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