function g=check_lsf(f,delta_f_min);
% Syntax: g=check_lsf(f,delta_f_min);
% 
% Function for checking the minimal distance of Line Spectrum Frequencies LSF.
% f is the column vector of normalized LSFs (Fe=1), size P, where P
% is the order of prediction/synthesis filter. 
% delta_f_min (optional) is the minimal difference of two LSFs. The
% default is 0.01 (which is equivalent to 80Hz in case Fe=8000Hz).
% The function is also forcing f(1) not to be zero - min. is delta_f_min.
% the vectors f and g are COLUMN.

if(nargin == 1),		% default
  delta_f_min=0.01;
end

M=length(f);
f=[0; f];

for i=2:M+1,
  if f(i)-f(i-1) < delta_f_min,
    f(i) = f(i-1) + delta_f_min;
  end
end

if f(M+1) > 0.5,
  disp ('check_lsf: warning - the last LSF after the checking is greater than 1/2');
end
     
g=f(2:M+1);