exc_lbc.c

一个非常好用的国际标准G。726算法

    Word16   Lag1, Lag2;
    Word16   off_filt;

    /* Init constants */
    Olp = (*Line).Olp[shr(Sfc, (Word16) 1)] ;
    Lid = (Word16) Pstep ;
    Gid = (Word16) 0 ;
    Hb  = (Word16) 3 + (Sfc & (Word16) 1 ) ;

    /* For even frames only */
    if ( (Sfc & (Word16)1) == (Word16) 0 ) {
        if ( Olp == (Word16) PitchMin )
            Olp = add( Olp, (Word16) 1 ) ;
        if ( Olp > (Word16) (PitchMax-5) )
            Olp = (Word16)(PitchMax-5) ;
    }

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

        /* Get residual from the excitation buffer */
        Get_Rez( RezBuf, PrevExc, (Word16)(Olp-(Word16)Pstep+k) ) ;

        /* Filter the last one using the impulse response */
        for ( i = 0 ; i < SubFrLen ; i ++ ) {
            Acc0 = (Word32) 0 ;
            for ( j = 0 ; j <= i ; j ++ )
                Acc0 = L_mac( Acc0, RezBuf[ClPitchOrd-1+j], ImpResp[i-j] ) ;
            FltBuf[ClPitchOrd-1][i] = round( Acc0 ) ;
        }

        /* Update all the others */
        for ( i = ClPitchOrd-2 ; i >= 0 ; i -- ) {
            FltBuf[i][0] = mult_r( RezBuf[i], (Word16) 0x2000 ) ;
            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],