mov_avg.c

用dsp解压mp3程序的算法

/*************************************************************
*  mov_avg.c - C program for moving-average filtering
**************************************************************
*  System configuration:
*
*  x(n) |-----------------------|  y(n)
*  ---->| moving-average filter |----->
*       |-----------------------|
*     x(n) is the input data from data file "xn.dat"
*     y(n) is the output data to data file  "yn.dat"
*************************************************************/
#include <stdio.h>
#include <stdlib.h>
#include <math.h>
const float bnCoef[4] = {0.25, 0.25, 0.25, 0.25};
void main()
{
  void datamov();         // function to update signal vector
  float fir();            // function to perform FIR filtering
/*************************************************************
*    Define variables and arrays
*************************************************************/
  int i;                  // array index
  int order = 4;          // order of moving-average filter
  int input;              // input data from integer file
  float xn = 0;           // x(n), input from xn.dat file
  float yn = 0.0;         // y(n), output from FIR filter
  float xnBuf[4];         // signal buffer for FIR filter
/**********************************************************
*    Declare file pointers, open files, clear array
**********************************************************/
  FILE *xn_in;                 // file pointer of x(n)
  FILE *yn_out;                // file pointer of y(n)
  xn_in = fopen("xn.dat","r"); // open file for input x(n)
  yn_out = fopen("yn.dat","w");// open file for output y(n)
  for (i=0; i<order; i++)
    xnBuf[i] = 0.;             // clear signal buffer
/**********************************************************
*    Start of main program
**********************************************************/

  while( (fscanf(xn_in,"%d",&input)) != EOF)
  {                           // read x(n) from data file
    xn = (float)input;        // convert to floating-point
    datamov(xnBuf, order, xn);// refresh signal buffer
    yn = fir(xnBuf, bnCoef, order);// FIR filtering
    fprintf(yn_out,"%d\n",(int)(yn+0.5));
  }       // round to integer and write y(n) to output file
  fcloseall();                // close all opened files
}