/* Roots_and_Formant.cpp
 *
 * Copyright (C) 1994-2026 David Weenink
 *
 * This code is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 3 of the License, or (at
 * your option) any later version.
 *
 * This code is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this work. If not, see <http://www.gnu.org/licenses/>.
 */

#include "Roots_and_Formant.h"

static void Formant_Frame_sort (Formant_Frame me) {
	const integer n = my numberOfFormants;
	for (integer i = 1; i < n; i ++) {
		double min = my formant [i]. frequency;
		integer imin = i;
		for (integer j = i + 1; j <= n; j ++)
			if (my formant [j]. frequency < min) {
				min = my formant [j]. frequency;
				imin = j;
			}
		if (imin != i)
			std::swap (my formant [imin], my formant [i]);
	}
}

void Roots_into_Formant_Frame (constRoots me, Formant_Frame thee, double samplingFrequency, double margin) {
	/*
		Determine the formants and bandwidths
	*/
	Melder_pre (my numberOfRoots == my roots.size);   // check invariant
	thy formant. resize (0);
	const double nyquistFrequency = 0.5 * samplingFrequency;
	const double fLow = margin, fHigh = nyquistFrequency - margin;
	for (integer iroot = 1; iroot <= my numberOfRoots; iroot ++) {
		if (my roots [iroot].imag() < 0.0)
			continue;
		const double frequency = fabs (atan2 (my roots [iroot].imag(), my roots [iroot].real())) * nyquistFrequency / NUMpi;
		if (frequency >= fLow && frequency <= fHigh) {
			const double bandwidth = - log (norm (my roots [iroot])) * nyquistFrequency / NUMpi;
			Formant_Formant newff = thy formant. append ();
			newff -> frequency = frequency;
			newff -> bandwidth = bandwidth;
		}
	}
	thy numberOfFormants = thy formant.size;   // maintain invariant
	Formant_Frame_sort (thee);
}

/* End of file Roots_and_Formant.h */
