/
Filters.h
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Filters.h
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#pragma once
#ifndef FILTERS_H
#define FILTERS_H
#include <stdint.h>
#include <array>
#include "Util.h"
class BiQuadBase
{
public:
BiQuadBase()
{
bCoef = {{0.0f, 0.0f, 0.0f}};
aCoef = {{0.0f, 0.0f}};
w = {{0.0f, 0.0f}};
}
~BiQuadBase()
{
}
// DF-II impl
void Process(float * samples, const uint32_t n)
{
float out = 0;
for (int s = 0; s < n; ++s)
{
out = bCoef[0] * samples[s] + w[0];
w[0] = bCoef[1] * samples[s] - aCoef[0] * out + w[1];
w[1] = bCoef[2] * samples[s] - aCoef[1] * out;
samples[s] = out;
}
}
float Tick(float s)
{
float out = bCoef[0] * s + w[0];
w[0] = bCoef[1] * s - aCoef[0] * out + w[1];
w[1] = bCoef[2] * s - aCoef[1] * out;
return out;
}
void SetBiquadCoefs(std::array<float, 3> b, std::array<float, 2> a)
{
bCoef = b;
aCoef = a;
}
protected:
std::array<float, 3> bCoef; // b0, b1, b2
std::array<float, 2> aCoef; // a1, a2
std::array<float, 2> w; // delays
};
class RBJFilter : public BiQuadBase
{
public:
enum FilterType
{
LOWPASS,
HIGHPASS,
BANDPASS,
ALLPASS,
NOTCH,
PEAK,
LOW_SHELF,
HIGH_SHELF
};
RBJFilter(FilterType type = FilterType::LOWPASS, float cutoff = 1, float sampleRate = 44100) : sampleRate(sampleRate), t(type)
{
Q = 1;
A = 1;
a = {{0.0f, 0.0f, 0.0f}};
b = {{0.0f, 0.0f, 0.0f}};
SetCutoff(cutoff);
}
~RBJFilter()
{
}
void UpdateCoefficients()
{
cosOmega = cos(omega);
sinOmega = sin(omega);
switch (t)
{
case LOWPASS:
{
alpha = sinOmega / (2.0 * Q);
b[0] = (1 - cosOmega) / 2;
b[1] = 1 - cosOmega;
b[2] = b[0];
a[0] = 1 + alpha;
a[1] = -2 * cosOmega;
a[2] = 1 - alpha;
} break;
case HIGHPASS:
{
alpha = sinOmega / (2.0 * Q);
b[0] = (1 + cosOmega) / 2;
b[1] = -(1 + cosOmega);
b[2] = b[0];
a[0] = 1 + alpha;
a[1] = -2 * cosOmega;
a[2] = 1 - alpha;
} break;
case BANDPASS:
{
alpha = sinOmega * sinhf(logf(2.0) / 2.0 * Q * omega/sinOmega);
b[0] = sinOmega / 2;
b[1] = 0;
b[2] = -b[0];
a[0] = 1 + alpha;
a[1] = -2 * cosOmega;
a[2] = 1 - alpha;
} break;
case ALLPASS:
{
alpha = sinOmega / (2.0 * Q);
b[0] = 1 - alpha;
b[1] = -2 * cosOmega;
b[2] = 1 + alpha;
a[0] = b[2];
a[1] = b[1];
a[2] = b[0];
} break;
case NOTCH:
{
alpha = sinOmega * sinhf(logf(2.0) / 2.0 * Q * omega/sinOmega);
b[0] = 1;
b[1] = -2 * cosOmega;
b[2] = 1;
a[0] = 1 + alpha;
a[1] = b[1];
a[2] = 1 - alpha;
} break;
case PEAK:
{
alpha = sinOmega * sinhf(logf(2.0) / 2.0 * Q * omega/sinOmega);
b[0] = 1 + (alpha * A);
b[1] = -2 * cosOmega;
b[2] = 1 - (alpha * A);
a[0] = 1 + (alpha / A);
a[1] = b[1];
a[2] = 1 - (alpha / A);
} break;
case LOW_SHELF:
{
alpha = sinOmega / 2.0 * sqrt( (A + 1.0 / A) * (1.0 / Q - 1.0) + 2.0);
b[0] = A * ((A + 1) - ((A - 1) * cosOmega) + (2 * sqrtf(A) * alpha));
b[1] = 2 * A * ((A - 1) - ((A + 1) * cosOmega));
b[2] = A * ((A + 1) - ((A - 1) * cosOmega) - (2 * sqrtf(A) * alpha));
a[0] = ((A + 1) + ((A - 1) * cosOmega) + (2 * sqrtf(A) * alpha));
a[1] = -2 * ((A - 1) + ((A + 1) * cosOmega));
a[2] = ((A + 1) + ((A - 1) * cosOmega) - (2 * sqrtf(A) * alpha));
} break;
case HIGH_SHELF:
{
alpha = sinOmega / 2.0 * sqrt( (A + 1.0 / A) * (1.0 / Q - 1.0) + 2.0);
b[0] = A * ((A + 1) + ((A - 1) * cosOmega) + (2 * sqrtf(A) * alpha));
b[1] = -2 * A * ((A - 1) + ((A + 1) * cosOmega));
b[2] = A * ((A + 1) + ((A - 1) * cosOmega) - (2 * sqrtf(A) * alpha));
a[0] = ((A + 1) - ((A - 1) * cosOmega) + (2 * sqrtf(A) * alpha));
a[1] = 2 * ((A - 1) - ((A + 1) * cosOmega));
a[2] = ((A + 1) - ((A - 1) * cosOmega) - (2 * sqrtf(A) * alpha));
} break;
}
// Normalize filter coefficients
float factor = 1.0f / a[0];
std::array<float, 2> aNorm;
std::array<float, 3> bNorm;
aNorm[0] = a[1] * factor;
aNorm[1] = a[2] * factor;
bNorm[0] = b[0] * factor;
bNorm[1] = b[1] * factor;
bNorm[2] = b[2] * factor;
SetBiquadCoefs(bNorm, aNorm);
}
// In Hertz, 0 to Nyquist
void SetCutoff(float c)
{
omega = HZ_TO_RAD(c) / sampleRate;
UpdateCoefficients();
}
float GetCutoff()
{
return omega;
}
// Arbitrary, from 0.01f to ~20
void SetQValue(float q)
{
Q = q;
UpdateCoefficients();
}
float GetQValue()
{
return Q;
}
void SetType(FilterType newType)
{
t = newType;
UpdateCoefficients();
}
FilterType GetType()
{
return t;
}
private:
float sampleRate;
float omega;
float cosOmega;
float sinOmega;
float Q;
float alpha;
float A;
std::array<float, 3> a;
std::array<float, 3> b;
FilterType t;
};
// +/-0.05dB above 9.2Hz @ 44,100Hz
class PinkingFilter
{
double b0, b1, b2, b3, b4, b5, b6;
public:
PinkingFilter() : b0(0), b1(0), b2(0), b3(0), b4(0), b5(0), b6(0) {}
float process(const float s)
{
b0 = 0.99886 * b0 + s * 0.0555179;
b1 = 0.99332 * b1 + s * 0.0750759;
b2 = 0.96900 * b2 + s * 0.1538520;
b3 = 0.86650 * b3 + s * 0.3104856;
b4 = 0.55000 * b4 + s * 0.5329522;
b5 = -0.7616 * b5 - s * 0.0168980;
const double pink = (b0 + b1 + b2 + b3 + b4 + b5 + b6 + (s * 0.5362)) * 0.11;
b6 = s * 0.115926;
return pink;
}
};
class BrowningFilter
{
float l;
public:
BrowningFilter() : l(0) {}
float process(const float s)
{
float brown = (l + (0.02f * s)) / 1.02f;
l = brown;
return brown * 3.5f; // compensate for gain
}
};
#endif