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@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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