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Mark Borgerding 2004-04-04 22:12:40 +00:00
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@ -35,13 +35,13 @@ Code definitions for 1d complex FFTs are in kiss_fft.c.
You can do other cool stuff with the extras you'll find in tools/
* arbitrary dimension FFTs (complex only currently, apologies to Steve DeKorte -- mebbe next time )
* real FFTs
* fast convolution filtering
* arbitrary dimension complex FFTs
* 1-d real FFTs
* fast convolution FIR filtering
* spectrum image creation
The core fft and most tools/ code can be compiled to use float, double
or 16bit short samples. The default is float.
or Q15 short samples. The default is float.
BACKGROUND:
@ -57,7 +57,7 @@ a well respected and highly optimized fft library. I don't want to criticize
this great library, so let's call it FFT_BRANDX.
During this process, I learned:
1. FFT_BRANDX has more than 100K lines of code. The core of kiss_fft is about 500 lines (cpx 1-d).
1. FFT_BRANDX has more than 100K lines of code. The core of kiss_fft is about 500 lines (cpx 1-d).
2. It took me an embarrassingly long time to get FFT_BRANDX working.
3. A simple program using FFT_BRANDX is 522KB. A similar program using kiss_fft is 18KB.
4. FFT_BRANDX is roughly twice as fast as KISS FFT.
@ -86,11 +86,10 @@ UNDER THE HOOD:
No scaling is done. Optimized butterflies are used for factors 2,3,4, and 5.
The real optimization code only works for even length ffts. It does two half-length
FFTs in parallel (packed into real&imag) then twiddles.
FFTs in parallel (packed into real&imag), and then combines them via twiddling.
The fast convolution filtering uses the overlap-scrap method, slightly
modified to put the scrap at the tail.
LICENSE:
BSD, see COPYING for details. Basically, "free to use&change, give credit where due, no guarantees"
@ -105,7 +104,6 @@ TODO:
*) Make doc describing the overlap (tail) scrap fast convolution filtering in kiss_fastfir.c
*) Test all the ./tools/ code with fixed point (kiss_fastfir.c doesn't work, maybe others)
AUTHOR:
Mark Borgerding
Mark@Borgerding.net