annotate matlab/bmm/carfac/CARFAC_AGC_Step.m @ 611:0fbaf443ec82

Carfac C++ revision 3, indluding more style improvements. The output structs are now classes again, and have separate storage methods for each output structure along with flags in the Run and RunSegment methods to allow for only storing NAPs if desired.

% Copyright 2012, Google, Inc.
% Author: Richard F. Lyon
%
% This Matlab 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.

function [state, updated] = CARFAC_AGC_Step(detects, coeffs, state)
% function [state, updated] = CARFAC_AGC_Step(detects, coeffs, state)
%
% one time step of the AGC state update; decimates internally

stage = 1;
AGC_in = coeffs.detect_scale * detects;
[state, updated] = CARFAC_AGC_Recurse(coeffs, AGC_in, stage, state);


function [state, updated] = CARFAC_AGC_Recurse(coeffs, AGC_in, ...
  stage, state)
% function [state, updated] = CARFAC_AGC_Recurse(coeffs, AGC_in, ...
%   stage, state)

% decim factor for this stage, relative to input or prev. stage:
decim = coeffs.decimation(stage);
% decim phase of this stage (do work on phase 0 only):
decim_phase = mod(state(1).decim_phase(stage) + 1, decim);
state.decim_phase(stage) = decim_phase;

% accumulate input for this stage from detect or previous stage:
state.input_accum(:, stage) = state.input_accum(:, stage) + 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 = state.input_accum(:, stage) / decim;
  state.input_accum(:, stage) = 0;  % reset accumulator
  
  if stage < length(coeffs.decimation)  % recurse to evaluate next stage(s)
    state = CARFAC_AGC_Recurse(coeffs, AGC_in, stage+1, state);
    % and add its output to this stage input, whether it updated or not:
    AGC_in = AGC_in + coeffs.AGC_stage_gain * state.AGC_memory(:, stage+1);
  end
  
  AGC_stage_state = state.AGC_memory(:, stage);
  % first-order recursive smoothing filter update, in time:
  AGC_stage_state = AGC_stage_state + ...
    coeffs.AGC_epsilon(stage) * (AGC_in - AGC_stage_state);
  % spatial smooth:
  AGC_stage_state = ...
    CARFAC_Spatial_Smooth(coeffs, stage, AGC_stage_state);
  % and store the state back (in C++, do it all in place?)
  state.AGC_memory(:, stage) = AGC_stage_state;
  
  updated = 1;  % bool to say we have new state
else
  updated = 0;
end