function y = LR2MS(x)
% LR2MS Converts stereo audio signal to MS (mid side).
% 
% by Brecht De Man at Centre for Digital Music, 4 June 2013

if min(size(x)) ~= 2
    error('Function LR2MS needs a stereo audio input file.');
end

y = zeros(size(x));

% M = L+R, S = L-R
y(:,1) = x(1,:) + x(2,:); % mid
y(:,2) = x(1,:) - x(2,:); % side

% normalise if necessary
if max(max(abs(y))) >= 1
    y = y/max(max(abs(y)));
end

end