libavcodec/flacdec.c

   1 /*
   2  * FLAC (Free Lossless Audio Codec) decoder
   3  * Copyright (c) 2003 Alex Beregszaszi
   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 libavcodec/flacdec.c
  24  * FLAC (Free Lossless Audio Codec) decoder
  25  * @author Alex Beregszaszi
  26  *
  27  * For more information on the FLAC format, visit:
  28  *  http://flac.sourceforge.net/
  29  *
  30  * This decoder can be used in 1 of 2 ways: Either raw FLAC data can be fed
  31  * through, starting from the initial 'fLaC' signature; or by passing the
  32  * 34-byte streaminfo structure through avctx->extradata[_size] followed
  33  * by data starting with the 0xFFF8 marker.
  34  */
  35
  36 #include <limits.h>
  37
  38 #include "libavutil/crc.h"
  39 #include "avcodec.h"
  40 #include "internal.h"
  41 #include "bitstream.h"
  42 #include "golomb.h"
  43 #include "flac.h"
  44
  45 #undef NDEBUG
  46 #include <assert.h>
  47
  48 #define MAX_CHANNELS 8
  49 #define MAX_BLOCKSIZE 65535
  50
  51 enum decorrelation_type {
  52     INDEPENDENT,
  53     LEFT_SIDE,
  54     RIGHT_SIDE,
  55     MID_SIDE,
  56 };
  57
  58 typedef struct FLACContext {
  59     FLACSTREAMINFO
  60
  61     AVCodecContext *avctx;                  ///< parent AVCodecContext
  62     GetBitContext gb;                       ///< GetBitContext initialized to start at the current frame
  63
  64     int blocksize;                          ///< number of samples in the current frame
  65     int curr_bps;                           ///< bps for current subframe, adjusted for channel correlation and wasted bits
  66     int sample_shift;                       ///< shift required to make output samples 16-bit or 32-bit
  67     int is32;                               ///< flag to indicate if output should be 32-bit instead of 16-bit
  68     enum decorrelation_type decorrelation;  ///< channel decorrelation type in the current frame
  69
  70     int32_t *decoded[MAX_CHANNELS];         ///< decoded samples
  71     uint8_t *bitstream;
  72     unsigned int bitstream_size;
  73     unsigned int bitstream_index;
  74     unsigned int allocated_bitstream_size;
  75 } FLACContext;
  76
  77 static const int sample_rate_table[] =
  78 { 0,
  79   88200, 176400, 192000,
  80   8000, 16000, 22050, 24000, 32000, 44100, 48000, 96000,
  81   0, 0, 0, 0 };
  82
  83 static const int sample_size_table[] =
  84 { 0, 8, 12, 0, 16, 20, 24, 0 };
  85
  86 static const int blocksize_table[] = {
  87      0,    192, 576<<0, 576<<1, 576<<2, 576<<3,      0,      0,
  88 256<<0, 256<<1, 256<<2, 256<<3, 256<<4, 256<<5, 256<<6, 256<<7
  89 };
  90
  91 static int64_t get_utf8(GetBitContext *gb)
  92 {
  93     int64_t val;
  94     GET_UTF8(val, get_bits(gb, 8), return -1;)
  95     return val;
  96 }
  97
  98 static void allocate_buffers(FLACContext *s);
  99
 100 int ff_flac_is_extradata_valid(AVCodecContext *avctx,
 101                                enum FLACExtradataFormat *format,
 102                                uint8_t **streaminfo_start)
 103 {
 104     if (!avctx->extradata || avctx->extradata_size < FLAC_STREAMINFO_SIZE) {
 105         av_log(avctx, AV_LOG_ERROR, "extradata NULL or too small.\n");
 106         return 0;
 107     }
 108     if (AV_RL32(avctx->extradata) != MKTAG('f','L','a','C')) {
 109         /* extradata contains STREAMINFO only */
 110         if (avctx->extradata_size != FLAC_STREAMINFO_SIZE) {
 111             av_log(avctx, AV_LOG_WARNING, "extradata contains %d bytes too many.\n",
 112                    FLAC_STREAMINFO_SIZE-avctx->extradata_size);
 113         }
 114         *format = FLAC_EXTRADATA_FORMAT_STREAMINFO;
 115         *streaminfo_start = avctx->extradata;
 116     } else {
 117         if (avctx->extradata_size < 8+FLAC_STREAMINFO_SIZE) {
 118             av_log(avctx, AV_LOG_ERROR, "extradata too small.\n");
 119             return 0;
 120         }
 121         *format = FLAC_EXTRADATA_FORMAT_FULL_HEADER;
 122         *streaminfo_start = &avctx->extradata[8];
 123     }
 124     return 1;
 125 }
 126
 127 static av_cold int flac_decode_init(AVCodecContext *avctx)
 128 {
 129     enum FLACExtradataFormat format;
 130     uint8_t *streaminfo;
 131     FLACContext *s = avctx->priv_data;
 132     s->avctx = avctx;
 133
 134     avctx->sample_fmt = SAMPLE_FMT_S16;
 135
 136     /* for now, the raw FLAC header is allowed to be passed to the decoder as
 137        frame data instead of extradata. */
 138     if (!avctx->extradata)
 139         return 0;
 140
 141     if (!ff_flac_is_extradata_valid(avctx, &format, &streaminfo))
 142         return -1;
 143
 144     /* initialize based on the demuxer-supplied streamdata header */
 145     ff_flac_parse_streaminfo(avctx, (FLACStreaminfo *)s, streaminfo);
 146     allocate_buffers(s);
 147
 148     return 0;
 149 }
 150
 151 static void dump_headers(AVCodecContext *avctx, FLACStreaminfo *s)
 152 {
 153     av_log(avctx, AV_LOG_DEBUG, "  Max Blocksize: %d\n", s->max_blocksize);
 154     av_log(avctx, AV_LOG_DEBUG, "  Max Framesize: %d\n", s->max_framesize);
 155     av_log(avctx, AV_LOG_DEBUG, "  Samplerate: %d\n", s->samplerate);
 156     av_log(avctx, AV_LOG_DEBUG, "  Channels: %d\n", s->channels);
 157     av_log(avctx, AV_LOG_DEBUG, "  Bits: %d\n", s->bps);
 158 }
 159
 160 static void allocate_buffers(FLACContext *s)
 161 {
 162     int i;
 163
 164     assert(s->max_blocksize);
 165
 166     if (s->max_framesize == 0 && s->max_blocksize) {
 167         // FIXME header overhead
 168         s->max_framesize= (s->channels * s->bps * s->max_blocksize + 7)/ 8;
 169     }
 170
 171     for (i = 0; i < s->channels; i++) {
 172         s->decoded[i] = av_realloc(s->decoded[i],
 173                                    sizeof(int32_t)*s->max_blocksize);
 174     }
 175
 176     if (s->allocated_bitstream_size < s->max_framesize)
 177         s->bitstream= av_fast_realloc(s->bitstream,
 178                                       &s->allocated_bitstream_size,
 179                                       s->max_framesize);
 180 }
 181
 182 void ff_flac_parse_streaminfo(AVCodecContext *avctx, struct FLACStreaminfo *s,
 183                               const uint8_t *buffer)
 184 {
 185     GetBitContext gb;
 186     init_get_bits(&gb, buffer, FLAC_STREAMINFO_SIZE*8);
 187
 188     /* mandatory streaminfo */
 189     skip_bits(&gb, 16); /* skip min blocksize */
 190     s->max_blocksize = get_bits(&gb, 16);
 191
 192     skip_bits(&gb, 24); /* skip min frame size */
 193     s->max_framesize = get_bits_long(&gb, 24);
 194
 195     s->samplerate = get_bits_long(&gb, 20);
 196     s->channels = get_bits(&gb, 3) + 1;
 197     s->bps = get_bits(&gb, 5) + 1;
 198
 199     avctx->channels = s->channels;
 200     avctx->sample_rate = s->samplerate;
 201     avctx->bits_per_raw_sample = s->bps;
 202     if (s->bps > 16)
 203         avctx->sample_fmt = SAMPLE_FMT_S32;
 204     else
 205         avctx->sample_fmt = SAMPLE_FMT_S16;
 206
 207     s->samples  = get_bits_long(&gb, 32) << 4;
 208     s->samples |= get_bits(&gb, 4);
 209
 210     skip_bits_long(&gb, 64); /* md5 sum */
 211     skip_bits_long(&gb, 64); /* md5 sum */
 212
 213     dump_headers(avctx, s);
 214 }
 215
 216 /**
 217  * Parse a list of metadata blocks. This list of blocks must begin with
 218  * the fLaC marker.
 219  * @param s the flac decoding context containing the gb bit reader used to
 220  *          parse metadata
 221  * @return 1 if some metadata was read, 0 if no fLaC marker was found
 222  */
 223 static int metadata_parse(FLACContext *s)
 224 {
 225     int i, metadata_last, metadata_type, metadata_size, streaminfo_updated=0;
 226     int initial_pos= get_bits_count(&s->gb);
 227
 228     if (show_bits_long(&s->gb, 32) == MKBETAG('f','L','a','C')) {
 229         skip_bits_long(&s->gb, 32);
 230
 231         do {
 232             metadata_last = get_bits1(&s->gb);
 233             metadata_type = get_bits(&s->gb, 7);
 234             metadata_size = get_bits_long(&s->gb, 24);
 235
 236             if (get_bits_count(&s->gb) + 8*metadata_size > s->gb.size_in_bits) {
 237                 skip_bits_long(&s->gb, initial_pos - get_bits_count(&s->gb));
 238                 break;
 239             }
 240
 241             if (metadata_size) {
 242                 switch (metadata_type) {
 243                 case FLAC_METADATA_TYPE_STREAMINFO:
 244                     ff_flac_parse_streaminfo(s->avctx, (FLACStreaminfo *)s,
 245                                              s->gb.buffer+get_bits_count(&s->gb)/8);
 246                     streaminfo_updated = 1;
 247
 248                 default:
 249                     for (i = 0; i < metadata_size; i++)
 250                         skip_bits(&s->gb, 8);
 251                 }
 252             }
 253         } while (!metadata_last);
 254
 255         if (streaminfo_updated)
 256             allocate_buffers(s);
 257         return 1;
 258     }
 259     return 0;
 260 }
 261
 262 static int decode_residuals(FLACContext *s, int channel, int pred_order)
 263 {
 264     int i, tmp, partition, method_type, rice_order;
 265     int sample = 0, samples;
 266
 267     method_type = get_bits(&s->gb, 2);
 268     if (method_type > 1) {
 269         av_log(s->avctx, AV_LOG_ERROR, "illegal residual coding method %d\n",
 270                method_type);
 271         return -1;
 272     }
 273
 274     rice_order = get_bits(&s->gb, 4);
 275
 276     samples= s->blocksize >> rice_order;
 277     if (pred_order > samples) {
 278         av_log(s->avctx, AV_LOG_ERROR, "invalid predictor order: %i > %i\n",
 279                pred_order, samples);
 280         return -1;
 281     }
 282
 283     sample=
 284     i= pred_order;
 285     for (partition = 0; partition < (1 << rice_order); partition++) {
 286         tmp = get_bits(&s->gb, method_type == 0 ? 4 : 5);
 287         if (tmp == (method_type == 0 ? 15 : 31)) {
 288             tmp = get_bits(&s->gb, 5);
 289             for (; i < samples; i++, sample++)
 290                 s->decoded[channel][sample] = get_sbits_long(&s->gb, tmp);
 291         } else {
 292             for (; i < samples; i++, sample++) {
 293                 s->decoded[channel][sample] = get_sr_golomb_flac(&s->gb, tmp, INT_MAX, 0);
 294             }
 295         }
 296         i= 0;
 297     }
 298
 299     return 0;
 300 }
 301
 302 static int decode_subframe_fixed(FLACContext *s, int channel, int pred_order)
 303 {
 304     const int blocksize = s->blocksize;
 305     int32_t *decoded = s->decoded[channel];
 306     int av_uninit(a), av_uninit(b), av_uninit(c), av_uninit(d), i;
 307
 308     /* warm up samples */
 309     for (i = 0; i < pred_order; i++) {
 310         decoded[i] = get_sbits_long(&s->gb, s->curr_bps);
 311     }
 312
 313     if (decode_residuals(s, channel, pred_order) < 0)
 314         return -1;
 315
 316     if (pred_order > 0)
 317         a = decoded[pred_order-1];
 318     if (pred_order > 1)
 319         b = a - decoded[pred_order-2];
 320     if (pred_order > 2)
 321         c = b - decoded[pred_order-2] + decoded[pred_order-3];
 322     if (pred_order > 3)
 323         d = c - decoded[pred_order-2] + 2*decoded[pred_order-3] - decoded[pred_order-4];
 324
 325     switch (pred_order) {
 326     case 0:
 327         break;
 328     case 1:
 329         for (i = pred_order; i < blocksize; i++)
 330             decoded[i] = a += decoded[i];
 331         break;
 332     case 2:
 333         for (i = pred_order; i < blocksize; i++)
 334             decoded[i] = a += b += decoded[i];
 335         break;
 336     case 3:
 337         for (i = pred_order; i < blocksize; i++)
 338             decoded[i] = a += b += c += decoded[i];
 339         break;
 340     case 4:
 341         for (i = pred_order; i < blocksize; i++)
 342             decoded[i] = a += b += c += d += decoded[i];
 343         break;
 344     default:
 345         av_log(s->avctx, AV_LOG_ERROR, "illegal pred order %d\n", pred_order);
 346         return -1;
 347     }
 348
 349     return 0;
 350 }
 351
 352 static int decode_subframe_lpc(FLACContext *s, int channel, int pred_order)
 353 {
 354     int i, j;
 355     int coeff_prec, qlevel;
 356     int coeffs[pred_order];
 357     int32_t *decoded = s->decoded[channel];
 358
 359     /* warm up samples */
 360     for (i = 0; i < pred_order; i++) {
 361         decoded[i] = get_sbits_long(&s->gb, s->curr_bps);
 362     }
 363
 364     coeff_prec = get_bits(&s->gb, 4) + 1;
 365     if (coeff_prec == 16) {
 366         av_log(s->avctx, AV_LOG_ERROR, "invalid coeff precision\n");
 367         return -1;
 368     }
 369     qlevel = get_sbits(&s->gb, 5);
 370     if (qlevel < 0) {
 371         av_log(s->avctx, AV_LOG_ERROR, "qlevel %d not supported, maybe buggy stream\n",
 372                qlevel);
 373         return -1;
 374     }
 375
 376     for (i = 0; i < pred_order; i++) {
 377         coeffs[i] = get_sbits(&s->gb, coeff_prec);
 378     }
 379
 380     if (decode_residuals(s, channel, pred_order) < 0)
 381         return -1;
 382
 383     if (s->bps > 16) {
 384         int64_t sum;
 385         for (i = pred_order; i < s->blocksize; i++) {
 386             sum = 0;
 387             for (j = 0; j < pred_order; j++)
 388                 sum += (int64_t)coeffs[j] * decoded[i-j-1];
 389             decoded[i] += sum >> qlevel;
 390         }
 391     } else {
 392         for (i = pred_order; i < s->blocksize-1; i += 2) {
 393             int c;
 394             int d = decoded[i-pred_order];
 395             int s0 = 0, s1 = 0;
 396             for (j = pred_order-1; j > 0; j--) {
 397                 c = coeffs[j];
 398                 s0 += c*d;
 399                 d = decoded[i-j];
 400                 s1 += c*d;
 401             }
 402             c = coeffs[0];
 403             s0 += c*d;
 404             d = decoded[i] += s0 >> qlevel;
 405             s1 += c*d;
 406             decoded[i+1] += s1 >> qlevel;
 407         }
 408         if (i < s->blocksize) {
 409             int sum = 0;
 410             for (j = 0; j < pred_order; j++)
 411                 sum += coeffs[j] * decoded[i-j-1];
 412             decoded[i] += sum >> qlevel;
 413         }
 414     }
 415
 416     return 0;
 417 }
 418
 419 static inline int decode_subframe(FLACContext *s, int channel)
 420 {
 421     int type, wasted = 0;
 422     int i, tmp;
 423
 424     s->curr_bps = s->bps;
 425     if (channel == 0) {
 426         if (s->decorrelation == RIGHT_SIDE)
 427             s->curr_bps++;
 428     } else {
 429         if (s->decorrelation == LEFT_SIDE || s->decorrelation == MID_SIDE)
 430             s->curr_bps++;
 431     }
 432     if (s->curr_bps > 32) {
 433         ff_log_missing_feature(s->avctx, "decorrelated bit depth > 32", 0);
 434         return -1;
 435     }
 436
 437     if (get_bits1(&s->gb)) {
 438         av_log(s->avctx, AV_LOG_ERROR, "invalid subframe padding\n");
 439         return -1;
 440     }
 441     type = get_bits(&s->gb, 6);
 442
 443     if (get_bits1(&s->gb)) {
 444         wasted = 1;
 445         while (!get_bits1(&s->gb))
 446             wasted++;
 447         s->curr_bps -= wasted;
 448     }
 449
 450 //FIXME use av_log2 for types
 451     if (type == 0) {
 452         tmp = get_sbits_long(&s->gb, s->curr_bps);
 453         for (i = 0; i < s->blocksize; i++)
 454             s->decoded[channel][i] = tmp;
 455     } else if (type == 1) {
 456         for (i = 0; i < s->blocksize; i++)
 457             s->decoded[channel][i] = get_sbits_long(&s->gb, s->curr_bps);
 458     } else if ((type >= 8) && (type <= 12)) {
 459         if (decode_subframe_fixed(s, channel, type & ~0x8) < 0)
 460             return -1;
 461     } else if (type >= 32) {
 462         if (decode_subframe_lpc(s, channel, (type & ~0x20)+1) < 0)
 463             return -1;
 464     } else {
 465         av_log(s->avctx, AV_LOG_ERROR, "invalid coding type\n");
 466         return -1;
 467     }
 468
 469     if (wasted) {
 470         int i;
 471         for (i = 0; i < s->blocksize; i++)
 472             s->decoded[channel][i] <<= wasted;
 473     }
 474
 475     return 0;
 476 }
 477
 478 static int decode_frame(FLACContext *s, int alloc_data_size)
 479 {
 480     int blocksize_code, sample_rate_code, sample_size_code, assignment, i, crc8;
 481     int decorrelation, bps, blocksize, samplerate;
 482
 483     blocksize_code = get_bits(&s->gb, 4);
 484
 485     sample_rate_code = get_bits(&s->gb, 4);
 486
 487     assignment = get_bits(&s->gb, 4); /* channel assignment */
 488     if (assignment < 8 && s->channels == assignment+1)
 489         decorrelation = INDEPENDENT;
 490     else if (assignment >=8 && assignment < 11 && s->channels == 2)
 491         decorrelation = LEFT_SIDE + assignment - 8;
 492     else {
 493         av_log(s->avctx, AV_LOG_ERROR, "unsupported channel assignment %d (channels=%d)\n",
 494                assignment, s->channels);
 495         return -1;
 496     }
 497
 498     sample_size_code = get_bits(&s->gb, 3);
 499     if (sample_size_code == 0)
 500         bps= s->bps;
 501     else if ((sample_size_code != 3) && (sample_size_code != 7))
 502         bps = sample_size_table[sample_size_code];
 503     else {
 504         av_log(s->avctx, AV_LOG_ERROR, "invalid sample size code (%d)\n",
 505                sample_size_code);
 506         return -1;
 507     }
 508     if (bps > 16) {
 509         s->avctx->sample_fmt = SAMPLE_FMT_S32;
 510         s->sample_shift = 32 - bps;
 511         s->is32 = 1;
 512     } else {
 513         s->avctx->sample_fmt = SAMPLE_FMT_S16;
 514         s->sample_shift = 16 - bps;
 515         s->is32 = 0;
 516     }
 517     s->bps = s->avctx->bits_per_raw_sample = bps;
 518
 519     if (get_bits1(&s->gb)) {
 520         av_log(s->avctx, AV_LOG_ERROR, "broken stream, invalid padding\n");
 521         return -1;
 522     }
 523
 524     if (get_utf8(&s->gb) < 0) {
 525         av_log(s->avctx, AV_LOG_ERROR, "utf8 fscked\n");
 526         return -1;
 527     }
 528
 529     if (blocksize_code == 0) {
 530         av_log(s->avctx, AV_LOG_ERROR, "reserved blocksize code: 0\n");
 531         return -1;
 532     } else if (blocksize_code == 6)
 533         blocksize = get_bits(&s->gb, 8)+1;
 534     else if (blocksize_code == 7)
 535         blocksize = get_bits(&s->gb, 16)+1;
 536     else
 537         blocksize = blocksize_table[blocksize_code];
 538
 539     if (blocksize > s->max_blocksize) {
 540         av_log(s->avctx, AV_LOG_ERROR, "blocksize %d > %d\n", blocksize,
 541                s->max_blocksize);
 542         return -1;
 543     }
 544
 545     if (blocksize * s->channels * sizeof(int16_t) > alloc_data_size)
 546         return -1;
 547
 548     if (sample_rate_code == 0)
 549         samplerate= s->samplerate;
 550     else if (sample_rate_code < 12)
 551         samplerate = sample_rate_table[sample_rate_code];
 552     else if (sample_rate_code == 12)
 553         samplerate = get_bits(&s->gb, 8) * 1000;
 554     else if (sample_rate_code == 13)
 555         samplerate = get_bits(&s->gb, 16);
 556     else if (sample_rate_code == 14)
 557         samplerate = get_bits(&s->gb, 16) * 10;
 558     else {
 559         av_log(s->avctx, AV_LOG_ERROR, "illegal sample rate code %d\n",
 560                sample_rate_code);
 561         return -1;
 562     }
 563
 564     skip_bits(&s->gb, 8);
 565     crc8 = av_crc(av_crc_get_table(AV_CRC_8_ATM), 0,
 566                   s->gb.buffer, get_bits_count(&s->gb)/8);
 567     if (crc8) {
 568         av_log(s->avctx, AV_LOG_ERROR, "header crc mismatch crc=%2X\n", crc8);
 569         return -1;
 570     }
 571
 572     s->blocksize    = blocksize;
 573     s->samplerate   = samplerate;
 574     s->bps          = bps;
 575     s->decorrelation= decorrelation;
 576
 577 //    dump_headers(s->avctx, (FLACStreaminfo *)s);
 578
 579     /* subframes */
 580     for (i = 0; i < s->channels; i++) {
 581         if (decode_subframe(s, i) < 0)
 582             return -1;
 583     }
 584
 585     align_get_bits(&s->gb);
 586
 587     /* frame footer */
 588     skip_bits(&s->gb, 16); /* data crc */
 589
 590     return 0;
 591 }
 592
 593 static int flac_decode_frame(AVCodecContext *avctx,
 594                             void *data, int *data_size,
 595                             const uint8_t *buf, int buf_size)
 596 {
 597     FLACContext *s = avctx->priv_data;
 598     int tmp = 0, i, j = 0, input_buf_size = 0;
 599     int16_t *samples_16 = data;
 600     int32_t *samples_32 = data;
 601     int alloc_data_size= *data_size;
 602
 603     *data_size=0;
 604
 605     if (s->max_framesize == 0) {
 606         s->max_framesize= FFMAX(4, buf_size); // should hopefully be enough for the first header
 607         s->bitstream= av_fast_realloc(s->bitstream, &s->allocated_bitstream_size, s->max_framesize);
 608     }
 609
 610     if (1 && s->max_framesize) { //FIXME truncated
 611         if (s->bitstream_size < 4 || AV_RL32(s->bitstream) != MKTAG('f','L','a','C'))
 612             buf_size= FFMIN(buf_size, s->max_framesize - FFMIN(s->bitstream_size, s->max_framesize));
 613         input_buf_size= buf_size;
 614
 615         if (s->bitstream_size + buf_size < buf_size || s->bitstream_index + s->bitstream_size + buf_size < s->bitstream_index)
 616             return -1;
 617
 618         if (s->allocated_bitstream_size < s->bitstream_size + buf_size)
 619             s->bitstream= av_fast_realloc(s->bitstream, &s->allocated_bitstream_size, s->bitstream_size + buf_size);
 620
 621         if (s->bitstream_index + s->bitstream_size + buf_size > s->allocated_bitstream_size) {
 622             memmove(s->bitstream, &s->bitstream[s->bitstream_index],
 623                     s->bitstream_size);
 624             s->bitstream_index=0;
 625         }
 626         memcpy(&s->bitstream[s->bitstream_index + s->bitstream_size],
 627                buf, buf_size);
 628         buf= &s->bitstream[s->bitstream_index];
 629         buf_size += s->bitstream_size;
 630         s->bitstream_size= buf_size;
 631
 632         if (buf_size < s->max_framesize && input_buf_size) {
 633             return input_buf_size;
 634         }
 635     }
 636
 637     init_get_bits(&s->gb, buf, buf_size*8);
 638
 639     if (metadata_parse(s))
 640         goto end;
 641
 642     tmp = show_bits(&s->gb, 16);
 643     if ((tmp & 0xFFFE) != 0xFFF8) {
 644         av_log(s->avctx, AV_LOG_ERROR, "FRAME HEADER not here\n");
 645         while (get_bits_count(&s->gb)/8+2 < buf_size && (show_bits(&s->gb, 16) & 0xFFFE) != 0xFFF8)
 646             skip_bits(&s->gb, 8);
 647         goto end; // we may not have enough bits left to decode a frame, so try next time
 648     }
 649     skip_bits(&s->gb, 16);
 650     if (decode_frame(s, alloc_data_size) < 0) {
 651         av_log(s->avctx, AV_LOG_ERROR, "decode_frame() failed\n");
 652         s->bitstream_size=0;
 653         s->bitstream_index=0;
 654         return -1;
 655     }
 656
 657 #define DECORRELATE(left, right)\
 658             assert(s->channels == 2);\
 659             for (i = 0; i < s->blocksize; i++) {\
 660                 int a= s->decoded[0][i];\
 661                 int b= s->decoded[1][i];\
 662                 if (s->is32) {\
 663                     *samples_32++ = (left)  << s->sample_shift;\
 664                     *samples_32++ = (right) << s->sample_shift;\
 665                 } else {\
 666                     *samples_16++ = (left)  << s->sample_shift;\
 667                     *samples_16++ = (right) << s->sample_shift;\
 668                 }\
 669             }\
 670             break;
 671
 672     switch (s->decorrelation) {
 673     case INDEPENDENT:
 674         for (j = 0; j < s->blocksize; j++) {
 675             for (i = 0; i < s->channels; i++) {
 676                 if (s->is32)
 677                     *samples_32++ = s->decoded[i][j] << s->sample_shift;
 678                 else
 679                     *samples_16++ = s->decoded[i][j] << s->sample_shift;
 680             }
 681         }
 682         break;
 683     case LEFT_SIDE:
 684         DECORRELATE(a,a-b)
 685     case RIGHT_SIDE:
 686         DECORRELATE(a+b,b)
 687     case MID_SIDE:
 688         DECORRELATE( (a-=b>>1) + b, a)
 689     }
 690
 691     *data_size = s->blocksize * s->channels * (s->is32 ? 4 : 2);
 692
 693 end:
 694     i= (get_bits_count(&s->gb)+7)/8;
 695     if (i > buf_size) {
 696         av_log(s->avctx, AV_LOG_ERROR, "overread: %d\n", i - buf_size);
 697         s->bitstream_size=0;
 698         s->bitstream_index=0;
 699         return -1;
 700     }
 701
 702     if (s->bitstream_size) {
 703         s->bitstream_index += i;
 704         s->bitstream_size  -= i;
 705         return input_buf_size;
 706     } else
 707         return i;
 708 }
 709
 710 static av_cold int flac_decode_close(AVCodecContext *avctx)
 711 {
 712     FLACContext *s = avctx->priv_data;
 713     int i;
 714
 715     for (i = 0; i < s->channels; i++) {
 716         av_freep(&s->decoded[i]);
 717     }
 718     av_freep(&s->bitstream);
 719
 720     return 0;
 721 }
 722
 723 static void flac_flush(AVCodecContext *avctx)
 724 {
 725     FLACContext *s = avctx->priv_data;
 726
 727     s->bitstream_size=
 728     s->bitstream_index= 0;
 729 }
 730
 731 AVCodec flac_decoder = {
 732     "flac",
 733     CODEC_TYPE_AUDIO,
 734     CODEC_ID_FLAC,
 735     sizeof(FLACContext),
 736     flac_decode_init,
 737     NULL,
 738     flac_decode_close,
 739     flac_decode_frame,
 740     CODEC_CAP_DELAY,
 741     .flush= flac_flush,
 742     .long_name= NULL_IF_CONFIG_SMALL("FLAC (Free Lossless Audio Codec)"),
 743 };