Version 4.0

src/StifKarp.cpp

@@ -0,0 +1,227 @@
+/***************************************************/
+/*! \class StifKarp
+    \brief STK plucked stiff string instrument.
+
+    This class implements a simple plucked string
+    algorithm (Karplus Strong) with enhancements
+    (Jaffe-Smith, Smith, and others), including
+    string stiffness and pluck position controls.
+    The stiffness is modeled with allpass filters.
+
+    This is a digital waveguide model, making its
+    use possibly subject to patents held by
+    Stanford University, Yamaha, and others.
+
+    Control Change Numbers:
+       - Pickup Position = 4
+       - String Sustain = 11
+       - String Stretch = 1
+
+    by Perry R. Cook and Gary P. Scavone, 1995 - 2002.
+*/
+/***************************************************/
+
+#include "StifKarp.h"
+#include "SKINI.msg"
+#include <string.h>
+#include <math.h>
+
+StifKarp :: StifKarp(MY_FLOAT lowestFrequency)
+{
+  length = (long) (Stk::sampleRate() / lowestFrequency + 1);
+  delayLine = new DelayA(0.5 * length, length);
+  combDelay = new DelayL( 0.2 * length, length);
+
+  filter = new OneZero();
+  noise = new Noise();
+  biQuad[0] = new BiQuad();
+  biQuad[1] = new BiQuad();
+  biQuad[2] = new BiQuad();
+  biQuad[3] = new BiQuad();
+
+  pluckAmplitude = 0.3;
+  pickupPosition = (MY_FLOAT) 0.4;
+  lastFrequency = lowestFrequency * 2.0;
+  lastLength = length * 0.5;
+  stretching = 0.9999;
+  baseLoopGain = 0.995;
+  loopGain = 0.999;
+
+  clear();
+}
+
+StifKarp :: ~StifKarp()
+{
+  delete delayLine;
+  delete combDelay;
+  delete filter;
+  delete noise;
+  delete biQuad[0];
+  delete biQuad[1];
+  delete biQuad[2];
+  delete biQuad[3];
+}
+
+void StifKarp :: clear()
+{
+  delayLine->clear();
+  combDelay->clear();
+  filter->clear();
+}
+
+void StifKarp :: setFrequency(MY_FLOAT frequency)
+{
+  lastFrequency = frequency; 
+  if ( frequency <= 0.0 ) {
+    cerr << "StifKarp: setFrequency parameter is less than or equal to zero!" << endl;
+    lastFrequency = 220.0;
+  }
+
+  lastLength = Stk::sampleRate() / lastFrequency;
+  MY_FLOAT delay = lastLength - 0.5;
+  if (delay <= 0.0) delay = 0.3;
+  else if (delay > length) delay = length;
+  delayLine->setDelay( delay );
+
+  loopGain = baseLoopGain + (frequency * (MY_FLOAT) 0.000005);
+  if (loopGain >= 1.0) loopGain = (MY_FLOAT) 0.99999;
+
+  setStretch(stretching);
+
+  combDelay->setDelay((MY_FLOAT) 0.5 * pickupPosition * lastLength); 
+}
+
+void StifKarp :: setStretch(MY_FLOAT stretch)
+{
+  stretching = stretch;
+  MY_FLOAT coefficient;
+  MY_FLOAT freq = lastFrequency * 2.0;
+  MY_FLOAT dFreq = ( (0.5 * Stk::sampleRate()) - freq ) * 0.25;
+  MY_FLOAT temp = 0.5 + (stretch * 0.5);
+  if (temp > 0.9999) temp = 0.9999;
+  for (int i=0; i<4; i++)	{
+    coefficient = temp * temp;
+    biQuad[i]->setA2( coefficient );
+    biQuad[i]->setB0( coefficient );
+    biQuad[i]->setB2( 1.0 );
+
+    coefficient = -2.0 * temp * cos(TWO_PI * freq / Stk::sampleRate());
+    biQuad[i]->setA1( coefficient );
+    biQuad[i]->setB1( coefficient );
+
+    freq += dFreq;
+  }
+}
+
+void StifKarp :: setPickupPosition(MY_FLOAT position) {
+  pickupPosition = position;
+  if ( position < 0.0 ) {
+    cerr << "StifKarp: setPickupPosition parameter is less than zero!" << endl;
+    pickupPosition = 0.0;
+  }
+  else if ( position > 1.0 ) {
+    cerr << "StifKarp: setPickupPosition parameter is greater than 1.0!" << endl;
+    pickupPosition = 1.0;
+  }
+
+  // Set the pick position, which puts zeroes at position * length.
+  combDelay->setDelay(0.5 * pickupPosition * lastLength); 
+}
+
+void StifKarp :: setBaseLoopGain(MY_FLOAT aGain)
+{
+  baseLoopGain = aGain;
+  loopGain = baseLoopGain + (lastFrequency * 0.000005);
+  if ( loopGain > 0.99999 ) loopGain = (MY_FLOAT) 0.99999;
+}
+
+void StifKarp :: pluck(MY_FLOAT amplitude)
+{
+  MY_FLOAT gain = amplitude;
+  if ( gain > 1.0 ) {
+    cerr << "StifKarp: pluck amplitude greater than 1.0!" << endl;
+    gain = 1.0;
+  }
+  else if ( gain < 0.0 ) {
+    cerr << "StifKarp: pluck amplitude less than zero!" << endl;
+    gain = 0.0;
+  }
+
+  pluckAmplitude = amplitude;
+  for (long i=0; i<length; i++)  {
+    // Fill delay with noise additively with current contents.
+    delayLine->tick((delayLine->lastOut() * 0.6) + 0.4 * noise->tick() * pluckAmplitude);
+    //delayLine->tick( combDelay->tick((delayLine->lastOut() * 0.6) + 0.4 * noise->tick() * pluckAmplitude));
+  }
+}
+
+void StifKarp :: noteOn(MY_FLOAT frequency, MY_FLOAT amplitude)
+{
+  this->setFrequency(frequency);
+  this->pluck(amplitude);
+
+#if defined(_STK_DEBUG_)
+  cerr << "StifKarp: NoteOn frequency = " << frequency << ", amplitude = " << amplitude << endl;
+#endif
+}
+
+void StifKarp :: noteOff(MY_FLOAT amplitude)
+{
+  MY_FLOAT gain = amplitude;
+  if ( gain > 1.0 ) {
+    cerr << "StifKarp: noteOff amplitude greater than 1.0!" << endl;
+    gain = 1.0;
+  }
+  else if ( gain < 0.0 ) {
+    cerr << "StifKarp: noteOff amplitude less than zero!" << endl;
+    gain = 0.0;
+  }
+  loopGain =  (1.0 - gain) * 0.5;
+
+#if defined(_STK_DEBUG_)
+  cerr << "StifPluck: NoteOff amplitude = " << amplitude << endl;
+#endif
+}
+
+MY_FLOAT StifKarp :: tick()
+{
+  MY_FLOAT temp = delayLine->lastOut() * loopGain;
+
+  // Calculate allpass stretching.
+  for (int i=0; i<4; i++)
+    temp = biQuad[i]->tick(temp);
+
+  // Moving average filter.
+  temp = filter->tick(temp);
+
+  lastOutput = delayLine->tick(temp);
+  lastOutput = lastOutput - combDelay->tick(lastOutput);
+  return lastOutput;
+}
+
+void StifKarp :: controlChange(int number, MY_FLOAT value)
+{
+  MY_FLOAT norm = value * ONE_OVER_128;
+  if ( norm < 0 ) {
+    norm = 0.0;
+    cerr << "StifKarp: Control value less than zero!" << endl;
+  }
+  else if ( norm > 1.0 ) {
+    norm = 1.0;
+    cerr << "StifKarp: Control value greater than 128.0!" << endl;
+  }
+
+  if (number == __SK_PickPosition_) // 4
+    setPickupPosition( norm );
+  else if (number == __SK_StringDamping_) // 11
+    setBaseLoopGain( 0.97 + (norm * 0.03) );
+  else if (number == __SK_StringDetune_) // 1
+    setStretch( 0.9 + (0.1 * (1.0 - norm)) );
+  else
+    cerr << "StifKarp: Undefined Control Number (" << number << ")!!" << endl;
+
+#if defined(_STK_DEBUG_)
+  cerr << "StifKarp: controlChange number = " << number << ", value = " << value << endl;
+#endif
+}
+