2 ** FAAD2 - Freeware Advanced Audio (AAC) Decoder including SBR decoding
3 ** Copyright (C) 2003-2005 M. Bakker, Nero AG, http://www.nero.com
5 ** This program is free software; you can redistribute it and/or modify
6 ** it under the terms of the GNU General Public License as published by
7 ** the Free Software Foundation; either version 2 of the License, or
8 ** (at your option) any later version.
10 ** This program is distributed in the hope that it will be useful,
11 ** but WITHOUT ANY WARRANTY; without even the implied warranty of
12 ** MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
13 ** GNU General Public License for more details.
15 ** You should have received a copy of the GNU General Public License
16 ** along with this program; if not, write to the Free Software
17 ** Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
19 ** Any non-GPL usage of this software or parts of this software is strictly
22 ** The "appropriate copyright message" mentioned in section 2c of the GPLv2
23 ** must read: "Code from FAAD2 is copyright (c) Nero AG, www.nero.com"
25 ** Commercial non-GPL licensing of this software is possible.
26 ** For more info contact Nero AG through Mpeg4AAClicense@nero.com.
28 ** $Id: is.c,v 1.28 2007/11/01 12:33:31 menno Exp $
38 static real_t pow05_table[] = {
39 COEF_CONST(1.68179283050743), /* 0.5^(-3/4) */
40 COEF_CONST(1.41421356237310), /* 0.5^(-2/4) */
41 COEF_CONST(1.18920711500272), /* 0.5^(-1/4) */
42 COEF_CONST(1.0), /* 0.5^( 0/4) */
43 COEF_CONST(0.84089641525371), /* 0.5^(+1/4) */
44 COEF_CONST(0.70710678118655), /* 0.5^(+2/4) */
45 COEF_CONST(0.59460355750136) /* 0.5^(+3/4) */
49 void is_decode(ic_stream *ics, ic_stream *icsr, real_t *l_spec, real_t *r_spec,
60 uint16_t nshort = frame_len/8;
63 for (g = 0; g < icsr->num_window_groups; g++)
65 /* Do intensity stereo decoding */
66 for (b = 0; b < icsr->window_group_length[g]; b++)
68 for (sfb = 0; sfb < icsr->max_sfb; sfb++)
70 if (is_intensity(icsr, g, sfb))
73 /* For scalefactor bands coded in intensity stereo the
74 corresponding predictors in the right channel are
77 ics->pred.prediction_used[sfb] = 0;
78 icsr->pred.prediction_used[sfb] = 0;
82 scale = (real_t)pow(0.5, (0.25*icsr->scale_factors[g][sfb]));
84 exp = icsr->scale_factors[g][sfb] >> 2;
85 frac = icsr->scale_factors[g][sfb] & 3;
88 /* Scale from left to right channel,
89 do not touch left channel */
90 for (i = icsr->swb_offset[sfb]; i < min(icsr->swb_offset[sfb+1], ics->swb_offset_max); i++)
93 r_spec[(group*nshort)+i] = MUL_R(l_spec[(group*nshort)+i], scale);
96 r_spec[(group*nshort)+i] = l_spec[(group*nshort)+i] << -exp;
98 r_spec[(group*nshort)+i] = l_spec[(group*nshort)+i] >> exp;
99 r_spec[(group*nshort)+i] = MUL_C(r_spec[(group*nshort)+i], pow05_table[frac + 3]);
101 if (is_intensity(icsr, g, sfb) != invert_intensity(ics, g, sfb))
102 r_spec[(group*nshort)+i] = -r_spec[(group*nshort)+i];