libavcodec/apedec.c

   1 /*
   2  * Monkey's Audio lossless audio decoder
   3  * Copyright (c) 2007 Benjamin Zores <ben@geexbox.org>
   4  *  based upon libdemac from Dave Chapman.
   5  *
   6  * This file is part of FFmpeg.
   7  *
   8  * FFmpeg is free software; you can redistribute it and/or
   9  * modify it under the terms of the GNU Lesser General Public
  10  * License as published by the Free Software Foundation; either
  11  * version 2.1 of the License, or (at your option) any later version.
  12  *
  13  * FFmpeg is distributed in the hope that it will be useful,
  14  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  15  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  16  * Lesser General Public License for more details.
  17  *
  18  * You should have received a copy of the GNU Lesser General Public
  19  * License along with FFmpeg; if not, write to the Free Software
  20  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  21  */
  22
  23 #define ALT_BITSTREAM_READER_LE
  24 #include "avcodec.h"
  25 #include "dsputil.h"
  26 #include "get_bits.h"
  27 #include "bytestream.h"
  28
  29 /**
  30  * @file
  31  * Monkey's Audio lossless audio decoder
  32  */
  33
  34 #define BLOCKS_PER_LOOP     4608
  35 #define MAX_CHANNELS        2
  36 #define MAX_BYTESPERSAMPLE  3
  37
  38 #define APE_FRAMECODE_MONO_SILENCE    1
  39 #define APE_FRAMECODE_STEREO_SILENCE  3
  40 #define APE_FRAMECODE_PSEUDO_STEREO   4
  41
  42 #define HISTORY_SIZE 512
  43 #define PREDICTOR_ORDER 8
  44 /** Total size of all predictor histories */
  45 #define PREDICTOR_SIZE 50
  46
  47 #define YDELAYA (18 + PREDICTOR_ORDER*4)
  48 #define YDELAYB (18 + PREDICTOR_ORDER*3)
  49 #define XDELAYA (18 + PREDICTOR_ORDER*2)
  50 #define XDELAYB (18 + PREDICTOR_ORDER)
  51
  52 #define YADAPTCOEFFSA 18
  53 #define XADAPTCOEFFSA 14
  54 #define YADAPTCOEFFSB 10
  55 #define XADAPTCOEFFSB 5
  56
  57 /**
  58  * Possible compression levels
  59  * @{
  60  */
  61 enum APECompressionLevel {
  62     COMPRESSION_LEVEL_FAST       = 1000,
  63     COMPRESSION_LEVEL_NORMAL     = 2000,
  64     COMPRESSION_LEVEL_HIGH       = 3000,
  65     COMPRESSION_LEVEL_EXTRA_HIGH = 4000,
  66     COMPRESSION_LEVEL_INSANE     = 5000
  67 };
  68 /** @} */
  69
  70 #define APE_FILTER_LEVELS 3
  71
  72 /** Filter orders depending on compression level */
  73 static const uint16_t ape_filter_orders[5][APE_FILTER_LEVELS] = {
  74     {  0,   0,    0 },
  75     { 16,   0,    0 },
  76     { 64,   0,    0 },
  77     { 32, 256,    0 },
  78     { 16, 256, 1280 }
  79 };
  80
  81 /** Filter fraction bits depending on compression level */
  82 static const uint8_t ape_filter_fracbits[5][APE_FILTER_LEVELS] = {
  83     {  0,  0,  0 },
  84     { 11,  0,  0 },
  85     { 11,  0,  0 },
  86     { 10, 13,  0 },
  87     { 11, 13, 15 }
  88 };
  89
  90
  91 /** Filters applied to the decoded data */
  92 typedef struct APEFilter {
  93     int16_t *coeffs;        ///< actual coefficients used in filtering
  94     int16_t *adaptcoeffs;   ///< adaptive filter coefficients used for correcting of actual filter coefficients
  95     int16_t *historybuffer; ///< filter memory
  96     int16_t *delay;         ///< filtered values
  97
  98     int avg;
  99 } APEFilter;
 100
 101 typedef struct APERice {
 102     uint32_t k;
 103     uint32_t ksum;
 104 } APERice;
 105
 106 typedef struct APERangecoder {
 107     uint32_t low;           ///< low end of interval
 108     uint32_t range;         ///< length of interval
 109     uint32_t help;          ///< bytes_to_follow resp. intermediate value
 110     unsigned int buffer;    ///< buffer for input/output
 111 } APERangecoder;
 112
 113 /** Filter histories */
 114 typedef struct APEPredictor {
 115     int32_t *buf;
 116
 117     int32_t lastA[2];
 118
 119     int32_t filterA[2];
 120     int32_t filterB[2];
 121
 122     int32_t coeffsA[2][4];  ///< adaption coefficients
 123     int32_t coeffsB[2][5];  ///< adaption coefficients
 124     int32_t historybuffer[HISTORY_SIZE + PREDICTOR_SIZE];
 125 } APEPredictor;
 126
 127 /** Decoder context */
 128 typedef struct APEContext {
 129     AVCodecContext *avctx;
 130     DSPContext dsp;
 131     int channels;
 132     int samples;                             ///< samples left to decode in current frame
 133
 134     int fileversion;                         ///< codec version, very important in decoding process
 135     int compression_level;                   ///< compression levels
 136     int fset;                                ///< which filter set to use (calculated from compression level)
 137     int flags;                               ///< global decoder flags
 138
 139     uint32_t CRC;                            ///< frame CRC
 140     int frameflags;                          ///< frame flags
 141     int currentframeblocks;                  ///< samples (per channel) in current frame
 142     int blocksdecoded;                       ///< count of decoded samples in current frame
 143     APEPredictor predictor;                  ///< predictor used for final reconstruction
 144
 145     int32_t decoded0[BLOCKS_PER_LOOP];       ///< decoded data for the first channel
 146     int32_t decoded1[BLOCKS_PER_LOOP];       ///< decoded data for the second channel
 147
 148     int16_t* filterbuf[APE_FILTER_LEVELS];   ///< filter memory
 149
 150     APERangecoder rc;                        ///< rangecoder used to decode actual values
 151     APERice riceX;                           ///< rice code parameters for the second channel
 152     APERice riceY;                           ///< rice code parameters for the first channel
 153     APEFilter filters[APE_FILTER_LEVELS][2]; ///< filters used for reconstruction
 154
 155     uint8_t *data;                           ///< current frame data
 156     uint8_t *data_end;                       ///< frame data end
 157     const uint8_t *ptr;                      ///< current position in frame data
 158     const uint8_t *last_ptr;                 ///< position where last 4608-sample block ended
 159
 160     int error;
 161 } APEContext;
 162
 163 // TODO: dsputilize
 164
 165 static av_cold int ape_decode_init(AVCodecContext * avctx)
 166 {
 167     APEContext *s = avctx->priv_data;
 168     int i;
 169
 170     if (avctx->extradata_size != 6) {
 171         av_log(avctx, AV_LOG_ERROR, "Incorrect extradata\n");
 172         return -1;
 173     }
 174     if (avctx->bits_per_coded_sample != 16) {
 175         av_log(avctx, AV_LOG_ERROR, "Only 16-bit samples are supported\n");
 176         return -1;
 177     }
 178     if (avctx->channels > 2) {
 179         av_log(avctx, AV_LOG_ERROR, "Only mono and stereo is supported\n");
 180         return -1;
 181     }
 182     s->avctx             = avctx;
 183     s->channels          = avctx->channels;
 184     s->fileversion       = AV_RL16(avctx->extradata);
 185     s->compression_level = AV_RL16(avctx->extradata + 2);
 186     s->flags             = AV_RL16(avctx->extradata + 4);
 187
 188     av_log(avctx, AV_LOG_DEBUG, "Compression Level: %d - Flags: %d\n", s->compression_level, s->flags);
 189     if (s->compression_level % 1000 || s->compression_level > COMPRESSION_LEVEL_INSANE) {
 190         av_log(avctx, AV_LOG_ERROR, "Incorrect compression level %d\n", s->compression_level);
 191         return -1;
 192     }
 193     s->fset = s->compression_level / 1000 - 1;
 194     for (i = 0; i < APE_FILTER_LEVELS; i++) {
 195         if (!ape_filter_orders[s->fset][i])
 196             break;
 197         s->filterbuf[i] = av_malloc((ape_filter_orders[s->fset][i] * 3 + HISTORY_SIZE) * 4);
 198     }
 199
 200     dsputil_init(&s->dsp, avctx);
 201     avctx->sample_fmt = SAMPLE_FMT_S16;
 202     avctx->channel_layout = (avctx->channels==2) ? CH_LAYOUT_STEREO : CH_LAYOUT_MONO;
 203     return 0;
 204 }
 205
 206 static av_cold int ape_decode_close(AVCodecContext * avctx)
 207 {
 208     APEContext *s = avctx->priv_data;
 209     int i;
 210
 211     for (i = 0; i < APE_FILTER_LEVELS; i++)
 212         av_freep(&s->filterbuf[i]);
 213
 214     av_freep(&s->data);
 215     return 0;
 216 }
 217
 218 /**
 219  * @defgroup rangecoder APE range decoder
 220  * @{
 221  */
 222
 223 #define CODE_BITS    32
 224 #define TOP_VALUE    ((unsigned int)1 << (CODE_BITS-1))
 225 #define SHIFT_BITS   (CODE_BITS - 9)
 226 #define EXTRA_BITS   ((CODE_BITS-2) % 8 + 1)
 227 #define BOTTOM_VALUE (TOP_VALUE >> 8)
 228
 229 /** Start the decoder */
 230 static inline void range_start_decoding(APEContext * ctx)
 231 {
 232     ctx->rc.buffer = bytestream_get_byte(&ctx->ptr);
 233     ctx->rc.low    = ctx->rc.buffer >> (8 - EXTRA_BITS);
 234     ctx->rc.range  = (uint32_t) 1 << EXTRA_BITS;
 235 }
 236
 237 /** Perform normalization */
 238 static inline void range_dec_normalize(APEContext * ctx)
 239 {
 240     while (ctx->rc.range <= BOTTOM_VALUE) {
 241         ctx->rc.buffer <<= 8;
 242         if(ctx->ptr < ctx->data_end)
 243             ctx->rc.buffer += *ctx->ptr;
 244         ctx->ptr++;
 245         ctx->rc.low    = (ctx->rc.low << 8)    | ((ctx->rc.buffer >> 1) & 0xFF);
 246         ctx->rc.range  <<= 8;
 247     }
 248 }
 249
 250 /**
 251  * Calculate culmulative frequency for next symbol. Does NO update!
 252  * @param ctx decoder context
 253  * @param tot_f is the total frequency or (code_value)1<<shift
 254  * @return the culmulative frequency
 255  */
 256 static inline int range_decode_culfreq(APEContext * ctx, int tot_f)
 257 {
 258     range_dec_normalize(ctx);
 259     ctx->rc.help = ctx->rc.range / tot_f;
 260     return ctx->rc.low / ctx->rc.help;
 261 }
 262
 263 /**
 264  * Decode value with given size in bits
 265  * @param ctx decoder context
 266  * @param shift number of bits to decode
 267  */
 268 static inline int range_decode_culshift(APEContext * ctx, int shift)
 269 {
 270     range_dec_normalize(ctx);
 271     ctx->rc.help = ctx->rc.range >> shift;
 272     return ctx->rc.low / ctx->rc.help;
 273 }
 274
 275
 276 /**
 277  * Update decoding state
 278  * @param ctx decoder context
 279  * @param sy_f the interval length (frequency of the symbol)
 280  * @param lt_f the lower end (frequency sum of < symbols)
 281  */
 282 static inline void range_decode_update(APEContext * ctx, int sy_f, int lt_f)
 283 {
 284     ctx->rc.low  -= ctx->rc.help * lt_f;
 285     ctx->rc.range = ctx->rc.help * sy_f;
 286 }
 287
 288 /** Decode n bits (n <= 16) without modelling */
 289 static inline int range_decode_bits(APEContext * ctx, int n)
 290 {
 291     int sym = range_decode_culshift(ctx, n);
 292     range_decode_update(ctx, 1, sym);
 293     return sym;
 294 }
 295
 296
 297 #define MODEL_ELEMENTS 64
 298
 299 /**
 300  * Fixed probabilities for symbols in Monkey Audio version 3.97
 301  */
 302 static const uint16_t counts_3970[22] = {
 303         0, 14824, 28224, 39348, 47855, 53994, 58171, 60926,
 304     62682, 63786, 64463, 64878, 65126, 65276, 65365, 65419,
 305     65450, 65469, 65480, 65487, 65491, 65493,
 306 };
 307
 308 /**
 309  * Probability ranges for symbols in Monkey Audio version 3.97
 310  */
 311 static const uint16_t counts_diff_3970[21] = {
 312     14824, 13400, 11124, 8507, 6139, 4177, 2755, 1756,
 313     1104, 677, 415, 248, 150, 89, 54, 31,
 314     19, 11, 7, 4, 2,
 315 };
 316
 317 /**
 318  * Fixed probabilities for symbols in Monkey Audio version 3.98
 319  */
 320 static const uint16_t counts_3980[22] = {
 321         0, 19578, 36160, 48417, 56323, 60899, 63265, 64435,
 322     64971, 65232, 65351, 65416, 65447, 65466, 65476, 65482,
 323     65485, 65488, 65490, 65491, 65492, 65493,
 324 };
 325
 326 /**
 327  * Probability ranges for symbols in Monkey Audio version 3.98
 328  */
 329 static const uint16_t counts_diff_3980[21] = {
 330     19578, 16582, 12257, 7906, 4576, 2366, 1170, 536,
 331     261, 119, 65, 31, 19, 10, 6, 3,
 332     3, 2, 1, 1, 1,
 333 };
 334
 335 /**
 336  * Decode symbol
 337  * @param ctx decoder context
 338  * @param counts probability range start position
 339  * @param counts_diff probability range widths
 340  */
 341 static inline int range_get_symbol(APEContext * ctx,
 342                                    const uint16_t counts[],
 343                                    const uint16_t counts_diff[])
 344 {
 345     int symbol, cf;
 346
 347     cf = range_decode_culshift(ctx, 16);
 348
 349     if(cf > 65492){
 350         symbol= cf - 65535 + 63;
 351         range_decode_update(ctx, 1, cf);
 352         if(cf > 65535)
 353             ctx->error=1;
 354         return symbol;
 355     }
 356     /* figure out the symbol inefficiently; a binary search would be much better */
 357     for (symbol = 0; counts[symbol + 1] <= cf; symbol++);
 358
 359     range_decode_update(ctx, counts_diff[symbol], counts[symbol]);
 360
 361     return symbol;
 362 }
 363 /** @} */ // group rangecoder
 364
 365 static inline void update_rice(APERice *rice, int x)
 366 {
 367     int lim = rice->k ? (1 << (rice->k + 4)) : 0;
 368     rice->ksum += ((x + 1) / 2) - ((rice->ksum + 16) >> 5);
 369
 370     if (rice->ksum < lim)
 371         rice->k--;
 372     else if (rice->ksum >= (1 << (rice->k + 5)))
 373         rice->k++;
 374 }
 375
 376 static inline int ape_decode_value(APEContext * ctx, APERice *rice)
 377 {
 378     int x, overflow;
 379
 380     if (ctx->fileversion < 3990) {
 381         int tmpk;
 382
 383         overflow = range_get_symbol(ctx, counts_3970, counts_diff_3970);
 384
 385         if (overflow == (MODEL_ELEMENTS - 1)) {
 386             tmpk = range_decode_bits(ctx, 5);
 387             overflow = 0;
 388         } else
 389             tmpk = (rice->k < 1) ? 0 : rice->k - 1;
 390
 391         if (tmpk <= 16)
 392             x = range_decode_bits(ctx, tmpk);
 393         else {
 394             x = range_decode_bits(ctx, 16);
 395             x |= (range_decode_bits(ctx, tmpk - 16) << 16);
 396         }
 397         x += overflow << tmpk;
 398     } else {
 399         int base, pivot;
 400
 401         pivot = rice->ksum >> 5;
 402         if (pivot == 0)
 403             pivot = 1;
 404
 405         overflow = range_get_symbol(ctx, counts_3980, counts_diff_3980);
 406
 407         if (overflow == (MODEL_ELEMENTS - 1)) {
 408             overflow  = range_decode_bits(ctx, 16) << 16;
 409             overflow |= range_decode_bits(ctx, 16);
 410         }
 411
 412         if (pivot < 0x10000) {
 413             base = range_decode_culfreq(ctx, pivot);
 414             range_decode_update(ctx, 1, base);
 415         } else {
 416             int base_hi = pivot, base_lo;
 417             int bbits = 0;
 418
 419             while (base_hi & ~0xFFFF) {
 420                 base_hi >>= 1;
 421                 bbits++;
 422             }
 423             base_hi = range_decode_culfreq(ctx, base_hi + 1);
 424             range_decode_update(ctx, 1, base_hi);
 425             base_lo = range_decode_culfreq(ctx, 1 << bbits);
 426             range_decode_update(ctx, 1, base_lo);
 427
 428             base = (base_hi << bbits) + base_lo;
 429         }
 430
 431         x = base + overflow * pivot;
 432     }
 433
 434     update_rice(rice, x);
 435
 436     /* Convert to signed */
 437     if (x & 1)
 438         return (x >> 1) + 1;
 439     else
 440         return -(x >> 1);
 441 }
 442
 443 static void entropy_decode(APEContext * ctx, int blockstodecode, int stereo)
 444 {
 445     int32_t *decoded0 = ctx->decoded0;
 446     int32_t *decoded1 = ctx->decoded1;
 447
 448     ctx->blocksdecoded = blockstodecode;
 449
 450     if (ctx->frameflags & APE_FRAMECODE_STEREO_SILENCE) {
 451         /* We are pure silence, just memset the output buffer. */
 452         memset(decoded0, 0, blockstodecode * sizeof(int32_t));
 453         memset(decoded1, 0, blockstodecode * sizeof(int32_t));
 454     } else {
 455         while (blockstodecode--) {
 456             *decoded0++ = ape_decode_value(ctx, &ctx->riceY);
 457             if (stereo)
 458                 *decoded1++ = ape_decode_value(ctx, &ctx->riceX);
 459         }
 460     }
 461
 462     if (ctx->blocksdecoded == ctx->currentframeblocks)
 463         range_dec_normalize(ctx);   /* normalize to use up all bytes */
 464 }
 465
 466 static void init_entropy_decoder(APEContext * ctx)
 467 {
 468     /* Read the CRC */
 469     ctx->CRC = bytestream_get_be32(&ctx->ptr);
 470
 471     /* Read the frame flags if they exist */
 472     ctx->frameflags = 0;
 473     if ((ctx->fileversion > 3820) && (ctx->CRC & 0x80000000)) {
 474         ctx->CRC &= ~0x80000000;
 475
 476         ctx->frameflags = bytestream_get_be32(&ctx->ptr);
 477     }
 478
 479     /* Keep a count of the blocks decoded in this frame */
 480     ctx->blocksdecoded = 0;
 481
 482     /* Initialize the rice structs */
 483     ctx->riceX.k = 10;
 484     ctx->riceX.ksum = (1 << ctx->riceX.k) * 16;
 485     ctx->riceY.k = 10;
 486     ctx->riceY.ksum = (1 << ctx->riceY.k) * 16;
 487
 488     /* The first 8 bits of input are ignored. */
 489     ctx->ptr++;
 490
 491     range_start_decoding(ctx);
 492 }
 493
 494 static const int32_t initial_coeffs[4] = {
 495     360, 317, -109, 98
 496 };
 497
 498 static void init_predictor_decoder(APEContext * ctx)
 499 {
 500     APEPredictor *p = &ctx->predictor;
 501
 502     /* Zero the history buffers */
 503     memset(p->historybuffer, 0, PREDICTOR_SIZE * sizeof(int32_t));
 504     p->buf = p->historybuffer;
 505
 506     /* Initialize and zero the coefficients */
 507     memcpy(p->coeffsA[0], initial_coeffs, sizeof(initial_coeffs));
 508     memcpy(p->coeffsA[1], initial_coeffs, sizeof(initial_coeffs));
 509     memset(p->coeffsB, 0, sizeof(p->coeffsB));
 510
 511     p->filterA[0] = p->filterA[1] = 0;
 512     p->filterB[0] = p->filterB[1] = 0;
 513     p->lastA[0]   = p->lastA[1]   = 0;
 514 }
 515
 516 /** Get inverse sign of integer (-1 for positive, 1 for negative and 0 for zero) */
 517 static inline int APESIGN(int32_t x) {
 518     return (x < 0) - (x > 0);
 519 }
 520
 521 static av_always_inline int predictor_update_filter(APEPredictor *p, const int decoded, const int filter, const int delayA, const int delayB, const int adaptA, const int adaptB)
 522 {
 523     int32_t predictionA, predictionB, sign;
 524
 525     p->buf[delayA]     = p->lastA[filter];
 526     p->buf[adaptA]     = APESIGN(p->buf[delayA]);
 527     p->buf[delayA - 1] = p->buf[delayA] - p->buf[delayA - 1];
 528     p->buf[adaptA - 1] = APESIGN(p->buf[delayA - 1]);
 529
 530     predictionA = p->buf[delayA    ] * p->coeffsA[filter][0] +
 531                   p->buf[delayA - 1] * p->coeffsA[filter][1] +
 532                   p->buf[delayA - 2] * p->coeffsA[filter][2] +
 533                   p->buf[delayA - 3] * p->coeffsA[filter][3];
 534
 535     /*  Apply a scaled first-order filter compression */
 536     p->buf[delayB]     = p->filterA[filter ^ 1] - ((p->filterB[filter] * 31) >> 5);
 537     p->buf[adaptB]     = APESIGN(p->buf[delayB]);
 538     p->buf[delayB - 1] = p->buf[delayB] - p->buf[delayB - 1];
 539     p->buf[adaptB - 1] = APESIGN(p->buf[delayB - 1]);
 540     p->filterB[filter] = p->filterA[filter ^ 1];
 541
 542     predictionB = p->buf[delayB    ] * p->coeffsB[filter][0] +
 543                   p->buf[delayB - 1] * p->coeffsB[filter][1] +
 544                   p->buf[delayB - 2] * p->coeffsB[filter][2] +
 545                   p->buf[delayB - 3] * p->coeffsB[filter][3] +
 546                   p->buf[delayB - 4] * p->coeffsB[filter][4];
 547
 548     p->lastA[filter] = decoded + ((predictionA + (predictionB >> 1)) >> 10);
 549     p->filterA[filter] = p->lastA[filter] + ((p->filterA[filter] * 31) >> 5);
 550
 551     sign = APESIGN(decoded);
 552     p->coeffsA[filter][0] += p->buf[adaptA    ] * sign;
 553     p->coeffsA[filter][1] += p->buf[adaptA - 1] * sign;
 554     p->coeffsA[filter][2] += p->buf[adaptA - 2] * sign;
 555     p->coeffsA[filter][3] += p->buf[adaptA - 3] * sign;
 556     p->coeffsB[filter][0] += p->buf[adaptB    ] * sign;
 557     p->coeffsB[filter][1] += p->buf[adaptB - 1] * sign;
 558     p->coeffsB[filter][2] += p->buf[adaptB - 2] * sign;
 559     p->coeffsB[filter][3] += p->buf[adaptB - 3] * sign;
 560     p->coeffsB[filter][4] += p->buf[adaptB - 4] * sign;
 561
 562     return p->filterA[filter];
 563 }
 564
 565 static void predictor_decode_stereo(APEContext * ctx, int count)
 566 {
 567     APEPredictor *p = &ctx->predictor;
 568     int32_t *decoded0 = ctx->decoded0;
 569     int32_t *decoded1 = ctx->decoded1;
 570
 571     while (count--) {
 572         /* Predictor Y */
 573         *decoded0 = predictor_update_filter(p, *decoded0, 0, YDELAYA, YDELAYB, YADAPTCOEFFSA, YADAPTCOEFFSB);
 574         decoded0++;
 575         *decoded1 = predictor_update_filter(p, *decoded1, 1, XDELAYA, XDELAYB, XADAPTCOEFFSA, XADAPTCOEFFSB);
 576         decoded1++;
 577
 578         /* Combined */
 579         p->buf++;
 580
 581         /* Have we filled the history buffer? */
 582         if (p->buf == p->historybuffer + HISTORY_SIZE) {
 583             memmove(p->historybuffer, p->buf, PREDICTOR_SIZE * sizeof(int32_t));
 584             p->buf = p->historybuffer;
 585         }
 586     }
 587 }
 588
 589 static void predictor_decode_mono(APEContext * ctx, int count)
 590 {
 591     APEPredictor *p = &ctx->predictor;
 592     int32_t *decoded0 = ctx->decoded0;
 593     int32_t predictionA, currentA, A, sign;
 594
 595     currentA = p->lastA[0];
 596
 597     while (count--) {
 598         A = *decoded0;
 599
 600         p->buf[YDELAYA] = currentA;
 601         p->buf[YDELAYA - 1] = p->buf[YDELAYA] - p->buf[YDELAYA - 1];
 602
 603         predictionA = p->buf[YDELAYA    ] * p->coeffsA[0][0] +
 604                       p->buf[YDELAYA - 1] * p->coeffsA[0][1] +
 605                       p->buf[YDELAYA - 2] * p->coeffsA[0][2] +
 606                       p->buf[YDELAYA - 3] * p->coeffsA[0][3];
 607
 608         currentA = A + (predictionA >> 10);
 609
 610         p->buf[YADAPTCOEFFSA]     = APESIGN(p->buf[YDELAYA    ]);
 611         p->buf[YADAPTCOEFFSA - 1] = APESIGN(p->buf[YDELAYA - 1]);
 612
 613         sign = APESIGN(A);
 614         p->coeffsA[0][0] += p->buf[YADAPTCOEFFSA    ] * sign;
 615         p->coeffsA[0][1] += p->buf[YADAPTCOEFFSA - 1] * sign;
 616         p->coeffsA[0][2] += p->buf[YADAPTCOEFFSA - 2] * sign;
 617         p->coeffsA[0][3] += p->buf[YADAPTCOEFFSA - 3] * sign;
 618
 619         p->buf++;
 620
 621         /* Have we filled the history buffer? */
 622         if (p->buf == p->historybuffer + HISTORY_SIZE) {
 623             memmove(p->historybuffer, p->buf, PREDICTOR_SIZE * sizeof(int32_t));
 624             p->buf = p->historybuffer;
 625         }
 626
 627         p->filterA[0] = currentA + ((p->filterA[0] * 31) >> 5);
 628         *(decoded0++) = p->filterA[0];
 629     }
 630
 631     p->lastA[0] = currentA;
 632 }
 633
 634 static void do_init_filter(APEFilter *f, int16_t * buf, int order)
 635 {
 636     f->coeffs = buf;
 637     f->historybuffer = buf + order;
 638     f->delay       = f->historybuffer + order * 2;
 639     f->adaptcoeffs = f->historybuffer + order;
 640
 641     memset(f->historybuffer, 0, (order * 2) * sizeof(int16_t));
 642     memset(f->coeffs, 0, order * sizeof(int16_t));
 643     f->avg = 0;
 644 }
 645
 646 static void init_filter(APEContext * ctx, APEFilter *f, int16_t * buf, int order)
 647 {
 648     do_init_filter(&f[0], buf, order);
 649     do_init_filter(&f[1], buf + order * 3 + HISTORY_SIZE, order);
 650 }
 651
 652 static void do_apply_filter(APEContext * ctx, int version, APEFilter *f, int32_t *data, int count, int order, int fracbits)
 653 {
 654     int res;
 655     int absres;
 656
 657     while (count--) {
 658         /* round fixedpoint scalar product */
 659         res = ctx->dsp.scalarproduct_and_madd_int16(f->coeffs, f->delay - order, f->adaptcoeffs - order, order, APESIGN(*data));
 660         res = (res + (1 << (fracbits - 1))) >> fracbits;
 661         res += *data;
 662         *data++ = res;
 663
 664         /* Update the output history */
 665         *f->delay++ = av_clip_int16(res);
 666
 667         if (version < 3980) {
 668             /* Version ??? to < 3.98 files (untested) */
 669             f->adaptcoeffs[0]  = (res == 0) ? 0 : ((res >> 28) & 8) - 4;
 670             f->adaptcoeffs[-4] >>= 1;
 671             f->adaptcoeffs[-8] >>= 1;
 672         } else {
 673             /* Version 3.98 and later files */
 674
 675             /* Update the adaption coefficients */
 676             absres = FFABS(res);
 677             if (absres)
 678                 *f->adaptcoeffs = ((res & (1<<31)) - (1<<30)) >> (25 + (absres <= f->avg*3) + (absres <= f->avg*4/3));
 679             else
 680                 *f->adaptcoeffs = 0;
 681
 682             f->avg += (absres - f->avg) / 16;
 683
 684             f->adaptcoeffs[-1] >>= 1;
 685             f->adaptcoeffs[-2] >>= 1;
 686             f->adaptcoeffs[-8] >>= 1;
 687         }
 688
 689         f->adaptcoeffs++;
 690
 691         /* Have we filled the history buffer? */
 692         if (f->delay == f->historybuffer + HISTORY_SIZE + (order * 2)) {
 693             memmove(f->historybuffer, f->delay - (order * 2),
 694                     (order * 2) * sizeof(int16_t));
 695             f->delay = f->historybuffer + order * 2;
 696             f->adaptcoeffs = f->historybuffer + order;
 697         }
 698     }
 699 }
 700
 701 static void apply_filter(APEContext * ctx, APEFilter *f,
 702                          int32_t * data0, int32_t * data1,
 703                          int count, int order, int fracbits)
 704 {
 705     do_apply_filter(ctx, ctx->fileversion, &f[0], data0, count, order, fracbits);
 706     if (data1)
 707         do_apply_filter(ctx, ctx->fileversion, &f[1], data1, count, order, fracbits);
 708 }
 709
 710 static void ape_apply_filters(APEContext * ctx, int32_t * decoded0,
 711                               int32_t * decoded1, int count)
 712 {
 713     int i;
 714
 715     for (i = 0; i < APE_FILTER_LEVELS; i++) {
 716         if (!ape_filter_orders[ctx->fset][i])
 717             break;
 718         apply_filter(ctx, ctx->filters[i], decoded0, decoded1, count, ape_filter_orders[ctx->fset][i], ape_filter_fracbits[ctx->fset][i]);
 719     }
 720 }
 721
 722 static void init_frame_decoder(APEContext * ctx)
 723 {
 724     int i;
 725     init_entropy_decoder(ctx);
 726     init_predictor_decoder(ctx);
 727
 728     for (i = 0; i < APE_FILTER_LEVELS; i++) {
 729         if (!ape_filter_orders[ctx->fset][i])
 730             break;
 731         init_filter(ctx, ctx->filters[i], ctx->filterbuf[i], ape_filter_orders[ctx->fset][i]);
 732     }
 733 }
 734
 735 static void ape_unpack_mono(APEContext * ctx, int count)
 736 {
 737     int32_t left;
 738     int32_t *decoded0 = ctx->decoded0;
 739     int32_t *decoded1 = ctx->decoded1;
 740
 741     if (ctx->frameflags & APE_FRAMECODE_STEREO_SILENCE) {
 742         entropy_decode(ctx, count, 0);
 743         /* We are pure silence, so we're done. */
 744         av_log(ctx->avctx, AV_LOG_DEBUG, "pure silence mono\n");
 745         return;
 746     }
 747
 748     entropy_decode(ctx, count, 0);
 749     ape_apply_filters(ctx, decoded0, NULL, count);
 750
 751     /* Now apply the predictor decoding */
 752     predictor_decode_mono(ctx, count);
 753
 754     /* Pseudo-stereo - just copy left channel to right channel */
 755     if (ctx->channels == 2) {
 756         while (count--) {
 757             left = *decoded0;
 758             *(decoded1++) = *(decoded0++) = left;
 759         }
 760     }
 761 }
 762
 763 static void ape_unpack_stereo(APEContext * ctx, int count)
 764 {
 765     int32_t left, right;
 766     int32_t *decoded0 = ctx->decoded0;
 767     int32_t *decoded1 = ctx->decoded1;
 768
 769     if (ctx->frameflags & APE_FRAMECODE_STEREO_SILENCE) {
 770         /* We are pure silence, so we're done. */
 771         av_log(ctx->avctx, AV_LOG_DEBUG, "pure silence stereo\n");
 772         return;
 773     }
 774
 775     entropy_decode(ctx, count, 1);
 776     ape_apply_filters(ctx, decoded0, decoded1, count);
 777
 778     /* Now apply the predictor decoding */
 779     predictor_decode_stereo(ctx, count);
 780
 781     /* Decorrelate and scale to output depth */
 782     while (count--) {
 783         left = *decoded1 - (*decoded0 / 2);
 784         right = left + *decoded0;
 785
 786         *(decoded0++) = left;
 787         *(decoded1++) = right;
 788     }
 789 }
 790
 791 static int ape_decode_frame(AVCodecContext * avctx,
 792                             void *data, int *data_size,
 793                             AVPacket *avpkt)
 794 {
 795     const uint8_t *buf = avpkt->data;
 796     int buf_size = avpkt->size;
 797     APEContext *s = avctx->priv_data;
 798     int16_t *samples = data;
 799     int nblocks;
 800     int i, n;
 801     int blockstodecode;
 802     int bytes_used;
 803
 804     if (buf_size == 0 && !s->samples) {
 805         *data_size = 0;
 806         return 0;
 807     }
 808
 809     /* should not happen but who knows */
 810     if (BLOCKS_PER_LOOP * 2 * avctx->channels > *data_size) {
 811         av_log (avctx, AV_LOG_ERROR, "Packet size is too big to be handled in lavc! (max is %d where you have %d)\n", *data_size, s->samples * 2 * avctx->channels);
 812         return -1;
 813     }
 814
 815     if(!s->samples){
 816         s->data = av_realloc(s->data, (buf_size + 3) & ~3);
 817         s->dsp.bswap_buf((uint32_t*)s->data, (const uint32_t*)buf, buf_size >> 2);
 818         s->ptr = s->last_ptr = s->data;
 819         s->data_end = s->data + buf_size;
 820
 821         nblocks = s->samples = bytestream_get_be32(&s->ptr);
 822         n =  bytestream_get_be32(&s->ptr);
 823         if(n < 0 || n > 3){
 824             av_log(avctx, AV_LOG_ERROR, "Incorrect offset passed\n");
 825             s->data = NULL;
 826             return -1;
 827         }
 828         s->ptr += n;
 829
 830         s->currentframeblocks = nblocks;
 831         buf += 4;
 832         if (s->samples <= 0) {
 833             *data_size = 0;
 834             return buf_size;
 835         }
 836
 837         memset(s->decoded0,  0, sizeof(s->decoded0));
 838         memset(s->decoded1,  0, sizeof(s->decoded1));
 839
 840         /* Initialize the frame decoder */
 841         init_frame_decoder(s);
 842     }
 843
 844     if (!s->data) {
 845         *data_size = 0;
 846         return buf_size;
 847     }
 848
 849     nblocks = s->samples;
 850     blockstodecode = FFMIN(BLOCKS_PER_LOOP, nblocks);
 851
 852     s->error=0;
 853
 854     if ((s->channels == 1) || (s->frameflags & APE_FRAMECODE_PSEUDO_STEREO))
 855         ape_unpack_mono(s, blockstodecode);
 856     else
 857         ape_unpack_stereo(s, blockstodecode);
 858     emms_c();
 859
 860     if(s->error || s->ptr > s->data_end){
 861         s->samples=0;
 862         av_log(avctx, AV_LOG_ERROR, "Error decoding frame\n");
 863         return -1;
 864     }
 865
 866     for (i = 0; i < blockstodecode; i++) {
 867         *samples++ = s->decoded0[i];
 868         if(s->channels == 2)
 869             *samples++ = s->decoded1[i];
 870     }
 871
 872     s->samples -= blockstodecode;
 873
 874     *data_size = blockstodecode * 2 * s->channels;
 875     bytes_used = s->samples ? s->ptr - s->last_ptr : buf_size;
 876     s->last_ptr = s->ptr;
 877     return bytes_used;
 878 }
 879
 880 AVCodec ape_decoder = {
 881     "ape",
 882     AVMEDIA_TYPE_AUDIO,
 883     CODEC_ID_APE,
 884     sizeof(APEContext),
 885     ape_decode_init,
 886     NULL,
 887     ape_decode_close,
 888     ape_decode_frame,
 889     .capabilities = CODEC_CAP_SUBFRAMES,
 890     .long_name = NULL_IF_CONFIG_SMALL("Monkey's Audio"),
 891 };