src/calf/inertia.h

   1 /* Calf DSP Library
   2  * Basic "inertia" (parameter smoothing) classes.
   3  * Copyright (C) 2001-2007 Krzysztof Foltman
   4  *
   5  * This program is free software; you can redistribute it and/or
   6  * modify it under the terms of the GNU Lesser General Public
   7  * License as published by the Free Software Foundation; either
   8  * version 2 of the License, or (at your option) any later version.
   9  *
  10  * This program is distributed in the hope that it will be useful,
  11  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  12  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  13  * Lesser General Public License for more details.
  14  *
  15  * You should have received a copy of the GNU Lesser General
  16  * Public License along with this program; if not, write to the
  17  * Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
  18  * Boston, MA 02111-1307, USA.
  19  */
  20 #ifndef __CALF_INERTIA_H
  21 #define __CALF_INERTIA_H
  22
  23 #include "primitives.h"
  24
  25 namespace dsp {
  26
  27 /// Algorithm for a constant time linear ramp
  28 class linear_ramp
  29 {
  30 public:
  31     int ramp_len;
  32     float mul, delta;
  33 public:
  34     /// Construct for given ramp length
  35     linear_ramp(int _ramp_len) {
  36         ramp_len = _ramp_len;
  37         mul = (float)(1.0f / ramp_len);
  38         delta = 0.f;
  39     }
  40     /// Change ramp length
  41     inline void set_length(int _ramp_len) {
  42         ramp_len = _ramp_len;
  43         mul = (float)(1.0f / ramp_len);
  44     }
  45     inline int length()
  46     {
  47         return ramp_len;
  48     }
  49     inline void start_ramp(float start, float end)
  50     {
  51         delta = mul * (end - start);
  52     }
  53     /// Return value after single step
  54     inline float ramp(float value)
  55     {
  56         return value + delta;
  57     }
  58     /// Return value after many steps
  59     inline float ramp_many(float value, int count)
  60     {
  61         return value + delta * count;
  62     }
  63 };
  64
  65 /// Algorithm for a constant time linear ramp
  66 class exponential_ramp
  67 {
  68 public:
  69     int ramp_len;
  70     float root, delta;
  71 public:
  72     exponential_ramp(int _ramp_len) {
  73         ramp_len = _ramp_len;
  74         root = (float)(1.0f / ramp_len);
  75         delta = 1.0;
  76     }
  77     inline void set_length(int _ramp_len) {
  78         ramp_len = _ramp_len;
  79         root = (float)(1.0f / ramp_len);
  80     }
  81     inline int length()
  82     {
  83         return ramp_len;
  84     }
  85     inline void start_ramp(float start, float end)
  86     {
  87         delta = pow(end / start, root);
  88     }
  89     /// Return value after single step
  90     inline float ramp(float value)
  91     {
  92         return value * delta;
  93     }
  94     /// Return value after many steps
  95     inline float ramp_many(float value, float count)
  96     {
  97         return value * pow(delta, count);
  98     }
  99 };
 100
 101 /// Generic inertia using ramping algorithm specified as template argument. The basic idea
 102 /// is producing smooth(ish) output for discrete input, using specified algorithm to go from
 103 /// last output value to input value. It is not the same as classic running average lowpass
 104 /// filter, because ramping time is finite and pre-determined (it calls ramp algorithm's length()
 105 /// function to obtain the expected ramp length)
 106 template<class Ramp>
 107 class inertia
 108 {
 109 public:
 110     float old_value;
 111     float value;
 112     unsigned int count;
 113     Ramp ramp;
 114
 115 public:
 116     inertia(const Ramp &_ramp, float init_value = 0.f)
 117     : ramp(_ramp)
 118     {
 119         value = old_value = init_value;
 120         count = 0;
 121     }
 122     /// Set value immediately (no inertia)
 123     void set_now(float _value)
 124     {
 125         value = old_value = _value;
 126         count = 0;
 127     }
 128     /// Set with inertia
 129     void set_inertia(float source)
 130     {
 131         if (source != old_value) {
 132             ramp.start_ramp(value, source);
 133             count = ramp.length();
 134             old_value = source;
 135         }
 136     }
 137     /// Get smoothed value of given source value
 138     inline float get(float source)
 139     {
 140         if (source != old_value) {
 141             ramp.start_ramp(value, source);
 142             count = ramp.length();
 143             old_value = source;
 144         }
 145         if (!count)
 146             return old_value;
 147         value = ramp.ramp(value);
 148         count--;
 149         if (!count) // finished ramping, set to desired value to get rid of accumulated rounding errors
 150             value = old_value;
 151         return value;
 152     }
 153     /// Get smoothed value assuming no new input
 154     inline float get()
 155     {
 156         if (!count)
 157             return old_value;
 158         value = ramp.ramp(value);
 159         count--;
 160         if (!count) // finished ramping, set to desired value to get rid of accumulated rounding errors
 161             value = old_value;
 162         return value;
 163     }
 164     /// Do one inertia step, without returning the new value and without changing destination value
 165     inline void step()
 166     {
 167         if (count) {
 168             value = ramp.ramp(value);
 169             count--;
 170             if (!count) // finished ramping, set to desired value to get rid of accumulated rounding errors
 171                 value = old_value;
 172         }
 173     }
 174     /// Do many inertia steps, without returning the new value and without changing destination value
 175     inline void step_many(unsigned int steps)
 176     {
 177         if (steps < count) {
 178             // Skip only a part of the current ramping period
 179             value = ramp.ramp_many(value, steps);
 180             count -= steps;
 181             if (!count) // finished ramping, set to desired value to get rid of accumulated rounding errors
 182                 value = old_value;
 183         }
 184         else
 185         {
 186             // The whole ramping period has been skipped, just go to destination
 187             value = old_value;
 188             count = 0;
 189         }
 190     }
 191     /// Get last smoothed value, without affecting anything
 192     inline float get_last() const
 193     {
 194         return value;
 195     }
 196     /// Is it still ramping?
 197     inline bool active() const
 198     {
 199         return count > 0;
 200     }
 201 };
 202
 203 class once_per_n
 204 {
 205 public:
 206     unsigned int frequency;
 207     unsigned int left;
 208 public:
 209     once_per_n(unsigned int _frequency)
 210     : frequency(_frequency), left(_frequency)
 211     {}
 212     inline void start()
 213     {
 214         left = frequency;
 215     }
 216     /// Set timer to "elapsed" state (elapsed() will return true during next call)
 217     inline void signal()
 218     {
 219         left = 0;
 220     }
 221     inline unsigned int get(unsigned int desired)
 222     {
 223         if (desired > left) {
 224             desired = left;
 225             left = 0;
 226             return desired;
 227         }
 228         left -= desired;
 229         return desired;
 230     }
 231     inline bool elapsed()
 232     {
 233         if (!left) {
 234             left = frequency;
 235             return true;
 236         }
 237         return false;
 238     }
 239 };
 240
 241 class gain_smoothing: public inertia<linear_ramp>
 242 {
 243 public:
 244     gain_smoothing()
 245     : inertia<linear_ramp>(linear_ramp(64))
 246     {
 247     }
 248     void set_sample_rate(int sr)
 249     {
 250         ramp = linear_ramp(sr / 100);
 251     }
 252     // to change param, use set_inertia(value)
 253     // to read param, use get()
 254 };
 255
 256 }
 257
 258 #endif