Home Information Classes Download Usage Mail List Requirements Links FAQ Tutorial

# Blit.h

    00001 #ifndef STK_BLIT_H
    00002 #define STK_BLIT_H
    00003
    00004 #include "Generator.h"
    00005 #include <cmath>
    00006 #include <limits>
    00007
    00008 namespace stk {
    00009
    00010 /***************************************************/
    00031 /***************************************************/
    00032
    00033 class Blit: public Generator
    00034 {
    00035  public:
    00037   Blit( StkFloat frequency = 220.0 );
    00038
    00040   ~Blit();
    00041
    00043   void reset();
    00044
    00046
    00049   void setPhase( StkFloat phase ) { phase_ = PI * phase; };
    00050
    00052
    00055   StkFloat getPhase() const { return phase_ / PI; };
    00056
    00058   void setFrequency( StkFloat frequency );
    00059
    00061
    00073   void setHarmonics( unsigned int nHarmonics = 0 );
    00074
    00076   StkFloat lastOut( void ) const { return lastFrame_[0]; };
    00077
    00079   StkFloat tick( void );
    00080
    00082
    00089   StkFrames& tick( StkFrames& frames, unsigned int channel = 0 );
    00090
    00091  protected:
    00092
    00093   void updateHarmonics( void );
    00094
    00095   unsigned int nHarmonics_;
    00096   unsigned int m_;
    00097   StkFloat rate_;
    00098   StkFloat phase_;
    00099   StkFloat p_;
    00100
    00101 };
    00102
    00103 inline StkFloat Blit :: tick( void )
    00104 {
    00105   // The code below implements the SincM algorithm of Stilson and
    00106   // Smith with an additional scale factor of P / M applied to
    00107   // normalize the output.
    00108
    00109   // A fully optimized version of this code would replace the two sin
    00110   // calls with a pair of fast sin oscillators, for which stable fast
    00111   // two-multiply algorithms are well known. In the spirit of STK,
    00112   // which favors clarity over performance, the optimization has not
    00113   // been made here.
    00114
    00115   // Avoid a divide by zero at the sinc peak, which has a limiting
    00116   // value of 1.0.
    00117   StkFloat tmp, denominator = sin( phase_ );
    00118   if ( denominator <= std::numeric_limits<StkFloat>::epsilon() )
    00119     tmp = 1.0;
    00120   else {
    00121     tmp =  sin( m_ * phase_ );
    00122     tmp /= m_ * denominator;
    00123   }
    00124
    00125   phase_ += rate_;
    00126   if ( phase_ >= PI ) phase_ -= PI;
    00127
    00128   lastFrame_[0] = tmp;
    00129          return lastFrame_[0];
    00130 }
    00131
    00132 inline StkFrames& Blit :: tick( StkFrames& frames, unsigned int channel )
    00133 {
    00134 #if defined(_STK_DEBUG_)
    00135   if ( channel >= frames.channels() ) {
    00136     errorString_ << "Blit::tick(): channel and StkFrames arguments are incompatible!";
    00137     handleError( StkError::FUNCTION_ARGUMENT );
    00138   }
    00139 #endif
    00140
    00141   StkFloat *samples = &frames[channel];
    00142   unsigned int hop = frames.channels();
    00143   for ( unsigned int i=0; i<frames.frames(); i++, samples += hop )
    00144     *samples = Blit::tick();
    00145
    00146   return frames;
    00147 }
    00148
    00149 } // stk namespace
    00150
    00151 #endif

The Synthesis ToolKit in C++ (STK)
©1995-2010 Perry R. Cook and Gary P. Scavone. All Rights Reserved.