lsp34.c

4.8kcelp语音压缩编码程序

/**************************************************************************
*
* ROUTINE
*               lsp34
*
* FUNCTION
*
*               independent nonuniform scalar line spectral pair quantizer
*
* SYNOPSIS
*               subroutine lsp34(freq, no, bits, findex)
*
*   formal
*
*                       data    I/O
*       name            type    type    function
*       -------------------------------------------------------------------
*       freq		float	i/o	input frequency array/
*					output quantized frequency array
*	no		int	i	order
*	bits		int	i	bit allocation
*	findex		int	o	frequency index array
*
*
***************************************************************************
*
* DESCRIPTION
*
*	Independent (nondifferential) scalar LSP quantization.  Determine
*	LSP quantization by refined sequential quantization.  Because the
*	quantization tables overlap, sequential quantization can produce a
*	nonmonotonic LSP vector.  For nonmonotinic LSPs, the quantization
*	is refined by adjusting the quantization for minimum error by
*	selecting 1 of the following 2 cases:
*	1.  Quantize current LSP to next higher level
*	2.  Quantize previous LSP to the next lower level
*
***************************************************************************
*
* CALLED BY
*
*	celp
*
* CALLS
*
*
**************************************************************************/
#define FSCALE	8000.0
#define mmax(A,B)	((A)>(B)?(A):(B))
#define mmin(A,B)	((A)<(B)?(A):(B))
#include <math.h>
#include "ccsub.h"
static int lsp[MAXNO][16] =
{
  { 100,  170,  225,  250,  280,  340,  420,  500},
  { 210,  235,  265,  295,  325,  360,  400,  440,
    480,  520,  560,  610,  670,  740,  810,  880},
  { 420,  460,  500,  540,  585,  640,  705,  775,
    850,  950, 1050, 1150, 1250, 1350, 1450, 1550},
  { 620,  660,  720,  795,  880,  970, 1080, 1170,
   1270, 1370, 1470, 1570, 1670, 1770, 1870, 1970},
  {1000, 1050, 1130, 1210, 1285, 1350, 1430, 1510,
   1590, 1670, 1750, 1850, 1950, 2050, 2150, 2250},
  {1470, 1570, 1690, 1830, 2000, 2200, 2400, 2600},
  {1800, 1880, 1960, 2100, 2300, 2480, 2700, 2900},
  {2225, 2400, 2525, 2650, 2800, 2950, 3150, 3350},
  {2760, 2880, 3000, 3100, 3200, 3310, 3430, 3550},
  {3190, 3270, 3350, 3420, 3490, 3590, 3710, 3830},
};
lsp34(freq, no, bits, findex)
int no, bits[], findex[];
float freq[];

{
  int levels, i, j;
  float dist, low, errorup, errordn;

  /* *sequentially find closest quantized LSP indicies */

  for (i = 0; i < no; i++)
  {
    freq[i] *= FSCALE;
    levels = (1 << bits[i]) - 1;

    /* *Quantize to nearest output level			 */

    low = dist = fabs(freq[i] - *lsp[i]);
    findex[i] = 0;
    for (j = 1; j <= levels; j++)
    {
      dist = fabs(freq[i] - lsp[i][j]);
      if (dist < low)
      {
	low = dist;
	findex[i] = j;
      }
    }

    /* *adjust quantization if nonmonotonically quantized
       *find minimum quantization error adjustment 		 */


    if (i > 0)
    {
      if (lsp[i][findex[i]] <= lsp[i - 1][findex[i - 1]])
      {
	errorup = fabs(freq[i] - lsp[i][mmin(findex[i] + 1, levels)]) +
	  fabs(freq[i - 1] - lsp[i - 1][findex[i - 1]]);
	errordn = fabs(freq[i] - lsp[i][findex[i]]) +
	  fabs(freq[i - 1] - lsp[i - 1][mmax(findex[i - 1] - 1, 0)]);

	/* *adjust index for minimum error (and preserve monotonicity!) */

	if (errorup < errordn)
        {
          findex[i] = mmin(findex[i] + 1, levels);
	  while (lsp[i][findex[i]] < lsp[i-1][findex[i-1]])
            findex[i] = mmin(findex[i] + 1, levels);
        }
	else if (i == 1)
	  findex[i - 1] = mmax(findex[i - 1] - 1, 0);
	else if (lsp[i - 1][mmax(findex[i - 1] - 1, 0)] >
		 lsp[i - 2][findex[i - 2]])
	  findex[i - 1] = mmax(findex[i - 1] - 1, 0);
	else
        {
	  findex[i] = mmin(findex[i] + 1, levels);
          while (lsp[i][findex[i]] < lsp[i-1][findex[i-1]])
            findex[i] = mmin(findex[i] + 1, levels);
        }
      }
    }
  }

  /* *quantize lsp frequencies using indicies found above */

  for (i = 0; i < no; i++)
    freq[i] = lsp[i][findex[i]] / FSCALE;
}
/**************************************************************************
*
* ROUTINE
*               lspdecode34
*
* FUNCTION
*                
*               independent nonuniform scalar lsp decoder 
*
* SYNOPSIS
*               subroutine lspdecode34(findex,no,freq)
*
*   formal 
*
*                       data    I/O
*       name            type    type    function
*       -------------------------------------------------------------------
*       findex		int	i	lsp frequency index
*	no		int	i	lpc order
*	freq		float	o	lsp quantized frequency
*
***************************************************************************
*
* DESCRIPTION
*	George Kang's tables modified for no preemphasis and bit allocation
*
***************************************************************************
*
* CALLED BY
*
*	celp
*
* CALLS
*	
*
**************************************************************************/
lspdecode34(findex,no,freq)
int findex[], no;
float freq[];
{
  int i;

  /* *** choose appropriate frequency by findex */
  
  for (i = 0; i < no; i++)
  {
    freq[i] = lsp[i][findex[i]]/FSCALE;
  }
}