lpc.c

G.723加解码程序

 /*
  * Input a single impulse
  */
    Acc0 = (Word32) 0x04000000L ;

 /*
  * Do for all elements in a subframe
  */
    for ( i = 0 ; i < SubFrLen ; i ++ ) {

 /*
  * Synthesis filter
  */
        for ( j = 0 ; j < LpcOrder ; j ++ )
            Acc0 = L_mac( Acc0, QntLpc[j], FirDl[j] ) ;
        Acc1 = L_shl( Acc0, (Word16) 2 ) ;

 /*
  * Perceptual weighting filter
  */

        /* FIR part */
        for ( j = 0 ; j < LpcOrder ; j ++ )
            Acc0 = L_msu( Acc0, PerLpc[j], FirDl[j] ) ;
                                Acc0 = L_shl( Acc0, (Word16) 1 ) ;
        for ( j = LpcOrder-1 ; j > 0 ; j -- )
            FirDl[j] = FirDl[j-1] ;
        FirDl[0] = round( Acc1 ) ;

        /* Iir part */
        for ( j = 0 ; j < LpcOrder ; j ++ )
            Acc0 = L_mac( Acc0, PerLpc[LpcOrder+j], IirDl[j] ) ;
        for ( j = LpcOrder-1 ; j > 0 ; j -- )
            IirDl[j] = IirDl[j-1] ;
        Acc0 = L_shl( Acc0, (Word16) 2 ) ;
        IirDl[0] = round( Acc0 ) ;
        Temp[PitchMax+i] = IirDl[0] ;

 /*
  * Harmonic noise shaping filter
  */

        Acc0 = L_deposit_h( IirDl[0] ) ;
        Acc0 = L_msu( Acc0, Pw.Gain, Temp[PitchMax-Pw.Indx+i] ) ;
        ImpResp[i] = round( Acc0 ) ;

        Acc0 = (Word32) 0 ;
    }
}

/*
**
** Function:        Sub_Ring()
**
** Description:     Computes the zero-input response of the
**          combined formant perceptual weighting filter,
**          harmonic noise shaping filter, and synthesis
**          filter for a subframe.  Subtracts the
**          zero-input response from the harmonic noise
**          weighted speech vector to produce the target 
**          speech vector.
**
** Links to text:   Section 2.13
**
** Arguments:       
**
**  Word16 Dpnt[]       Harmonic noise weighted vector w[n] (60 words)
**  Word16 QntLpc[]     Quantized LPC coefficients (10 words)
**  Word16 PerLpc[]     Perceptual filter coefficients (20 words)
**  Word16 PrevErr[]    Harmonic noise shaping filter memory (145 words)
**  PWDEF Pw        Harmonic noise shaping filter parameters
**  
** Inputs:
**
**  CodStat.RingFirDl[] Perceptual weighting filter FIR memory from 
**               previous subframe (10 words)
**  CodStat.RingIirDl[] Perceptual weighting filter IIR memory from 
**               previous subframe (10 words)
**
** Outputs:     
**
**  Word16 Dpnt[]       Target vector t[n] (60 words)
**
** Return value:    None
**
*/
void  Sub_Ring( Word16 *Dpnt, Word16 *QntLpc, Word16 *PerLpc, Word16
*PrevErr, PWDEF Pw )
{
    int   i,j   ;
    Word32   Acc0,Acc1 ;

    Word16   FirDl[LpcOrder] ;
    Word16   IirDl[LpcOrder] ;
    Word16   Temp[PitchMax+SubFrLen] ;


 /*
  * Initialize the memory
  */
    for ( i = 0 ; i < PitchMax ; i ++ )
        Temp[i] = PrevErr[i] ;

    for ( i = 0 ; i < LpcOrder ; i ++ ) {
        FirDl[i] = CodStat.RingFirDl[i] ;
        IirDl[i] = CodStat.RingIirDl[i] ;
    }

 /*
  * Do for all elements in a subframe
  */
    for ( i = 0 ; i < SubFrLen ; i ++ ) {

 /*
  * Input zero
  */
        Acc0 = (Word32) 0 ;

 /*
  * Synthesis filter
  */
        for ( j = 0 ; j < LpcOrder ; j ++ )
            Acc0 = L_mac( Acc0, QntLpc[j], FirDl[j] ) ;
        Acc1 = L_shl( Acc0, (Word16) 2 ) ;

 /*
  * Perceptual weighting filter
  */

        /* Fir part */
        for ( j = 0 ; j < LpcOrder ; j ++ )
            Acc0 = L_msu( Acc0, PerLpc[j], FirDl[j] ) ;
        for ( j = LpcOrder-1 ; j > 0 ; j -- )
            FirDl[j] = FirDl[j-1] ;
        FirDl[0] = round( Acc1 ) ;

        /* Iir part */
        for ( j = 0 ; j < LpcOrder ; j ++ )
            Acc0 = L_mac( Acc0, PerLpc[LpcOrder+j], IirDl[j] ) ;
        Acc0 = L_shl( Acc0, (Word16) 2 ) ;
        for ( j = LpcOrder-1 ; j > 0 ; j -- )
            IirDl[j] = IirDl[j-1] ;
        IirDl[0] = round( Acc0 ) ;
        Temp[PitchMax+i] = IirDl[0] ;

 /*
  * Do the harmonic noise shaping filter and subtract the result
  * from the harmonic noise weighted vector.
  */
        Acc0 = L_deposit_h( sub( Dpnt[i], IirDl[0] ) ) ;
        Acc0 = L_mac( Acc0, Pw.Gain, Temp[PitchMax-(int)Pw.Indx+i] ) ;
        Dpnt[i] = round ( Acc0 ) ;
    }
}

/*
**
** Function:        Upd_Ring()
**
** Description:     Updates the memory of the combined formant
**          perceptual weighting filter, harmonic noise
**          shaping filter, and synthesis filter for a
**          subframe.  The update is done by passing the
**          current subframe's excitation through the
**          combined filter.
**
** Links to text:   Section 2.19
**
** Arguments:       
**
**  Word16 Dpnt[]       Decoded excitation for the current subframe e[n] 
**               (60 words)
**  Word16 QntLpc[]     Quantized LPC coefficients (10 words)
**  Word16 PerLpc[]     Perceptual filter coefficients (20 words)
**  Word16 PrevErr[]    Harmonic noise shaping filter memory (145 words)
**  
** Inputs:
**
**  CodStat.RingFirDl[] Perceptual weighting filter FIR memory from 

**               previous subframe (10 words)
**  CodStat.RingIirDl[] Perceptual weighting filter IIR memory from 
**               previous subframe (10 words)
**
** Outputs:     
**
**  Word16 PrevErr[]    Updated harmonic noise shaping filter memory 
**  CodStat.RingFirDl[] Updated perceptual weighting filter FIR memory 
**  CodStat.RingIirDl[] Updated perceptual weighting filter IIR memory 
**
** Return value:    None
**
*/
void  Upd_Ring( Word16 *Dpnt, Word16 *QntLpc, Word16 *PerLpc, Word16
*PrevErr )
{
    int   i,j   ;

    Word32   Acc0,Acc1   ;


 /*
  * Shift the harmonic noise shaping filter memory
  */
    for ( i = SubFrLen ; i < PitchMax ; i ++ )
        PrevErr[i-SubFrLen] = PrevErr[i] ;


 /*
  * Do for all elements in the subframe
  */
    for ( i = 0 ; i < SubFrLen ; i ++ ) {

 /*
  * Input the current subframe's excitation
  */
        Acc0 = L_deposit_h( Dpnt[i] ) ;
        Acc0 = L_shr( Acc0, (Word16) 3 ) ;

 /*
  * Synthesis filter
  */
        for ( j = 0 ; j < LpcOrder ; j ++ )
            Acc0 = L_mac( Acc0, QntLpc[j], CodStat.RingFirDl[j] ) ;
        Acc1 = L_shl( Acc0, (Word16) 2 ) ;

        Dpnt[i] = shl( round( Acc1 ), (Word16) 1 ) ;

 /*
  * Perceptual weighting filter
  */

        /* FIR part */
        for ( j = 0 ; j < LpcOrder ; j ++ )
            Acc0 = L_msu( Acc0, PerLpc[j], CodStat.RingFirDl[j] ) ;

        /* Update FIR memory */
        for ( j = LpcOrder-1 ; j > 0 ; j -- )
            CodStat.RingFirDl[j] = CodStat.RingFirDl[j-1] ;
        CodStat.RingFirDl[0] = round( Acc1 ) ;

        /* IIR part */
        for ( j = 0 ; j < LpcOrder ; j ++ )
            Acc0 = L_mac( Acc0, PerLpc[LpcOrder+j], CodStat.RingIirDl[j] ) ;
        Acc0 = L_shl( Acc0, (Word16) 2 ) ;

        /* Update IIR memory */
        for ( j = LpcOrder-1 ; j > 0 ; j -- )
            CodStat.RingIirDl[j] = CodStat.RingIirDl[j-1] ;
        CodStat.RingIirDl[0] = round( Acc0 ) ;

        /* Update harmonic noise shaping memory */
        PrevErr[PitchMax-SubFrLen+i] = CodStat.RingIirDl[0] ;
    }
}

/*
**
** Function:        Synt()
**
** Description:     Implements the decoder synthesis filter for a
**          subframe.  This is a tenth-order IIR filter.
**
** Links to text:   Section 3.7
**
** Arguments:       
**
**  Word16 Dpnt[]       Pitch-postfiltered excitation for the current
**               subframe ppf[n] (60 words)
**  Word16 Lpc[]        Quantized LPC coefficients (10 words)
**  
** Inputs:
**
**  DecStat.SyntIirDl[] Synthesis filter memory from previous
subframe (10 words)
**
** Outputs:     
**
**  Word16 Dpnt[]       Synthesized speech vector sy[n]
**  DecStat.SyntIirDl[] Updated synthesis filter memory 
**
** Return value:    None
**
*/
void     Synt( Word16 *Dpnt, Word16 *Lpc )
{
    int   i,j   ;

    Word32   Acc0  ;


 /*
  * Do for all elements in the subframe
  */
    for ( i = 0 ; i < SubFrLen ; i ++ ) {

 /*
  * Input the current subframe's excitation
  */
        Acc0 = L_deposit_h( Dpnt[i] ) ;
        Acc0 = L_shr( Acc0, (Word16) 3 ) ;

 /*
  * Synthesis
  */

        /* Filter */
        for ( j = 0 ; j < LpcOrder ; j ++ )
            Acc0 = L_mac( Acc0, Lpc[j], DecStat.SyntIirDl[j] ) ;

        /* Update memory */
        for ( j = LpcOrder-1 ; j > 0 ; j -- )
            DecStat.SyntIirDl[j] = DecStat.SyntIirDl[j-1] ;

        Acc0 = L_shl( Acc0, (Word16) 2 ) ;

        DecStat.SyntIirDl[0] = round( Acc0 ) ;

 /*
  * Scale output if postfilter is off.  (Otherwise output is
  * scaled by the gain scaling unit.)
  */
        if ( UsePf )
            Dpnt[i] = DecStat.SyntIirDl[0] ;
        else
            Dpnt[i] = shl( DecStat.SyntIirDl[0], (Word16) 1 ) ;

    }

}

/*
**
** Function:        Spf()
**
** Description:     Implements the formant postfilter for a
**          subframe.  The formant postfilter is a
**          10-pole, 10-zero ARMA filter followed by a
**          single-tap tilt compensation filter.
**
** Links to text:   Section 3.8
**
** Arguments:
**
**  Word16 Tv[]     Synthesized speech vector sy[n] (60 words)
**  Word16 Lpc[]        Quantized LPC coefficients (10 words)
**
** Inputs:
**
**  DecStat.PostIirDl[] Postfilter IIR memory from previous
subframe (10 words)
**  DecStat.PostFirDl[] Postfilter FIR memory from previous
subframe (10 words)
**  DecStat.Park        Previous value of compensation filter parameter
**
** Outputs:
**
**  Word16 Tv[]     Postfiltered speech vector pf[n] (60 words)
**  DecStat.PostIirDl[] Updated postfilter IIR memory
**  DecStat.PostFirDl[] Updated postfilter FIR memory
**  DecStat.Park        Updated compensation filter parameter
**
** Return value: Input vector energy
**
*/
Word32  Spf( Word16 *Tv, Word16 *Lpc )
{
    int   i,j   ;

    Word32   Acc0,Acc1   ;
    Word32   Sen ;
    Word16   Tmp ;
    Word16   Exp ;

    Word16   FirCoef[LpcOrder] ;
    Word16   IirCoef[LpcOrder] ;

    Word16   TmpVect[SubFrLen] ;

 /*
  * Compute ARMA coefficients.  Compute the jth FIR coefficient by
  * multiplying the jth quantized LPC coefficient by (0.65)^j.
  * Compute the jth IIR coefficient by multiplying the jth quantized
  * LPC coefficient by (0.75)^j.  This emphasizes the formants in
  * the frequency response.
  */
    for ( i = 0 ; i < LpcOrder ; i ++ ) {
        FirCoef[i] = mult_r( Lpc[i], PostFiltZeroTable[i] ) ;
        IirCoef[i] = mult_r( Lpc[i], PostFiltPoleTable[i] ) ;
    }

 /*
  * Normalize the speech vector.
  */
    for ( i = 0 ; i < SubFrLen ; i ++ )
        TmpVect[i] = Tv[i] ;
    Exp = Vec_Norm( TmpVect, (Word16) SubFrLen ) ;

 /*
  * Compute the first two autocorrelation coefficients R[0] and R[1]
  */
    Acc0 = (Word32) 0 ;
    Acc1 = L_mult( TmpVect[0], TmpVect[0] ) ;
    for ( i = 1 ; i < SubFrLen ; i ++ ) {
        Acc0 = L_mac( Acc0, TmpVect[i], TmpVect[i-1] ) ;
        Acc1 = L_mac( Acc1, TmpVect[i], TmpVect[i] ) ;
    }

 /*
  * Scale the energy for the later use.
  */
    Sen = L_shr( Acc1, (Word16)(2*Exp + 4) ) ;

 /*
  * Compute the first-order partial correlation coefficient of the
  * input speech vector.
  */
    Tmp = extract_h( Acc1 ) ;
    if ( Tmp != (Word16) 0 ) {

        /* Compute first parkor */
        Acc0 = L_shr( Acc0, (Word16) 1 ) ;
        Acc1 = Acc0 ;
        Acc0 = L_abs( Acc0 ) ;

        Tmp = div_l( Acc0, Tmp ) ;

        if ( Acc1 < (Word32) 0 )
            Tmp = negate( Tmp ) ;
    }
    else
        Tmp = (Word16) 0 ;

 /*
  * Compute the compensation filter parameter and update the memory
  */
    Acc0 = L_deposit_h( DecStat.Park ) ;
    Acc0 = L_msu( Acc0, DecStat.Park, (Word16) 0x2000 ) ;
    Acc0 = L_mac( Acc0, Tmp, (Word16) 0x2000 ) ;
    DecStat.Park = round( Acc0 ) ;

    Tmp  = mult( DecStat.Park, PreCoef ) ;
    Tmp &= (Word16) 0xfffc ;


 /*
  *  Do for all elements in the subframe
  */
    for ( i = 0 ; i < SubFrLen ; i ++ ) {

 /*
  * Input the speech vector
  */
        Acc0 = L_deposit_h( Tv[i] ) ;
        Acc0 = L_shr( Acc0, (Word16) 2 ) ;

 /*
  * Formant postfilter
  */

        /* FIR part */
        for ( j = 0 ; j < LpcOrder ; j ++ )
            Acc0 = L_msu( Acc0, FirCoef[j], DecStat.PostFirDl[j] ) ;

        /* Update FIR memory */
        for ( j = LpcOrder-1 ; j > 0 ; j -- )
            DecStat.PostFirDl[j] = DecStat.PostFirDl[j-1] ;
        DecStat.PostFirDl[0] = Tv[i] ;

        /* IIR part */
        for ( j = 0 ; j < LpcOrder ; j ++ )
            Acc0 = L_mac( Acc0, IirCoef[j], DecStat.PostIirDl[j] ) ;

        /* Update IIR memory */
        for ( j = LpcOrder-1 ; j > 0 ; j -- )
            DecStat.PostIirDl[j] = DecStat.PostIirDl[j-1] ;

        Acc0 = L_shl( Acc0, (Word16) 2 ) ;
        Acc1 = Acc0 ;

        DecStat.PostIirDl[0] = round( Acc0 ) ;

 /*
  * Compensation filter
  */
        Acc1 = L_mac( Acc1, DecStat.PostIirDl[1], Tmp ) ;

        Tv[i] = round( Acc1 ) ;
    }
    return Sen ;
}