libmpeg3/audio/uncouple.c

   1 /*
   2  *
   3  *      uncouple.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 #include "../bitstream.h"
  24 #include "mpeg3audio.h"
  25
  26 static unsigned char mpeg3_first_bit_lut[256] =
  27 {
  28         0, 8, 7, 7, 6, 6, 6, 6, 5, 5, 5, 5, 5, 5, 5, 5,
  29         4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4,
  30         3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3,
  31         3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3,
  32         2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2,
  33         2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2,
  34         2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2,
  35         2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2,
  36         1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
  37         1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
  38         1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
  39         1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
  40         1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
  41         1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
  42         1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
  43         1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1
  44 };
  45
  46 /* Converts an unsigned exponent in the range of 0-24 and a 16 bit mantissa
  47  * to an IEEE single precision floating point value */
  48 static inline void mpeg3audio_ac3_convert_to_float(unsigned short exp,
  49         unsigned short mantissa,
  50         u_int32_t *dest)
  51 {
  52         int num;
  53         short exponent;
  54         int i;
  55
  56 /* If the mantissa is zero we can simply return zero */
  57         if(mantissa == 0)
  58         {
  59                 *dest = 0;
  60                 return;
  61         }
  62
  63 /* Exponent is offset by 127 in IEEE format minus the shift to
  64  * align the mantissa to 1.f (subtracted in the final result) */
  65         exponent = 127 - exp;
  66
  67 /* Take care of the one asymmetric negative number */
  68         if(mantissa == 0x8000)
  69                 mantissa++;
  70
  71 /* Extract the sign bit, invert the mantissa if it's negative, and
  72    shift out the sign bit */
  73         if(mantissa & 0x8000)
  74         {
  75                 mantissa *= -1;
  76                 num = 0x80000000 + (exponent << 23);
  77         }
  78         else
  79         {
  80                 mantissa *= 1;
  81                 num = exponent << 23;
  82         }
  83
  84 /* Find the index of the most significant one bit */
  85         i = mpeg3_first_bit_lut[mantissa >> 8];
  86
  87         if(i == 0)
  88                 i = mpeg3_first_bit_lut[mantissa & 0xff] + 8;
  89
  90         *dest = num - (i << 23) + (mantissa << (7 + i));
  91         return;
  92 }
  93
  94
  95 int mpeg3audio_ac3_uncouple(mpeg3audio_t *audio,
  96                 mpeg3_ac3bsi_t *bsi,
  97                 mpeg3_ac3audblk_t *audblk,
  98                 mpeg3_stream_coeffs_t *coeffs)
  99 {
 100         int i, j;
 101
 102         for(i = 0; i < bsi->nfchans; i++)
 103         {
 104                 for(j = 0; j < audblk->endmant[i]; j++)
 105                          mpeg3audio_ac3_convert_to_float(audblk->fbw_exp[i][j],
 106                                         audblk->chmant[i][j],
 107                                         (u_int32_t*)&coeffs->fbw[i][j]);
 108         }
 109
 110         if(audblk->cplinu)
 111         {
 112                 for(i = 0; i < bsi->nfchans; i++)
 113                 {
 114                         if(audblk->chincpl[i])
 115                         {
 116                                 mpeg3audio_ac3_uncouple_channel(audio,
 117                                         coeffs,
 118                                         audblk,
 119                                         i);
 120                         }
 121                 }
 122
 123         }
 124
 125         if(bsi->lfeon)
 126         {
 127 /* There are always 7 mantissas for lfe */
 128                 for(j = 0; j < 7 ; j++)
 129                          mpeg3audio_ac3_convert_to_float(audblk->lfe_exp[j],
 130                                         audblk->lfemant[j],
 131                                          (u_int32_t*)&coeffs->lfe[j]);
 132
 133         }
 134         return 0;
 135 }