lsfxlp.m

ITU-T G.723.1 Speech Coder: Matlab implementation This package implements the speech coder and de

function a = LSFxLP (lsf, LSFpar)
% Convert LSF's to LP coefficients. Optionally modify the LSF
% values to account for the use of linear interpolation of a
% cosine table as used in the G.723.1 procedure.
%   lsf: Column vectors of LSF parameters

% $Id: LSFxLP.m 1.1 2004/07/06 G.723.1-v2r1a $

% In G.723.1, the conversion from LSFs to LP coefficients is carried
% out in the x = cos(w) domain. The conversion to the x-domain is
% done via linear interpolation into a cosine table. Here we modify
% the LSF's to take into account the error in the conversion to x values.
if (isfield (LSFpar.Fix, 'CosTable'))
  NCos = length (LSFpar.Fix.CosTable);
  w = (0:(NCos-1)) * 2 * pi / NCos;     % w runs from 0 to 2*pi
  x = interp1 (w, LSFpar.Fix.CosTable, lsf, 'linear');
  lsf = acos (x);
end

% Convert to LP coefficients
N = size (lsf, 2);
for (i = 1:N)
  ai = lsf2poly (lsf(:,i));   % Inconsistent: aI is a row vector
  a(:,i) = ai(:);
end

return