q_gain2p.c

关于AMR-WB+语音压缩编码的实现代码

/*-------------------------------------------------------------------------*
 * procedure q_gain2_plus                                                  *
 * ~~~~~~~~~~~~~~~~~~~~~~                                                  *
 * Quantization of pitch and codebook gains.                               *
 * The following routines is Q_gains updated for AMR_WB_PLUS.              *
 * MA prediction is removed and MEAN_ENER is now quantized with 2 bits and *
 * transmitted once every ACELP frame to the gains decoder.                *
 * The pitch gain and the code gain are vector quantized and the           *
 * mean-squared weighted error criterion is used in the quantizer search.  *
 *-------------------------------------------------------------------------*/
#include <math.h>
#include <float.h>
#include "../include/amr_plus.h"
#define RANGE         64
int q_gain2_plus(   /* (o)  : index of quantizer                      */
  float code[],     /* (i)  : Innovative code vector                  */
  int lcode,        /* (i)  : Subframe size                           */
  float *gain_pit,  /* (i/o): Pitch gain / Quantized pitch gain       */
  float *gain_code, /* (i/o): code gain / Quantized codebook gain     */
  float *coeff,     /* (i)  : correlations <y1,y1>, -2<xn,y1>,        */
                    /*                <y2,y2>, -2<xn,y2> and 2<y1,y2> */
  float mean_ener,  /* (i)  : mean_ener defined in open-loop (2 bits) */
  float *g0         /* (o)  : 'correction factor'                     */
)
{
  int   i, indice=0, min_ind, size;
  float ener_code, gcode0;
  float dist, dist_min, g_pitch, g_code;
  const float *t_qua_gain, *p;
/*-----------------------------------------------------------------*
 * - Find the initial quantization pitch index                     *
 * - Set gains search range                                        *
 *-----------------------------------------------------------------*/
  t_qua_gain = E_ROM_qua_gain7b;
  p = (const float *) (E_ROM_qua_gain7b + RANGE);       /* pt at 1/4th of table */
  min_ind = 0;
  g_pitch = *gain_pit;
  for (i=0; i<(NB_QUA_GAIN7B-RANGE); i++, p+=2) {
    if (g_pitch > *p) {
      min_ind++;
    }
  }
  size = RANGE;
  min_ind=0;
  size=128;             
  /* innovation energy (without gain) */
  ener_code = 0.01F;
  for(i=0; i<lcode; i++) {
    ener_code += code[i] * code[i];
  }
  ener_code = (float)(10.0 * log10(ener_code /(float)lcode));
  /* predicted codebook gain */
  /* mean energy quantized with 2 bits : 18, 30, 42 or 54 dB */
  gcode0 = mean_ener - ener_code;				
  gcode0 = (float)pow(10.0,gcode0/20.0);   /* predicted gain */
  /* Search for best quantizer */
  dist_min = FLT_MAX;
  p = (const float *) (t_qua_gain + min_ind*2);
  for (i = 0; i<size; i++)
  {
    g_pitch = *p++;                  /* pitch gain */
    g_code = gcode0 * *p++;         /* codebook gain */
    dist = g_pitch*g_pitch * coeff[0]
         + g_pitch         * coeff[1]
         + g_code*g_code   * coeff[2]
         + g_code          * coeff[3]
         + g_pitch*g_code  * coeff[4];				
    if (dist < dist_min)
    {
      dist_min = dist;
      indice = i;
    }
  }
  indice += min_ind;
  *gain_pit  = t_qua_gain[indice*2];
  *gain_code = t_qua_gain[indice*2+1] * gcode0;
  *g0 = t_qua_gain[indice*2+1];
  return indice;
}