% -*- texinfo -*- % @deftypefn {Function File} {[@var{table}, @var{codes}] = } lloyds (@var{sig},@var{init_codes}) % @deftypefnx {Function File} {[@var{table}, @var{codes}] = } lloyds (@var{sig},@var{len}) % @deftypefnx {Function File} {[@var{table}, @var{codes}] = } lloyds (@var{sig},@var{...},@var{tol}) % @deftypefnx {Function File} {[@var{table}, @var{codes}] = } lloyds (@var{sig},@var{...},@var{tol},@var{type}) % @deftypefnx {Function File} {[@var{table}, @var{codes}, @var{dist}] = } lloyds (@var{...}) % @deftypefnx {Function File} {[@var{table}, @var{codes}, @var{dist}, @var{reldist}] = } lloyds (@var{...}) % % Optimize the quantization table and codes to reduce distortion. This is % based on the article by Lloyd % % S. Lloyd @emph{Least squared quantization in PCM}, IEEE Trans Inform % Thoery, Mar 1982, no 2, p129-137 % % which describes an iterative technique to reduce the quantization error % by making the intervals of the table such that each interval has the same % area under the PDF of the training signal @var{sig}. The initial codes to % try can either be given in the vector @var{init_codes} or as scalar % @var{len}. In the case of a scalar the initial codes will be an equi-spaced % vector of length @var{len} between the minimum and maximum value of the % training signal. % % The stopping criteria of the iterative algorithm is given by % % @example % abs(@var{dist}(n) - @var{dist}(n-1)) < max(@var{tol}, abs(@var{eps}*max(@var{sig})) % @end example % % By default @var{tol} is 1.e-7. The final input argument determines how the % updated table is created. By default the centroid of the values of the % training signal that fall within the interval described by @var{codes} % are used to update @var{table}. If @var{type} is any other string than % 'centroid', this behaviour is overriden and @var{table} is updated as % follows. % % @example % @var{table} = (@var{code}(2:length(@var{code})) + @var{code}(1:length(@var{code}-1))) / 2 % @end example % % The optimized values are returned as @var{table} and @var{code}. In % addition the distortion of the the optimized codes representing the % training signal is returned as @var{dist}. The relative distortion in % the final iteration is also returned as @var{reldist}. % % @end deftypefn % @seealso{quantiz}

- quantiz %

- comms %

Generated on Sat 16-May-2009 00:04:49 by