Re: [Numpy-discussion] Zoom fft code

[Stéfan van der Walt]

Hi Nadav

I recall that you posted an implementation yourself a while ago!

http://www.mail-archive.com/numpy-discussion@scipy.org/msg01812.html

Regards
Stéfan

2009/1/5 Nadav Horesh nad...@visionsense.com:

  I am looking for a zoom fft code. I found an old code by Paule Kinzle (a 
 matlab code with a translation to numarray), but its 2D extension (czt1.py) 
 looks buggy.

  Nadav.
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Re: [Numpy-discussion] Zoom fft code

[Nadav Horesh]

Thank you, I lost the code so thank you for finding it. In addition, chirp z 
transform is broader then zoom fft. There was someone on this list that was 
interested especially in zoom fft, so I was wondered if there is a code for it. 
Anyway, I can use my old code again.

   Nadav

  


-הודעה מקורית-
מאת: numpy-discussion-boun...@scipy.org בשם St?fan van der Walt
נשלח: ב 05-ינואר-09 10:25
אל: Discussion of Numerical Python
נושא: Re: [Numpy-discussion] Zoom fft code
 
Hi Nadav

I recall that you posted an implementation yourself a while ago!

http://www.mail-archive.com/numpy-discussion@scipy.org/msg01812.html

Regards
St?fan

2009/1/5 Nadav Horesh nad...@visionsense.com:

  I am looking for a zoom fft code. I found an old code by Paule Kinzle (a 
 matlab code with a translation to numarray), but its 2D extension (czt1.py) 
 looks buggy.

  Nadav.
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Re: [Numpy-discussion] Zoom fft code

[Stéfan van der Walt]

2009/1/5 Neal Becker ndbeck...@gmail.com:
 I was not aware that chirp-z transform can be used to efficiently compute DFT 
 over a limited part of the spectrum.  I could use this.  Any references on 
 this technique?

The only reference I have is the one mentioned in the source:

Rabiner, L.R., R.W. Schafer and C.M. Rader.
The Chirp z-Transform Algorithm.
IEEE Transactions on Audio and Electroacoustics, AU-17(2):86--92, 1969

The discrete z-transform,

X(z_k) = \sum_{n=0}^{N-1} x_n z^{-n}

is calculated at M points,

z_k = AW^-k, k = 0,1,...,M-1.

You can think of the z_k's as a spiral, where A controls the outside
radius (starting frequency) and W the rate of inward spiralling.

Regards
Stéfan
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