www.pudn.com > hmm--matlab.rar > viterbi.m, change:2005-06-22,size:1013b

function [prob,q] = viterbi(hmm,O) 
%viterbi算法 
%输入： 
% hmm--hmm模型 
% O--输入观察序列，N*D，N为帧数，D为向量维数 
% 输出： 
% prob--输出序列 
% q--状态序列 
 
init = hmm.init; %初始概率 
trans = hmm.trans; %转移概率 
mix = hmm.mix;  %高阶混合 
N = hmm.N;  %HMM的状态数 
T = size(O,1); %语音帧数 
 
%计算log(init) 
ind1 = find(init>0); 
ind0 = find(init<=0); 
init(ind0) = -inf; 
init(ind1) = log(init(ind1)); 
 
%计算log(trans) 
ind1 = find(trans>0); 
ind0 = find(trans<=0); 
trans(ind0) = -inf; 
trans(ind1) = log(trans(ind1)); 
 
%初始化 
delta = zeros(T,N); 
fai = zeros(T,N); 
q = zeros(T,1); 
 
%t=1 
x = O(1,:); 
for i =1:N 
    delta(1,i) = init(i)+log(mixture(mix(i),x)); 
end 
 
%t=2:T 
for t=2:T 
    for j=1:N 
        [delta(t,j) fai(t,j)] = max(delta(t-1,:)+trans(:,j)'); 
        x = O(t,:); 
        delta(t,j) = delta(t,j)+log(mixture(mix(j),x)); 
    end 
end 
 
%最终概率和最后节点 
[prob q(T)] = max(delta(T,:)); 
 
%回溯最佳状态路径 
for t=T-1:-1:1 
    q(t) = fai(t+1,q(t+1)); 
end