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function lsf=poly2lsf(a)
//poly2lsf Prediction polynomial to line spectral frequencies.
// Calling Sequence
// lsf = poly2lsf(a)
// Parameters
// k: define the prediction polynomial.
// lsf: returns corresponding line spectral frequencies.
// Examples
//
//EXAMPLE
//X=[1 0.6149 0.9899 0 0.0031 -0.0082]
// lsf = poly2lsf(X)
//EXPECTED OUTPUT:
//lsf =0.7841731 1.5605415 1.8776459 1.8984313 2.3592523
//
// Author
// Jitendra Singh
//modified to match MATLAb o/p
if(find(a(1,1)==0)==1) then
error ("Input to ROOTS must not contain NaN or Inf");
end //end of modification
if or(type(a)==10) then
error ('The polynomial must have all roots inside of the unit circle.')
end
if (size(a,1) > 1) & (size(a,2) > 1)
error('The prediction polynomial must be stored in a vector.')
end
if ~isreal(a) then
error('Line spectral frequencies are not defined for complex polynomials.')
end
if (max(abs(roots(a))) >= 1) then
error('The polynomial must have all roots inside of the unit circle.');
end
if a(1) ~= 1 then
a = a./a(1);
end
a=a(:);
p = length(a)-1;
a1 = [a;0];
a2 = a1($:-1:1);
pp = a1-a2;
qq = a1+a2;
if (p-fix(p./2).*2)~=0 then // Odd order
//////////////////////////////
aa=[1 0 -1];
[m,n] = size(pp);
n = max(m,n);
na = length(aa);
if na > n
P = 0;
else
P= filter(pp, aa, [1 zeros(1,n-na)]);
if m ~= 1
P = P(:);
end
end
Q = qq;
else // Even order
aa=[1 -1];
[m,n] = size(pp);
n = max(m,n);
na = length
(aa);
if na > n
P = 0;
else
P= filter(pp, aa, [1 zeros(1,n-na)]);
if m ~= 1
P = P(:);
end
end
aa=[1 1];
[m,n] = size(qq);
n = max(m,n);
na = length(aa);
if na > n
Q = 0;
else
Q= filter(qq, aa, [1 zeros(1,n-na)]);
if m ~= 1
Q = Q(:);
end
end
end
r_p = roots(P); r_q = roots(Q);
ap =atan(imag(r_p(1:2:$)),real(r_p(1:2:$)));
aq = atan(imag(r_q(1:2:$)),real(r_q(1:2:$)));
lsf = mtlb_sort([ap;aq]);
endfunction
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