30 Sep
2010
30 Sep
'10
2:18 p.m.
On Thu, Sep 30, 2010 at 07:15:32AM -0400, Dave Phillips wrote:
Robin Gareus wrote:
since the FFT is just a fast way to compute the DFT
it might make more sense if you understood the DFT.
understanding why the FFT works, and why its faster is only useful if
you want to use it.
http://en.wikipedia.org/wiki/Discrete_Fourier_transform
In layman terms:
There's a smart French guy by the name of Joseph F. sitting inside it:
If you play him some audio: He thinks: "Hey, this is actually just a few
simple sine-waves added together (superpositioned)", he quickly
calculates their frequencies and amplitudes and asks "Now, you want to
change the duration?" easy: "I'll generate some new sine-waves with
these frequencies and amplitudes, how long did you say you want?"
(The smart thing about this French guy is that he actually speaks fluent
English - Sorry I could not resist :)
I recall a brief exchange on a DSP list that went something like this:
Q: Can anyone explain the FFT in simple terms ?
A. No.
I have read and understood some articles and descriptions of the
FFT. Mark Dolson's original article on the phase vocoder (in the
Computer Music Journal V10,#4, Winter 1986), is still a good
introduction for computer-based musicians, though it may be a bit
too technical by contemporary standards.
Louigi, take a look at some descriptions of what an FFT does. It
does use "windows" but you'll have to do some homework to find out
what's meant by the term in this context.
http://en.wikipedia.org/wiki/FFT
Beware, that page is a maths page, it's not directly concerned with
the use of the FFT in music/sound applications.
And btw, I agree wrt Paul's Extreme Stretch, it's a great tool.
Best,
dp
_______________________________________________
Linux-audio-dev mailing list
Linux-audio-dev(a)lists.linuxaudio.org
http://lists.linuxaudio.org/listinfo/linux-audio-dev
--
torben Hohn