mirror of
https://github.com/thestk/stk
synced 2026-01-11 03:51:53 +00:00
90 lines
2.9 KiB
C++
90 lines
2.9 KiB
C++
/***************************************************/
|
|
/*! \class BlitSquare
|
|
\brief STK band-limited square wave class.
|
|
|
|
This class generates a band-limited square wave signal. It is
|
|
derived in part from the approach reported by Stilson and Smith in
|
|
"Alias-Free Digital Synthesis of Classic Analog Waveforms", 1996.
|
|
The algorithm implemented in this class uses a SincM function with
|
|
an even M value to achieve a bipolar bandlimited impulse train.
|
|
This signal is then integrated to achieve a square waveform. The
|
|
integration process has an associated DC offset but that is
|
|
subtracted off the output signal.
|
|
|
|
The user can specify both the fundamental frequency of the
|
|
waveform and the number of harmonics contained in the resulting
|
|
signal.
|
|
|
|
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).
|
|
|
|
Based on initial code of Robin Davies, 2005.
|
|
Modified algorithm code by Gary Scavone, 2005.
|
|
*/
|
|
/***************************************************/
|
|
|
|
#ifndef STK_BLITSQUARE_H
|
|
#define STK_BLITSQUARE_H
|
|
|
|
#include "Generator.h"
|
|
|
|
class BlitSquare: public Generator
|
|
{
|
|
public:
|
|
//! Default constructor that initializes BLIT frequency to 220 Hz.
|
|
BlitSquare( StkFloat frequency = 220.0 );
|
|
|
|
//! Class destructor.
|
|
~BlitSquare();
|
|
|
|
//! 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_;
|
|
StkFloat offset_;
|
|
};
|
|
|
|
#endif
|