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1 #ifndef STK_ENVELOPE_H
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2 #define STK_ENVELOPE_H
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3
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4 #include "Generator.h"
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5
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6 namespace stk {
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7
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8 /***************************************************/
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9 /*! \class Envelope
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10 \brief STK linear line envelope class.
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11
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12 This class implements a simple linear line envelope generator
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13 which is capable of ramping to an arbitrary target value by a
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14 specified \e rate. It also responds to simple \e keyOn and \e
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15 keyOff messages, ramping to 1.0 on keyOn and to 0.0 on keyOff.
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16
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17 by Perry R. Cook and Gary P. Scavone, 1995--2014.
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18 */
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19 /***************************************************/
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20
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21 class Envelope : public Generator
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22 {
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23 public:
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24
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25 //! Default constructor.
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26 Envelope( void );
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27
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28 //! Class destructor.
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29 ~Envelope( void );
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30
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31 //! Assignment operator.
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32 Envelope& operator= ( const Envelope& e );
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33
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34 //! Set target = 1.
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35 void keyOn( void ) { this->setTarget( 1.0 ); };
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36
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37 //! Set target = 0.
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38 void keyOff( void ) { this->setTarget( 0.0 ); };
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39
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40 //! Set the \e rate.
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41 /*!
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42 The \e rate must be positive (though a value of 0.0 is allowed).
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43 */
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44 void setRate( StkFloat rate );
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45
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46 //! Set the \e rate based on a positive time duration (seconds).
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47 /*!
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48 The \e rate is calculated such that the envelope will ramp from
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49 a value of 0.0 to 1.0 in the specified time duration.
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50 */
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51 void setTime( StkFloat time );
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52
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53 //! Set the target value.
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54 void setTarget( StkFloat target );
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55
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56 //! Set current and target values to \e value.
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57 void setValue( StkFloat value );
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58
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59 //! Return the current envelope \e state (0 = at target, 1 otherwise).
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60 int getState( void ) const { return state_; };
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61
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62 //! Return the last computed output value.
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63 StkFloat lastOut( void ) const { return lastFrame_[0]; };
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64
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65 //! Compute and return one output sample.
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66 StkFloat tick( void );
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67
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68 //! Fill a channel of the StkFrames object with computed outputs.
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69 /*!
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70 The \c channel argument must be less than the number of
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71 channels in the StkFrames argument (the first channel is specified
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72 by 0). However, range checking is only performed if _STK_DEBUG_
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73 is defined during compilation, in which case an out-of-range value
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74 will trigger an StkError exception.
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75 */
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76 StkFrames& tick( StkFrames& frames, unsigned int channel = 0 );
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77
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78 protected:
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79
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80 void sampleRateChanged( StkFloat newRate, StkFloat oldRate );
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81
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82 StkFloat value_;
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83 StkFloat target_;
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84 StkFloat rate_;
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85 int state_;
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86 };
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87
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88 inline StkFloat Envelope :: tick( void )
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89 {
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90 if ( state_ ) {
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91 if ( target_ > value_ ) {
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92 value_ += rate_;
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93 if ( value_ >= target_ ) {
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94 value_ = target_;
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95 state_ = 0;
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96 }
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97 }
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98 else {
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99 value_ -= rate_;
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100 if ( value_ <= target_ ) {
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101 value_ = target_;
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102 state_ = 0;
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103 }
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104 }
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105 lastFrame_[0] = value_;
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106 }
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107
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108 return value_;
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109 }
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110
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111 inline StkFrames& Envelope :: tick( StkFrames& frames, unsigned int channel )
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112 {
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113 #if defined(_STK_DEBUG_)
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114 if ( channel >= frames.channels() ) {
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115 oStream_ << "Envelope::tick(): channel and StkFrames arguments are incompatible!";
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116 handleError( StkError::FUNCTION_ARGUMENT );
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117 }
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118 #endif
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119
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120 StkFloat *samples = &frames[channel];
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121 unsigned int hop = frames.channels();
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122 for ( unsigned int i=0; i<frames.frames(); i++, samples += hop )
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123 *samples = tick();
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124
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125 return frames;
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126 }
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127
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128 } // stk namespace
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129
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130 #endif
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