libmpeg3/audio/exponents.c

   1 /*
   2  *
   3  *      exponents.c Copyright (C) Aaron Holtzman - May 1999
   4  *
   5  *  This file is part of libmpeg3
   6  *
   7  *  libmpeg3 is free software; you can redistribute it and/or modify
   8  *  it under the terms of the GNU General Public License as published by
   9  *  the Free Software Foundation; either version 2, or (at your option)
  10  *  any later version.
  11  *
  12  *  libmpeg3 is distributed in the hope that it will be useful,
  13  *  but WITHOUT ANY WARRANTY; without even the implied warranty of
  14  *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  15  *  GNU General Public License for more details.
  16  *
  17  *  You should have received a copy of the GNU General Public License
  18  *  along with GNU Make; see the file COPYING.  If not, write to
  19  *  the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.
  20  *
  21  */
  22
  23
  24 #define MIN(x, y) ((x) > (y) ? (y) : (x))
  25
  26 #include "mpeg3audio.h"
  27 #include <stdio.h>
  28
  29 /* Exponent defines */
  30 #define UNPACK_FBW  1
  31 #define UNPACK_CPL  2
  32 #define UNPACK_LFE  4
  33
  34 static inline int mpeg3audio_ac3_exp_unpack_ch(unsigned int type,
  35                 unsigned int expstr,
  36                 unsigned int ngrps,
  37                 unsigned int initial_exp,
  38                 unsigned short exps[],
  39                 unsigned short *dest)
  40 {
  41         int i, j;
  42         int exp_acc;
  43         int exp_1, exp_2, exp_3;
  44
  45         if(expstr == MPEG3_EXP_REUSE)
  46                 return 0;
  47
  48 /* Handle the initial absolute exponent */
  49         exp_acc = initial_exp;
  50         j = 0;
  51
  52 /* In the case of a fbw channel then the initial absolute value is
  53  * also an exponent */
  54         if(type != UNPACK_CPL)
  55                 dest[j++] = exp_acc;
  56
  57 /* Loop through the groups and fill the dest array appropriately */
  58         for(i = 0; i < ngrps; i++)
  59         {
  60                 if(exps[i] > 124)
  61                 {
  62 //                      fprintf(stderr, "mpeg3audio_ac3_exp_unpack_ch: Invalid exponent %d\n", exps[i]);
  63                         return 1;
  64                 }
  65
  66                 exp_1 = exps[i] / 25;
  67                 exp_2 = (exps[i] % 25) / 5;
  68                 exp_3 = (exps[i] % 25) % 5;
  69
  70                 exp_acc += (exp_1 - 2);
  71
  72                 switch(expstr)
  73                 {
  74                         case MPEG3_EXP_D45:
  75                                 j = MIN(255, j);
  76                                 dest[j++] = exp_acc;
  77                                 j = MIN(255, j);
  78                                 dest[j++] = exp_acc;
  79                         case MPEG3_EXP_D25:
  80                                 j = MIN(255, j);
  81                                 dest[j++] = exp_acc;
  82                         case MPEG3_EXP_D15:
  83                                 j = MIN(255, j);
  84                                 dest[j++] = exp_acc;
  85                 }
  86
  87                 exp_acc += (exp_2 - 2);
  88
  89                 switch(expstr)
  90                 {
  91                         case MPEG3_EXP_D45:
  92                                 j = MIN(255, j);
  93                                 dest[j++] = exp_acc;
  94                                 j = MIN(255, j);
  95                                 dest[j++] = exp_acc;
  96                         case MPEG3_EXP_D25:
  97                                 j = MIN(255, j);
  98                                 dest[j++] = exp_acc;
  99                         case MPEG3_EXP_D15:
 100                                 j = MIN(255, j);
 101                                 dest[j++] = exp_acc;
 102                 }
 103
 104                 exp_acc += (exp_3 - 2);
 105
 106                 switch(expstr)
 107                 {
 108                         case MPEG3_EXP_D45:
 109                                 j = MIN(255, j);
 110                                 dest[j++] = exp_acc;
 111                                 j = MIN(255, j);
 112                                 dest[j++] = exp_acc;
 113                         case MPEG3_EXP_D25:
 114                                 j = MIN(255, j);
 115                                 dest[j++] = exp_acc;
 116                         case MPEG3_EXP_D15:
 117                                 j = MIN(255, j);
 118                                 dest[j++] = exp_acc;
 119                 }
 120         }
 121         return 0;
 122 }
 123
 124 int mpeg3audio_ac3_exponent_unpack(mpeg3audio_t *audio,
 125                 mpeg3_ac3bsi_t *bsi,
 126                 mpeg3_ac3audblk_t *audblk)
 127 {
 128         int i, result = 0;
 129
 130         for(i = 0; i < bsi->nfchans; i++)
 131                 result |= mpeg3audio_ac3_exp_unpack_ch(UNPACK_FBW,
 132                         audblk->chexpstr[i],
 133                         audblk->nchgrps[i],
 134                         audblk->exps[i][0],
 135                         &audblk->exps[i][1],
 136                         audblk->fbw_exp[i]);
 137
 138         if(audblk->cplinu && !result)
 139                 result |= mpeg3audio_ac3_exp_unpack_ch(UNPACK_CPL,
 140                         audblk->cplexpstr,
 141                         audblk->ncplgrps,
 142                         audblk->cplabsexp << 1,
 143                         audblk->cplexps,
 144                         &audblk->cpl_exp[audblk->cplstrtmant]);
 145
 146         if(bsi->lfeon && !result)
 147                 result |= mpeg3audio_ac3_exp_unpack_ch(UNPACK_LFE,
 148                         audblk->lfeexpstr,
 149                         2,
 150                         audblk->lfeexps[0],
 151                         &audblk->lfeexps[1],
 152                         audblk->lfe_exp);
 153         return result;
 154 }