Version 4.4.3

src/Twang.cpp

@@ -0,0 +1,108 @@
+/***************************************************/
+/*! \class Twang
+    \brief STK enhanced plucked string class.
+
+    This class implements an enhanced plucked-string
+    physical model, a la Jaffe-Smith, Smith,
+    Karjalainen and others.  It includes a comb
+    filter to simulate pluck position.  The tick()
+    function takes an input sample, which is added
+    to the delayline input.  This can be used to
+    implement commuted synthesis (if the input
+    samples are derived from the impulse response of
+    a body filter) or feedback (as in an electric
+    guitar model).
+
+    This is a digital waveguide model, making its
+    use possibly subject to patents held by Stanford
+    University, Yamaha, and others.
+
+    by Perry R. Cook and Gary P. Scavone, 1995-2011.
+*/
+/***************************************************/
+
+#include "Twang.h"
+
+namespace stk {
+
+Twang :: Twang( StkFloat lowestFrequency )
+{
+  if ( lowestFrequency <= 0.0 ) {
+    oStream_ << "Twang::Twang: argument is less than or equal to zero!";
+    handleError( StkError::FUNCTION_ARGUMENT );
+  }
+
+  this->setLowestFrequency( lowestFrequency );
+
+  std::vector<StkFloat> coefficients( 2, 0.5 );
+  loopFilter_.setCoefficients( coefficients );
+
+  lastFrame_.resize( 1, 1, 0.0 );
+
+  loopGain_ = 0.995;
+  pluckPosition_ = 0.4;
+  this->setFrequency( 220.0 );
+}
+
+Twang :: ~Twang( void )
+{
+}
+
+void Twang :: clear( void )
+{
+  delayLine_.clear();
+  combDelay_.clear();
+  loopFilter_.clear();
+  lastFrame_[0] = 0.0;
+}
+
+void Twang :: setLowestFrequency( StkFloat frequency )
+{
+  unsigned long nDelays = (unsigned long) ( Stk::sampleRate() / frequency );
+  delayLine_.setMaximumDelay( nDelays + 1 );
+  combDelay_.setMaximumDelay( nDelays + 1 );
+}
+
+void Twang :: setFrequency( StkFloat frequency )
+{
+#if defined(_STK_DEBUG_)
+  if ( frequency <= 0.0 ) {
+    oStream_ << "Twang::setFrequency: argument is less than or equal to zero!";
+    handleError( StkError::WARNING ); return;
+  }
+#endif
+
+  // Delay = length - filter delay.
+  StkFloat delay = ( Stk::sampleRate() / frequency ) - loopFilter_.phaseDelay( frequency );
+  delayLine_.setDelay( delay );
+
+  this->setLoopGain( loopGain_ );
+
+  // Set the pluck position, which puts zeroes at position * length.
+  combDelay_.setDelay( 0.5 * pluckPosition_ * delay );
+}
+
+void Twang :: setLoopGain( StkFloat loopGain )
+{
+  if ( loopGain < 0.0 || loopGain >= 1.0 ) {
+    oStream_ << "Twang::setLoopGain: parameter is out of range!";
+    handleError( StkError::WARNING ); return;
+  }
+
+  loopGain_ = loopGain;
+  StkFloat gain = loopGain_ + (frequency_ * 0.000005);
+  if ( gain >= 1.0 ) gain = 0.99999;
+  loopFilter_.setGain( gain );
+}
+
+void Twang :: setPluckPosition( StkFloat position )
+{
+  if ( position < 0.0 || position > 1.0 ) {
+    oStream_ << "Twang::setPluckPosition: argument (" << position << ") is out of range!";
+    handleError( StkError::WARNING ); return;
+  }
+
+  pluckPosition_ = position;
+}
+
+} // stk namespace