FormSwep.cpp

/***************************************************/
/*! \class FormSwep
    \brief STK sweepable formant filter class.

    This class implements a formant (resonance) which can be "swept"
    over time from one frequency setting to another.  It provides
    methods for controlling the sweep rate and target frequency.

    by Perry R. Cook and Gary P. Scavone, 1995--2023.
*/
/***************************************************/

#include "FormSwep.h"
#include <cmath>

namespace stk {

FormSwep :: FormSwep( void )
{
  frequency_ = 0.0;
  radius_ = 0.0;
  targetGain_ = 1.0;
  targetFrequency_ = 0.0;
  targetRadius_ = 0.0;
  deltaGain_ = 0.0;
  deltaFrequency_ = 0.0;
  deltaRadius_ = 0.0;
  sweepState_ = 0.0;
  sweepRate_ = 0.002;
  dirty_ = false;

  b_.resize( 3, 0.0 );
  a_.resize( 3, 0.0 );
  a_[0] = 1.0;
  inputs_.resize( 3, 1, 0.0 );
  outputs_.resize( 3, 1, 0.0 );

  Stk::addSampleRateAlert( this );
}

FormSwep :: ~FormSwep()
{
  Stk::removeSampleRateAlert( this );
}

void FormSwep :: sampleRateChanged( StkFloat newRate, StkFloat oldRate )
{
  if ( !ignoreSampleRateChange_ ) {
    oStream_ << "FormSwep::sampleRateChanged: you may need to recompute filter coefficients!";
    handleError( StkError::WARNING );
  }
}

void FormSwep :: setResonance( StkFloat frequency, StkFloat radius )
{
#if defined(_STK_DEBUG_)
  if ( frequency < 0.0 || frequency > 0.5 * Stk::sampleRate() ) {
    oStream_ << "FormSwep::setResonance: frequency argument (" << frequency << ") is out of range!";
    handleError( StkError::WARNING ); return;
  }
  if ( radius < 0.0 || radius >= 1.0 ) {
    oStream_ << "FormSwep::setResonance: radius argument (" << radius << ") is out of range!";
    handleError( StkError::WARNING ); return;
  }
#endif

  radius_ = radius;
  frequency_ = frequency;

  a_[2] = radius * radius;
  a_[1] = -2.0 * radius * cos( TWO_PI * frequency / Stk::sampleRate() );

  // 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 FormSwep :: setStates( StkFloat frequency, StkFloat radius, StkFloat gain )
{
  dirty_ = false;

  if ( frequency_ != frequency || radius_ != radius )
    this->setResonance( frequency, radius );

  gain_ = gain;
  targetFrequency_ = frequency;
  targetRadius_ = radius;
  targetGain_ = gain;
}

void FormSwep :: setTargets( StkFloat frequency, StkFloat radius, StkFloat gain )
{
  if ( frequency < 0.0 || frequency > 0.5 * Stk::sampleRate() ) {
    oStream_ << "FormSwep::setTargets: frequency argument (" << frequency << ") is out of range!";
    handleError( StkError::WARNING ); return;
  }
  if ( radius < 0.0 || radius >= 1.0 ) {
    oStream_ << "FormSwep::setTargets: radius argument (" << radius << ") is out of range!";
    handleError( StkError::WARNING ); return;
  }

  dirty_ = true;
  startFrequency_ = frequency_;
  startRadius_ = radius_;
  startGain_ = gain_;
  targetFrequency_ = frequency;
  targetRadius_ = radius;
  targetGain_ = gain;
  deltaFrequency_ = frequency - frequency_;
  deltaRadius_ = radius - radius_;
  deltaGain_ = gain - gain_;
  sweepState_ = 0.0;
}

void FormSwep :: setSweepRate( StkFloat rate )
{
  if ( rate < 0.0 || rate > 1.0 ) {
    oStream_ << "FormSwep::setSweepRate: argument (" << rate << ") is out of range!";
    handleError( StkError::WARNING ); return;
  }

  sweepRate_ = rate;
}

void FormSwep :: setSweepTime( StkFloat time )
{
  if ( time <= 0.0 ) {
    oStream_ << "FormSwep::setSweepTime: argument (" << time << ") must be > 0.0!";
    handleError( StkError::WARNING ); return;
  }

  this->setSweepRate( 1.0 / ( time * Stk::sampleRate() ) );
}

} // stk namespace