smcbg.c

语音CELP压缩解压源代码（C语音)

/**************************************************************************
*
* ROUTINE
*               smoothcbgain
*
* FUNCTION
*
*               smooth cbgain values when two errors detected in
*		Hamming block
*
* SYNOPSIS
*               smoothcbgain(cbgain,twoerror,syndavg, gains, subframe)
*
*   formal
*                       data    I/O
*       name            type    type    function
*       -------------------------------------------------------------------
*       cbgain		float	i/o	input cbgain
*	twoerror	int	i	two error flag
*	syndavg		float	i	error rate estimation parameter
*	gains		float	i	vector of gains to calculate variance
*	subframe	int	i	subframe number
*
*   external
*                       data    I/O
*       name            type    type    function
*       -------------------------------------------------------------------
*	frame		int	i
*
***************************************************************************
*
* DESCRIPTION
*
*	Smoothing routine to smooth cbgain when errors are detected:
*
*	If the variance of past cbgain values is within the range VARLIMIT,
*	the validity of the current cbgain value is tested.  If the current
*	value of cbgain is within the range CBGAINLIMIT, cbgain is passed.
*	If CBGAIN is not within  the range CBGAINLIMIT it is reset to the 
*	average value of the surrounding cbgain values.
*
*	The array OLDCBGAIN contains past values of cbgain.  The array
*	GAINS contains current and future values of cbgain.  The array 
*	VECTOR is constructed from the arrays OLDCBGAIN and GAINS
*	depending on the current subframe.  CBGAIN is smoothed based on 
*	the statistics of VECTOR, which contains the nearest four
*	surrounding cbgain values, both past and future values, except
*	where future values are not available (subframes 3 and 4).
*
*	NOTE:  The smoothing parameters should be capable of adapting
*	to various bit error rate estimates.  For example, different
*	values of SYNDAVG should select different levels of CBGAINLIMIT,
*	VARLIMIT, and SYNDAVG.
*
***************************************************************************
*
* CALLED BY
*
*       celp
*
* CALLS
*
*       variance
*
**************************************************************************/
#define CBGAINHISTORY	4
#define CBGAINLIMIT	300.0
#define VARLIMIT	30000.0
#define SGAINLIMIT	9.0
#define SVARLIMIT	10.0
#define AVGLIMIT	6.0
#define SYNDLIMIT	0.04
#define TRUE		1
#define FALSE		0
#include <math.h>
#include "ccsub.h"
extern int frame;
smoothcbgain(cbgain, twoerror, syndavg, gains, subframe)
int twoerror, subframe;
float *cbgain, syndavg, gains[];

{
  int i, sign;
  static int enable;
  float avg, var, abscbgain, vector[4];
  static float oldcbgain[CBGAINHISTORY];

  abscbgain = fabs(*cbgain);
  if (subframe != 4)
    enable = TRUE;
  if ((twoerror || syndavg > SYNDLIMIT) && enable)
  {
    if (subframe == 1)
    {
      vector[0] = oldcbgain[0];
      vector[1] = oldcbgain[1];
      vector[2] = fabs(gains[1]);
      vector[3] = fabs(gains[2]);
    }
    else if (subframe == 2)
    {
      vector[0] = oldcbgain[0];
      vector[1] = oldcbgain[1];
      vector[2] = fabs(gains[2]);
      vector[3] = fabs(gains[3]);
    }
    else if (subframe == 3)
    {
      vector[0] = oldcbgain[0];
      vector[1] = oldcbgain[1];
      vector[2] = oldcbgain[2];
      vector[3] = fabs(gains[3]);
    }
    else if (subframe == 4)
    {
      vector[0] = oldcbgain[0];
      vector[1] = oldcbgain[1];
      vector[2] = oldcbgain[2];
      vector[3] = oldcbgain[3];
    }
    else
      printf("smoothcbgain: Error in subframe number\n");

    variance(vector, 4, &var, &avg);
    sign = nint(*cbgain / fabs(*cbgain));
    if (var < VARLIMIT &&
	(abscbgain > avg + CBGAINLIMIT || abscbgain < avg - CBGAINLIMIT))
    {
      abscbgain = avg;
      printf("smoothcbgain:  cbgain value reset to avg cbgains at frame %d subframe %d\n", frame, subframe);
      *cbgain = sign * abscbgain;
      if (subframe == 3)
      {
	enable = FALSE;
	printf("smoothcbgain:  smoothing disabled for subframe 4\n");
      }
    }

    if (var < SVARLIMIT && abscbgain > SGAINLIMIT &&
	avg < AVGLIMIT && enable)
    {
      abscbgain = avg;
      *cbgain = sign * abscbgain;
      printf("smoothcbgain:  %s at frame %d subframe %d\n",
	   "cbgain value reset to avg cbgains (silence?)", frame, subframe);
      if (subframe == 3)
      {
	enable = FALSE;
	printf("smoothcbgain:  smoothing disabled for subframe 4\n");
      }
    }
  }
  for (i = CBGAINHISTORY - 1; i > 0; i--)
    oldcbgain[i] = oldcbgain[i - 1];
  oldcbgain[0] = abscbgain;
}