libfaad2/is.c

   1 /*
   2 ** FAAD2 - Freeware Advanced Audio (AAC) Decoder including SBR decoding
   3 ** Copyright (C) 2003-2004 M. Bakker, Ahead Software AG, http://www.nero.com
   4 **
   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.
   9 **
  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.
  14 **
  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.
  18 **
  19 ** Any non-GPL usage of this software or parts of this software is strictly
  20 ** forbidden.
  21 **
  22 ** Commercial non-GPL licensing of this software is possible.
  23 ** For more info contact Ahead Software through Mpeg4AAClicense@nero.com.
  24 **
  25 ** $Id: is.c,v 1.24 2004/09/04 14:56:28 menno Exp $
  26 **/
  27
  28 #include "common.h"
  29 #include "structs.h"
  30
  31 #include "syntax.h"
  32 #include "is.h"
  33
  34 #ifdef FIXED_POINT
  35 static real_t pow05_table[] = {
  36     COEF_CONST(1.68179283050743), /* 0.5^(-3/4) */
  37     COEF_CONST(1.41421356237310), /* 0.5^(-2/4) */
  38     COEF_CONST(1.18920711500272), /* 0.5^(-1/4) */
  39     COEF_CONST(1.0),              /* 0.5^( 0/4) */
  40     COEF_CONST(0.84089641525371), /* 0.5^(+1/4) */
  41     COEF_CONST(0.70710678118655), /* 0.5^(+2/4) */
  42     COEF_CONST(0.59460355750136)  /* 0.5^(+3/4) */
  43 };
  44 #endif
  45
  46 void is_decode(ic_stream *ics, ic_stream *icsr, real_t *l_spec, real_t *r_spec,
  47                uint16_t frame_len)
  48 {
  49     uint8_t g, sfb, b;
  50     uint16_t i;
  51 #ifndef FIXED_POINT
  52     real_t scale;
  53 #else
  54     int32_t exp, frac;
  55 #endif
  56
  57     uint16_t nshort = frame_len/8;
  58     uint8_t group = 0;
  59
  60     for (g = 0; g < icsr->num_window_groups; g++)
  61     {
  62         /* Do intensity stereo decoding */
  63         for (b = 0; b < icsr->window_group_length[g]; b++)
  64         {
  65             for (sfb = 0; sfb < icsr->max_sfb; sfb++)
  66             {
  67                 if (is_intensity(icsr, g, sfb))
  68                 {
  69 #ifdef MAIN_DEC
  70                     /* For scalefactor bands coded in intensity stereo the
  71                        corresponding predictors in the right channel are
  72                        switched to "off".
  73                      */
  74                     ics->pred.prediction_used[sfb] = 0;
  75                     icsr->pred.prediction_used[sfb] = 0;
  76 #endif
  77
  78 #ifndef FIXED_POINT
  79                     scale = (real_t)pow(0.5, (0.25*icsr->scale_factors[g][sfb]));
  80 #else
  81                     exp = icsr->scale_factors[g][sfb] >> 2;
  82                     frac = icsr->scale_factors[g][sfb] & 3;
  83 #endif
  84
  85                     /* Scale from left to right channel,
  86                        do not touch left channel */
  87                     for (i = icsr->swb_offset[sfb]; i < icsr->swb_offset[sfb+1]; i++)
  88                     {
  89 #ifndef FIXED_POINT
  90                         r_spec[(group*nshort)+i] = MUL_R(l_spec[(group*nshort)+i], scale);
  91 #else
  92                         if (exp < 0)
  93                             r_spec[(group*nshort)+i] = l_spec[(group*nshort)+i] << -exp;
  94                         else
  95                             r_spec[(group*nshort)+i] = l_spec[(group*nshort)+i] >> exp;
  96                         r_spec[(group*nshort)+i] = MUL_C(r_spec[(group*nshort)+i], pow05_table[frac + 3]);
  97 #endif
  98                         if (is_intensity(icsr, g, sfb) != invert_intensity(ics, g, sfb))
  99                             r_spec[(group*nshort)+i] = -r_spec[(group*nshort)+i];
 100                     }
 101                 }
 102             }
 103             group++;
 104         }
 105     }
 106 }