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 #include "flacdata.h"
  46
  47 #undef NDEBUG
  48 #include <assert.h>
  49
  50 typedef struct FLACContext {
  51     FLACSTREAMINFO
  52
  53     AVCodecContext *avctx;                  ///< parent AVCodecContext
  54     GetBitContext gb;                       ///< GetBitContext initialized to start at the current frame
  55
  56     int blocksize;                          ///< number of samples in the current frame
  57     int curr_bps;                           ///< bps for current subframe, adjusted for channel correlation and wasted bits
  58     int sample_shift;                       ///< shift required to make output samples 16-bit or 32-bit
  59     int is32;                               ///< flag to indicate if output should be 32-bit instead of 16-bit
  60     int ch_mode;                            ///< channel decorrelation type in the current frame
  61     int got_streaminfo;                     ///< indicates if the STREAMINFO has been read
  62
  63     int32_t *decoded[FLAC_MAX_CHANNELS];    ///< decoded samples
  64     uint8_t *bitstream;
  65     unsigned int bitstream_size;
  66     unsigned int bitstream_index;
  67     unsigned int allocated_bitstream_size;
  68 } FLACContext;
  69
  70 static const int sample_size_table[] =
  71 { 0, 8, 12, 0, 16, 20, 24, 0 };
  72
  73 static int64_t get_utf8(GetBitContext *gb)
  74 {
  75     int64_t val;
  76     GET_UTF8(val, get_bits(gb, 8), return -1;)
  77     return val;
  78 }
  79
  80 static void allocate_buffers(FLACContext *s);
  81
  82 int ff_flac_is_extradata_valid(AVCodecContext *avctx,
  83                                enum FLACExtradataFormat *format,
  84                                uint8_t **streaminfo_start)
  85 {
  86     if (!avctx->extradata || avctx->extradata_size < FLAC_STREAMINFO_SIZE) {
  87         av_log(avctx, AV_LOG_ERROR, "extradata NULL or too small.\n");
  88         return 0;
  89     }
  90     if (AV_RL32(avctx->extradata) != MKTAG('f','L','a','C')) {
  91         /* extradata contains STREAMINFO only */
  92         if (avctx->extradata_size != FLAC_STREAMINFO_SIZE) {
  93             av_log(avctx, AV_LOG_WARNING, "extradata contains %d bytes too many.\n",
  94                    FLAC_STREAMINFO_SIZE-avctx->extradata_size);
  95         }
  96         *format = FLAC_EXTRADATA_FORMAT_STREAMINFO;
  97         *streaminfo_start = avctx->extradata;
  98     } else {
  99         if (avctx->extradata_size < 8+FLAC_STREAMINFO_SIZE) {
 100             av_log(avctx, AV_LOG_ERROR, "extradata too small.\n");
 101             return 0;
 102         }
 103         *format = FLAC_EXTRADATA_FORMAT_FULL_HEADER;
 104         *streaminfo_start = &avctx->extradata[8];
 105     }
 106     return 1;
 107 }
 108
 109 static av_cold int flac_decode_init(AVCodecContext *avctx)
 110 {
 111     enum FLACExtradataFormat format;
 112     uint8_t *streaminfo;
 113     FLACContext *s = avctx->priv_data;
 114     s->avctx = avctx;
 115
 116     avctx->sample_fmt = SAMPLE_FMT_S16;
 117
 118     /* for now, the raw FLAC header is allowed to be passed to the decoder as
 119        frame data instead of extradata. */
 120     if (!avctx->extradata)
 121         return 0;
 122
 123     if (!ff_flac_is_extradata_valid(avctx, &format, &streaminfo))
 124         return -1;
 125
 126     /* initialize based on the demuxer-supplied streamdata header */
 127     ff_flac_parse_streaminfo(avctx, (FLACStreaminfo *)s, streaminfo);
 128     allocate_buffers(s);
 129     s->got_streaminfo = 1;
 130
 131     return 0;
 132 }
 133
 134 static void dump_headers(AVCodecContext *avctx, FLACStreaminfo *s)
 135 {
 136     av_log(avctx, AV_LOG_DEBUG, "  Max Blocksize: %d\n", s->max_blocksize);
 137     av_log(avctx, AV_LOG_DEBUG, "  Max Framesize: %d\n", s->max_framesize);
 138     av_log(avctx, AV_LOG_DEBUG, "  Samplerate: %d\n", s->samplerate);
 139     av_log(avctx, AV_LOG_DEBUG, "  Channels: %d\n", s->channels);
 140     av_log(avctx, AV_LOG_DEBUG, "  Bits: %d\n", s->bps);
 141 }
 142
 143 static void allocate_buffers(FLACContext *s)
 144 {
 145     int i;
 146
 147     assert(s->max_blocksize);
 148
 149     if (s->max_framesize == 0 && s->max_blocksize) {
 150         s->max_framesize = ff_flac_get_max_frame_size(s->max_blocksize,
 151                                                       s->channels, s->bps);
 152     }
 153
 154     for (i = 0; i < s->channels; i++) {
 155         s->decoded[i] = av_realloc(s->decoded[i],
 156                                    sizeof(int32_t)*s->max_blocksize);
 157     }
 158
 159     if (s->allocated_bitstream_size < s->max_framesize)
 160         s->bitstream= av_fast_realloc(s->bitstream,
 161                                       &s->allocated_bitstream_size,
 162                                       s->max_framesize);
 163 }
 164
 165 void ff_flac_parse_streaminfo(AVCodecContext *avctx, struct FLACStreaminfo *s,
 166                               const uint8_t *buffer)
 167 {
 168     GetBitContext gb;
 169     init_get_bits(&gb, buffer, FLAC_STREAMINFO_SIZE*8);
 170
 171     skip_bits(&gb, 16); /* skip min blocksize */
 172     s->max_blocksize = get_bits(&gb, 16);
 173     if (s->max_blocksize < FLAC_MIN_BLOCKSIZE) {
 174         av_log(avctx, AV_LOG_WARNING, "invalid max blocksize: %d\n",
 175                s->max_blocksize);
 176         s->max_blocksize = 16;
 177     }
 178
 179     skip_bits(&gb, 24); /* skip min frame size */
 180     s->max_framesize = get_bits_long(&gb, 24);
 181
 182     s->samplerate = get_bits_long(&gb, 20);
 183     s->channels = get_bits(&gb, 3) + 1;
 184     s->bps = get_bits(&gb, 5) + 1;
 185
 186     avctx->channels = s->channels;
 187     avctx->sample_rate = s->samplerate;
 188     avctx->bits_per_raw_sample = s->bps;
 189     if (s->bps > 16)
 190         avctx->sample_fmt = SAMPLE_FMT_S32;
 191     else
 192         avctx->sample_fmt = SAMPLE_FMT_S16;
 193
 194     s->samples  = get_bits_long(&gb, 32) << 4;
 195     s->samples |= get_bits(&gb, 4);
 196
 197     skip_bits_long(&gb, 64); /* md5 sum */
 198     skip_bits_long(&gb, 64); /* md5 sum */
 199
 200     dump_headers(avctx, s);
 201 }
 202
 203 void ff_flac_parse_block_header(const uint8_t *block_header,
 204                                 int *last, int *type, int *size)
 205 {
 206     int tmp = bytestream_get_byte(&block_header);
 207     if (last)
 208         *last = tmp & 0x80;
 209     if (type)
 210         *type = tmp & 0x7F;
 211     if (size)
 212         *size = bytestream_get_be24(&block_header);
 213 }
 214
 215 /**
 216  * Parse the STREAMINFO from an inline header.
 217  * @param s the flac decoding context
 218  * @param buf input buffer, starting with the "fLaC" marker
 219  * @param buf_size buffer size
 220  * @return non-zero if metadata is invalid
 221  */
 222 static int parse_streaminfo(FLACContext *s, const uint8_t *buf, int buf_size)
 223 {
 224     int metadata_type, metadata_size;
 225
 226     if (buf_size < FLAC_STREAMINFO_SIZE+8) {
 227         /* need more data */
 228         return 0;
 229     }
 230     ff_flac_parse_block_header(&buf[4], NULL, &metadata_type, &metadata_size);
 231     if (metadata_type != FLAC_METADATA_TYPE_STREAMINFO ||
 232         metadata_size != FLAC_STREAMINFO_SIZE) {
 233         return AVERROR_INVALIDDATA;
 234     }
 235     ff_flac_parse_streaminfo(s->avctx, (FLACStreaminfo *)s, &buf[8]);
 236     allocate_buffers(s);
 237     s->got_streaminfo = 1;
 238
 239     return 0;
 240 }
 241
 242 /**
 243  * Determine the size of an inline header.
 244  * @param buf input buffer, starting with the "fLaC" marker
 245  * @param buf_size buffer size
 246  * @return number of bytes in the header, or 0 if more data is needed
 247  */
 248 static int get_metadata_size(const uint8_t *buf, int buf_size)
 249 {
 250     int metadata_last, metadata_size;
 251     const uint8_t *buf_end = buf + buf_size;
 252
 253     buf += 4;
 254     do {
 255         ff_flac_parse_block_header(buf, &metadata_last, NULL, &metadata_size);
 256         buf += 4;
 257         if (buf + metadata_size > buf_end) {
 258             /* need more data in order to read the complete header */
 259             return 0;
 260         }
 261         buf += metadata_size;
 262     } while (!metadata_last);
 263
 264     return buf_size - (buf_end - buf);
 265 }
 266
 267 static int decode_residuals(FLACContext *s, int channel, int pred_order)
 268 {
 269     int i, tmp, partition, method_type, rice_order;
 270     int sample = 0, samples;
 271
 272     method_type = get_bits(&s->gb, 2);
 273     if (method_type > 1) {
 274         av_log(s->avctx, AV_LOG_ERROR, "illegal residual coding method %d\n",
 275                method_type);
 276         return -1;
 277     }
 278
 279     rice_order = get_bits(&s->gb, 4);
 280
 281     samples= s->blocksize >> rice_order;
 282     if (pred_order > samples) {
 283         av_log(s->avctx, AV_LOG_ERROR, "invalid predictor order: %i > %i\n",
 284                pred_order, samples);
 285         return -1;
 286     }
 287
 288     sample=
 289     i= pred_order;
 290     for (partition = 0; partition < (1 << rice_order); partition++) {
 291         tmp = get_bits(&s->gb, method_type == 0 ? 4 : 5);
 292         if (tmp == (method_type == 0 ? 15 : 31)) {
 293             tmp = get_bits(&s->gb, 5);
 294             for (; i < samples; i++, sample++)
 295                 s->decoded[channel][sample] = get_sbits_long(&s->gb, tmp);
 296         } else {
 297             for (; i < samples; i++, sample++) {
 298                 s->decoded[channel][sample] = get_sr_golomb_flac(&s->gb, tmp, INT_MAX, 0);
 299             }
 300         }
 301         i= 0;
 302     }
 303
 304     return 0;
 305 }
 306
 307 static int decode_subframe_fixed(FLACContext *s, int channel, int pred_order)
 308 {
 309     const int blocksize = s->blocksize;
 310     int32_t *decoded = s->decoded[channel];
 311     int av_uninit(a), av_uninit(b), av_uninit(c), av_uninit(d), i;
 312
 313     /* warm up samples */
 314     for (i = 0; i < pred_order; i++) {
 315         decoded[i] = get_sbits_long(&s->gb, s->curr_bps);
 316     }
 317
 318     if (decode_residuals(s, channel, pred_order) < 0)
 319         return -1;
 320
 321     if (pred_order > 0)
 322         a = decoded[pred_order-1];
 323     if (pred_order > 1)
 324         b = a - decoded[pred_order-2];
 325     if (pred_order > 2)
 326         c = b - decoded[pred_order-2] + decoded[pred_order-3];
 327     if (pred_order > 3)
 328         d = c - decoded[pred_order-2] + 2*decoded[pred_order-3] - decoded[pred_order-4];
 329
 330     switch (pred_order) {
 331     case 0:
 332         break;
 333     case 1:
 334         for (i = pred_order; i < blocksize; i++)
 335             decoded[i] = a += decoded[i];
 336         break;
 337     case 2:
 338         for (i = pred_order; i < blocksize; i++)
 339             decoded[i] = a += b += decoded[i];
 340         break;
 341     case 3:
 342         for (i = pred_order; i < blocksize; i++)
 343             decoded[i] = a += b += c += decoded[i];
 344         break;
 345     case 4:
 346         for (i = pred_order; i < blocksize; i++)
 347             decoded[i] = a += b += c += d += decoded[i];
 348         break;
 349     default:
 350         av_log(s->avctx, AV_LOG_ERROR, "illegal pred order %d\n", pred_order);
 351         return -1;
 352     }
 353
 354     return 0;
 355 }
 356
 357 static int decode_subframe_lpc(FLACContext *s, int channel, int pred_order)
 358 {
 359     int i, j;
 360     int coeff_prec, qlevel;
 361     int coeffs[pred_order];
 362     int32_t *decoded = s->decoded[channel];
 363
 364     /* warm up samples */
 365     for (i = 0; i < pred_order; i++) {
 366         decoded[i] = get_sbits_long(&s->gb, s->curr_bps);
 367     }
 368
 369     coeff_prec = get_bits(&s->gb, 4) + 1;
 370     if (coeff_prec == 16) {
 371         av_log(s->avctx, AV_LOG_ERROR, "invalid coeff precision\n");
 372         return -1;
 373     }
 374     qlevel = get_sbits(&s->gb, 5);
 375     if (qlevel < 0) {
 376         av_log(s->avctx, AV_LOG_ERROR, "qlevel %d not supported, maybe buggy stream\n",
 377                qlevel);
 378         return -1;
 379     }
 380
 381     for (i = 0; i < pred_order; i++) {
 382         coeffs[i] = get_sbits(&s->gb, coeff_prec);
 383     }
 384
 385     if (decode_residuals(s, channel, pred_order) < 0)
 386         return -1;
 387
 388     if (s->bps > 16) {
 389         int64_t sum;
 390         for (i = pred_order; i < s->blocksize; i++) {
 391             sum = 0;
 392             for (j = 0; j < pred_order; j++)
 393                 sum += (int64_t)coeffs[j] * decoded[i-j-1];
 394             decoded[i] += sum >> qlevel;
 395         }
 396     } else {
 397         for (i = pred_order; i < s->blocksize-1; i += 2) {
 398             int c;
 399             int d = decoded[i-pred_order];
 400             int s0 = 0, s1 = 0;
 401             for (j = pred_order-1; j > 0; j--) {
 402                 c = coeffs[j];
 403                 s0 += c*d;
 404                 d = decoded[i-j];
 405                 s1 += c*d;
 406             }
 407             c = coeffs[0];
 408             s0 += c*d;
 409             d = decoded[i] += s0 >> qlevel;
 410             s1 += c*d;
 411             decoded[i+1] += s1 >> qlevel;
 412         }
 413         if (i < s->blocksize) {
 414             int sum = 0;
 415             for (j = 0; j < pred_order; j++)
 416                 sum += coeffs[j] * decoded[i-j-1];
 417             decoded[i] += sum >> qlevel;
 418         }
 419     }
 420
 421     return 0;
 422 }
 423
 424 static inline int decode_subframe(FLACContext *s, int channel)
 425 {
 426     int type, wasted = 0;
 427     int i, tmp;
 428
 429     s->curr_bps = s->bps;
 430     if (channel == 0) {
 431         if (s->ch_mode == FLAC_CHMODE_RIGHT_SIDE)
 432             s->curr_bps++;
 433     } else {
 434         if (s->ch_mode == FLAC_CHMODE_LEFT_SIDE || s->ch_mode == FLAC_CHMODE_MID_SIDE)
 435             s->curr_bps++;
 436     }
 437
 438     if (get_bits1(&s->gb)) {
 439         av_log(s->avctx, AV_LOG_ERROR, "invalid subframe padding\n");
 440         return -1;
 441     }
 442     type = get_bits(&s->gb, 6);
 443
 444     if (get_bits1(&s->gb)) {
 445         wasted = 1;
 446         while (!get_bits1(&s->gb))
 447             wasted++;
 448         s->curr_bps -= wasted;
 449     }
 450     if (s->curr_bps > 32) {
 451         ff_log_missing_feature(s->avctx, "decorrelated bit depth > 32", 0);
 452         return -1;
 453     }
 454
 455 //FIXME use av_log2 for types
 456     if (type == 0) {
 457         tmp = get_sbits_long(&s->gb, s->curr_bps);
 458         for (i = 0; i < s->blocksize; i++)
 459             s->decoded[channel][i] = tmp;
 460     } else if (type == 1) {
 461         for (i = 0; i < s->blocksize; i++)
 462             s->decoded[channel][i] = get_sbits_long(&s->gb, s->curr_bps);
 463     } else if ((type >= 8) && (type <= 12)) {
 464         if (decode_subframe_fixed(s, channel, type & ~0x8) < 0)
 465             return -1;
 466     } else if (type >= 32) {
 467         if (decode_subframe_lpc(s, channel, (type & ~0x20)+1) < 0)
 468             return -1;
 469     } else {
 470         av_log(s->avctx, AV_LOG_ERROR, "invalid coding type\n");
 471         return -1;
 472     }
 473
 474     if (wasted) {
 475         int i;
 476         for (i = 0; i < s->blocksize; i++)
 477             s->decoded[channel][i] <<= wasted;
 478     }
 479
 480     return 0;
 481 }
 482
 483 static int decode_frame(FLACContext *s)
 484 {
 485     int bs_code, sr_code, bps_code, i;
 486     int ch_mode, bps, blocksize, samplerate, channels;
 487     GetBitContext *gb = &s->gb;
 488
 489     /* frame sync code */
 490     skip_bits(&s->gb, 16);
 491
 492     /* block size and sample rate codes */
 493     bs_code = get_bits(gb, 4);
 494     sr_code = get_bits(gb, 4);
 495
 496     /* channels and decorrelation */
 497     ch_mode = get_bits(gb, 4);
 498     if (ch_mode < FLAC_MAX_CHANNELS && s->channels == ch_mode+1) {
 499         channels = ch_mode + 1;
 500         ch_mode = FLAC_CHMODE_INDEPENDENT;
 501     } else if (ch_mode <= FLAC_CHMODE_MID_SIDE) {
 502         channels = 2;
 503     } else {
 504         av_log(s->avctx, AV_LOG_ERROR, "invalid channel mode: %d\n", ch_mode);
 505         return -1;
 506     }
 507     if (channels != s->channels) {
 508         av_log(s->avctx, AV_LOG_ERROR, "switching channel layout mid-stream "
 509                                        "is not supported\n");
 510         return -1;
 511     }
 512
 513     /* bits per sample */
 514     bps_code = get_bits(gb, 3);
 515     if (bps_code == 0)
 516         bps= s->bps;
 517     else if ((bps_code != 3) && (bps_code != 7))
 518         bps = sample_size_table[bps_code];
 519     else {
 520         av_log(s->avctx, AV_LOG_ERROR, "invalid sample size code (%d)\n",
 521                bps_code);
 522         return -1;
 523     }
 524     if (bps > 16) {
 525         s->avctx->sample_fmt = SAMPLE_FMT_S32;
 526         s->sample_shift = 32 - bps;
 527         s->is32 = 1;
 528     } else {
 529         s->avctx->sample_fmt = SAMPLE_FMT_S16;
 530         s->sample_shift = 16 - bps;
 531         s->is32 = 0;
 532     }
 533     s->bps = s->avctx->bits_per_raw_sample = bps;
 534
 535     /* reserved bit */
 536     if (get_bits1(gb)) {
 537         av_log(s->avctx, AV_LOG_ERROR, "broken stream, invalid padding\n");
 538         return -1;
 539     }
 540
 541     /* sample or frame count */
 542     if (get_utf8(gb) < 0) {
 543         av_log(s->avctx, AV_LOG_ERROR, "utf8 fscked\n");
 544         return -1;
 545     }
 546
 547     /* blocksize */
 548     if (bs_code == 0) {
 549         av_log(s->avctx, AV_LOG_ERROR, "reserved blocksize code: 0\n");
 550         return -1;
 551     } else if (bs_code == 6)
 552         blocksize = get_bits(gb, 8)+1;
 553     else if (bs_code == 7)
 554         blocksize = get_bits(gb, 16)+1;
 555     else
 556         blocksize = ff_flac_blocksize_table[bs_code];
 557
 558     if (blocksize > s->max_blocksize) {
 559         av_log(s->avctx, AV_LOG_ERROR, "blocksize %d > %d\n", blocksize,
 560                s->max_blocksize);
 561         return -1;
 562     }
 563
 564     /* sample rate */
 565     if (sr_code == 0)
 566         samplerate= s->samplerate;
 567     else if (sr_code < 12)
 568         samplerate = ff_flac_sample_rate_table[sr_code];
 569     else if (sr_code == 12)
 570         samplerate = get_bits(gb, 8) * 1000;
 571     else if (sr_code == 13)
 572         samplerate = get_bits(gb, 16);
 573     else if (sr_code == 14)
 574         samplerate = get_bits(gb, 16) * 10;
 575     else {
 576         av_log(s->avctx, AV_LOG_ERROR, "illegal sample rate code %d\n",
 577                sr_code);
 578         return -1;
 579     }
 580
 581     /* header CRC-8 check */
 582     skip_bits(gb, 8);
 583     if (av_crc(av_crc_get_table(AV_CRC_8_ATM), 0, gb->buffer,
 584                get_bits_count(gb)/8)) {
 585         av_log(s->avctx, AV_LOG_ERROR, "header crc mismatch\n");
 586         return -1;
 587     }
 588
 589     s->blocksize    = blocksize;
 590     s->samplerate   = samplerate;
 591     s->bps          = bps;
 592     s->ch_mode      = ch_mode;
 593
 594 //    dump_headers(s->avctx, (FLACStreaminfo *)s);
 595
 596     /* subframes */
 597     for (i = 0; i < s->channels; i++) {
 598         if (decode_subframe(s, i) < 0)
 599             return -1;
 600     }
 601
 602     align_get_bits(gb);
 603
 604     /* frame footer */
 605     skip_bits(gb, 16); /* data crc */
 606
 607     return 0;
 608 }
 609
 610 static int flac_decode_frame(AVCodecContext *avctx,
 611                             void *data, int *data_size,
 612                             const uint8_t *buf, int buf_size)
 613 {
 614     FLACContext *s = avctx->priv_data;
 615     int i, j = 0, input_buf_size = 0, bytes_read = 0;
 616     int16_t *samples_16 = data;
 617     int32_t *samples_32 = data;
 618     int alloc_data_size= *data_size;
 619     int output_size;
 620
 621     *data_size=0;
 622
 623     if (s->max_framesize == 0) {
 624         s->max_framesize= FFMAX(4, buf_size); // should hopefully be enough for the first header
 625         s->bitstream= av_fast_realloc(s->bitstream, &s->allocated_bitstream_size, s->max_framesize);
 626     }
 627
 628     if (1 && s->max_framesize) { //FIXME truncated
 629         if (s->bitstream_size < 4 || AV_RL32(s->bitstream) != MKTAG('f','L','a','C'))
 630             buf_size= FFMIN(buf_size, s->max_framesize - FFMIN(s->bitstream_size, s->max_framesize));
 631         input_buf_size= buf_size;
 632
 633         if (s->bitstream_size + buf_size < buf_size || s->bitstream_index + s->bitstream_size + buf_size < s->bitstream_index)
 634             return -1;
 635
 636         if (s->allocated_bitstream_size < s->bitstream_size + buf_size)
 637             s->bitstream= av_fast_realloc(s->bitstream, &s->allocated_bitstream_size, s->bitstream_size + buf_size);
 638
 639         if (s->bitstream_index + s->bitstream_size + buf_size > s->allocated_bitstream_size) {
 640             memmove(s->bitstream, &s->bitstream[s->bitstream_index],
 641                     s->bitstream_size);
 642             s->bitstream_index=0;
 643         }
 644         memcpy(&s->bitstream[s->bitstream_index + s->bitstream_size],
 645                buf, buf_size);
 646         buf= &s->bitstream[s->bitstream_index];
 647         buf_size += s->bitstream_size;
 648         s->bitstream_size= buf_size;
 649
 650         if (buf_size < s->max_framesize && input_buf_size) {
 651             return input_buf_size;
 652         }
 653     }
 654
 655     /* check that there is at least the smallest decodable amount of data.
 656        this amount corresponds to the smallest valid FLAC frame possible.
 657        FF F8 69 02 00 00 9A 00 00 34 46 */
 658     if (buf_size < 11)
 659         goto end;
 660
 661     /* check for inline header */
 662     if (AV_RB32(buf) == MKBETAG('f','L','a','C')) {
 663         if (!s->got_streaminfo && parse_streaminfo(s, buf, buf_size)) {
 664             av_log(s->avctx, AV_LOG_ERROR, "invalid header\n");
 665             return -1;
 666         }
 667         bytes_read = get_metadata_size(buf, buf_size);
 668         goto end;
 669     }
 670
 671     /* check for frame sync code and resync stream if necessary */
 672     if ((AV_RB16(buf) & 0xFFFE) != 0xFFF8) {
 673         const uint8_t *buf_end = buf + buf_size;
 674         av_log(s->avctx, AV_LOG_ERROR, "FRAME HEADER not here\n");
 675         while (buf+2 < buf_end && (AV_RB16(buf) & 0xFFFE) != 0xFFF8)
 676             buf++;
 677         bytes_read = buf_size - (buf_end - buf);
 678         goto end; // we may not have enough bits left to decode a frame, so try next time
 679     }
 680
 681     /* decode frame */
 682     init_get_bits(&s->gb, buf, buf_size*8);
 683     if (decode_frame(s) < 0) {
 684         av_log(s->avctx, AV_LOG_ERROR, "decode_frame() failed\n");
 685         s->bitstream_size=0;
 686         s->bitstream_index=0;
 687         return -1;
 688     }
 689     bytes_read = (get_bits_count(&s->gb)+7)/8;
 690
 691     /* check if allocated data size is large enough for output */
 692     output_size = s->blocksize * s->channels * (s->is32 ? 4 : 2);
 693     if (output_size > alloc_data_size) {
 694         av_log(s->avctx, AV_LOG_ERROR, "output data size is larger than "
 695                                        "allocated data size\n");
 696         return -1;
 697     }
 698     *data_size = output_size;
 699
 700 #define DECORRELATE(left, right)\
 701             assert(s->channels == 2);\
 702             for (i = 0; i < s->blocksize; i++) {\
 703                 int a= s->decoded[0][i];\
 704                 int b= s->decoded[1][i];\
 705                 if (s->is32) {\
 706                     *samples_32++ = (left)  << s->sample_shift;\
 707                     *samples_32++ = (right) << s->sample_shift;\
 708                 } else {\
 709                     *samples_16++ = (left)  << s->sample_shift;\
 710                     *samples_16++ = (right) << s->sample_shift;\
 711                 }\
 712             }\
 713             break;
 714
 715     switch (s->ch_mode) {
 716     case FLAC_CHMODE_INDEPENDENT:
 717         for (j = 0; j < s->blocksize; j++) {
 718             for (i = 0; i < s->channels; i++) {
 719                 if (s->is32)
 720                     *samples_32++ = s->decoded[i][j] << s->sample_shift;
 721                 else
 722                     *samples_16++ = s->decoded[i][j] << s->sample_shift;
 723             }
 724         }
 725         break;
 726     case FLAC_CHMODE_LEFT_SIDE:
 727         DECORRELATE(a,a-b)
 728     case FLAC_CHMODE_RIGHT_SIDE:
 729         DECORRELATE(a+b,b)
 730     case FLAC_CHMODE_MID_SIDE:
 731         DECORRELATE( (a-=b>>1) + b, a)
 732     }
 733
 734 end:
 735     if (bytes_read > buf_size) {
 736         av_log(s->avctx, AV_LOG_ERROR, "overread: %d\n", bytes_read - buf_size);
 737         s->bitstream_size=0;
 738         s->bitstream_index=0;
 739         return -1;
 740     }
 741
 742     if (s->bitstream_size) {
 743         s->bitstream_index += bytes_read;
 744         s->bitstream_size  -= bytes_read;
 745         return input_buf_size;
 746     } else
 747         return bytes_read;
 748 }
 749
 750 static av_cold int flac_decode_close(AVCodecContext *avctx)
 751 {
 752     FLACContext *s = avctx->priv_data;
 753     int i;
 754
 755     for (i = 0; i < s->channels; i++) {
 756         av_freep(&s->decoded[i]);
 757     }
 758     av_freep(&s->bitstream);
 759
 760     return 0;
 761 }
 762
 763 static void flac_flush(AVCodecContext *avctx)
 764 {
 765     FLACContext *s = avctx->priv_data;
 766
 767     s->bitstream_size=
 768     s->bitstream_index= 0;
 769 }
 770
 771 AVCodec flac_decoder = {
 772     "flac",
 773     CODEC_TYPE_AUDIO,
 774     CODEC_ID_FLAC,
 775     sizeof(FLACContext),
 776     flac_decode_init,
 777     NULL,
 778     flac_decode_close,
 779     flac_decode_frame,
 780     CODEC_CAP_DELAY,
 781     .flush= flac_flush,
 782     .long_name= NULL_IF_CONFIG_SMALL("FLAC (Free Lossless Audio Codec)"),
 783 };