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stk::Twang Class Reference

STK enhanced plucked string class. More...

#include <Twang.h>

Inheritance diagram for stk::Twang:
stk::Stk

List of all members.

Public Member Functions

 Twang (StkFloat lowestFrequency=50.0)
 Class constructor, taking the lowest desired playing frequency.
 ~Twang (void)
 Class destructor.
void clear (void)
 Reset and clear all internal state.
void setLowestFrequency (StkFloat frequency)
 Set the delayline parameters to allow frequencies as low as specified.
void setFrequency (StkFloat frequency)
 Set the delayline parameters for a particular frequency.
void setPluckPosition (StkFloat position)
 Set the pluck or "excitation" position along the string (0.0 - 1.0).
void setLoopGain (StkFloat loopGain)
 Set the nominal loop gain.
void setLoopFilter (std::vector< StkFloat > coefficients)
 Set the loop filter coefficients.
const StkFrameslastFrame (void) const
 Return an StkFrames reference to the last output sample frame.
StkFloat tick (StkFloat input)
 Compute and return one output sample.
StkFramestick (StkFrames &frames, unsigned int channel=0)
 Take a channel of the iFrames object as inputs to the class and write outputs to the oFrames object.
StkFramestick (StkFrames &iFrames, StkFrames &oFrames, unsigned int iChannel=0, unsigned int oChannel=0)
 Take a channel of the iFrames object as inputs to the effect and write outputs to the oFrames object.

Detailed Description

STK enhanced plucked string class.

This class implements an enhanced plucked-string physical model, a la Jaffe-Smith, Smith, Karjalainen and others. It includes a comb filter to simulate pluck position. The tick() function takes an input sample, which is added to the delayline input. This can be used to implement commuted synthesis (if the input samples are derived from the impulse response of a body filter) and/or feedback (as in an electric guitar model).

This is a digital waveguide model, making its use possibly subject to patents held by Stanford University, Yamaha, and others.

by Perry R. Cook and Gary P. Scavone, 1995-2011.


Member Function Documentation

void stk::Twang::setLoopGain ( StkFloat  loopGain  ) 

Set the nominal loop gain.

The actual loop gain is based on the value set with this function, but scaled slightly according to the frequency. Higher frequency settings have greater loop gains because of high-frequency loop-filter roll-off.

void stk::Twang::setLoopFilter ( std::vector< StkFloat >  coefficients  ) 

Set the loop filter coefficients.

The loop filter can be any arbitrary FIR filter. By default, the coefficients are set for a first-order lowpass filter with coefficients b = [0.5 0.5].

StkFrames & stk::Twang::tick ( StkFrames frames,
unsigned int  channel = 0 
) [inline]

Take a channel of the iFrames object as inputs to the class and write outputs to the oFrames object.

The iFrames object reference is returned. Each channel argument must be less than the number of channels in the corresponding StkFrames argument (the first channel is specified by 0). However, range checking is only performed if _STK_DEBUG_ is defined during compilation, in which case an out-of-range value will trigger an StkError exception.

00121 {
00122 #if defined(_STK_DEBUG_)
00123   if ( channel >= frames.channels() ) {
00124     oStream_ << "Twang::tick(): channel and StkFrames arguments are incompatible!";
00125     handleError( StkError::FUNCTION_ARGUMENT );
00126   }
00127 #endif
00128 
00129   StkFloat *samples = &frames[channel];
00130   unsigned int hop = frames.channels();
00131   for ( unsigned int i=0; i<frames.frames(); i++, samples += hop )
00132     *samples = tick( *samples );
00133 
00134   return frames;
00135 }

StkFrames & stk::Twang::tick ( StkFrames iFrames,
StkFrames oFrames,
unsigned int  iChannel = 0,
unsigned int  oChannel = 0 
) [inline]

Take a channel of the iFrames object as inputs to the effect and write outputs to the oFrames object.

The iFrames object reference is returned. Each channel argument must be less than the number of channels in the corresponding StkFrames argument (the first channel is specified by 0). However, range checking is only performed if _STK_DEBUG_ is defined during compilation, in which case an out-of-range value will trigger an StkError exception.

00138 {
00139 #if defined(_STK_DEBUG_)
00140   if ( iChannel >= iFrames.channels() || oChannel >= oFrames.channels() ) {
00141     oStream_ << "Twang::tick(): channel and StkFrames arguments are incompatible!";
00142     handleError( StkError::FUNCTION_ARGUMENT );
00143   }
00144 #endif
00145 
00146   StkFloat *iSamples = &iFrames[iChannel];
00147   StkFloat *oSamples = &oFrames[oChannel];
00148   unsigned int iHop = iFrames.channels(), oHop = oFrames.channels();
00149   for ( unsigned int i=0; i<iFrames.frames(); i++, iSamples += iHop, oSamples += oHop )
00150     *oSamples = tick( *iSamples );
00151 
00152   return iFrames;
00153 }


The documentation for this class was generated from the following file:

The Synthesis ToolKit in C++ (STK)
©1995-2011 Perry R. Cook and Gary P. Scavone. All Rights Reserved.