libs/mpega/layer12.c

   1 /*
   2  * libmad - MPEG audio decoder library
   3  * Copyright (C) 2000-2004 Underbit Technologies, Inc.
   4  *
   5  * This program is free software; you can redistribute it and/or modify
   6  * it under the terms of the GNU General Public License as published by
   7  * the Free Software Foundation; either version 2 of the License, or
   8  * (at your option) any later version.
   9  *
  10  * This program is distributed in the hope that it will be useful,
  11  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  12  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  13  * GNU General Public License for more details.
  14  *
  15  * You should have received a copy of the GNU General Public License
  16  * along with this program; if not, write to the Free Software
  17  * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
  18  *
  19  * $Id$
  20  */
  21
  22 # ifdef HAVE_CONFIG_H
  23 #  include "config.h"
  24 # endif
  25
  26 # include "global.h"
  27
  28 # ifdef HAVE_LIMITS_H
  29 #  include <limits.h>
  30 # else
  31 #  define CHAR_BIT  8
  32 # endif
  33
  34 # include "fixed.h"
  35 # include "bit.h"
  36 # include "stream.h"
  37 # include "frame.h"
  38 # include "layer12.h"
  39
  40 /*
  41  * scalefactor table
  42  * used in both Layer I and Layer II decoding
  43  */
  44 static
  45 mad_fixed_t const sf_table[64] = {
  46 # include "sf_table.dat"
  47 };
  48
  49 /* --- Layer I ------------------------------------------------------------- */
  50
  51 /* linear scaling table */
  52 static
  53 mad_fixed_t const linear_table[14] = {
  54   MAD_F(0x15555555),  /* 2^2  / (2^2  - 1) == 1.33333333333333 */
  55   MAD_F(0x12492492),  /* 2^3  / (2^3  - 1) == 1.14285714285714 */
  56   MAD_F(0x11111111),  /* 2^4  / (2^4  - 1) == 1.06666666666667 */
  57   MAD_F(0x10842108),  /* 2^5  / (2^5  - 1) == 1.03225806451613 */
  58   MAD_F(0x10410410),  /* 2^6  / (2^6  - 1) == 1.01587301587302 */
  59   MAD_F(0x10204081),  /* 2^7  / (2^7  - 1) == 1.00787401574803 */
  60   MAD_F(0x10101010),  /* 2^8  / (2^8  - 1) == 1.00392156862745 */
  61   MAD_F(0x10080402),  /* 2^9  / (2^9  - 1) == 1.00195694716243 */
  62   MAD_F(0x10040100),  /* 2^10 / (2^10 - 1) == 1.00097751710655 */
  63   MAD_F(0x10020040),  /* 2^11 / (2^11 - 1) == 1.00048851978505 */
  64   MAD_F(0x10010010),  /* 2^12 / (2^12 - 1) == 1.00024420024420 */
  65   MAD_F(0x10008004),  /* 2^13 / (2^13 - 1) == 1.00012208521548 */
  66   MAD_F(0x10004001),  /* 2^14 / (2^14 - 1) == 1.00006103888177 */
  67   MAD_F(0x10002000)   /* 2^15 / (2^15 - 1) == 1.00003051850948 */
  68 };
  69
  70 /*
  71  * NAME:        I_sample()
  72  * DESCRIPTION: decode one requantized Layer I sample from a bitstream
  73  */
  74 static
  75 mad_fixed_t I_sample(struct mad_bitptr *ptr, unsigned int nb)
  76 {
  77   mad_fixed_t sample;
  78
  79   sample = mad_bit_read(ptr, nb);
  80
  81   /* invert most significant bit, extend sign, then scale to fixed format */
  82
  83   sample ^= 1 << (nb - 1);
  84   sample |= -(sample & (1 << (nb - 1)));
  85
  86   sample <<= MAD_F_FRACBITS - (nb - 1);
  87
  88   /* requantize the sample */
  89
  90   /* s'' = (2^nb / (2^nb - 1)) * (s''' + 2^(-nb + 1)) */
  91
  92   sample += MAD_F_ONE >> (nb - 1);
  93
  94   return mad_f_mul(sample, linear_table[nb - 2]);
  95
  96   /* s' = factor * s'' */
  97   /* (to be performed by caller) */
  98 }
  99
 100 /*
 101  * NAME:        layer->I()
 102  * DESCRIPTION: decode a single Layer I frame
 103  */
 104 int mad_layer_I(struct mad_stream *stream, struct mad_frame *frame)
 105 {
 106   struct mad_header *header = &frame->header;
 107   unsigned int nch, bound, ch, s, sb, nb;
 108   unsigned char allocation[2][32], scalefactor[2][32];
 109
 110   nch = MAD_NCHANNELS(header);
 111
 112   bound = 32;
 113   if (header->mode == MAD_MODE_JOINT_STEREO) {
 114     header->flags |= MAD_FLAG_I_STEREO;
 115     bound = 4 + header->mode_extension * 4;
 116   }
 117
 118   /* check CRC word */
 119
 120   if (header->flags & MAD_FLAG_PROTECTION) {
 121     header->crc_check =
 122       mad_bit_crc(stream->ptr, 4 * (bound * nch + (32 - bound)),
 123                   header->crc_check);
 124
 125     if (header->crc_check != header->crc_target &&
 126         !(frame->options & MAD_OPTION_IGNORECRC)) {
 127       stream->error = MAD_ERROR_BADCRC;
 128       return -1;
 129     }
 130   }
 131
 132   /* decode bit allocations */
 133
 134   for (sb = 0; sb < bound; ++sb) {
 135     for (ch = 0; ch < nch; ++ch) {
 136       nb = mad_bit_read(&stream->ptr, 4);
 137
 138       if (nb == 15) {
 139         stream->error = MAD_ERROR_BADBITALLOC;
 140         return -1;
 141       }
 142
 143       allocation[ch][sb] = nb ? nb + 1 : 0;
 144     }
 145   }
 146
 147   for (sb = bound; sb < 32; ++sb) {
 148     nb = mad_bit_read(&stream->ptr, 4);
 149
 150     if (nb == 15) {
 151       stream->error = MAD_ERROR_BADBITALLOC;
 152       return -1;
 153     }
 154
 155     allocation[0][sb] =
 156     allocation[1][sb] = nb ? nb + 1 : 0;
 157   }
 158
 159   /* decode scalefactors */
 160
 161   for (sb = 0; sb < 32; ++sb) {
 162     for (ch = 0; ch < nch; ++ch) {
 163       if (allocation[ch][sb]) {
 164         scalefactor[ch][sb] = mad_bit_read(&stream->ptr, 6);
 165
 166 # if defined(OPT_STRICT)
 167         /*
 168          * Scalefactor index 63 does not appear in Table B.1 of
 169          * ISO/IEC 11172-3. Nonetheless, other implementations accept it,
 170          * so we only reject it if OPT_STRICT is defined.
 171          */
 172         if (scalefactor[ch][sb] == 63) {
 173           stream->error = MAD_ERROR_BADSCALEFACTOR;
 174           return -1;
 175         }
 176 # endif
 177       }
 178     }
 179   }
 180
 181   /* decode samples */
 182
 183   for (s = 0; s < 12; ++s) {
 184     for (sb = 0; sb < bound; ++sb) {
 185       for (ch = 0; ch < nch; ++ch) {
 186         nb = allocation[ch][sb];
 187         frame->sbsample[ch][s][sb] = nb ?
 188           mad_f_mul(I_sample(&stream->ptr, nb),
 189                     sf_table[scalefactor[ch][sb]]) : 0;
 190       }
 191     }
 192
 193     for (sb = bound; sb < 32; ++sb) {
 194       if ((nb = allocation[0][sb])) {
 195         mad_fixed_t sample;
 196
 197         sample = I_sample(&stream->ptr, nb);
 198
 199         for (ch = 0; ch < nch; ++ch) {
 200           frame->sbsample[ch][s][sb] =
 201             mad_f_mul(sample, sf_table[scalefactor[ch][sb]]);
 202         }
 203       }
 204       else {
 205         for (ch = 0; ch < nch; ++ch)
 206           frame->sbsample[ch][s][sb] = 0;
 207       }
 208     }
 209   }
 210
 211   return 0;
 212 }
 213
 214 /* --- Layer II ------------------------------------------------------------ */
 215
 216 /* possible quantization per subband table */
 217 static
 218 struct {
 219   unsigned int sblimit;
 220   unsigned char const offsets[30];
 221 } const sbquant_table[5] = {
 222   /* ISO/IEC 11172-3 Table B.2a */
 223   { 27, { 7, 7, 7, 6, 6, 6, 6, 6, 6, 6, 6, 3, 3, 3, 3, 3,       /* 0 */
 224           3, 3, 3, 3, 3, 3, 3, 0, 0, 0, 0 } },
 225   /* ISO/IEC 11172-3 Table B.2b */
 226   { 30, { 7, 7, 7, 6, 6, 6, 6, 6, 6, 6, 6, 3, 3, 3, 3, 3,       /* 1 */
 227           3, 3, 3, 3, 3, 3, 3, 0, 0, 0, 0, 0, 0, 0 } },
 228   /* ISO/IEC 11172-3 Table B.2c */
 229   {  8, { 5, 5, 2, 2, 2, 2, 2, 2 } },                           /* 2 */
 230   /* ISO/IEC 11172-3 Table B.2d */
 231   { 12, { 5, 5, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2 } },               /* 3 */
 232   /* ISO/IEC 13818-3 Table B.1 */
 233   { 30, { 4, 4, 4, 4, 2, 2, 2, 2, 2, 2, 2, 1, 1, 1, 1, 1,       /* 4 */
 234           1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1 } }
 235 };
 236
 237 /* bit allocation table */
 238 static
 239 struct {
 240   unsigned short nbal;
 241   unsigned short offset;
 242 } const bitalloc_table[8] = {
 243   { 2, 0 },  /* 0 */
 244   { 2, 3 },  /* 1 */
 245   { 3, 3 },  /* 2 */
 246   { 3, 1 },  /* 3 */
 247   { 4, 2 },  /* 4 */
 248   { 4, 3 },  /* 5 */
 249   { 4, 4 },  /* 6 */
 250   { 4, 5 }   /* 7 */
 251 };
 252
 253 /* offsets into quantization class table */
 254 static
 255 unsigned char const offset_table[6][15] = {
 256   { 0, 1, 16                                             },  /* 0 */
 257   { 0, 1,  2, 3, 4, 5, 16                                },  /* 1 */
 258   { 0, 1,  2, 3, 4, 5,  6, 7,  8,  9, 10, 11, 12, 13, 14 },  /* 2 */
 259   { 0, 1,  3, 4, 5, 6,  7, 8,  9, 10, 11, 12, 13, 14, 15 },  /* 3 */
 260   { 0, 1,  2, 3, 4, 5,  6, 7,  8,  9, 10, 11, 12, 13, 16 },  /* 4 */
 261   { 0, 2,  4, 5, 6, 7,  8, 9, 10, 11, 12, 13, 14, 15, 16 }   /* 5 */
 262 };
 263
 264 /* quantization class table */
 265 static
 266 struct quantclass {
 267   unsigned short nlevels;
 268   unsigned char group;
 269   unsigned char bits;
 270   mad_fixed_t C;
 271   mad_fixed_t D;
 272 } const qc_table[17] = {
 273 # include "qc_table.dat"
 274 };
 275
 276 /*
 277  * NAME:        II_samples()
 278  * DESCRIPTION: decode three requantized Layer II samples from a bitstream
 279  */
 280 static
 281 void II_samples(struct mad_bitptr *ptr,
 282                 struct quantclass const *quantclass,
 283                 mad_fixed_t output[3])
 284 {
 285   unsigned int nb, s, sample[3];
 286
 287   if ((nb = quantclass->group)) {
 288     unsigned int c, nlevels;
 289
 290     /* degrouping */
 291     c = mad_bit_read(ptr, quantclass->bits);
 292     nlevels = quantclass->nlevels;
 293
 294     for (s = 0; s < 3; ++s) {
 295       sample[s] = c % nlevels;
 296       c /= nlevels;
 297     }
 298   }
 299   else {
 300     nb = quantclass->bits;
 301
 302     for (s = 0; s < 3; ++s)
 303       sample[s] = mad_bit_read(ptr, nb);
 304   }
 305
 306   for (s = 0; s < 3; ++s) {
 307     mad_fixed_t requantized;
 308
 309     /* invert most significant bit, extend sign, then scale to fixed format */
 310
 311     requantized  = sample[s] ^ (1 << (nb - 1));
 312     requantized |= -(requantized & (1 << (nb - 1)));
 313
 314     requantized <<= MAD_F_FRACBITS - (nb - 1);
 315
 316     /* requantize the sample */
 317
 318     /* s'' = C * (s''' + D) */
 319
 320     output[s] = mad_f_mul(requantized + quantclass->D, quantclass->C);
 321
 322     /* s' = factor * s'' */
 323     /* (to be performed by caller) */
 324   }
 325 }
 326
 327 /*
 328  * NAME:        layer->II()
 329  * DESCRIPTION: decode a single Layer II frame
 330  */
 331 int mad_layer_II(struct mad_stream *stream, struct mad_frame *frame)
 332 {
 333   struct mad_header *header = &frame->header;
 334   struct mad_bitptr start;
 335   unsigned int index, sblimit, nbal, nch, bound, gr, ch, s, sb;
 336   unsigned char const *offsets;
 337   unsigned char allocation[2][32], scfsi[2][32], scalefactor[2][32][3];
 338   mad_fixed_t samples[3];
 339
 340   nch = MAD_NCHANNELS(header);
 341
 342   if (header->flags & MAD_FLAG_LSF_EXT)
 343     index = 4;
 344   else if (header->flags & MAD_FLAG_FREEFORMAT)
 345     goto freeformat;
 346   else {
 347     unsigned long bitrate_per_channel;
 348
 349     bitrate_per_channel = header->bitrate;
 350     if (nch == 2) {
 351       bitrate_per_channel /= 2;
 352
 353 # if defined(OPT_STRICT)
 354       /*
 355        * ISO/IEC 11172-3 allows only single channel mode for 32, 48, 56, and
 356        * 80 kbps bitrates in Layer II, but some encoders ignore this
 357        * restriction. We enforce it if OPT_STRICT is defined.
 358        */
 359       if (bitrate_per_channel <= 28000 || bitrate_per_channel == 40000) {
 360         stream->error = MAD_ERROR_BADMODE;
 361         return -1;
 362       }
 363 # endif
 364     }
 365     else {  /* nch == 1 */
 366       if (bitrate_per_channel > 192000) {
 367         /*
 368          * ISO/IEC 11172-3 does not allow single channel mode for 224, 256,
 369          * 320, or 384 kbps bitrates in Layer II.
 370          */
 371         stream->error = MAD_ERROR_BADMODE;
 372         return -1;
 373       }
 374     }
 375
 376     if (bitrate_per_channel <= 48000)
 377       index = (header->samplerate == 32000) ? 3 : 2;
 378     else if (bitrate_per_channel <= 80000)
 379       index = 0;
 380     else {
 381     freeformat:
 382       index = (header->samplerate == 48000) ? 0 : 1;
 383     }
 384   }
 385
 386   sblimit = sbquant_table[index].sblimit;
 387   offsets = sbquant_table[index].offsets;
 388
 389   bound = 32;
 390   if (header->mode == MAD_MODE_JOINT_STEREO) {
 391     header->flags |= MAD_FLAG_I_STEREO;
 392     bound = 4 + header->mode_extension * 4;
 393   }
 394
 395   if (bound > sblimit)
 396     bound = sblimit;
 397
 398   start = stream->ptr;
 399
 400   /* decode bit allocations */
 401
 402   for (sb = 0; sb < bound; ++sb) {
 403     nbal = bitalloc_table[offsets[sb]].nbal;
 404
 405     for (ch = 0; ch < nch; ++ch)
 406       allocation[ch][sb] = mad_bit_read(&stream->ptr, nbal);
 407   }
 408
 409   for (sb = bound; sb < sblimit; ++sb) {
 410     nbal = bitalloc_table[offsets[sb]].nbal;
 411
 412     allocation[0][sb] =
 413     allocation[1][sb] = mad_bit_read(&stream->ptr, nbal);
 414   }
 415
 416   /* decode scalefactor selection info */
 417
 418   for (sb = 0; sb < sblimit; ++sb) {
 419     for (ch = 0; ch < nch; ++ch) {
 420       if (allocation[ch][sb])
 421         scfsi[ch][sb] = mad_bit_read(&stream->ptr, 2);
 422     }
 423   }
 424
 425   /* check CRC word */
 426
 427   if (header->flags & MAD_FLAG_PROTECTION) {
 428     header->crc_check =
 429       mad_bit_crc(start, mad_bit_length(&start, &stream->ptr),
 430                   header->crc_check);
 431
 432     if (header->crc_check != header->crc_target &&
 433         !(frame->options & MAD_OPTION_IGNORECRC)) {
 434       stream->error = MAD_ERROR_BADCRC;
 435       return -1;
 436     }
 437   }
 438
 439   /* decode scalefactors */
 440
 441   for (sb = 0; sb < sblimit; ++sb) {
 442     for (ch = 0; ch < nch; ++ch) {
 443       if (allocation[ch][sb]) {
 444         scalefactor[ch][sb][0] = mad_bit_read(&stream->ptr, 6);
 445
 446         switch (scfsi[ch][sb]) {
 447         case 2:
 448           scalefactor[ch][sb][2] =
 449           scalefactor[ch][sb][1] =
 450           scalefactor[ch][sb][0];
 451           break;
 452
 453         case 0:
 454           scalefactor[ch][sb][1] = mad_bit_read(&stream->ptr, 6);
 455           /* fall through */
 456
 457         case 1:
 458         case 3:
 459           scalefactor[ch][sb][2] = mad_bit_read(&stream->ptr, 6);
 460         }
 461
 462         if (scfsi[ch][sb] & 1)
 463           scalefactor[ch][sb][1] = scalefactor[ch][sb][scfsi[ch][sb] - 1];
 464
 465 # if defined(OPT_STRICT)
 466         /*
 467          * Scalefactor index 63 does not appear in Table B.1 of
 468          * ISO/IEC 11172-3. Nonetheless, other implementations accept it,
 469          * so we only reject it if OPT_STRICT is defined.
 470          */
 471         if (scalefactor[ch][sb][0] == 63 ||
 472             scalefactor[ch][sb][1] == 63 ||
 473             scalefactor[ch][sb][2] == 63) {
 474           stream->error = MAD_ERROR_BADSCALEFACTOR;
 475           return -1;
 476         }
 477 # endif
 478       }
 479     }
 480   }
 481
 482   /* decode samples */
 483
 484   for (gr = 0; gr < 12; ++gr) {
 485     for (sb = 0; sb < bound; ++sb) {
 486       for (ch = 0; ch < nch; ++ch) {
 487         if ((index = allocation[ch][sb])) {
 488           index = offset_table[bitalloc_table[offsets[sb]].offset][index - 1];
 489
 490           II_samples(&stream->ptr, &qc_table[index], samples);
 491
 492           for (s = 0; s < 3; ++s) {
 493             frame->sbsample[ch][3 * gr + s][sb] =
 494               mad_f_mul(samples[s], sf_table[scalefactor[ch][sb][gr / 4]]);
 495           }
 496         }
 497         else {
 498           for (s = 0; s < 3; ++s)
 499             frame->sbsample[ch][3 * gr + s][sb] = 0;
 500         }
 501       }
 502     }
 503
 504     for (sb = bound; sb < sblimit; ++sb) {
 505       if ((index = allocation[0][sb])) {
 506         index = offset_table[bitalloc_table[offsets[sb]].offset][index - 1];
 507
 508         II_samples(&stream->ptr, &qc_table[index], samples);
 509
 510         for (ch = 0; ch < nch; ++ch) {
 511           for (s = 0; s < 3; ++s) {
 512             frame->sbsample[ch][3 * gr + s][sb] =
 513               mad_f_mul(samples[s], sf_table[scalefactor[ch][sb][gr / 4]]);
 514           }
 515         }
 516       }
 517       else {
 518         for (ch = 0; ch < nch; ++ch) {
 519           for (s = 0; s < 3; ++s)
 520             frame->sbsample[ch][3 * gr + s][sb] = 0;
 521         }
 522       }
 523     }
 524
 525     for (ch = 0; ch < nch; ++ch) {
 526       for (s = 0; s < 3; ++s) {
 527         for (sb = sblimit; sb < 32; ++sb)
 528           frame->sbsample[ch][3 * gr + s][sb] = 0;
 529       }
 530     }
 531   }
 532
 533   return 0;
 534 }