Add a useful package (from Source forge) for octave

[CreaPhase.git] / octave_packages / communications-1.1.1 / riceenco.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} {} riceenco (@var{sig}, @var{K})
+##
+## Returns the Rice encoded signal using @var{K} or optimal K . 
+## Default optimal K is chosen between 0-7. Currently no other way
+## to increase the range except to specify explicitly. Also returns
+## @var{K} parameter used (in case it were to be chosen optimally) 
+## and @var{Ltot} the total length of output code in bits.
+## This function uses a @var{K} if supplied or by default chooses
+## the optimal K for encoding signal vector into a rice coded vector.
+## A restrictions is that a signal set must strictly be non-negative.
+## The Rice algorithm is used to encode the data into unary coded
+## quotient part which is represented as a set of 1's separated from
+## the K-part (binary) using a zero. This scheme doesnt need any 
+## kind of dictionaries and its close to O(N), but this implementation
+## *may be* sluggish, though correct.
+##
+## Reference: Solomon Golomb, Run length Encodings, 1966 IEEE Trans
+## Info' Theory
+##
+## An exmaple of the use of @code{riceenco} is
+## @example
+## @group
+##   riceenco(1:4) #  
+##   riceenco(1:10,2) # 
+## @end group
+## @end example
+## @end deftypefn
+## @seealso{ricedeco}
+
+function [rcode,K,Ltot]=riceenco(sig,K)
+  if ( nargin < 1 )
+    error('usage: riceenco(sig,{K})');
+  elseif (nargin < 2)
+    use_optimal_k=1;
+  else
+    use_optimal_k=0;
+  end
+
+  if (min(sig) < 0)
+    error("signal has elements that are outside alphabet set ...
+       . Accepts only non-negative numbers. Cannot encode.");
+  end
+
+    
+  L=length(sig);
+
+  ##compute the optimal rice parameter.
+  if(use_optimal_k)
+    k_opt=0;
+    len_past=sum(sig)+L+k_opt*L;
+    quot=sig;
+    
+    for k=1:7
+      k_pow_2=2**k;
+      quot_k=floor(sig./k_pow_2);
+      len=sum(quot_k)+L+k*L;
+      if(len < len_past)
+       len_past=len;
+       k_opt=k;
+       rem=mod(sig,k_pow_2);
+       quot=quot_k;
+      end
+    end
+    Ltot=len_past;
+    K=k_opt;
+    K_pow_2=2**K;
+  else
+    K_pow_2=2**K;
+    quot=floor(sig./K_pow_2);
+    rem=mod(sig,K_pow_2);
+  end
+
+  for j=1:L
+    rice_part=zeros(1,K);
+    %
+    % How can we eliminate this loop?
+    % I essentially need to get the binary
+    % representation of rem(j) in the rice_part(i)
+    %
+    for i=K:-1:1
+      rice_part(i)=mod(rem(j),2);
+      rem(j)=floor(rem(j)/2);
+    end
+    rcode{j}=[ones(1,quot(j)) 0 rice_part];
+  end
+  Ltot=sum(quot)+L+K*L;
+  
+  return
+end
+%! 
+%! assert(riceenco(1:4,2),{[0 0 1],[0 1 0], [0 1 1], [ 1 0 0 0]})
+%!