diff matlab/bmm/carfac/CARFAC_SAI.m @ 455:f8ba7ad93fa9

Added MATLAB code for Lyon's CAR-FAC filter cascade.

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/matlab/bmm/carfac/CARFAC_SAI.m	Wed Feb 15 21:26:40 2012 +0000
@@ -0,0 +1,70 @@
+% 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 [CF, sai] = CARFAC_SAI(CF, k, n_mics, naps, sai)
+% function sai = CARFAC_SAI(CF_struct, n_mics, naps, sai)
+%
+% Calculate the Stabilized Auditory Image from naps
+%
+
+  threshold_alpha = CF.sai_params.threshold_alpha;
+  threshold_jump = CF.sai_params.threshold_jump_factor;
+  threshold_offset = CF.sai_params.threshold_jump_offset;
+
+  sai2 = reshape(sai,CF.sai_params.sai_width * CF.n_ch,n_mics);
+  naps2 = reshape(naps,CF.n_samp * CF.n_ch,n_mics);
+
+  for mic = 1:n_mics
+    data = naps(k, :, mic)';
+    above_threshold = (CF.sai_state(mic).lastdata > ...
+                       CF.sai_state(mic).thresholds) & ...
+                      (CF.sai_state(mic).lastdata > data);
+    CF.sai_state(mic).thresholds(above_threshold) = ...
+        data(above_threshold) * threshold_jump + threshold_offset;
+    CF.sai_state(mic).thresholds(~above_threshold) = ...
+        CF.sai_state(mic).thresholds(~above_threshold) * threshold_alpha;
+    CF.sai_state(mic).lastdata = data;
+
+    % Update SAI image with strobe data.
+    othermic = 3 - mic;
+
+    % Channels that are above the threhsold
+    above_ch = find(above_threshold);
+
+    % If we are above the threshold, set the trigger index and reset the
+    % sai_index
+    CF.sai_state(mic).trigger_index(above_ch) = k;
+    CF.sai_state(mic).sai_index(above_ch) = 1;
+
+    % Copy the right data from the nap to the sai
+    chans = (1:CF.n_ch)';
+    fromindices = CF.sai_state(mic).trigger_index() + (chans - 1) * CF.n_samp;
+    toindices = min((CF.sai_state(mic).sai_index() + (chans - 1) * ...
+                     CF.sai_params.sai_width), ...
+                     CF.sai_params.sai_width * CF.n_ch);
+    sai2(toindices,mic) = naps2(fromindices,othermic);
+
+    CF.sai_state(mic).trigger_index(:) = CF.sai_state(mic).trigger_index(:) + 1;
+    CF.sai_state(mic).sai_index(:) = CF.sai_state(mic).sai_index(:) + 1;
+
+  end
+
+  sai = reshape(sai2,CF.sai_params.sai_width,CF.n_ch,n_mics);
+  naps = reshape(naps2,CF.n_samp, CF.n_ch,n_mics);
+