/***************************************************/ /*! \class BiQuad \brief STK biquad (two-pole, two-zero) filter class. This class implements a two-pole, two-zero digital filter. Methods are provided for creating a resonance or notch in the frequency response while maintaining a constant filter gain. by Perry R. Cook and Gary P. Scavone, 1995--2017. */ /***************************************************/ #include "BiQuad.h" #include namespace stk { BiQuad :: BiQuad() : Filter() { b_.resize( 3, 0.0 ); a_.resize( 3, 0.0 ); b_[0] = 1.0; a_[0] = 1.0; inputs_.resize( 3, 1, 0.0 ); outputs_.resize( 3, 1, 0.0 ); Stk::addSampleRateAlert( this ); } BiQuad :: ~BiQuad() { Stk::removeSampleRateAlert( this ); } void BiQuad :: setCoefficients( StkFloat b0, StkFloat b1, StkFloat b2, StkFloat a1, StkFloat a2, bool clearState ) { b_[0] = b0; b_[1] = b1; b_[2] = b2; a_[1] = a1; a_[2] = a2; if ( clearState ) this->clear(); } void BiQuad :: sampleRateChanged( StkFloat newRate, StkFloat oldRate ) { if ( !ignoreSampleRateChange_ ) { oStream_ << "BiQuad::sampleRateChanged: you may need to recompute filter coefficients!"; handleError( StkError::WARNING ); } } void BiQuad :: setResonance( StkFloat frequency, StkFloat radius, bool normalize ) { #if defined(_STK_DEBUG_) if ( frequency < 0.0 || frequency > 0.5 * Stk::sampleRate() ) { oStream_ << "BiQuad::setResonance: frequency argument (" << frequency << ") is out of range!"; handleError( StkError::WARNING ); return; } if ( radius < 0.0 || radius >= 1.0 ) { oStream_ << "BiQuad::setResonance: radius argument (" << radius << ") is out of range!"; handleError( StkError::WARNING ); return; } #endif a_[2] = radius * radius; a_[1] = -2.0 * radius * cos( TWO_PI * frequency / Stk::sampleRate() ); if ( normalize ) { // Use zeros at +- 1 and normalize the filter peak gain. b_[0] = 0.5 - 0.5 * a_[2]; b_[1] = 0.0; b_[2] = -b_[0]; } } void BiQuad :: setNotch( StkFloat frequency, StkFloat radius ) { #if defined(_STK_DEBUG_) if ( frequency < 0.0 || frequency > 0.5 * Stk::sampleRate() ) { oStream_ << "BiQuad::setNotch: frequency argument (" << frequency << ") is out of range!"; handleError( StkError::WARNING ); return; } if ( radius < 0.0 ) { oStream_ << "BiQuad::setNotch: radius argument (" << radius << ") is negative!"; handleError( StkError::WARNING ); return; } #endif // This method does not attempt to normalize the filter gain. b_[2] = radius * radius; b_[1] = (StkFloat) -2.0 * radius * cos( TWO_PI * (double) frequency / Stk::sampleRate() ); } void BiQuad :: setEqualGainZeroes( void ) { b_[0] = 1.0; b_[1] = 0.0; b_[2] = -1.0; } } // stk namespace