ref: 2bc0f84e01dfb29b9253d7b7313a0f0bd619f5a1
dir: /libfaad/is.c/
/*
** FAAD - Freeware Advanced Audio Decoder
** Copyright (C) 2002 M. Bakker
**
** 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.
**
** $Id: is.c,v 1.10 2002/11/28 18:48:30 menno Exp $
**/
#include "common.h"
#include "structs.h"
#include "syntax.h"
#include "is.h"
#ifdef FIXED_POINT
static real_t pow05_table[] = {
COEF_CONST(1.68179283050743), /* 0.5^(-3/4) */
COEF_CONST(1.41421356237310), /* 0.5^(-2/4) */
COEF_CONST(1.18920711500272), /* 0.5^(-1/4) */
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, k;
#ifndef FIXED_POINT
real_t scale;
#else
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))
{
/* 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;
#ifndef FIXED_POINT
scale = (real_t)pow(0.5, (0.25*icsr->scale_factors[g][sfb]));
#else
exp = icsr->scale_factors[g][sfb] / 4;
frac = icsr->scale_factors[g][sfb] % 4;
#endif
/* Scale from left to right channel,
do not touch left channel */
for (i = icsr->swb_offset[sfb]; i < icsr->swb_offset[sfb+1]; i++)
{
k = (group*nshort)+i;
#ifndef FIXED_POINT
r_spec[k] = MUL(l_spec[k], scale);
#else
if (exp < 0)
r_spec[k] = l_spec[k] << -exp;
else
r_spec[k] = l_spec[k] >> exp;
r_spec[k] = MUL_R_C(r_spec[k], pow05_table[frac + 3]);
#endif
if (is_intensity(icsr, g, sfb) != invert_intensity(ics, g, sfb))
r_spec[k] = -r_spec[k];
}
}
}
group++;
}
}
}