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- #ifndef STK_IIR_H
- #define STK_IIR_H
-
- #include "Filter.h"
-
- namespace stk {
-
- /***************************************************/
- /*! \class Iir
- \brief 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 \e 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--2017.
- */
- /***************************************************/
-
- class Iir : public Filter
- {
- public:
- //! Default constructor creates a zero-order pass-through "filter".
- Iir( void );
-
- //! 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.
- */
- Iir( std::vector<StkFloat> &bCoefficients, std::vector<StkFloat> &aCoefficients );
-
- //! Class destructor.
- ~Iir( void );
-
- //! 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
- \e clearState flag is \c true.
- */
- void setCoefficients( std::vector<StkFloat> &bCoefficients, std::vector<StkFloat> &aCoefficients, 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 \e clearState flag is \c true.
- */
- void setNumerator( std::vector<StkFloat> &bCoefficients, 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 \e clearState flag is \c true.
- */
- void setDenominator( std::vector<StkFloat> &aCoefficients, bool clearState = false );
-
- //! Return the last computed output value.
- StkFloat lastOut( void ) const { return lastFrame_[0]; };
-
- //! Input one sample to the filter and return one output.
- StkFloat tick( StkFloat input );
-
- //! Take a channel of the StkFrames object as inputs to the filter and replace with corresponding outputs.
- /*!
- The StkFrames argument reference is returned. The \c 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.
- */
- StkFrames& tick( StkFrames& frames, unsigned int channel = 0 );
-
- //! Take a channel of the \c iFrames object as inputs to the filter and write outputs to the \c oFrames object.
- /*!
- The \c 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.
- */
- StkFrames& tick( StkFrames& iFrames, StkFrames &oFrames, unsigned int iChannel = 0, unsigned int oChannel = 0 );
-
- protected:
-
- };
-
- inline StkFloat Iir :: tick( StkFloat input )
- {
- size_t i;
-
- outputs_[0] = 0.0;
- inputs_[0] = gain_ * input;
- for ( i=b_.size()-1; i>0; i-- ) {
- outputs_[0] += b_[i] * inputs_[i];
- inputs_[i] = inputs_[i-1];
- }
- outputs_[0] += b_[0] * inputs_[0];
-
- for ( i=a_.size()-1; i>0; i-- ) {
- outputs_[0] += -a_[i] * outputs_[i];
- outputs_[i] = outputs_[i-1];
- }
-
- lastFrame_[0] = outputs_[0];
- return lastFrame_[0];
- }
-
- inline StkFrames& Iir :: tick( StkFrames& frames, unsigned int channel )
- {
- #if defined(_STK_DEBUG_)
- if ( channel >= frames.channels() ) {
- oStream_ << "Iir::tick(): channel and StkFrames arguments are incompatible!";
- handleError( StkError::FUNCTION_ARGUMENT );
- }
- #endif
-
- StkFloat *samples = &frames[channel];
- size_t i;
- unsigned int hop = frames.channels();
- for ( unsigned int j=0; j<frames.frames(); j++, samples += hop ) {
- outputs_[0] = 0.0;
- inputs_[0] = gain_ * *samples;
- for ( i=b_.size()-1; i>0; i-- ) {
- outputs_[0] += b_[i] * inputs_[i];
- inputs_[i] = inputs_[i-1];
- }
- outputs_[0] += b_[0] * inputs_[0];
-
- for ( i=a_.size()-1; i>0; i-- ) {
- outputs_[0] += -a_[i] * outputs_[i];
- outputs_[i] = outputs_[i-1];
- }
-
- *samples = outputs_[0];
- }
-
- lastFrame_[0] = *(samples-hop);
- return frames;
- }
-
- inline StkFrames& Iir :: tick( StkFrames& iFrames, StkFrames& oFrames, unsigned int iChannel, unsigned int oChannel )
- {
- #if defined(_STK_DEBUG_)
- if ( iChannel >= iFrames.channels() || oChannel >= oFrames.channels() ) {
- oStream_ << "Iir::tick(): channel and StkFrames arguments are incompatible!";
- handleError( StkError::FUNCTION_ARGUMENT );
- }
- #endif
-
- StkFloat *iSamples = &iFrames[iChannel];
- StkFloat *oSamples = &oFrames[oChannel];
- size_t i;
- unsigned int iHop = iFrames.channels(), oHop = oFrames.channels();
- for ( unsigned int j=0; j<iFrames.frames(); j++, iSamples += iHop, oSamples += oHop ) {
- outputs_[0] = 0.0;
- inputs_[0] = gain_ * *iSamples;
- for ( i=b_.size()-1; i>0; i-- ) {
- outputs_[0] += b_[i] * inputs_[i];
- inputs_[i] = inputs_[i-1];
- }
- outputs_[0] += b_[0] * inputs_[0];
-
- for ( i=a_.size()-1; i>0; i-- ) {
- outputs_[0] += -a_[i] * outputs_[i];
- outputs_[i] = outputs_[i-1];
- }
-
- *oSamples = outputs_[0];
- }
-
- lastFrame_[0] = *(oSamples-oHop);
- return iFrames;
- }
-
- } // stk namespace
-
- #endif
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