ale_fixpt.c

用dsp解压mp3程序的算法

/*****************************************************************
*  ale_fixpt.c - Fixed-point C program for implementing ALE
******************************************************************
*  System configuration:
*
* d(n) ---------------------------
*     |             /             |
* d(n-1)|----------------| out(n) V
*  ---->| ALE (LMS-FIR)  |-----> |+|----->
*       |----------------|     -      | 
*             /_______________________|
*
*
*     d(n) is the input data from data file "in_int.dat"
*****************************************************************/

#include <stdio.h>
#include <stdlib.h>
#include <math.h>

void main()
{

  /***************************************************************
  *    Define variable arrays, define and clear variables
  ***************************************************************/

  #define NL 16		     /* length of FIR filter            */
  long yn = 0;               /* y(n), output from filter        */
  int xn;
  int xnbuf[NL];
  int w[NL];
  int i,j,k;
  int mu = 338;		    /* 33(0.001); 338(0.01); 655(0.02)  */
  int mu_err;
  int dn = 0;
  int err;

  /***************************************************************
  *    Declare file pointers
  ***************************************************************/

  FILE *xn_in;              /* file pointer of x(n)             */
  FILE *yn_out;             /* file pointer of y(n)             */
  FILE *w_out;              /* file pointer of w(0)             */
  FILE *err_out;            /* file pointer of e(n)             */
  xn_in = fopen("in_int.dat","r");  /* open file for input x(n) */
  yn_out = fopen("out_int.dat","w");/* open file for output y(n)*/
  w_out = fopen("w_int.dat","w");   /* coefficient file         */
  err_out = fopen("err_int.dat","w");/* error signal file       */
  /***************************************************************
  *    Start of main program
  ***************************************************************/
  for(k=0;k<NL;k++)
  {                     /* clear signal and coefficient buffers */
    xnbuf[k]=0;
    w[k] = 0;
  }

  while ((fscanf(xn_in,"%d",&xn)) != EOF)
  {          /* read in x(n) from data file and processing it   */
    for (i=NL-1;i>0;i--)
    {
      xnbuf[i]=xnbuf[i-1];   /* refresh signal buffer           */
    }
    xnbuf[0]=dn;             /* elayed version of dn            */
    dn = xn;                 /* delay by 1                      */    

    yn = 0; 
    for (j=0; j< NL; j++)    /*    FIR filtering                */	
    {
      yn += ((long)(int)xnbuf[j] * (long)(int)w[j])>>15;	
    } 
 
    err = dn-yn;             /* e(n) = d(n) - y(n)              */
    mu_err = (int)(((long)(int)mu*(long)(int)err)>>15);

    /*    update filter coeffificient                           */

    for (k=0; k< NL; k++)
    {
      w[k]=w[k]+(int)(((long)(int)mu_err*(long)(int)xnbuf[k])>>15);
    }
	
    fprintf(yn_out,"%d\n",(int)(yn));
    fprintf(w_out,"%d\n",(int)w[0]);
    fprintf(err_out,"%d\n",(int)err);
	
  }
  printf("Finish");	      /* complete filtering             */  
  fcloseall();                /* close all opened files         */
}