/*

Copyright (C) 2016 Apple Inc. All Rights Reserved.

See LICENSE.txt for this sample’s licensing information

*/

//~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

//  Biquad.h

//

//      A generic biquad (two zero - two pole) IIR filter:

//

//          lopass

//          hipass

//          parametric peaking

//          low shelving

//          high shelving

//~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

#ifndef __Biquad

#define __Biquad

#include <math.h>

#include <stdio.h>

class Complex;

class Biquad

{

public:

    Biquad();

    void            Reset();

    static void     GetLopassParams(    float inFreq,

                                        float &a0,

                                        float &a1,

                                        float &a2,

                                        float &b1,

                                        float &b2  );

    // version which also has resonance parameter

    static void     GetLopassParams(    float inFreq,

                                        float inResonance,

                                        float &a0,

                                        float &a1,

                                        float &a2,

                                        float &b1,

                                        float &b2  );

    static void     GetHipassParams(    float inFreq,

                                        float &a0,

                                        float &a1,

                                        float &a2,

                                        float &b1,

                                        float &b2  );

    // version which also has resonance parameter

    static void     GetHipassParams(    float inFreq,

                                        float inResonance,

                                        float &a0,

                                        float &a1,

                                        float &a2,

                                        float &b1,

                                        float &b2  );

    static void     GetLowShelfParams(  float inFreq,

                                        float inDbGain,         // +/- 40dB

                                        float &outA0,

                                        float &outA1,

                                        float &outA2,

                                        float &outB1,

                                        float &outB2);

    static void     GetHighShelfParams( float inFreq,

                                        float inDbGain,         // +/- 40dB

                                        float &outA0,

                                        float &outA1,

                                        float &outA2,

                                        float &outB1,

                                        float &outB2);

    void            GetLopassParams(    float inFreq );

    void            GetLopassParams(    float inFreq, float inResonance );

    void            GetHipassParams(    float inFreq );

    void            GetHipassParams(    float inFreq, float inResonance );

    void            GetLowShelfParams(  float inFreq, float inDbGain );

    void            GetHighShelfParams( float inFreq, float inDbGain );

    void            GetAllpassParams( const Complex &inComplexPole );

    void            GetNotchParams( float inFreq,

                                    float inQ );

    static void     PolarToRect(    float   inTheta,

                                    float   inMag,

                                    float   &outX,

                                    float   &outY   );

    static void     ConjugateRootToQuadCoeffs(  float   inTheta,

                                                float   inMag,

                                                float   &out0,

                                                float   &out1,

                                                float   &out2   );

    static void     RealRootsToQuadCoeffs(  float   inRoot1,

                                            float   inRoot2,

                                            float   &out0,

                                            float   &out1,

                                            float   &out2   );

    void            SetZeroConjugateRoot(   float   inZeroTheta,

                                            float   inZeroMag  );

    void            SetPoleConjugateRoot(   float   inPoleTheta,

                                            float   inPoleMag );

    void            SetZeroConjugateRoot(   const Complex   &inComplexZero  );

    void            SetPoleConjugateRoot(   const Complex   &inComplexPole );

    void            SetZeroRealRoots(   float   inRoot1,

                                        float   inRoot2  );

    void            SetPoleRealRoots(   float   inRoot1,

                                        float   inRoot2  );

    void            Process(    const float *inSourceP,

                                float   *inDestP,

                                int     inFramesToProcess,

                                int     inInputNumberOfChannels,

                                int     inOutputNumberOfChannels

                                );

    inline float Process1(  float   x)

    {

        float y = mA0*x + mA1*mX1 + mA2*mX2 - mB1*mY1 - mB2*mY2;

        mX2 = mX1;

        mX1 = x;

        mY2 = mY1;

        mY1 = y;

        return y;

    }

private:

    float   mA0;

    float   mA1;

    float   mA2;

    float   mB1;

    float   mB2;

    float   mX1;

    float   mX2;

    float   mY1;

    float   mY2;

};

const double kInv1200 = 1.0 / 1200.0;

const double kInv440 = 1.0 / 440.0;

const double kInvLog2 = 1.0 / log(2.0);

inline double   AbsoluteCentsToHertz(double inAbsCents) {return 440.0 * pow(2.0, (inAbsCents - 6900.0) * kInv1200 );};

inline double   HertzToAbsoluteCents(double inHertz) {return 1200.0 * kInvLog2 * log(inHertz * kInv440) + 6900.0;};

#define kMinAbsoluteCents   1200.0 /* 0 is approx 8.175799Hz :: 1200.0 is approx 16Hz */

#define kMaxAbsoluteCents   15023.0 /* approx 48000Hz */

#endif // __Biquad