function [u,v]=pow2cep(m,c,mode)
%CEP2POW convert cepstral means and variances to the power domain
% for now, we insist that u is a row vector
% cepstral vector includes the 0'th coefficient
% mode: 'c'  pow=exp(irdct(cep))   [default]
%       'f'  pow=exp(rsfft(cep)/n)  [fft length even]
%       'fo' pow=exp(rsfft(cep)/n)  [fft length odd]


%      Copyright (C) Mike Brookes 1998
%
%      Last modified Wed Jan 30 09:44:14 2002
%
%   VOICEBOX is a MATLAB toolbox for speech processing. Home page is at
%   http://www.ee.ic.ac.uk/hp/staff/dmb/voicebox/voicebox.html
%
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%   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 2 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 can obtain a copy of the GNU General Public License from
%   ftp://prep.ai.mit.edu/pub/gnu/COPYING-2.0 or by writing to
%   Free Software Foundation, Inc.,675 Mass Ave, Cambridge, MA 02139, USA.
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

if nargin<3 mode='c'; end
if min(size(c))==1
   v=diag(c);
end
q=log(1+c./(m'*m));
p=log(m)-0.5*diag(q)';
if any(mode=='f')
   n=2*length(m)-2;
   if any(mode=='o')
      n=n+1;
   end
   u=rsfft(p,n);
   v=rsfft(rsfft(q,n)',n);
else
   u=rdct(p);
   v=rdct(rdct(q)');
end