/*** FAAD2 - Freeware Advanced Audio (AAC) Decoder including SBR decoding** Copyright (C) 2003-2005 M. Bakker, Nero AG, http://www.nero.com**** This program 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 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 General Public License for more details.**** You should have received a copy of the GNU General Public License** along with this program; if not, write to the Free Software** Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.**** Any non-GPL usage of this software or parts of this software is strictly** forbidden.**** The "appropriate copyright message" mentioned in section 2c of the GPLv2** must read: "Code from FAAD2 is copyright (c) Nero AG, www.nero.com"**** Commercial non-GPL licensing of this software is possible.** For more info contact Nero AG through Mpeg4AAClicense@nero.com.**** $Id: is.c,v 1.28 2007/11/01 12:33:31 menno Exp $**/ #include "common.h"#include "structs.h" #include "syntax.h"#include "is.h" #ifdef FIXED_POINTstatic real_t pow05_table[] = {    COEF_CONST(1.0),              /* 0.5^( 0/4) */    COEF_CONST(0.84089641525371), /* 0.5^(+1/4) */    COEF_CONST(0.70710678118655), /* 0.5^(+2/4) */    COEF_CONST(0.59460355750136)  /* 0.5^(+3/4) */};#endif void is_decode(ic_stream *ics, ic_stream *icsr, real_t *l_spec, real_t *r_spec,               uint16_t frame_len){    uint8_t g, sfb, b;    uint16_t i;    real_t scale;#ifdef FIXED_POINT    int32_t exp, frac;#endif     uint16_t nshort = frame_len/8;    uint8_t group = 0;     for (g = 0; g < icsr->num_window_groups; g++)    {        /* Do intensity stereo decoding */        for (b = 0; b < icsr->window_group_length[g]; b++)        {            for (sfb = 0; sfb < icsr->max_sfb; sfb++)            {                if (is_intensity(icsr, g, sfb))                {                    int16_t scale_factor = icsr->scale_factors[g][sfb];#ifdef MAIN_DEC                    /* For scalefactor bands coded in intensity stereo the                       corresponding predictors in the right channel are                       switched to "off".                     */                    ics->pred.prediction_used[sfb] = 0;                    icsr->pred.prediction_used[sfb] = 0;#endif #ifndef FIXED_POINT                    scale_factor = min(max(scale_factor, -120), 120);                    scale = (real_t)pow(0.5, (0.25*scale_factor));#else                    scale_factor = min(max(scale_factor, -60), 60);                    exp = scale_factor >> 2; /* exp is -15..15 */                    frac = scale_factor & 3;                    scale = pow05_table[frac];                    exp += COEF_BITS - REAL_BITS; /* exp is -1..29 */                    if (exp < 0)                        scale <<= -exp;                    else                        scale >>= exp;#endif                     /* Scale from left to right channel,                       do not touch left channel */                    for (i = icsr->swb_offset[sfb]; i < min(icsr->swb_offset[sfb+1], ics->swb_offset_max); i++)                    {                        r_spec[(group*nshort)+i] = MUL_R(l_spec[(group*nshort)+i], scale);                        if (is_intensity(icsr, g, sfb) != invert_intensity(ics, g, sfb))                            r_spec[(group*nshort)+i] = -r_spec[(group*nshort)+i];                    }                }            }            group++;        }    }}