q_gn_hf.c

关于AMR-WB+语音压缩编码的实现代码

/*-------------------------------------------------------------------*
 * functions: q_gain_hf()                                            *
 *                                                                   *
 * Coding/Decoding of HF gain parameters with AR prediction.         *
 *                                                                   *
 * The gain vector is quantized using one-stage VQ with 4 elements.  *
 *-------------------------------------------------------------------*/
#include <math.h>
#include <float.h>
#include "../include/amr_plus.h"
void q_gain_hf(
  float *gain,      /* input : gain of 4 subfr */
  float *gain_q,    /* output: quantized gains */
  int *indice       /* output: indices         */
)
{
  int i, k;
  float min_err, distance, gain2[Q_GN_ORDER];
  distance = 1.0e30f;
  for (k=0; k<SIZE_BK_HF; k++)
  {
    for (i=0; i<Q_GN_ORDER; i++) {
      gain2[i] = gain[i] - dico_gain_hf[(k*Q_GN_ORDER)+i] - MEAN_GAIN_HF;
    }
    min_err = 0.0;
    for (i=0; i<Q_GN_ORDER; i++) {
      min_err += gain2[i]*gain2[i];
    }
    if (min_err < distance)
    {
      distance = min_err;
      indice[0] = k;
    }
  }
  for (i=0; i<Q_GN_ORDER; i++) {
    gain_q[i] = dico_gain_hf[(indice[0]*Q_GN_ORDER)+i] + MEAN_GAIN_HF;
  }
  return;
}
/*-------------------------------------------------------------------*
 * routine:   d_gain_hf()                                            *
 *            ~~~~~~~~~                                              *
 * Decoding of gain parameters                                       *
 *-------------------------------------------------------------------*
 *  Arguments:                                                       *
 *    indice[] : indices of the two selected codebook entries        *
 *    gain[]   : quantized gains                                     *
 *-------------------------------------------------------------------*/
#define ALPHA     0.9f
void d_gain_hf(
  int   indice,     /* input:  quantization indices */
  float *gain_q,    /* output: quantized gains      */
  float *past_q,    /* i/o   : past quantized gain (1 word) */
  int   bfi         /* input : Bad frame indicator  */
)
{
  int   i;
  float tmp;
  if(bfi == 0) /* Good frame */
  {
    for (i=0; i<Q_GN_ORDER; i++) {
      gain_q[i] = dico_gain_hf[(indice*Q_GN_ORDER)+i] + MEAN_GAIN_HF;
    }
  }
  else /* bad frame */
  {
    /* use the past gains slightly shifted towards the means */
    *past_q = (ALPHA*(*past_q + 20.0f)) - 20.0f;
    for (i=0; i<Q_GN_ORDER; i++) {
      gain_q[i] = *past_q + MEAN_GAIN_HF;
    }
  }
  tmp = 0.0;
  for (i=0; i<Q_GN_ORDER; i++) {
    tmp += gain_q[i];
  }
  *past_q = 0.25f*tmp - MEAN_GAIN_HF;
  return;
}