[PD] Window Functions

[Matt Barber]

Excellent, thanks. One reason I'm wondering is that many definitions of
window functions in DSP texts and online define Hann as something like
0.5*(1 - cos((2*pi*n)/(N - 1))), which is the symmetric version, 0 at both
ends. With overlap-add it puts a repeated value at both peak and trough,
but still with the FFT periodicity.

On Sat, Jan 9, 2016 at 7:02 AM, katja <katjavetter at gmail.com> wrote:

> Hi Matt,
>
> What I remember from FFT experiments is, a 'periodic' Hann window
> (asymmetric) gives best results for overlap-add. You can think of the
> window as two functions: the DC component preserves the original
> signal, while the cosine component produces sum- and difference
> frequencies which cancel each other in subsequent overlaps after IFFT.
> Long story and illustrations here:
>
> http://www.katjaas.nl/FFTwindow/FFTwindow&filtering.html
>
> Katja
>
>
> On Sat, Jan 9, 2016 at 6:39 AM, Matt Barber <brbrofsvl at gmail.com> wrote:
> > Hi list, quick DSP question.
> >
> > In I02.Hann.window.pd there is a Hann window computed by running an
> [osc~]
> > for one cycle over 512 samples. Doing it this way is simple but it means
> > that it doesn't taper all the way to 0 on the right (the next value of
> the
> > oscillator after writing the table is 0). I don't know why I hadn't
> thought
> > of this before, but is this asymmetry mathematically optimal for
> windowing
> > of a single frame? What about in an overlap-add context? I'm trying to
> > understand the logic, so I'm not too worried about whether it makes a
> > practical difference. A period of 511 samples would be symmetric and
> > 0-valued at both ends, but there would be no "middle" value at unity.
> >
> > What's the best way to think of this?
> >
> > Matt
> >
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