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https://github.com/cookiengineer/audacity
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118 lines
3.5 KiB
C++
118 lines
3.5 KiB
C++
/***************************************************/
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/*! \class BiQuad
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\brief STK biquad (two-pole, two-zero) filter class.
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This protected Filter subclass implements a
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two-pole, two-zero digital filter. A method
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is provided for creating a resonance in the
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frequency response while maintaining a constant
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filter gain.
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by Perry R. Cook and Gary P. Scavone, 1995 - 2005.
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*/
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/***************************************************/
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#ifndef STK_BIQUAD_H
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#define STK_BIQUAD_H
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#include "Filter.h"
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namespace Nyq
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{
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class BiQuad : 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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BiQuad();
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//! Class destructor.
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virtual ~BiQuad();
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//! Clears all 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(StkFloat b0);
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//! Set the b[1] coefficient value.
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void setB1(StkFloat b1);
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//! Set the b[2] coefficient value.
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void setB2(StkFloat b2);
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//! Set the a[1] coefficient value.
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void setA1(StkFloat a1);
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//! Set the a[2] coefficient value.
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void setA2(StkFloat 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 filter zeros are placed at z = 1, z = -1, and the coefficients
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are then normalized to produce a constant unity peak gain
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(independent of the filter \e gain parameter). The resulting
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filter frequency response has a resonance at the given \e
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frequency. The closer the poles are to the unit-circle (\e radius
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close to one), the narrower the resulting resonance width.
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*/
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void setResonance(StkFloat frequency, StkFloat radius, bool normalize = false);
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//! Set the filter coefficients for a notch 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 zeros with the given \e frequency (in Hz)
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and \e radius from the z-plane origin. No filter normalization
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is attempted.
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*/
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void setNotch(StkFloat frequency, StkFloat radius);
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//! Sets the filter zeroes for equal resonance gain.
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/*!
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When using the filter as a resonator, zeroes places at z = 1, z
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= -1 will result in a constant gain at resonance of 1 / (1 - R),
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where R is the pole radius setting.
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*/
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void setEqualGainZeroes();
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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(StkFloat gain);
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//! Return the current filter gain.
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StkFloat getGain(void) const;
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//! Return the last computed output value.
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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 sample);
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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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*/
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virtual StkFrames& tick( StkFrames& frames, unsigned int channel = 0 );
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protected:
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// This function must be implemented in all subclasses. It is used
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// to get around a C++ problem with overloaded virtual functions.
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virtual StkFloat computeSample( StkFloat input );
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};
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} // namespace Nyq
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#endif
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