用C实现FFT算法

用C语言编写FFT算法 

转http://blog.sina.com.cn/s/blog_65d639d50101buo1.html

#include "math.h"
#define PI 3.1415926
#define SAMPLENUMBER 512

void InitForFFT();
void MakeWave();
void FFT();

int INPUT[SAMPLENUMBER],DATA[SAMPLENUMBER];
float fWaveR[SAMPLENUMBER],fWaveI[SAMPLENUMBER],w[SAMPLENUMBER];
float sin_tab[SAMPLENUMBER],cos_tab[SAMPLENUMBER];

main()
{
int i;
InitForFFT();
MakeWave();
for ( i=0;i
{
fWaveR[i]=INPUT[i];
fWaveI[i]=0.0f;
w[i]=0.0f;
}
FFT(fWaveR,fWaveI);
for ( i=0;i
{
DATA[i]=w[i];
}
while ( 1 ); // break point
}

void FFT(float dataR[SAMPLENUMBER],float dataI[SAMPLENUMBER])
{
int x0,x1,x2,x3,x4,x5,x6,x7,x8,xx;
int i,j,k,b,p,L;
float TR,TI,temp;
for ( i=0;i
{
x0=x1=x2=x3=x4=x5=x6=x7=x8=0;
x0=i&0x01; x1=(i/2)&0x01; x2=(i/4)&0x01; x3=(i/8)&0x01;x4=(i/16)&0x01; x5=(i/32)&0x01; x6=(i/64)&0x01;x7=(i/128)&0x01;x8=(i/256)&0x01;
xx=x0*256+x1*128+x2*64+x3*32+x4*16+x5*8+x6*4+x7*2+x8;
dataI[xx]=dataR[i];
}
for ( i=0;i
{
dataR[i]=dataI[i]; dataI[i]=0; 
}

for ( L=1;L<=9;L++ )
{
b=1; i=L-1;
while ( i>0 ) 
{
b=b*2; i--;
}
for ( j=0;j<=b-1;j++ )
{
p=1; i=9-L;
while ( i>0 )
{
p=p*2; i--;
}
p=p*j;
for ( k=j;k<512;k=k+2*b )
{
TR=dataR[k]; TI=dataI[k]; temp=dataR[k+b];
dataR[k]=dataR[k]+dataR[k+b]*cos_tab[p]+dataI[k+b]*sin_tab[p];
dataI[k]=dataI[k]-dataR[k+b]*sin_tab[p]+dataI[k+b]*cos_tab[p];
dataR[k+b]=TR-dataR[k+b]*cos_tab[p]-dataI[k+b]*sin_tab[p];
dataI[k+b]=TI+temp*sin_tab[p]-dataI[k+b]*cos_tab[p];
}
}
}
for ( i=0;i
{ 
w[i]=sqrt(dataR[i]*dataR[i]+dataI[i]*dataI[i]);
}
}


void InitForFFT()
{
int i;
for ( i=0;i
{
sin_tab[i]=sin(PI*2*i/SAMPLENUMBER);
cos_tab[i]=cos(PI*2*i/SAMPLENUMBER);
}
}

void MakeWave()
{
int i;
for ( i=0;i
{
INPUT[i]=sin(PI*2*i/SAMPLENUMBER*30)*1024;
}
}