### jit.fft

Ok I know for audio when you do an fft on a signal you specify the size of the fft(frequency resolution). Then you get a vector of complex numbers that represent the magnitude and phase of frequencies that correspond to fs/2*n*(freqres) where n is the index of the vector…. (in the looses sense here). So my question is what exactly is the format that jit.fft spits out. Since it operates on two plane matrices I’m guessing that this will determine what data is spit out. Can someone help me understand this object?

On Aug 8, 2006, at 5:04 PM, Tyler Nitsch wrote:

>

> Ok I know for audio when you do an fft on a signal you specify the

> size of the fft(frequency resolution). Then you get a vector of

> complex numbers that represent the magnitude and phase of frequencies

> that correspond to fs/2*n*(freqres) where n is the index of the

> vector…. (in the looses sense here). So my question is what exactly

> is the format that jit.fft spits out. Since it operates on two plane

> matrices I’m guessing that this will determine what data is spit out.

> Can someone help me understand this object?

I’d suggest you check out the jit.fft-threshold.pat example and other

jit.fft examples and let us know if you have additional questions. Keep

in mind that in an fft, you have both positive and negative frequencies

(about the center vertically and horizontally in the 2D case), and that

in a 2D fft the harmonics have frequencies about each axis as

determined by the cell position. real and imaginary coordinates are in

the matrix planes 0 and 1 respectively. More info on 2D ffts can be

found online.

-Joshua

Thanks for the tips. Ok for future browsers and searchers of this topic after doing a little bit of digging and weeding I finally found an article that explains the relation between locations and values of the 2d fft and the actuall spatial image.