# HG changeset patch
# User tomwalters
# Date 1266345655 0
# Node ID a57b29e373c72ddf7161d128309164d48c00d4ec
# Parent  ce2bab04f155841b18c7366b307169a821c2fd6c
- Added stub for a Slaney IIR Gammatone filterbank

diff -r ce2bab04f155 -r a57b29e373c7 trunk/src/Modules/BMM/ModuleGammatone.cc
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/trunk/src/Modules/BMM/ModuleGammatone.cc	Tue Feb 16 18:40:55 2010 +0000
@@ -0,0 +1,112 @@
+// Copyright 2009-2010, Thomas Walters
+//
+// AIM-C: A C++ implementation of the Auditory Image Model
+// http://www.acousticscale.org/AIMC
+//
+// 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 3 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, see <http://www.gnu.org/licenses/>.
+
+/*! \file
+ *  \brief Slaney's gammatone filterbank
+ *
+ *  \author Thomas Walters <tom@acousticscale.org>
+ *  \date created 2009/11/13
+ *  \version \$Id$
+ */
+
+#include <complex>
+
+#include "Modules/BMM/ModuleGammatone.h"
+
+namespace aimc {
+using std::complex;
+ModuleGammatone::ModuleGammatone(Parameters *params) : Module(params) {
+  module_identifier_ = "gtfb";
+  module_type_ = "bmm";
+  module_description_ = "Gammatone filterbank (Slaney's IIR gammatone)";
+  module_version_ = "$Id$";
+
+  num_channels_ = parameters_->DefaultInt("gtfb.channel_count", 200);
+  min_frequency_ = parameters_->DefaultFloat("gtfb.min_frequency", 86.0f);
+  max_frequency_ = parameters_->DefaultFloat("gtfb.max_frequency", 16000.0f);
+}
+
+bool ModuleGammatone::InitializeInternal(const SignalBank& input) {
+  // Calculate number of channels, and centre frequencies
+
+  forward_.resize(num_channels_);
+  feedback_.resize(num_channels_);
+
+  for (int ch = 0; ch < num_channels_; ++ch) {
+    float erb = Freq2ERBw(cf)
+
+    // Sample interval
+    float dt = 1.0f / fs;
+
+    // Bandwidth parameter
+    float b = 1.019f * 2.0f * M_PI * erb;
+
+    // All of the following expressions are derived in Apple TR #35, "An 
+    // Efficient Implementation of the Patterson-Holdsworth Cochlear 
+    // Filter Bank".
+
+    // Calculate the gain:
+    complex<float> exponent(0.0f, 2.0f * cf * M_PI * T);
+    complex<float> ec = exp(2.0f * complex_exponent);
+    complex<float> two_cf_pi_t(2.0f * cf * M_PI * T, 0.0f);
+    complex<float> two_pow(pow(2.0f, (3.0f/2.0f)), 0.0f);
+
+    complex<float> p = -2.0f * ec * T + 2.0f * exp(-(B * T) + exponent) * dt;
+
+    float gain = abs(
+      (part1 * (cos(two_cf_pi_t) - sqrt(3.0f - twopow) * sin(two_cf_pi_t)))
+      * (part1 * (cos(two_cf_pi_t) + sqrt(3.0f - twopow) * sin(two_cf_pi_t)))
+      * (part1 * (cos(two_cf_pi_t) - sqrt(3.0f + twopow) * sin(two_cf_pi_t)))
+      * (part1 * (cos(two_cf_pi_t) + sqrt(3.0f + twopow) * sin(two_cf_pi_t)))
+      / pow(-2.0f / exp(2.0f * b * dt) - 2.0f * ec + 2.0f * (1.0f + ec)
+            / exp(b * dt), 4.0f));
+
+    // The filter coefficients themselves:
+    forward[ch].resize(5, 0.0f);
+    feedback[ch].resize(9, 0.0f);
+
+    forward[ch][0] = pow(T, 4.0f) / gain;
+    forward[ch][1] = (-4.0f * pow(T, 4.0f) * cos(2.0f * cf * M_PI * dt)
+                      / exp(b * dt) / gain);
+    forward[ch][2] = (6.0f * pow(T, 4.0f) * cos(4.0f * cf * M_PI * dt)
+                      / exp(2.0f * b * dt) / gain);
+    forward[ch][3] = (-4.0f * pow(T, 4.0f) * cos(6.0f * cf * M_PI * dt)
+                      / exp(3.0f * b * dt) / gain);
+    forward[ch][4] = (pow(T,4.0f) * cos(8.0f * cf * M_PI * dt)
+                      / exp(4.0f * b * dt) / gain);
+
+    feedback[ch][0] = 1.0f;
+    feedback[ch][1] = -8.0f * cos(2.0f * cf * M_PI * T) / exp(b * dt);
+    feedback[ch][2] = (4.0f * (4.0f + 3.0f * cos(4.0f * cf * M_PI * dt))
+                       / exp(2.0f * b * dt));
+    feedback[ch][3] = (-8.0f * (6.0f * cos(2.0f * cf * M_PI * dt)
+                                + cos(6.0f * cf * M_PI * dt))
+                       / exp(3.0f * b * dt));
+    feedback[ch][4] = (2.0f * (18.0f + 16.0f * cos(4.0f * cf * M_PI * dt)
+                               + cos(8.0f * cf * M_PI * dt))
+                       / exp(4.0f * b * dt));
+    feedback[ch][5] = (-8.0f * (6.0f * cos(2.0f * cf * M_PI * T)
+                                + cos(6.0f * cf * M_PI * T))
+                       / exp(5.0f * B * T));
+    feedback[ch][6] = (4.0f * (4.0f + 3.0f * cos(4.0f * cf * M_PI * T))
+                       / exp(6.0f * B * T));
+    feedback[ch][7] = -8.0f * cos(2.0f * cf * M_PI * dt) / exp(7.0f * b * dt);
+    feedback[ch][8] = exp(-8.0f * b * dt);
+  }
+}
+} // namespace aimc
\ No newline at end of file
diff -r ce2bab04f155 -r a57b29e373c7 trunk/src/Modules/BMM/ModuleGammatone.h
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/trunk/src/Modules/BMM/ModuleGammatone.h	Tue Feb 16 18:40:55 2010 +0000
@@ -0,0 +1,48 @@
+// Copyright 2009-2010, Thomas Walters
+//
+// AIM-C: A C++ implementation of the Auditory Image Model
+// http://www.acousticscale.org/AIMC
+//
+// 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 3 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, see <http://www.gnu.org/licenses/>.
+
+/*! \file
+ *  \brief Slaney's gammatone filterbank
+ *
+ *  \author Thomas Walters <tom@acousticscale.org>
+ *  \date created 2009/11/13
+ *  \version \$Id$
+ */
+
+#include <vector>
+
+namespace aimc {
+using std::vector;
+class ModuleGammatone : public Module {
+ public:
+  ModuleGammatone(Parameters *params);
+  virtual ~ModuleGammatone();
+  //! \brief Process a buffer
+  virtual void Process(const SignalBank &input);
+
+ private:
+  virtual bool InitializeInternal(const SignalBank& input);
+  virtual void ResetInternal();
+  vector<vector<float> > forward_;
+  vector<vector<float> > feedback_;
+  vector<float> centre_frequencies_;
+  int num_channels_;
+  float max_frequency_;
+  float min_frequency_;
+};
+}  // namespace aimc
\ No newline at end of file