mirror of https://github.com/bsnes-emu/bsnes.git
46 lines
994 B
C++
46 lines
994 B
C++
#pragma once
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//one-pole first-order IIR filter
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namespace nall { namespace DSP { namespace IIR {
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struct OnePole {
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enum class Type : uint {
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LowPass,
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HighPass,
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};
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inline auto reset(Type type, double cutoffFrequency, double samplingFrequency) -> void;
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inline auto process(double in) -> double; //normalized sample (-1.0 to +1.0)
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private:
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Type type;
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double cutoffFrequency;
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double samplingFrequency;
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double a0, b1; //coefficients
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double z1; //first-order IIR
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};
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auto OnePole::reset(Type type, double cutoffFrequency, double samplingFrequency) -> void {
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this->type = type;
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this->cutoffFrequency = cutoffFrequency;
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this->samplingFrequency = samplingFrequency;
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b1 = exp(-2.0 * Math::Pi * cutoffFrequency / samplingFrequency);
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a0 = 1.0 - b1;
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z1 = 0.0;
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}
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auto OnePole::process(double in) -> double {
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z1 = in * a0 + z1 * b1;
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switch(type) {
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case Type::LowPass: return z1;
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case Type::HighPass: return in - z1;
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default: return 0.0;
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}
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}
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}}}
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