fixpoint_leaky_lms.c

电话通信中我们常会遇到回音,如何消除?本程序用自适应滤波器消除回音的方法来处理.(使用于音频信号处理)

// 
//  Project: Experiment 10.7.3 AEC using C55x Intrinsics - Chapter 10
//  File name: fixPoint_leaky_lms.c   
//
//  Description: This AEC uses the fixed-point leaky LMS algorithm
//
//  For the book "Real Time Digital Signal Processing: 
//                Implementation and Application, 2nd Ed"
//                By Sen M. Kuo, Bob H. Lee, and Wenshun Tian
//                Publisher: John Wiley and Sons, Ltd
//  Tools used:   CCS v.2.12.07
//                TMS320VC5510 DSK Rev-C
//

#include "fixPoint_leaky_lms.h"

void fixPoint_leaky_lms(DTALK *dtObj, LMS *lmsObj)
{ 
  DTALK  *dt=(DTALK *)dtObj;
  LMS    *lms=(LMS *)lmsObj;
  long   temp32,ue;
  short  j,n,sign, step;
  short  *x,*w;
	
  n = lms->order;
  w = &lms->w[0];
  x = &lms->x[0];

  // Update data delay line
  for(j=n-1; j>0; j--)
  {
    x[j] = x[j-1];
  }
  x[0] = lms->in;
    
  // Get adaptive filter output - equation (7.2.19)
  temp32 = (long)w[0] * x[0]; 
  for(j=1; j<n; j++)
  {
    temp32 += (long)w[j] * x[j];
  }
  lms->out = (short)((temp32+ROUND)>>15);

  // Compute error term - equation (7.2.20)
  lms->err = lms->des - lms->out;

  if(!lms->freez)
  {
    long temp32a;

    // Coefficients update - equation (7.4.5)
    ue = (long)(((lms->err * (long)lms->mu))); 	
    temp32a = dt->farInPowM >>15;
    if ( temp32a >=32767) 
    {
      temp32a =32767;
    }
    else if (temp32a <=1) 
    {
      temp32a=1;
    }

    sign =1;
    if (ue <0) 
    {
      ue = -ue;
      sign = -1;
    }

    if (ue < dt->farInPowM) 
    {	
      step = div_l(ue, (short)temp32a);
    }
    else if (ue >= (dt->farInPowM<<1)) 
    {
      step = (short)(ue>>14);
    }
    step = step*sign;

    for(j=0; j<n ; j++)
    {
      temp32 = (((long) w[j])<<15);
      temp32 += (long) ((long)step * x[j]);
      w[j] = (short)((temp32+ROUND) >>15);
    }
  }
}