Version 4.4.0

include/Blit.h

@@ -1,3 +1,12 @@
+#ifndef STK_BLIT_H
+#define STK_BLIT_H
+
+#include "Generator.h"
+#include <cmath>
+#include <limits>
+
+namespace stk {
+
 /***************************************************/
 /*! \class Blit
     \brief STK band-limited impulse train class.
@@ -21,11 +30,6 @@
 */
 /***************************************************/
 
-#ifndef STK_BLIT_H
-#define STK_BLIT_H
-
-#include "Generator.h"
-
 class Blit: public Generator
 {
  public:
@@ -68,10 +72,25 @@ class Blit: public Generator
   */
   void setHarmonics( unsigned int nHarmonics = 0 );
 
+  //! Return the last computed output value.
+  StkFloat lastOut( void ) const { return lastFrame_[0]; };
+
+  //! Compute and return one output sample.
+  StkFloat tick( void );
+
+  //! Fill a channel of the StkFrames object with computed outputs.
+  /*!
+    The \c channel argument must be less than the number of
+    channels in the StkFrames argument (the first channel is specified
+    by 0).  However, range checking is only performed if _STK_DEBUG_
+    is defined during compilation, in which case an out-of-range value
+    will trigger an StkError exception.
+  */
+  StkFrames& tick( StkFrames& frames, unsigned int channel = 0 );
+
  protected:
 
   void updateHarmonics( void );
-  StkFloat computeSample( void );
 
   unsigned int nHarmonics_;
   unsigned int m_;
@@ -81,4 +100,52 @@ class Blit: public Generator
 
 };
 
+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() ) {
+    errorString_ << "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