function [optsigmin,optsigmax] = hauth2020_ecprocess4optsigs(optsigL,optsigR,ECparams,fs,bin_inaccuracy)
%HAUTH2020_ECPROCESS4OPTSIGS Equalization-Cancellation process 
%
%   Usage:
%     [optsigmin,optsigmax] = hauth2020_ecprocess4optsigs(optsigL,optsigR,ECparams,fs,bin_inaccuracy)
%
%   Input parameters:
%     optsigL        : left ear optional signal
%     optsigR        : right ear optional signal
%     ECparams       : Parameters for the EC process
%     fs             : sampling frequency
%     bin_inaccuracy : flag indicating the use of (1) binaural processing
%                      inaccuracies or (0) assuming binaural processing to be deterministic
%
%   Output parameters: 
%     optsigmin      : EC processed optional signal using minimization strategy
%     optsigmax      : EC processed optional signal using maximization strategy
%
%
%   HAUTH2020_ECPROCESS4OPTSIGS applies the Equalization-Cancellation 
%   process in the frequency domain to the optional signals.
%   The Equalization is applied two both ears symmetrically.
%
%   Url: http://amtoolbox.org/amt-1.6.0/doc/modelstages/hauth2020_ecprocess4optsigs.php


%   #StatusDoc: Good
%   #StatusCode: Good
%   #Verification: Unknown
%   #Requirements: MATLAB M-Signal
%   #Author: Christopher F. Hauth (2020)
%   #Author: Dr. Thomas Brand (2020)

% This file is licensed unter the GNU General Public License (GPL) either 
% version 3 of the license, or any later version as published by the Free Software 
% Foundation. Details of the GPLv3 can be found in the AMT directory "licences" and 
% at <https://www.gnu.org/licenses/gpl-3.0.html>. 
% You can redistribute this file and/or modify it under the terms of the GPLv3. 
% This file is distributed without any warranty; without even the implied warranty 
% of merchantability or fitness for a particular purpose. 

%--------------------------------------------------------------------------

orig_len = length(optsigL);
optsigLFFT = fft(optsigL,ECparams.fftpoints); 
optsigRFFT = fft(optsigR,ECparams.fftpoints);

f = linspace(0,fs/2,floor(ECparams.fftpoints./2+1))';
 % invert frequency vector for complex conjugate
f_inv = f(end-1:-1:2); 
 % frequency vector in rad
omega = 2.*pi*[f;f_inv];
 
 % copy signals to generate buffer for processed signals
FFToptsigLeq = optsigLFFT;
FFToptsigReq = optsigRFFT;
%--------------------------------------------------------------------------
                %% Apply Equalization Mechanism %%
% calculate phase factor for left and right ear with a set of gaussian
% distributed RVs as binaural processing inaccuracies
if bin_inaccuracy
    for kk = 1:size(ECparams.errorLR,2)
        phaseL(:,kk) = exp(-1j.*omega(1:(end/2)+1).*(ECparams.EC_tau./2 + ECparams.errorLR(1,kk)));
        phaseR(:,kk) = exp(+1j.*omega(1:(end/2)+1).*(ECparams.EC_tau./2 + ECparams.errorLR(2,kk)));
        % complex conjugate
        phaseLcc(:,kk) = exp(+1j.*omega((end/2)+2:end).*(ECparams.EC_tau./2 + ECparams.errorLR(1,kk)));
        phaseRcc(:,kk) = exp(-1j.*omega((end/2)+2:end).*(ECparams.EC_tau./2 + ECparams.errorLR(2,kk)));
    end
    % take the mean over all phase terms to obtain averaged processing
    % binaural processing inaccuracy
    phaseL   = mean(phaseL,2);
    phaseLcc = mean(phaseLcc,2);
    phaseR   = mean(phaseR,2);
    phaseRcc = mean(phaseRcc,2);
else
        phaseL = exp(-1j.*omega(1:(end/2)+1).*(ECparams.EC_tau./2));
        phaseR = exp(+1j.*omega(1:(end/2)+1).*(ECparams.EC_tau./2));
        % complex conjugate
        phaseLcc = exp(+1j.*omega((end/2)+2:end).*(ECparams.EC_tau./2));
        phaseRcc = exp(-1j.*omega((end/2)+2:end).*(ECparams.EC_tau./2));
end
% modify signals
% Left ear
FFToptsigLeq(1:(end/2)+1)  = FFToptsigLeq(1:(end/2)+1).*phaseL;
FFToptsigLeq((end/2)+2:end)= FFToptsigLeq((end/2)+2:end).*phaseLcc;
 
% Right ear 
FFToptsigReq(1:(end/2)+1)  = FFToptsigReq(1:(end/2)+1).*phaseR;
FFToptsigReq((end/2)+2:end)= FFToptsigReq((end/2)+2:end).*phaseRcc;
%--------------------------------------------------------------------------
                    %% Apply Cancellation %%
FFToptsigMin = FFToptsigLeq - FFToptsigReq; % destructive interference
FFToptsigMax = FFToptsigLeq + FFToptsigReq; % constructive interference
%--------------------------------------------------------------------------
                    %% Apply IFFT and cut signals
 % Level minimization
 optsigmin = real(ifft(FFToptsigMin));
 optsigmin = optsigmin(1:orig_len);
 
 % Level maximization
 optsigmax = real(ifft(FFToptsigMax));
 optsigmax = optsigmax(1:orig_len);              
%--------------------Licence ---------------------------------------------
% Copyright (c) <2020> Christopher Hauth
% Dept. Medical Physics and Acoustics
% Carl von Ossietzky University Oldenburg 
% Permission is hereby granted, free of charge, to any person obtaining 
% a copy of this software and associated documentation files 
% (the "Software"), to deal in the Software without restriction, including 
% without limitation the rights to use, copy, modify, merge, publish, 
% distribute, sublicense, and/or sell copies of the Software, and to 
% permit persons to whom the Software is furnished to do so, subject 
% to the following conditions:
% The above copyright notice and this permission notice shall be included 
% in all copies or substantial portions of the Software.

% THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, 
% EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES 
% OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. 
% IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY 
% CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, 
% TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE 
% SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
% END OF FILE