twopole.cpp

Mobile STK for Symbian OS V0.1

/***************************************************/
/*! \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 - 2005.
*/
/***************************************************/

#include "TwoPole.h"
#if !defined(SYMBIAN)
#include <math.h>
#else
#include "symbmath.h"
#endif

TwoPole :: TwoPole() : Filter()
{
#if !defined(SYMBIAN)
  std::vector<StkFloat> b(1, 1.0);
  std::vector<StkFloat> a(3, 0.0);
#else
  FloatVector b(1, 1.0);
  FloatVector a(3, 0.0);

/*	TReal *b = new (ELeave) TReal[1];
	b[0] = 1.0;
	TReal *a = new (ELeave) TReal[3];
	a[1] = 0.0;
	a[2] = 0.0;*/
#endif
  a[0] = 1.0;
  Filter::setCoefficients( b, a );
}

TwoPole :: ~TwoPole()
{
}

void TwoPole :: clear(void)
{
  Filter::clear();
}

void TwoPole :: setB0(StkFloat b0)
{
  b_[0] = b0;
}

void TwoPole :: setA1(StkFloat a1)
{
  a_[1] = a1;
}

void TwoPole :: setA2(StkFloat a2)
{
  a_[2] = a2;
}

void TwoPole :: setResonance(StkFloat frequency, StkFloat radius, bool normalize)
{
  a_[2] = radius * radius;
  a_[1] = (StkFloat) -2.0 * radius * cos(TWO_PI * frequency / Stk::sampleRate());

  if ( normalize ) {
    // Normalize the filter gain ... not terribly efficient.
    StkFloat real = 1 - radius + (a_[2] - radius) * cos(TWO_PI * 2 * frequency / Stk::sampleRate());
    StkFloat imag = (a_[2] - radius) * sin(TWO_PI * 2 * frequency / Stk::sampleRate());
    b_[0] = sqrt( pow(real, 2) + pow(imag, 2) );
  }

}

void TwoPole :: setGain(StkFloat gain)
{
  Filter::setGain(gain);
}

StkFloat TwoPole :: getGain(void) const
{
  return Filter::getGain();
}

StkFloat TwoPole :: lastOut(void) // SYMBIAN const removed: const
{
  return Filter::lastOut();
}

StkFloat TwoPole :: tick( StkFloat input )
{
  inputs_[0] = gain_ * input;
  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];
}

StkFrames& TwoPole :: tick( StkFrames& frames, unsigned int channel )
{
  return Filter::tick( frames, channel );
}