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function [outsig, sigweight] = rangecompress(insig,varargin)
%-*- texinfo -*-
%@deftypefn {Function} rangecompress
%@verbatim
%RANGECOMPRESS Compress the dynamic range of a signal
% Usage: [outsig, sigweight] = rangecompress(insig,mu);
%
% [outsig, sigweight]=RANGECOMPRESS(insig,mu) range-compresss the input
% signal insig using mu-law range-compression with parameter mu.
%
% RANGECOMPRESS takes the following optional arguments:
%
% 'mulaw' Do mu-law compression, this is the default.
%
% 'alaw' Do A-law compression.
%
% 'mu',mu mu-law parameter. Default value is 255.
%
% 'A',A A-law parameter. Default value is 87.7.
%
% The following plot shows how the output range is compressed for input
% values between 0 and 1:
%
% x=linspace(0,1,100);
% xc=rangecompress(x);
% plot(x,xc);
% xlabel('input');
% ylabel('output');
% title('mu-law compression');
%
% References:
% S. Jayant and P. Noll. Digital Coding of Waveforms: Principles and
% Applications to Speech and Video. Prentice Hall, 1990.
%
%
%@end verbatim
%@strong{Url}: @url{http://ltfat.github.io/doc/auditory/rangecompress.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: Bruno Torresani and Peter L. Soendergaard
if nargin<1
error('%s: Too few input parameters.',upper(mfilename));
end;
definput.flags.method={'mulaw','alaw'};
definput.keyvals.mu=255;
definput.keyvals.A=87.7;
[flags,kv]=ltfatarghelper({},definput,varargin);
if flags.do_mulaw
tmp = log(1+kv.mu);
sigweight = max(abs(insig(:)));
outsig = sign(insig) .* log(1+kv.mu*abs(insig))/tmp;
end;
if flags.do_alaw
absx=abs(insig);
tmp=1+log(kv.A);
mask=absx<1/kv.A;
outsig = sign(insig).*(mask.*kv.A.*absx./tmp+(1-mask).*(1+log(kv.A*absx))/tmp);
end;
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