view trunk/matlab/bmm/carfac/smooth1d.m @ 690:76f749d29b48

Fix memory leak in CARFAC.

Also get rid of most uses of auto, which tend to hurt readability
unless the type name is particularly long, especially when it masks
pointers.

% Copyright 2010, 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 cols = smooth1d(cols, scale)
% smooth1d - Smooth the columns of the input.
%
% output = smooth1d(input, smoothing_factor)
%
% Smooth the columns of input using a one-pole smoothing filter, using the
% provided smoothing factor.
%
% TODO(dross, dicklyon): make this code satisfy the google3 Matlab style.

[nr, nc, nl] = size(cols);
if nr == 1
    if nl == 1
        cols = cols';
        [nr, nc, nl] = size(cols);
    else
        disp('error in shape passed to smooth1d')
    end
end

if scale==0
    polez = 0; % no smoothing at all
    return;
else
    % this coefficient matches the curvature at DC of a discrete Gaussian:
    t = scale^2;
    polez = 1 + 1/t - sqrt((1+1/t)^2 - 1); % equiv. to the one below
    % polez = 1 + 1/t - sqrt((2/t) + 1/t^2); % equiv. to the one above
    % polez is Z position of real pole
end

[x, state] = filter(1-polez, [1, -polez], cols);
cols = cols(end:-1:1,:);
[cols, state] = filter(1-polez, [1, -polez], cols, state);
cols = cols(end:-1:1,:);
[cols, state] = filter(1-polez, [1, -polez], cols, state);

return