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STK two-zero filter class. More...
#include <TwoZero.h>
Public Member Functions | |
TwoZero () | |
Default constructor creates a second-order pass-through filter. | |
~TwoZero () | |
Class destructor. | |
void | ignoreSampleRateChange (bool ignore=true) |
A function to enable/disable the automatic updating of class data when the STK sample rate changes. | |
void | setB0 (StkFloat b0) |
Set the b[0] coefficient value. | |
void | setB1 (StkFloat b1) |
Set the b[1] coefficient value. | |
void | setB2 (StkFloat b2) |
Set the b[2] coefficient value. | |
void | setCoefficients (StkFloat b0, StkFloat b1, StkFloat b2, bool clearState=false) |
Set all filter coefficients. | |
void | setNotch (StkFloat frequency, StkFloat radius) |
Sets the filter coefficients for a "notch" at frequency (in Hz). | |
StkFloat | lastOut (void) const |
Return the last computed output value. | |
StkFloat | tick (StkFloat input) |
Input one sample to the filter and return one output. | |
StkFrames & | tick (StkFrames &frames, unsigned int channel=0) |
Take a channel of the StkFrames object as inputs to the filter and replace with corresponding outputs. | |
StkFrames & | tick (StkFrames &iFrames, StkFrames &oFrames, unsigned int iChannel=0, unsigned int oChannel=0) |
Take a channel of the iFrames object as inputs to the filter and write outputs to the oFrames object. |
STK two-zero filter class.
This class implements a two-zero digital filter. A method is provided for creating a "notch" in the frequency response while maintaining a constant filter gain.
by Perry R. Cook and Gary P. Scavone, 1995-2012.
void stk::TwoZero::setNotch | ( | StkFloat | frequency, | |
StkFloat | radius | |||
) |
Sets the filter coefficients for a "notch" at frequency (in Hz).
This method determines the filter coefficients corresponding to two complex-conjugate zeros with the given frequency (in Hz) and radius from the z-plane origin. The coefficients are then normalized to produce a maximum filter gain of one (independent of the filter gain parameter). The resulting filter frequency response has a "notch" or anti-resonance at the given frequency. The closer the zeros are to the unit-circle (radius close to or equal to one), the narrower the resulting notch width. The frequency value should be between zero and half the sample rate. The radius value should be positive.
Take a channel of the StkFrames object as inputs to the filter and replace with corresponding outputs.
The StkFrames argument reference is returned. The channel
argument must be less than the number of channels in the 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.
Implements stk::Filter.
00103 { 00104 #if defined(_STK_DEBUG_) 00105 if ( channel >= frames.channels() ) { 00106 oStream_ << "TwoZero::tick(): channel and StkFrames arguments are incompatible!"; 00107 handleError( StkError::FUNCTION_ARGUMENT ); 00108 } 00109 #endif 00110 00111 StkFloat *samples = &frames[channel]; 00112 unsigned int hop = frames.channels(); 00113 for ( unsigned int i=0; i<frames.frames(); i++, samples += hop ) { 00114 inputs_[0] = gain_ * *samples; 00115 *samples = b_[2] * inputs_[2] + b_[1] * inputs_[1] + b_[0] * inputs_[0]; 00116 inputs_[2] = inputs_[1]; 00117 inputs_[1] = inputs_[0]; 00118 } 00119 00120 lastFrame_[0] = *(samples-hop); 00121 return frames; 00122 }
StkFrames & stk::TwoZero::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 filter 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.
00125 { 00126 #if defined(_STK_DEBUG_) 00127 if ( iChannel >= iFrames.channels() || oChannel >= oFrames.channels() ) { 00128 oStream_ << "TwoZero::tick(): channel and StkFrames arguments are incompatible!"; 00129 handleError( StkError::FUNCTION_ARGUMENT ); 00130 } 00131 #endif 00132 00133 StkFloat *iSamples = &iFrames[iChannel]; 00134 StkFloat *oSamples = &oFrames[oChannel]; 00135 unsigned int iHop = iFrames.channels(), oHop = oFrames.channels(); 00136 for ( unsigned int i=0; i<iFrames.frames(); i++, iSamples += iHop, oSamples += oHop ) { 00137 inputs_[0] = gain_ * *iSamples; 00138 *oSamples = b_[2] * inputs_[2] + b_[1] * inputs_[1] + b_[0] * inputs_[0]; 00139 inputs_[2] = inputs_[1]; 00140 inputs_[1] = inputs_[0]; 00141 } 00142 00143 lastFrame_[0] = *(oSamples-oHop); 00144 return iFrames; 00145 }
The Synthesis ToolKit in C++ (STK) |
©1995-2012 Perry R. Cook and Gary P. Scavone. All Rights Reserved. |