www.pudn.com > 200411301125332697.rar > dec_sid.c

/* 
   ITU-T G.729 Annex B     ANSI-C Source Code 
   Version 1.4    Last modified: November 2000 
 
   Copyright (c) 1996, France Telecom, Rockwell International, 
                       Universite de Sherbrooke. 
   All rights reserved. 
*/ 
 
/* 
** 
** File:            "dec_cng.c" 
** 
** Description:     Comfort noise generation 
**                  performed at the decoder part 
** 
*/ 
/**** Fixed point version ***/ 
 
#include  
#include  
#include "typedef.h" 
#include "ld8k.h" 
#include "tab_ld8k.h" 
#include "basic_op.h" 
#include "vad.h" 
#include "dtx.h" 
#include "sid.h" 
#include "tab_dtx.h" 
 
static Word16 cur_gain; 
static Word16 lspSid[M]={ 
  31441,  27566,  21458,  13612,   4663, 
  -4663, -13612, -21458, -27566, -31441}; 
static Word16 sid_gain; 
 
/* 
** 
** Function:        Init_Dec_cng() 
** 
** Description:     Initialize dec_cng static variables 
** 
** 
*/ 
void Init_Dec_cng(void) 
{ 
   
  sid_gain = tab_Sidgain[0]; 
 
  return; 
} 
 
/*-----------------------------------------------------------* 
 * procedure Dec_cng:                                        * 
 *           ~~~~~~~~                                        * 
 *                     Receives frame type                   * 
 *                     0  :  for untransmitted frames        * 
 *                     2  :  for SID frames                  * 
 *                     Decodes SID frames                    * 
 *                     Computes current frame excitation     * 
 *                     Computes current frame LSPs 
 *-----------------------------------------------------------*/ 
void Dec_cng( 
  Word16 past_ftyp,     /* (i)   : past frame type                      */ 
  Word16 sid_sav,       /* (i)   : energy to recover SID gain           */ 
  Word16 sh_sid_sav,    /* (i)   : corresponding scaling factor         */ 
  Word16 *parm,         /* (i)   : coded SID parameters                 */ 
  Word16 *exc,          /* (i/o) : excitation array                     */ 
  Word16 *lsp_old,      /* (i/o) : previous lsp                         */ 
  Word16 *A_t,          /* (o)   : set of interpolated LPC coefficients */ 
  Word16 *seed,         /* (i/o) : random generator seed                */ 
  Word16 freq_prev[MA_NP][M] 
                        /* (i/o) : previous LPS for quantization        */ 
) 
{ 
  Word16 temp, ind; 
  Word16 dif; 
 
  dif = sub(past_ftyp, 1); 
   
  /* SID Frame */ 
  /*************/ 
  if(parm[0] != 0) { 
 
    sid_gain = tab_Sidgain[(int)parm[4]];            
     
    /* Inverse quantization of the LSP */ 
    sid_lsfq_decode(&parm[1], lspSid, freq_prev); 
     
  } 
 
  /* non SID Frame */ 
  /*****************/ 
  else { 
     
    /* Case of 1st SID frame erased : quantize-decode   */ 
    /* energy estimate stored in sid_gain         */ 
    if(dif == 0) { 
      Qua_Sidgain(&sid_sav, &sh_sid_sav, 0, &temp, &ind); 
      sid_gain = tab_Sidgain[(int)ind]; 
    } 
     
  } 
   
  if(dif == 0) { 
    cur_gain = sid_gain; 
  } 
  else { 
    cur_gain = mult_r(cur_gain, A_GAIN0); 
    cur_gain = add(cur_gain, mult_r(sid_gain, A_GAIN1)); 
  } 
  
  Calc_exc_rand(cur_gain, exc, seed, FLAG_DEC); 
 
  /* Interpolate the Lsp vectors */ 
  Int_qlpc(lsp_old, lspSid, A_t); 
  Copy(lspSid, lsp_old, M); 
   
  return; 
} 
 
 
 
/*---------------------------------------------------------------------------* 
 * Function  Init_lsfq_noise                                                 * 
 * ~~~~~~~~~~~~~~~~~~~~~~~~~                                                 * 
 *                                                                           * 
 * -> Initialization of variables for the lsf quantization in the SID        * 
 *                                                                           * 
 *---------------------------------------------------------------------------*/ 
void Init_lsfq_noise(void) 
{ 
  Word16 i, j; 
  Word32 acc0; 
 
  /* initialize the noise_fg */ 
  for (i=0; i<4; i++) 
    Copy(fg[0][i], noise_fg[0][i], M); 
   
  for (i=0; i<4; i++) 
    for (j=0; j 0){ 
      tmpbuf[j-1] = sub(tmpbuf[j-1], k); 
      tmpbuf[j] = add(tmpbuf[j], k); 
    } 
  } 
   
  /* compute the quantized lsf vector */ 
  Lsp_prev_compose(tmpbuf, lsfq, noise_fg[index[0]], freq_prev,  
                   noise_fg_sum[index[0]]); 
   
  /* update the prediction memory */ 
  Lsp_prev_update(tmpbuf, freq_prev); 
   
  /* lsf stability check */ 
  Lsp_stability(lsfq); 
 
  /* convert lsf to lsp */ 
  Lsf_lsp2(lsfq, lspq, M); 
 
}