function [c,vmean]=sphinx2cov(list,dir,ext,vecsize,number);
% c=sphinx2cov(list,dir,ext,vecsize,number);
% computes covar matrice out of a list of SPhinx files. 
% number is optional and can limit the no of used files. 

if nargin==4
  number = inf;
end

% alloc matrices
vmean=zeros(1,vecsize); 
sum2 = zeros (vecsize,vecsize); 
X = [];

% go round 
N=0; files=0;
ff=fopen(list,'r');
while (files < number)
  ss=fscanf(ff, '%s',[1 1]); if (isempty(ss)) break; end
%  name=[dir '/features/' ss '.fea'];  %disp(name);
  name=[dir '/' ss '.' ext]; 
  [m,veccount]=read_sphinx (name,vecsize); %X = [X m];
  disp([ num2str(files) ' ' num2str(veccount) ' ' name]);
  % update matrices: 
  vmean = vmean + sum(m');
  sum2 = sum2 + m * m';
  
  N=N+veccount;
  files=files+1;
end
fclose(ff);

% compute the covar matrix:
vmean = vmean /N;
c = sum2/N - vmean' * vmean;