#include "IIRFilter.h"
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template <typename SampleType>
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IIRFilter<SampleType>::IIRFilter()
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{
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}
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template <typename SampleType>
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IIRFilter<SampleType>::~IIRFilter()
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{
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}
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template <typename SampleType>
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void IIRFilter<SampleType>::prepare(SampleType sampleRate)
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{
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this->sampleRate = sampleRate;
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calculateCoeffs();
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}
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template <typename SampleType>
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SampleType IIRFilter<SampleType>::processSample(SampleType input)
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{
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auto yn = d0*input + c0*(a0 * input + a1 * xn_1 + a2 * xn_2 - b1 * yn_1 - b2 * yn_2);
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xn_2 = xn_1;
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xn_1 = input;
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yn_2 = yn_1;
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yn_1 = yn;
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return yn;
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}
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template <typename SampleType>
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void IIRFilter<SampleType>::process(SampleType* data, int startSample, int endSample)
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{
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for(int sample = startSample; sample < endSample; ++sample)
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data[sample] = processSample(data[sample]);
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}
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template <typename SampleType>
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void IIRFilter<SampleType>::setCutoff(SampleType newValue)
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{
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if (newValue < 20.0f)
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fc = 20.0f;
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else if (newValue > 20000.0f)
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fc = 20000.0f;
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else
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fc = newValue;
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calculateCoeffs();
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}
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template <typename SampleType>
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SampleType IIRFilter<SampleType>::getCutoff()
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{
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return fc;
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}
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template <typename SampleType>
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void IIRFilter<SampleType>::setFilterType(int type)
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{
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if (type < 0)
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type = 0;
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else if (type > 4)
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type = 4;
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filterType = type;
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calculateCoeffs();
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}
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template <typename SampleType>
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int IIRFilter<SampleType>::getFilterType()
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{
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return filterType;
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}
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template <typename SampleType>
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void IIRFilter<SampleType>::setQ(SampleType newValue)
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{
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SampleType this_q = newValue;
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if (this_q > 20.0)
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this_q = 20.0;
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else if (this_q < 0.2)
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this_q = 0.2;
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Q = this_q;
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calculateCoeffs();
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}
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template <typename SampleType>
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SampleType IIRFilter<SampleType>::getQ()
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{
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return Q;
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}
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template <typename SampleType>
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void IIRFilter<SampleType>::setGain(SampleType newValue)
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{
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notchGain = newValue;
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calculateCoeffs();
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}
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template <typename SampleType>
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SampleType IIRFilter<SampleType>::getGain()
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{
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return notchGain;
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}
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template <typename SampleType>
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void IIRFilter<SampleType>::calculateCoeffs()
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{
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switch (filterType)
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{
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case FilterTypes::LPF : //2nd Order Butterworth LPF
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r = std::sqrt(2);
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C = SampleType(1.0f / tan(PI * fc / (SampleType)this->sampleRate));
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a0 = 1.0f / (1.0f + r * C + C * C);
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a1 = 2 * a0;
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a2 = a0;
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b1 = 2.0f * a0 * (1.0f - C * C);
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b2 = a0 * (1.0f - r * C + C * C);
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c0 = 1.0f;
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d0 = 0.0;
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break;
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case FilterTypes::HPF : //2nd Order Butterworth HPF
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r = std::sqrt(2);
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C = SampleType(tan(PI * fc / (SampleType)this->sampleRate));
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a0 = 1.0f / (1.0f + r * C + C * C);
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a1 = -2 * a0;
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a2 = a0;
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b1 = 2.0f * a0 * (C * C - 1.0f);
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b2 = a0 * (1.0f - r * C + C * C);
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c0 = 1.0f;
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d0 = 0.0;
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break;
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case FilterTypes::Parametric :
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K = tan(PI*fc/SampleType(this->sampleRate));
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V0 = std::pow(10, notchGain / 20);
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D0 = 1 + (K/Q)+K*K;
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e0 = 1 + (K/(V0*Q)) + K*K;
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alpha = 1 + ((V0*K) / Q) + K*K;
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beta = 2*(K*K - 1);
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gamma = 1 - ((V0*K) / Q) + K*K;
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delta = 1 - (K / Q) + K*K;
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heta = 1 - (K / V0*Q) + K*K;
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if(notchGain >= 0)
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{
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//Calcualte boost coefficients
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a0 = alpha/D0;
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a1 = beta/D0;
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a2 = gamma/D0;
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b1 = beta/D0;
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b2 = delta/D0;
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c0 = 1.0f;
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d0 = 0.0f;
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}else
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{
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//Calculate cut coefficients
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a0 = D0/e0;
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a1 = beta/e0;
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a2 = delta/e0;
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b1 = beta/e0;
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b2 = heta/e0;
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c0 = 1.0f;
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d0 = 0.0f;
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}
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/*theta_c = (2 * PI * fc) / SampleType(this->sampleRate);
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u = std::pow(10, notchGain / 20);
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zeta = 4.0 / (1.0 + u);
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beta = 0.5 * (1.0f - (zeta * tan(theta_c / (2.0 * Q)))) / (1.0f + (zeta * tan(theta_c / (2.0 * Q))));
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gamma = (0.5 + beta) * cos(theta_c);
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a0 = 0.5 - beta;
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a1 = 0.0;
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a2 = beta - 0.5;
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b1 = -2.0 * gamma;
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b2 = 2.0 * beta;
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c0 = u - 1.0f;
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d0 = 1.0f;*/
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break;
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}
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}
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template class IIRFilter<float>;
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template class IIRFilter<double>;
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