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 #include "unary.h"
  59
  60 #define ALAC_EXTRADATA_SIZE 36
  61 #define MAX_CHANNELS 2
  62
  63 typedef struct {
  64
  65     AVCodecContext *avctx;
  66     GetBitContext gb;
  67     /* init to 0; first frame decode should initialize from extradata and
  68      * set this to 1 */
  69     int context_initialized;
  70
  71     int samplesize;
  72     int numchannels;
  73     int bytespersample;
  74
  75     /* buffers */
  76     int32_t *predicterror_buffer[MAX_CHANNELS];
  77
  78     int32_t *outputsamples_buffer[MAX_CHANNELS];
  79
  80     /* stuff from setinfo */
  81     uint32_t setinfo_max_samples_per_frame; /* 0x1000 = 4096 */    /* max samples per frame? */
  82     uint8_t setinfo_7a; /* 0x00 */
  83     uint8_t setinfo_sample_size; /* 0x10 */
  84     uint8_t setinfo_rice_historymult; /* 0x28 */
  85     uint8_t setinfo_rice_initialhistory; /* 0x0a */
  86     uint8_t setinfo_rice_kmodifier; /* 0x0e */
  87     uint8_t setinfo_7f; /* 0x02 */
  88     uint16_t setinfo_80; /* 0x00ff */
  89     uint32_t setinfo_82; /* 0x000020e7 */ /* max sample size?? */
  90     uint32_t setinfo_86; /* 0x00069fe4 */ /* bit rate (average)?? */
  91     uint32_t setinfo_8a_rate; /* 0x0000ac44 */
  92     /* end setinfo stuff */
  93
  94 } ALACContext;
  95
  96 static void allocate_buffers(ALACContext *alac)
  97 {
  98     int chan;
  99     for (chan = 0; chan < MAX_CHANNELS; chan++) {
 100         alac->predicterror_buffer[chan] =
 101             av_malloc(alac->setinfo_max_samples_per_frame * 4);
 102
 103         alac->outputsamples_buffer[chan] =
 104             av_malloc(alac->setinfo_max_samples_per_frame * 4);
 105     }
 106 }
 107
 108 static int alac_set_info(ALACContext *alac)
 109 {
 110     const unsigned char *ptr = alac->avctx->extradata;
 111
 112     ptr += 4; /* size */
 113     ptr += 4; /* alac */
 114     ptr += 4; /* 0 ? */
 115
 116     if(AV_RB32(ptr) >= UINT_MAX/4){
 117         av_log(alac->avctx, AV_LOG_ERROR, "setinfo_max_samples_per_frame too large\n");
 118         return -1;
 119     }
 120
 121     /* buffer size / 2 ? */
 122     alac->setinfo_max_samples_per_frame = bytestream_get_be32(&ptr);
 123     alac->setinfo_7a                    = *ptr++;
 124     alac->setinfo_sample_size           = *ptr++;
 125     alac->setinfo_rice_historymult      = *ptr++;
 126     alac->setinfo_rice_initialhistory   = *ptr++;
 127     alac->setinfo_rice_kmodifier        = *ptr++;
 128     /* channels? */
 129     alac->setinfo_7f                    = *ptr++;
 130     alac->setinfo_80                    = bytestream_get_be16(&ptr);
 131     /* max coded frame size */
 132     alac->setinfo_82                    = bytestream_get_be32(&ptr);
 133     /* bitrate ? */
 134     alac->setinfo_86                    = bytestream_get_be32(&ptr);
 135     /* samplerate */
 136     alac->setinfo_8a_rate               = bytestream_get_be32(&ptr);
 137
 138     allocate_buffers(alac);
 139
 140     return 0;
 141 }
 142
 143 static inline int count_leading_zeros(int32_t input)
 144 {
 145     return 31-av_log2(input);
 146 }
 147
 148 static void bastardized_rice_decompress(ALACContext *alac,
 149                                  int32_t *output_buffer,
 150                                  int output_size,
 151                                  int readsamplesize, /* arg_10 */
 152                                  int rice_initialhistory, /* arg424->b */
 153                                  int rice_kmodifier, /* arg424->d */
 154                                  int rice_historymult, /* arg424->c */
 155                                  int rice_kmodifier_mask /* arg424->e */
 156         )
 157 {
 158     int output_count;
 159     unsigned int history = rice_initialhistory;
 160     int sign_modifier = 0;
 161
 162     for (output_count = 0; output_count < output_size; output_count++) {
 163         int32_t x;
 164         int32_t x_modified;
 165         int32_t final_val;
 166
 167         /* read x - number of 1s before 0 represent the rice */
 168         x = get_unary_0_9(&alac->gb);
 169
 170         if (x > 8) { /* RICE THRESHOLD */
 171             /* use alternative encoding */
 172             int32_t value;
 173
 174             value = get_bits(&alac->gb, readsamplesize);
 175
 176             /* mask value to readsamplesize size */
 177             if (readsamplesize != 32)
 178                 value &= (0xffffffff >> (32 - readsamplesize));
 179
 180             x = value;
 181         } else {
 182             /* standard rice encoding */
 183             int extrabits;
 184             int k; /* size of extra bits */
 185
 186             /* read k, that is bits as is */
 187             k = 31 - rice_kmodifier - count_leading_zeros((history >> 9) + 3);
 188
 189             if (k < 0)
 190                 k += rice_kmodifier;
 191             else
 192                 k = rice_kmodifier;
 193
 194             if (k != 1) {
 195                 extrabits = show_bits(&alac->gb, k);
 196
 197                 /* multiply x by 2^k - 1, as part of their strange algorithm */
 198                 x = (x << k) - x;
 199
 200                 if (extrabits > 1) {
 201                     x += extrabits - 1;
 202                     skip_bits(&alac->gb, k);
 203                 } else
 204                     skip_bits(&alac->gb, k - 1);
 205             }
 206         }
 207
 208         x_modified = sign_modifier + x;
 209         final_val = (x_modified + 1) / 2;
 210         if (x_modified & 1) final_val *= -1;
 211
 212         output_buffer[output_count] = final_val;
 213
 214         sign_modifier = 0;
 215
 216         /* now update the history */
 217         history += x_modified * rice_historymult
 218                    - ((history * rice_historymult) >> 9);
 219
 220         if (x_modified > 0xffff)
 221             history = 0xffff;
 222
 223         /* special case: there may be compressed blocks of 0 */
 224         if ((history < 128) && (output_count+1 < output_size)) {
 225             int block_size;
 226
 227             sign_modifier = 1;
 228
 229             x = get_unary_0_9(&alac->gb);
 230
 231             if (x > 8) {
 232                 block_size = get_bits(&alac->gb, 16);
 233                 block_size &= 0xffff;
 234             } else {
 235                 int k;
 236                 int extrabits;
 237
 238                 k = count_leading_zeros(history) + ((history + 16) >> 6 /* / 64 */) - 24;
 239
 240                 extrabits = show_bits(&alac->gb, k);
 241
 242                 block_size = (((1 << k) - 1) & rice_kmodifier_mask) * x
 243                            + extrabits - 1;
 244
 245                 if (extrabits < 2) {
 246                     x = 1 - extrabits;
 247                     block_size += x;
 248                     skip_bits(&alac->gb, k - 1);
 249                 } else {
 250                     skip_bits(&alac->gb, k);
 251                 }
 252             }
 253
 254             if (block_size > 0) {
 255                 memset(&output_buffer[output_count+1], 0, block_size * 4);
 256                 output_count += block_size;
 257             }
 258
 259             if (block_size > 0xffff)
 260                 sign_modifier = 0;
 261
 262             history = 0;
 263         }
 264     }
 265 }
 266
 267 static inline int32_t extend_sign32(int32_t val, int bits)
 268 {
 269     return (val << (32 - bits)) >> (32 - bits);
 270 }
 271
 272 static inline int sign_only(int v)
 273 {
 274     return v ? FFSIGN(v) : 0;
 275 }
 276
 277 static void predictor_decompress_fir_adapt(int32_t *error_buffer,
 278                                            int32_t *buffer_out,
 279                                            int output_size,
 280                                            int readsamplesize,
 281                                            int16_t *predictor_coef_table,
 282                                            int predictor_coef_num,
 283                                            int predictor_quantitization)
 284 {
 285     int i;
 286
 287     /* first sample always copies */
 288     *buffer_out = *error_buffer;
 289
 290     if (!predictor_coef_num) {
 291         if (output_size <= 1)
 292             return;
 293
 294         memcpy(buffer_out+1, error_buffer+1, (output_size-1) * 4);
 295         return;
 296     }
 297
 298     if (predictor_coef_num == 0x1f) { /* 11111 - max value of predictor_coef_num */
 299       /* second-best case scenario for fir decompression,
 300        * error describes a small difference from the previous sample only
 301        */
 302         if (output_size <= 1)
 303             return;
 304         for (i = 0; i < output_size - 1; i++) {
 305             int32_t prev_value;
 306             int32_t error_value;
 307
 308             prev_value = buffer_out[i];
 309             error_value = error_buffer[i+1];
 310             buffer_out[i+1] =
 311                 extend_sign32((prev_value + error_value), readsamplesize);
 312         }
 313         return;
 314     }
 315
 316     /* read warm-up samples */
 317     if (predictor_coef_num > 0)
 318         for (i = 0; i < predictor_coef_num; i++) {
 319             int32_t val;
 320
 321             val = buffer_out[i] + error_buffer[i+1];
 322             val = extend_sign32(val, readsamplesize);
 323             buffer_out[i+1] = val;
 324         }
 325
 326 #if 0
 327     /* 4 and 8 are very common cases (the only ones i've seen). these
 328      * should be unrolled and optimized
 329      */
 330     if (predictor_coef_num == 4) {
 331         /* FIXME: optimized general case */
 332         return;
 333     }
 334
 335     if (predictor_coef_table == 8) {
 336         /* FIXME: optimized general case */
 337         return;
 338     }
 339 #endif
 340
 341     /* general case */
 342     if (predictor_coef_num > 0) {
 343         for (i = predictor_coef_num + 1; i < output_size; i++) {
 344             int j;
 345             int sum = 0;
 346             int outval;
 347             int error_val = error_buffer[i];
 348
 349             for (j = 0; j < predictor_coef_num; j++) {
 350                 sum += (buffer_out[predictor_coef_num-j] - buffer_out[0]) *
 351                        predictor_coef_table[j];
 352             }
 353
 354             outval = (1 << (predictor_quantitization-1)) + sum;
 355             outval = outval >> predictor_quantitization;
 356             outval = outval + buffer_out[0] + error_val;
 357             outval = extend_sign32(outval, readsamplesize);
 358
 359             buffer_out[predictor_coef_num+1] = outval;
 360
 361             if (error_val > 0) {
 362                 int predictor_num = predictor_coef_num - 1;
 363
 364                 while (predictor_num >= 0 && error_val > 0) {
 365                     int val = buffer_out[0] - buffer_out[predictor_coef_num - predictor_num];
 366                     int sign = sign_only(val);
 367
 368                     predictor_coef_table[predictor_num] -= sign;
 369
 370                     val *= sign; /* absolute value */
 371
 372                     error_val -= ((val >> predictor_quantitization) *
 373                                   (predictor_coef_num - predictor_num));
 374
 375                     predictor_num--;
 376                 }
 377             } else if (error_val < 0) {
 378                 int predictor_num = predictor_coef_num - 1;
 379
 380                 while (predictor_num >= 0 && error_val < 0) {
 381                     int val = buffer_out[0] - buffer_out[predictor_coef_num - predictor_num];
 382                     int sign = - sign_only(val);
 383
 384                     predictor_coef_table[predictor_num] -= sign;
 385
 386                     val *= sign; /* neg value */
 387
 388                     error_val -= ((val >> predictor_quantitization) *
 389                                   (predictor_coef_num - predictor_num));
 390
 391                     predictor_num--;
 392                 }
 393             }
 394
 395             buffer_out++;
 396         }
 397     }
 398 }
 399
 400 static void reconstruct_stereo_16(int32_t *buffer[MAX_CHANNELS],
 401                                   int16_t *buffer_out,
 402                                   int numchannels, int numsamples,
 403                                   uint8_t interlacing_shift,
 404                                   uint8_t interlacing_leftweight)
 405 {
 406     int i;
 407     if (numsamples <= 0)
 408         return;
 409
 410     /* weighted interlacing */
 411     if (interlacing_leftweight) {
 412         for (i = 0; i < numsamples; i++) {
 413             int32_t a, b;
 414
 415             a = buffer[0][i];
 416             b = buffer[1][i];
 417
 418             a -= (b * interlacing_leftweight) >> interlacing_shift;
 419             b += a;
 420
 421             buffer_out[i*numchannels] = b;
 422             buffer_out[i*numchannels + 1] = a;
 423         }
 424
 425         return;
 426     }
 427
 428     /* otherwise basic interlacing took place */
 429     for (i = 0; i < numsamples; i++) {
 430         int16_t left, right;
 431
 432         left = buffer[0][i];
 433         right = buffer[1][i];
 434
 435         buffer_out[i*numchannels] = left;
 436         buffer_out[i*numchannels + 1] = right;
 437     }
 438 }
 439
 440 static int alac_decode_frame(AVCodecContext *avctx,
 441                              void *outbuffer, int *outputsize,
 442                              const uint8_t *inbuffer, int input_buffer_size)
 443 {
 444     ALACContext *alac = avctx->priv_data;
 445
 446     int channels;
 447     int32_t outputsamples;
 448     int hassize;
 449     int readsamplesize;
 450     int wasted_bytes;
 451     int isnotcompressed;
 452     uint8_t interlacing_shift;
 453     uint8_t interlacing_leftweight;
 454
 455     /* short-circuit null buffers */
 456     if (!inbuffer || !input_buffer_size)
 457         return input_buffer_size;
 458
 459     /* initialize from the extradata */
 460     if (!alac->context_initialized) {
 461         if (alac->avctx->extradata_size != ALAC_EXTRADATA_SIZE) {
 462             av_log(avctx, AV_LOG_ERROR, "alac: expected %d extradata bytes\n",
 463                 ALAC_EXTRADATA_SIZE);
 464             return input_buffer_size;
 465         }
 466         if (alac_set_info(alac)) {
 467             av_log(avctx, AV_LOG_ERROR, "alac: set_info failed\n");
 468             return input_buffer_size;
 469         }
 470         alac->context_initialized = 1;
 471     }
 472
 473     init_get_bits(&alac->gb, inbuffer, input_buffer_size * 8);
 474
 475     channels = get_bits(&alac->gb, 3) + 1;
 476     if (channels > MAX_CHANNELS) {
 477         av_log(avctx, AV_LOG_ERROR, "channels > %d not supported\n",
 478                MAX_CHANNELS);
 479         return input_buffer_size;
 480     }
 481
 482     /* 2^result = something to do with output waiting.
 483      * perhaps matters if we read > 1 frame in a pass?
 484      */
 485     skip_bits(&alac->gb, 4);
 486
 487     skip_bits(&alac->gb, 12); /* unknown, skip 12 bits */
 488
 489     /* the output sample size is stored soon */
 490     hassize = get_bits1(&alac->gb);
 491
 492     wasted_bytes = get_bits(&alac->gb, 2); /* unknown ? */
 493
 494     /* whether the frame is compressed */
 495     isnotcompressed = get_bits1(&alac->gb);
 496
 497     if (hassize) {
 498         /* now read the number of samples as a 32bit integer */
 499         outputsamples = get_bits(&alac->gb, 32);
 500     } else
 501         outputsamples = alac->setinfo_max_samples_per_frame;
 502
 503     *outputsize = outputsamples * alac->bytespersample;
 504     readsamplesize = alac->setinfo_sample_size - (wasted_bytes * 8) + channels - 1;
 505
 506     if (!isnotcompressed) {
 507         /* so it is compressed */
 508         int16_t predictor_coef_table[channels][32];
 509         int predictor_coef_num[channels];
 510         int prediction_type[channels];
 511         int prediction_quantitization[channels];
 512         int ricemodifier[channels];
 513         int i, chan;
 514
 515         interlacing_shift = get_bits(&alac->gb, 8);
 516         interlacing_leftweight = get_bits(&alac->gb, 8);
 517
 518         for (chan = 0; chan < channels; chan++) {
 519             prediction_type[chan] = get_bits(&alac->gb, 4);
 520             prediction_quantitization[chan] = get_bits(&alac->gb, 4);
 521
 522             ricemodifier[chan] = get_bits(&alac->gb, 3);
 523             predictor_coef_num[chan] = get_bits(&alac->gb, 5);
 524
 525             /* read the predictor table */
 526             for (i = 0; i < predictor_coef_num[chan]; i++)
 527                 predictor_coef_table[chan][i] = (int16_t)get_bits(&alac->gb, 16);
 528         }
 529
 530         if (wasted_bytes)
 531             av_log(avctx, AV_LOG_ERROR, "FIXME: unimplemented, unhandling of wasted_bytes\n");
 532
 533         for (chan = 0; chan < channels; chan++) {
 534             bastardized_rice_decompress(alac,
 535                                         alac->predicterror_buffer[chan],
 536                                         outputsamples,
 537                                         readsamplesize,
 538                                         alac->setinfo_rice_initialhistory,
 539                                         alac->setinfo_rice_kmodifier,
 540                                         ricemodifier[chan] * alac->setinfo_rice_historymult / 4,
 541                                         (1 << alac->setinfo_rice_kmodifier) - 1);
 542
 543             if (prediction_type[chan] == 0) {
 544                 /* adaptive fir */
 545                 predictor_decompress_fir_adapt(alac->predicterror_buffer[chan],
 546                                                alac->outputsamples_buffer[chan],
 547                                                outputsamples,
 548                                                readsamplesize,
 549                                                predictor_coef_table[chan],
 550                                                predictor_coef_num[chan],
 551                                                prediction_quantitization[chan]);
 552             } else {
 553                 av_log(avctx, AV_LOG_ERROR, "FIXME: unhandled prediction type: %i\n", prediction_type[chan]);
 554                 /* I think the only other prediction type (or perhaps this is
 555                  * just a boolean?) runs adaptive fir twice.. like:
 556                  * predictor_decompress_fir_adapt(predictor_error, tempout, ...)
 557                  * predictor_decompress_fir_adapt(predictor_error, outputsamples ...)
 558                  * little strange..
 559                  */
 560             }
 561         }
 562     } else {
 563         /* not compressed, easy case */
 564         if (alac->setinfo_sample_size <= 16) {
 565             int i, chan;
 566             for (chan = 0; chan < channels; chan++)
 567                 for (i = 0; i < outputsamples; i++) {
 568                     int32_t audiobits;
 569
 570                     audiobits = get_bits(&alac->gb, alac->setinfo_sample_size);
 571                     audiobits = extend_sign32(audiobits, readsamplesize);
 572
 573                     alac->outputsamples_buffer[chan][i] = audiobits;
 574                 }
 575         } else {
 576             int i, chan;
 577             for (chan = 0; chan < channels; chan++)
 578                 for (i = 0; i < outputsamples; i++) {
 579                     int32_t audiobits;
 580
 581                     audiobits = get_bits(&alac->gb, 16);
 582                     /* special case of sign extension..
 583                      * as we'll be ORing the low 16bits into this */
 584                     audiobits = audiobits << 16;
 585                     audiobits = audiobits >> (32 - alac->setinfo_sample_size);
 586                     audiobits |= get_bits(&alac->gb, alac->setinfo_sample_size - 16);
 587
 588                     alac->outputsamples_buffer[chan][i] = audiobits;
 589                 }
 590         }
 591         /* wasted_bytes = 0; */
 592         interlacing_shift = 0;
 593         interlacing_leftweight = 0;
 594     }
 595
 596     switch(alac->setinfo_sample_size) {
 597     case 16:
 598         if (channels == 2) {
 599             reconstruct_stereo_16(alac->outputsamples_buffer,
 600                                   (int16_t*)outbuffer,
 601                                   alac->numchannels,
 602                                   outputsamples,
 603                                   interlacing_shift,
 604                                   interlacing_leftweight);
 605         } else {
 606             int i;
 607             for (i = 0; i < outputsamples; i++) {
 608                 int16_t sample = alac->outputsamples_buffer[0][i];
 609                 ((int16_t*)outbuffer)[i * alac->numchannels] = sample;
 610             }
 611         }
 612         break;
 613     case 20:
 614     case 24:
 615         // It is not clear if there exist any encoder that creates 24 bit ALAC
 616         // files. iTunes convert 24 bit raw files to 16 bit before encoding.
 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 av_cold 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 av_cold 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 };