Blit.h

#ifndef STK_BLIT_H
#define STK_BLIT_H
 
#include "Generator.h"
#include <cmath>
#include <limits>
 
namespace stk {
 
/***************************************************/
/***************************************************/
 
class Blit: public Generator
{
 public:
  Blit( StkFloat frequency = 220.0 );
 
  ~Blit();
 
  void reset();
 
 
  void setPhase( StkFloat phase ) { phase_ = PI * phase; };
 
 
  StkFloat getPhase() const { return phase_ / PI; };
 
  void setFrequency( StkFloat frequency );
 
 
  void setHarmonics( unsigned int nHarmonics = 0 );
 
  StkFloat lastOut( void ) const { return lastFrame_[0]; };
 
  StkFloat tick( void );
 
 
  StkFrames& tick( StkFrames& frames, unsigned int channel = 0 );
 
 protected:
 
  void updateHarmonics( void );
 
  unsigned int nHarmonics_;
  unsigned int m_;
  StkFloat rate_;
  StkFloat phase_;
  StkFloat p_;
 
};
 
inline StkFloat Blit :: tick( void )
{
  // The code below implements the SincM algorithm of Stilson and
  // Smith with an additional scale factor of P / M applied to
  // normalize the output.
 
  // A fully optimized version of this code would replace the two sin
  // calls with a pair of fast sin oscillators, for which stable fast
  // two-multiply algorithms are well known. In the spirit of STK,
  // which favors clarity over performance, the optimization has not
  // been made here.
 
  // Avoid a divide by zero at the sinc peak, which has a limiting
  // value of 1.0.
  StkFloat tmp, denominator = sin( phase_ );
  if ( denominator <= std::numeric_limits<StkFloat>::epsilon() )
    tmp = 1.0;
  else {
    tmp =  sin( m_ * phase_ );
    tmp /= m_ * denominator;
  }
 
  phase_ += rate_;
  if ( phase_ >= PI ) phase_ -= PI;
 
  lastFrame_[0] = tmp;
         return lastFrame_[0];
}
 
inline StkFrames& Blit :: tick( StkFrames& frames, unsigned int channel )
{
#if defined(_STK_DEBUG_)
  if ( channel >= frames.channels() ) {
    oStream_ << "Blit::tick(): channel and StkFrames arguments are incompatible!";
    handleError( StkError::FUNCTION_ARGUMENT );
  }
#endif
 
  StkFloat *samples = &frames[channel];
  unsigned int hop = frames.channels();
  for ( unsigned int i=0; i<frames.frames(); i++, samples += hop )
    *samples = Blit::tick();
 
  return frames;
}
 
} // stk namespace
 
#endif