annotate C++/CAR.C @ 593:40934f897a56

Fixed certain minor documentation bugs.
Added the CAR::designFilters and CAR::stageG methods. These methods design the CAR.coeff coefficients. They have been compared to be the same as the matlab coefficients.
An Ear is now contructed with a specific FS or, it uses the default.
Added the PsychoAcoustics class to do ERB and Hz conversions.
Added the EarTest.C main which allows the construction of an Ear class for testing.

// Copyright 2013 Matt R. Flax <flatmax\@> All Rights Reserved.
// Author Matt Flax <flatmax@>
//
// 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.
/**
    \author {Matt Flax <flatmax\@>}
    \date 2013.02.08
*/

#include "CAR.H"

CAR::CAR() {
    //ctor
}

CAR::~CAR() {
    //dtor
}

void CAR::designFilters(FP_TYPE fs, int n_ch) {
    // don't really need these zero arrays, but it's a clue to what fields
    // and types are need in ohter language implementations:
    coeff.r1_coeffs.resize(n_ch, 1); coeff.r1_coeffs-=coeff.r1_coeffs; // resize and zero
    coeff.a0_coeffs.resize(n_ch, 1); coeff.a0_coeffs-=coeff.a0_coeffs;
    coeff.c0_coeffs.resize(n_ch, 1); coeff.c0_coeffs-=coeff.c0_coeffs;
    coeff.h_coeffs.resize(n_ch, 1); coeff.h_coeffs-=coeff.h_coeffs;
    coeff.g0_coeffs.resize(n_ch, 1); coeff.g0_coeffs-=coeff.g0_coeffs;
    // zr_coeffs is not zeroed ... perhaps it should be ?

// zero_ratio comes in via h.  In book's circuit D, zero_ratio is 1/sqrt(a),
// and that a is here 1 / (1+f) where h = f*c.
// solve for f:  1/zero_ratio^2 = 1 / (1+f)
// zero_ratio^2 = 1+f => f = zero_ratio^2 - 1
    FP_TYPE f = pow(param.zero_ratio,2.) - 1.;  // nominally 1 for half-octave

// Make pole positions, s and c coeffs, h and g coeffs, etc.,
// which mostly depend on the pole angle theta:
    Array<FP_TYPE, Dynamic, 1> theta = pole_freqs * (2. * M_PI / fs);


// undamped coupled-form coefficients:
    coeff.c0_coeffs = theta.sin();
    coeff.a0_coeffs = theta.cos();

// different possible interpretations for min-damping r:
// r = exp(-theta * CF_CAR_params.min_zeta).
// Compress theta to give somewhat higher Q at highest thetas:
    FP_TYPE ff = param.high_f_damping_compression; // 0 to 1 typ. 0.5
    Array<FP_TYPE, Dynamic,1> x = theta/M_PI;

    coeff.zr_coeffs = M_PI * (x - ff * x.pow(3.));  // when ff is 0, this is just theta,
//                       and when ff is 1 it goes to zero at theta = pi.
    coeff.r1_coeffs = (1. - coeff.zr_coeffs.array() * param.max_zeta);  // "r1" for the max-damping condition

// Increase the min damping where channels are spaced out more, by pulling
// 25% of the way toward ERB_Hz/pole_freqs (close to 0.1 at high f)
    Array<FP_TYPE, Dynamic, 1> min_zetas = param.min_zeta + 0.25*(PsychoAcoustics::Hz2ERB(pole_freqs, param.ERB_break_freq, param.ERB_Q).array() / pole_freqs - param.min_zeta);
    coeff.zr_coeffs = coeff.zr_coeffs.array() * (param.max_zeta - min_zetas); // how r relates to undamping

// the zeros follow via the h_coeffs
    coeff.h_coeffs = coeff.c0_coeffs * f;

// for unity gain at min damping, radius r; only used in CARFAC_Init:
    Array<FP_TYPE, Dynamic,1> relative_undamping(n_ch, 1);
    relative_undamping=(relative_undamping-=relative_undamping).cos();// what is an efficient way to set a matrix to 1. ? As this is in a design phase, I will leave it for now

// this function needs to take CAR_coeffs even if we haven't finished
// constucting it by putting in the g0_coeffs:
    coeff.g0_coeffs = stageG(relative_undamping);

}

Array<FP_TYPE, Dynamic, 1> CAR::stageG(Array<FP_TYPE, Dynamic, 1> &relative_undamping) {
    // at max damping
    Array<FP_TYPE, Dynamic, 1> r  = coeff.r1_coeffs.array() + coeff.zr_coeffs.array() * relative_undamping;
    return (1. - 2.*r*coeff.a0_coeffs.array() + r.pow(2.)) / (1. - 2.*r*coeff.a0_coeffs.array() + coeff.h_coeffs.array()*r*coeff.c0_coeffs.array() + pow(r,2.));
}