Harmonic distortion of a input signal

[jmfauth]

On 20 mai, 19:56, Christian Gollwitzer <aurio... at gmx.de> wrote:
> Oops, I thought we were posting to comp.dsp. Nevertheless, I think
> numpy.fft does mixed-radix (can't check it now)
>
> Am 20.05.13 19:50, schrieb Christian Gollwitzer:
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> > Am 20.05.13 19:23, schrieb jmfauth:
> >> Non sense.
>
> > Dito.
>
> >> The discrete fft algorithm is valid only if the number of data
> >> points you transform does correspond to a power of 2 (2**n).
>
> > Where did you get this? The DFT is defined for any integer point number
> > the same way.
>
> > Just if you want to get it fast, you need to worry about the length. For
> > powers of two, there is the classic Cooley-Tukey. But there do exist FFT
> > algorithms for any other length. For example, there is the Winograd
> > transform for a set of small numbers, there is "mixed-radix" to reduce
> > any length which can be factored, and there is finally Bluestein which
> > works for any size, even for a prime. All of the aforementioned
> > algorithms are O(log n) and are implemented in typical FFT packages. All
> > of them should result (up to rounding differences) in the same thing as
> > the naive DFT sum. Therefore, today
>
> >> Keywords to the problem: apodization, zero filling, convolution
> >> product, ...
>
> > Not for a periodic signal of integer length.
>
> >> eg.http://en.wikipedia.org/wiki/Convolution
>
> > How long do you read this group?
>
> >      Christian

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Forget what I wrote.
I'm understanding what I wanted to say, it is badly
formulated.

jmf