autoPolynomial LPC_Frame_to_Polynomial (LPC_Frame me) {
long degree = (long) my nCoefficients;
autoPolynomial thee = Polynomial_create (-1, 1, degree);
for (long i = 1; i <= degree; i++) {
thy coefficients[i] = my a[degree - i + 1];
}
thy coefficients[degree + 1] = 1.0;
return thee;
}
static void burg (double sample [], long nsamp_window, double cof [], int nPoles,
Formant_Frame frame, double nyquistFrequency, double safetyMargin)
{
double a0;
NUMburg (sample, nsamp_window, cof, nPoles, & a0);
/*
* Convert LP coefficients to polynomial.
*/
autoPolynomial polynomial = Polynomial_create (-1, 1, nPoles);
for (int i = 1; i <= nPoles; i ++)
polynomial -> coefficients [i] = - cof [nPoles - i + 1];
polynomial -> coefficients [nPoles + 1] = 1.0;
/*
* Find the roots of the polynomial.
*/
autoRoots roots = Polynomial_to_Roots (polynomial.peek());
Roots_fixIntoUnitCircle (roots.peek());
Melder_assert (frame -> nFormants == 0 && ! frame -> formant);
/*
* First pass: count the formants.
* The roots come in conjugate pairs, so we need only count those above the real axis.
*/
for (int i = roots -> min; i <= roots -> max; i ++) if (roots -> v [i]. im >= 0) {
double f = fabs (atan2 (roots -> v [i].im, roots -> v [i].re)) * nyquistFrequency / NUMpi;
if (f >= safetyMargin && f <= nyquistFrequency - safetyMargin)
frame -> nFormants ++;
}
/*
* Create space for formant data.
*/
if (frame -> nFormants > 0)
frame -> formant = NUMvector <structFormant_Formant> (1, frame -> nFormants);
/*
* Second pass: fill in the formants.
*/
int iformant = 0;
for (int i = roots -> min; i <= roots -> max; i ++) if (roots -> v [i]. im >= 0.0) {
double f = fabs (atan2 (roots -> v [i].im, roots -> v [i].re)) * nyquistFrequency / NUMpi;
if (f >= safetyMargin && f <= nyquistFrequency - safetyMargin) {
Formant_Formant formant = & frame -> formant [++ iformant];
formant -> frequency = f;
formant -> bandwidth = -
log (roots -> v [i].re * roots -> v [i].re + roots -> v [i].im * roots -> v [i].im) * nyquistFrequency / NUMpi;
}
}
Melder_assert (iformant == frame -> nFormants); // may fail if some frequency is NaN
}
