Biquad.h

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/**********************************************************************
 
Audacity: A Digital Audio Editor
 
Biquad.h
 
Norm C
Max Maisel
 
***********************************************************************/
 
#ifndef __BIQUAD_H__
#define __BIQUAD_H__
 
#include "MemoryX.h"
 
struct MATH_API Biquad
{
   Biquad();
   void Reset();
   void Process(const float* pfIn, float* pfOut, int iNumSamples);
 
   enum
   {
      B0=0, B1, B2,
      A1=0, A2,
 
      MIN_Order = 1,
      MAX_Order = 10
   };
 
   inline float ProcessOne(float fIn)
   {
      // Biquad must use double for all calculations. Otherwise some
      // filters may have catastrophic rounding errors!
      double fOut = double(fIn) * fNumerCoeffs[B0] +
            fPrevIn * fNumerCoeffs[B1] +
            fPrevPrevIn * fNumerCoeffs[B2] -
            fPrevOut * fDenomCoeffs[A1] -
            fPrevPrevOut * fDenomCoeffs[A2];
      fPrevPrevIn = fPrevIn;
      fPrevIn = fIn;
      fPrevPrevOut = fPrevOut;
      fPrevOut = fOut;
      return fOut;
   }
 
   double fNumerCoeffs[3]; // B0 B1 B2
   double fDenomCoeffs[2]; // A1 A2, A0 == 1.0
   double fPrevIn;
   double fPrevPrevIn;
   double fPrevOut;
   double fPrevPrevOut;
 
   enum kSubTypes
   {
      kLowPass,
      kHighPass,
      nSubTypes
   };
 
   static ArrayOf<Biquad> CalcButterworthFilter(int order, double fn, double fc, int type);
   static ArrayOf<Biquad> CalcChebyshevType1Filter(int order, double fn, double fc, double ripple, int type);
   static ArrayOf<Biquad> CalcChebyshevType2Filter(int order, double fn, double fc, double ripple, int type);
 
   static void ComplexDiv (double fNumerR, double fNumerI, double fDenomR, double fDenomI,
                           double* pfQuotientR, double* pfQuotientI);
   static bool BilinTransform (double fSX, double fSY, double* pfZX, double* pfZY);
   static float Calc2D_DistSqr (double fX1, double fY1, double fX2, double fY2);
 
   static const double s_fChebyCoeffs[MAX_Order][MAX_Order + 1];
   static double ChebyPoly(int Order, double NormFreq);
};
 
#endif