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 "bytestream.h"
  43 #include "golomb.h"
  44 #include "flac.h"
  45
  46 #undef NDEBUG
  47 #include <assert.h>
  48
  49 #define MAX_CHANNELS 8
  50 #define MAX_BLOCKSIZE 65535
  51
  52 enum decorrelation_type {
  53     INDEPENDENT,
  54     LEFT_SIDE,
  55     RIGHT_SIDE,
  56     MID_SIDE,
  57 };
  58
  59 typedef struct FLACContext {
  60     FLACSTREAMINFO
  61
  62     AVCodecContext *avctx;                  ///< parent AVCodecContext
  63     GetBitContext gb;                       ///< GetBitContext initialized to start at the current frame
  64
  65     int blocksize;                          ///< number of samples in the current frame
  66     int curr_bps;                           ///< bps for current subframe, adjusted for channel correlation and wasted bits
  67     int sample_shift;                       ///< shift required to make output samples 16-bit or 32-bit
  68     int is32;                               ///< flag to indicate if output should be 32-bit instead of 16-bit
  69     enum decorrelation_type decorrelation;  ///< channel decorrelation type in the current frame
  70     int got_streaminfo;                     ///< indicates if the STREAMINFO has been read
  71
  72     int32_t *decoded[MAX_CHANNELS];         ///< decoded samples
  73     uint8_t *bitstream;
  74     unsigned int bitstream_size;
  75     unsigned int bitstream_index;
  76     unsigned int allocated_bitstream_size;
  77 } FLACContext;
  78
  79 static const int sample_rate_table[] =
  80 { 0,
  81   88200, 176400, 192000,
  82   8000, 16000, 22050, 24000, 32000, 44100, 48000, 96000,
  83   0, 0, 0, 0 };
  84
  85 static const int sample_size_table[] =
  86 { 0, 8, 12, 0, 16, 20, 24, 0 };
  87
  88 static const int blocksize_table[] = {
  89      0,    192, 576<<0, 576<<1, 576<<2, 576<<3,      0,      0,
  90 256<<0, 256<<1, 256<<2, 256<<3, 256<<4, 256<<5, 256<<6, 256<<7
  91 };
  92
  93 static int64_t get_utf8(GetBitContext *gb)
  94 {
  95     int64_t val;
  96     GET_UTF8(val, get_bits(gb, 8), return -1;)
  97     return val;
  98 }
  99
 100 static void allocate_buffers(FLACContext *s);
 101
 102 int ff_flac_is_extradata_valid(AVCodecContext *avctx,
 103                                enum FLACExtradataFormat *format,
 104                                uint8_t **streaminfo_start)
 105 {
 106     if (!avctx->extradata || avctx->extradata_size < FLAC_STREAMINFO_SIZE) {
 107         av_log(avctx, AV_LOG_ERROR, "extradata NULL or too small.\n");
 108         return 0;
 109     }
 110     if (AV_RL32(avctx->extradata) != MKTAG('f','L','a','C')) {
 111         /* extradata contains STREAMINFO only */
 112         if (avctx->extradata_size != FLAC_STREAMINFO_SIZE) {
 113             av_log(avctx, AV_LOG_WARNING, "extradata contains %d bytes too many.\n",
 114                    FLAC_STREAMINFO_SIZE-avctx->extradata_size);
 115         }
 116         *format = FLAC_EXTRADATA_FORMAT_STREAMINFO;
 117         *streaminfo_start = avctx->extradata;
 118     } else {
 119         if (avctx->extradata_size < 8+FLAC_STREAMINFO_SIZE) {
 120             av_log(avctx, AV_LOG_ERROR, "extradata too small.\n");
 121             return 0;
 122         }
 123         *format = FLAC_EXTRADATA_FORMAT_FULL_HEADER;
 124         *streaminfo_start = &avctx->extradata[8];
 125     }
 126     return 1;
 127 }
 128
 129 static av_cold int flac_decode_init(AVCodecContext *avctx)
 130 {
 131     enum FLACExtradataFormat format;
 132     uint8_t *streaminfo;
 133     FLACContext *s = avctx->priv_data;
 134     s->avctx = avctx;
 135
 136     avctx->sample_fmt = SAMPLE_FMT_S16;
 137
 138     /* for now, the raw FLAC header is allowed to be passed to the decoder as
 139        frame data instead of extradata. */
 140     if (!avctx->extradata)
 141         return 0;
 142
 143     if (!ff_flac_is_extradata_valid(avctx, &format, &streaminfo))
 144         return -1;
 145
 146     /* initialize based on the demuxer-supplied streamdata header */
 147     ff_flac_parse_streaminfo(avctx, (FLACStreaminfo *)s, streaminfo);
 148     allocate_buffers(s);
 149     s->got_streaminfo = 1;
 150
 151     return 0;
 152 }
 153
 154 static void dump_headers(AVCodecContext *avctx, FLACStreaminfo *s)
 155 {
 156     av_log(avctx, AV_LOG_DEBUG, "  Max Blocksize: %d\n", s->max_blocksize);
 157     av_log(avctx, AV_LOG_DEBUG, "  Max Framesize: %d\n", s->max_framesize);
 158     av_log(avctx, AV_LOG_DEBUG, "  Samplerate: %d\n", s->samplerate);
 159     av_log(avctx, AV_LOG_DEBUG, "  Channels: %d\n", s->channels);
 160     av_log(avctx, AV_LOG_DEBUG, "  Bits: %d\n", s->bps);
 161 }
 162
 163 static void allocate_buffers(FLACContext *s)
 164 {
 165     int i;
 166
 167     assert(s->max_blocksize);
 168
 169     if (s->max_framesize == 0 && s->max_blocksize) {
 170         // FIXME header overhead
 171         s->max_framesize= (s->channels * s->bps * s->max_blocksize + 7)/ 8;
 172     }
 173
 174     for (i = 0; i < s->channels; i++) {
 175         s->decoded[i] = av_realloc(s->decoded[i],
 176                                    sizeof(int32_t)*s->max_blocksize);
 177     }
 178
 179     if (s->allocated_bitstream_size < s->max_framesize)
 180         s->bitstream= av_fast_realloc(s->bitstream,
 181                                       &s->allocated_bitstream_size,
 182                                       s->max_framesize);
 183 }
 184
 185 void ff_flac_parse_streaminfo(AVCodecContext *avctx, struct FLACStreaminfo *s,
 186                               const uint8_t *buffer)
 187 {
 188     GetBitContext gb;
 189     init_get_bits(&gb, buffer, FLAC_STREAMINFO_SIZE*8);
 190
 191     skip_bits(&gb, 16); /* skip min blocksize */
 192     s->max_blocksize = get_bits(&gb, 16);
 193     if (s->max_blocksize < 16) {
 194         av_log(avctx, AV_LOG_WARNING, "invalid max blocksize: %d\n",
 195                s->max_blocksize);
 196         s->max_blocksize = 16;
 197     }
 198
 199     skip_bits(&gb, 24); /* skip min frame size */
 200     s->max_framesize = get_bits_long(&gb, 24);
 201
 202     s->samplerate = get_bits_long(&gb, 20);
 203     s->channels = get_bits(&gb, 3) + 1;
 204     s->bps = get_bits(&gb, 5) + 1;
 205
 206     avctx->channels = s->channels;
 207     avctx->sample_rate = s->samplerate;
 208     avctx->bits_per_raw_sample = s->bps;
 209     if (s->bps > 16)
 210         avctx->sample_fmt = SAMPLE_FMT_S32;
 211     else
 212         avctx->sample_fmt = SAMPLE_FMT_S16;
 213
 214     s->samples  = get_bits_long(&gb, 32) << 4;
 215     s->samples |= get_bits(&gb, 4);
 216
 217     skip_bits_long(&gb, 64); /* md5 sum */
 218     skip_bits_long(&gb, 64); /* md5 sum */
 219
 220     dump_headers(avctx, s);
 221 }
 222
 223 /**
 224  * Parse the STREAMINFO from an inline header.
 225  * @param s the flac decoding context
 226  * @param buf input buffer, starting with the "fLaC" marker
 227  * @param buf_size buffer size
 228  * @return non-zero if metadata is invalid
 229  */
 230 static int parse_streaminfo(FLACContext *s, const uint8_t *buf, int buf_size)
 231 {
 232     int metadata_type, metadata_size;
 233
 234     if (buf_size < FLAC_STREAMINFO_SIZE+8) {
 235         /* need more data */
 236         return 0;
 237     }
 238     buf += 4;
 239     metadata_type = bytestream_get_byte(&buf) & 0x7F;
 240     metadata_size = bytestream_get_be24(&buf);
 241     if (metadata_type != FLAC_METADATA_TYPE_STREAMINFO ||
 242         metadata_size != FLAC_STREAMINFO_SIZE) {
 243         return AVERROR_INVALIDDATA;
 244     }
 245     ff_flac_parse_streaminfo(s->avctx, (FLACStreaminfo *)s, buf);
 246     allocate_buffers(s);
 247     s->got_streaminfo = 1;
 248
 249     return 0;
 250 }
 251
 252 /**
 253  * Determine the size of an inline header.
 254  * @param buf input buffer, starting with the "fLaC" marker
 255  * @param buf_size buffer size
 256  * @return number of bytes in the header, or 0 if more data is needed
 257  */
 258 static int get_metadata_size(const uint8_t *buf, int buf_size)
 259 {
 260     int metadata_last, metadata_size;
 261     const uint8_t *buf_end = buf + buf_size;
 262
 263     buf += 4;
 264     do {
 265         metadata_last = bytestream_get_byte(&buf) & 0x80;
 266         metadata_size = bytestream_get_be24(&buf);
 267         if (buf + metadata_size > buf_end) {
 268             /* need more data in order to read the complete header */
 269             return 0;
 270         }
 271         buf += metadata_size;
 272     } while (!metadata_last);
 273
 274     return buf_size - (buf_end - buf);
 275 }
 276
 277 static int decode_residuals(FLACContext *s, int channel, int pred_order)
 278 {
 279     int i, tmp, partition, method_type, rice_order;
 280     int sample = 0, samples;
 281
 282     method_type = get_bits(&s->gb, 2);
 283     if (method_type > 1) {
 284         av_log(s->avctx, AV_LOG_ERROR, "illegal residual coding method %d\n",
 285                method_type);
 286         return -1;
 287     }
 288
 289     rice_order = get_bits(&s->gb, 4);
 290
 291     samples= s->blocksize >> rice_order;
 292     if (pred_order > samples) {
 293         av_log(s->avctx, AV_LOG_ERROR, "invalid predictor order: %i > %i\n",
 294                pred_order, samples);
 295         return -1;
 296     }
 297
 298     sample=
 299     i= pred_order;
 300     for (partition = 0; partition < (1 << rice_order); partition++) {
 301         tmp = get_bits(&s->gb, method_type == 0 ? 4 : 5);
 302         if (tmp == (method_type == 0 ? 15 : 31)) {
 303             tmp = get_bits(&s->gb, 5);
 304             for (; i < samples; i++, sample++)
 305                 s->decoded[channel][sample] = get_sbits_long(&s->gb, tmp);
 306         } else {
 307             for (; i < samples; i++, sample++) {
 308                 s->decoded[channel][sample] = get_sr_golomb_flac(&s->gb, tmp, INT_MAX, 0);
 309             }
 310         }
 311         i= 0;
 312     }
 313
 314     return 0;
 315 }
 316
 317 static int decode_subframe_fixed(FLACContext *s, int channel, int pred_order)
 318 {
 319     const int blocksize = s->blocksize;
 320     int32_t *decoded = s->decoded[channel];
 321     int av_uninit(a), av_uninit(b), av_uninit(c), av_uninit(d), i;
 322
 323     /* warm up samples */
 324     for (i = 0; i < pred_order; i++) {
 325         decoded[i] = get_sbits_long(&s->gb, s->curr_bps);
 326     }
 327
 328     if (decode_residuals(s, channel, pred_order) < 0)
 329         return -1;
 330
 331     if (pred_order > 0)
 332         a = decoded[pred_order-1];
 333     if (pred_order > 1)
 334         b = a - decoded[pred_order-2];
 335     if (pred_order > 2)
 336         c = b - decoded[pred_order-2] + decoded[pred_order-3];
 337     if (pred_order > 3)
 338         d = c - decoded[pred_order-2] + 2*decoded[pred_order-3] - decoded[pred_order-4];
 339
 340     switch (pred_order) {
 341     case 0:
 342         break;
 343     case 1:
 344         for (i = pred_order; i < blocksize; i++)
 345             decoded[i] = a += decoded[i];
 346         break;
 347     case 2:
 348         for (i = pred_order; i < blocksize; i++)
 349             decoded[i] = a += b += decoded[i];
 350         break;
 351     case 3:
 352         for (i = pred_order; i < blocksize; i++)
 353             decoded[i] = a += b += c += decoded[i];
 354         break;
 355     case 4:
 356         for (i = pred_order; i < blocksize; i++)
 357             decoded[i] = a += b += c += d += decoded[i];
 358         break;
 359     default:
 360         av_log(s->avctx, AV_LOG_ERROR, "illegal pred order %d\n", pred_order);
 361         return -1;
 362     }
 363
 364     return 0;
 365 }
 366
 367 static int decode_subframe_lpc(FLACContext *s, int channel, int pred_order)
 368 {
 369     int i, j;
 370     int coeff_prec, qlevel;
 371     int coeffs[pred_order];
 372     int32_t *decoded = s->decoded[channel];
 373
 374     /* warm up samples */
 375     for (i = 0; i < pred_order; i++) {
 376         decoded[i] = get_sbits_long(&s->gb, s->curr_bps);
 377     }
 378
 379     coeff_prec = get_bits(&s->gb, 4) + 1;
 380     if (coeff_prec == 16) {
 381         av_log(s->avctx, AV_LOG_ERROR, "invalid coeff precision\n");
 382         return -1;
 383     }
 384     qlevel = get_sbits(&s->gb, 5);
 385     if (qlevel < 0) {
 386         av_log(s->avctx, AV_LOG_ERROR, "qlevel %d not supported, maybe buggy stream\n",
 387                qlevel);
 388         return -1;
 389     }
 390
 391     for (i = 0; i < pred_order; i++) {
 392         coeffs[i] = get_sbits(&s->gb, coeff_prec);
 393     }
 394
 395     if (decode_residuals(s, channel, pred_order) < 0)
 396         return -1;
 397
 398     if (s->bps > 16) {
 399         int64_t sum;
 400         for (i = pred_order; i < s->blocksize; i++) {
 401             sum = 0;
 402             for (j = 0; j < pred_order; j++)
 403                 sum += (int64_t)coeffs[j] * decoded[i-j-1];
 404             decoded[i] += sum >> qlevel;
 405         }
 406     } else {
 407         for (i = pred_order; i < s->blocksize-1; i += 2) {
 408             int c;
 409             int d = decoded[i-pred_order];
 410             int s0 = 0, s1 = 0;
 411             for (j = pred_order-1; j > 0; j--) {
 412                 c = coeffs[j];
 413                 s0 += c*d;
 414                 d = decoded[i-j];
 415                 s1 += c*d;
 416             }
 417             c = coeffs[0];
 418             s0 += c*d;
 419             d = decoded[i] += s0 >> qlevel;
 420             s1 += c*d;
 421             decoded[i+1] += s1 >> qlevel;
 422         }
 423         if (i < s->blocksize) {
 424             int sum = 0;
 425             for (j = 0; j < pred_order; j++)
 426                 sum += coeffs[j] * decoded[i-j-1];
 427             decoded[i] += sum >> qlevel;
 428         }
 429     }
 430
 431     return 0;
 432 }
 433
 434 static inline int decode_subframe(FLACContext *s, int channel)
 435 {
 436     int type, wasted = 0;
 437     int i, tmp;
 438
 439     s->curr_bps = s->bps;
 440     if (channel == 0) {
 441         if (s->decorrelation == RIGHT_SIDE)
 442             s->curr_bps++;
 443     } else {
 444         if (s->decorrelation == LEFT_SIDE || s->decorrelation == MID_SIDE)
 445             s->curr_bps++;
 446     }
 447
 448     if (get_bits1(&s->gb)) {
 449         av_log(s->avctx, AV_LOG_ERROR, "invalid subframe padding\n");
 450         return -1;
 451     }
 452     type = get_bits(&s->gb, 6);
 453
 454     if (get_bits1(&s->gb)) {
 455         wasted = 1;
 456         while (!get_bits1(&s->gb))
 457             wasted++;
 458         s->curr_bps -= wasted;
 459     }
 460     if (s->curr_bps > 32) {
 461         ff_log_missing_feature(s->avctx, "decorrelated bit depth > 32", 0);
 462         return -1;
 463     }
 464
 465 //FIXME use av_log2 for types
 466     if (type == 0) {
 467         tmp = get_sbits_long(&s->gb, s->curr_bps);
 468         for (i = 0; i < s->blocksize; i++)
 469             s->decoded[channel][i] = tmp;
 470     } else if (type == 1) {
 471         for (i = 0; i < s->blocksize; i++)
 472             s->decoded[channel][i] = get_sbits_long(&s->gb, s->curr_bps);
 473     } else if ((type >= 8) && (type <= 12)) {
 474         if (decode_subframe_fixed(s, channel, type & ~0x8) < 0)
 475             return -1;
 476     } else if (type >= 32) {
 477         if (decode_subframe_lpc(s, channel, (type & ~0x20)+1) < 0)
 478             return -1;
 479     } else {
 480         av_log(s->avctx, AV_LOG_ERROR, "invalid coding type\n");
 481         return -1;
 482     }
 483
 484     if (wasted) {
 485         int i;
 486         for (i = 0; i < s->blocksize; i++)
 487             s->decoded[channel][i] <<= wasted;
 488     }
 489
 490     return 0;
 491 }
 492
 493 static int decode_frame(FLACContext *s, int alloc_data_size)
 494 {
 495     int blocksize_code, sample_rate_code, sample_size_code, assignment, i, crc8;
 496     int decorrelation, bps, blocksize, samplerate;
 497
 498     blocksize_code = get_bits(&s->gb, 4);
 499
 500     sample_rate_code = get_bits(&s->gb, 4);
 501
 502     assignment = get_bits(&s->gb, 4); /* channel assignment */
 503     if (assignment < 8 && s->channels == assignment+1)
 504         decorrelation = INDEPENDENT;
 505     else if (assignment >=8 && assignment < 11 && s->channels == 2)
 506         decorrelation = LEFT_SIDE + assignment - 8;
 507     else {
 508         av_log(s->avctx, AV_LOG_ERROR, "unsupported channel assignment %d (channels=%d)\n",
 509                assignment, s->channels);
 510         return -1;
 511     }
 512
 513     sample_size_code = get_bits(&s->gb, 3);
 514     if (sample_size_code == 0)
 515         bps= s->bps;
 516     else if ((sample_size_code != 3) && (sample_size_code != 7))
 517         bps = sample_size_table[sample_size_code];
 518     else {
 519         av_log(s->avctx, AV_LOG_ERROR, "invalid sample size code (%d)\n",
 520                sample_size_code);
 521         return -1;
 522     }
 523     if (bps > 16) {
 524         s->avctx->sample_fmt = SAMPLE_FMT_S32;
 525         s->sample_shift = 32 - bps;
 526         s->is32 = 1;
 527     } else {
 528         s->avctx->sample_fmt = SAMPLE_FMT_S16;
 529         s->sample_shift = 16 - bps;
 530         s->is32 = 0;
 531     }
 532     s->bps = s->avctx->bits_per_raw_sample = bps;
 533
 534     if (get_bits1(&s->gb)) {
 535         av_log(s->avctx, AV_LOG_ERROR, "broken stream, invalid padding\n");
 536         return -1;
 537     }
 538
 539     if (get_utf8(&s->gb) < 0) {
 540         av_log(s->avctx, AV_LOG_ERROR, "utf8 fscked\n");
 541         return -1;
 542     }
 543
 544     if (blocksize_code == 0) {
 545         av_log(s->avctx, AV_LOG_ERROR, "reserved blocksize code: 0\n");
 546         return -1;
 547     } else if (blocksize_code == 6)
 548         blocksize = get_bits(&s->gb, 8)+1;
 549     else if (blocksize_code == 7)
 550         blocksize = get_bits(&s->gb, 16)+1;
 551     else
 552         blocksize = blocksize_table[blocksize_code];
 553
 554     if (blocksize > s->max_blocksize) {
 555         av_log(s->avctx, AV_LOG_ERROR, "blocksize %d > %d\n", blocksize,
 556                s->max_blocksize);
 557         return -1;
 558     }
 559
 560     if (blocksize * s->channels * (s->is32 ? 4 : 2) > alloc_data_size)
 561         return -1;
 562
 563     if (sample_rate_code == 0)
 564         samplerate= s->samplerate;
 565     else if (sample_rate_code < 12)
 566         samplerate = sample_rate_table[sample_rate_code];
 567     else if (sample_rate_code == 12)
 568         samplerate = get_bits(&s->gb, 8) * 1000;
 569     else if (sample_rate_code == 13)
 570         samplerate = get_bits(&s->gb, 16);
 571     else if (sample_rate_code == 14)
 572         samplerate = get_bits(&s->gb, 16) * 10;
 573     else {
 574         av_log(s->avctx, AV_LOG_ERROR, "illegal sample rate code %d\n",
 575                sample_rate_code);
 576         return -1;
 577     }
 578
 579     skip_bits(&s->gb, 8);
 580     crc8 = av_crc(av_crc_get_table(AV_CRC_8_ATM), 0,
 581                   s->gb.buffer, get_bits_count(&s->gb)/8);
 582     if (crc8) {
 583         av_log(s->avctx, AV_LOG_ERROR, "header crc mismatch crc=%2X\n", crc8);
 584         return -1;
 585     }
 586
 587     s->blocksize    = blocksize;
 588     s->samplerate   = samplerate;
 589     s->bps          = bps;
 590     s->decorrelation= decorrelation;
 591
 592 //    dump_headers(s->avctx, (FLACStreaminfo *)s);
 593
 594     /* subframes */
 595     for (i = 0; i < s->channels; i++) {
 596         if (decode_subframe(s, i) < 0)
 597             return -1;
 598     }
 599
 600     align_get_bits(&s->gb);
 601
 602     /* frame footer */
 603     skip_bits(&s->gb, 16); /* data crc */
 604
 605     return 0;
 606 }
 607
 608 static int flac_decode_frame(AVCodecContext *avctx,
 609                             void *data, int *data_size,
 610                             const uint8_t *buf, int buf_size)
 611 {
 612     FLACContext *s = avctx->priv_data;
 613     int i, j = 0, input_buf_size = 0, bytes_read = 0;
 614     int16_t *samples_16 = data;
 615     int32_t *samples_32 = data;
 616     int alloc_data_size= *data_size;
 617
 618     *data_size=0;
 619
 620     if (s->max_framesize == 0) {
 621         s->max_framesize= FFMAX(4, buf_size); // should hopefully be enough for the first header
 622         s->bitstream= av_fast_realloc(s->bitstream, &s->allocated_bitstream_size, s->max_framesize);
 623     }
 624
 625     if (1 && s->max_framesize) { //FIXME truncated
 626         if (s->bitstream_size < 4 || AV_RL32(s->bitstream) != MKTAG('f','L','a','C'))
 627             buf_size= FFMIN(buf_size, s->max_framesize - FFMIN(s->bitstream_size, s->max_framesize));
 628         input_buf_size= buf_size;
 629
 630         if (s->bitstream_size + buf_size < buf_size || s->bitstream_index + s->bitstream_size + buf_size < s->bitstream_index)
 631             return -1;
 632
 633         if (s->allocated_bitstream_size < s->bitstream_size + buf_size)
 634             s->bitstream= av_fast_realloc(s->bitstream, &s->allocated_bitstream_size, s->bitstream_size + buf_size);
 635
 636         if (s->bitstream_index + s->bitstream_size + buf_size > s->allocated_bitstream_size) {
 637             memmove(s->bitstream, &s->bitstream[s->bitstream_index],
 638                     s->bitstream_size);
 639             s->bitstream_index=0;
 640         }
 641         memcpy(&s->bitstream[s->bitstream_index + s->bitstream_size],
 642                buf, buf_size);
 643         buf= &s->bitstream[s->bitstream_index];
 644         buf_size += s->bitstream_size;
 645         s->bitstream_size= buf_size;
 646
 647         if (buf_size < s->max_framesize && input_buf_size) {
 648             return input_buf_size;
 649         }
 650     }
 651
 652     /* check that there is at least the smallest decodable amount of data.
 653        this amount corresponds to the smallest valid FLAC frame possible. */
 654     if (buf_size < 11)
 655         goto end;
 656
 657     /* check for inline header */
 658     if (AV_RB32(buf) == MKBETAG('f','L','a','C')) {
 659         if (!s->got_streaminfo && parse_streaminfo(s, buf, buf_size)) {
 660             av_log(s->avctx, AV_LOG_ERROR, "invalid header\n");
 661             return -1;
 662         }
 663         bytes_read = get_metadata_size(buf, buf_size);
 664         goto end;
 665     }
 666
 667     /* check for frame sync code and resync stream if necessary */
 668     if ((AV_RB16(buf) & 0xFFFE) != 0xFFF8) {
 669         const uint8_t *buf_end = buf + buf_size;
 670         av_log(s->avctx, AV_LOG_ERROR, "FRAME HEADER not here\n");
 671         while (buf+2 < buf_end && (AV_RB16(buf) & 0xFFFE) != 0xFFF8)
 672             buf++;
 673         bytes_read = buf_size - (buf_end - buf);
 674         goto end; // we may not have enough bits left to decode a frame, so try next time
 675     }
 676
 677     /* decode frame */
 678     init_get_bits(&s->gb, buf, buf_size*8);
 679     skip_bits(&s->gb, 16);
 680     if (decode_frame(s, alloc_data_size) < 0) {
 681         av_log(s->avctx, AV_LOG_ERROR, "decode_frame() failed\n");
 682         s->bitstream_size=0;
 683         s->bitstream_index=0;
 684         return -1;
 685     }
 686     *data_size = s->blocksize * s->channels * (s->is32 ? 4 : 2);
 687     bytes_read = (get_bits_count(&s->gb)+7)/8;
 688
 689 #define DECORRELATE(left, right)\
 690             assert(s->channels == 2);\
 691             for (i = 0; i < s->blocksize; i++) {\
 692                 int a= s->decoded[0][i];\
 693                 int b= s->decoded[1][i];\
 694                 if (s->is32) {\
 695                     *samples_32++ = (left)  << s->sample_shift;\
 696                     *samples_32++ = (right) << s->sample_shift;\
 697                 } else {\
 698                     *samples_16++ = (left)  << s->sample_shift;\
 699                     *samples_16++ = (right) << s->sample_shift;\
 700                 }\
 701             }\
 702             break;
 703
 704     switch (s->decorrelation) {
 705     case INDEPENDENT:
 706         for (j = 0; j < s->blocksize; j++) {
 707             for (i = 0; i < s->channels; i++) {
 708                 if (s->is32)
 709                     *samples_32++ = s->decoded[i][j] << s->sample_shift;
 710                 else
 711                     *samples_16++ = s->decoded[i][j] << s->sample_shift;
 712             }
 713         }
 714         break;
 715     case LEFT_SIDE:
 716         DECORRELATE(a,a-b)
 717     case RIGHT_SIDE:
 718         DECORRELATE(a+b,b)
 719     case MID_SIDE:
 720         DECORRELATE( (a-=b>>1) + b, a)
 721     }
 722
 723 end:
 724     if (bytes_read > buf_size) {
 725         av_log(s->avctx, AV_LOG_ERROR, "overread: %d\n", bytes_read - buf_size);
 726         s->bitstream_size=0;
 727         s->bitstream_index=0;
 728         return -1;
 729     }
 730
 731     if (s->bitstream_size) {
 732         s->bitstream_index += bytes_read;
 733         s->bitstream_size  -= bytes_read;
 734         return input_buf_size;
 735     } else
 736         return bytes_read;
 737 }
 738
 739 static av_cold int flac_decode_close(AVCodecContext *avctx)
 740 {
 741     FLACContext *s = avctx->priv_data;
 742     int i;
 743
 744     for (i = 0; i < s->channels; i++) {
 745         av_freep(&s->decoded[i]);
 746     }
 747     av_freep(&s->bitstream);
 748
 749     return 0;
 750 }
 751
 752 static void flac_flush(AVCodecContext *avctx)
 753 {
 754     FLACContext *s = avctx->priv_data;
 755
 756     s->bitstream_size=
 757     s->bitstream_index= 0;
 758 }
 759
 760 AVCodec flac_decoder = {
 761     "flac",
 762     CODEC_TYPE_AUDIO,
 763     CODEC_ID_FLAC,
 764     sizeof(FLACContext),
 765     flac_decode_init,
 766     NULL,
 767     flac_decode_close,
 768     flac_decode_frame,
 769     CODEC_CAP_DELAY,
 770     .flush= flac_flush,
 771     .long_name= NULL_IF_CONFIG_SMALL("FLAC (Free Lossless Audio Codec)"),
 772 };