Add a useful package (from Source forge) for octave

[CreaPhase.git] / octave_packages / communications-1.1.1 / golombdeco.m

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+## 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 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/>.
+
+## -*- texinfo -*-
+## @deftypefn {Function File} {} golombdeco (@var{code}, @var{m})
+##
+## Returns the Golomb decoded signal vector using @var{code} and @var{m}. 
+## Compulsory m 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 golomb value
+## for a single sample. The Golomb 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{golombenco}. Also the parameter @var{m} need to
+## be a non-zero number, unless which it makes divide-by-zero errors.
+## This function works backward the Golomb algorithm see
+## @code{golombenco} for more detials on that.
+## Reference: Solomon Golomb, Run length Encodings, 1966 IEEE Trans Info' Theory
+##
+## An exmaple of the use of @code{golombdeco} is
+## @example
+## @group
+##   golombdeco(golombenco(1:4,2),2)
+## @end group
+## @end example
+## @end deftypefn
+## @seealso{golombenco}
+
+##! /usr/bin/octave -q
+#A stress test routine
+#for i=1:100
+#  sig=abs(randint(1,10,[0,255]));
+#  k=mod(i,10)+1;
+#  code=golombenco(sig,k);
+#  assert(golombdeco(code,k),sig)
+#end
+#
+#for k=1:10;
+# assert(golombdeco(golombenco(4:10,k),k),[4:10]);
+#end
+#
+function sig_op=golombdeco(code,m)
+  if ( nargin < 2 ) || (strcmp(class(code),"cell")~=1 || m<=0)
+    error('usage: golombdeco(code,m)');
+  end
+  
+  L=length(code);  
+  C=ceil(log2(m));
+  partition_limit=2**C-m;
+ 
+
+  power_seq=[2.^(ceil(log2(m))-1:-1:0)];
+  power_seq_mod=power_seq(2:end);
+  
+  for j=1:L
+    word=code{j};
+    WL=length(word);
+    idx=find(word==0)(1);
+    q=sum(word(1:idx));
+    
+    idx2=(WL-idx);
+    word_tail=word(idx+1:end);
+  
+    if(length(word_tail) == C)
+      r=sum(word_tail.*power_seq);
+      r=r-(partition_limit);
+    else
+      r=sum(word_tail.*power_seq_mod);
+    end
+    
+    quot(j)=q;
+    rem(j)=r;
+  end
+  sig_op=quot.*m + rem;
+
+  return
+end
+%! 
+%! assert(golombdeco(golombenco(1:4,2),2),[1:4])
+%!