# Re: [music-dsp] 2-point DFT Matrix for subbands Re: FFT for realtime synthesis?

```
mr. g,I think what you're describing is the Cooley-Tukey Radix-2 FFT
algorithm.--r b-j                     r...@audioimagination.com"Imagination is
more important than knowledge."```
```
-------- Original message --------
From: gm <g...@voxangelica.net>
Date: 11/4/2018  4:14 PM  (GMT-08:00)
To: music-dsp@music.columbia.edu
Subject: [music-dsp] 2-point DFT Matrix for subbands Re: FFT for realtime
synthesis?

bear with me, I am a math illiterate.I understand you can do a Discrete Fourier
Transform in matrix form,and for 2-point case it is simply[ 1, 1   1,-1]like
the Haar transform, average and difference.My idea is, to use two successive
DFT frames, and to transform resepctive bins of two successive frames like
this.To obtain a better frequency estimate (subbands) from two smaller DFTs
instead of an DFT double the size.This should be possible? and the information
obtained, time and frequency resolution wise, identical.Except that you can
overlap the two DTFs.I basically want to find the dominant frequency in the FFT
bin, and sepreate it and discard the rest.And a subband resolution of 2 seems
to be a sufficient increase in resolution.But how do I get that from this when
there is no phase other then 0?I can see which of the two bands has more
energy, but how do I know "the true frequency" of Nyquist and DC?There is not
enough information.The problem persists for me if I resort to a 4-point
transform, what to do with the highest/lowest subband.(and also to understand
how to calculate the simple 4 point matrix, cause I am uneducated..)Or do I
need the 4-point case and discard "DC" and Nyquist subbands?Or is the idea
totally nonsens?Or is it justified to pick the subband that has more energy,
and then, what?_______________________________________________dupswapdrop:
music-dsp mailing
listmusic-dsp@music.columbia.eduhttps://lists.columbia.edu/mailman/listinfo/music-dsp```
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