/*
exp7d.c - Experiment for FFT convolution
using Overlap-Add method
*/
#include "icomplex.h"
#include "input7.dat" /* This is the data file used in Chapter 5 */
#define L 48 /* Filter length */
#define N 1024 /* FFT size, N >= L+M-1 */
#define EXP 10 /* MM = log2(N) */
#define M (N-L+1) /* Data sample length */
#pragma DATA_SECTION(U, "fft_twd");
#pragma DATA_SECTION(X, "fft_temp");
#pragma DATA_SECTION(H, "fft_coef");
#pragma DATA_SECTION(LP_h, "fft_coef");
#pragma DATA_SECTION(OVRLAP, "fft_in");
#pragma DATA_SECTION(re1, "fft_temp");
#pragma DATA_SECTION(re2, "fft_temp");
#pragma CODE_SECTION(main, "fft_code");
complex X[N]; /* Signal buffer */
complex H[N]; /* Frequency domain Filter */
complex U[N]; /* Twiddle e^(-j2pi/N) table */
int OVRLAP[L-1]; /* Frequency domain overlap buffer */
int re1[N],re2[N];
/* Low-pass FIR filter coefficients */
#include "firlp48.dat" /* This is the same filter used in Chaper 5 */
//#include "firlp8.dat"
//#include "firlp16.dat"
//#include "firlp32.dat"
//#include "firlp64.dat"
//#include "firlp128.dat"
//#include "firlp256.dat"
//#include "firlp512.dat"
extern void fft(complex *, unsigned int, complex *, int);
extern void bit_rev(complex *, unsigned int);
extern void w_table(complex *, unsigned int);
extern void olap_add(complex *, int *, unsigned int, unsigned int, unsigned int);
extern void freqflt(complex *, complex *, unsigned int);
main()
{
unsigned int i,j;
/* Initialization */
for (i=0; i OVRLAP[i] =0;
for (i=0; i {
X[i].re = LP_h[i];
X[i].im = 0;
}
for (i=i; i {
X[i].re = 0;
X[i].im = 0;
}
w_table(U,EXP); /* Create Twiddle lookup table for FFT */
bit_rev(X,EXP); /* Bit reversal arrange the coefficient */
fft(X,EXP,U,1); /* FFT to the filter coefficients */
for (i=0; i {
H[i].re = X[i].re H[i].im = X[i].im }
/* Start FFT Convolution test */
j=0;
for (;;)
{
for (i=0; i {
X[i].re = input[j++]; /* Generate input samples */
X[i].im = 0;
re1[i] = X[i].re; /* Copy to reference buffer */
if (j==160)
j=0;
}
for (i=i; i {
X[i].re = 0;
X[i].im = 0;
}
/* Start FFT convolution */
bit_rev(X,EXP); /* Arrange sample in bit reversal order */
fft(X,EXP,U,1); /* Perform FFT */
freqflt(X,H,N); /* Perform frequency domain filtering */
bit_rev(X,EXP); /* Arrange sample in bit reversal order */
fft(X,EXP,U,0); /* Perform IFFT */
olap_add(X,OVRLAP,L,M,N); /* Overlap and add algorithm */
/* end of FFT convolution */
for (i=0; i {
re2[i] = X[i].re;
}
}
}
