diff carfac/ear.cc @ 609:aefe2ca0674f

First version of a C++ implementation by Alex Brandmeyer

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/carfac/ear.cc	Mon May 13 22:51:15 2013 +0000
@@ -0,0 +1,268 @@
+//
+//  ear.cc
+//  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.
+
+#include "ear.h"
+
+void Ear::InitEar(long fs, CARParams car_p, IHCParams ihc_p, AGCParams agc_p){
+  car_params_ = car_p;
+  ihc_params_ = ihc_p;
+  agc_params_ = agc_p;
+  n_ch_ = 0;
+  FPType pole_hz = car_params_.first_pole_theta_ * fs / (2 * PI);
+  while (pole_hz > car_params_.min_pole_hz_) {
+    n_ch_++;
+    pole_hz = pole_hz - car_params_.erb_per_step_ *
+    ERBHz(pole_hz, car_params_.erb_break_freq_, car_params_.erb_q_);
+  }
+  FloatArray pole_freqs(n_ch_);
+  pole_hz = car_params_.first_pole_theta_ * fs / (2 * PI);
+  for(int ch=0;ch < n_ch_; ch++){
+    pole_freqs(ch) = pole_hz;
+    pole_hz = pole_hz - car_params_.erb_per_step_ *
+    ERBHz(pole_hz, car_params_.erb_break_freq_, car_params_.erb_q_);
+  }
+  max_channels_per_octave_ = log(2) / log(pole_freqs(0) / pole_freqs(1));
+  car_coeffs_.DesignFilters(car_params_, fs, &pole_freqs);
+  agc_coeffs_.DesignAGC(agc_params_, fs, n_ch_);
+  ihc_coeffs_.DesignIHC(ihc_params_, fs, n_ch_);
+  car_state_.InitCARState(car_coeffs_);
+  agc_state_.InitAGCState(agc_coeffs_);
+  ihc_state_.InitIHCState(ihc_coeffs_);
+
+}
+
+FloatArray Ear::CARStep(FPType input){
+  FloatArray g(n_ch_);
+  FloatArray zb(n_ch_);
+  FloatArray za(n_ch_);
+  FloatArray v(n_ch_);
+  FloatArray nlf(n_ch_);
+  FloatArray r(n_ch_);
+  FloatArray z1(n_ch_);
+  FloatArray z2(n_ch_);
+  FloatArray zy(n_ch_);
+  FPType in_out;
+  
+  // do the DOHC stuff:
+  g = car_state_.g_memory_ + car_state_.dg_memory_; //interp g
+  zb = car_state_.zb_memory_ + car_state_.dzb_memory_; //AGC interpolation state
+  // update the nonlinear function of "velocity", and zA (delay of z2):
+  za = car_state_.za_memory_;
+  v = car_state_.z2_memory_ - za;
+  nlf = OHC_NLF(v);
+  r = car_coeffs_.r1_coeffs_ + (zb * nlf); // zB * nfl is "undamping" delta r
+  za = car_state_.z2_memory_;
+  // now reduce state by r and rotate with the fixed cos/sin coeffs:
+  z1 = r * ((car_coeffs_.a0_coeffs_ * car_state_.z1_memory_) -
+            (car_coeffs_.c0_coeffs_ * car_state_.z2_memory_));
+  z2 = r * ((car_coeffs_.c0_coeffs_ * car_state_.z1_memory_) +
+            (car_coeffs_.a0_coeffs_ * car_state_.z2_memory_));
+  zy = car_coeffs_.h_coeffs_ * z2;
+  // Ripple input-output path, instead of parallel, to avoid delay...
+  // this is the only part that doesn't get computed "in parallel":
+  in_out = input;
+  for (int ch = 0; ch < n_ch_; ch++){
+    z1(ch) = z1(ch) + in_out;
+    // ripple, saving final channel outputs in zY
+    in_out = g(ch) * (in_out + zy(ch));
+    zy(ch) = in_out;
+  }
+  car_state_.z1_memory_ = z1;
+  car_state_.z2_memory_ = z2;
+  car_state_.za_memory_ = za;
+  car_state_.zb_memory_ = zb;
+  car_state_.zy_memory_ = zy;
+  car_state_.g_memory_ = g;
+  // car_out is equal to zy state;
+  return zy;
+}
+
+// start with a quadratic nonlinear function, and limit it via a
+// rational function; make the result go to zero at high
+// absolute velocities, so it will do nothing there.
+FloatArray Ear::OHC_NLF(FloatArray velocities){
+  FloatArray nlf(n_ch_);
+  nlf = 1 / ((velocities * car_coeffs_.velocity_scale_) +
+             (car_coeffs_.v_offset_ * car_coeffs_.v_offset_));
+  return nlf;
+}
+
+// One sample-time update of inner-hair-cell (IHC) model, including the
+// detection nonlinearity and one or two capacitor state variables.
+FloatArray Ear::IHCStep(FloatArray car_out){
+  FloatArray ihc_out(n_ch_);
+  FloatArray ac_diff(n_ch_);
+  FloatArray conductance(n_ch_);
+  ac_diff = car_out - ihc_state_.ac_coupler_;
+  ihc_state_.ac_coupler_ = ihc_state_.ac_coupler_ +
+                           (ihc_coeffs_.ac_coeff_ * ac_diff);
+  if (ihc_coeffs_.just_hwr_) {
+    //TODO Figure out best implementation with Eigen max/min methods
+    for (int ch = 0; ch < n_ch_; ch++){
+      FPType a;
+      if (ac_diff(ch) > 0){
+        a = ac_diff(ch);
+      } else {
+        a = 0;
+      }
+      if (a < 2){
+        ihc_out(ch) = a;
+      } else {
+        ihc_out(ch) = 2;
+      }
+    }
+    
+  } else {
+    conductance = CARFACDetect(ac_diff);
+    if (ihc_coeffs_.one_cap_) {
+      ihc_out = conductance * ihc_state_.cap1_voltage_;
+      ihc_state_.cap1_voltage_ = ihc_state_.cap1_voltage_ -
+                                 (ihc_out * ihc_coeffs_.out1_rate_) +
+                                 ((1 - ihc_state_.cap1_voltage_)
+                                  * ihc_coeffs_.in1_rate_);
+    } else {
+      ihc_out = conductance * ihc_state_.cap2_voltage_;
+      ihc_state_.cap1_voltage_ = ihc_state_.cap1_voltage_ -
+                      ((ihc_state_.cap1_voltage_ - ihc_state_.cap2_voltage_)
+                      * ihc_coeffs_.out1_rate_) +
+                      ((1 - ihc_state_.cap1_voltage_) * ihc_coeffs_.in1_rate_);
+      ihc_state_.cap2_voltage_ = ihc_state_.cap2_voltage_ -
+                          (ihc_out * ihc_coeffs_.out2_rate_) +
+                          ((ihc_state_.cap1_voltage_ - ihc_state_.cap2_voltage_)
+                          * ihc_coeffs_.in2_rate_);
+    }
+    // smooth it twice with LPF:
+    ihc_out = ihc_out * ihc_coeffs_.output_gain_;
+    ihc_state_.lpf1_state_ = ihc_state_.lpf1_state_ +
+                  (ihc_coeffs_.lpf_coeff_ * (ihc_out - ihc_state_.lpf1_state_));
+    ihc_state_.lpf2_state_ = ihc_state_.lpf2_state_ +
+                  (ihc_coeffs_.lpf_coeff_ *
+                   (ihc_state_.lpf1_state_ - ihc_state_.lpf2_state_));
+    ihc_out = ihc_state_.lpf2_state_ - ihc_coeffs_.rest_output_;
+  }
+  ihc_state_.ihc_accum_ += ihc_out;
+  return ihc_out;
+}
+
+bool Ear::AGCStep(FloatArray ihc_out){
+  int stage = 0;
+  FloatArray agc_in(n_ch_);
+  agc_in = agc_coeffs_.detect_scale_ * ihc_out;
+  bool updated = AGCRecurse(stage, agc_in);
+  return updated;
+}
+
+bool Ear::AGCRecurse(int stage, FloatArray agc_in){
+  bool updated = true;
+  // decim factor for this stage, relative to input or prev. stage:
+  int decim = agc_coeffs_.decimation_(stage);
+  // decim phase of this stage (do work on phase 0 only):
+  //TODO FIX MODULO
+  
+  int decim_phase = agc_state_.decim_phase_(stage);
+  decim_phase = decim_phase % decim;
+  agc_state_.decim_phase_(stage) = decim_phase;
+  // accumulate input for this stage from detect or previous stage:
+  agc_state_.input_accum_.block(0,stage,n_ch_,1) =
+                        agc_state_.input_accum_.block(0,stage,n_ch_,1) + agc_in;
+  
+  // nothing else to do if it's not the right decim_phase
+  if (decim_phase == 0){
+    // do lots of work, at decimated rate.
+    // decimated inputs for this stage, and to be decimated more for next:
+    agc_in = agc_state_.input_accum_.block(0,stage,n_ch_,1) / decim;
+    // reset accumulator:
+    agc_state_.input_accum_.block(0,stage,n_ch_,1) = FloatArray::Zero(n_ch_);
+    
+    if (stage < (agc_coeffs_.decimation_.size() - 1)){
+      // recurse to evaluate next stage(s)
+      updated = AGCRecurse(stage+1, agc_in);
+      // and add its output to this stage input, whether it updated or not:
+      agc_in = agc_in + (agc_coeffs_.agc_stage_gain_ *
+                         agc_state_.agc_memory_.block(0,stage+1,n_ch_,1));
+    }
+    FloatArray agc_stage_state = agc_state_.agc_memory_.block(0,stage,n_ch_,1);
+    // first-order recursive smoothing filter update, in time:
+    agc_stage_state = agc_stage_state + (agc_coeffs_.agc_epsilon_(stage) *
+                                         (agc_in - agc_stage_state));
+    agc_stage_state = AGCSpatialSmooth(stage, agc_stage_state);
+    agc_state_.agc_memory_.block(0,stage,n_ch_,1) = agc_stage_state;
+  } else {
+    updated = false;
+  }
+  return updated;
+}
+
+FloatArray Ear::AGCSpatialSmooth(int stage, FloatArray stage_state){
+  int n_iterations = agc_coeffs_.agc_spatial_iterations_(stage);
+  bool use_fir;
+  if (n_iterations < 4){
+    use_fir = true;
+  } else {
+    use_fir = false;
+  }
+  
+  if (use_fir) {
+    FloatArray fir_coeffs = agc_coeffs_.agc_spatial_fir_.block(0,stage,3,1);
+    FloatArray ss_tap1(n_ch_);
+    FloatArray ss_tap2(n_ch_);
+    FloatArray ss_tap3(n_ch_);
+    FloatArray ss_tap4(n_ch_);
+    int n_taps = agc_coeffs_.agc_spatial_n_taps_(stage);
+    //Initialize first two taps of stage state, used for both cases
+    ss_tap1(0) = stage_state(0);
+    ss_tap1.block(1,0,n_ch_-1,1) = stage_state.block(0,0,n_ch_-1,1);
+    ss_tap2(n_ch_-1) = stage_state(n_ch_-1);
+    ss_tap2.block(0,0,n_ch_-1,1) = stage_state.block(1,0,n_ch_-1,1);
+    switch (n_taps) {
+      case 3:
+        stage_state = (fir_coeffs(0) * ss_tap1) +
+                      (fir_coeffs(1) * stage_state) +
+                      (fir_coeffs(2) * ss_tap2);
+        break;
+      case 5:
+        //Initialize last two taps of stage state, used for 5-tap case
+        ss_tap3(0) = stage_state(0);
+        ss_tap3(1) = stage_state(1);
+        ss_tap3.block(2,0,n_ch_-2,1) = stage_state.block(0,0,n_ch_-2,1);
+        ss_tap4(n_ch_-2) = stage_state(n_ch_-1);
+        ss_tap4(n_ch_-1) = stage_state(n_ch_-2);
+        ss_tap4.block(0,0,n_ch_-2,1) = stage_state.block(2,0,n_ch_-2,1);
+        
+        stage_state = (fir_coeffs(0) * (ss_tap3 + ss_tap1)) +
+                      (fir_coeffs(1) * stage_state) +
+                      (fir_coeffs(2) * (ss_tap2 + ss_tap4));
+        break;
+      default:
+        //TODO Throw Error
+        std::cout << "Error: bad n-taps in AGCSpatialSmooth" << std::endl;
+    }
+    
+  } else {
+    stage_state = AGCSmoothDoubleExponential(stage_state);
+  }
+  return stage_state;
+}
+
+FloatArray Ear::AGCSmoothDoubleExponential(FloatArray stage_state){
+  return stage_state;
+}