hf_func.c

关于AMR-WB+语音压缩编码的实现代码

#include <float.h>
#include <stdlib.h>
#include <math.h>
#include "../include/amr_plus.h"
/*---------------------------------------------------------------------*
 * routine match_gain_6k4()                                            *
 * ~~~~~~~~~~~~~~~~~~~~~~~~                                            *
 * Find the gain to match amplitude of both filters at 6.4kHz.         *
 * Gain is returned in log domain.                                     *
 *---------------------------------------------------------------------*/
float match_gain_6k4(float *AqLF, float *AqHF)
{
  float tmp, gain;
  float buf[M+L_SUBFR];
  float code[L_SUBFR];
  int i;
  /* generate 1/(1+0.9 z^{-1}) over one subframe (HF signal close to a sinusoid at 6.4 kHz) */
  set_zero(buf, M);
  tmp = 1.0;
  for (i=0; i<L_SUBFR; i++)
  {
    buf[i+M] = tmp;
    tmp *= -0.9f;
  }
  /* apply A(z) from lower-band and 1/A(z) from upper-band */
  E_UTIL_residu(AqLF, buf+M, code, L_SUBFR);
  E_UTIL_synthesisPlus(AqHF, MHF, code, code, L_SUBFR, buf, 0);
  /* compute energy and correction scale factor */
  tmp=0.0;
  for (i=0; i<L_SUBFR; i++) {
    tmp += code[i]*code[i];
  }
  gain = 10.0f * (float)log10(1.0f / tmp);
  return(gain);
}
/*---------------------------------------------------------------------*
 * routine int_gain()                                                  *
 * ~~~~~~~~~~~~~~~~~~                                                  *
 * Find the interpolated gain parameters in every subframes.           *
 *---------------------------------------------------------------------*/
void int_gain(float old_gain, float new_gain, float *gain, int nb_subfr)
{
  float inc, fnew, fold;
  int k;
  inc = 1.0f / (float)nb_subfr;
  fnew = 0.0f;
  for (k=0; k<nb_subfr; k++)
  {
    fold = 1.0f - fnew;
    *gain = (old_gain*fold) + (new_gain*fnew);
    fnew += inc;
    gain++;								
  }  
  return;
}
/*---------------------------------------------------------------------*
 * routine soft_exc_hf()                                               *
 * ~~~~~~~~~~~~~~~~~~~~~                                               *
 * reduce buzziness from excitation.                                   *
 *---------------------------------------------------------------------*/
void soft_exc_hf(float *exc_hf, float *mem)
{
  float tmp, lp_amp;
  int i;
  lp_amp = *mem;
  for (i=0; i<L_SUBFR; i++)
  {
    tmp = (float)fabs(exc_hf[i]);
    lp_amp = 0.98f*lp_amp + 0.02f*tmp;
    tmp = tmp - 2.0f*lp_amp;
    if (tmp < 0.0) {
      tmp = 0.0;
    }
    lp_amp += 0.5f*tmp;
    if (exc_hf[i] >= 0.0) {
      exc_hf[i] -= tmp;
    } else {
      exc_hf[i] += tmp;
    }
  }
  *mem = lp_amp;
  return;
}
/*---------------------------------------------------------------------*
 * routine soft_exc_hf_new()                                           *
 * ~~~~~~~~~~~~~~~~~~~~~                                               *
 * reduce buzziness from excitation.                                   *
 *---------------------------------------------------------------------*/
void soft_exc_hf_new(float *exc_hf, float *mem, int l_frame)
{
  float tmp, lp_amp;
  int i;
  lp_amp = *mem;
  for (i=0; i<l_frame; i++)
  {
    tmp = (float)fabs(exc_hf[i]);
    lp_amp = 0.98f*lp_amp + 0.02f*tmp;
    tmp = tmp - 2.0f*lp_amp;
    if (tmp < 0.0) {
      tmp = 0.0;
    }
    lp_amp += 0.5f*tmp;
    if (exc_hf[i] >= 0.0) {
      exc_hf[i] -= tmp;
    } else {
      exc_hf[i] += tmp;
    }
  }
  *mem = lp_amp;
  return;
}
/*---------------------------------------------------------------------*
 * routine smooth_ener_hf()                                            *
 * ~~~~~~~~~~~~~~~~~~~~~~~~                                            *
 * smooth energy evolution of HF synthesis subframe.                   *
 *---------------------------------------------------------------------*/
void smooth_ener_hf(float *HF, float *threshold)
{
  float tmp, ener;
  int i;
  /* compute energy over subframe */
  ener = 0.0001f;
  for (i=0; i<L_SUBFR; i++) {
    ener += HF[i]*HF[i];
  }
  /* if energy<threshold, add 1.5 dB and saturate to threshold
     else substract 1.5 dB and saturate to threshold */
  tmp = ener;
  if (tmp < *threshold) 
  {
    tmp = tmp*1.414f;
    if (tmp > *threshold) {
      tmp = *threshold;
    }
  }
  else {
    tmp = tmp/1.414f;
    if (tmp < *threshold) {
      tmp = *threshold;
    }
  }
  /* set the threshold for next subframer to the current modified energy */
  *threshold = tmp;
  /* apply correction scale factor to HF signal */
  tmp = (float)sqrt(tmp/ener);
  for (i=0; i<L_SUBFR; i++) {
    HF[i] *= tmp;
  }
  return;
}