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stk::Iir Class Reference

STK general infinite impulse response filter class. More...

#include <Iir.h>

Inheritance diagram for stk::Iir:
stk::Filter stk::Stk

Public Member Functions

 Iir (void)
 Default constructor creates a zero-order pass-through "filter".
 
 Iir (std::vector< StkFloat > &bCoefficients, std::vector< StkFloat > &aCoefficients)
 Overloaded constructor which takes filter coefficients. More...
 
 ~Iir (void)
 Class destructor.
 
void setCoefficients (std::vector< StkFloat > &bCoefficients, std::vector< StkFloat > &aCoefficients, bool clearState=false)
 Set filter coefficients. More...
 
void setNumerator (std::vector< StkFloat > &bCoefficients, bool clearState=false)
 Set numerator coefficients. More...
 
void setDenominator (std::vector< StkFloat > &aCoefficients, bool clearState=false)
 Set denominator coefficients. 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.
 
virtual void sampleRateChanged (StkFloat newRate, StkFloat oldRate)
 This function should be implemented in subclasses that depend on the sample rate.
 
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 general infinite impulse response filter class.

This class provides a generic digital filter structure that can be used to implement IIR filters. For filters containing only feedforward terms, the Fir class is slightly more efficient.

In particular, this class implements the standard difference equation:

a[0]*y[n] = b[0]*x[n] + ... + b[nb]*x[n-nb] - a[1]*y[n-1] - ... - a[na]*y[n-na]

If a[0] is not equal to 1, the filter coeffcients are normalized by a[0].

The gain parameter is applied at the filter input and does not affect the coefficient values. The default gain value is 1.0. This structure results in one extra multiply per computed sample, but allows easy control of the overall filter gain.

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

Constructor & Destructor Documentation

stk::Iir::Iir ( std::vector< StkFloat > &  bCoefficients,
std::vector< StkFloat > &  aCoefficients 
)

Overloaded constructor which takes filter coefficients.

An StkError can be thrown if either of the coefficient vector sizes is zero, or if the a[0] coefficient is equal to zero.

Member Function Documentation

void stk::Iir::setCoefficients ( std::vector< StkFloat > &  bCoefficients,
std::vector< StkFloat > &  aCoefficients,
bool  clearState = false 
)

Set filter coefficients.

An StkError can be thrown if either of the coefficient vector sizes is zero, or if the a[0] coefficient is equal to zero. If a[0] is not equal to 1, the filter coeffcients are normalized by a[0]. The internal state of the filter is not cleared unless the clearState flag is true.

void stk::Iir::setNumerator ( std::vector< StkFloat > &  bCoefficients,
bool  clearState = false 
)

Set numerator coefficients.

An StkError can be thrown if coefficient vector is empty. Any previously set denominator coefficients are left unaffected. Note that the default constructor sets the single denominator coefficient a[0] to 1.0. The internal state of the filter is not cleared unless the clearState flag is true.

void stk::Iir::setDenominator ( std::vector< StkFloat > &  aCoefficients,
bool  clearState = false 
)

Set denominator coefficients.

An StkError can be thrown if the coefficient vector is empty or if the a[0] coefficient is equal to zero. Previously set numerator coefficients are unaffected unless a[0] is not equal to 1, in which case all coeffcients are normalized by a[0]. Note that the default constructor sets the single numerator coefficient b[0] to 1.0. The internal state of the filter is not cleared unless the clearState flag is true.

StkFrames & stk::Iir::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.

136 {
137 #if defined(_STK_DEBUG_)
138  if ( channel >= frames.channels() ) {
139  oStream_ << "Iir::tick(): channel and StkFrames arguments are incompatible!";
140  handleError( StkError::FUNCTION_ARGUMENT );
141  }
142 #endif
143 
144  StkFloat *samples = &frames[channel];
145  size_t i;
146  unsigned int hop = frames.channels();
147  for ( unsigned int j=0; j<frames.frames(); j++, samples += hop ) {
148  outputs_[0] = 0.0;
149  inputs_[0] = gain_ * *samples;
150  for ( i=b_.size()-1; i>0; i-- ) {
151  outputs_[0] += b_[i] * inputs_[i];
152  inputs_[i] = inputs_[i-1];
153  }
154  outputs_[0] += b_[0] * inputs_[0];
155 
156  for ( i=a_.size()-1; i>0; i-- ) {
157  outputs_[0] += -a_[i] * outputs_[i];
158  outputs_[i] = outputs_[i-1];
159  }
160 
161  *samples = outputs_[0];
162  }
163 
164  lastFrame_[0] = *(samples-hop);
165  return frames;
166 }
StkFrames & stk::Iir::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.

169 {
170 #if defined(_STK_DEBUG_)
171  if ( iChannel >= iFrames.channels() || oChannel >= oFrames.channels() ) {
172  oStream_ << "Iir::tick(): channel and StkFrames arguments are incompatible!";
173  handleError( StkError::FUNCTION_ARGUMENT );
174  }
175 #endif
176 
177  StkFloat *iSamples = &iFrames[iChannel];
178  StkFloat *oSamples = &oFrames[oChannel];
179  size_t i;
180  unsigned int iHop = iFrames.channels(), oHop = oFrames.channels();
181  for ( unsigned int j=0; j<iFrames.frames(); j++, iSamples += iHop, oSamples += oHop ) {
182  outputs_[0] = 0.0;
183  inputs_[0] = gain_ * *iSamples;
184  for ( i=b_.size()-1; i>0; i-- ) {
185  outputs_[0] += b_[i] * inputs_[i];
186  inputs_[i] = inputs_[i-1];
187  }
188  outputs_[0] += b_[0] * inputs_[0];
189 
190  for ( i=a_.size()-1; i>0; i-- ) {
191  outputs_[0] += -a_[i] * outputs_[i];
192  outputs_[i] = outputs_[i-1];
193  }
194 
195  *oSamples = outputs_[0];
196  }
197 
198  lastFrame_[0] = *(oSamples-oHop);
199  return iFrames;
200 }

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.