gri_agc2_ff.h

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/* -*- c++ -*- */
/*
 * Copyright 2002,2006 Free Software Foundation, Inc.
 * 
 * This file is part of GNU Radio
 * 
 * GNU Radio is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 3, or (at your option)
 * any later version.
 * 
 * GNU Radio 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 for more details.
 * 
 * You should have received a copy of the GNU General Public License
 * along with GNU Radio; see the file COPYING.  If not, write to
 * the Free Software Foundation, Inc., 51 Franklin Street,
 * Boston, MA 02110-1301, USA.
 */

#ifndef _GRI_AGC2_FF_H_
#define _GRI_AGC2_FF_H_

#include <math.h>

/*!
 * \brief high performance Automatic Gain Control class with attack and decay rate
 *
 * Power is approximated by absolute value
 */

class gri_agc2_ff {

 public:
  gri_agc2_ff (float attack_rate = 1e-1, float decay_rate = 1e-2, float reference = 1.0, 
               float gain = 1.0, float max_gain = 0.0)
    : _attack_rate(attack_rate), _decay_rate(decay_rate), _reference(reference), 
      _gain(gain), _max_gain(max_gain) {};

  float attack_rate () const { return _attack_rate; }
  float decay_rate () const  { return _decay_rate; }
  float reference () const   { return _reference; }
  float gain () const        { return _gain;  }
  float max_gain () const    { return _max_gain; }
  
  void set_attack_rate (float rate) { _attack_rate = rate; }
  void set_decay_rate (float rate) { _decay_rate = rate; }
  void set_reference (float reference) { _reference = reference; }
  void set_gain (float gain) { _gain = gain; }
  void set_max_gain (float max_gain) { _max_gain = max_gain; }
  
  float scale (float input){
    float output = input * _gain;
    
    float tmp = (fabsf(output)) - _reference;
    float rate = _decay_rate;
    if(fabsf(tmp) > _gain)
        rate = _attack_rate;
    _gain -= tmp*rate;

#if 0
    fprintf(stdout, "rate = %f\ttmp = %f\t gain = %f\n", rate, tmp, _gain);
#endif

    // Not sure about this
    if (_gain < 0.0)
        _gain = 10e-5;

    if (_max_gain > 0.0 && _gain > _max_gain)
       _gain = _max_gain;
    return output;
  }

  void scaleN (float output[], const float input[], unsigned n){
    for (unsigned i = 0; i < n; i++)
      output[i] = scale (input[i]);
  }
  
 protected:
  float _attack_rate;           // attack_rate for fast changing signals
  float _decay_rate;            // decay rate for slow changing signals
  float _reference;             // reference value
  float _gain;                  // current gain
  float _max_gain;              // maximum gain
};

#endif /* _GRI_AGC2_FF_H_ */