intfft2.c

dsp AD公司ADSP21的代码,里面有FFT FIR IIR EQULIZER G722_21F 等可以在项目中直接应用的代码.此代码的来源是ADI公司自己出版的书籍,此书在美国购得

#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <math.h>
#include "rtdspc.h"

/************************************************************************

INTFFT2.C - Interpolate 2:1 using FFT

Generates 2:1 interpolated time domain data.

*************************************************************************/

#define LENGTH 2048
#define M 11           /* must be log2(FFT_LENGTH) */

main()
{
    int          i;
    float        temp;
    COMPLEX      *samp;

/* allocate the complex array (twice as long) */
    samp = (COMPLEX *) calloc(2*LENGTH, sizeof(COMPLEX));
    if(!samp) {
        printf("\nError allocating fft memory\n");
        exit(1);
    }

/* copy input signal to complex array and do the fft */
    for (i = 0; i < LENGTH; i++) samp[i].real = getinput();

    fft(samp,M);

/* swap the real and imag to do the inverse fft */
    for (i = 0; i < LENGTH; i++) {
        temp = samp[i].real;
        samp[i].real = samp[i].imag;
        samp[i].imag = temp;
    }

/* divide the middle frequency component by 2 */
    samp[LENGTH/2].real = 0.5*samp[LENGTH/2].real;
    samp[LENGTH/2].imag = 0.5*samp[LENGTH/2].imag;

/* zero pad and move the negative frequencies */
    samp[3*LENGTH/2] = samp[LENGTH/2];
    for (i = LENGTH/2 + 1; i < LENGTH ; i++) {
        samp[i+LENGTH] = samp[i];
        samp[i].real = 0.0;
        samp[i].imag = 0.0;
    }

/* do inverse fft by swapping input and output real & imag */
    fft(samp,M+1);

/* copy to output and multiply by 2/(2*LENGTH) */
    temp = 1.0/LENGTH;
    for (i=0; i < 2*LENGTH; i++) sendout(temp*samp[i].imag);
    flush();
}