Re: AUDITORY Digest - 29 Jul 2002 to 30 Jul 2002 (#2002-117)

[Ian Knopke <knopke@xxxxxxxxxxxxxxx>]

Marius,

There is lots of source code on the net to do fourier transforms. Here are
two packages

http://www.fftw.org/
http://www.library.cornell.edu/nr/bookcpdf.html (section 12)

This a good online book which explains the principles behind the fourier
transform:

http://www.dspguide.com/pdfbook.htm

If you already have the data in 512 byte array then the hardest part is
done. Good luck!


Ian Knopke
PhD Music Technology
McGill University


> Hello everyone,
>
> I am in desperate need of a way to determine the frequency content of a
> 'raw' amplitude-time sample.  I know that Fourier Transform can do this, but
> all of the texts I have read are at the advanced level, and quite frankly I
> have no idea what they are talking about.
>
> The raw data is in the form of a 512 byte array, defined as char
> rawdata[512].  This array is continually filled by my microphone audio
> grabbing code.  Now I need to be able to pass this array to a function which
> would fill another array, say fourierdata, with the frequency information.
>
> If anyone can be of assistance, I would really appreciate it.  Specifically,
> if you can supply me with C code to implement such a fourier function, I
> would be very greatful.
>
> Thank you,
> Marius Myburg