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Diffstat (limited to 'dfx-library/IIRfilter.h')
| -rwxr-xr-x | dfx-library/IIRfilter.h | 156 |
1 files changed, 156 insertions, 0 deletions
diff --git a/dfx-library/IIRfilter.h b/dfx-library/IIRfilter.h new file mode 100755 index 0000000..8729d36 --- /dev/null +++ b/dfx-library/IIRfilter.h @@ -0,0 +1,156 @@ +#ifndef __IIRfilter +#define __IIRfilter + + +#define PI 3.1415926535897932384626433832795f +#define SHELF_START_IIR 0.333f + +class IIRfilter +{ +public: + IIRfilter(); + ~IIRfilter(); + + void calculateLowpassCoefficients(float cutoff, float samplerate); + void calculateHighpassCoefficients(float cutoff, float samplerate); + void copyCoefficients(IIRfilter *source); + + void reset() + { + prevIn = prevprevIn = prevOut = prevprevOut = prevprevprevOut = currentOut = 0.0f; + } + + float prevIn, prevprevIn, prevOut, prevprevOut, prevprevprevOut, currentOut; + float pOutCoeff, ppOutCoeff, pInCoeff, ppInCoeff, inCoeff; + + +#ifdef USING_HERMITE + void process(float currentIn) +#else + float process(float currentIn) +#endif + { + #ifdef USING_HERMITE + // store 4 samples of history if we're preprocessing for Hermite interpolation + prevprevprevOut = prevprevOut; + #endif + prevprevOut = prevOut; + prevOut = currentOut; + +// currentOut = (currentIn*inCoeff) + (prevIn*pInCoeff) + (prevprevIn*ppInCoeff) +// - (prevOut*pOutCoeff) - (prevprevOut*ppOutCoeff); + currentOut = ((currentIn+prevprevIn)*inCoeff) + (prevIn*pInCoeff) + - (prevOut*pOutCoeff) - (prevprevOut*ppOutCoeff); + + prevprevIn = prevIn; + prevIn = currentIn; + + #ifndef USING_HERMITE + return currentOut; + #endif + } + +#ifdef USING_HERMITE +// start of pre-Hermite-specific functions +// there are 4 versions, 3 of which unroll for loops of 2, 3, & 4 iterations + + void processH1(float currentIn) + { + prevprevprevOut = prevprevOut; + prevprevOut = prevOut; + prevOut = currentOut; + // + currentOut = ( (currentIn+prevprevIn) * inCoeff ) + (prevIn * pInCoeff) + - (prevOut * pOutCoeff) - (prevprevOut * ppOutCoeff); + // + prevprevIn = prevIn; + prevIn = currentIn; + } + + void processH2(float *in, long inPos, long arraySize) + { + float in0 = in[inPos]; + float in1 = in[(inPos+1) % arraySize]; + + prevprevprevOut = prevprevOut; + prevprevOut = prevOut; + prevOut = currentOut; + currentOut = ( (in0+prevprevIn) * inCoeff ) + (prevIn * pInCoeff) + - (prevOut * pOutCoeff) - (prevprevOut * ppOutCoeff); + // + prevprevprevOut = prevprevOut; + prevprevOut = prevOut; + prevOut = currentOut; + currentOut = ( (in1+prevIn) * inCoeff ) + (in0 * pInCoeff) + - (prevOut * pOutCoeff) - (prevprevOut * ppOutCoeff); + // + prevprevIn = in0; + prevIn = in1; + } + + void processH3(float *in, long inPos, long arraySize) + { + float in0 = in[inPos]; + float in1 = in[(inPos+1) % arraySize]; + float in2 = in[(inPos+2) % arraySize]; + + prevprevprevOut = ( (in0+prevprevIn) * inCoeff ) + (prevIn * pInCoeff) + - (currentOut * pOutCoeff) - (prevOut * ppOutCoeff); + prevprevOut = ((in1+prevIn) * inCoeff) + (in0 * pInCoeff) + - (prevprevprevOut * pOutCoeff) - (currentOut * ppOutCoeff); + prevOut = ((in2+in0) * inCoeff) + (in1 * pInCoeff) + - (prevprevOut * pOutCoeff) - (prevprevprevOut * ppOutCoeff); + // + currentOut = prevOut; + prevOut = prevprevOut; + prevprevOut = prevprevprevOut; + prevprevprevOut = currentOut; + // + prevprevIn = in1; + prevIn = in2; + } + + void processH4(float *in, long inPos, long arraySize) + { + float in0 = in[inPos]; + float in1 = in[(inPos+1) % arraySize]; + float in2 = in[(inPos+2) % arraySize]; + float in3 = in[(inPos+3) % arraySize]; + + prevprevprevOut = ( (in0+prevprevIn) * inCoeff ) + (prevIn * pInCoeff) + - (currentOut * pOutCoeff) - (prevOut * ppOutCoeff); + prevprevOut = ((in1+prevIn) * inCoeff) + (in0 * pInCoeff) + - (prevprevprevOut * pOutCoeff) - (currentOut * ppOutCoeff); + prevOut = ((in2+in0) * inCoeff) + (in1 * pInCoeff) + - (prevprevOut * pOutCoeff) - (prevprevprevOut * ppOutCoeff); + currentOut = ((in3+in1) * inCoeff) + (in2 * pInCoeff) + - (prevOut * pOutCoeff) - (prevprevOut * ppOutCoeff); + // + prevprevIn = in2; + prevIn = in3; + } + +#endif +// end of USING_HERMITE batch of functions + +}; // end of IIRfilter class definition + + + +// 4-point Hermite spline interpolation for use with IIR filter output histories +inline float interpolateHermitePostFilter(IIRfilter *filter, double address) +{ + long pos = (long)address; + float posFract = (float) (address - (double)pos); + + float a = ( (3.0f*(filter->prevprevOut-filter->prevOut)) - + filter->prevprevprevOut + filter->currentOut ) * 0.5f; + float b = (2.0f*filter->prevOut) + filter->prevprevprevOut - + (2.5f*filter->prevprevOut) - (filter->currentOut*0.5f); + float c = (filter->prevOut - filter->prevprevprevOut) * 0.5f; + + return (( ((a*posFract)+b) * posFract + c ) * posFract) + filter->prevprevOut; +} + + +#endif
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