,
> just for
> > >> demo purposes.
> > >>
> > >> cheers,
> > >>
> > >> Oli
> > >>
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