libavcodec/alac.c

   1 /*
   2  * ALAC (Apple Lossless Audio Codec) decoder
   3  * Copyright (c) 2005 David Hammerton
   4  *
   5  * This file is part of FFmpeg.
   6  *
   7  * FFmpeg is free software; you can redistribute it and/or
   8  * modify it under the terms of the GNU Lesser General Public
   9  * License as published by the Free Software Foundation; either
  10  * version 2.1 of the License, or (at your option) any later version.
  11  *
  12  * FFmpeg 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 GNU
  15  * Lesser General Public License for more details.
  16  *
  17  * You should have received a copy of the GNU Lesser General Public
  18  * License along with FFmpeg; if not, write to the Free Software
  19  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  20  */
  21
  22 /**
  23  * @file alac.c
  24  * ALAC (Apple Lossless Audio Codec) decoder
  25  * @author 2005 David Hammerton
  26  *
  27  * For more information on the ALAC format, visit:
  28  *  http://crazney.net/programs/itunes/alac.html
  29  *
  30  * Note: This decoder expects a 36- (0x24-)byte QuickTime atom to be
  31  * passed through the extradata[_size] fields. This atom is tacked onto
  32  * the end of an 'alac' stsd atom and has the following format:
  33  *  bytes 0-3   atom size (0x24), big-endian
  34  *  bytes 4-7   atom type ('alac', not the 'alac' tag from start of stsd)
  35  *  bytes 8-35  data bytes needed by decoder
  36  *
  37  * Extradata:
  38  * 32bit  size
  39  * 32bit  tag (=alac)
  40  * 32bit  zero?
  41  * 32bit  max sample per frame
  42  *  8bit  ?? (zero?)
  43  *  8bit  sample size
  44  *  8bit  history mult
  45  *  8bit  initial history
  46  *  8bit  kmodifier
  47  *  8bit  channels?
  48  * 16bit  ??
  49  * 32bit  max coded frame size
  50  * 32bit  bitrate?
  51  * 32bit  samplerate
  52  */
  53
  54
  55 #include "avcodec.h"
  56 #include "bitstream.h"
  57 #include "bytestream.h"
  58
  59 #define ALAC_EXTRADATA_SIZE 36
  60 #define MAX_CHANNELS 2
  61
  62 typedef struct {
  63
  64     AVCodecContext *avctx;
  65     GetBitContext gb;
  66     /* init to 0; first frame decode should initialize from extradata and
  67      * set this to 1 */
  68     int context_initialized;
  69
  70     int samplesize;
  71     int numchannels;
  72     int bytespersample;
  73
  74     /* buffers */
  75     int32_t *predicterror_buffer[MAX_CHANNELS];
  76
  77     int32_t *outputsamples_buffer[MAX_CHANNELS];
  78
  79     /* stuff from setinfo */
  80     uint32_t setinfo_max_samples_per_frame; /* 0x1000 = 4096 */    /* max samples per frame? */
  81     uint8_t setinfo_7a; /* 0x00 */
  82     uint8_t setinfo_sample_size; /* 0x10 */
  83     uint8_t setinfo_rice_historymult; /* 0x28 */
  84     uint8_t setinfo_rice_initialhistory; /* 0x0a */
  85     uint8_t setinfo_rice_kmodifier; /* 0x0e */
  86     uint8_t setinfo_7f; /* 0x02 */
  87     uint16_t setinfo_80; /* 0x00ff */
  88     uint32_t setinfo_82; /* 0x000020e7 */ /* max sample size?? */
  89     uint32_t setinfo_86; /* 0x00069fe4 */ /* bit rate (average)?? */
  90     uint32_t setinfo_8a_rate; /* 0x0000ac44 */
  91     /* end setinfo stuff */
  92
  93 } ALACContext;
  94
  95 static void allocate_buffers(ALACContext *alac)
  96 {
  97     int chan;
  98     for (chan = 0; chan < MAX_CHANNELS; chan++) {
  99         alac->predicterror_buffer[chan] =
 100             av_malloc(alac->setinfo_max_samples_per_frame * 4);
 101
 102         alac->outputsamples_buffer[chan] =
 103             av_malloc(alac->setinfo_max_samples_per_frame * 4);
 104     }
 105 }
 106
 107 static int alac_set_info(ALACContext *alac)
 108 {
 109     unsigned char *ptr = alac->avctx->extradata;
 110
 111     ptr += 4; /* size */
 112     ptr += 4; /* alac */
 113     ptr += 4; /* 0 ? */
 114
 115     if(AV_RB32(ptr) >= UINT_MAX/4){
 116         av_log(alac->avctx, AV_LOG_ERROR, "setinfo_max_samples_per_frame too large\n");
 117         return -1;
 118     }
 119
 120     /* buffer size / 2 ? */
 121     alac->setinfo_max_samples_per_frame = bytestream_get_be32(&ptr);
 122     alac->setinfo_7a                    = *ptr++;
 123     alac->setinfo_sample_size           = *ptr++;
 124     alac->setinfo_rice_historymult      = *ptr++;
 125     alac->setinfo_rice_initialhistory   = *ptr++;
 126     alac->setinfo_rice_kmodifier        = *ptr++;
 127     /* channels? */
 128     alac->setinfo_7f                    = *ptr++;
 129     alac->setinfo_80                    = bytestream_get_be16(&ptr);
 130     /* max coded frame size */
 131     alac->setinfo_82                    = bytestream_get_be32(&ptr);
 132     /* bitrate ? */
 133     alac->setinfo_86                    = bytestream_get_be32(&ptr);
 134     /* samplerate */
 135     alac->setinfo_8a_rate               = bytestream_get_be32(&ptr);
 136
 137     allocate_buffers(alac);
 138
 139     return 0;
 140 }
 141
 142 static inline int count_leading_zeros(int32_t input)
 143 {
 144     return 31-av_log2(input);
 145 }
 146
 147 static void bastardized_rice_decompress(ALACContext *alac,
 148                                  int32_t *output_buffer,
 149                                  int output_size,
 150                                  int readsamplesize, /* arg_10 */
 151                                  int rice_initialhistory, /* arg424->b */
 152                                  int rice_kmodifier, /* arg424->d */
 153                                  int rice_historymult, /* arg424->c */
 154                                  int rice_kmodifier_mask /* arg424->e */
 155         )
 156 {
 157     int output_count;
 158     unsigned int history = rice_initialhistory;
 159     int sign_modifier = 0;
 160
 161     for (output_count = 0; output_count < output_size; output_count++) {
 162         int32_t x = 0;
 163         int32_t x_modified;
 164         int32_t final_val;
 165
 166         /* read x - number of 1s before 0 represent the rice */
 167         while (x <= 8 && get_bits1(&alac->gb)) {
 168             x++;
 169         }
 170
 171
 172         if (x > 8) { /* RICE THRESHOLD */
 173             /* use alternative encoding */
 174             int32_t value;
 175
 176             value = get_bits(&alac->gb, readsamplesize);
 177
 178             /* mask value to readsamplesize size */
 179             if (readsamplesize != 32)
 180                 value &= (0xffffffff >> (32 - readsamplesize));
 181
 182             x = value;
 183         } else {
 184             /* standard rice encoding */
 185             int extrabits;
 186             int k; /* size of extra bits */
 187
 188             /* read k, that is bits as is */
 189             k = 31 - rice_kmodifier - count_leading_zeros((history >> 9) + 3);
 190
 191             if (k < 0)
 192                 k += rice_kmodifier;
 193             else
 194                 k = rice_kmodifier;
 195
 196             if (k != 1) {
 197                 extrabits = show_bits(&alac->gb, k);
 198
 199                 /* multiply x by 2^k - 1, as part of their strange algorithm */
 200                 x = (x << k) - x;
 201
 202                 if (extrabits > 1) {
 203                     x += extrabits - 1;
 204                     get_bits(&alac->gb, k);
 205                 } else
 206                     get_bits(&alac->gb, k - 1);
 207             }
 208         }
 209
 210         x_modified = sign_modifier + x;
 211         final_val = (x_modified + 1) / 2;
 212         if (x_modified & 1) final_val *= -1;
 213
 214         output_buffer[output_count] = final_val;
 215
 216         sign_modifier = 0;
 217
 218         /* now update the history */
 219         history += x_modified * rice_historymult
 220                    - ((history * rice_historymult) >> 9);
 221
 222         if (x_modified > 0xffff)
 223             history = 0xffff;
 224
 225         /* special case: there may be compressed blocks of 0 */
 226         if ((history < 128) && (output_count+1 < output_size)) {
 227             int block_size;
 228
 229             sign_modifier = 1;
 230
 231             x = 0;
 232             while (x <= 8 && get_bits1(&alac->gb)) {
 233                 x++;
 234             }
 235
 236             if (x > 8) {
 237                 block_size = get_bits(&alac->gb, 16);
 238                 block_size &= 0xffff;
 239             } else {
 240                 int k;
 241                 int extrabits;
 242
 243                 k = count_leading_zeros(history) + ((history + 16) >> 6 /* / 64 */) - 24;
 244
 245                 extrabits = show_bits(&alac->gb, k);
 246
 247                 block_size = (((1 << k) - 1) & rice_kmodifier_mask) * x
 248                            + extrabits - 1;
 249
 250                 if (extrabits < 2) {
 251                     x = 1 - extrabits;
 252                     block_size += x;
 253                     get_bits(&alac->gb, k - 1);
 254                 } else {
 255                     get_bits(&alac->gb, k);
 256                 }
 257             }
 258
 259             if (block_size > 0) {
 260                 memset(&output_buffer[output_count+1], 0, block_size * 4);
 261                 output_count += block_size;
 262             }
 263
 264             if (block_size > 0xffff)
 265                 sign_modifier = 0;
 266
 267             history = 0;
 268         }
 269     }
 270 }
 271
 272 #define SIGN_EXTENDED32(val, bits) ((val << (32 - bits)) >> (32 - bits))
 273
 274 #define SIGN_ONLY(v) \
 275                      ((v < 0) ? (-1) : \
 276                                 ((v > 0) ? (1) : \
 277                                            (0)))
 278
 279 static void predictor_decompress_fir_adapt(int32_t *error_buffer,
 280                                            int32_t *buffer_out,
 281                                            int output_size,
 282                                            int readsamplesize,
 283                                            int16_t *predictor_coef_table,
 284                                            int predictor_coef_num,
 285                                            int predictor_quantitization)
 286 {
 287     int i;
 288
 289     /* first sample always copies */
 290     *buffer_out = *error_buffer;
 291
 292     if (!predictor_coef_num) {
 293         if (output_size <= 1)
 294             return;
 295
 296         memcpy(buffer_out+1, error_buffer+1, (output_size-1) * 4);
 297         return;
 298     }
 299
 300     if (predictor_coef_num == 0x1f) { /* 11111 - max value of predictor_coef_num */
 301       /* second-best case scenario for fir decompression,
 302        * error describes a small difference from the previous sample only
 303        */
 304         if (output_size <= 1)
 305             return;
 306         for (i = 0; i < output_size - 1; i++) {
 307             int32_t prev_value;
 308             int32_t error_value;
 309
 310             prev_value = buffer_out[i];
 311             error_value = error_buffer[i+1];
 312             buffer_out[i+1] =
 313                 SIGN_EXTENDED32((prev_value + error_value), readsamplesize);
 314         }
 315         return;
 316     }
 317
 318     /* read warm-up samples */
 319     if (predictor_coef_num > 0)
 320         for (i = 0; i < predictor_coef_num; i++) {
 321             int32_t val;
 322
 323             val = buffer_out[i] + error_buffer[i+1];
 324             val = SIGN_EXTENDED32(val, readsamplesize);
 325             buffer_out[i+1] = val;
 326         }
 327
 328 #if 0
 329     /* 4 and 8 are very common cases (the only ones i've seen). these
 330      * should be unrolled and optimised
 331      */
 332     if (predictor_coef_num == 4) {
 333         /* FIXME: optimised general case */
 334         return;
 335     }
 336
 337     if (predictor_coef_table == 8) {
 338         /* FIXME: optimised general case */
 339         return;
 340     }
 341 #endif
 342
 343     /* general case */
 344     if (predictor_coef_num > 0) {
 345         for (i = predictor_coef_num + 1; i < output_size; i++) {
 346             int j;
 347             int sum = 0;
 348             int outval;
 349             int error_val = error_buffer[i];
 350
 351             for (j = 0; j < predictor_coef_num; j++) {
 352                 sum += (buffer_out[predictor_coef_num-j] - buffer_out[0]) *
 353                        predictor_coef_table[j];
 354             }
 355
 356             outval = (1 << (predictor_quantitization-1)) + sum;
 357             outval = outval >> predictor_quantitization;
 358             outval = outval + buffer_out[0] + error_val;
 359             outval = SIGN_EXTENDED32(outval, readsamplesize);
 360
 361             buffer_out[predictor_coef_num+1] = outval;
 362
 363             if (error_val > 0) {
 364                 int predictor_num = predictor_coef_num - 1;
 365
 366                 while (predictor_num >= 0 && error_val > 0) {
 367                     int val = buffer_out[0] - buffer_out[predictor_coef_num - predictor_num];
 368                     int sign = SIGN_ONLY(val);
 369
 370                     predictor_coef_table[predictor_num] -= sign;
 371
 372                     val *= sign; /* absolute value */
 373
 374                     error_val -= ((val >> predictor_quantitization) *
 375                                   (predictor_coef_num - predictor_num));
 376
 377                     predictor_num--;
 378                 }
 379             } else if (error_val < 0) {
 380                 int predictor_num = predictor_coef_num - 1;
 381
 382                 while (predictor_num >= 0 && error_val < 0) {
 383                     int val = buffer_out[0] - buffer_out[predictor_coef_num - predictor_num];
 384                     int sign = - SIGN_ONLY(val);
 385
 386                     predictor_coef_table[predictor_num] -= sign;
 387
 388                     val *= sign; /* neg value */
 389
 390                     error_val -= ((val >> predictor_quantitization) *
 391                                   (predictor_coef_num - predictor_num));
 392
 393                     predictor_num--;
 394                 }
 395             }
 396
 397             buffer_out++;
 398         }
 399     }
 400 }
 401
 402 static void reconstruct_stereo_16(int32_t *buffer[MAX_CHANNELS],
 403                                   int16_t *buffer_out,
 404                                   int numchannels, int numsamples,
 405                                   uint8_t interlacing_shift,
 406                                   uint8_t interlacing_leftweight)
 407 {
 408     int i;
 409     if (numsamples <= 0)
 410         return;
 411
 412     /* weighted interlacing */
 413     if (interlacing_leftweight) {
 414         for (i = 0; i < numsamples; i++) {
 415             int32_t a, b;
 416
 417             a = buffer[0][i];
 418             b = buffer[1][i];
 419
 420             a -= (b * interlacing_leftweight) >> interlacing_shift;
 421             b += a;
 422
 423             buffer_out[i*numchannels] = b;
 424             buffer_out[i*numchannels + 1] = a;
 425         }
 426
 427         return;
 428     }
 429
 430     /* otherwise basic interlacing took place */
 431     for (i = 0; i < numsamples; i++) {
 432         int16_t left, right;
 433
 434         left = buffer[0][i];
 435         right = buffer[1][i];
 436
 437         buffer_out[i*numchannels] = left;
 438         buffer_out[i*numchannels + 1] = right;
 439     }
 440 }
 441
 442 static int alac_decode_frame(AVCodecContext *avctx,
 443                              void *outbuffer, int *outputsize,
 444                              uint8_t *inbuffer, int input_buffer_size)
 445 {
 446     ALACContext *alac = avctx->priv_data;
 447
 448     int channels;
 449     int32_t outputsamples;
 450     int hassize;
 451     int readsamplesize;
 452     int wasted_bytes;
 453     int isnotcompressed;
 454     uint8_t interlacing_shift;
 455     uint8_t interlacing_leftweight;
 456
 457     /* short-circuit null buffers */
 458     if (!inbuffer || !input_buffer_size)
 459         return input_buffer_size;
 460
 461     /* initialize from the extradata */
 462     if (!alac->context_initialized) {
 463         if (alac->avctx->extradata_size != ALAC_EXTRADATA_SIZE) {
 464             av_log(avctx, AV_LOG_ERROR, "alac: expected %d extradata bytes\n",
 465                 ALAC_EXTRADATA_SIZE);
 466             return input_buffer_size;
 467         }
 468         if (alac_set_info(alac)) {
 469             av_log(avctx, AV_LOG_ERROR, "alac: set_info failed\n");
 470             return input_buffer_size;
 471         }
 472         alac->context_initialized = 1;
 473     }
 474
 475     init_get_bits(&alac->gb, inbuffer, input_buffer_size * 8);
 476
 477     channels = get_bits(&alac->gb, 3) + 1;
 478     if (channels > MAX_CHANNELS) {
 479         av_log(avctx, AV_LOG_ERROR, "channels > %d not supported\n",
 480                MAX_CHANNELS);
 481         return input_buffer_size;
 482     }
 483
 484     /* 2^result = something to do with output waiting.
 485      * perhaps matters if we read > 1 frame in a pass?
 486      */
 487     get_bits(&alac->gb, 4);
 488
 489     get_bits(&alac->gb, 12); /* unknown, skip 12 bits */
 490
 491     /* the output sample size is stored soon */
 492     hassize = get_bits(&alac->gb, 1);
 493
 494     wasted_bytes = get_bits(&alac->gb, 2); /* unknown ? */
 495
 496     /* whether the frame is compressed */
 497     isnotcompressed = get_bits(&alac->gb, 1);
 498
 499     if (hassize) {
 500         /* now read the number of samples as a 32bit integer */
 501         outputsamples = get_bits(&alac->gb, 32);
 502     } else
 503         outputsamples = alac->setinfo_max_samples_per_frame;
 504
 505     *outputsize = outputsamples * alac->bytespersample;
 506     readsamplesize = alac->setinfo_sample_size - (wasted_bytes * 8) + channels - 1;
 507
 508     if (!isnotcompressed) {
 509         /* so it is compressed */
 510         int16_t predictor_coef_table[channels][32];
 511         int predictor_coef_num[channels];
 512         int prediction_type[channels];
 513         int prediction_quantitization[channels];
 514         int ricemodifier[channels];
 515         int i, chan;
 516
 517         interlacing_shift = get_bits(&alac->gb, 8);
 518         interlacing_leftweight = get_bits(&alac->gb, 8);
 519
 520         for (chan = 0; chan < channels; chan++) {
 521             prediction_type[chan] = get_bits(&alac->gb, 4);
 522             prediction_quantitization[chan] = get_bits(&alac->gb, 4);
 523
 524             ricemodifier[chan] = get_bits(&alac->gb, 3);
 525             predictor_coef_num[chan] = get_bits(&alac->gb, 5);
 526
 527             /* read the predictor table */
 528             for (i = 0; i < predictor_coef_num[chan]; i++)
 529                 predictor_coef_table[chan][i] = (int16_t)get_bits(&alac->gb, 16);
 530         }
 531
 532         if (wasted_bytes)
 533             av_log(avctx, AV_LOG_ERROR, "FIXME: unimplemented, unhandling of wasted_bytes\n");
 534
 535         for (chan = 0; chan < channels; chan++) {
 536             bastardized_rice_decompress(alac,
 537                                         alac->predicterror_buffer[chan],
 538                                         outputsamples,
 539                                         readsamplesize,
 540                                         alac->setinfo_rice_initialhistory,
 541                                         alac->setinfo_rice_kmodifier,
 542                                         ricemodifier[chan] * alac->setinfo_rice_historymult / 4,
 543                                         (1 << alac->setinfo_rice_kmodifier) - 1);
 544
 545             if (prediction_type[chan] == 0) {
 546                 /* adaptive fir */
 547                 predictor_decompress_fir_adapt(alac->predicterror_buffer[chan],
 548                                                alac->outputsamples_buffer[chan],
 549                                                outputsamples,
 550                                                readsamplesize,
 551                                                predictor_coef_table[chan],
 552                                                predictor_coef_num[chan],
 553                                                prediction_quantitization[chan]);
 554             } else {
 555                 av_log(avctx, AV_LOG_ERROR, "FIXME: unhandled prediction type: %i\n", prediction_type[chan]);
 556                 /* I think the only other prediction type (or perhaps this is
 557                  * just a boolean?) runs adaptive fir twice.. like:
 558                  * predictor_decompress_fir_adapt(predictor_error, tempout, ...)
 559                  * predictor_decompress_fir_adapt(predictor_error, outputsamples ...)
 560                  * little strange..
 561                  */
 562             }
 563         }
 564     } else {
 565         /* not compressed, easy case */
 566         if (alac->setinfo_sample_size <= 16) {
 567             int i, chan;
 568             for (chan = 0; chan < channels; chan++)
 569                 for (i = 0; i < outputsamples; i++) {
 570                     int32_t audiobits;
 571
 572                     audiobits = get_bits(&alac->gb, alac->setinfo_sample_size);
 573                     audiobits = SIGN_EXTENDED32(audiobits, readsamplesize);
 574
 575                     alac->outputsamples_buffer[chan][i] = audiobits;
 576                 }
 577         } else {
 578             int i, chan;
 579             for (chan = 0; chan < channels; chan++)
 580                 for (i = 0; i < outputsamples; i++) {
 581                     int32_t audiobits;
 582
 583                     audiobits = get_bits(&alac->gb, 16);
 584                     /* special case of sign extension..
 585                      * as we'll be ORing the low 16bits into this */
 586                     audiobits = audiobits << 16;
 587                     audiobits = audiobits >> (32 - alac->setinfo_sample_size);
 588                     audiobits |= get_bits(&alac->gb, alac->setinfo_sample_size - 16);
 589
 590                     alac->outputsamples_buffer[chan][i] = audiobits;
 591                 }
 592         }
 593         /* wasted_bytes = 0; */
 594         interlacing_shift = 0;
 595         interlacing_leftweight = 0;
 596     }
 597
 598     switch(alac->setinfo_sample_size) {
 599     case 16:
 600         if (channels == 2) {
 601             reconstruct_stereo_16(alac->outputsamples_buffer,
 602                            (int16_t*)outbuffer,
 603                            alac->numchannels,
 604                            outputsamples,
 605                            interlacing_shift,
 606                            interlacing_leftweight);
 607         } else {
 608             int i;
 609             for (i = 0; i < outputsamples; i++) {
 610                 int16_t sample = alac->outputsamples_buffer[0][i];
 611                 ((int16_t*)outbuffer)[i * alac->numchannels] = sample;
 612             }
 613         }
 614         break;
 615     case 20:
 616     case 24:
 617     case 32:
 618         av_log(avctx, AV_LOG_ERROR, "FIXME: unimplemented sample size %i\n", alac->setinfo_sample_size);
 619         break;
 620     default:
 621         break;
 622     }
 623
 624     return input_buffer_size;
 625 }
 626
 627 static int alac_decode_init(AVCodecContext * avctx)
 628 {
 629     ALACContext *alac = avctx->priv_data;
 630     alac->avctx = avctx;
 631     alac->context_initialized = 0;
 632
 633     alac->samplesize = alac->avctx->bits_per_sample;
 634     alac->numchannels = alac->avctx->channels;
 635     alac->bytespersample = (alac->samplesize / 8) * alac->numchannels;
 636
 637     return 0;
 638 }
 639
 640 static int alac_decode_close(AVCodecContext *avctx)
 641 {
 642     ALACContext *alac = avctx->priv_data;
 643
 644     int chan;
 645     for (chan = 0; chan < MAX_CHANNELS; chan++) {
 646         av_free(alac->predicterror_buffer[chan]);
 647         av_free(alac->outputsamples_buffer[chan]);
 648     }
 649
 650     return 0;
 651 }
 652
 653 AVCodec alac_decoder = {
 654     "alac",
 655     CODEC_TYPE_AUDIO,
 656     CODEC_ID_ALAC,
 657     sizeof(ALACContext),
 658     alac_decode_init,
 659     NULL,
 660     alac_decode_close,
 661     alac_decode_frame,
 662 };