103 lines
2.8 KiB
Java
103 lines
2.8 KiB
Java
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/* -*-mode:java; c-basic-offset:2; indent-tabs-mode:nil -*- */
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/* JOrbis
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* Copyright (C) 2000 ymnk, JCraft,Inc.
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*
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* Written by: 2000 ymnk<ymnk@jcraft.com>
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*
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* Many thanks to
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* Monty <monty@xiph.org> and
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* The XIPHOPHORUS Company http://www.xiph.org/ .
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* JOrbis has been based on their awesome works, Vorbis codec.
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU Library General Public License
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* as published by the Free Software Foundation; either version 2 of
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* the License, or (at your option) any later version.
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU Library General Public License for more details.
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*
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* You should have received a copy of the GNU Library General Public
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* License along with this program; if not, write to the Free Software
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* Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
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*/
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package com.jcraft.jorbis;
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/*
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function: LSP (also called LSF) conversion routines
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The LSP generation code is taken (with minimal modification) from
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"On the Computation of the LSP Frequencies" by Joseph Rothweiler
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<rothwlr@altavista.net>, available at:
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http://www2.xtdl.com/~rothwlr/lsfpaper/lsfpage.html
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********************************************************************/
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class Lsp {
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static final float M_PI = (float) (3.1415926539);
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static void lsp_to_curve(float[] curve, int[] map, int n, int ln, float[] lsp, int m, float amp, float ampoffset) {
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int i;
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float wdel = M_PI / ln;
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for (i = 0; i < m; i++)
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lsp[i] = Lookup.coslook(lsp[i]);
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int m2 = (m / 2) * 2;
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i = 0;
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while (i < n) {
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int k = map[i];
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float p = .7071067812f;
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float q = .7071067812f;
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float w = Lookup.coslook(wdel * k);
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for (int j = 0; j < m2; j += 2) {
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q *= lsp[j] - w;
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p *= lsp[j + 1] - w;
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}
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if ((m & 1) != 0) {
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/* odd order filter; slightly assymetric */
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/* the last coefficient */
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q *= lsp[m - 1] - w;
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q *= q;
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p *= p * (1.f - w * w);
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} else {
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/* even order filter; still symmetric */
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q *= q * (1.f + w);
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p *= p * (1.f - w);
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}
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// q=frexp(p+q,&qexp);
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q = p + q;
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int hx = Float.floatToIntBits(q);
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int ix = 0x7fffffff & hx;
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int qexp = 0;
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if (ix >= 0x7f800000 || (ix == 0)) {
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// 0,inf,nan
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} else {
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if (ix < 0x00800000) { // subnormal
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q *= 3.3554432000e+07; // 0x4c000000
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hx = Float.floatToIntBits(q);
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ix = 0x7fffffff & hx;
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qexp = -25;
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}
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qexp += ((ix >>> 23) - 126);
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hx = (hx & 0x807fffff) | 0x3f000000;
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q = Float.intBitsToFloat(hx);
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}
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q = Lookup.fromdBlook(amp * Lookup.invsqlook(q) * Lookup.invsq2explook(qexp + m) - ampoffset);
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do {
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curve[i++] *= q;
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} while (i < n && map[i] == k);
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}
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}
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}
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