view carfac/carfac_common.h @ 642:20f64146c2ce

Initial translation of SAI code to C++.

This only implements the simple (as opposed to the layered) SAI, as
implemented in SAI_Run.m.

//
//  carfac_common.h
//  CARFAC Open Source C++ Library
//
//  Created by Alex Brandmeyer on 5/10/13.
//
// This C++ file is part of an implementation of Lyon's cochlear model:
// "Cascade of Asymmetric Resonators with Fast-Acting Compression"
// to supplement Lyon's upcoming book "Human and Machine Hearing"
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
//
// *****************************************************************************
// carfac_common.h
// *****************************************************************************
// This file contains the base level definitions and includes used within the
// CARFAC C++ library. It also defines some low level functions which are used
// during the calculation of the various coefficient sets required by the model.
//
// The current implementation of the library is dependent on the use of the
// Eigen C++ library for linear algebra. Specifically, Eigen Arrays are used
// extensively for coefficient wise operations during both the design and run
// stages of the model.
//
// The 'FPType' typedef is specified in this file in order to enable quick
// switching between precision levels (i.e. float vs. double) throughout the
// library. The remainder of the code uses this type for specifying floating
// point scalars.
//
// An additional typedefs are defined for one dimensional arrays: FloatArray.
// These in turn make use of FPType so that the precision level across floating
// point data is consistent.
//
// The functions 'ERBHz' and 'CARFACDetect' are defined here, and are used
// during the design stage of a CARFAC model.

#ifndef CARFAC_CARFAC_COMMON_H
#define CARFAC_CARFAC_COMMON_H

// The Eigen library is used extensively for floating point arrays.
// For more information, see: http://eigen.tuxfamily.org
#include <Eigen/Dense>

using namespace Eigen;

// The 'FPType' typedef is used to enable easy switching in precision level.
// It's currently set to double for during the unit testing phase of the
// project.
typedef double FPType;
// A typedef is used to define a one-dimensional Eigen array with the same
// precision level as FPType.
typedef Eigen::Array<FPType, Dynamic, 1> FloatArray;
typedef Eigen::Array<FPType, Dynamic, Dynamic> Float2dArray;

// A fixed value of PI is defined throughout the project.
static const FPType kPi = 3.141592653589793238;

// Two helper functions are defined here for use by the different model stages
// in calculating coeffecients and during model runtime.
// Function: ERBHz
// Auditory filter nominal Equivalent Rectangular Bandwidth
// Ref: Glasberg and Moore: Hearing Research, 47 (1990), 103-138
FPType ERBHz(const FPType cf_hz, const FPType erb_break_freq,
             const FPType erb_q);

// Function CARFACDetect
// This returns the IHC detection nonilnearity function of the filter output
// values.  This is here because it is called both in design and run phases.
FloatArray CARFACDetect(const FloatArray& x);

#endif  // CARFAC_CARFAC_COMMON_H