mirror of
https://github.com/cookiengineer/audacity
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127 lines
2.4 KiB
C++
127 lines
2.4 KiB
C++
/***************************************************/
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/*! \class BiQuad
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\brief STK biquad (two-pole, two-zero) filter class.
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This protected Filter subclass implements a
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two-pole, two-zero digital filter. A method
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is provided for creating a resonance in the
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frequency response while maintaining a constant
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filter gain.
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by Perry R. Cook and Gary P. Scavone, 1995 - 2005.
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*/
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/***************************************************/
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#include "BiQuad.h"
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#include <cmath>
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using namespace Nyq;
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BiQuad :: BiQuad() : Filter()
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{
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std::vector<StkFloat> b(3, 0.0);
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std::vector<StkFloat> a(3, 0.0);
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b[0] = 1.0;
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a[0] = 1.0;
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Filter::setCoefficients( b, a );
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}
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BiQuad :: ~BiQuad()
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{
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}
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void BiQuad :: clear(void)
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{
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Filter::clear();
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}
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void BiQuad :: setB0(StkFloat b0)
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{
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b_[0] = b0;
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}
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void BiQuad :: setB1(StkFloat b1)
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{
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b_[1] = b1;
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}
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void BiQuad :: setB2(StkFloat b2)
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{
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b_[2] = b2;
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}
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void BiQuad :: setA1(StkFloat a1)
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{
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a_[1] = a1;
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}
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void BiQuad :: setA2(StkFloat a2)
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{
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a_[2] = a2;
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}
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void BiQuad :: setResonance(StkFloat frequency, StkFloat radius, bool normalize)
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{
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a_[2] = radius * radius;
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a_[1] = -2.0 * radius * cos(TWO_PI * frequency / Stk::sampleRate());
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if ( normalize ) {
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// Use zeros at +- 1 and normalize the filter peak gain.
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b_[0] = 0.5 - 0.5 * a_[2];
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b_[1] = 0.0;
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b_[2] = -b_[0];
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}
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}
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void BiQuad :: setNotch(StkFloat frequency, StkFloat radius)
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{
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// This method does not attempt to normalize the filter gain.
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b_[2] = radius * radius;
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b_[1] = (StkFloat) -2.0 * radius * cos(TWO_PI * (double) frequency / Stk::sampleRate());
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}
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void BiQuad :: setEqualGainZeroes()
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{
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b_[0] = 1.0;
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b_[1] = 0.0;
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b_[2] = -1.0;
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}
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void BiQuad :: setGain(StkFloat gain)
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{
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Filter::setGain(gain);
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}
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StkFloat BiQuad :: getGain(void) const
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{
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return Filter::getGain();
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}
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StkFloat BiQuad :: lastOut(void) const
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{
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return Filter::lastOut();
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}
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StkFloat BiQuad :: computeSample( StkFloat input )
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{
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inputs_[0] = gain_ * input;
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outputs_[0] = b_[0] * inputs_[0] + b_[1] * inputs_[1] + b_[2] * inputs_[2];
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outputs_[0] -= a_[2] * outputs_[2] + a_[1] * outputs_[1];
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inputs_[2] = inputs_[1];
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inputs_[1] = inputs_[0];
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outputs_[2] = outputs_[1];
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outputs_[1] = outputs_[0];
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return outputs_[0];
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}
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StkFloat BiQuad :: tick( StkFloat input )
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{
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return this->computeSample( input );
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}
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StkFrames& BiQuad :: tick( StkFrames& frames, unsigned int channel )
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{
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return Filter::tick( frames, channel );
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}
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