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stk::TwoPole Class Reference

STK two-pole filter class. More...

#include <TwoPole.h>

Inheritance diagram for stk::TwoPole:
stk::Filter stk::Stk

Public Member Functions

 TwoPole (void)
 Default constructor creates a second-order pass-through filter.
 
 ~TwoPole ()
 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 setA1 (StkFloat a1)
 Set the a[1] coefficient value.
 
void setA2 (StkFloat a2)
 Set the a[2] coefficient value.
 
void setCoefficients (StkFloat b0, StkFloat a1, StkFloat a2, bool clearState=false)
 Set all filter coefficients.
 
void setResonance (StkFloat frequency, StkFloat radius, bool normalize=false)
 Sets the filter coefficients for a resonance at frequency (in Hz). More...
 
StkFloat lastOut (void) const
 Return the last computed output value.
 
StkFloat tick (StkFloat input)
 Input one sample to the filter and return one output.
 
StkFramestick (StkFrames &frames, unsigned int channel=0)
 Take a channel of the StkFrames object as inputs to the filter and replace with corresponding outputs. More...
 
StkFramestick (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. More...
 
- Public Member Functions inherited from stk::Filter
 Filter (void)
 Class constructor.
 
unsigned int channelsIn (void) const
 Return the number of input channels for the class.
 
unsigned int channelsOut (void) const
 Return the number of output channels for the class.
 
virtual void clear (void)
 Clears all internal states of the filter.
 
void setGain (StkFloat gain)
 Set the filter gain. More...
 
StkFloat getGain (void) const
 Return the current filter gain.
 
StkFloat phaseDelay (StkFloat frequency)
 Return the filter phase delay at the specified frequency. More...
 
const StkFrameslastFrame (void) const
 Return an StkFrames reference to the last output sample frame.
 
- Public Member Functions inherited from stk::Stk
void ignoreSampleRateChange (bool ignore=true)
 A function to enable/disable the automatic updating of class data when the STK sample rate changes. More...
 

Additional Inherited Members

- Static Public Member Functions inherited from stk::Stk
static StkFloat sampleRate (void)
 Static method that returns the current STK sample rate.
 
static void setSampleRate (StkFloat rate)
 Static method that sets the STK sample rate. More...
 
static std::string rawwavePath (void)
 Static method that returns the current rawwave path.
 
static void setRawwavePath (std::string path)
 Static method that sets the STK rawwave path.
 
static void swap16 (unsigned char *ptr)
 Static method that byte-swaps a 16-bit data type.
 
static void swap32 (unsigned char *ptr)
 Static method that byte-swaps a 32-bit data type.
 
static void swap64 (unsigned char *ptr)
 Static method that byte-swaps a 64-bit data type.
 
static void sleep (unsigned long milliseconds)
 Static cross-platform method to sleep for a number of milliseconds.
 
static bool inRange (StkFloat value, StkFloat min, StkFloat max)
 Static method to check whether a value is within a specified range.
 
static void handleError (const char *message, StkError::Type type)
 Static function for error reporting and handling using c-strings.
 
static void handleError (std::string message, StkError::Type type)
 Static function for error reporting and handling using c++ strings.
 
static void showWarnings (bool status)
 Toggle display of WARNING and STATUS messages.
 
static void printErrors (bool status)
 Toggle display of error messages before throwing exceptions.
 
- Static Public Attributes inherited from stk::Stk
static const StkFormat STK_SINT8
 
static const StkFormat STK_SINT16
 
static const StkFormat STK_SINT24
 
static const StkFormat STK_SINT32
 
static const StkFormat STK_FLOAT32
 
static const StkFormat STK_FLOAT64
 
- Protected Member Functions inherited from stk::Stk
 Stk (void)
 Default constructor.
 
virtual ~Stk (void)
 Class destructor.
 
void addSampleRateAlert (Stk *ptr)
 Add class pointer to list for sample rate change notification.
 
void removeSampleRateAlert (Stk *ptr)
 Remove class pointer from list for sample rate change notification.
 
void handleError (StkError::Type type) const
 Internal function for error reporting that assumes message in oStream_ variable.
 

Detailed Description

STK two-pole filter class.

This class implements a two-pole digital filter. A method is provided for creating a resonance in the frequency response while maintaining a nearly constant filter gain.

by Perry R. Cook and Gary P. Scavone, 1995–2014.

Member Function Documentation

void stk::TwoPole::setResonance ( StkFloat  frequency,
StkFloat  radius,
bool  normalize = false 
)

Sets the filter coefficients for a resonance at frequency (in Hz).

This method determines the filter coefficients corresponding to two complex-conjugate poles with the given frequency (in Hz) and radius from the z-plane origin. If normalize is true, the coefficients are then normalized to produce unity gain at frequency (the actual maximum filter gain tends to be slightly greater than unity when radius is not close to one). The resulting filter frequency response has a resonance at the given frequency. The closer the poles are to the unit-circle (radius close to one), the narrower the resulting resonance width. An unstable filter will result for radius >= 1.0. The frequency value should be between zero and half the sample rate. For a better resonance filter, use a BiQuad filter.

See Also
BiQuad filter class
StkFrames & stk::TwoPole::tick ( StkFrames frames,
unsigned int  channel = 0 
)
inlinevirtual

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.

107 {
108 #if defined(_STK_DEBUG_)
109  if ( channel >= frames.channels() ) {
110  oStream_ << "TwoPole::tick(): channel and StkFrames arguments are incompatible!";
111  handleError( StkError::FUNCTION_ARGUMENT );
112  }
113 #endif
114 
115  StkFloat *samples = &frames[channel];
116  unsigned int hop = frames.channels();
117  for ( unsigned int i=0; i<frames.frames(); i++, samples += hop ) {
118  inputs_[0] = gain_ * *samples;
119  *samples = b_[0] * inputs_[0] - a_[1] * outputs_[1] - a_[2] * outputs_[2];
120  outputs_[2] = outputs_[1];
121  outputs_[1] = *samples;
122  }
123 
124  lastFrame_[0] = outputs_[1];
125  return frames;
126 }
StkFrames & stk::TwoPole::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.

129 {
130 #if defined(_STK_DEBUG_)
131  if ( iChannel >= iFrames.channels() || oChannel >= oFrames.channels() ) {
132  oStream_ << "TwoPole::tick(): channel and StkFrames arguments are incompatible!";
133  handleError( StkError::FUNCTION_ARGUMENT );
134  }
135 #endif
136 
137  StkFloat *iSamples = &iFrames[iChannel];
138  StkFloat *oSamples = &oFrames[oChannel];
139  unsigned int iHop = iFrames.channels(), oHop = oFrames.channels();
140  for ( unsigned int i=0; i<iFrames.frames(); i++, iSamples += iHop, oSamples += oHop ) {
141  inputs_[0] = gain_ * *iSamples;
142  *oSamples = b_[0] * inputs_[0] - a_[1] * outputs_[1] - a_[2] * outputs_[2];
143  outputs_[2] = outputs_[1];
144  outputs_[1] = *oSamples;
145  }
146 
147  lastFrame_[0] = outputs_[1];
148  return iFrames;
149 }

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

The Synthesis ToolKit in C++ (STK)
©1995--2014 Perry R. Cook and Gary P. Scavone. All Rights Reserved.