Harmonic distortion of a input signal

[Christian Gollwitzer]

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