view trunk/carfac/agc.h @ 695:2e3672df5698

Simple integration test between CARFAC and SAI.

The interface between the two classes is pretty clunky because of the
way CARFACOutput stores things.  We should work on this, probably by
rotating the outer two dimensions of CARFACOutput (i.e. store outputs
in containers with sizes n_ears x n_samples x n_channels instead of
n_samples x n_ears x n_channels).

//
//  agc.h
//  CARFAC Open Source C++ Library
//
//  Created by Alex Brandmeyer on 5/30/13.
//
// 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.

#ifndef CARFAC_AGC_H
#define CARFAC_AGC_H

#include <vector>

#include "common.h"

// Automatic gain control (AGC) parameters, which are used to design the AGC
// filters.
struct AGCParams {
  AGCParams() {
    num_stages = 4;
    agc_stage_gain = 2.0;
    time_constants.resize(num_stages);
    agc1_scales.resize(num_stages);
    agc2_scales.resize(num_stages);
    agc1_scales[0] = 1.0;
    agc2_scales[0] = 1.65;
    time_constants[0] = 0.002;
    for (int i = 1; i < num_stages; ++i) {
      agc1_scales[i] = agc1_scales[i - 1] * sqrt(2.0);
      agc2_scales[i] = agc2_scales[i - 1] * sqrt(2.0);
      time_constants[i] = time_constants[i - 1] * 4.0;
    }
    decimation = {8, 2, 2, 2};
    agc_mix_coeff = 0.5;
  }
  int num_stages;
  FPType agc_stage_gain;
  FPType agc_mix_coeff;
  std::vector<FPType> time_constants;
  std::vector<int> decimation;
  std::vector<FPType> agc1_scales;
  std::vector<FPType> agc2_scales;
};

// Automatic gain control filter coefficients, which are derived from a set of
// AGCParams.
struct AGCCoeffs {
  int num_agc_stages;
  FPType agc_stage_gain;
  FPType agc_epsilon;
  int decimation;
  FPType agc_pole_z1;
  FPType agc_pole_z2;
  int agc_spatial_iterations;
  FPType agc_spatial_fir_left;
  FPType agc_spatial_fir_mid;
  FPType agc_spatial_fir_right;
  int agc_spatial_n_taps;
  FPType agc_mix_coeffs;
  FPType agc_gain;
  FPType detect_scale;
  FPType decim;
};

// Automatic gain control filter state.
struct AGCState {
  ArrayX agc_memory;
  ArrayX input_accum;
  int decim_phase;
};

#endif  // CARFAC_AGC_H