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AnalogFilter.h

/*
  ZynAddSubFX - a software synthesizer
 
  Analog Filter.h - Several analog filters (lowpass, highpass...)
  Copyright (C) 2002-2005 Nasca Octavian Paul
  Author: Nasca Octavian Paul

  Modified for rakarrack by Josep Andreu

  This program is free software; you can redistribute it and/or modify
  it under the terms of version 2 of the GNU General Public License 
  as published by the Free Software Foundation.

  This program is distributed in the hope that it will be useful,
  but WITHOUT ANY WARRANTY; without even the implied warranty of
  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  GNU General Public License (version 2) for more details.

  You should have received a copy of the GNU General Public License (version 2)
  along with this program; if not, write to the Free Software Foundation,
  Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307 USA

*/

#ifndef ANALOG_FILTER_H
#define ANALOG_FILTER_H

#include "global.h"
#include "Filter_.h"

#define REALTYPE float
#define MAX_FILTER_STAGES 5

class AnalogFilter:public Filter_
{
public:
  AnalogFilter (unsigned char Ftype, REALTYPE Ffreq, REALTYPE Fq,
            unsigned char Fstages);
   ~AnalogFilter ();
  void filterout (REALTYPE * smp);
  void setfreq (REALTYPE frequency);
  void setfreq_and_q (REALTYPE frequency, REALTYPE q_);
  void setq (REALTYPE q_);

  void settype (int type_);
  void setgain (REALTYPE dBgain);
  void setstages (int stages_);
  void cleanup ();

  REALTYPE H (REALTYPE freq); //Obtains the response for a given frequency

private:
  struct fstage
  {
    REALTYPE c1, c2;
  } x[MAX_FILTER_STAGES + 1], y[MAX_FILTER_STAGES + 1],
    oldx[MAX_FILTER_STAGES + 1], oldy[MAX_FILTER_STAGES + 1];

  void singlefilterout (REALTYPE * smp, fstage & x, fstage & y, REALTYPE * c,
                  REALTYPE * d);
  void computefiltercoefs ();
  int type;             //The type of the filter (LPF1,HPF1,LPF2,HPF2...)
  int stages;                 //how many times the filter is applied (0->1,1->2,etc.)
  REALTYPE freq;        //Frequency given in Hz
  REALTYPE q;                 //Q factor (resonance or Q factor)
  REALTYPE gain;        //the gain of the filter (if are shelf/peak) filters

  int order;                  //the order of the filter (number of poles)

  REALTYPE c[3], d[3];        //coefficients

  REALTYPE oldc[3], oldd[3];  //old coefficients(used only if some filter paremeters changes very fast, and it needs interpolation)

  REALTYPE xd[3], yd[3];      //used if the filter is applied more times

  int needsinterpolation, firsttime;
  int abovenq;                //this is 1 if the frequency is above the nyquist
  int oldabovenq;       //if the last time was above nyquist (used to see if it needs interpolation)
};


#endif

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