/* -*-mode:java; c-basic-offset:2; indent-tabs-mode:nil -*- */
/* JOrbis
 * Copyright (C) 2000 ymnk, JCraft,Inc.
 *  
 * Written by: 2000 ymnk<ymnk@jcraft.com>
 *   
 * Many thanks to 
 *   Monty <monty@xiph.org> and 
 *   The XIPHOPHORUS Company http://www.xiph.org/ .
 * JOrbis has been based on their awesome works, Vorbis codec.
 *   
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Library General Public License
 * as published by the Free Software Foundation; either version 2 of
 * the License, or (at your option) any later version.
   
 * This program 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 Library General Public License for more details.
 * 
 * You should have received a copy of the GNU Library General Public
 * License along with this program; if not, write to the Free Software
 * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
 */

package com.jcraft.jorbis;

/*
  function: LSP (also called LSF) conversion routines

  The LSP generation code is taken (with minimal modification) from
  "On the Computation of the LSP Frequencies" by Joseph Rothweiler
  <rothwlr@altavista.net>, available at:
  
  http://www2.xtdl.com/~rothwlr/lsfpaper/lsfpage.html 
 ********************************************************************/

class Lsp {

	static final float M_PI = (float) (3.1415926539);

	static void lsp_to_curve(float[] curve, int[] map, int n, int ln, float[] lsp, int m, float amp, float ampoffset) {
		int i;
		float wdel = M_PI / ln;
		for (i = 0; i < m; i++)
			lsp[i] = Lookup.coslook(lsp[i]);
		int m2 = (m / 2) * 2;

		i = 0;
		while (i < n) {
			int k = map[i];
			float p = .7071067812f;
			float q = .7071067812f;
			float w = Lookup.coslook(wdel * k);

			for (int j = 0; j < m2; j += 2) {
				q *= lsp[j] - w;
				p *= lsp[j + 1] - w;
			}

			if ((m & 1) != 0) {
				/* odd order filter; slightly assymetric */
				/* the last coefficient */
				q *= lsp[m - 1] - w;
				q *= q;
				p *= p * (1.f - w * w);
			} else {
				/* even order filter; still symmetric */
				q *= q * (1.f + w);
				p *= p * (1.f - w);
			}

			// q=frexp(p+q,&qexp);
			q = p + q;
			int hx = Float.floatToIntBits(q);
			int ix = 0x7fffffff & hx;
			int qexp = 0;

			if (ix >= 0x7f800000 || (ix == 0)) {
				// 0,inf,nan
			} else {
				if (ix < 0x00800000) { // subnormal
					q *= 3.3554432000e+07; // 0x4c000000
					hx = Float.floatToIntBits(q);
					ix = 0x7fffffff & hx;
					qexp = -25;
				}
				qexp += ((ix >>> 23) - 126);
				hx = (hx & 0x807fffff) | 0x3f000000;
				q = Float.intBitsToFloat(hx);
			}

			q = Lookup.fromdBlook(amp * Lookup.invsqlook(q) * Lookup.invsq2explook(qexp + m) - ampoffset);

			do {
				curve[i++] *= q;
			} while (i < n && map[i] == k);

		}
	}
}
