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Article #159

Need help to find fundamental frequency!

#159
From: Shigenori Horio
Date: Thu, 30 Jul 1992 00:57
33 lines
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Hello!  I recently started learning signal processing algorithms for my thesis.
I have some problems understanding the theory and converting it to the C code.
My theis deals with musical instruments' acoustic signals and finding its
fundamental frequencies.

I am testing this with my Amiga 3000, getting a 8 bit long signal from parallel
port. Right now I am playing an electoric guitar and sending the signal to the
port. Hopefully, I would like to find a sequence of the fundamental frequencies
from the input singal in real-time.  

Now, my questions are:

	Is there any fast algorithms written in any programming language that
retrieves the fundamental frequency without going through FFT algorithm?

	If not, I think I understand that I have to make a window (array of
N elements, x[n]) and pass this to DFT alorithm, and move the window to the
next sampling data by N or N/2.

I have gotten some of the DFT alorithms written in C such as fft() and realfft()
which inputs a data array(size sixteen) and returning an output array which is
also the size sixteen, x[16].  Now, to find the fundamental frequency out of
the output array, do I have to go through all the elements in the array and find
the maximum value in x[k]? (Does it need N times comparisons for the window
size N: x[N]?)  Does this bring to the result that the fundamental frequency
is (R / 16) * k?  Also, can the input data array be the 8 bit long signal that
I am getting from the port?

	Any kind of advice, suggestions, corrections, or coding is rally 
appreciated.

-Fory Horio (shorio@polyslo.csc.calpoly.edu
             or shorio@bach.csc.calpoly.edu)
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From: shorio@polyslo.csc.calpoly.edu (Shigenori Horio)
Subject: Need help to find fundamental frequency!
Message-ID: <1992Jul30.005716.25410@rat.csc.calpoly.edu>
Date: Thu, 30 Jul 92 00:57:16 GMT
Organization: Cal Poly State Univ,CSC Dept,San Luis Obispo,CA 93407
Nntp-Posting-Host: polyslo.csc.calpoly.edu
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