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Version 4.4.0
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Gary Scavone
committed by
Stephen Sinclair
Stephen Sinclair
parent
d199342e86
commit
eccd8c9981
138
include/Filter.h
138
include/Filter.h
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/***************************************************/
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/*! \class Filter
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\brief STK filter class.
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This class implements a generic structure that
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can be used to create a wide range of filters.
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It can function independently or be subclassed
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to provide more specific controls based on a
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particular filter type.
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In particular, this class implements the standard
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difference equation:
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a[0]*y[n] = b[0]*x[n] + ... + b[nb]*x[n-nb] -
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a[1]*y[n-1] - ... - a[na]*y[n-na]
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If a[0] is not equal to 1, the filter coeffcients
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are normalized by a[0].
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The \e gain parameter is applied at the filter
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input and does not affect the coefficient values.
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The default gain value is 1.0. This structure
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results in one extra multiply per computed sample,
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but allows easy control of the overall filter gain.
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by Perry R. Cook and Gary P. Scavone, 1995 - 2007.
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*/
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/***************************************************/
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#ifndef STK_FILTER_H
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#define STK_FILTER_H
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#include "Stk.h"
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#include <vector>
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namespace stk {
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/***************************************************/
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/*! \class Filter
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\brief STK abstract filter class.
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This class provides limited common functionality for STK digital
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filter subclasses. It is general enough to support both
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monophonic and polyphonic input/output classes.
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by Perry R. Cook and Gary P. Scavone, 1995 - 2009.
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*/
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/***************************************************/
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class Filter : public Stk
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{
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public:
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//! Default constructor creates a zero-order pass-through "filter".
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Filter(void);
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//! Class constructor.
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Filter( void ) { gain_ = 1.0; channelsIn_ = 1; lastFrame_.resize( 1, 1, 0.0 ); };
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//! Overloaded constructor which takes filter coefficients.
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/*!
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An StkError can be thrown if either of the coefficient vector
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sizes is zero, or if the a[0] coefficient is equal to zero.
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*/
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Filter( std::vector<StkFloat> &bCoefficients, std::vector<StkFloat> &aCoefficients );
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//! Return the number of input channels for the class.
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unsigned int channelsIn( void ) const { return channelsIn_; };
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//! Class destructor.
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virtual ~Filter(void);
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//! Return the number of output channels for the class.
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unsigned int channelsOut( void ) const { return lastFrame_.channels(); };
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//! Sets all internal states of the filter to zero.
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void clear(void);
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//! Set filter coefficients.
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/*!
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An StkError can be thrown if either of the coefficient vector
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sizes is zero, or if the a[0] coefficient is equal to zero. If
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a[0] is not equal to 1, the filter coeffcients are normalized by
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a[0]. The internal state of the filter is not cleared unless the
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\e clearState flag is \c true.
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*/
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void setCoefficients( std::vector<StkFloat> &bCoefficients, std::vector<StkFloat> &aCoefficients, bool clearState = false );
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//! Set numerator coefficients.
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/*!
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An StkError can be thrown if coefficient vector is empty. Any
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previously set denominator coefficients are left unaffected. Note
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that the default constructor sets the single denominator
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coefficient a[0] to 1.0. The internal state of the filter is not
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cleared unless the \e clearState flag is \c true.
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*/
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void setNumerator( std::vector<StkFloat> &bCoefficients, bool clearState = false );
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//! Set denominator coefficients.
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/*!
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An StkError can be thrown if the coefficient vector is empty or
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if the a[0] coefficient is equal to zero. Previously set
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numerator coefficients are unaffected unless a[0] is not equal to
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1, in which case all coeffcients are normalized by a[0]. Note
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that the default constructor sets the single numerator coefficient
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b[0] to 1.0. The internal state of the filter is not cleared
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unless the \e clearState flag is \c true.
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*/
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void setDenominator( std::vector<StkFloat> &aCoefficients, bool clearState = false );
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//! Clears all internal states of the filter.
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virtual void clear( void );
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//! Set the filter gain.
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/*!
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The gain is applied at the filter input and does not affect the
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coefficient values. The default gain value is 1.0.
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*/
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virtual void setGain(StkFloat gain);
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void setGain( StkFloat gain ) { gain_ = gain; };
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//! Return the current filter gain.
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virtual StkFloat getGain(void) const;
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StkFloat getGain( void ) const { return gain_; };
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//! Return the last computed output value.
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virtual StkFloat lastOut(void) const;
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//! Input one sample to the filter and return one output.
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virtual StkFloat tick( StkFloat input );
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//! Return an StkFrames reference to the last output sample frame.
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const StkFrames& lastFrame( void ) const { return lastFrame_; };
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//! Take a channel of the StkFrames object as inputs to the filter and replace with corresponding outputs.
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/*!
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The \c channel argument should be zero or greater (the first
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channel is specified by 0). An StkError will be thrown if the \c
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channel argument is equal to or greater than the number of
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channels in the StkFrames object.
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The StkFrames argument reference is returned. The \c channel
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argument must be less than the number of channels in the
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StkFrames argument (the first channel is specified by 0).
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However, range checking is only performed if _STK_DEBUG_ is
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defined during compilation, in which case an out-of-range value
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will trigger an StkError exception.
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*/
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virtual StkFrames& tick( StkFrames& frames, unsigned int channel = 0 );
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virtual StkFrames& tick( StkFrames& frames, unsigned int channel = 0 ) = 0;
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protected:
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unsigned int channelsIn_;
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StkFrames lastFrame_;
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StkFloat gain_;
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std::vector<StkFloat> b_;
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std::vector<StkFloat> a_;
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std::vector<StkFloat> outputs_;
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std::vector<StkFloat> inputs_;
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StkFrames outputs_;
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StkFrames inputs_;
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};
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inline void Filter :: clear( void )
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{
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unsigned int i;
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for ( i=0; i<inputs_.size(); i++ )
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inputs_[i] = 0.0;
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for ( i=0; i<outputs_.size(); i++ )
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outputs_[i] = 0.0;
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for ( i=0; i<lastFrame_.size(); i++ )
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lastFrame_[i] = 0.0;
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}
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} // stk namespace
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#endif
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