apps/codecs/libmad/frame.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 # include "bit.h"
  29 # include "stream.h"
  30 # include "frame.h"
  31 # include "timer.h"
  32 # include "layer12.h"
  33 # include "layer3.h"
  34 # include "codeclib.h"
  35
  36 static
  37 unsigned long const bitrate_table[5][15] = {
  38   /* MPEG-1 */
  39   { 0,  32000,  64000,  96000, 128000, 160000, 192000, 224000,  /* Layer I   */
  40        256000, 288000, 320000, 352000, 384000, 416000, 448000 },
  41   { 0,  32000,  48000,  56000,  64000,  80000,  96000, 112000,  /* Layer II  */
  42        128000, 160000, 192000, 224000, 256000, 320000, 384000 },
  43   { 0,  32000,  40000,  48000,  56000,  64000,  80000,  96000,  /* Layer III */
  44        112000, 128000, 160000, 192000, 224000, 256000, 320000 },
  45
  46   /* MPEG-2 LSF */
  47   { 0,  32000,  48000,  56000,  64000,  80000,  96000, 112000,  /* Layer I   */
  48        128000, 144000, 160000, 176000, 192000, 224000, 256000 },
  49   { 0,   8000,  16000,  24000,  32000,  40000,  48000,  56000,  /* Layers    */
  50         64000,  80000,  96000, 112000, 128000, 144000, 160000 } /* II & III  */
  51 };
  52
  53 static
  54 unsigned int const samplerate_table[3] = { 44100, 48000, 32000 };
  55
  56 static
  57 int (*const decoder_table[3])(struct mad_stream *, struct mad_frame *) = {
  58   mad_layer_I,
  59   mad_layer_II,
  60   mad_layer_III
  61 };
  62
  63 /*
  64  * NAME:        header->init()
  65  * DESCRIPTION: initialize header struct
  66  */
  67 void mad_header_init(struct mad_header *header)
  68 {
  69   header->layer          = 0;
  70   header->mode           = 0;
  71   header->mode_extension = 0;
  72   header->emphasis       = 0;
  73
  74   header->bitrate        = 0;
  75   header->samplerate     = 0;
  76
  77   header->crc_check      = 0;
  78   header->crc_target     = 0;
  79
  80   header->flags          = 0;
  81   header->private_bits   = 0;
  82
  83   header->duration       = mad_timer_zero;
  84 }
  85
  86 /*
  87  * NAME:        frame->init()
  88  * DESCRIPTION: initialize frame struct
  89  */
  90 void mad_frame_init(struct mad_frame *frame)
  91 {
  92   mad_header_init(&frame->header);
  93
  94   frame->options = 0;
  95 /* rockbox: comment this to proper zero this array in mad_frame_mute(). overlap
  96  * is linked to an array in rockbox' apps/codecs/mpa.c before calling this.
  97   frame->overlap = 0;
  98 */
  99   mad_frame_mute(frame);
 100 }
 101
 102 /*
 103  * NAME:        frame->finish()
 104  * DESCRIPTION: deallocate any dynamic memory associated with frame
 105  */
 106 /* rockbox: unused
 107 void mad_frame_finish(struct mad_frame *frame)
 108 {
 109   mad_header_finish(&frame->header);
 110
 111   if (frame->overlap) {
 112     free(frame->overlap);
 113     frame->overlap = 0;
 114   }
 115 }
 116 */
 117
 118 /*
 119  * NAME:        decode_header()
 120  * DESCRIPTION: read header data and following CRC word
 121  */
 122 static
 123 int decode_header(struct mad_header *header, struct mad_stream *stream)
 124 {
 125   unsigned int index;
 126
 127   header->flags        = 0;
 128   header->private_bits = 0;
 129
 130   /* header() */
 131
 132   /* syncword */
 133   mad_bit_skip(&stream->ptr, 11);
 134
 135   /* MPEG 2.5 indicator (really part of syncword) */
 136   if (mad_bit_read(&stream->ptr, 1) == 0)
 137     header->flags |= MAD_FLAG_MPEG_2_5_EXT;
 138
 139   /* ID */
 140   if (mad_bit_read(&stream->ptr, 1) == 0)
 141     header->flags |= MAD_FLAG_LSF_EXT;
 142   else if (header->flags & MAD_FLAG_MPEG_2_5_EXT) {
 143     stream->error = MAD_ERROR_LOSTSYNC;
 144     return -1;
 145   }
 146
 147   /* layer */
 148   header->layer = 4 - mad_bit_read(&stream->ptr, 2);
 149
 150   if (header->layer == 4) {
 151     stream->error = MAD_ERROR_BADLAYER;
 152     return -1;
 153   }
 154
 155   /* protection_bit */
 156   if (mad_bit_read(&stream->ptr, 1) == 0) {
 157     header->flags    |= MAD_FLAG_PROTECTION;
 158     header->crc_check = mad_bit_crc(stream->ptr, 16, 0xffff);
 159   }
 160
 161   /* bitrate_index */
 162   index = mad_bit_read(&stream->ptr, 4);
 163
 164   if (index == 15) {
 165     stream->error = MAD_ERROR_BADBITRATE;
 166     return -1;
 167   }
 168
 169   if (header->flags & MAD_FLAG_LSF_EXT)
 170     header->bitrate = bitrate_table[3 + (header->layer >> 1)][index];
 171   else
 172     header->bitrate = bitrate_table[header->layer - 1][index];
 173
 174   /* sampling_frequency */
 175   index = mad_bit_read(&stream->ptr, 2);
 176
 177   if (index == 3) {
 178     stream->error = MAD_ERROR_BADSAMPLERATE;
 179     return -1;
 180   }
 181
 182   header->samplerate = samplerate_table[index];
 183
 184   if (header->flags & MAD_FLAG_LSF_EXT) {
 185     header->samplerate /= 2;
 186
 187     if (header->flags & MAD_FLAG_MPEG_2_5_EXT)
 188       header->samplerate /= 2;
 189   }
 190
 191   /* padding_bit */
 192   if (mad_bit_read(&stream->ptr, 1))
 193     header->flags |= MAD_FLAG_PADDING;
 194
 195   /* private_bit */
 196   if (mad_bit_read(&stream->ptr, 1))
 197     header->private_bits |= MAD_PRIVATE_HEADER;
 198
 199   /* mode */
 200   header->mode = 3 - mad_bit_read(&stream->ptr, 2);
 201
 202   /* mode_extension */
 203   header->mode_extension = mad_bit_read(&stream->ptr, 2);
 204
 205   /* copyright */
 206   if (mad_bit_read(&stream->ptr, 1))
 207     header->flags |= MAD_FLAG_COPYRIGHT;
 208
 209   /* original/copy */
 210   if (mad_bit_read(&stream->ptr, 1))
 211     header->flags |= MAD_FLAG_ORIGINAL;
 212
 213   /* emphasis */
 214   header->emphasis = mad_bit_read(&stream->ptr, 2);
 215
 216 # if defined(OPT_STRICT)
 217   /*
 218    * ISO/IEC 11172-3 says this is a reserved emphasis value, but
 219    * streams exist which use it anyway. Since the value is not important
 220    * to the decoder proper, we allow it unless OPT_STRICT is defined.
 221    */
 222   if (header->emphasis == MAD_EMPHASIS_RESERVED) {
 223     stream->error = MAD_ERROR_BADEMPHASIS;
 224     return -1;
 225   }
 226 # endif
 227
 228   /* error_check() */
 229
 230   /* crc_check */
 231   if (header->flags & MAD_FLAG_PROTECTION)
 232     header->crc_target = mad_bit_read(&stream->ptr, 16);
 233
 234   return 0;
 235 }
 236
 237 /*
 238  * NAME:        free_bitrate()
 239  * DESCRIPTION: attempt to discover the bitstream's free bitrate
 240  */
 241 static
 242 int free_bitrate(struct mad_stream *stream, struct mad_header const *header)
 243 {
 244   struct mad_bitptr keep_ptr;
 245   unsigned long rate = 0;
 246   unsigned int pad_slot, slots_per_frame;
 247   unsigned char const *ptr = 0;
 248
 249   keep_ptr = stream->ptr;
 250
 251   pad_slot = (header->flags & MAD_FLAG_PADDING) ? 1 : 0;
 252   slots_per_frame = (header->layer == MAD_LAYER_III &&
 253                      (header->flags & MAD_FLAG_LSF_EXT)) ? 72 : 144;
 254
 255   while (mad_stream_sync(stream) == 0) {
 256     struct mad_stream peek_stream;
 257     struct mad_header peek_header;
 258
 259     peek_stream = *stream;
 260     peek_header = *header;
 261
 262     if (decode_header(&peek_header, &peek_stream) == 0 &&
 263         peek_header.layer == header->layer &&
 264         peek_header.samplerate == header->samplerate) {
 265       unsigned int N;
 266
 267       ptr = mad_bit_nextbyte(&stream->ptr);
 268
 269       N = ptr - stream->this_frame;
 270
 271       if (header->layer == MAD_LAYER_I) {
 272         rate = (unsigned long) header->samplerate *
 273           (N - 4 * pad_slot + 4) / 48 / 1000;
 274       }
 275       else {
 276         rate = (unsigned long) header->samplerate *
 277           (N - pad_slot + 1) / slots_per_frame / 1000;
 278       }
 279
 280       if (rate >= 8)
 281         break;
 282     }
 283
 284     mad_bit_skip(&stream->ptr, 8);
 285   }
 286
 287   stream->ptr = keep_ptr;
 288
 289   if (rate < 8 || (header->layer == MAD_LAYER_III && rate > 640)) {
 290     stream->error = MAD_ERROR_LOSTSYNC;
 291     return -1;
 292   }
 293
 294   stream->freerate = rate * 1000;
 295
 296   return 0;
 297 }
 298
 299 /*
 300  * NAME:        header->decode()
 301  * DESCRIPTION: read the next frame header from the stream
 302  */
 303 int mad_header_decode(struct mad_header *header, struct mad_stream *stream)
 304 {
 305   register unsigned char const *ptr, *end;
 306   unsigned int pad_slot, N;
 307
 308   ptr = stream->next_frame;
 309   end = stream->bufend;
 310
 311   if (ptr == 0) {
 312     stream->error = MAD_ERROR_BUFPTR;
 313     goto fail;
 314   }
 315
 316   /* stream skip */
 317   if (stream->skiplen) {
 318     if (!stream->sync)
 319       ptr = stream->this_frame;
 320
 321     if (end - ptr < (long) stream->skiplen) {
 322       stream->skiplen   -= end - ptr;
 323       stream->next_frame = end;
 324
 325       stream->error = MAD_ERROR_BUFLEN;
 326       goto fail;
 327     }
 328
 329     ptr += stream->skiplen;
 330     stream->skiplen = 0;
 331
 332     stream->sync = 1;
 333   }
 334
 335  sync:
 336   /* synchronize */
 337   if (stream->sync) {
 338     if (end - ptr < MAD_BUFFER_GUARD) {
 339       stream->next_frame = ptr;
 340
 341       stream->error = MAD_ERROR_BUFLEN;
 342       goto fail;
 343     }
 344     else if (!(ptr[0] == 0xff && (ptr[1] & 0xe0) == 0xe0)) {
 345       /* mark point where frame sync word was expected */
 346       stream->this_frame = ptr;
 347       stream->next_frame = ptr + 1;
 348
 349       stream->error = MAD_ERROR_LOSTSYNC;
 350       goto fail;
 351     }
 352   }
 353   else {
 354     mad_bit_init(&stream->ptr, ptr);
 355
 356     if (mad_stream_sync(stream) == -1) {
 357       if (end - stream->next_frame >= MAD_BUFFER_GUARD)
 358         stream->next_frame = end - MAD_BUFFER_GUARD;
 359
 360       stream->error = MAD_ERROR_BUFLEN;
 361       goto fail;
 362     }
 363
 364     ptr = mad_bit_nextbyte(&stream->ptr);
 365   }
 366
 367   /* begin processing */
 368   stream->this_frame = ptr;
 369   stream->next_frame = ptr + 1;  /* possibly bogus sync word */
 370
 371   mad_bit_init(&stream->ptr, stream->this_frame);
 372
 373   if (decode_header(header, stream) == -1)
 374     goto fail;
 375
 376   /* calculate frame duration */
 377   mad_timer_set(&header->duration, 0,
 378                 32 * MAD_NSBSAMPLES(header), header->samplerate);
 379
 380   /* calculate free bit rate */
 381   if (header->bitrate == 0) {
 382     if ((stream->freerate == 0 || !stream->sync ||
 383          (header->layer == MAD_LAYER_III && stream->freerate > 640000)) &&
 384         free_bitrate(stream, header) == -1)
 385       goto fail;
 386
 387     header->bitrate = stream->freerate;
 388     header->flags  |= MAD_FLAG_FREEFORMAT;
 389   }
 390
 391   /* calculate beginning of next frame */
 392   pad_slot = (header->flags & MAD_FLAG_PADDING) ? 1 : 0;
 393
 394   if (header->layer == MAD_LAYER_I)
 395     N = ((12 * header->bitrate / header->samplerate) + pad_slot) * 4;
 396   else {
 397     unsigned int slots_per_frame;
 398
 399     slots_per_frame = (header->layer == MAD_LAYER_III &&
 400                        (header->flags & MAD_FLAG_LSF_EXT)) ? 72 : 144;
 401
 402     N = (slots_per_frame * header->bitrate / header->samplerate) + pad_slot;
 403   }
 404
 405   /* verify there is enough data left in buffer to decode this frame */
 406   if ((long)(N + MAD_BUFFER_GUARD) > end - stream->this_frame) {
 407     stream->next_frame = stream->this_frame;
 408
 409     stream->error = MAD_ERROR_BUFLEN;
 410     goto fail;
 411   }
 412
 413   stream->next_frame = stream->this_frame + N;
 414
 415   if (!stream->sync) {
 416     /* check that a valid frame header follows this frame */
 417
 418     ptr = stream->next_frame;
 419     if (!(ptr[0] == 0xff && (ptr[1] & 0xe0) == 0xe0)) {
 420       ptr = stream->next_frame = stream->this_frame + 1;
 421       goto sync;
 422     }
 423
 424     stream->sync = 1;
 425   }
 426
 427   header->flags |= MAD_FLAG_INCOMPLETE;
 428
 429   return 0;
 430
 431  fail:
 432   stream->sync = 0;
 433
 434   return -1;
 435 }
 436
 437 /*
 438  * NAME:        frame->decode()
 439  * DESCRIPTION: decode a single frame from a bitstream
 440  */
 441 int mad_frame_decode(struct mad_frame *frame, struct mad_stream *stream)
 442 {
 443   frame->options = stream->options;
 444
 445   /* header() */
 446   /* error_check() */
 447
 448   if (!(frame->header.flags & MAD_FLAG_INCOMPLETE) &&
 449       mad_header_decode(&frame->header, stream) == -1)
 450     goto fail;
 451
 452   /* audio_data() */
 453
 454   frame->header.flags &= ~MAD_FLAG_INCOMPLETE;
 455
 456   if (decoder_table[frame->header.layer - 1](stream, frame) == -1) {
 457     if (!MAD_RECOVERABLE(stream->error))
 458       stream->next_frame = stream->this_frame;
 459
 460     goto fail;
 461   }
 462
 463   /* ancillary_data() */
 464
 465   if (frame->header.layer != MAD_LAYER_III) {
 466     struct mad_bitptr next_frame;
 467
 468     mad_bit_init(&next_frame, stream->next_frame);
 469
 470     stream->anc_ptr    = stream->ptr;
 471     stream->anc_bitlen = mad_bit_length(&stream->ptr, &next_frame);
 472
 473     mad_bit_finish(&next_frame);
 474   }
 475
 476
 477
 478   return 0;
 479
 480  fail:
 481   stream->anc_bitlen = 0;
 482   return -1;
 483 }
 484
 485 /*
 486  * NAME:        frame->mute()
 487  * DESCRIPTION: zero all subband values so the frame becomes silent
 488  */
 489 void mad_frame_mute(struct mad_frame *frame)
 490 {
 491   memset((*frame->sbsample_prev), 0, sizeof(*frame->sbsample_prev));
 492   memset((*frame->sbsample)     , 0, sizeof(*frame->sbsample));
 493   memset((*frame->overlap)      , 0, sizeof(*frame->overlap));
 494 }