possibly useful PI controller from torben by way of jack2

git-svn-id: svn://localhost/ardour2/branches/3.0@6264 d708f5d6-7413-0410-9779-e7cbd77b26cf

diff --git a/libs/ardour/ardour/pi_controller.h b/libs/ardour/ardour/pi_controller.h
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+/*
+  Copyright (C) 2008 Torben Hohn
+  
+  This program 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 2 of the License, or
+  (at your option) any later version.
+  
+  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 for more details.
+
+  You should have received a copy of the GNU General Public License
+  along with this program; if not, write to the Free Software
+  Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
+*/
+
+#ifndef __libardour_pi_controller__
+#define __libardour_pi_controller__
+
+class PIController {
+
+  public:
+    PIController (double resample_factor, int fir_size);
+    ~PIController();
+        
+    void reset (double resample_factor) {
+            resample_mean = resample_factor;
+            static_resample_factor = resample_factor;
+           out_of_bounds ();
+    }
+        
+    double get_ratio (int fill_level);
+    void out_of_bounds();
+
+  public:
+    double  resample_mean;
+    double  static_resample_factor;
+    double* offset_array;
+    double* window_array;
+    int     offset_differential_index;
+    double  offset_integral;
+    double  catch_factor;
+    double  catch_factor2;
+    double  pclamp;
+    double  controlquant;
+    int     smooth_size;
+    double  smooth_offset;
+    double  current_resample_factor;
+};
+
+#endif /* __libardour_pi_controller__ */

diff --git a/libs/ardour/pi_controller.cc b/libs/ardour/pi_controller.cc
new file mode 100644 (file)
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+++ b/libs/ardour/pi_controller.cc
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+/*
+  Copyright (C) 2008 Torben Hohn
+  
+  This program 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 2 of the License, or
+  (at your option) any later version.
+  
+  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 for more details.
+
+  You should have received a copy of the GNU General Public License
+  along with this program; if not, write to the Free Software
+  Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
+*/
+
+#include <iostream>
+#include <cmath>
+#include <cstdlib>
+
+#include "ardour/pi_controller.h"
+
+static inline double hann(double x) {
+       return 0.5 * (1.0 - cos(2 * M_PI * x));
+}
+    
+PIController::PIController (double resample_factor, int fir_size) 
+{
+       resample_mean = resample_factor;
+       static_resample_factor = resample_factor;
+       offset_array = new double[fir_size];
+       window_array = new double[fir_size];
+       offset_differential_index = 0;
+       offset_integral = 0.0;
+       smooth_size = fir_size;
+        
+       for (int i = 0; i < fir_size; i++) {
+                offset_array[i] = 0.0;
+                window_array[i] = hann(double(i) / (double(fir_size) - 1.0));
+       }
+       
+       // These values could be configurable
+       catch_factor = 100000;
+       catch_factor2 = 10000;
+       pclamp = 15.0;
+       controlquant = 10000.0;
+}
+
+PIController::~PIController ()
+{
+       delete [] offset_array;
+       delete [] window_array;
+}
+
+double
+PIController::get_ratio (int fill_level)
+{
+       double offset = fill_level;
+       
+       // Save offset.
+       offset_array[(offset_differential_index++) % smooth_size] = offset;
+        
+       // Build the mean of the windowed offset array basically fir lowpassing.
+       smooth_offset = 0.0;
+       for (int i = 0; i < smooth_size; i++) {
+                smooth_offset += offset_array[(i + offset_differential_index - 1) % smooth_size] * window_array[i];
+       }
+       smooth_offset /= double(smooth_size);
+        
+       // This is the integral of the smoothed_offset
+       offset_integral += smooth_offset;
+
+       
+       // Clamp offset : the smooth offset still contains unwanted noise which would go straigth onto the resample coeff.
+       // It only used in the P component and the I component is used for the fine tuning anyways.
+       if (fabs(smooth_offset) < pclamp)
+                smooth_offset = 0.0;
+       
+       // Ok, now this is the PI controller. 
+       // u(t) = K * (e(t) + 1/T \int e(t') dt')
+       // Kp = 1/catch_factor and T = catch_factor2  Ki = Kp/T 
+       current_resample_factor 
+                = static_resample_factor - smooth_offset / catch_factor - offset_integral / catch_factor / catch_factor2;
+       
+       // Now quantize this value around resample_mean, so that the noise which is in the integral component doesnt hurt.
+       current_resample_factor = floor((current_resample_factor - resample_mean) * controlquant + 0.5) / controlquant + resample_mean;
+       
+       // Calculate resample_mean so we can init ourselves to saner values.
+       // resample_mean = 0.9999 * resample_mean + 0.0001 * current_resample_factor;
+       resample_mean = 0.9 * resample_mean + 0.1 * current_resample_factor;
+       return current_resample_factor;
+}
+        
+void 
+PIController::out_of_bounds()
+{
+       int i;
+       // Set the resample_rate... we need to adjust the offset integral, to do this.
+       // first look at the PI controller, this code is just a special case, which should never execute once
+       // everything is swung in. 
+       offset_integral = - (resample_mean - static_resample_factor) * catch_factor * catch_factor2;
+       // Also clear the array. we are beginning a new control cycle.
+       for (i = 0; i < smooth_size; i++) {
+                offset_array[i] = 0.0;
+       }
+}