Version 4.0

src/TwoPole.cpp

@@ -1,60 +1,93 @@
-/*******************************************/
-/*  Two Pole Filter Class,                 */
-/*  by Perry R. Cook, 1995-96              */ 
-/*  See books on filters to understand     */
-/*  more about how this works.  Nothing    */
-/*  out of the ordinary in this version.   */
-/*******************************************/
-
-#include "TwoPole.h"
-
-TwoPole :: TwoPole() : Filter()
-{
-  outputs = (MY_FLOAT *) malloc(2 * sizeof(MY_FLOAT));
-  poleCoeffs[0] = (MY_FLOAT) 0.0;
-  poleCoeffs[1] = (MY_FLOAT) 0.0;
-  gain = (MY_FLOAT) 1.0;
-  this->clear();
-}
-
-TwoPole :: ~TwoPole()
-{
-  free(outputs);
-}
-
-void TwoPole :: clear()
-{
-  outputs[0] = (MY_FLOAT) 0.0;
-  outputs[1] = (MY_FLOAT) 0.0;
-  lastOutput = (MY_FLOAT) 0.0;
-}
-
-void TwoPole :: setPoleCoeffs(MY_FLOAT *coeffs)
-{
-  poleCoeffs[0] = coeffs[0];
-  poleCoeffs[1] = coeffs[1];
-}
-
-void TwoPole :: setFreqAndReson(MY_FLOAT freq, MY_FLOAT reson)
-{
-  poleCoeffs[1] = - (reson * reson);
-  poleCoeffs[0] = (MY_FLOAT) 2.0 * reson * cos(TWO_PI * (double) freq / SRATE);
-}
-
-void TwoPole :: setGain(MY_FLOAT aValue)
-{
-  gain = aValue;
-}
-
-MY_FLOAT TwoPole :: tick(MY_FLOAT sample) // Perform Filter Operation
-{                                         //  TwoPole is a two pole filter (duh!)
-  MY_FLOAT temp;                          //  Look it up in your favorite DSP text
-  temp = sample * gain;
-  temp += poleCoeffs[0] * outputs[0];
-  temp += poleCoeffs[1] * outputs[1];
-  outputs[1] = outputs[0];
-  outputs[0] = temp;
-  lastOutput = outputs[0];
-  return lastOutput;
-}
-
+/***************************************************/
+/*! \class TwoPole
+    \brief STK two-pole filter class.
+
+    This protected Filter subclass implements
+    a two-pole digital filter.  A method is
+    provided for creating a resonance in the
+    frequency response while maintaining a nearly
+    constant filter gain.
+
+    by Perry R. Cook and Gary P. Scavone, 1995 - 2002.
+*/
+/***************************************************/
+
+#include "TwoPole.h"
+#include <math.h>
+
+TwoPole :: TwoPole() : Filter()
+{
+  MY_FLOAT B = 1.0;
+  MY_FLOAT A[3] = {1.0, 0.0, 0.0};
+  Filter::setCoefficients( 1, &B, 3, A );
+}
+
+TwoPole :: ~TwoPole()
+{
+}
+
+void TwoPole :: clear(void)
+{
+  Filter::clear();
+}
+
+void TwoPole :: setB0(MY_FLOAT b0)
+{
+  b[0] = b0;
+}
+
+void TwoPole :: setA1(MY_FLOAT a1)
+{
+  a[1] = a1;
+}
+
+void TwoPole :: setA2(MY_FLOAT a2)
+{
+  a[2] = a2;
+}
+
+void TwoPole :: setResonance(MY_FLOAT frequency, MY_FLOAT radius, bool normalize)
+{
+  a[2] = radius * radius;
+  a[1] = (MY_FLOAT) -2.0 * radius * cos(TWO_PI * frequency / Stk::sampleRate());
+
+  if ( normalize ) {
+    // Normalize the filter gain ... not terribly efficient.
+    MY_FLOAT real = 1 - radius + (a[2] - radius) * cos(TWO_PI * 2 * frequency / Stk::sampleRate());
+    MY_FLOAT imag = (a[2] - radius) * sin(TWO_PI * 2 * frequency / Stk::sampleRate());
+    b[0] = sqrt( pow(real, 2) + pow(imag, 2) );
+  }
+}
+
+void TwoPole :: setGain(MY_FLOAT theGain)
+{
+  Filter::setGain(theGain);
+}
+
+MY_FLOAT TwoPole :: getGain(void) const
+{
+  return Filter::getGain();
+}
+
+MY_FLOAT TwoPole :: lastOut(void) const
+{
+  return Filter::lastOut();
+}
+
+MY_FLOAT TwoPole :: tick(MY_FLOAT sample)
+{
+  inputs[0] = gain * sample;
+  outputs[0] = b[0] * inputs[0] - a[2] * outputs[2] - a[1] * outputs[1];
+  outputs[2] = outputs[1];
+  outputs[1] = outputs[0];
+
+  return outputs[0];
+}
+
+MY_FLOAT *TwoPole :: tick(MY_FLOAT *vector, unsigned int vectorSize)
+{
+  for (unsigned int i=0; i<vectorSize; i++)
+    vector[i] = tick(vector[i]);
+
+  return vector;
+}