?? huffman.m
字號(hào):
function [cc,ll,l]=huffman(p,a)
%HUFFMAN calculates a D-ary huffman code [CC,LL]=(P,A)
%
% Inputs: P is a vector or matrix of probabilities
% A(D) is a vector of alphabet characters either integers of chars [default: '01']
% the length of A determines the order of the code
%
% Outputs: CC is a cell array containing the code for each symbol with the sme shape as P
% LL is a vector or matrix of code lengths with the sme shape as P
% L is the average code length
% Copyright (C) Mike Brookes 1995
% Version: $Id: huffman.m,v 1.2 2007/05/04 07:01:38 dmb Exp $
%
% VOICEBOX is a MATLAB toolbox for speech processing.
% Home page: 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
% http://www.gnu.org/copyleft/gpl.html or by writing to
% Free Software Foundation, Inc.,675 Mass Ave, Cambridge, MA 02139, USA.
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
np=length(p(:));
if nargin <2
a='01';
end
d=length(a);
% first append additional zeros-probability symbols to ensure a full code tree
nx=np+mod(1-np,d-1);
px=zeros(nx,1);
px(1:np)=p(:);
cl=(nx-1)/(d-1); % max potential code length
cd=zeros(nx,cl); % code array
qx=px;
ix=(1:nx)';
dd=(d:-1:1)';
kx=zeros(nx,1);
for i=cl:-1:1
nc=1+i*(d-1);
[rx,jx]=sort(qx); % find the D smallest probabilities
kx(jx)=(1:nc)'; % create a reverse index
cd(:,i)=kx(ix);
ix=max(kx(ix)-d+1,1);
rx(d)=sum(rx(1:d));
qx=rx(d:end);
end
cc=cell(size(p));
ll=zeros(size(p));
for i=1:np
ci=cd(i,cd(i,:)<=d);
ll(i) = length(ci);
cc{i}=a(ci);
end
l=p(:)'*ll(:)/sum(p(:)); % calculate average length
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