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@318: // Licensed under the Apache License, Version 2.0 (the "License");
tomwalters@318: // you may not use this file except in compliance with the License.
tomwalters@318: // You may obtain a copy of the License at
tomwalters@276: //
tomwalters@318: //     http://www.apache.org/licenses/LICENSE-2.0
tomwalters@276: //
tomwalters@318: // Unless required by applicable law or agreed to in writing, software
tomwalters@318: // distributed under the License is distributed on an "AS IS" BASIS,
tomwalters@318: // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
tomwalters@318: // See the License for the specific language governing permissions and
tomwalters@318: // limitations under the License.
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_