exc_lbc.c

G.723及其附件A以下简称为G.723A 论文首先对语音编码的各种方案进行了比较并对G.723编码方案的特点等进 行了全面的比较然后对语音信号的特征及其分析方法语音信号的形成机理的 数学模型以

            for ( j = 1 ; j < SubFrLen ; j ++ ) {
                Acc0 = L_deposit_h( FltBuf[i+1][j-1] ) ;
                Acc0 = L_mac( Acc0, RezBuf[i], ImpResp[j] ) ;
                FltBuf[i][j] = round( Acc0 ) ;
            }
        }

        /* Compute the cross with the signal */
        for ( i = 0 ; i < ClPitchOrd ; i ++ ) {
            Acc1 = (Word32) 0 ;
            for ( j = 0 ; j < SubFrLen ; j ++ ) {
                Acc0 = L_mult( Tv[j], FltBuf[i][j] ) ;
                Acc1 = L_add( Acc1, L_shr( Acc0, (Word16) 1 ) ) ;
            }
            *lPnt ++ = L_shl( Acc1, (Word16) 1 ) ;
        }

        /* Compute the energies */
        for ( i = 0 ; i < ClPitchOrd ; i ++ ) {
            Acc1 = (Word32) 0 ;
            for ( j = 0 ; j < SubFrLen ; j ++ )
                Acc1 = L_mac( Acc1, FltBuf[i][j], FltBuf[i][j] ) ;
            *lPnt ++ = Acc1 ;
        }

        /* Compute the between crosses */
        for ( i = 1 ; i < ClPitchOrd ; i ++ ) {
            for ( j = 0 ; j < i ; j ++ ) {
                Acc1 = (Word32) 0 ;
                for ( l = 0 ; l < SubFrLen ; l ++ ) {
                    Acc0 = L_mult( FltBuf[i][l], FltBuf[j][l] ) ;
                    Acc1 = L_add( Acc1, L_shr( Acc0, (Word16) 1 ) ) ;
                }
                *lPnt ++ = L_shl( Acc1, (Word16) 2 ) ;
            }
        }
    }


    /* Find Max and normalize */
    Acc1 = (Word32) 0 ;
    for ( i = 0 ; i < Hb*20 ; i ++ ) {
        Acc0 = L_abs(CorBuf[i]) ;
        if ( Acc0 > Acc1 )
            Acc1 = Acc0 ;
    }

    Exp = norm_l( Acc1 ) ;
    /* Convert to shorts */
    for ( i = 0 ; i < Hb*20 ; i ++ ) {
        Acc0 = L_shl( CorBuf[i], Exp ) ;
        CorVct[i] = round( Acc0 ) ;
    }

    /* Test potential error */
    Lag1 = Olp-(Word16)Pstep;
    Lag2 = Olp-(Word16)Pstep+ Hb -(Word16)1;
    off_filt = Test_Err(Lag1, Lag2);
    Bound[0] =  NbFilt085_min + shl(off_filt,2);
    if(Bound[0] > NbFilt085) Bound[0] = NbFilt085;
    Bound[1] =  NbFilt170_min + shl(off_filt,3);
    if(Bound[1] > NbFilt170) Bound[1] = NbFilt170;

    /* Init the search loop */
    Acc1 = (Word32) 0 ;

    for ( k = 0 ; k < (int) Hb ; k ++ ) {

        /* Select Quantization tables */
        l = 0 ;
        if ( WrkRate == Rate63 ){
            if ( (Sfc & (Word16) 1) == (Word16) 0 ) {
                if ( (int)Olp-Pstep+k >= SubFrLen-2 )l ++ ;
            }
            else {
                if ( (int)Olp >= SubFrLen-2 ) l ++ ;
            }
        }
        else {
            l = 1;
        }


        sPnt = AcbkGainTablePtr[l] ;

        for ( i = 0 ; i < (int) Bound[l] ; i ++ ) {

            Acc0 = (Word32) 0 ;
            for ( j = 0 ; j < 20 ; j ++ )
                Acc0 = L_add( Acc0, L_shr( L_mult(CorVct[k*20+j], *sPnt ++),
(Word16) 1 ) ) ;

            if ( Acc0 > Acc1 ) {
                Acc1 = Acc0 ;
                Gid = (Word16) i ;
                Lid = (Word16) k ;
            }
        }
    }

    /* Modify Olp for even sub frames */
    if ( (Sfc & (Word16) 1 ) == (Word16) 0 ) {
        Olp = Olp - (Word16) Pstep + Lid ;
        Lid = (Word16) Pstep ;
    }

    /* Save Gains and Olp */
    (*Line).Sfs[Sfc].AcLg = Lid ;
    (*Line).Sfs[Sfc].AcGn = Gid ;
    (*Line).Olp[shr(Sfc, (Word16) 1)] = Olp ;

    /* Decode the Acbk contribution and subtract it */
    Decod_Acbk( RezBuf, PrevExc, Olp, Lid, Gid ) ;

    for ( i = 0 ; i < SubFrLen ; i ++ ) {
        Acc0 = L_deposit_h( Tv[i] ) ;
        Acc0 = L_shr( Acc0, (Word16) 1 ) ;

        for ( j = 0 ; j <= i ; j ++ )
            Acc0 = L_msu( Acc0, RezBuf[j], ImpResp[i-j] ) ;
        Acc0 = L_shl( Acc0, (Word16) 1 ) ;
        Tv[i] = round( Acc0 ) ;
    }

    return;
}

/*
**
** Function:        Get_Rez()
**
** Description:     Gets delayed contribution from the previous excitation
**                  vector.
**
** Links to text:   Sections 2.14, 2.18 & 3.4
**
** Arguments:
**
**  Word16 *Tv      delayed excitation
**  Word16 *PrevExc Previous excitation vector
**  Word16 Lag      Closed loop pitch lag
**
** Outputs:
**
**  Word16 *Tv      delayed excitation
**
** Return value:    None
**
*/
void  Get_Rez( Word16 *Tv, Word16 *PrevExc, Word16 Lag )
{
    int   i  ;

    for ( i = 0 ; i < ClPitchOrd/2 ; i ++ )
        Tv[i] = PrevExc[PitchMax - (int) Lag - ClPitchOrd/2 + i] ;

    for ( i = 0 ; i < SubFrLen+ClPitchOrd/2 ; i ++ )
        Tv[ClPitchOrd/2+i] = PrevExc[PitchMax - (int)Lag + i%(int)Lag] ;

    return;
}

/*
**
** Function:        Decod_Acbk()
**
** Description:     Computes the adaptive codebook contribution from the previous
**                  excitation vector.
**                  With the gain index, the closed loop pitch lag, the jitter
**                  which when added to this pitch lag gives the actual closed
**                  loop value, and after having selected the proper codebook,
**                  the pitch contribution is reconstructed using the previous
**                  excitation buffer.
**
** Links to text:   Sections 2.14, 2.18 & 3.4
**
** Arguments:
**
**  Word16 *Tv      Reconstructed excitation vector
**  Word16 *PrevExc Previous excitation vector
**  Word16 Olp      closed-loop pitch period
**  Word16 Lid      Jitter around pitch period
**  Word16 Gid      Gain vector index in 5- dimensional
**                      adaptive gain vector codebook
**
** Outputs:
**
**  Word16 *Tv      Reconstructed excitation vector
**
** Return value:    None
**
*/
void  Decod_Acbk( Word16 *Tv, Word16 *PrevExc, Word16 Olp, Word16 Lid,
Word16 Gid )
{
    int   i,j   ;

    Word32   Acc0  ;
    Word16   RezBuf[SubFrLen+ClPitchOrd-1] ;
    Word16  *sPnt ;

    Get_Rez( RezBuf, PrevExc, (Word16)(Olp - (Word16)Pstep + Lid) ) ;

    /* Select Quantization tables */
    i = 0 ;
    if ( WrkRate == Rate63 ) {
        if ( Olp >= (Word16) (SubFrLen-2) ) i ++ ;
    }
    else {
        i = 1;
    }
    sPnt = AcbkGainTablePtr[i] ;

    sPnt += (int)Gid*20 ;

    for ( i = 0 ; i < SubFrLen ; i ++ ) {
        Acc0 = (Word32) 0 ;
        for ( j = 0 ; j < ClPitchOrd ; j ++ )
            Acc0 = L_mac( Acc0, RezBuf[i+j], sPnt[j] ) ;
        Acc0 = L_shl( Acc0, (Word16) 1 ) ;
        Tv[i] = round( Acc0 ) ;
    }

    return;
}

/*
**
** Function:        Comp_Info()
**
** Description:     Voiced/unvoiced classifier.
**                  It is based on a cross correlation maximization over the
**                  last 120 samples of the frame and with an index varying
**                  around the decoded pitch lag (from L-3 to L+3). Then the
**                  prediction gain is tested to declare the frame voiced or
**                  unvoiced.
**
** Links to text:   Section 3.10.2
**
** Arguments:
**
**  Word16 *Buff  decoded excitation
**  Word16 Olp    Decoded pitch lag
**
** Outputs: None
**
** Return value:
**
**      Word16   Estimated pitch value
*/
Word16   Comp_Info( Word16 *Buff, Word16 Olp, Word16 *Gain, Word16 *ShGain)
{
    int   i,j   ;

    Word32   Acc0,Acc1 ;

    Word16   Tenr ;
    Word16   Ccr,Enr ;
    Word16   Indx ;

    /* Normalize the excitation */
    *ShGain = Vec_Norm( Buff, (Word16) (PitchMax+Frame) ) ;

    if ( Olp > (Word16) (PitchMax-3) )
        Olp = (Word16) (PitchMax-3) ;

    Indx = Olp ;

    Acc1 = (Word32) 0 ;

    for ( i = (int)Olp-3 ; i <= (int)Olp+3 ; i ++ ) {

        Acc0 = (Word32) 0 ;
        for ( j = 0 ; j < 2*SubFrLen ; j ++ )
            Acc0 = L_mac( Acc0, Buff[PitchMax+Frame-2*SubFrLen+j],
                                    Buff[PitchMax+Frame-2*SubFrLen-i+j] ) ;

        if ( Acc0 > Acc1 ) {
            Acc1 = Acc0 ;
            Indx = (Word16) i ;
        }
    }

    /* Compute target energy */
    Acc0 = (Word32) 0 ;
    for ( j = 0 ; j < 2*SubFrLen ; j ++ )
        Acc0 = L_mac( Acc0, Buff[PitchMax+Frame-2*SubFrLen+j],
                                    Buff[PitchMax+Frame-2*SubFrLen+j] ) ;
    Tenr = round( Acc0 ) ;
    *Gain = Tenr;

    /* Compute best energy */
    Acc0 = (Word32) 0 ;
    for ( j = 0 ; j < 2*SubFrLen ; j ++ )
        Acc0 = L_mac( Acc0, Buff[PitchMax+Frame-2*SubFrLen-(int)Indx+j],
                            Buff[PitchMax+Frame-2*SubFrLen-(int)Indx+j] ) ;

    Ccr = round( Acc1 ) ;

    if ( Ccr <= (Word16) 0 )
        return (Word16) 0 ;

    Enr = round( Acc0 ) ;

    Acc0 = L_mult( Enr, Tenr ) ;
    Acc0 = L_shr( Acc0, (Word16) 3 ) ;

    Acc0 = L_msu( Acc0, Ccr, Ccr ) ;

    if ( Acc0 < (Word32) 0 )
        return Indx ;
    else
        return (Word16) 0 ;
}

/*
**
** Function:        Regen()
**
** Description:     Performs residual interpolation depending of the frame
**                  classification.
**                  If the frame is previously declared unvoiced, the excitation
**                  is regenerated using a random number generator. Otherwise
**                  a periodic excitation is generated with the period
**                  previously found.
**
** Links to text:   Section 3.10.2
**
** Arguments:
**
**  Word16 *DataBuff  current subframe decoded excitation
**  Word16 *Buff     past decoded excitation
**  Word16 Lag       Decoded pitch lag from previous frame
**  Word16 Gain      Interpolated gain from previous frames
**  Word16 Ecount    Number of erased frames
**  Word16 *Sd       Random number used in unvoiced cases
**
** Outputs:
**
**  Word16 *DataBuff current subframe decoded excitation
**  Word16 *Buff     updated past excitation
**
** Return value:    None
**
*/
void     Regen( Word16 *DataBuff, Word16 *Buff, Word16 Lag, Word16 Gain,
Word16 Ecount, Word16 *Sd )
{
    int   i  ;

    /* Test for clearing */
    if ( Ecount >= (Word16) ErrMaxNum ) {
        for ( i = 0 ; i < Frame ; i ++ )
            DataBuff[i] = (Word16) 0 ;
        for ( i = 0 ; i < Frame+PitchMax ; i ++ )
            Buff[i] = (Word16) 0 ;
    }
    else {
        /* Interpolate accordingly to the voicing estimation */
        if ( Lag != (Word16) 0 ) {
            /* Voiced case */
            for ( i = 0 ; i < Frame ; i ++ )
                Buff[PitchMax+i] = Buff[PitchMax-(int)Lag+i] ;
            for ( i = 0 ; i < Frame ; i ++ )
                DataBuff[i] = Buff[PitchMax+i] = mult( Buff[PitchMax+i],
                            (Word16) 0x6000 ) ;
        }
        else {
            /* Unvoiced case */
            for ( i = 0 ; i < Frame ; i ++ )
                DataBuff[i] = mult( Gain, Rand_lbc( Sd ) ) ;
            /* Clear buffer to reset memory */
            for ( i = 0 ; i < Frame+PitchMax ; i ++ )
                Buff[i] = (Word16) 0 ;
        }
    }

    return;
}

/*
**
** Function:        Comp_Lpf()
**
** Description:     Computes pitch postfilter parameters.
**                  The pitch postfilter lag is first derived (Find_B
**                  and Find_F). Then, the one that gives the largest
**                  contribution is used to calculate the gains (Get_Ind).
**
**
** Links to text:   Section 3.6
**
** Arguments:
**
**  Word16 *Buff    decoded excitation
**  Word16 Olp      Decoded pitch lag
**  Word16 Sfc      Subframe index
**
** Outputs:
**
**
** Return value:
**
**  PFDEF       Pitch postfilter parameters: PF.Gain    Pitch Postfilter gain
**                                           PF.ScGn    Pitch Postfilter scaling gain
**                                           PF.Indx    Pitch postfilter lag
*/
PFDEF Comp_Lpf( Word16 *Buff, Word16 Olp, Word16 Sfc )
{
    int   i,j   ;

    PFDEF Pf    ;
    Word32   Lcr[5] ;
    Word16   Scr[5] ;
    Word16   Bindx, Findx ;
    Word16   Exp ;

    Word32   Acc0,Acc1 ;

    /* Initialize */
    Pf.Indx = (Word16) 0 ;
    Pf.Gain = (Word16) 0 ;
    Pf.ScGn = (Word16) 0x7fff ;

    /* Find both indices */
    Bindx = Find_B( Buff, Olp, Sfc ) ;
    Findx = Find_F( Buff, Olp, Sfc ) ;

    /* Combine the results */
    if ( (Bindx == (Word16) 0) && (Findx == (Word16) 0) )
        return Pf ;

    /* Compute target energy */
    Acc0 = (Word32) 0 ;
    for ( j = 0 ; j < SubFrLen ; j ++ )
        Acc0 = L_mac( Acc0, Buff[PitchMax+(int)Sfc*SubFrLen+j],
                                    Buff[PitchMax+(int)Sfc*SubFrLen+j] ) ;
    Lcr[0] = Acc0 ;

    if ( Bindx != (Word16) 0 ) {
        Acc0 = (Word32) 0 ;
        Acc1 = (Word32) 0 ;
        for ( j = 0 ; j < SubFrLen ; j ++ ) {
            Acc0 = L_mac( Acc0, Buff[PitchMax+(int)Sfc*SubFrLen+j],
                        Buff[PitchMax+(int)Sfc*SubFrLen+(int)Bindx+j] ) ;
            Acc1 = L_mac( Acc1, Buff[PitchMax+(int)Sfc*SubFrLen+(int)Bindx+j],
                        Buff[PitchMax+(int)Sfc*SubFrLen+(int)Bindx+j] ) ;
        }
        Lcr[1] = Acc0 ;
        Lcr[2] = Acc1 ;
    }
    else {
        Lcr[1] = (Word32) 0 ;
        Lcr[2] = (Word32) 0 ;
    }

    if ( Findx != (Word16) 0 ) {
        Acc0 = (Word32) 0 ;
        Acc1 = (Word32) 0 ;
        for ( j = 0 ; j < SubFrLen ; j ++ ) {
            Acc0 = L_mac( Acc0, Buff[PitchMax+(int)Sfc*SubFrLen+j],
                        Buff[PitchMax+(int)Sfc*SubFrLen+(int)Findx+j] ) ;
            Acc1 = L_mac( Acc1, Buff[PitchMax+(int)Sfc*SubFrLen+(int)Findx+j],
                        Buff[PitchMax+(int)Sfc*SubFrLen+(int)Findx+j] ) ;
        }
        Lcr[3] = Acc0 ;
        Lcr[4] = Acc1 ;
    }
    else {
        Lcr[3] = (Word32) 0 ;
        Lcr[4] = (Word32) 0 ;
    }

    /* Normalize and convert to shorts */
    Acc1 = 0L ;
    for ( i = 0 ; i < 5 ; i ++ ) {
        Acc0 = Lcr[i] ;
        if ( Acc0 > Acc1 )
            Acc1 = Acc0 ;
    }

    Exp = norm_l( Acc1 ) ;
    for ( i = 0 ; i < 5 ; i ++ ) {
        Acc0 = L_shl( Lcr[i], Exp ) ;
        Scr[i] = extract_h( Acc0 ) ;
    }