dicklyon@534: % Copyright 2012, Google, Inc.
dicklyon@534: % Author: Richard F. Lyon
dicklyon@534: %
dicklyon@534: % This Matlab file is part of an implementation of Lyon's cochlear model:
dicklyon@534: % "Cascade of Asymmetric Resonators with Fast-Acting Compression"
dicklyon@534: % to supplement Lyon's upcoming book "Human and Machine Hearing"
dicklyon@534: %
dicklyon@534: % Licensed under the Apache License, Version 2.0 (the "License");
dicklyon@534: % you may not use this file except in compliance with the License.
dicklyon@534: % You may obtain a copy of the License at
dicklyon@534: %
dicklyon@534: %     http://www.apache.org/licenses/LICENSE-2.0
dicklyon@534: %
dicklyon@534: % Unless required by applicable law or agreed to in writing, software
dicklyon@534: % distributed under the License is distributed on an "AS IS" BASIS,
dicklyon@534: % WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
dicklyon@534: % See the License for the specific language governing permissions and
dicklyon@534: % limitations under the License.
dicklyon@534: 
dicklyon@565: function [state, updated] = CARFAC_AGC_Step(detects, coeffs, state)
dicklyon@565: % function [state, updated] = CARFAC_AGC_Step(detects, coeffs, state)
dicklyon@534: %
dicklyon@559: % one time step of the AGC state update; decimates internally
dicklyon@534: 
dicklyon@534: stage = 1;
dicklyon@665: AGC_in = coeffs(1).detect_scale * detects;
dicklyon@559: [state, updated] = CARFAC_AGC_Recurse(coeffs, AGC_in, stage, state);
dicklyon@534: 
dicklyon@534: 
dicklyon@559: function [state, updated] = CARFAC_AGC_Recurse(coeffs, AGC_in, ...
dicklyon@559:   stage, state)
dicklyon@559: % function [state, updated] = CARFAC_AGC_Recurse(coeffs, AGC_in, ...
dicklyon@559: %   stage, state)
dicklyon@534: 
dicklyon@559: % decim factor for this stage, relative to input or prev. stage:
dicklyon@665: decim = coeffs(stage).decimation;
dicklyon@559: % decim phase of this stage (do work on phase 0 only):
dicklyon@665: decim_phase = mod(state(stage).decim_phase + 1, decim);
dicklyon@665: state(stage).decim_phase = decim_phase;
dicklyon@534: 
dicklyon@534: % accumulate input for this stage from detect or previous stage:
dicklyon@665: state(stage).input_accum = state(stage).input_accum + AGC_in;
dicklyon@534: 
dicklyon@534: % nothing else to do if it's not the right decim_phase
dicklyon@534: if decim_phase == 0
dicklyon@559:   % do lots of work, at decimated rate.
dicklyon@559:   % decimated inputs for this stage, and to be decimated more for next:
dicklyon@665:   AGC_in = state(stage).input_accum / decim;
dicklyon@665:   state(stage).input_accum(:) = 0;  % reset accumulator
dicklyon@534:   
dicklyon@665:   if stage < coeffs(1).n_AGC_stages
dicklyon@559:     state = CARFAC_AGC_Recurse(coeffs, AGC_in, stage+1, state);
dicklyon@559:     % and add its output to this stage input, whether it updated or not:
dicklyon@665:     AGC_in = AGC_in + ...
dicklyon@665:       coeffs(stage).AGC_stage_gain * state(stage + 1).AGC_memory;
dicklyon@534:   end
dicklyon@534:   
dicklyon@665:   AGC_stage_state = state(stage).AGC_memory;
dicklyon@559:   % first-order recursive smoothing filter update, in time:
dicklyon@559:   AGC_stage_state = AGC_stage_state + ...
dicklyon@665:     coeffs(stage).AGC_epsilon * (AGC_in - AGC_stage_state);
dicklyon@559:   % spatial smooth:
dicklyon@559:   AGC_stage_state = ...
dicklyon@665:     CARFAC_Spatial_Smooth(coeffs(stage), AGC_stage_state);
dicklyon@559:   % and store the state back (in C++, do it all in place?)
dicklyon@665:   state(stage).AGC_memory = AGC_stage_state;
dicklyon@534:   
dicklyon@534:   updated = 1;  % bool to say we have new state
dicklyon@534: else
dicklyon@534:   updated = 0;
dicklyon@534: end