dicklyon@466: % Copyright 2012, Google, Inc.
dicklyon@466: % Author: Richard F. Lyon
dicklyon@466: %
dicklyon@466: % This Matlab file is part of an implementation of Lyon's cochlear model:
dicklyon@466: % "Cascade of Asymmetric Resonators with Fast-Acting Compression"
dicklyon@466: % to supplement Lyon's upcoming book "Human and Machine Hearing"
dicklyon@466: %
dicklyon@466: % Licensed under the Apache License, Version 2.0 (the "License");
dicklyon@466: % you may not use this file except in compliance with the License.
dicklyon@466: % You may obtain a copy of the License at
dicklyon@466: %
dicklyon@466: %     http://www.apache.org/licenses/LICENSE-2.0
dicklyon@466: %
dicklyon@466: % Unless required by applicable law or agreed to in writing, software
dicklyon@466: % distributed under the License is distributed on an "AS IS" BASIS,
dicklyon@466: % WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
dicklyon@466: % See the License for the specific language governing permissions and
dicklyon@466: % limitations under the License.
dicklyon@466: 
dicklyon@462: function stage_state = CARFAC_Spatial_Smooth(coeffs, stage, stage_state)
dicklyon@462: % function AGC_state = CARFAC_Spatial_Smooth( ...
dicklyon@462: %   n_taps, n_iterations, FIR_coeffs, AGC_state)
dicklyon@462: 
dicklyon@462: n_iterations = coeffs.AGC_spatial_iterations(stage);
dicklyon@462: 
dicklyon@462: use_FIR = n_iterations < 4;  % or whatever condition we want to try
dicklyon@462: 
dicklyon@462: if use_FIR
dicklyon@462:   FIR_coeffs = coeffs.AGC_spatial_FIR(:,stage);
dicklyon@462:   switch coeffs.AGC_n_taps(stage)
dicklyon@462:     case 3
dicklyon@462:       for iter = 1:n_iterations
dicklyon@462:         stage_state = ...
dicklyon@462:           FIR_coeffs(1) * stage_state([1, 1:(end-1)], :) + ...
dicklyon@462:           FIR_coeffs(2) * stage_state + ...
dicklyon@462:           FIR_coeffs(3) * stage_state([2:end, end], :);
dicklyon@462:       end
dicklyon@462:     case 5  % 5-tap smoother duplicates first and last coeffs:
dicklyon@462:       for iter = 1:n_iterations
dicklyon@462:         stage_state = ...
dicklyon@473:           FIR_coeffs(1) * (stage_state([1, 2, 1:(end-2)], :) + ...
dicklyon@462:           stage_state([1, 1:(end-1)], :)) + ...
dicklyon@462:           FIR_coeffs(2) *  stage_state + ...
dicklyon@462:           FIR_coeffs(3) * (stage_state([2:end, end], :) + ...
dicklyon@473:           stage_state([3:end, end, end-1], :));
dicklyon@462:       end
dicklyon@462:     otherwise
dicklyon@462:       error('Bad n_taps in CARFAC_Spatial_Smooth');
dicklyon@462:   end
dicklyon@462: else
dicklyon@462:   % use IIR method, back-and-forth firt-order smoothers:
dicklyon@462:   stage_state = SmoothDoubleExponential(stage_state, ...
dicklyon@462:     coeffs.AGC_polez1(stage), coeffs.AGC_polez2(stage));
dicklyon@462: end