libfaad2/ms.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: ms.c,v 1.17 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 "ms.h"
  33 #include "is.h"
  34 #include "pns.h"
  35
  36 void ms_decode(ic_stream *ics, ic_stream *icsr, real_t *l_spec, real_t *r_spec,
  37                uint16_t frame_len)
  38 {
  39     uint8_t g, b, sfb;
  40     uint8_t group = 0;
  41     uint16_t nshort = frame_len/8;
  42
  43     uint16_t i, k;
  44     real_t tmp;
  45
  46     if (ics->ms_mask_present >= 1)
  47     {
  48         for (g = 0; g < ics->num_window_groups; g++)
  49         {
  50             for (b = 0; b < ics->window_group_length[g]; b++)
  51             {
  52                 for (sfb = 0; sfb < ics->max_sfb; sfb++)
  53                 {
  54                     /* If intensity stereo coding or noise substitution is on
  55                        for a particular scalefactor band, no M/S stereo decoding
  56                        is carried out.
  57                      */
  58                     if ((ics->ms_used[g][sfb] || ics->ms_mask_present == 2) &&
  59                         !is_intensity(icsr, g, sfb) && !is_noise(ics, g, sfb))
  60                     {
  61                         for (i = ics->swb_offset[sfb]; i < ics->swb_offset[sfb+1]; i++)
  62                         {
  63                             k = (group*nshort) + i;
  64                             tmp = l_spec[k] - r_spec[k];
  65                             l_spec[k] = l_spec[k] + r_spec[k];
  66                             r_spec[k] = tmp;
  67                         }
  68                     }
  69                 }
  70                 group++;
  71             }
  72         }
  73     }
  74 }