view matlab/bmm/carfac/SAI_BlendFrameIntoComposite.m @ 610:01986636257a

Second check-in of Alex Brandmeyer's C++ implementation of CARFAC. Addressed style issues and completed implementation of remaining functions. Still needs proper testing of the output stages against the MATLAB version, and runtime functions need improvements in efficiency.

% Copyright 2013, 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 composite_frame = SAI_BlendFrameIntoComposite( ...
  layer_struct, composite_frame)

new_frame = layer_struct.frame;
alpha = layer_struct.alpha;
lag_curve = layer_struct.lag_curve;
target_columns = layer_struct.target_indices;

frame_width = size(new_frame, 2);

% Lags are measured from 0 at the right.
stretched_frame = interp1(new_frame', frame_width - lag_curve)';
alpha = repmat(alpha, size(new_frame, 1), 1);
composite_frame(:, target_columns) = ...
  (1 - alpha) .* composite_frame(:, target_columns) + ...
  alpha .* stretched_frame;