dicklyon@527: % Copyright 2012, Google, Inc.
dicklyon@527: % Author: Richard F. Lyon
dicklyon@527: %
dicklyon@527: % This Matlab file is part of an implementation of Lyon's cochlear model:
dicklyon@527: % "Cascade of Asymmetric Resonators with Fast-Acting Compression"
dicklyon@527: % to supplement Lyon's upcoming book "Human and Machine Hearing"
dicklyon@527: %
dicklyon@527: % Licensed under the Apache License, Version 2.0 (the "License");
dicklyon@527: % you may not use this file except in compliance with the License.
dicklyon@527: % You may obtain a copy of the License at
dicklyon@527: %
dicklyon@527: %     http://www.apache.org/licenses/LICENSE-2.0
dicklyon@527: %
dicklyon@527: % Unless required by applicable law or agreed to in writing, software
dicklyon@527: % distributed under the License is distributed on an "AS IS" BASIS,
dicklyon@527: % WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
dicklyon@527: % See the License for the specific language governing permissions and
dicklyon@527: % limitations under the License.
dicklyon@527: 
dicklyon@523: function stage_state = CARFAC_Spatial_Smooth(coeffs, stage, stage_state)
dicklyon@523: % function AGC_state = CARFAC_Spatial_Smooth( ...
dicklyon@523: %   n_taps, n_iterations, FIR_coeffs, AGC_state)
dicklyon@523: 
dicklyon@523: n_iterations = coeffs.AGC_spatial_iterations(stage);
dicklyon@523: 
dicklyon@523: use_FIR = n_iterations < 4;  % or whatever condition we want to try
dicklyon@523: 
dicklyon@523: if use_FIR
dicklyon@523:   FIR_coeffs = coeffs.AGC_spatial_FIR(:,stage);
dicklyon@536:   switch coeffs.AGC_spatial_n_taps(stage)
dicklyon@523:     case 3
dicklyon@523:       for iter = 1:n_iterations
dicklyon@523:         stage_state = ...
dicklyon@523:           FIR_coeffs(1) * stage_state([1, 1:(end-1)], :) + ...
dicklyon@523:           FIR_coeffs(2) * stage_state + ...
dicklyon@523:           FIR_coeffs(3) * stage_state([2:end, end], :);
dicklyon@523:       end
dicklyon@523:     case 5  % 5-tap smoother duplicates first and last coeffs:
dicklyon@523:       for iter = 1:n_iterations
dicklyon@523:         stage_state = ...
dicklyon@534:           FIR_coeffs(1) * (stage_state([1, 2, 1:(end-2)], :) + ...
dicklyon@523:           stage_state([1, 1:(end-1)], :)) + ...
dicklyon@523:           FIR_coeffs(2) *  stage_state + ...
dicklyon@523:           FIR_coeffs(3) * (stage_state([2:end, end], :) + ...
dicklyon@534:           stage_state([3:end, end, end-1], :));
dicklyon@523:       end
dicklyon@523:     otherwise
dicklyon@536:       error('Bad AGC_spatial_n_taps in CARFAC_Spatial_Smooth');
dicklyon@523:   end
dicklyon@523: else
dicklyon@536:   % use IIR method, back-and-forth first-order smoothers:
dicklyon@523:   stage_state = SmoothDoubleExponential(stage_state, ...
dicklyon@523:     coeffs.AGC_polez1(stage), coeffs.AGC_polez2(stage));
dicklyon@523: end