/*

** 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_POINT

static 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++;

        }

    }

}