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 #define ALT_BITSTREAM_READER
  39 #include "libavutil/crc.h"
  40 #include "avcodec.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, "  Blocksize: %d .. %d\n", s->min_blocksize,
 154            s->max_blocksize);
 155     av_log(avctx, AV_LOG_DEBUG, "  Max Framesize: %d\n", s->max_framesize);
 156     av_log(avctx, AV_LOG_DEBUG, "  Samplerate: %d\n", s->samplerate);
 157     av_log(avctx, AV_LOG_DEBUG, "  Channels: %d\n", s->channels);
 158     av_log(avctx, AV_LOG_DEBUG, "  Bits: %d\n", s->bps);
 159 }
 160
 161 static void allocate_buffers(FLACContext *s)
 162 {
 163     int i;
 164
 165     assert(s->max_blocksize);
 166
 167     if (s->max_framesize == 0 && s->max_blocksize) {
 168         // FIXME header overhead
 169         s->max_framesize= (s->channels * s->bps * s->max_blocksize + 7)/ 8;
 170     }
 171
 172     for (i = 0; i < s->channels; i++) {
 173         s->decoded[i] = av_realloc(s->decoded[i],
 174                                    sizeof(int32_t)*s->max_blocksize);
 175     }
 176
 177     if (s->allocated_bitstream_size < s->max_framesize)
 178         s->bitstream= av_fast_realloc(s->bitstream,
 179                                       &s->allocated_bitstream_size,
 180                                       s->max_framesize);
 181 }
 182
 183 void ff_flac_parse_streaminfo(AVCodecContext *avctx, struct FLACStreaminfo *s,
 184                               const uint8_t *buffer)
 185 {
 186     GetBitContext gb;
 187     init_get_bits(&gb, buffer, FLAC_STREAMINFO_SIZE*8);
 188
 189     /* mandatory streaminfo */
 190     s->min_blocksize = get_bits(&gb, 16);
 191     s->max_blocksize = get_bits(&gb, 16);
 192
 193     skip_bits(&gb, 24); /* skip min frame size */
 194     s->max_framesize = get_bits_long(&gb, 24);
 195
 196     s->samplerate = get_bits_long(&gb, 20);
 197     s->channels = get_bits(&gb, 3) + 1;
 198     s->bps = get_bits(&gb, 5) + 1;
 199
 200     avctx->channels = s->channels;
 201     avctx->sample_rate = s->samplerate;
 202     avctx->bits_per_raw_sample = s->bps;
 203     if (s->bps > 16)
 204         avctx->sample_fmt = SAMPLE_FMT_S32;
 205     else
 206         avctx->sample_fmt = SAMPLE_FMT_S16;
 207
 208     s->samples  = get_bits_long(&gb, 32) << 4;
 209     s->samples |= get_bits(&gb, 4);
 210
 211     skip_bits_long(&gb, 64); /* md5 sum */
 212     skip_bits_long(&gb, 64); /* md5 sum */
 213
 214     dump_headers(avctx, s);
 215 }
 216
 217 /**
 218  * Parse a list of metadata blocks. This list of blocks must begin with
 219  * the fLaC marker.
 220  * @param s the flac decoding context containing the gb bit reader used to
 221  *          parse metadata
 222  * @return 1 if some metadata was read, 0 if no fLaC marker was found
 223  */
 224 static int metadata_parse(FLACContext *s)
 225 {
 226     int i, metadata_last, metadata_type, metadata_size, streaminfo_updated=0;
 227     int initial_pos= get_bits_count(&s->gb);
 228
 229     if (show_bits_long(&s->gb, 32) == MKBETAG('f','L','a','C')) {
 230         skip_bits_long(&s->gb, 32);
 231
 232         do {
 233             metadata_last = get_bits1(&s->gb);
 234             metadata_type = get_bits(&s->gb, 7);
 235             metadata_size = get_bits_long(&s->gb, 24);
 236
 237             if (get_bits_count(&s->gb) + 8*metadata_size > s->gb.size_in_bits) {
 238                 skip_bits_long(&s->gb, initial_pos - get_bits_count(&s->gb));
 239                 break;
 240             }
 241
 242             if (metadata_size) {
 243                 switch (metadata_type) {
 244                 case FLAC_METADATA_TYPE_STREAMINFO:
 245                     ff_flac_parse_streaminfo(s->avctx, (FLACStreaminfo *)s,
 246                                              s->gb.buffer+get_bits_count(&s->gb)/8);
 247                     streaminfo_updated = 1;
 248
 249                 default:
 250                     for (i = 0; i < metadata_size; i++)
 251                         skip_bits(&s->gb, 8);
 252                 }
 253             }
 254         } while (!metadata_last);
 255
 256         if (streaminfo_updated)
 257             allocate_buffers(s);
 258         return 1;
 259     }
 260     return 0;
 261 }
 262
 263 static int decode_residuals(FLACContext *s, int channel, int pred_order)
 264 {
 265     int i, tmp, partition, method_type, rice_order;
 266     int sample = 0, samples;
 267
 268     method_type = get_bits(&s->gb, 2);
 269     if (method_type > 1) {
 270         av_log(s->avctx, AV_LOG_ERROR, "illegal residual coding method %d\n",
 271                method_type);
 272         return -1;
 273     }
 274
 275     rice_order = get_bits(&s->gb, 4);
 276
 277     samples= s->blocksize >> rice_order;
 278     if (pred_order > samples) {
 279         av_log(s->avctx, AV_LOG_ERROR, "invalid predictor order: %i > %i\n",
 280                pred_order, samples);
 281         return -1;
 282     }
 283
 284     sample=
 285     i= pred_order;
 286     for (partition = 0; partition < (1 << rice_order); partition++) {
 287         tmp = get_bits(&s->gb, method_type == 0 ? 4 : 5);
 288         if (tmp == (method_type == 0 ? 15 : 31)) {
 289             tmp = get_bits(&s->gb, 5);
 290             for (; i < samples; i++, sample++)
 291                 s->decoded[channel][sample] = get_sbits(&s->gb, tmp);
 292         } else {
 293             for (; i < samples; i++, sample++) {
 294                 s->decoded[channel][sample] = get_sr_golomb_flac(&s->gb, tmp, INT_MAX, 0);
 295             }
 296         }
 297         i= 0;
 298     }
 299
 300     return 0;
 301 }
 302
 303 static int decode_subframe_fixed(FLACContext *s, int channel, int pred_order)
 304 {
 305     const int blocksize = s->blocksize;
 306     int32_t *decoded = s->decoded[channel];
 307     int av_uninit(a), av_uninit(b), av_uninit(c), av_uninit(d), i;
 308
 309     /* warm up samples */
 310     for (i = 0; i < pred_order; i++) {
 311         decoded[i] = get_sbits(&s->gb, s->curr_bps);
 312     }
 313
 314     if (decode_residuals(s, channel, pred_order) < 0)
 315         return -1;
 316
 317     if (pred_order > 0)
 318         a = decoded[pred_order-1];
 319     if (pred_order > 1)
 320         b = a - decoded[pred_order-2];
 321     if (pred_order > 2)
 322         c = b - decoded[pred_order-2] + decoded[pred_order-3];
 323     if (pred_order > 3)
 324         d = c - decoded[pred_order-2] + 2*decoded[pred_order-3] - decoded[pred_order-4];
 325
 326     switch (pred_order) {
 327     case 0:
 328         break;
 329     case 1:
 330         for (i = pred_order; i < blocksize; i++)
 331             decoded[i] = a += decoded[i];
 332         break;
 333     case 2:
 334         for (i = pred_order; i < blocksize; i++)
 335             decoded[i] = a += b += decoded[i];
 336         break;
 337     case 3:
 338         for (i = pred_order; i < blocksize; i++)
 339             decoded[i] = a += b += c += decoded[i];
 340         break;
 341     case 4:
 342         for (i = pred_order; i < blocksize; i++)
 343             decoded[i] = a += b += c += d += decoded[i];
 344         break;
 345     default:
 346         av_log(s->avctx, AV_LOG_ERROR, "illegal pred order %d\n", pred_order);
 347         return -1;
 348     }
 349
 350     return 0;
 351 }
 352
 353 static int decode_subframe_lpc(FLACContext *s, int channel, int pred_order)
 354 {
 355     int i, j;
 356     int coeff_prec, qlevel;
 357     int coeffs[pred_order];
 358     int32_t *decoded = s->decoded[channel];
 359
 360     /* warm up samples */
 361     for (i = 0; i < pred_order; i++) {
 362         decoded[i] = get_sbits(&s->gb, s->curr_bps);
 363     }
 364
 365     coeff_prec = get_bits(&s->gb, 4) + 1;
 366     if (coeff_prec == 16) {
 367         av_log(s->avctx, AV_LOG_ERROR, "invalid coeff precision\n");
 368         return -1;
 369     }
 370     qlevel = get_sbits(&s->gb, 5);
 371     if (qlevel < 0) {
 372         av_log(s->avctx, AV_LOG_ERROR, "qlevel %d not supported, maybe buggy stream\n",
 373                qlevel);
 374         return -1;
 375     }
 376
 377     for (i = 0; i < pred_order; i++) {
 378         coeffs[i] = get_sbits(&s->gb, coeff_prec);
 379     }
 380
 381     if (decode_residuals(s, channel, pred_order) < 0)
 382         return -1;
 383
 384     if (s->bps > 16) {
 385         int64_t sum;
 386         for (i = pred_order; i < s->blocksize; i++) {
 387             sum = 0;
 388             for (j = 0; j < pred_order; j++)
 389                 sum += (int64_t)coeffs[j] * decoded[i-j-1];
 390             decoded[i] += sum >> qlevel;
 391         }
 392     } else {
 393         for (i = pred_order; i < s->blocksize-1; i += 2) {
 394             int c;
 395             int d = decoded[i-pred_order];
 396             int s0 = 0, s1 = 0;
 397             for (j = pred_order-1; j > 0; j--) {
 398                 c = coeffs[j];
 399                 s0 += c*d;
 400                 d = decoded[i-j];
 401                 s1 += c*d;
 402             }
 403             c = coeffs[0];
 404             s0 += c*d;
 405             d = decoded[i] += s0 >> qlevel;
 406             s1 += c*d;
 407             decoded[i+1] += s1 >> qlevel;
 408         }
 409         if (i < s->blocksize) {
 410             int sum = 0;
 411             for (j = 0; j < pred_order; j++)
 412                 sum += coeffs[j] * decoded[i-j-1];
 413             decoded[i] += sum >> qlevel;
 414         }
 415     }
 416
 417     return 0;
 418 }
 419
 420 static inline int decode_subframe(FLACContext *s, int channel)
 421 {
 422     int type, wasted = 0;
 423     int i, tmp;
 424
 425     s->curr_bps = s->bps;
 426     if (channel == 0) {
 427         if (s->decorrelation == RIGHT_SIDE)
 428             s->curr_bps++;
 429     } else {
 430         if (s->decorrelation == LEFT_SIDE || s->decorrelation == MID_SIDE)
 431             s->curr_bps++;
 432     }
 433
 434     if (get_bits1(&s->gb)) {
 435         av_log(s->avctx, AV_LOG_ERROR, "invalid subframe padding\n");
 436         return -1;
 437     }
 438     type = get_bits(&s->gb, 6);
 439
 440     if (get_bits1(&s->gb)) {
 441         wasted = 1;
 442         while (!get_bits1(&s->gb))
 443             wasted++;
 444         s->curr_bps -= wasted;
 445     }
 446
 447 //FIXME use av_log2 for types
 448     if (type == 0) {
 449         tmp = get_sbits(&s->gb, s->curr_bps);
 450         for (i = 0; i < s->blocksize; i++)
 451             s->decoded[channel][i] = tmp;
 452     } else if (type == 1) {
 453         for (i = 0; i < s->blocksize; i++)
 454             s->decoded[channel][i] = get_sbits(&s->gb, s->curr_bps);
 455     } else if ((type >= 8) && (type <= 12)) {
 456         if (decode_subframe_fixed(s, channel, type & ~0x8) < 0)
 457             return -1;
 458     } else if (type >= 32) {
 459         if (decode_subframe_lpc(s, channel, (type & ~0x20)+1) < 0)
 460             return -1;
 461     } else {
 462         av_log(s->avctx, AV_LOG_ERROR, "invalid coding type\n");
 463         return -1;
 464     }
 465
 466     if (wasted) {
 467         int i;
 468         for (i = 0; i < s->blocksize; i++)
 469             s->decoded[channel][i] <<= wasted;
 470     }
 471
 472     return 0;
 473 }
 474
 475 static int decode_frame(FLACContext *s, int alloc_data_size)
 476 {
 477     int blocksize_code, sample_rate_code, sample_size_code, assignment, i, crc8;
 478     int decorrelation, bps, blocksize, samplerate;
 479
 480     blocksize_code = get_bits(&s->gb, 4);
 481
 482     sample_rate_code = get_bits(&s->gb, 4);
 483
 484     assignment = get_bits(&s->gb, 4); /* channel assignment */
 485     if (assignment < 8 && s->channels == assignment+1)
 486         decorrelation = INDEPENDENT;
 487     else if (assignment >=8 && assignment < 11 && s->channels == 2)
 488         decorrelation = LEFT_SIDE + assignment - 8;
 489     else {
 490         av_log(s->avctx, AV_LOG_ERROR, "unsupported channel assignment %d (channels=%d)\n",
 491                assignment, s->channels);
 492         return -1;
 493     }
 494
 495     sample_size_code = get_bits(&s->gb, 3);
 496     if (sample_size_code == 0)
 497         bps= s->bps;
 498     else if ((sample_size_code != 3) && (sample_size_code != 7))
 499         bps = sample_size_table[sample_size_code];
 500     else {
 501         av_log(s->avctx, AV_LOG_ERROR, "invalid sample size code (%d)\n",
 502                sample_size_code);
 503         return -1;
 504     }
 505     if (bps > 16) {
 506         s->avctx->sample_fmt = SAMPLE_FMT_S32;
 507         s->sample_shift = 32 - bps;
 508         s->is32 = 1;
 509     } else {
 510         s->avctx->sample_fmt = SAMPLE_FMT_S16;
 511         s->sample_shift = 16 - bps;
 512         s->is32 = 0;
 513     }
 514     s->bps = s->avctx->bits_per_raw_sample = bps;
 515
 516     if (get_bits1(&s->gb)) {
 517         av_log(s->avctx, AV_LOG_ERROR, "broken stream, invalid padding\n");
 518         return -1;
 519     }
 520
 521     if (get_utf8(&s->gb) < 0) {
 522         av_log(s->avctx, AV_LOG_ERROR, "utf8 fscked\n");
 523         return -1;
 524     }
 525
 526     if (blocksize_code == 0)
 527         blocksize = s->min_blocksize;
 528     else if (blocksize_code == 6)
 529         blocksize = get_bits(&s->gb, 8)+1;
 530     else if (blocksize_code == 7)
 531         blocksize = get_bits(&s->gb, 16)+1;
 532     else
 533         blocksize = blocksize_table[blocksize_code];
 534
 535     if (blocksize > s->max_blocksize) {
 536         av_log(s->avctx, AV_LOG_ERROR, "blocksize %d > %d\n", blocksize,
 537                s->max_blocksize);
 538         return -1;
 539     }
 540
 541     if (blocksize * s->channels * sizeof(int16_t) > alloc_data_size)
 542         return -1;
 543
 544     if (sample_rate_code == 0)
 545         samplerate= s->samplerate;
 546     else if (sample_rate_code < 12)
 547         samplerate = sample_rate_table[sample_rate_code];
 548     else if (sample_rate_code == 12)
 549         samplerate = get_bits(&s->gb, 8) * 1000;
 550     else if (sample_rate_code == 13)
 551         samplerate = get_bits(&s->gb, 16);
 552     else if (sample_rate_code == 14)
 553         samplerate = get_bits(&s->gb, 16) * 10;
 554     else {
 555         av_log(s->avctx, AV_LOG_ERROR, "illegal sample rate code %d\n",
 556                sample_rate_code);
 557         return -1;
 558     }
 559
 560     skip_bits(&s->gb, 8);
 561     crc8 = av_crc(av_crc_get_table(AV_CRC_8_ATM), 0,
 562                   s->gb.buffer, get_bits_count(&s->gb)/8);
 563     if (crc8) {
 564         av_log(s->avctx, AV_LOG_ERROR, "header crc mismatch crc=%2X\n", crc8);
 565         return -1;
 566     }
 567
 568     s->blocksize    = blocksize;
 569     s->samplerate   = samplerate;
 570     s->bps          = bps;
 571     s->decorrelation= decorrelation;
 572
 573 //    dump_headers(s->avctx, (FLACStreaminfo *)s);
 574
 575     /* subframes */
 576     for (i = 0; i < s->channels; i++) {
 577         if (decode_subframe(s, i) < 0)
 578             return -1;
 579     }
 580
 581     align_get_bits(&s->gb);
 582
 583     /* frame footer */
 584     skip_bits(&s->gb, 16); /* data crc */
 585
 586     return 0;
 587 }
 588
 589 static int flac_decode_frame(AVCodecContext *avctx,
 590                             void *data, int *data_size,
 591                             const uint8_t *buf, int buf_size)
 592 {
 593     FLACContext *s = avctx->priv_data;
 594     int tmp = 0, i, j = 0, input_buf_size = 0;
 595     int16_t *samples_16 = data;
 596     int32_t *samples_32 = data;
 597     int alloc_data_size= *data_size;
 598
 599     *data_size=0;
 600
 601     if (s->max_framesize == 0) {
 602         s->max_framesize= FFMAX(4, buf_size); // should hopefully be enough for the first header
 603         s->bitstream= av_fast_realloc(s->bitstream, &s->allocated_bitstream_size, s->max_framesize);
 604     }
 605
 606     if (1 && s->max_framesize) { //FIXME truncated
 607         if (s->bitstream_size < 4 || AV_RL32(s->bitstream) != MKTAG('f','L','a','C'))
 608             buf_size= FFMIN(buf_size, s->max_framesize - FFMIN(s->bitstream_size, s->max_framesize));
 609         input_buf_size= buf_size;
 610
 611         if (s->bitstream_size + buf_size < buf_size || s->bitstream_index + s->bitstream_size + buf_size < s->bitstream_index)
 612             return -1;
 613
 614         if (s->allocated_bitstream_size < s->bitstream_size + buf_size)
 615             s->bitstream= av_fast_realloc(s->bitstream, &s->allocated_bitstream_size, s->bitstream_size + buf_size);
 616
 617         if (s->bitstream_index + s->bitstream_size + buf_size > s->allocated_bitstream_size) {
 618             memmove(s->bitstream, &s->bitstream[s->bitstream_index],
 619                     s->bitstream_size);
 620             s->bitstream_index=0;
 621         }
 622         memcpy(&s->bitstream[s->bitstream_index + s->bitstream_size],
 623                buf, buf_size);
 624         buf= &s->bitstream[s->bitstream_index];
 625         buf_size += s->bitstream_size;
 626         s->bitstream_size= buf_size;
 627
 628         if (buf_size < s->max_framesize && input_buf_size) {
 629             return input_buf_size;
 630         }
 631     }
 632
 633     init_get_bits(&s->gb, buf, buf_size*8);
 634
 635     if (metadata_parse(s))
 636         goto end;
 637
 638     tmp = show_bits(&s->gb, 16);
 639     if ((tmp & 0xFFFE) != 0xFFF8) {
 640         av_log(s->avctx, AV_LOG_ERROR, "FRAME HEADER not here\n");
 641         while (get_bits_count(&s->gb)/8+2 < buf_size && (show_bits(&s->gb, 16) & 0xFFFE) != 0xFFF8)
 642             skip_bits(&s->gb, 8);
 643         goto end; // we may not have enough bits left to decode a frame, so try next time
 644     }
 645     skip_bits(&s->gb, 16);
 646     if (decode_frame(s, alloc_data_size) < 0) {
 647         av_log(s->avctx, AV_LOG_ERROR, "decode_frame() failed\n");
 648         s->bitstream_size=0;
 649         s->bitstream_index=0;
 650         return -1;
 651     }
 652
 653 #define DECORRELATE(left, right)\
 654             assert(s->channels == 2);\
 655             for (i = 0; i < s->blocksize; i++) {\
 656                 int a= s->decoded[0][i];\
 657                 int b= s->decoded[1][i];\
 658                 if (s->is32) {\
 659                     *samples_32++ = (left)  << s->sample_shift;\
 660                     *samples_32++ = (right) << s->sample_shift;\
 661                 } else {\
 662                     *samples_16++ = (left)  << s->sample_shift;\
 663                     *samples_16++ = (right) << s->sample_shift;\
 664                 }\
 665             }\
 666             break;
 667
 668     switch (s->decorrelation) {
 669     case INDEPENDENT:
 670         for (j = 0; j < s->blocksize; j++) {
 671             for (i = 0; i < s->channels; i++) {
 672                 if (s->is32)
 673                     *samples_32++ = s->decoded[i][j] << s->sample_shift;
 674                 else
 675                     *samples_16++ = s->decoded[i][j] << s->sample_shift;
 676             }
 677         }
 678         break;
 679     case LEFT_SIDE:
 680         DECORRELATE(a,a-b)
 681     case RIGHT_SIDE:
 682         DECORRELATE(a+b,b)
 683     case MID_SIDE:
 684         DECORRELATE( (a-=b>>1) + b, a)
 685     }
 686
 687     *data_size = s->blocksize * s->channels * (s->is32 ? 4 : 2);
 688
 689 end:
 690     i= (get_bits_count(&s->gb)+7)/8;
 691     if (i > buf_size) {
 692         av_log(s->avctx, AV_LOG_ERROR, "overread: %d\n", i - buf_size);
 693         s->bitstream_size=0;
 694         s->bitstream_index=0;
 695         return -1;
 696     }
 697
 698     if (s->bitstream_size) {
 699         s->bitstream_index += i;
 700         s->bitstream_size  -= i;
 701         return input_buf_size;
 702     } else
 703         return i;
 704 }
 705
 706 static av_cold int flac_decode_close(AVCodecContext *avctx)
 707 {
 708     FLACContext *s = avctx->priv_data;
 709     int i;
 710
 711     for (i = 0; i < s->channels; i++) {
 712         av_freep(&s->decoded[i]);
 713     }
 714     av_freep(&s->bitstream);
 715
 716     return 0;
 717 }
 718
 719 static void flac_flush(AVCodecContext *avctx)
 720 {
 721     FLACContext *s = avctx->priv_data;
 722
 723     s->bitstream_size=
 724     s->bitstream_index= 0;
 725 }
 726
 727 AVCodec flac_decoder = {
 728     "flac",
 729     CODEC_TYPE_AUDIO,
 730     CODEC_ID_FLAC,
 731     sizeof(FLACContext),
 732     flac_decode_init,
 733     NULL,
 734     flac_decode_close,
 735     flac_decode_frame,
 736     CODEC_CAP_DELAY,
 737     .flush= flac_flush,
 738     .long_name= NULL_IF_CONFIG_SMALL("FLAC (Free Lossless Audio Codec)"),
 739 };