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

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