readme.txt

快速傅立叶变换FFT的动态链接库DLL

FFT DLL Release 2
-----------------

Just a quick note on what this is...

It's a slightly altered version of Don Cross's ([e-mail])
fabulous Discrete Fast Fourier Transform code.

I make no assurances that it's bug or problem free.  What can I say?
I didn't spend a particularly large amount of time on it, but I've
been using it, and it has been working fabulously for me.

Essentially, I did five things:
 First, I made it compile with Visual C++ 2.2 as a DLL.  I made the
 three usable functions (fft_float(), fft_double(), and 
 Index_to_frequency()) use the WINAPI calling convention and exported
 them.  This means that this DLL is usable with Visual Basic as well
 as C and Delphi. 

 Second, I cast a couple doubles to floats in fft_float() to get rid
 of warnings.

 Third, I made a slightly tweaked version that compiles with LCC
 (the free-ish and wonderful Win32 C compiler).  I did this as a
 whole seperate set of files because I thought it was kinda nasty
 with directives.  The included DLL was built using these files.

 Fourth, I put together FFTLib.bas, which is a Visual Basic module
 with the appropriate Declares in it.  Stick this file in your VB
 project and you're good to go using the DLL.  This is found in the
 "ForVB" directory.

 Fifth, I put together FFTLib.H and FFT.LIB.  Include the header in
 your project, link the lib and you've got fftDouble(), fftFloat(),
 and indexToFrequency() at your disposal through the DLL.  This is
 found in the "ForC" directory.  The FFT.LIB I included was built
 using LCC.

I encourage people intrested in this code to take a look at Don
Cross's FFT page (http://www.intersrv.com/~dcross/fft.html).  It's
informative, has some good FFT-related links, and background on FFT
and digital audio.  You can also download the most recent version
of his FFT code (upon which this DLL is based), and (theoretically)
the most recent version of this DLL and my Visual Basic FFT code as
well.


Murphy McCauley 08/01/99
[e-mail]
http://www.fullspectrum.com/deeth/