www.pudn.com > G.723.1_c.rar > DEC_CNG.C

/* 
** 
** File:            "dec_cng.c" 
** 
** Description:     Comfort noise generation 
**                  performed at the decoder part 
** 
** Functions:       Init_Dec_Cng() 
**                  Dec_Cng() 
** 
** 
*/ 
/* 
    ITU-T G.723 Speech Coder   ANSI-C Source Code     Version 5.00 
    copyright (c) 1995, AudioCodes, DSP Group, France Telecom, 
    Universite de Sherbrooke.  All rights reserved. 
*/ 
 
#include  
#include  
 
#include "typedef.h" 
#include "cst_lbc.h" 
#include "tab_lbc.h" 
#include "util_lbc.h" 
#include "lsp.h" 
#include "exc_lbc.h" 
#include "basop.h" 
#include "util_cng.h" 
#include "dec_cng.h" 
#include "decod.h" 
 
/* Global Variable */ 
DECCNGDEF DecCng; 
 
/* 
** 
** Function:        Init_Dec_Cng() 
** 
** Description:     Initialize Dec_Cng static variables 
** 
** Links to text: 
** 
** Arguments:       None 
** 
** Outputs:         None 
** 
** Return value:    None 
** 
*/ 
void Init_Dec_Cng(void) 
{ 
    int i; 
 
    DecCng.PastFtyp = 1; 
    DecCng.SidGain = 0; 
    for(i=0; iSfs[0].Mamp); 
 
        /* Inverse quantization of the LSP */ 
        Lsp_Inq( DecCng.LspSid, DecStat.PrevLsp, Line->LspId, 0) ; 
    } 
 
    else { 
 
/* 
 * non SID Frame 
 */ 
        if(DecCng.PastFtyp == 1) { 
 
 /* 
  * Case of 1st SID frame erased : quantize-decode 
  * energy estimate stored in DecCng.SidGain 
  * scaling factor in DecCng.CurGain 
  */ 
            temp = Qua_SidGain(&DecCng.SidGain, &DecCng.CurGain, 0); 
            DecCng.SidGain = Dec_SidGain(temp); 
        } 
    } 
 
 
    if(DecCng.PastFtyp == 1) { 
        DecCng.CurGain = DecCng.SidGain; 
    } 
    else { 
        DecCng.CurGain = extract_h(L_add( L_mult(DecCng.CurGain,0x7000), 
                    L_mult(DecCng.SidGain,0x1000) ) ) ; 
    } 
    Calc_Exc_Rand(DecCng.CurGain, DecStat.PrevExc, DataExc, 
                    &DecCng.RandSeed, Line); 
 
    /* Interpolate the Lsp vectors */ 
    Lsp_Int( QntLpc, DecCng.LspSid, DecStat.PrevLsp ) ; 
 
    /* Copy the LSP vector for the next frame */ 
    for ( i = 0 ; i < LpcOrder ; i ++ ) 
        DecStat.PrevLsp[i] = DecCng.LspSid[i] ; 
 
    return; 
}