git.sesse.net Git - vlc/blob - src/ac3_decoder/ac3_downmix.c

   1 /*****************************************************************************
   2  * ac3_downmix.c: ac3 downmix functions
   3  *****************************************************************************
   4  * Copyright (C) 1999, 2000 VideoLAN
   5  * $Id: ac3_downmix.c,v 1.18 2001/03/21 13:42:34 sam Exp $
   6  *
   7  * Authors: Michel Kaempf <maxx@via.ecp.fr>
   8  *          Aaron Holtzman <aholtzma@engr.uvic.ca>
   9  *          Renaud Dartus <reno@videolan.org>
  10  *
  11  * This program is free software; you can redistribute it and/or modify
  12  * it under the terms of the GNU General Public License as published by
  13  * the Free Software Foundation; either version 2 of the License, or
  14  * (at your option) any later version.
  15  *
  16  * This program is distributed in the hope that it will be useful,
  17  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  18  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  19  * GNU General Public License for more details.
  20  *
  21  * You should have received a copy of the GNU General Public License
  22  * along with this program; if not, write to the Free Software
  23  * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111, USA.
  24  *****************************************************************************/
  25 #include "defs.h"
  26
  27 #include "int_types.h"
  28 #include "ac3_decoder.h"
  29 #include "ac3_internal.h"
  30
  31 #include "ac3_downmix.h"
  32
  33 /* Pre-scaled downmix coefficients */
  34 static const float cmixlev_lut[4] = { 0.2928, 0.2468, 0.2071, 0.2468 };
  35 static const float smixlev_lut[4] = { 0.2928, 0.2071, 0.0   , 0.2071 };
  36
  37 /* Downmix into _two_ channels...other downmix modes aren't implemented
  38  * to reduce complexity. Realistically, there aren't many machines around
  39  * with > 2 channel output anyways */
  40
  41 int __inline__ downmix (ac3dec_t * p_ac3dec, float * channel, s16 * out_buf)
  42 {
  43
  44     dm_par_t    dm_par;
  45
  46     dm_par.clev = 0.0;
  47     dm_par.slev = 0.0;
  48     dm_par.unit = 1.0;
  49
  50     if (p_ac3dec->bsi.acmod & 0x1) /* have center */
  51         dm_par.clev = cmixlev_lut[p_ac3dec->bsi.cmixlev];
  52
  53     if (p_ac3dec->bsi.acmod & 0x4) /* have surround channels */
  54         dm_par.slev = smixlev_lut[p_ac3dec->bsi.surmixlev];
  55
  56     dm_par.unit /= 1.0 + dm_par.clev + dm_par.slev;
  57     dm_par.clev *= dm_par.unit;
  58     dm_par.slev *= dm_par.unit;
  59
  60
  61     /*
  62     if (p_ac3dec->bsi.acmod > 7)
  63         intf_ErrMsg( "ac3dec: (downmix) invalid acmod number" );
  64     */
  65
  66     switch(p_ac3dec->bsi.acmod)
  67     {
  68         case 7:         // 3/2
  69                     downmix_3f_2r_to_2ch_c (channel, &dm_par);
  70                         break;
  71                 case 6:         // 2/2
  72                         downmix_2f_2r_to_2ch_c (channel, &dm_par);
  73                         break;
  74                 case 5:         // 3/1
  75                         downmix_3f_1r_to_2ch_c (channel, &dm_par);
  76                         break;
  77                 case 4:         // 2/1
  78                         downmix_2f_1r_to_2ch_c (channel, &dm_par);
  79                         break;
  80                 case 3:         // 3/0
  81                         downmix_3f_0r_to_2ch_c (channel, &dm_par);
  82                         break;
  83                 case 2:
  84                         break;
  85                 default:        // 1/0
  86             /* FIXME
  87                         if (p_ac3dec->bsi.acmod == 1)
  88                                 center = p_ac3dec->samples.channel[0];
  89                         else if (p_ac3dec->bsi.acmod == 0)
  90                                 center = p_ac3dec->samples.channel[0]; */
  91             return 1;
  92         }
  93     return 0;
  94 }
  95