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ricedeco.m

## Copyright (C) 2006 Muthiah Annamalai <muthiah.annamalai@uta.edu>
## 
## 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 should have received a copy of the GNU General Public License
## along with this program; If not, see <http://www.gnu.org/licenses/>.
##

## -*- texinfo -*-
## @deftypefn {Function File} {} ricedeco (@var{code}, @var{K})
##
## Returns the Rice decoded signal vector using @var{code} and @var{K}. 
## Compulsory K is need to be specified.
## A restrictions is that a signal set must strictly be non-negative.
## The value of code is a cell array of row-vectors which have the 
## encoded rice value for a single sample. The Rice algorithm is
##  used to encode the 'code' and only that can be meaningfully 
## decoded. @var{code} is assumed to have been of format generated
## by the function @code{riceenco}.
##
## Reference: Solomon Golomb, Run length Encodings, 1966 IEEE Trans Info' Theory
##
## An exmaple of the use of @code{ricedeco} is
## @example
## @group
##   ricedec(riceenco(1:4,2),2) 
##  
## @end group
## @end example
## @end deftypefn
## @seealso{riceenco}

##
##
##! /usr/bin/octave -q
##A stress test routine
##for i=1:100
##  sig=abs(randint(1,10,[0,255]));
##  [code,k]=riceenco(sig)
##  sig_d=ricedeco(code,k)
##  if(isequal(sig_d,sig)~=1)
##    error('Some mistake in ricedeco/enco pair');
##  end
##end
##
function sig_op=ricedeco(code,K)
  if ( nargin < 2 ) || (strcmp(class(code),"cell")~=1)
    error('usage: ricedeco(code,K)');
  end

  L=length(code);
  
  K_pow_2=2**K;

  if(K ~= 0)
    power_seq=[2.^((K-1):-1:0)];
    for j=1:L
      word=code{j};
      idx=find(word==0)(1);
      val=sum(word(1:idx));
      sig_op(j)=val*K_pow_2 + sum(word(idx+1:end).*power_seq);
    end
  else
    for j=1:L
      sig_op(j)=sum(code{j});
    end
  end
  
  return
end
%! 
%! assert(ricedeco(riceenco(1:4,2),2),[1:4])
%! 

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