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https://github.com/thestk/stk
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118 lines
3.0 KiB
C++
118 lines
3.0 KiB
C++
#ifndef STK_STIFKARP_H
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#define STK_STIFKARP_H
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#include "Instrmnt.h"
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#include "DelayL.h"
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#include "DelayA.h"
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#include "OneZero.h"
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#include "Noise.h"
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#include "BiQuad.h"
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namespace stk {
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/***************************************************/
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/*! \class StifKarp
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\brief STK plucked stiff string instrument.
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This class implements a simple plucked string
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algorithm (Karplus Strong) with enhancements
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(Jaffe-Smith, Smith, and others), including
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string stiffness and pluck position controls.
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The stiffness is modeled with allpass filters.
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This is a digital waveguide model, making its
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use possibly subject to patents held by
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Stanford University, Yamaha, and others.
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Control Change Numbers:
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- Pickup Position = 4
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- String Sustain = 11
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- String Stretch = 1
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by Perry R. Cook and Gary P. Scavone, 1995 - 2010.
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*/
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/***************************************************/
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class StifKarp : public Instrmnt
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{
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public:
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//! Class constructor, taking the lowest desired playing frequency.
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StifKarp( StkFloat lowestFrequency );
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//! Class destructor.
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~StifKarp( void );
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//! Reset and clear all internal state.
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void clear( void );
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//! Set instrument parameters for a particular frequency.
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void setFrequency( StkFloat frequency );
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//! Set the stretch "factor" of the string (0.0 - 1.0).
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void setStretch( StkFloat stretch );
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//! Set the pluck or "excitation" position along the string (0.0 - 1.0).
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void setPickupPosition( StkFloat position );
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//! Set the base loop gain.
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/*!
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The actual loop gain is set according to the frequency.
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Because of high-frequency loop filter roll-off, higher
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frequency settings have greater loop gains.
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*/
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void setBaseLoopGain( StkFloat aGain );
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//! Pluck the string with the given amplitude using the current frequency.
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void pluck( StkFloat amplitude );
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//! Start a note with the given frequency and amplitude.
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void noteOn( StkFloat frequency, StkFloat amplitude );
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//! Stop a note with the given amplitude (speed of decay).
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void noteOff( StkFloat amplitude );
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//! Perform the control change specified by \e number and \e value (0.0 - 128.0).
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void controlChange( int number, StkFloat value );
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//! Compute and return one output sample.
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StkFloat tick( unsigned int channel = 0 );
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protected:
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DelayA delayLine_;
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DelayL combDelay_;
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OneZero filter_;
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Noise noise_;
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BiQuad biquad_[4];
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unsigned long length_;
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StkFloat loopGain_;
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StkFloat baseLoopGain_;
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StkFloat lastFrequency_;
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StkFloat lastLength_;
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StkFloat stretching_;
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StkFloat pluckAmplitude_;
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StkFloat pickupPosition_;
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};
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inline StkFloat StifKarp :: tick( unsigned int )
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{
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StkFloat temp = delayLine_.lastOut() * loopGain_;
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// Calculate allpass stretching.
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for (int i=0; i<4; i++)
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temp = biquad_[i].tick(temp);
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// Moving average filter.
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temp = filter_.tick(temp);
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lastFrame_[0] = delayLine_.tick(temp);
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lastFrame_[0] = lastFrame_[0] - combDelay_.tick( lastFrame_[0] );
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return lastFrame_[0];
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}
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} // stk namespace
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#endif
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