mirror of
https://github.com/thestk/stk
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75 lines
1.9 KiB
C++
75 lines
1.9 KiB
C++
/***************************************************/
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/*! \class TwoZero
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\brief STK two-zero filter class.
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This class implements a two-zero digital filter. A method is
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provided for creating a "notch" in the frequency response while
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maintaining a constant filter gain.
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by Perry R. Cook and Gary P. Scavone, 1995--2023.
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*/
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/***************************************************/
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#include "TwoZero.h"
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#include <cmath>
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namespace stk {
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TwoZero :: TwoZero( void )
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{
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b_.resize( 3, 0.0 );
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inputs_.resize( 3, 1, 0.0 );
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b_[0] = 1.0;
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Stk::addSampleRateAlert( this );
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}
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TwoZero :: ~TwoZero()
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{
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Stk::removeSampleRateAlert( this );
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}
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void TwoZero :: sampleRateChanged( StkFloat newRate, StkFloat oldRate )
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{
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if ( !ignoreSampleRateChange_ ) {
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oStream_ << "TwoZero::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 TwoZero :: setCoefficients( StkFloat b0, StkFloat b1, StkFloat b2, 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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if ( clearState ) this->clear();
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}
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void TwoZero :: 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_ << "TwoZero::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_ << "TwoZero::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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b_[2] = radius * radius;
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b_[1] = -2.0 * radius * cos(TWO_PI * frequency / Stk::sampleRate());
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// Normalize the filter gain.
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if ( b_[1] > 0.0 ) // Maximum at z = 0.
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b_[0] = 1.0 / ( 1.0 + b_[1] + b_[2] );
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else // Maximum at z = -1.
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b_[0] = 1.0 / ( 1.0 - b_[1] + b_[2] );
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b_[1] *= b_[0];
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b_[2] *= b_[0];
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}
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} // stk namespace
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