CDSPFracInterpolator.h

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//$ nobt
//$ nocpp

 
#ifndef R8B_CDSPFRACINTERPOLATOR_INCLUDED
#define R8B_CDSPFRACINTERPOLATOR_INCLUDED
 
#include "CDSPSincFilterGen.h"
#include "CDSPProcessor.h"
 
namespace r8b {
 
#if R8B_FLTTEST
    extern int InterpFilterFracs; 
#endif // R8B_FLTTEST

 
class CDSPFracDelayFilterBank : public R8B_BASECLASS
{
    R8BNOCTOR( CDSPFracDelayFilterBank )
 
    friend class CDSPFracDelayFilterBankCache;
 
public:
 
    CDSPFracDelayFilterBank( const int aFilterFracs, const int aElementSize,
        const int aInterpPoints, const double aReqAtten, const bool aIsThird )
        : InitFilterFracs( aFilterFracs )
        , ElementSize( aElementSize )
        , InterpPoints( aInterpPoints )
        , ReqAtten( aReqAtten )
        , IsThird( aIsThird )
        , Next( R8B_NULL )
        , RefCount( 1 )
    {
        R8BASSERT( ElementSize >= 1 && ElementSize <= 4 );
 
        // Kaiser window function Params, for half and third-band.
 
        const double* const Params = getWinParams( ReqAtten, IsThird,
            FilterLen );
 
        FilterSize = FilterLen * ElementSize;
 
        if( InitFilterFracs == -1 )
        {
            FilterFracs = (int) ceil( pow( 6.4, ReqAtten / 50.0 ));
 
            #if R8B_FLTTEST
 
            if( InterpFilterFracs != -1 )
            {
                FilterFracs = InterpFilterFracs;
            }
 
            #endif // R8B_FLTTEST
        }
        else
        {
            FilterFracs = InitFilterFracs;
        }
 
        Table.alloc( FilterSize * ( FilterFracs + InterpPoints ));
 
        CDSPSincFilterGen sinc;
        sinc.Len2 = FilterLen / 2;
 
        double* p = Table;
        const int pc2 = InterpPoints / 2;
        int i;
 
        for( i = -pc2 + 1; i <= FilterFracs + pc2; i++ )
        {
            sinc.FracDelay = (double) ( FilterFracs - i ) / FilterFracs;
            sinc.initFrac( CDSPSincFilterGen :: wftKaiser, Params, true );
            sinc.generateFrac( p, &CDSPSincFilterGen :: calcWindowKaiser,
                ElementSize );
 
            normalizeFIRFilter( p, FilterLen, 1.0, ElementSize );
            p += FilterSize;
        }
 
        const int TablePos2 = FilterSize;
        const int TablePos3 = FilterSize * 2;
        const int TablePos4 = FilterSize * 3;
        const int TablePos5 = FilterSize * 4;
        const int TablePos6 = FilterSize * 5;
        const int TablePos7 = FilterSize * 6;
        const int TablePos8 = FilterSize * 7;
        double* const TableEnd = Table + ( FilterFracs + 1 ) * FilterSize;
        p = Table;
 
        if( InterpPoints == 8 )
        {
            if( ElementSize == 3 )
            {
                // Calculate 2nd order spline (polynomial) interpolation
                // coefficients using 8 points.
 
                while( p < TableEnd )
                {
                    calcSpline2p8Coeffs( p, p[ 0 ], p[ TablePos2 ],
                        p[ TablePos3 ], p[ TablePos4 ], p[ TablePos5 ],
                        p[ TablePos6 ], p[ TablePos7 ], p[ TablePos8 ]);
 
                    p += ElementSize;
                }
 
                #if defined( R8B_SIMD_ISH )
                    shuffle2_3( Table, TableEnd );
                #endif // SIMD
            }
            else
            if( ElementSize == 4 )
            {
                // Calculate 3rd order spline (polynomial) interpolation
                // coefficients using 8 points.
 
                while( p < TableEnd )
                {
                    calcSpline3p8Coeffs( p, p[ 0 ], p[ TablePos2 ],
                        p[ TablePos3 ], p[ TablePos4 ], p[ TablePos5 ],
                        p[ TablePos6 ], p[ TablePos7 ], p[ TablePos8 ]);
 
                    p += ElementSize;
                }
 
                #if defined( R8B_SIMD_ISH )
                    shuffle2_4( Table, TableEnd );
                #endif // SIMD
            }
        }
        else
        {
            if( ElementSize == 2 )
            {
                // Calculate linear interpolation coefficients.
 
                while( p < TableEnd )
                {
                    p[ 1 ] = p[ TablePos2 ] - p[ 0 ];
                    p += ElementSize;
                }
 
                #if defined( R8B_SIMD_ISH )
                    shuffle2_2( Table, TableEnd );
                #endif // SIMD
            }
        }
 
        R8BCONSOLE( "CDSPFracDelayFilterBank: fracs=%i order=%i taps=%i "
            "att=%.1f third=%i\n", FilterFracs, ElementSize - 1, FilterLen,
            ReqAtten, (int) IsThird );
    }
 
    ~CDSPFracDelayFilterBank()
    {
        delete Next;
    }

 
    static void roundReqAtten( double& att, const bool aIsThird )
    {
        int tmp;
        getWinParams( att, aIsThird, tmp );
    }

 
    int getFilterLen() const
    {
        return( FilterLen );
    }

 
    int getFilterFracs() const
    {
        return( FilterFracs );
    }

 
    const double& operator []( const int i ) const
    {
        R8BASSERT( i >= 0 && i <= FilterFracs );
 
        return( Table[ i * FilterSize ]);
    }

 
    void unref();
 
private:
    int FilterLen; 
    int FilterFracs; 
    int InitFilterFracs; 
    int ElementSize; 
    int InterpPoints; 
    double ReqAtten; 
    bool IsThird; 
    int FilterSize; 
    CFixedBuffer< double > Table; 
    CDSPFracDelayFilterBank* Next; 
    int RefCount; 

 
    static const double* getWinParams( double& att, const bool aIsThird,
        int& fltlen )
    {
        static const int Coeffs2Base = 8;
        static const int Coeffs2Count = 12;
        static const double Coeffs2[ Coeffs2Count ][ 3 ] = {
            { 4.1308468534586913, 1.1752580009977263, 55.5446 }, // 0.0256
            { 4.4241520324148826, 1.8004881791443044, 81.4191 }, // 0.0886
            { 5.2615232289173663, 1.8133318236025469, 96.3392 }, // 0.0481
            { 5.9433751227216174, 1.8730186391986436, 111.1315 }, // 0.0264
            { 6.8308658290513815, 1.8549555110340281, 125.4653 }, // 0.0146
            { 7.6648458290312904, 1.8565766090828464, 139.7379 }, // 0.0081
            { 8.2038728664307605, 1.9269521820570166, 154.0532 }, // 0.0045
            { 8.7865150946655142, 1.9775307667441668, 168.2101 }, // 0.0025
            { 9.5945017884101773, 1.9718456992078597, 182.1076 }, // 0.0014
            { 10.5163141145985240, 1.9504067820201083, 195.5668 }, // 0.0008
            { 10.2382465206362470, 2.1608923446870087, 209.0610 }, // 0.0004
            { 10.9976060250714000, 2.1536533525688935, 222.5010 }, // 0.0003
        };
 
        static const int Coeffs3Base = 6;
        static const int Coeffs3Count = 10;
        static const double Coeffs3[ Coeffs3Count ][ 3 ] = {
            { 3.9888564562781847, 1.5869927184268915, 66.5701 }, // 0.0467
            { 4.6986694038145007, 1.8086068597928262, 86.4715 }, // 0.0136
            { 5.5995071329337822, 1.8930163360942349, 106.1195 }, // 0.0040
            { 6.3627287800257228, 1.9945748322093975, 125.2307 }, // 0.0012
            { 7.4299550711428308, 1.9893400572347544, 144.3469 }, // 0.0004
            { 8.0667715944075642, 2.0928201458699909, 163.4099 }, // 0.0001
            { 8.7469970226288822, 2.1640279784268355, 181.0694 }, // 0.0000
            { 10.0823430069835230, 2.0896678025321922, 199.2880 }, // 0.0000
            { 10.9222206090489510, 2.1221681162186004, 216.6865 }, // 0.0000
            { 21.2017743894772010, 1.1856768080118900, 233.9188 }, // 0.0000
        };
 
        const double* Params;
        int i = 0;
 
        if( aIsThird )
        {
            while( i != Coeffs3Count - 1 && Coeffs3[ i ][ 2 ] < att )
            {
                i++;
            }
 
            Params = &Coeffs3[ i ][ 0 ];
            att = Coeffs3[ i ][ 2 ];
            fltlen = Coeffs3Base + i * 2;
        }
        else
        {
            while( i != Coeffs2Count - 1 && Coeffs2[ i ][ 2 ] < att )
            {
                i++;
            }
 
            Params = &Coeffs2[ i ][ 0 ];
            att = Coeffs2[ i ][ 2 ];
            fltlen = Coeffs2Base + i * 2;
        }
 
        return( Params );
    }

 
    static void shuffle2_2( double* p, double* const pe )
    {
        while( p != pe )
        {
            const double t = p[ 2 ];
            p[ 2 ] = p[ 1 ];
            p[ 1 ] = t;
 
            p += 4;
        }
    }

 
    static void shuffle2_3( double* p, double* const pe )
    {
        while( p != pe )
        {
            const double t1 = p[ 1 ];
            const double t2 = p[ 2 ];
            const double t3 = p[ 3 ];
            const double t4 = p[ 4 ];
            p[ 1 ] = t3;
            p[ 2 ] = t1;
            p[ 3 ] = t4;
            p[ 4 ] = t2;
 
            p += 6;
        }
    }

 
    static void shuffle2_4( double* p, double* const pe )
    {
        while( p != pe )
        {
            const double t1 = p[ 1 ];
            const double t2 = p[ 2 ];
            const double t3 = p[ 3 ];
            const double t4 = p[ 4 ];
            const double t5 = p[ 5 ];
            const double t6 = p[ 6 ];
            p[ 1 ] = t4;
            p[ 2 ] = t1;
            p[ 3 ] = t5;
            p[ 4 ] = t2;
            p[ 5 ] = t6;
            p[ 6 ] = t3;
 
            p += 8;
        }
    }
};

 
class CDSPFracDelayFilterBankCache : public R8B_BASECLASS
{
    R8BNOCTOR( CDSPFracDelayFilterBankCache )
 
    friend class CDSPFracDelayFilterBank;
 
public:
 
    static CDSPFracDelayFilterBank& getFilterBank( const int aFilterFracs,
        const int aElementSize, const int aInterpPoints,
        double ReqAtten, const bool IsThird, const bool IsStatic )
    {
        R8B_EXITDTOR static CPtrKeeper< CDSPFracDelayFilterBank > Objects;
            // The chain of cached objects.
        R8B_EXITDTOR static CPtrKeeper< CDSPFracDelayFilterBank > StaticObjects;
            // The chain of static objects.
        R8B_EXITDTOR static int ObjCount = 0; // The number of objects
            // currently present in the Objects cache.
 
        CDSPFracDelayFilterBank :: roundReqAtten( ReqAtten, IsThird );
 
        R8BSYNC( getStateSync() );
 
        if( IsStatic )
        {
            CDSPFracDelayFilterBank* PrevObj = R8B_NULL;
            CDSPFracDelayFilterBank* CurObj = StaticObjects;
 
            while( CurObj != R8B_NULL )
            {
                if( CurObj -> InitFilterFracs == aFilterFracs &&
                    CurObj -> IsThird == IsThird &&
                    CurObj -> ElementSize == aElementSize &&
                    CurObj -> InterpPoints == aInterpPoints &&
                    CurObj -> ReqAtten == ReqAtten )
                {
                    if( PrevObj != R8B_NULL )
                    {
                        // Move the object to the top of the list.
 
                        PrevObj -> Next = CurObj -> Next;
                        CurObj -> Next = StaticObjects.unkeep();
                        StaticObjects = CurObj;
                    }
 
                    return( *CurObj );
                }
 
                PrevObj = CurObj;
                CurObj = CurObj -> Next;
            }
 
            // Create a new filter bank and build it.
 
            CurObj = new CDSPFracDelayFilterBank( aFilterFracs, aElementSize,
                aInterpPoints, ReqAtten, IsThird );
 
            // Insert the bank at the start of the list.
 
            CurObj -> Next = StaticObjects.unkeep();
            StaticObjects = CurObj;
 
            return( *CurObj );
        }
 
        CDSPFracDelayFilterBank* PrevObj = R8B_NULL;
        CDSPFracDelayFilterBank* CurObj = Objects;
 
        while( CurObj != R8B_NULL )
        {
            if( CurObj -> InitFilterFracs == aFilterFracs &&
                CurObj -> IsThird == IsThird &&
                CurObj -> ElementSize == aElementSize &&
                CurObj -> InterpPoints == aInterpPoints &&
                CurObj -> ReqAtten == ReqAtten )
            {
                break;
            }
 
            if( CurObj -> Next == R8B_NULL &&
                ObjCount >= R8B_FRACBANK_CACHE_MAX )
            {
                if( CurObj -> RefCount == 0 )
                {
                    // Delete the last bank which is not used.
 
                    PrevObj -> Next = R8B_NULL;
                    delete CurObj;
                    ObjCount--;
                }
                else
                {
                    // Move the last bank to the top of the list since it
                    // seems to be in use for a long time.
 
                    PrevObj -> Next = R8B_NULL;
                    CurObj -> Next = Objects.unkeep();
                    Objects = CurObj;
                }
 
                CurObj = R8B_NULL;
                break;
            }
 
            PrevObj = CurObj;
            CurObj = CurObj -> Next;
        }
 
        if( CurObj != R8B_NULL )
        {
            CurObj -> RefCount++;
 
            if( PrevObj == R8B_NULL )
            {
                return( *CurObj );
            }
 
            // Remove the bank from the list temporarily.
 
            PrevObj -> Next = CurObj -> Next;
        }
        else
        {
            // Create a new filter bank (with RefCount == 1) and build it.
 
            CurObj = new CDSPFracDelayFilterBank( aFilterFracs, aElementSize,
                aInterpPoints, ReqAtten, IsThird );
 
            ObjCount++;
        }
 
        // Insert the bank at the start of the list.
 
        CurObj -> Next = Objects.unkeep();
        Objects = CurObj;
 
        return( *CurObj );
    }
 
protected:
 
    static CSyncObject& getStateSync()
    {
        R8B_EXITDTOR static CSyncObject StateSync;
 
        return( StateSync );
    }
};
 
// ---------------------------------------------------------------------------
// CDSPFracDelayFilterBank PUBLIC
// ---------------------------------------------------------------------------
 
inline void CDSPFracDelayFilterBank :: unref()
{
    R8BSYNC( CDSPFracDelayFilterBankCache :: getStateSync() );
 
    RefCount--;
}

 
inline bool findGCD( double l, double s, double& GCD )
{
    int it = 0;
 
    while( ++it < 150 )
    {
        const double r = l - s;
 
        if( r == 0.0 )
        {
            GCD = s;
            return( s > 0.0 );
        }
 
        l = s;
        s = fabs( r );
    }
 
    return( false );
}

 
inline bool getWholeStepping( const double SSampleRate,
    const double DSampleRate, int& ResInStep, int& ResOutStep )
{
    double GCD;
 
    if( !findGCD( SSampleRate, DSampleRate, GCD ))
    {
        return( false );
    }
 
    const double InStep0 = SSampleRate / GCD;
    const double OutStep0 = DSampleRate / GCD;
 
    if( OutStep0 > 1500.0 )
    {
        // Do not allow large output stepping due to low cache
        // performance of large filter banks.
 
        return( false );
    }
 
    ResInStep = (int) InStep0;
    ResOutStep = (int) OutStep0;
 
    // Check for double-to-int precision and overflows.
 
    if( InStep0 != ResInStep || OutStep0 != ResOutStep )
    {
        return( false );
    }
 
    return( true );
}

 
class CDSPFracInterpolator : public CDSPProcessor
{
public:
 
    CDSPFracInterpolator( const double aSrcSampleRate,
        const double aDstSampleRate, const double ReqAtten,
        const bool IsThird, const double PrevLatency )
        : SrcSampleRate( aSrcSampleRate )
        , DstSampleRate( aDstSampleRate )
    #if R8B_FASTTIMING
        , FracStep( aSrcSampleRate / aDstSampleRate )
    #endif // R8B_FASTTIMING
    {
        R8BASSERT( SrcSampleRate > 0.0 );
        R8BASSERT( DstSampleRate > 0.0 );
        R8BASSERT( PrevLatency >= 0.0 );
        R8BASSERT( BufLenBits >= 5 );
 
        InitFracPos = PrevLatency;
        Latency = (int) InitFracPos;
        InitFracPos -= Latency;
 
        R8BASSERT( Latency >= 0 );
 
    #if R8B_FLTTEST
 
        IsWhole = false;
        LatencyFrac = 0.0;
        FilterBank = new CDSPFracDelayFilterBank( -1, 3, 8, ReqAtten,
            IsThird );
 
    #else // R8B_FLTTEST
 
        IsWhole = getWholeStepping( SrcSampleRate, DstSampleRate, InStep,
            OutStep );
 
        if( IsWhole )
        {
            const double spos = InitFracPos * OutStep;
            InitFracPosW = (int) spos;
            LatencyFrac = ( spos - InitFracPosW ) / InStep;
 
            FilterBank = &CDSPFracDelayFilterBankCache :: getFilterBank(
                OutStep, 1, 2, ReqAtten, IsThird, false );
        }
        else
        {
            LatencyFrac = 0.0;
            FilterBank = &CDSPFracDelayFilterBankCache :: getFilterBank(
                -1, 3, 8, ReqAtten, IsThird, true );
        }
 
    #endif // R8B_FLTTEST
 
        FilterLen = FilterBank -> getFilterLen();
        fl2 = FilterLen >> 1;
        fll = fl2 - 1;
        flo = fll + fl2;
        flb = BufLen - fll;
 
        R8BASSERT(( 1 << BufLenBits ) >= FilterLen * 3 );
 
        static const CConvolveFn FltConvFn0[ 13 ] = {
            &CDSPFracInterpolator :: convolve0< 6 >,
            &CDSPFracInterpolator :: convolve0< 8 >,
            &CDSPFracInterpolator :: convolve0< 10 >,
            &CDSPFracInterpolator :: convolve0< 12 >,
            &CDSPFracInterpolator :: convolve0< 14 >,
            &CDSPFracInterpolator :: convolve0< 16 >,
            &CDSPFracInterpolator :: convolve0< 18 >,
            &CDSPFracInterpolator :: convolve0< 20 >,
            &CDSPFracInterpolator :: convolve0< 22 >,
            &CDSPFracInterpolator :: convolve0< 24 >,
            &CDSPFracInterpolator :: convolve0< 26 >,
            &CDSPFracInterpolator :: convolve0< 28 >,
            &CDSPFracInterpolator :: convolve0< 30 >
        };
 
        convfn = ( IsWhole ? FltConvFn0[ fl2 - 3 ] :
            &CDSPFracInterpolator :: convolve2 );
 
        R8BCONSOLE( "CDSPFracInterpolator: src=%.2f dst=%.2f taps=%i "
            "fracs=%i whole=%i third=%i step=%.6f\n", SrcSampleRate,
            DstSampleRate, FilterLen, ( IsWhole ? OutStep :
            FilterBank -> getFilterFracs() ), (int) IsWhole, (int) IsThird,
            aSrcSampleRate / aDstSampleRate );
 
        clear();
    }
 
    virtual ~CDSPFracInterpolator()
    {
    #if R8B_FLTTEST
        delete FilterBank;
    #else // R8B_FLTTEST
        FilterBank -> unref();
    #endif // R8B_FLTTEST
    }
 
    virtual int getInLenBeforeOutPos( const int ReqOutPos ) const
    {
        const int ilat = fl2 + Latency;
 
        if( IsWhole )
        {
            return( ilat + (int) (( InitFracPosW +
                (double) ReqOutPos * InStep ) / OutStep +
                LatencyFrac * InStep / OutStep ));
        }
 
        return( ilat + (int) ( InitFracPos + ReqOutPos * SrcSampleRate /
            DstSampleRate ));
    }
 
    virtual int getLatency() const
    {
        return( 0 );
    }
 
    virtual double getLatencyFrac() const
    {
        return( LatencyFrac );
    }
 
    virtual int getMaxOutLen( const int MaxInLen ) const
    {
        R8BASSERT( MaxInLen >= 0 );
 
        return( (int) ceil( MaxInLen * DstSampleRate / SrcSampleRate ) + 1 );
    }
 
    virtual void clear()
    {
        LatencyLeft = Latency;
        BufLeft = 0;
        WritePos = 0;
        ReadPos = flb; // Set "read" position to account for filter's
            // latency at zero fractional delay.
 
        memset( &Buf[ ReadPos ], 0,
            (size_t) ( BufLen - flb ) * sizeof( Buf[ 0 ]));
 
        if( IsWhole )
        {
            InPosFracW = InitFracPosW;
        }
        else
        {
            InPosFrac = InitFracPos;
 
        #if !R8B_FASTTIMING
            InCounter = 0;
            InPosInt = 0;
            InPosShift = InitFracPos * DstSampleRate / SrcSampleRate;
        #endif // !R8B_FASTTIMING
        }
    }
 
    virtual int process( double* ip, int l, double*& op0 )
    {
        R8BASSERT( l >= 0 );
        R8BASSERT( ip != op0 || l == 0 || SrcSampleRate > DstSampleRate );
 
        if( LatencyLeft != 0 )
        {
            if( LatencyLeft >= l )
            {
                LatencyLeft -= l;
                return( 0 );
            }
 
            l -= LatencyLeft;
            ip += LatencyLeft;
            LatencyLeft = 0;
        }
 
        double* op = op0;
 
        while( l > 0 )
        {
            // Copy new input samples to the ring buffer.
 
            const int b = min( l, min( BufLen - WritePos, flb - BufLeft ));
 
            double* const wp1 = Buf + WritePos;
            memcpy( wp1, ip, (size_t) b * sizeof( wp1[ 0 ]));
            const int ec = flo - WritePos;
 
            if( ec > 0 )
            {
                memcpy( wp1 + BufLen, ip,
                    (size_t) min( b, ec ) * sizeof( wp1[ 0 ]));
            }
 
            ip += b;
            WritePos = ( WritePos + b ) & BufLenMask;
            l -= b;
            BufLeft += b;
 
            // Produce as many output samples as possible.
 
            op = ( *this.*convfn )( op );
        }
 
    #if !R8B_FASTTIMING
 
        if( !IsWhole && InCounter > 1000 )
        {
            // Reset the interpolation position counter to achieve a higher
            // sample-timing precision.
 
            InCounter = 0;
            InPosInt = 0;
            InPosShift = InPosFrac * DstSampleRate / SrcSampleRate;
        }
 
    #endif // !R8B_FASTTIMING
 
        return( (int) ( op - op0 ));
    }
 
private:
    static const int BufLenBits = 8; 
    static const int BufLen = 1 << BufLenBits; 
    static const int BufLenMask = BufLen - 1; 
    double Buf[ BufLen + 29 ]; 
    double SrcSampleRate; 
    double DstSampleRate; 
    double InitFracPos; 
    int InitFracPosW; 
    int Latency; 
    double LatencyFrac; 
    int FilterLen; 
    int fll; 
    int fl2; 
    int flo; 
    int flb; 
    int InStep; 
    int OutStep; 
    int LatencyLeft; 
    int BufLeft; 
    int WritePos; 
    int ReadPos; 
    int InPosFracW; 
    double InPosFrac; 
 
#if R8B_FASTTIMING
    double FracStep; 
#else // R8B_FASTTIMING
    int InCounter; 
    int InPosInt; 
    double InPosShift; 
#endif // R8B_FASTTIMING
 
    CDSPFracDelayFilterBank* FilterBank; 
    bool IsWhole; 
 
    typedef double*( CDSPFracInterpolator ::* CConvolveFn )( double* op ); 
    CConvolveFn convfn; 

 
    template< int fltlen >
    double* convolve0( double* op )
    {
        const CDSPFracDelayFilterBank& fb = *FilterBank;
        const int istep = InStep;
        const int ostep = OutStep;
        int fpos = InPosFracW;
        int rpos = ReadPos;
        int bl = BufLeft - fl2;
 
        while( bl > 0 )
        {
            const double* const ftp = &fb[ fpos ];
            const double* const rp = Buf + rpos;
            int i;
 
        #if defined( R8B_SSE2 ) && !defined( __INTEL_COMPILER )
 
            __m128d s = _mm_setzero_pd();
 
            for( i = 0; i < fltlen; i += 2 )
            {
                const __m128d m = _mm_mul_pd( _mm_load_pd( ftp + i ),
                    _mm_loadu_pd( rp + i ));
 
                s = _mm_add_pd( s, m );
            }
 
            _mm_storel_pd( op, _mm_add_pd( s, _mm_shuffle_pd( s, s, 1 )));
 
        #elif defined( R8B_NEON )
 
            float64x2_t s = vdupq_n_f64( 0.0 );
 
            for( i = 0; i < fltlen; i += 2 )
            {
                s = vmlaq_f64( s, vld1q_f64( ftp + i ), vld1q_f64( rp + i ));
            }
 
            *op = vaddvq_f64( s );
 
        #else // SIMD
 
            double s = 0.0;
 
            for( i = 0; i < fltlen; i++ )
            {
                s += ftp[ i ] * rp[ i ];
            }
 
            *op = s;
 
        #endif // SIMD
 
            op++;
 
            fpos += istep;
            const int PosIncr = fpos / ostep;
            fpos -= PosIncr * ostep;
 
            rpos = ( rpos + PosIncr ) & BufLenMask;
            bl -= PosIncr;
        }
 
        BufLeft = bl + fl2;
        ReadPos = rpos;
        InPosFracW = fpos;
 
        return( op );
    }

 
    double* convolve2( double* op )
    {
        const CDSPFracDelayFilterBank& fb = *FilterBank;
        const int fltlen = FilterLen;
        const double ssr = SrcSampleRate;
        const double dsr = DstSampleRate;
        double fpos = InPosFrac;
        int rpos = ReadPos;
        int bl = BufLeft - fl2;
 
        while( bl > 0 )
        {
            double x = fpos * fb.getFilterFracs();
            const int fti = (int) x; // Function table index.
            x -= fti; // Coefficient for interpolation between adjacent
                // fractional delay filters.
            const double x2d = x * x;
            const double* ftp = &fb[ fti ];
            const double* const rp = Buf + rpos;
            int i;
 
        #if defined( R8B_SSE2 ) && defined( R8B_SIMD_ISH )
 
            const __m128d x1 = _mm_set1_pd( x );
            const __m128d x2 = _mm_set1_pd( x2d );
            __m128d s = _mm_setzero_pd();
 
            for( i = 0; i < fltlen; i += 2 )
            {
                const __m128d ftp2 = _mm_load_pd( ftp + 2 );
                const __m128d xx1 = _mm_mul_pd( ftp2, x1 );
                const __m128d ftp4 = _mm_load_pd( ftp + 4 );
                const __m128d xx2 = _mm_mul_pd( ftp4, x2 );
                const __m128d ftp0 = _mm_load_pd( ftp );
                ftp += 6;
 
                const __m128d rpi = _mm_loadu_pd( rp + i );
                const __m128d xxs = _mm_add_pd( ftp0, _mm_add_pd( xx1, xx2 ));
 
                s = _mm_add_pd( s, _mm_mul_pd( rpi, xxs ));
            }
 
            _mm_storel_pd( op, _mm_add_pd( s, _mm_shuffle_pd( s, s, 1 )));
 
        #elif defined( R8B_NEON ) && defined( R8B_SIMD_ISH )
 
            const float64x2_t x1 = vdupq_n_f64( x );
            const float64x2_t x2 = vdupq_n_f64( x2d );
            float64x2_t s = vdupq_n_f64( 0.0 );
 
            for( i = 0; i < fltlen; i += 2 )
            {
                const float64x2_t ftp2 = vld1q_f64( ftp + 2 );
                const float64x2_t xx1 = vmulq_f64( ftp2, x1 );
                const float64x2_t ftp4 = vld1q_f64( ftp + 4 );
                const float64x2_t xx2 = vmulq_f64( ftp4, x2 );
                const float64x2_t ftp0 = vld1q_f64( ftp );
                ftp += 6;
 
                const float64x2_t rpi = vld1q_f64( rp + i );
                const float64x2_t xxs = vaddq_f64( ftp0,
                    vaddq_f64( xx1, xx2 ));
 
                s = vmlaq_f64( s, rpi, xxs );
            }
 
            *op = vaddvq_f64( s );
 
        #else // SIMD
 
            double s = 0.0;
 
            for( i = 0; i < fltlen; i++ )
            {
                s += ( ftp[ 0 ] + ftp[ 1 ] * x + ftp[ 2 ] * x2d ) * rp[ i ];
                ftp += 3;
            }
 
            *op = s;
 
        #endif // SIMD
 
            op++;
 
        #if R8B_FASTTIMING
 
            fpos += FracStep;
            const int PosIncr = (int) fpos;
            fpos -= PosIncr;
 
        #else // R8B_FASTTIMING
 
            InCounter++;
            const double NextInPos = ( InCounter + InPosShift ) * ssr / dsr;
            const int NextInPosInt = (int) NextInPos;
            const int PosIncr = NextInPosInt - InPosInt;
            InPosInt = NextInPosInt;
            fpos = NextInPos - NextInPosInt;
 
        #endif // R8B_FASTTIMING
 
            rpos = ( rpos + PosIncr ) & BufLenMask;
            bl -= PosIncr;
        }
 
        BufLeft = bl + fl2;
        ReadPos = rpos;
        InPosFrac = fpos;
 
        return( op );
    }
};
 
// ---------------------------------------------------------------------------
 
} // namespace r8b
 
#endif // R8B_CDSPFRACINTERPOLATOR_INCLUDED