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https://github.com/thestk/stk
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79 lines
2.4 KiB
C++
79 lines
2.4 KiB
C++
/***************************************************/
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/*! \class TwoPole
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\brief STK two-pole filter class.
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This protected Filter subclass implements
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a two-pole digital filter. A method is
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provided for creating a resonance in the
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frequency response while maintaining a nearly
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constant filter gain.
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by Perry R. Cook and Gary P. Scavone, 1995 - 2002.
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*/
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/***************************************************/
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#if !defined(__TWOPOLE_H)
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#define __TWOPOLE_H
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#include "Filter.h"
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class TwoPole : protected Filter
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{
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public:
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//! Default constructor creates a second-order pass-through filter.
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TwoPole();
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//! Class destructor.
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~TwoPole();
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//! Clears the internal states of the filter.
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void clear(void);
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//! Set the b[0] coefficient value.
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void setB0(MY_FLOAT b0);
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//! Set the a[1] coefficient value.
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void setA1(MY_FLOAT a1);
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//! Set the a[2] coefficient value.
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void setA2(MY_FLOAT a2);
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//! Sets the filter coefficients for a resonance at \e frequency (in Hz).
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/*!
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This method determines the filter coefficients corresponding to
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two complex-conjugate poles with the given \e frequency (in Hz)
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and \e radius from the z-plane origin. If \e normalize is true,
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the coefficients are then normalized to produce unity gain at \e
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frequency (the actual maximum filter gain tends to be slightly
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greater than unity when \e radius is not close to one). The
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resulting filter frequency response has a resonance at the given
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\e frequency. The closer the poles are to the unit-circle (\e
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radius close to one), the narrower the resulting resonance width.
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An unstable filter will result for \e radius >= 1.0. For a better
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resonance filter, use a BiQuad filter. \sa BiQuad filter class
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*/
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void setResonance(MY_FLOAT frequency, MY_FLOAT radius, bool normalize = FALSE);
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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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void setGain(MY_FLOAT theGain);
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//! Return the current filter gain.
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MY_FLOAT getGain(void) const;
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//! Return the last computed output value.
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MY_FLOAT lastOut(void) const;
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//! Input one sample to the filter and return one output.
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MY_FLOAT tick(MY_FLOAT sample);
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//! Input \e vectorSize samples to the filter and return an equal number of outputs in \e vector.
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MY_FLOAT *tick(MY_FLOAT *vector, unsigned int vectorSize);
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};
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#endif
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