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function xo=uquant(xi,varargin);
%-*- texinfo -*-
%@deftypefn {Function} uquant
%@verbatim
%UQUANT Simulate uniform quantization
% Usage: x=uquant(x);
% x=uquant(x,nbits,xmax,...);
%
% UQUANT(x,nbits,xmax) simulates the effect of uniform quantization of
% x using nbits bits. The output is simply x rounded to 2^{nbits}
% different values. The xmax parameters specify the maximal value that
% should be quantifiable.
%
% UQUANT(x,nbits) assumes a maximal quantifiable value of 1.
%
% UQUANT(x) additionally assumes 8 bit quantization.
%
% UQUANT takes the following flags at the end of the input arguments:
%
% 'nbits' Number of bits to use in the quantization. Default is 8.
%
% 'xmax' Maximal quantifiable value. Default is 1.
%
% 's' Use signed quantization. This assumes that the signal
% has a both positive and negative part. Useful for sound
% signals. This is the default.
%
% 'u' Use unsigned quantization. Assumes the signal is positive.
% Negative values are silently rounded to zero.
% Useful for images.
%
% If this function is applied to a complex signal, it will be applied to
% the real and imaginary part separately.
%@end verbatim
%@strong{Url}: @url{http://ltfat.github.io/doc/sigproc/uquant.html}
%@end deftypefn
% Copyright (C) 2005-2016 Peter L. Soendergaard <peter@sonderport.dk>.
% This file is part of LTFAT version 2.3.1
%
% This program is free software: you can redistribute it and/or modify
% it under the terms of the GNU General Public License as published by
% the Free Software Foundation, either version 3 of the License, or
% (at your option) any later version.
%
% This program is distributed in the hope that it will be useful,
% but WITHOUT ANY WARRANTY; without even the implied warranty of
% MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
% GNU General Public License for more details.
%
% You should have received a copy of the GNU General Public License
% along with this program. If not, see <http://www.gnu.org/licenses/>.
% AUTHOR : Peter L. Soendergaard and Bruno Torresani.
% TESTING: OK
% REFERENCE: OK
if nargin<1
error('Too few input parameters.');
end;
% Define initial value for flags and key/value pairs.
definput.flags.sign={'s','u'};
definput.keyvals.nbits=8;
definput.keyvals.xmax=1;
[flags,keyvals,nbits,xmax]=ltfatarghelper({'nbits','xmax'},definput,varargin);
% ------ handle complex values ------------------
if ~isreal(xi)
xo = uquant(real(xi),nbits,xmax,varargin{:}) + ...
i*uquant(imag(xi),nbits,xmax,varargin{:});
return
end;
if nbits<2
error('Must specify at least 2 bits.');
end;
% Calculate number of buckets.
nbuck=2^nbits;
if xmax<max(abs(xi(:)))
error('Signal contains values higher than xmax.');
end;
if flags.do_s
% ------------ unsigned case -----------------
bucksize=xmax/(nbuck/2-1);
xo=round(xi/bucksize)*bucksize;
else
% ------------- signed case------------
bucksize=xmax/(nbuck-.51);
% Thresh all negative values to zero.
xi=xi.*(xi>0);
xo=round(xi/bucksize)*bucksize;
end;
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