tomwalters@276: // Copyright 2009-2010, Thomas Walters
tomwalters@276: //
tomwalters@276: // AIM-C: A C++ implementation of the Auditory Image Model
tomwalters@276: // http://www.acousticscale.org/AIMC
tomwalters@276: //
tomwalters@276: // This program is free software: you can redistribute it and/or modify
tomwalters@276: // it under the terms of the GNU General Public License as published by
tomwalters@276: // the Free Software Foundation, either version 3 of the License, or
tomwalters@276: // (at your option) any later version.
tomwalters@276: //
tomwalters@276: // This program is distributed in the hope that it will be useful,
tomwalters@276: // but WITHOUT ANY WARRANTY; without even the implied warranty of
tomwalters@276: // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
tomwalters@276: // GNU General Public License for more details.
tomwalters@276: //
tomwalters@276: // You should have received a copy of the GNU General Public License
tomwalters@276: // along with this program.  If not, see <http://www.gnu.org/licenses/>.
tomwalters@276: 
tomwalters@276: /*! \file
tomwalters@276:  *  \brief Slaney's gammatone filterbank
tomwalters@276:  *
tomwalters@276:  *  \author Thomas Walters <tom@acousticscale.org>
tomwalters@276:  *  \date created 2009/11/13
tomwalters@276:  *  \version \$Id$
tomwalters@288:  *
tomwalters@288:  * This is the version of the IIR gammatone used in Slaney's Auditory toolbox.
tomwalters@288:  * The original verison as described in Apple Tech. Report #35 has a problem
tomwalters@288:  * with the high-order coefficients at low centre frequencies and high sample
tomwalters@288:  * rates. Since it is important that AIM-C can deal with these cases (for
tomwalters@288:  * example for the Gaussian features), I've reiplemeted Slaney's alternative
tomwalters@288:  * version which uses a cascade of four second-order filters in place of the 
tomwalters@288:  * eighth-order filter.
tomwalters@276:  */
tomwalters@280: #ifndef _AIMC_MODULES_BMM_GAMMATONE_H_
tomwalters@280: #define _AIMC_MODULES_BMM_GAMMATONE_H_
tomwalters@276: 
tomwalters@276: #include <vector>
tomwalters@276: 
tomwalters@277: #include "Support/Module.h"
tomwalters@277: #include "Support/Parameters.h"
tomwalters@277: #include "Support/SignalBank.h"
tomwalters@277: 
tomwalters@276: namespace aimc {
tomwalters@276: using std::vector;
tomwalters@276: class ModuleGammatone : public Module {
tomwalters@276:  public:
tomwalters@280:   explicit ModuleGammatone(Parameters *params);
tomwalters@276:   virtual ~ModuleGammatone();
tomwalters@280:   /*! \brief Process a buffer
tomwalters@280:    */
tomwalters@276:   virtual void Process(const SignalBank &input);
tomwalters@276: 
tomwalters@276:  private:
tomwalters@276:   virtual bool InitializeInternal(const SignalBank& input);
tomwalters@276:   virtual void ResetInternal();
tomwalters@288: 
tomwalters@288:   // Filter coefficients
tomwalters@288:   vector<vector<double> > b1_;
tomwalters@288:   vector<vector<double> > b2_;
tomwalters@288:   vector<vector<double> > b3_;
tomwalters@288:   vector<vector<double> > b4_;
tomwalters@288:   vector<vector<double> > a_;
tomwalters@288: 
tomwalters@288:   vector<vector<double> > state_1_;
tomwalters@288:   vector<vector<double> > state_2_;
tomwalters@288:   vector<vector<double> > state_3_;
tomwalters@288:   vector<vector<double> > state_4_;
tomwalters@288: 
tomwalters@288:   vector<double> centre_frequencies_;
tomwalters@276:   int num_channels_;
tomwalters@288:   double max_frequency_;
tomwalters@288:   double min_frequency_;
tomwalters@276: };
tomwalters@280: }  // namespace aimc
tomwalters@280: #endif  // _AIMC_MODULES_BMM_GAMMATONE_H_