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/* -*-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);
}
}
}
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