The Synthesis ToolKit in C++ (STK)

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BlitSquare.h
1 #ifndef STK_BLITSQUARE_H
2 #define STK_BLITSQUARE_H
3
4 #include "Generator.h"
5 #include <cmath>
6 #include <limits>
7
8 namespace stk {
9
10 /***************************************************/
40 /***************************************************/
41
42 class BlitSquare: public Generator
43 {
44 public:
46 BlitSquare( StkFloat frequency = 220.0 );
47
49 ~BlitSquare();
50
52 void reset();
53
55
58 void setPhase( StkFloat phase ) { phase_ = PI * phase; };
59
61
64 StkFloat getPhase() const { return phase_ / PI; };
65
67 void setFrequency( StkFloat frequency );
68
70
82 void setHarmonics( unsigned int nHarmonics = 0 );
83
85 StkFloat lastOut( void ) const { return lastFrame_[0]; };
86
88 StkFloat tick( void );
89
91
98 StkFrames& tick( StkFrames& frames, unsigned int channel = 0 );
99
100 protected:
101
102 void updateHarmonics( void );
103
104 unsigned int nHarmonics_;
105 unsigned int m_;
106 StkFloat rate_;
107 StkFloat phase_;
108 StkFloat p_;
109 StkFloat a_;
110 StkFloat lastBlitOutput_;
111 StkFloat dcbState_;
112 };
113
114 inline StkFloat BlitSquare :: tick( void )
115 {
116 StkFloat temp = lastBlitOutput_;
117
118 // A fully optimized version of this would replace the two sin calls
119 // with a pair of fast sin oscillators, for which stable fast
120 // two-multiply algorithms are well known. In the spirit of STK,
121 // which favors clarity over performance, the optimization has
122 // not been made here.
123
124 // Avoid a divide by zero, or use of a denomralized divisor
125 // at the sinc peak, which has a limiting value of 1.0.
126 StkFloat denominator = sin( phase_ );
127 if ( fabs( denominator ) < std::numeric_limits<StkFloat>::epsilon() ) {
128 // Inexact comparison safely distinguishes betwen *close to zero*, and *close to PI*.
129 if ( phase_ < 0.1f || phase_ > TWO_PI - 0.1f )
130 lastBlitOutput_ = a_;
131 else
132 lastBlitOutput_ = -a_;
133 }
134 else {
135 lastBlitOutput_ = sin( m_ * phase_ );
136 lastBlitOutput_ /= p_ * denominator;
137 }
138
139 lastBlitOutput_ += temp;
140
141 // Now apply DC blocker.
142 lastFrame_[0] = lastBlitOutput_ - dcbState_ + 0.999 * lastFrame_[0];
143 dcbState_ = lastBlitOutput_;
144
145 phase_ += rate_;
146 if ( phase_ >= TWO_PI ) phase_ -= TWO_PI;
147
148 return lastFrame_[0];
149 }
150
151 inline StkFrames& BlitSquare :: tick( StkFrames& frames, unsigned int channel )
152 {
153 #if defined(_STK_DEBUG_)
154 if ( channel >= frames.channels() ) {
155 oStream_ << "BlitSquare::tick(): channel and StkFrames arguments are incompatible!";
156 handleError( StkError::FUNCTION_ARGUMENT );
157 }
158 #endif
159
160 StkFloat *samples = &frames[channel];
161 unsigned int hop = frames.channels();
162 for ( unsigned int i=0; i<frames.frames(); i++, samples += hop )
163 *samples = BlitSquare::tick();
164
165 return frames;
166 }
167
168 } // stk namespace
169
170 #endif

The Synthesis ToolKit in C++ (STK)
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