stk/STK/TwoPole.cpp

/*******************************************/
/*  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;
}