Version 4.2.1

include/Blit.h

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+/***************************************************/
+/*! \class Blit
+    \brief STK band-limited impulse train class.
+
+    This class generates a band-limited impulse train using a
+    closed-form algorithm reported by Stilson and Smith in "Alias-Free
+    Digital Synthesis of Classic Analog Waveforms", 1996.  The user
+    can specify both the fundamental frequency of the impulse train
+    and the number of harmonics contained in the resulting signal.
+
+    The signal is normalized so that the peak value is +/-1.0.
+
+    If nHarmonics is 0, then the signal will contain all harmonics up
+    to half the sample rate.  Note, however, that this setting may
+    produce aliasing in the signal when the frequency is changing (no
+    automatic modification of the number of harmonics is performed by
+    the setFrequency() function).
+
+    Original code by Robin Davies, 2005.
+    Revisions by Gary Scavone for STK, 2005.
+*/
+/***************************************************/
+
+#ifndef STK_BLIT_H
+#define STK_BLIT_H
+
+#include "Generator.h"
+
+class Blit: public Generator
+{
+ public:
+  //! Default constructor that initializes BLIT frequency to 220 Hz.
+  Blit( StkFloat frequency = 220.0 );
+
+  //! Class destructor.
+  ~Blit();
+
+  //! Resets the oscillator state and phase to 0.
+  void reset();
+
+  //! Set the phase of the signal.
+  /*!
+    Set the phase of the signal, in the range 0 to 1.
+  */
+  void setPhase( StkFloat phase ) { phase_ = PI * phase; };
+
+  //! Get the current phase of the signal.
+  /*!
+    Get the phase of the signal, in the range [0 to 1.0).
+  */
+  StkFloat getPhase() const { return phase_ / PI; };
+
+  //! Set the impulse train rate in terms of a frequency in Hz.
+  void setFrequency( StkFloat frequency );
+
+  //! Set the number of harmonics generated in the signal.
+  /*!
+    This function sets the number of harmonics contained in the
+    resulting signal.  It is equivalent to (2 * M) + 1 in the BLIT
+    algorithm.  The default value of 0 sets the algorithm for maximum
+    harmonic content (harmonics up to half the sample rate).  This
+    parameter is not checked against the current sample rate and
+    fundamental frequency.  Thus, aliasing can result if one or more
+    harmonics for a given fundamental frequency exceeds fs / 2.  This
+    behavior was chosen over the potentially more problematic solution
+    of automatically modifying the M parameter, which can produce
+    audible clicks in the signal.
+  */
+  void setHarmonics( unsigned int nHarmonics = 0 );
+
+ protected:
+
+  void updateHarmonics( void );
+  StkFloat computeSample( void );
+
+  unsigned int nHarmonics_;
+  unsigned int m_;
+  StkFloat rate_;
+  StkFloat phase_;
+  StkFloat p_;
+
+};
+
+#endif