2 Copyright (C) 2008 Torben Hohn
4 This program is free software; you can redistribute it and/or modify
5 it under the terms of the GNU General Public License as published by
6 the Free Software Foundation; either version 2 of the License, or
7 (at your option) any later version.
9 This program is distributed in the hope that it will be useful,
10 but WITHOUT ANY WARRANTY; without even the implied warranty of
11 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
12 GNU General Public License for more details.
14 You should have received a copy of the GNU General Public License
15 along with this program; if not, write to the Free Software
16 Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
23 #include "ardour/pi_controller.h"
25 static inline double hann(double x) {
26 return 0.5 * (1.0 - cos(2 * M_PI * x));
29 PIController::PIController (double resample_factor, int fir_size)
31 resample_mean = resample_factor;
32 static_resample_factor = resample_factor;
33 offset_array = new double[fir_size];
34 window_array = new double[fir_size];
35 offset_differential_index = 0;
36 offset_integral = 0.0;
37 smooth_size = fir_size;
39 for (int i = 0; i < fir_size; i++) {
40 offset_array[i] = 0.0;
41 window_array[i] = hann(double(i) / (double(fir_size) - 1.0));
44 // These values could be configurable
45 catch_factor = 100000;
46 catch_factor2 = 10000;
48 controlquant = 10000.0;
51 PIController::~PIController ()
53 delete [] offset_array;
54 delete [] window_array;
58 PIController::get_ratio (int fill_level)
60 double offset = fill_level;
63 offset_array[(offset_differential_index++) % smooth_size] = offset;
65 // Build the mean of the windowed offset array basically fir lowpassing.
67 for (int i = 0; i < smooth_size; i++) {
68 smooth_offset += offset_array[(i + offset_differential_index - 1) % smooth_size] * window_array[i];
70 smooth_offset /= double(smooth_size);
72 // This is the integral of the smoothed_offset
73 offset_integral += smooth_offset;
76 // Clamp offset : the smooth offset still contains unwanted noise which would go straigth onto the resample coeff.
77 // It only used in the P component and the I component is used for the fine tuning anyways.
78 if (fabs(smooth_offset) < pclamp)
81 // Ok, now this is the PI controller.
82 // u(t) = K * (e(t) + 1/T \int e(t') dt')
83 // Kp = 1/catch_factor and T = catch_factor2 Ki = Kp/T
84 current_resample_factor
85 = static_resample_factor - smooth_offset / catch_factor - offset_integral / catch_factor / catch_factor2;
87 // Now quantize this value around resample_mean, so that the noise which is in the integral component doesnt hurt.
88 current_resample_factor = floor((current_resample_factor - resample_mean) * controlquant + 0.5) / controlquant + resample_mean;
90 // Calculate resample_mean so we can init ourselves to saner values.
91 // resample_mean = 0.9999 * resample_mean + 0.0001 * current_resample_factor;
92 resample_mean = 0.9 * resample_mean + 0.1 * current_resample_factor;
93 return current_resample_factor;
97 PIController::out_of_bounds()
100 // Set the resample_rate... we need to adjust the offset integral, to do this.
101 // first look at the PI controller, this code is just a special case, which should never execute once
102 // everything is swung in.
103 offset_integral = - (resample_mean - static_resample_factor) * catch_factor * catch_factor2;
104 // Also clear the array. we are beginning a new control cycle.
105 for (i = 0; i < smooth_size; i++) {
106 offset_array[i] = 0.0;