delaya.h

Mobile STK for Symbian OS V0.1

/***************************************************/
/*! \class DelayA
    \brief STK allpass interpolating delay line class.

    This Delay subclass implements a fractional-length digital
    delay-line using a first-order allpass filter.  A fixed maximum
    length of 4095 and a delay of 0.5 is set using the default
    constructor.  Alternatively, the delay and maximum length can be
    set during instantiation with an overloaded constructor.

    An allpass filter has unity magnitude gain but variable phase
    delay properties, making it useful in achieving fractional delays
    without affecting a signal's frequency magnitude response.  In
    order to achieve a maximally flat phase delay response, the
    minimum delay possible in this implementation is limited to a
    value of 0.5.

    by Perry R. Cook and Gary P. Scavone, 1995 - 2005.
*/
/***************************************************/

#ifndef STK_DELAYA_H
#define STK_DELAYA_H

#include "Delay.h"

class DelayA : public Delay
{
public:

  //! Default constructor creates a delay-line with maximum length of 4095 samples and zero delay.
  DelayA();

  //! Overloaded constructor which specifies the current and maximum delay-line lengths.
  /*!
    An StkError will be thrown if the delay parameter is less than
    zero, the maximum delay parameter is less than one, or the delay
    parameter is greater than the maxDelay value.
   */  
  DelayA(StkFloat delay, unsigned long maxDelay);

  //! Class destructor.
  ~DelayA();

  //! Clears the internal state of the delay line.
  void clear();

  //! Set the delay-line length
  /*!
    The valid range for \e theDelay is from 0.5 to the maximum delay-line length.
  */
  void setDelay(StkFloat delay);

  //! Return the current delay-line length.
  StkFloat getDelay(void) const;

  //! Return the value which will be output by the next call to tick().
  /*!
    This method is valid only for delay settings greater than zero!
   */
  StkFloat nextOut(void);

protected:  

  StkFloat computeSample( StkFloat input );

  StkFloat alpha_;
  StkFloat coeff_;
  StkFloat apInput_;
  StkFloat nextOutput_;
  bool doNextOut_;
};

#endif