intsynth.c

语音CELP压缩解压源代码（C语音)

/**************************************************************************
*
* ROUTINE
*		intsynth
*
* FUNCTION
*		Linearly interpolate between transmitted LSPs
*		to generate nn (=4) intermediate sets of LSP
*		frequencies for subframe synthesis. 
*		
*
* SYNOPSIS
*		subroutine intsynth(lspnew, nn, lsp, twoerror, syndavg)
*
*   formal 
*
*                       data    I/O
*       name            type    type    function
*       -------------------------------------------------------------------
*	lspnew		float	i/o	new frequency array
*	nn		int	i	number of segments/frame
*	lsp		float	o	interpolated frequency matrix
*	twoerror	int	i	flag for occurrence of two errors
*					  in Hamming protected bits.
*	syndavg		float	i	bit error estimation parameter
*
*   external 
*                       data    I/O
*       name            type    type    function
*       -------------------------------------------------------------------
*	no		int	i
*	frame		int	i
*
***************************************************************************
*
* DESCRIPTION
*		This routine interpolates lsp's for subframe synthesis.
*	This version is only for use with absolute scalar LSP coding!
*	The interpolated LSPs are identical to the interpolated set in the
*	transmitter provided there are no transmission errors.  If the 
*	LSP's are nonmonotonic, then LSP errors have occured and an 
*	attempt is made to "fix" them by repeating previous LSP values. 
*	If this correction fails (the vector is still nonomonotonic),
*	then the entire previous LSP vector is repeated.  (This version
*       ignores twoerror and syndavg.)
*
*
***************************************************************************
*
* CALLED BY
*
*	celp
*
* CALLS
*
*	lsptopc  rctopc
*
**************************************************************************/
#define TRUE	1
#define FALSE	0
#include "ccsub.h"
extern int no, frame;
intsynth(lspnew, nn, lsp, twoerror, syndavg)
int nn, twoerror;
float lspnew[], lsp[][MAXNO], syndavg;
{
  int i, j, nonmono;
  float temp[MAXNO+1], rc[MAXNO], dlsp[MAXNO + 1];
  static float w[2][4] =   
  {
    0.875, 0.625, 0.375, 0.125,  
    0.125, 0.375, 0.625, 0.875
  };
  static float lspold[MAXNO] =
  {
    .03, .05, .09, .13, .19, 
    .23, .29, .33, .39, .44
  };

  /* *try to fix any nonmonotonic LSPs by repeating pair	 */

  for (i = 1; i < no; i++)
  {
    if (lspnew[i] <= lspnew[i - 1])
    {
      printf("intsynth: try to fix any nonmonotonic LSPs\n");
      lspnew[i] = lspold[i];
      lspnew[i - 1] = lspold[i - 1];
    }
  }

  /* *check fixed LSPs (also check for pairs too close?)	 */

  nonmono = FALSE;
  for (i = 1; i < no; i++)
  {
    if (lspnew[i] <= lspnew[i - 1])
      nonmono = TRUE;
  }

  /* *if fix fails, repeat entire LSP vector			 */

  if (nonmono)
  {
    printf("intsynth: repeat entire LSP vector\n");
    printf("intsynth: syndavg = %f  twoerror = %d  frame = %d\n",
	   syndavg, twoerror, frame);
    printf("lspold          lspnew\n");
    for (i = 0; i < no; i++)
    {
      printf("%-14f %-14f \n", lspold[i], lspnew[i]);
      lspnew[i] = lspold[i];
    }
  }

  /* *OPTIONAl (and not finished):				 */
  /* *if large prediction gain then repeat close LSP pair	 */

  lsptopc(lspnew, temp);
  pctorc(temp, rc, no);
  for (i = 1; i < no; i++)
  {
    dlsp[i] = lspnew[i] - lspnew[i - 1];
  }
  dlsp[no] = 0.5 - lspnew[no - 1];

  /* *interpolate lsp's						 */
  for (i = 0; i < nn; i++)
  {
    for (j = 0; j < no; j++)
      lsp[i][j] = w[0][i] * lspold[j] + w[1][i] * lspnew[j];

    /* *OPTIONAL bug checker					 */
    /* *check for monotonically increasing lsp's		 */

    nonmono = FALSE;
    for (j = 1; j < no; j++)
    {
      if (lsp[i][j] <= lsp[i][j - 1])
	nonmono = TRUE;
    }
    if (nonmono)
    {
      printf("intsynth: nonmono LSPs @ frame %d CAN'T HAPPEN\n",
	     frame);
      printf("intsynth: LSPs=");
      for (j = 0; j < no; j++)
	printf("  %f", lsp[i][j]);
      printf("\n");
    }
  }

  /* 		*update lsp history					 */

  for (i = 0; i < no; i++)
    lspold[i] = lspnew[i];
}