deccng2.c

symbian 系统下的g.723 g.723_24实现, 本源码在 series60 sdk fp2下调试通过

/*
**
** File:            "deccng2.c"
**
** Description:     Comfort noise generation
**                  performed at the decoder part
**
** Functions:       Init_Dec_Cng()
**                  Dec_Cng()
**
**
*/
/*
    ITU-T G.723.1 Floating Point Speech Coder ANSI C Source Code.  Version 5.1F
    copyright (c) 1995, AudioCodes, DSP Group, France Telecom,
    Universite de Sherbrooke.  All rights reserved.

    Floating-point code copyright (c) 1996,
    Intel Corporation and France Telecom (CNET).
    All rights reserved.
*/

#include <stdio.h>
#include <stdlib.h>

#include "typedef2.h"
#include "cst2.h"
#include "tab2.h"
#include "util2.h"
#include "lsp2.h"
#include "exc2.h"
#include "utilcng2.h"
#include "deccng2.h"
#include "decod2.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 = (FLOAT)0.0;
    for (i=0; i<LpcOrder; i++)
        DecCng.LspSid[i] = LspDcTable[i];
    DecCng.RandSeed = 12345;
    return;
}

/*
**
** Function:           Dec_Cng()
**
** Description:        Receives Ftyp
**                     0  :  for untransmitted frames
**                     2  :  for SID frames
**                     Decodes SID frames
**                     Computes current frame excitation
**                     Computes current frame LSPs
**
** Links to text:
**
** Arguments:
**
**  Word16  Ftyp       Type of silence frame
**  LINEDEF *Line      Coded parameters
**  FLOAT   *DataExc   Current frame excitation
**  FLOAT   *QntLpc    Interpolated frame LPC coefficients
**
** Outputs:
**
**  FLOAT   *DataExc
**  FLOAT   *QntLpc
**
** Return value:       None
**
*/
void Dec_Cng(Word16 Ftyp, LINEDEF *Line, FLOAT *DataExc, FLOAT *QntLpc)
{
    Word16 temp;
    int i;

    if (Ftyp == 2) {
        /*
         * SID Frame decoding
         */

        DecCng.SidGain = Dec_SidGain((Word16) Line->Sfs[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, 0);
            DecCng.SidGain = Dec_SidGain(temp);
        }
    }

    if (DecCng.PastFtyp == 1) {
        DecCng.CurGain = DecCng.SidGain;
    }
    else {
        DecCng.CurGain =   (FLOAT) 0.875 * DecCng.CurGain
                         + (FLOAT) 0.125 * DecCng.SidGain;
    }
    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;
}