Move library tree where it belongs

lib-src/libnyquist/nyquist/nyqstk/include/BiQuad.h

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+/***************************************************/
+/*! \class BiQuad
+    \brief STK biquad (two-pole, two-zero) filter class.
+
+    This protected Filter subclass implements a
+    two-pole, two-zero digital filter.  A method
+    is provided for creating a resonance in the
+    frequency response while maintaining a constant
+    filter gain.
+
+    by Perry R. Cook and Gary P. Scavone, 1995 - 2005.
+*/
+/***************************************************/
+
+#ifndef STK_BIQUAD_H
+#define STK_BIQUAD_H
+
+#include "Filter.h"
+
+namespace Nyq
+{
+
+class BiQuad : protected Filter
+{
+public:
+
+  //! Default constructor creates a second-order pass-through filter.
+  BiQuad();
+
+  //! Class destructor.
+  virtual ~BiQuad();
+
+  //! Clears all internal states of the filter.
+  void clear(void);
+
+  //! Set the b[0] coefficient value.
+  void setB0(StkFloat b0);
+
+  //! Set the b[1] coefficient value.
+  void setB1(StkFloat b1);
+
+  //! Set the b[2] coefficient value.
+  void setB2(StkFloat b2);
+
+  //! Set the a[1] coefficient value.
+  void setA1(StkFloat a1);
+
+  //! Set the a[2] coefficient value.
+  void setA2(StkFloat a2);
+
+  //! Sets the filter coefficients for a resonance at \e frequency (in Hz).
+  /*!
+    This method determines the filter coefficients corresponding to
+    two complex-conjugate poles with the given \e frequency (in Hz)
+    and \e radius from the z-plane origin.  If \e normalize is true,
+    the filter zeros are placed at z = 1, z = -1, and the coefficients
+    are then normalized to produce a constant unity peak gain
+    (independent of the filter \e gain parameter).  The resulting
+    filter frequency response has a resonance at the given \e
+    frequency.  The closer the poles are to the unit-circle (\e radius
+    close to one), the narrower the resulting resonance width.
+  */
+  void setResonance(StkFloat frequency, StkFloat radius, bool normalize = false);
+
+  //! Set the filter coefficients for a notch at \e frequency (in Hz).
+  /*!
+    This method determines the filter coefficients corresponding to
+    two complex-conjugate zeros with the given \e frequency (in Hz)
+    and \e radius from the z-plane origin.  No filter normalization
+    is attempted.
+  */
+  void setNotch(StkFloat frequency, StkFloat radius);
+
+  //! Sets the filter zeroes for equal resonance gain.
+  /*!
+    When using the filter as a resonator, zeroes places at z = 1, z
+    = -1 will result in a constant gain at resonance of 1 / (1 - R),
+    where R is the pole radius setting.
+
+  */
+  void setEqualGainZeroes();
+
+  //! Set the filter gain.
+  /*!
+    The gain is applied at the filter input and does not affect the
+    coefficient values.  The default gain value is 1.0.
+   */
+  void setGain(StkFloat gain);
+
+  //! Return the current filter gain.
+  StkFloat getGain(void) const;
+
+  //! Return the last computed output value.
+  StkFloat lastOut(void) const;
+
+  //! Input one sample to the filter and return one output.
+  virtual StkFloat tick(StkFloat sample);
+
+  //! Take a channel of the StkFrames object as inputs to the filter and replace with corresponding outputs.
+  /*!
+    The \c channel argument should be zero or greater (the first
+    channel is specified by 0).  An StkError will be thrown if the \c
+    channel argument is equal to or greater than the number of
+    channels in the StkFrames object.
+  */
+  virtual StkFrames& tick( StkFrames& frames, unsigned int channel = 0 );
+
+ protected:
+
+  // This function must be implemented in all subclasses. It is used
+  // to get around a C++ problem with overloaded virtual functions.
+  virtual StkFloat computeSample( StkFloat input );
+};
+
+} // namespace Nyq
+
+#endif