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113 lines
3.3 KiB
C++
113 lines
3.3 KiB
C++
#ifndef STK_POLEZERO_H
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#define STK_POLEZERO_H
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#include "Filter.h"
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namespace stk {
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/***************************************************/
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/*! \class PoleZero
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\brief STK one-pole, one-zero filter class.
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This class implements a one-pole, one-zero digital filter. A
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method is provided for creating an allpass filter with a given
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coefficient. Another method is provided to create a DC blocking
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filter.
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by Perry R. Cook and Gary P. Scavone, 1995-2012.
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*/
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/***************************************************/
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class PoleZero : public Filter
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{
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public:
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//! Default constructor creates a first-order pass-through filter.
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PoleZero();
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//! Class destructor.
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~PoleZero();
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//! Set the b[0] coefficient value.
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void setB0( StkFloat b0 ) { b_[0] = b0; };
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//! Set the b[1] coefficient value.
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void setB1( StkFloat b1 ) { b_[1] = b1; };
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//! Set the a[1] coefficient value.
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void setA1( StkFloat a1 ) { a_[1] = a1; };
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//! Set all filter coefficients.
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void setCoefficients( StkFloat b0, StkFloat b1, StkFloat a1, bool clearState = false );
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//! Set the filter for allpass behavior using \e coefficient.
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/*!
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This method uses \e coefficient to create an allpass filter,
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which has unity gain at all frequencies. Note that the
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\e coefficient magnitude must be less than one to maintain
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filter stability.
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*/
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void setAllpass( StkFloat coefficient );
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//! Create a DC blocking filter with the given pole position in the z-plane.
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/*!
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This method sets the given pole position, together with a zero
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at z=1, to create a DC blocking filter. The argument magnitude
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should be close to (but less than) one to minimize low-frequency
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attenuation.
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*/
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void setBlockZero( StkFloat thePole = 0.99 );
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//! Return the last computed output value.
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StkFloat lastOut( void ) const { return lastFrame_[0]; };
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//! Input one sample to the filter and return one output.
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StkFloat tick( StkFloat input );
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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 must be less than the number of
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channels in the StkFrames argument (the first channel is specified
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by 0). However, range checking is only performed if _STK_DEBUG_
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is 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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StkFrames& tick( StkFrames& frames, unsigned int channel = 0 );
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};
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inline StkFloat PoleZero :: tick( StkFloat input )
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{
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inputs_[0] = gain_ * input;
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lastFrame_[0] = b_[0] * inputs_[0] + b_[1] * inputs_[1] - a_[1] * outputs_[1];
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inputs_[1] = inputs_[0];
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outputs_[1] = lastFrame_[0];
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return lastFrame_[0];
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}
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inline StkFrames& PoleZero :: tick( StkFrames& frames, unsigned int channel )
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{
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#if defined(_STK_DEBUG_)
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if ( channel >= frames.channels() ) {
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oStream_ << "PoleZero::tick(): channel and StkFrames arguments are incompatible!";
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handleError( StkError::FUNCTION_ARGUMENT );
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}
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#endif
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StkFloat *samples = &frames[channel];
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unsigned int hop = frames.channels();
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for ( unsigned int i=0; i<frames.frames(); i++, samples += hop ) {
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inputs_[0] = gain_ * *samples;
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*samples = b_[0] * inputs_[0] + b_[1] * inputs_[1] - a_[1] * outputs_[1];
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inputs_[1] = inputs_[0];
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outputs_[1] = *samples;
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}
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lastFrame_[0] = outputs_[1];
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return frames;
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}
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} // stk namespace
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#endif
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