mirror of
https://github.com/thestk/stk
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104 lines
2.7 KiB
C++
104 lines
2.7 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 class implements a two-pole, two-zero digital filter.
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Methods are provided for creating a resonance or notch in the
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frequency response while maintaining a constant filter gain.
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by Perry R. Cook and Gary P. Scavone, 1995-2012.
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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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namespace stk {
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BiQuad :: BiQuad() : Filter()
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{
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b_.resize( 3, 0.0 );
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a_.resize( 3, 0.0 );
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b_[0] = 1.0;
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a_[0] = 1.0;
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inputs_.resize( 3, 1, 0.0 );
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outputs_.resize( 3, 1, 0.0 );
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Stk::addSampleRateAlert( this );
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}
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BiQuad :: ~BiQuad()
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{
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Stk::removeSampleRateAlert( this );
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}
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void BiQuad :: setCoefficients( StkFloat b0, StkFloat b1, StkFloat b2, StkFloat a1, StkFloat a2, bool clearState )
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{
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b_[0] = b0;
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b_[1] = b1;
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b_[2] = b2;
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a_[1] = a1;
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a_[2] = a2;
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if ( clearState ) this->clear();
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}
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void BiQuad :: sampleRateChanged( StkFloat newRate, StkFloat oldRate )
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{
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if ( !ignoreSampleRateChange_ ) {
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oStream_ << "BiQuad::sampleRateChanged: you may need to recompute filter coefficients!";
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handleError( StkError::WARNING );
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}
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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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#if defined(_STK_DEBUG_)
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if ( frequency < 0.0 || frequency > 0.5 * Stk::sampleRate() ) {
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oStream_ << "BiQuad::setResonance: frequency argument (" << frequency << ") is out of range!";
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handleError( StkError::WARNING ); return;
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}
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if ( radius < 0.0 || radius >= 1.0 ) {
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oStream_ << "BiQuad::setResonance: radius argument (" << radius << ") is out of range!";
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handleError( StkError::WARNING ); return;
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}
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#endif
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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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#if defined(_STK_DEBUG_)
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if ( frequency < 0.0 || frequency > 0.5 * Stk::sampleRate() ) {
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oStream_ << "BiQuad::setNotch: frequency argument (" << frequency << ") is out of range!";
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handleError( StkError::WARNING ); return;
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}
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if ( radius < 0.0 ) {
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oStream_ << "BiQuad::setNotch: radius argument (" << radius << ") is negative!";
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handleError( StkError::WARNING ); return;
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}
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#endif
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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( void )
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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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} // stk namespace
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