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:
   7  *
   8  * This program is free software; you can redistribute it and/or modify
   9  * it under the terms of the GNU General Public License as published by
  10  * the Free Software Foundation; either version 2 of the License, or
  11  * (at your option) any later version.
  12  *
  13  * This program is distributed in the hope that it will be useful,
  14  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  15  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  16  * GNU General Public License for more details.
  17  *
  18  * You should have received a copy of the GNU General Public License
  19  * along with this program; if not, write to the Free Software
  20  * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111, USA.
  21  *****************************************************************************/
  22 #include "defs.h"
  23
  24 #include "int_types.h"
  25 #include "ac3_decoder.h"
  26 #include "ac3_internal.h"
  27
  28 #define NORM 16384
  29
  30 typedef struct prefs_s {
  31     u16 use_dolby_surround;
  32     u16 dual_mono_channel_select;
  33 } prefs_t;
  34
  35 prefs_t global_prefs = {0,0};
  36
  37 /* Pre-scaled downmix coefficients */
  38 static float cmixlev_lut[4] = { 0.2928, 0.2468, 0.2071, 0.2468 };
  39 static float smixlev_lut[4] = { 0.2928, 0.2071, 0.0   , 0.2071 };
  40
  41 /* Downmix into _two_ channels...other downmix modes aren't implemented
  42  * to reduce complexity. Realistically, there aren't many machines around
  43  * with > 2 channel output anyways */
  44
  45 void downmix (ac3dec_t * p_ac3dec, s16 * out_buf)
  46 {
  47     int j;
  48     float right_tmp;
  49     float left_tmp;
  50     float clev,slev;
  51     float *centre = 0, *left = 0, *right = 0, *left_sur = 0, *right_sur = 0;
  52
  53     /*
  54     if (p_ac3dec->bsi.acmod > 7)
  55         intf_ErrMsg( "ac3dec: (downmix) invalid acmod number\n" );
  56     */
  57
  58     /* There are two main cases, with or without Dolby Surround */
  59     if (global_prefs.use_dolby_surround) {
  60         switch(p_ac3dec->bsi.acmod) {
  61         case 7: /* 3/2 */
  62             left      = p_ac3dec->samples.channel[0];
  63             centre    = p_ac3dec->samples.channel[1];
  64             right     = p_ac3dec->samples.channel[2];
  65             left_sur  = p_ac3dec->samples.channel[3];
  66             right_sur = p_ac3dec->samples.channel[4];
  67
  68             for (j = 0; j < 256; j++) {
  69                 right_tmp = 0.2265f * *left_sur++ + 0.2265f * *right_sur++;
  70                 left_tmp  = -1 * right_tmp;
  71                 right_tmp += 0.3204f * *right++ + 0.2265f * *centre;
  72                 left_tmp  += 0.3204f * *left++  + 0.2265f * *centre++;
  73
  74                 *(out_buf++) = left_tmp * NORM;
  75                 *(out_buf++) = right_tmp * NORM;
  76             }
  77             break;
  78
  79         case 6: /* 2/2 */
  80             left      = p_ac3dec->samples.channel[0];
  81             right     = p_ac3dec->samples.channel[1];
  82             left_sur  = p_ac3dec->samples.channel[2];
  83             right_sur = p_ac3dec->samples.channel[3];
  84
  85             for (j = 0; j < 256; j++) {
  86                 right_tmp = 0.2265f * *left_sur++ + 0.2265f * *right_sur++;
  87                 left_tmp  = -1 * right_tmp;
  88                 right_tmp += 0.3204f * *right++;
  89                 left_tmp  += 0.3204f * *left++ ;
  90
  91                 *(out_buf++) = left_tmp * NORM;
  92                 *(out_buf++) = right_tmp * NORM;
  93             }
  94             break;
  95
  96         case 5: /* 3/1 */
  97             left      = p_ac3dec->samples.channel[0];
  98             centre    = p_ac3dec->samples.channel[1];
  99             right     = p_ac3dec->samples.channel[2];
 100             /* Mono surround */
 101             right_sur = p_ac3dec->samples.channel[3];
 102
 103             for (j = 0; j < 256; j++) {
 104                 right_tmp =  0.2265f * *right_sur++;
 105                 left_tmp  = - right_tmp;
 106                 right_tmp += 0.3204f * *right++ + 0.2265f * *centre;
 107                 left_tmp  += 0.3204f * *left++  + 0.2265f * *centre++;
 108
 109                 *(out_buf++) = left_tmp * NORM;
 110                 *(out_buf++) = right_tmp * NORM;
 111             }
 112             break;
 113
 114         case 4: /* 2/1 */
 115             left      = p_ac3dec->samples.channel[0];
 116             right     = p_ac3dec->samples.channel[1];
 117             /* Mono surround */
 118             right_sur = p_ac3dec->samples.channel[2];
 119
 120             for (j = 0; j < 256; j++) {
 121                 right_tmp =  0.2265f * *right_sur++;
 122                 left_tmp  = - right_tmp;
 123                 right_tmp += 0.3204f * *right++;
 124                 left_tmp  += 0.3204f * *left++;
 125
 126                 *(out_buf++) = left_tmp * NORM;
 127                 *(out_buf++) = right_tmp * NORM;
 128             }
 129             break;
 130
 131         case 3: /* 3/0 */
 132             left      = p_ac3dec->samples.channel[0];
 133             centre    = p_ac3dec->samples.channel[1];
 134             right     = p_ac3dec->samples.channel[2];
 135
 136             for (j = 0; j < 256; j++) {
 137                 right_tmp = 0.3204f * *right++ + 0.2265f * *centre;
 138                 left_tmp  = 0.3204f * *left++  + 0.2265f * *centre++;
 139
 140                 *(out_buf++) = left_tmp * NORM;
 141                 *(out_buf++) = right_tmp * NORM;
 142             }
 143             break;
 144
 145         case 2: /* 2/0 */
 146             left = p_ac3dec->samples.channel[0];
 147             right = p_ac3dec->samples.channel[1];
 148
 149             for (j = 0; j < 256; j++) {
 150                 *(out_buf++) = *(left++) * NORM;
 151                 *(out_buf++) = *(right++) * NORM;
 152             }
 153             break;
 154
 155         case 1: /* 1/0 */
 156             /* Mono program! */
 157             right = p_ac3dec->samples.channel[0];
 158
 159             for (j = 0; j < 256; j++) {
 160                 right_tmp = 0.7071f * *right++;
 161
 162                 *(out_buf++) = right_tmp * NORM;
 163                 *(out_buf++) = right_tmp * NORM;
 164             }
 165             break;
 166
 167         case 0: /* 1+1 */
 168             /* Dual mono, output selected by user */
 169             right = p_ac3dec->samples.channel[global_prefs.dual_mono_channel_select];
 170
 171             for (j = 0; j < 256; j++) {
 172                 right_tmp = 0.7071f * *right++;
 173
 174                 *(out_buf++) = right_tmp * NORM;
 175                 *(out_buf++) = right_tmp * NORM;
 176             }
 177             break;
 178         }
 179     } else {
 180         /* Non-Dolby surround downmixes */
 181         switch(p_ac3dec->bsi.acmod) {
 182         case 7: /* 3/2 */
 183             left      = p_ac3dec->samples.channel[0];
 184             centre    = p_ac3dec->samples.channel[1];
 185             right     = p_ac3dec->samples.channel[2];
 186             left_sur  = p_ac3dec->samples.channel[3];
 187             right_sur = p_ac3dec->samples.channel[4];
 188
 189             clev = cmixlev_lut[p_ac3dec->bsi.cmixlev];
 190             slev = smixlev_lut[p_ac3dec->bsi.surmixlev];
 191
 192             for (j = 0; j < 256; j++) {
 193                 right_tmp= 0.4142f * *right++ + clev * *centre   + slev * *right_sur++;
 194                 left_tmp = 0.4142f * *left++  + clev * *centre++ + slev * *left_sur++;
 195
 196                 *(out_buf++) = left_tmp * NORM;
 197                 *(out_buf++) = right_tmp * NORM;
 198             }
 199             break;
 200
 201         case 6: /* 2/2 */
 202             left      = p_ac3dec->samples.channel[0];
 203             right     = p_ac3dec->samples.channel[1];
 204             left_sur  = p_ac3dec->samples.channel[2];
 205             right_sur = p_ac3dec->samples.channel[3];
 206
 207             slev = smixlev_lut[p_ac3dec->bsi.surmixlev];
 208
 209             for (j = 0; j < 256; j++) {
 210                 right_tmp= 0.4142f * *right++ + slev * *right_sur++;
 211                 left_tmp = 0.4142f * *left++  + slev * *left_sur++;
 212
 213                 *(out_buf++) = left_tmp * NORM;
 214                 *(out_buf++) = right_tmp * NORM;
 215             }
 216             break;
 217
 218         case 5: /* 3/1 */
 219             left      = p_ac3dec->samples.channel[0];
 220             centre    = p_ac3dec->samples.channel[1];
 221             right     = p_ac3dec->samples.channel[2];
 222             /* Mono surround */
 223             right_sur = p_ac3dec->samples.channel[3];
 224
 225             clev = cmixlev_lut[p_ac3dec->bsi.cmixlev];
 226             slev = smixlev_lut[p_ac3dec->bsi.surmixlev];
 227
 228             for (j = 0; j < 256; j++) {
 229                 right_tmp= 0.4142f * *right++ + clev * *centre   + slev * *right_sur;
 230                 left_tmp = 0.4142f * *left++  + clev * *centre++ + slev * *right_sur++;
 231
 232                 *(out_buf++) = left_tmp * NORM;
 233                 *(out_buf++) = right_tmp * NORM;
 234             }
 235             break;
 236
 237         case 4: /* 2/1 */
 238             left      = p_ac3dec->samples.channel[0];
 239             right     = p_ac3dec->samples.channel[1];
 240             /* Mono surround */
 241             right_sur = p_ac3dec->samples.channel[2];
 242
 243             slev = smixlev_lut[p_ac3dec->bsi.surmixlev];
 244
 245             for (j = 0; j < 256; j++) {
 246                 right_tmp= 0.4142f * *right++ + slev * *right_sur;
 247                 left_tmp = 0.4142f * *left++  + slev * *right_sur++;
 248
 249                 *(out_buf++) = left_tmp * NORM;
 250                 *(out_buf++) = right_tmp * NORM;
 251             }
 252             break;
 253
 254         case 3: /* 3/0 */
 255             left      = p_ac3dec->samples.channel[0];
 256             centre    = p_ac3dec->samples.channel[1];
 257             right     = p_ac3dec->samples.channel[2];
 258
 259             clev = cmixlev_lut[p_ac3dec->bsi.cmixlev];
 260
 261             for (j = 0; j < 256; j++) {
 262                 right_tmp= 0.4142f * *right++ + clev * *centre;
 263                 left_tmp = 0.4142f * *left++  + clev * *centre++;
 264
 265                 *(out_buf++) = left_tmp * NORM;
 266                 *(out_buf++) = right_tmp * NORM;
 267             }
 268             break;
 269
 270         case 2: /* 2/0 */
 271             left = p_ac3dec->samples.channel[0];
 272             right = p_ac3dec->samples.channel[1];
 273
 274             for (j = 0; j < 256; j++) {
 275                 *(out_buf++) = *(left++) * NORM;
 276                 *(out_buf++) = *(right++) * NORM;
 277             }
 278             break;
 279
 280         case 1: /* 1/0 */
 281             /* Mono program! */
 282             right = p_ac3dec->samples.channel[0];
 283
 284             for (j = 0; j < 256; j++) {
 285                 right_tmp = 0.7071f * *right++;
 286
 287                 *(out_buf++) = right_tmp * NORM;
 288                 *(out_buf++) = right_tmp * NORM;
 289             }
 290             break;
 291
 292         case 0: /* 1+1 */
 293             /* Dual mono, output selected by user */
 294             right = p_ac3dec->samples.channel[global_prefs.dual_mono_channel_select];
 295
 296             for (j = 0; j < 256; j++) {
 297                 right_tmp = 0.7071f * *right++;
 298
 299                 *(out_buf++) = right_tmp * NORM;
 300                 *(out_buf++) = right_tmp * NORM;
 301             }
 302             break;
 303         }
 304     }
 305 }