fix_fft-doc.txt

里面有一对定点FFT和IFFT算法

Here it is... an integer FFT routine that's pretty fast.  I've only tested
it on a 68k powerbook, and it's much faster than either software floating
point or the built in FPU.  The orignal source was DOS only and came off 
the net.  
I simply removed the ugly DOS stuff and did some simple testing.  I do not
guarantee that it works... but try compiling with -DMAIN to test it yourself.

Those of you with impoverished floating point hardware (notably, some new
Powerbooks, and maybe even Intel machines) might find these routines
useful.

Input and output is an array of shorts.  I haven't tested all the routines,
but the FFT looks good enough to use.  It keeps a table of trig functions, so
it will only run up to 1024 points.

-- Malcolm

Written by:  Tom Roberts  11/8/89
Made portable:  Malcolm Slaney 12/15/94 malcolm (AT) interval.com