plucked.cpp

Mobile STK for Symbian OS V0.1

/***************************************************/
/*! \class Plucked
    \brief STK plucked string model class.

    This class implements a simple plucked string
    physical model based on the Karplus-Strong
    algorithm.

    This is a digital waveguide model, making its
    use possibly subject to patents held by
    Stanford University, Yamaha, and others.
    There exist at least two patents, assigned to
    Stanford, bearing the names of Karplus and/or
    Strong.

    by Perry R. Cook and Gary P. Scavone, 1995 - 2005.
*/
/***************************************************/

#include "Plucked.h"

Plucked :: Plucked(StkFloat lowestFrequency)
{
  length_ = (unsigned long) (Stk::sampleRate() / lowestFrequency + 1);
  loopGain_ = 0.999;
  delayLine_.setMaximumDelay( length_ );
  delayLine_.setDelay( 0.5 * length_ );
  this->clear();
}

Plucked :: ~Plucked()
{
}

void Plucked :: clear()
{
  delayLine_.clear();
  loopFilter_.clear();
  pickFilter_.clear();
}

void Plucked :: setFrequency(StkFloat frequency)
{
  StkFloat freakency = frequency;
  if ( frequency <= 0.0 ) {
#if !defined(SYMBIAN)
    errorString_ << "Plucked::setFrequency: parameter is less than or equal to zero!";
    handleError( StkError::WARNING );
#endif
    freakency = 220.0;
  }

  // Delay = length - approximate filter delay.
  StkFloat delay = (Stk::sampleRate() / freakency) - 0.5;
  if ( delay <= 0.0 )
    delay = 0.3;
  else if ( delay > length_ )
    delay = length_;
  delayLine_.setDelay( delay );

  loopGain_ = 0.995 + (freakency * 0.000005);
  if ( loopGain_ >= 1.0 ) loopGain_ = 0.99999;
}

void Plucked :: pluck(StkFloat amplitude)
{
  StkFloat gain = amplitude;
  if ( gain > 1.0 ) {
#if !defined(SYMBIAN)
    errorString_ << "Plucked::pluck: amplitude is greater than 1.0 ... setting to 1.0!";
    handleError( StkError::WARNING );
#endif
    gain = 1.0;
  }
  else if ( gain < 0.0 ) {
#if !defined(SYMBIAN)
    errorString_ << "Plucked::pluck: amplitude is < 0.0  ... setting to 0.0!";
    handleError( StkError::WARNING );
#endif
    gain = 0.0;
  }

  pickFilter_.setPole( 0.999 - (gain * 0.15) );
  pickFilter_.setGain( gain * 0.5 );
  for (unsigned long i=0; i<length_; i++)
    // Fill delay with noise additively with current contents.
    delayLine_.tick( 0.6 * delayLine_.lastOut() + pickFilter_.tick( noise_.tick() ) );
}

void Plucked :: noteOn(StkFloat frequency, StkFloat amplitude)
{
  this->setFrequency( frequency );
  this->pluck( amplitude );

#if defined(_STK_DEBUG_)
  errorString_ << "Plucked::NoteOn: frequency = " << frequency << ", amplitude = " << amplitude << ".";
  handleError( StkError::DEBUG_WARNING );
#endif
}

void Plucked :: noteOff(StkFloat amplitude)
{
  loopGain_ = 1.0 - amplitude;
  if ( loopGain_ < 0.0 ) {
#if !defined(SYMBIAN)
    errorString_ << "Plucked::noteOff: amplitude is greater than 1.0 ... setting to 1.0!";
    handleError( StkError::WARNING );
#endif
    loopGain_ = 0.0;
  }
  else if ( loopGain_ > 1.0 ) {
#if !defined(SYMBIAN)
    errorString_ << "Plucked::noteOff: amplitude is < 0.0  ... setting to 0.0!";
    handleError( StkError::WARNING );
#endif
    loopGain_ = (StkFloat) 0.99999;
  }

#if defined(_STK_DEBUG_)
  errorString_ << "Plucked::NoteOff: amplitude = " << amplitude << ".";
  handleError( StkError::DEBUG_WARNING );
#endif
}

StkFloat Plucked :: computeSample()
{
  // Here's the whole inner loop of the instrument!!
  lastOutput_ = delayLine_.tick( loopFilter_.tick( delayLine_.lastOut() * loopGain_ ) ); 
  lastOutput_ *= 3.0;
  return lastOutput_;
}