/*
  * Monkey's Audio lossless audio decoder
  * Copyright (c) 2007 Benjamin Zores <ben@geexbox.org>
  *  based upon libdemac from Dave Chapman.
  *
  * This file is part of FFmpeg.
  *
  * FFmpeg is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Lesser General Public
  * License as published by the Free Software Foundation; either
  * version 2.1 of the License, or (at your option) any later version.
  *
  * FFmpeg is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  * Lesser General Public License for more details.
  *
  * You should have received a copy of the GNU Lesser General Public
  * License along with FFmpeg; if not, write to the Free Software
  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  */
 

 #include "libavutil/avassert.h"
 #include "libavutil/channel_layout.h"
 #include "libavutil/opt.h"

 #include "avcodec.h"
 #include "dsputil.h"
 #include "bytestream.h"

 #include "internal.h"

 
 /**

  * @file

  * Monkey's Audio lossless audio decoder
  */
 
 #define MAX_CHANNELS        2
 #define MAX_BYTESPERSAMPLE  3
 
 #define APE_FRAMECODE_MONO_SILENCE    1
 #define APE_FRAMECODE_STEREO_SILENCE  3
 #define APE_FRAMECODE_PSEUDO_STEREO   4
 
 #define HISTORY_SIZE 512
 #define PREDICTOR_ORDER 8
 /** Total size of all predictor histories */
 #define PREDICTOR_SIZE 50
 
 #define YDELAYA (18 + PREDICTOR_ORDER*4)
 #define YDELAYB (18 + PREDICTOR_ORDER*3)
 #define XDELAYA (18 + PREDICTOR_ORDER*2)
 #define XDELAYB (18 + PREDICTOR_ORDER)
 
 #define YADAPTCOEFFSA 18
 #define XADAPTCOEFFSA 14
 #define YADAPTCOEFFSB 10
 #define XADAPTCOEFFSB 5
 
 /**
  * Possible compression levels
  * @{
  */
 enum APECompressionLevel {
     COMPRESSION_LEVEL_FAST       = 1000,
     COMPRESSION_LEVEL_NORMAL     = 2000,
     COMPRESSION_LEVEL_HIGH       = 3000,
     COMPRESSION_LEVEL_EXTRA_HIGH = 4000,
     COMPRESSION_LEVEL_INSANE     = 5000
 };
 /** @} */
 
 #define APE_FILTER_LEVELS 3
 
 /** Filter orders depending on compression level */
 static const uint16_t ape_filter_orders[5][APE_FILTER_LEVELS] = {
     {  0,   0,    0 },
     { 16,   0,    0 },
     { 64,   0,    0 },
     { 32, 256,    0 },
     { 16, 256, 1280 }
 };
 
 /** Filter fraction bits depending on compression level */

 static const uint8_t ape_filter_fracbits[5][APE_FILTER_LEVELS] = {

     {  0,  0,  0 },
     { 11,  0,  0 },
     { 11,  0,  0 },
     { 10, 13,  0 },
     { 11, 13, 15 }
 };
 
 
 /** Filters applied to the decoded data */
 typedef struct APEFilter {
     int16_t *coeffs;        ///< actual coefficients used in filtering
     int16_t *adaptcoeffs;   ///< adaptive filter coefficients used for correcting of actual filter coefficients
     int16_t *historybuffer; ///< filter memory
     int16_t *delay;         ///< filtered values
 
     int avg;
 } APEFilter;
 
 typedef struct APERice {
     uint32_t k;
     uint32_t ksum;
 } APERice;
 
 typedef struct APERangecoder {
     uint32_t low;           ///< low end of interval
     uint32_t range;         ///< length of interval
     uint32_t help;          ///< bytes_to_follow resp. intermediate value
     unsigned int buffer;    ///< buffer for input/output
 } APERangecoder;
 
 /** Filter histories */
 typedef struct APEPredictor {
     int32_t *buf;
 
     int32_t lastA[2];
 
     int32_t filterA[2];
     int32_t filterB[2];
 
     int32_t coeffsA[2][4];  ///< adaption coefficients
     int32_t coeffsB[2][5];  ///< adaption coefficients
     int32_t historybuffer[HISTORY_SIZE + PREDICTOR_SIZE];
 } APEPredictor;
 
 /** Decoder context */
 typedef struct APEContext {

     AVClass *class;                          ///< class for AVOptions

     AVCodecContext *avctx;

     AVFrame frame;

     DSPContext dsp;
     int channels;
     int samples;                             ///< samples left to decode in current frame

     int bps;

 
     int fileversion;                         ///< codec version, very important in decoding process
     int compression_level;                   ///< compression levels
     int fset;                                ///< which filter set to use (calculated from compression level)
     int flags;                               ///< global decoder flags
 
     uint32_t CRC;                            ///< frame CRC
     int frameflags;                          ///< frame flags
     APEPredictor predictor;                  ///< predictor used for final reconstruction
 

     int32_t *decoded_buffer;
     int decoded_size;
     int32_t *decoded[MAX_CHANNELS];          ///< decoded data for each channel

     int blocks_per_loop;                     ///< maximum number of samples to decode for each call

 
     int16_t* filterbuf[APE_FILTER_LEVELS];   ///< filter memory
 
     APERangecoder rc;                        ///< rangecoder used to decode actual values
     APERice riceX;                           ///< rice code parameters for the second channel
     APERice riceY;                           ///< rice code parameters for the first channel
     APEFilter filters[APE_FILTER_LEVELS][2]; ///< filters used for reconstruction
 
     uint8_t *data;                           ///< current frame data
     uint8_t *data_end;                       ///< frame data end

     int data_size;                           ///< frame data allocated size

     const uint8_t *ptr;                      ///< current position in frame data

 
     int error;

 } APEContext;
 
 // TODO: dsputilize
 

 static av_cold int ape_decode_close(AVCodecContext *avctx)

 {
     APEContext *s = avctx->priv_data;
     int i;
 
     for (i = 0; i < APE_FILTER_LEVELS; i++)
         av_freep(&s->filterbuf[i]);
 

     av_freep(&s->decoded_buffer);

     av_freep(&s->data);

     s->decoded_size = s->data_size = 0;

     return 0;
 }
 

 static av_cold int ape_decode_init(AVCodecContext *avctx)

 {
     APEContext *s = avctx->priv_data;
     int i;
 
     if (avctx->extradata_size != 6) {
         av_log(avctx, AV_LOG_ERROR, "Incorrect extradata\n");

         return AVERROR(EINVAL);

     }
     if (avctx->channels > 2) {
         av_log(avctx, AV_LOG_ERROR, "Only mono and stereo is supported\n");

         return AVERROR(EINVAL);

     }

     s->bps = avctx->bits_per_coded_sample;
     switch (s->bps) {
     case 8:

         avctx->sample_fmt = AV_SAMPLE_FMT_U8P;

         break;
     case 16:

         avctx->sample_fmt = AV_SAMPLE_FMT_S16P;

         break;
     case 24:

         avctx->sample_fmt = AV_SAMPLE_FMT_S32P;

         break;
     default:
         av_log_ask_for_sample(avctx, "Unsupported bits per coded sample %d\n",
                               s->bps);
         return AVERROR_PATCHWELCOME;
     }

     s->avctx             = avctx;
     s->channels          = avctx->channels;
     s->fileversion       = AV_RL16(avctx->extradata);
     s->compression_level = AV_RL16(avctx->extradata + 2);
     s->flags             = AV_RL16(avctx->extradata + 4);
 

     av_log(avctx, AV_LOG_DEBUG, "Compression Level: %d - Flags: %d\n",
            s->compression_level, s->flags);

     if (s->compression_level % 1000 || s->compression_level > COMPRESSION_LEVEL_INSANE || !s->compression_level) {

         av_log(avctx, AV_LOG_ERROR, "Incorrect compression level %d\n",
                s->compression_level);

         return AVERROR_INVALIDDATA;

     }
     s->fset = s->compression_level / 1000 - 1;
     for (i = 0; i < APE_FILTER_LEVELS; i++) {
         if (!ape_filter_orders[s->fset][i])
             break;

         FF_ALLOC_OR_GOTO(avctx, s->filterbuf[i],
                          (ape_filter_orders[s->fset][i] * 3 + HISTORY_SIZE) * 4,
                          filter_alloc_fail);

     }
 

     ff_dsputil_init(&s->dsp, avctx);

     avctx->channel_layout = (avctx->channels==2) ? AV_CH_LAYOUT_STEREO : AV_CH_LAYOUT_MONO;

 
     avcodec_get_frame_defaults(&s->frame);
     avctx->coded_frame = &s->frame;
 

     return 0;

 filter_alloc_fail:
     ape_decode_close(avctx);
     return AVERROR(ENOMEM);

 }
 
 /**

  * @name APE range decoding functions

  * @{
  */
 
 #define CODE_BITS    32
 #define TOP_VALUE    ((unsigned int)1 << (CODE_BITS-1))
 #define SHIFT_BITS   (CODE_BITS - 9)
 #define EXTRA_BITS   ((CODE_BITS-2) % 8 + 1)
 #define BOTTOM_VALUE (TOP_VALUE >> 8)
 
 /** Start the decoder */

 static inline void range_start_decoding(APEContext *ctx)

 {
     ctx->rc.buffer = bytestream_get_byte(&ctx->ptr);
     ctx->rc.low    = ctx->rc.buffer >> (8 - EXTRA_BITS);
     ctx->rc.range  = (uint32_t) 1 << EXTRA_BITS;
 }
 
 /** Perform normalization */

 static inline void range_dec_normalize(APEContext *ctx)

 {
     while (ctx->rc.range <= BOTTOM_VALUE) {

         ctx->rc.buffer <<= 8;

         if(ctx->ptr < ctx->data_end) {

             ctx->rc.buffer += *ctx->ptr;

             ctx->ptr++;
         } else {
             ctx->error = 1;
         }

         ctx->rc.low    = (ctx->rc.low << 8)    | ((ctx->rc.buffer >> 1) & 0xFF);
         ctx->rc.range  <<= 8;
     }
 }
 
 /**
  * Calculate culmulative frequency for next symbol. Does NO update!

  * @param ctx decoder context

  * @param tot_f is the total frequency or (code_value)1<<shift
  * @return the culmulative frequency
  */

 static inline int range_decode_culfreq(APEContext *ctx, int tot_f)

 {
     range_dec_normalize(ctx);
     ctx->rc.help = ctx->rc.range / tot_f;
     return ctx->rc.low / ctx->rc.help;
 }
 
 /**
  * Decode value with given size in bits

  * @param ctx decoder context

  * @param shift number of bits to decode
  */

 static inline int range_decode_culshift(APEContext *ctx, int shift)

 {
     range_dec_normalize(ctx);
     ctx->rc.help = ctx->rc.range >> shift;
     return ctx->rc.low / ctx->rc.help;
 }
 
 
 /**
  * Update decoding state

  * @param ctx decoder context

  * @param sy_f the interval length (frequency of the symbol)
  * @param lt_f the lower end (frequency sum of < symbols)
  */

 static inline void range_decode_update(APEContext *ctx, int sy_f, int lt_f)

 {
     ctx->rc.low  -= ctx->rc.help * lt_f;
     ctx->rc.range = ctx->rc.help * sy_f;
 }
 
 /** Decode n bits (n <= 16) without modelling */

 static inline int range_decode_bits(APEContext *ctx, int n)

 {
     int sym = range_decode_culshift(ctx, n);
     range_decode_update(ctx, 1, sym);
     return sym;
 }
 
 
 #define MODEL_ELEMENTS 64
 
 /**
  * Fixed probabilities for symbols in Monkey Audio version 3.97
  */

 static const uint16_t counts_3970[22] = {

         0, 14824, 28224, 39348, 47855, 53994, 58171, 60926,
     62682, 63786, 64463, 64878, 65126, 65276, 65365, 65419,

     65450, 65469, 65480, 65487, 65491, 65493,

 };
 
 /**
  * Probability ranges for symbols in Monkey Audio version 3.97
  */

 static const uint16_t counts_diff_3970[21] = {

     14824, 13400, 11124, 8507, 6139, 4177, 2755, 1756,
     1104, 677, 415, 248, 150, 89, 54, 31,

     19, 11, 7, 4, 2,

 };
 
 /**
  * Fixed probabilities for symbols in Monkey Audio version 3.98
  */

 static const uint16_t counts_3980[22] = {

         0, 19578, 36160, 48417, 56323, 60899, 63265, 64435,
     64971, 65232, 65351, 65416, 65447, 65466, 65476, 65482,

     65485, 65488, 65490, 65491, 65492, 65493,

 };
 
 /**
  * Probability ranges for symbols in Monkey Audio version 3.98
  */

 static const uint16_t counts_diff_3980[21] = {

     19578, 16582, 12257, 7906, 4576, 2366, 1170, 536,
     261, 119, 65, 31, 19, 10, 6, 3,

     3, 2, 1, 1, 1,

 };
 
 /**
  * Decode symbol

  * @param ctx decoder context

  * @param counts probability range start position

  * @param counts_diff probability range widths

  */

 static inline int range_get_symbol(APEContext *ctx,

                                    const uint16_t counts[],

                                    const uint16_t counts_diff[])
 {
     int symbol, cf;
 
     cf = range_decode_culshift(ctx, 16);
 

     if(cf > 65492){
         symbol= cf - 65535 + 63;
         range_decode_update(ctx, 1, cf);
         if(cf > 65535)
             ctx->error=1;
         return symbol;
     }

     /* figure out the symbol inefficiently; a binary search would be much better */
     for (symbol = 0; counts[symbol + 1] <= cf; symbol++);
 
     range_decode_update(ctx, counts_diff[symbol], counts[symbol]);
 
     return symbol;
 }
 /** @} */ // group rangecoder
 

 static inline void update_rice(APERice *rice, unsigned int x)

 {

     int lim = rice->k ? (1 << (rice->k + 4)) : 0;

     rice->ksum += ((x + 1) / 2) - ((rice->ksum + 16) >> 5);
 

     if (rice->ksum < lim)

         rice->k--;
     else if (rice->ksum >= (1 << (rice->k + 5)))
         rice->k++;
 }
 

 static inline int ape_decode_value(APEContext *ctx, APERice *rice)

 {

     unsigned int x, overflow;

     if (ctx->fileversion < 3990) {

         int tmpk;
 
         overflow = range_get_symbol(ctx, counts_3970, counts_diff_3970);
 
         if (overflow == (MODEL_ELEMENTS - 1)) {
             tmpk = range_decode_bits(ctx, 5);
             overflow = 0;
         } else
             tmpk = (rice->k < 1) ? 0 : rice->k - 1;
 
         if (tmpk <= 16)
             x = range_decode_bits(ctx, tmpk);

         else if (tmpk <= 32) {

             x = range_decode_bits(ctx, 16);
             x |= (range_decode_bits(ctx, tmpk - 16) << 16);

         } else {

             av_log(ctx->avctx, AV_LOG_ERROR, "Too many bits: %d\n", tmpk);
             return AVERROR_INVALIDDATA;

         }
         x += overflow << tmpk;
     } else {
         int base, pivot;
 
         pivot = rice->ksum >> 5;
         if (pivot == 0)
             pivot = 1;
 
         overflow = range_get_symbol(ctx, counts_3980, counts_diff_3980);
 
         if (overflow == (MODEL_ELEMENTS - 1)) {
             overflow  = range_decode_bits(ctx, 16) << 16;
             overflow |= range_decode_bits(ctx, 16);
         }
 

         if (pivot < 0x10000) {
             base = range_decode_culfreq(ctx, pivot);
             range_decode_update(ctx, 1, base);
         } else {
             int base_hi = pivot, base_lo;
             int bbits = 0;
 
             while (base_hi & ~0xFFFF) {
                 base_hi >>= 1;
                 bbits++;
             }
             base_hi = range_decode_culfreq(ctx, base_hi + 1);
             range_decode_update(ctx, 1, base_hi);
             base_lo = range_decode_culfreq(ctx, 1 << bbits);
             range_decode_update(ctx, 1, base_lo);
 
             base = (base_hi << bbits) + base_lo;
         }

 
         x = base + overflow * pivot;
     }
 
     update_rice(rice, x);
 
     /* Convert to signed */
     if (x & 1)
         return (x >> 1) + 1;
     else
         return -(x >> 1);
 }
 

 static void entropy_decode(APEContext *ctx, int blockstodecode, int stereo)

 {

     int32_t *decoded0 = ctx->decoded[0];
     int32_t *decoded1 = ctx->decoded[1];

     while (blockstodecode--) {
         *decoded0++ = ape_decode_value(ctx, &ctx->riceY);
         if (stereo)
             *decoded1++ = ape_decode_value(ctx, &ctx->riceX);

     }
 }
 

 static int init_entropy_decoder(APEContext *ctx)

 {
     /* Read the CRC */

     if (ctx->data_end - ctx->ptr < 6)
         return AVERROR_INVALIDDATA;

     ctx->CRC = bytestream_get_be32(&ctx->ptr);
 
     /* Read the frame flags if they exist */
     ctx->frameflags = 0;
     if ((ctx->fileversion > 3820) && (ctx->CRC & 0x80000000)) {
         ctx->CRC &= ~0x80000000;
 

         if (ctx->data_end - ctx->ptr < 6)
             return AVERROR_INVALIDDATA;

         ctx->frameflags = bytestream_get_be32(&ctx->ptr);
     }
 

     /* Initialize the rice structs */

     ctx->riceX.k = 10;
     ctx->riceX.ksum = (1 << ctx->riceX.k) * 16;
     ctx->riceY.k = 10;
     ctx->riceY.ksum = (1 << ctx->riceY.k) * 16;
 
     /* The first 8 bits of input are ignored. */
     ctx->ptr++;
 
     range_start_decoding(ctx);

 
     return 0;

 }
 
 static const int32_t initial_coeffs[4] = {
     360, 317, -109, 98
 };
 

 static void init_predictor_decoder(APEContext *ctx)

 {
     APEPredictor *p = &ctx->predictor;
 
     /* Zero the history buffers */

     memset(p->historybuffer, 0, PREDICTOR_SIZE * sizeof(*p->historybuffer));

     p->buf = p->historybuffer;
 

     /* Initialize and zero the coefficients */

     memcpy(p->coeffsA[0], initial_coeffs, sizeof(initial_coeffs));
     memcpy(p->coeffsA[1], initial_coeffs, sizeof(initial_coeffs));
     memset(p->coeffsB, 0, sizeof(p->coeffsB));
 
     p->filterA[0] = p->filterA[1] = 0;
     p->filterB[0] = p->filterB[1] = 0;
     p->lastA[0]   = p->lastA[1]   = 0;
 }
 
 /** Get inverse sign of integer (-1 for positive, 1 for negative and 0 for zero) */
 static inline int APESIGN(int32_t x) {
     return (x < 0) - (x > 0);
 }
 

 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)

 {

     int32_t predictionA, predictionB, sign;

 
     p->buf[delayA]     = p->lastA[filter];
     p->buf[adaptA]     = APESIGN(p->buf[delayA]);
     p->buf[delayA - 1] = p->buf[delayA] - p->buf[delayA - 1];
     p->buf[adaptA - 1] = APESIGN(p->buf[delayA - 1]);
 
     predictionA = p->buf[delayA    ] * p->coeffsA[filter][0] +
                   p->buf[delayA - 1] * p->coeffsA[filter][1] +
                   p->buf[delayA - 2] * p->coeffsA[filter][2] +
                   p->buf[delayA - 3] * p->coeffsA[filter][3];
 
     /*  Apply a scaled first-order filter compression */
     p->buf[delayB]     = p->filterA[filter ^ 1] - ((p->filterB[filter] * 31) >> 5);
     p->buf[adaptB]     = APESIGN(p->buf[delayB]);
     p->buf[delayB - 1] = p->buf[delayB] - p->buf[delayB - 1];
     p->buf[adaptB - 1] = APESIGN(p->buf[delayB - 1]);
     p->filterB[filter] = p->filterA[filter ^ 1];
 
     predictionB = p->buf[delayB    ] * p->coeffsB[filter][0] +
                   p->buf[delayB - 1] * p->coeffsB[filter][1] +
                   p->buf[delayB - 2] * p->coeffsB[filter][2] +
                   p->buf[delayB - 3] * p->coeffsB[filter][3] +
                   p->buf[delayB - 4] * p->coeffsB[filter][4];
 
     p->lastA[filter] = decoded + ((predictionA + (predictionB >> 1)) >> 10);
     p->filterA[filter] = p->lastA[filter] + ((p->filterA[filter] * 31) >> 5);
 

     sign = APESIGN(decoded);
     p->coeffsA[filter][0] += p->buf[adaptA    ] * sign;
     p->coeffsA[filter][1] += p->buf[adaptA - 1] * sign;
     p->coeffsA[filter][2] += p->buf[adaptA - 2] * sign;
     p->coeffsA[filter][3] += p->buf[adaptA - 3] * sign;
     p->coeffsB[filter][0] += p->buf[adaptB    ] * sign;
     p->coeffsB[filter][1] += p->buf[adaptB - 1] * sign;
     p->coeffsB[filter][2] += p->buf[adaptB - 2] * sign;
     p->coeffsB[filter][3] += p->buf[adaptB - 3] * sign;
     p->coeffsB[filter][4] += p->buf[adaptB - 4] * sign;

 
     return p->filterA[filter];
 }
 

 static void predictor_decode_stereo(APEContext *ctx, int count)

 {
     APEPredictor *p = &ctx->predictor;

     int32_t *decoded0 = ctx->decoded[0];
     int32_t *decoded1 = ctx->decoded[1];

 
     while (count--) {
         /* Predictor Y */

         *decoded0 = predictor_update_filter(p, *decoded0, 0, YDELAYA, YDELAYB,
                                             YADAPTCOEFFSA, YADAPTCOEFFSB);

         decoded0++;

         *decoded1 = predictor_update_filter(p, *decoded1, 1, XDELAYA, XDELAYB,
                                             XADAPTCOEFFSA, XADAPTCOEFFSB);

         decoded1++;

 
         /* Combined */
         p->buf++;
 
         /* Have we filled the history buffer? */
         if (p->buf == p->historybuffer + HISTORY_SIZE) {

             memmove(p->historybuffer, p->buf,
                     PREDICTOR_SIZE * sizeof(*p->historybuffer));

             p->buf = p->historybuffer;
         }
     }
 }
 

 static void predictor_decode_mono(APEContext *ctx, int count)

 {
     APEPredictor *p = &ctx->predictor;

     int32_t *decoded0 = ctx->decoded[0];

     int32_t predictionA, currentA, A, sign;

 
     currentA = p->lastA[0];
 
     while (count--) {
         A = *decoded0;
 
         p->buf[YDELAYA] = currentA;
         p->buf[YDELAYA - 1] = p->buf[YDELAYA] - p->buf[YDELAYA - 1];
 
         predictionA = p->buf[YDELAYA    ] * p->coeffsA[0][0] +
                       p->buf[YDELAYA - 1] * p->coeffsA[0][1] +
                       p->buf[YDELAYA - 2] * p->coeffsA[0][2] +
                       p->buf[YDELAYA - 3] * p->coeffsA[0][3];
 
         currentA = A + (predictionA >> 10);
 
         p->buf[YADAPTCOEFFSA]     = APESIGN(p->buf[YDELAYA    ]);
         p->buf[YADAPTCOEFFSA - 1] = APESIGN(p->buf[YDELAYA - 1]);
 

         sign = APESIGN(A);
         p->coeffsA[0][0] += p->buf[YADAPTCOEFFSA    ] * sign;
         p->coeffsA[0][1] += p->buf[YADAPTCOEFFSA - 1] * sign;
         p->coeffsA[0][2] += p->buf[YADAPTCOEFFSA - 2] * sign;
         p->coeffsA[0][3] += p->buf[YADAPTCOEFFSA - 3] * sign;

 
         p->buf++;
 
         /* Have we filled the history buffer? */
         if (p->buf == p->historybuffer + HISTORY_SIZE) {

             memmove(p->historybuffer, p->buf,
                     PREDICTOR_SIZE * sizeof(*p->historybuffer));

             p->buf = p->historybuffer;
         }
 
         p->filterA[0] = currentA + ((p->filterA[0] * 31) >> 5);
         *(decoded0++) = p->filterA[0];
     }
 
     p->lastA[0] = currentA;
 }
 

 static void do_init_filter(APEFilter *f, int16_t *buf, int order)

 {
     f->coeffs = buf;
     f->historybuffer = buf + order;
     f->delay       = f->historybuffer + order * 2;
     f->adaptcoeffs = f->historybuffer + order;
 

     memset(f->historybuffer, 0, (order * 2) * sizeof(*f->historybuffer));
     memset(f->coeffs, 0, order * sizeof(*f->coeffs));

     f->avg = 0;
 }
 

 static void init_filter(APEContext *ctx, APEFilter *f, int16_t *buf, int order)

 {
     do_init_filter(&f[0], buf, order);
     do_init_filter(&f[1], buf + order * 3 + HISTORY_SIZE, order);
 }
 

 static void do_apply_filter(APEContext *ctx, int version, APEFilter *f,
                             int32_t *data, int count, int order, int fracbits)

 {
     int res;
     int absres;
 
     while (count--) {
         /* round fixedpoint scalar product */

         res = ctx->dsp.scalarproduct_and_madd_int16(f->coeffs, f->delay - order,
                                                     f->adaptcoeffs - order,
                                                     order, APESIGN(*data));

         res = (res + (1 << (fracbits - 1))) >> fracbits;

         res += *data;
         *data++ = res;
 
         /* Update the output history */
         *f->delay++ = av_clip_int16(res);
 
         if (version < 3980) {
             /* Version ??? to < 3.98 files (untested) */
             f->adaptcoeffs[0]  = (res == 0) ? 0 : ((res >> 28) & 8) - 4;
             f->adaptcoeffs[-4] >>= 1;
             f->adaptcoeffs[-8] >>= 1;
         } else {
             /* Version 3.98 and later files */
 
             /* Update the adaption coefficients */

             absres = FFABS(res);
             if (absres)

                 *f->adaptcoeffs = ((res & (-1<<31)) ^ (-1<<30)) >>

                                   (25 + (absres <= f->avg*3) + (absres <= f->avg*4/3));

             else
                 *f->adaptcoeffs = 0;
 
             f->avg += (absres - f->avg) / 16;
 
             f->adaptcoeffs[-1] >>= 1;
             f->adaptcoeffs[-2] >>= 1;
             f->adaptcoeffs[-8] >>= 1;
         }
 
         f->adaptcoeffs++;
 
         /* Have we filled the history buffer? */
         if (f->delay == f->historybuffer + HISTORY_SIZE + (order * 2)) {
             memmove(f->historybuffer, f->delay - (order * 2),

                     (order * 2) * sizeof(*f->historybuffer));

             f->delay = f->historybuffer + order * 2;
             f->adaptcoeffs = f->historybuffer + order;
         }
     }
 }
 

 static void apply_filter(APEContext *ctx, APEFilter *f,
                          int32_t *data0, int32_t *data1,

                          int count, int order, int fracbits)
 {

     do_apply_filter(ctx, ctx->fileversion, &f[0], data0, count, order, fracbits);

     if (data1)

         do_apply_filter(ctx, ctx->fileversion, &f[1], data1, count, order, fracbits);

 }
 

 static void ape_apply_filters(APEContext *ctx, int32_t *decoded0,
                               int32_t *decoded1, int count)

 {
     int i;
 
     for (i = 0; i < APE_FILTER_LEVELS; i++) {
         if (!ape_filter_orders[ctx->fset][i])
             break;

         apply_filter(ctx, ctx->filters[i], decoded0, decoded1, count,
                      ape_filter_orders[ctx->fset][i],
                      ape_filter_fracbits[ctx->fset][i]);

     }
 }
 

 static int init_frame_decoder(APEContext *ctx)

 {

     int i, ret;
     if ((ret = init_entropy_decoder(ctx)) < 0)
         return ret;

     init_predictor_decoder(ctx);
 
     for (i = 0; i < APE_FILTER_LEVELS; i++) {
         if (!ape_filter_orders[ctx->fset][i])
             break;

         init_filter(ctx, ctx->filters[i], ctx->filterbuf[i],
                     ape_filter_orders[ctx->fset][i]);

     }

     return 0;

 }
 

 static void ape_unpack_mono(APEContext *ctx, int count)

 {
     if (ctx->frameflags & APE_FRAMECODE_STEREO_SILENCE) {
         /* We are pure silence, so we're done. */
         av_log(ctx->avctx, AV_LOG_DEBUG, "pure silence mono\n");
         return;
     }
 
     entropy_decode(ctx, count, 0);

     ape_apply_filters(ctx, ctx->decoded[0], NULL, count);

 
     /* Now apply the predictor decoding */
     predictor_decode_mono(ctx, count);
 
     /* Pseudo-stereo - just copy left channel to right channel */
     if (ctx->channels == 2) {

         memcpy(ctx->decoded[1], ctx->decoded[0], count * sizeof(*ctx->decoded[1]));

     }
 }
 

 static void ape_unpack_stereo(APEContext *ctx, int count)

 {
     int32_t left, right;

     int32_t *decoded0 = ctx->decoded[0];
     int32_t *decoded1 = ctx->decoded[1];

 
     if (ctx->frameflags & APE_FRAMECODE_STEREO_SILENCE) {
         /* We are pure silence, so we're done. */
         av_log(ctx->avctx, AV_LOG_DEBUG, "pure silence stereo\n");
         return;
     }
 
     entropy_decode(ctx, count, 1);
     ape_apply_filters(ctx, decoded0, decoded1, count);
 
     /* Now apply the predictor decoding */
     predictor_decode_stereo(ctx, count);
 
     /* Decorrelate and scale to output depth */
     while (count--) {
         left = *decoded1 - (*decoded0 / 2);
         right = left + *decoded0;
 
         *(decoded0++) = left;
         *(decoded1++) = right;
     }
 }
 

 static int ape_decode_frame(AVCodecContext *avctx, void *data,
                             int *got_frame_ptr, AVPacket *avpkt)

 {

     const uint8_t *buf = avpkt->data;

     APEContext *s = avctx->priv_data;

     uint8_t *sample8;
     int16_t *sample16;
     int32_t *sample24;

     int i, ch, ret;

     int blockstodecode;

     /* this should never be negative, but bad things will happen if it is, so
        check it just to make sure. */
     av_assert0(s->samples >= 0);
 

     if(!s->samples){

         uint32_t nblocks, offset;

         int buf_size;

         if (!avpkt->size) {

             *got_frame_ptr = 0;

             return 0;
         }

         if (avpkt->size < 8) {

             av_log(avctx, AV_LOG_ERROR, "Packet is too small\n");
             return AVERROR_INVALIDDATA;
         }

         buf_size = avpkt->size & ~3;
         if (buf_size != avpkt->size) {
             av_log(avctx, AV_LOG_WARNING, "packet size is not a multiple of 4. "
                    "extra bytes at the end will be skipped.\n");
         }

         av_fast_malloc(&s->data, &s->data_size, buf_size);

         if (!s->data)

             return AVERROR(ENOMEM);

         s->dsp.bswap_buf((uint32_t*)s->data, (const uint32_t*)buf, buf_size >> 2);

         s->ptr = s->data;

         s->data_end = s->data + buf_size;
 

         nblocks = bytestream_get_be32(&s->ptr);

         offset  = bytestream_get_be32(&s->ptr);
         if (offset > 3) {

             av_log(avctx, AV_LOG_ERROR, "Incorrect offset passed\n");
             s->data = NULL;

             return AVERROR_INVALIDDATA;

         }

         if (s->data_end - s->ptr < offset) {
             av_log(avctx, AV_LOG_ERROR, "Packet is too small\n");
             return AVERROR_INVALIDDATA;
         }

         s->ptr += offset;

         if (!nblocks || nblocks > INT_MAX) {
             av_log(avctx, AV_LOG_ERROR, "Invalid sample count: %u.\n", nblocks);
             return AVERROR_INVALIDDATA;

         }

         s->samples = nblocks;

 
         /* Initialize the frame decoder */

         if (init_frame_decoder(s) < 0) {
             av_log(avctx, AV_LOG_ERROR, "Error reading frame header\n");
             return AVERROR_INVALIDDATA;
         }

     }
 
     if (!s->data) {

         *got_frame_ptr = 0;

         return avpkt->size;

     }
 

     blockstodecode = FFMIN(s->blocks_per_loop, s->samples);

     /* reallocate decoded sample buffer if needed */
     av_fast_malloc(&s->decoded_buffer, &s->decoded_size,
                    2 * FFALIGN(blockstodecode, 8) * sizeof(*s->decoded_buffer));
     if (!s->decoded_buffer)
         return AVERROR(ENOMEM);
     memset(s->decoded_buffer, 0, s->decoded_size);
     s->decoded[0] = s->decoded_buffer;
     s->decoded[1] = s->decoded_buffer + FFALIGN(blockstodecode, 8);

     /* get output buffer */
     s->frame.nb_samples = blockstodecode;

     if ((ret = ff_get_buffer(avctx, &s->frame)) < 0) {

         av_log(avctx, AV_LOG_ERROR, "get_buffer() failed\n");
         return ret;

     }

     s->error=0;
 

     if ((s->channels == 1) || (s->frameflags & APE_FRAMECODE_PSEUDO_STEREO))
         ape_unpack_mono(s, blockstodecode);
     else
         ape_unpack_stereo(s, blockstodecode);

     emms_c();

     if (s->error) {

         s->samples=0;
         av_log(avctx, AV_LOG_ERROR, "Error decoding frame\n");

         return AVERROR_INVALIDDATA;

     }
 

     switch (s->bps) {
     case 8:

         for (ch = 0; ch < s->channels; ch++) {
             sample8 = (uint8_t *)s->frame.data[ch];
             for (i = 0; i < blockstodecode; i++)
                 *sample8++ = (s->decoded[ch][i] + 0x80) & 0xff;

         }
         break;
     case 16:

         for (ch = 0; ch < s->channels; ch++) {
             sample16 = (int16_t *)s->frame.data[ch];
             for (i = 0; i < blockstodecode; i++)
                 *sample16++ = s->decoded[ch][i];

         }
         break;
     case 24:

         for (ch = 0; ch < s->channels; ch++) {
             sample24 = (int32_t *)s->frame.data[ch];
             for (i = 0; i < blockstodecode; i++)
                 *sample24++ = s->decoded[ch][i] << 8;

         }
         break;

     }
 
     s->samples -= blockstodecode;
 

     *got_frame_ptr   = 1;
     *(AVFrame *)data = s->frame;
 

     return !s->samples ? avpkt->size : 0;

 }
 

 static void ape_flush(AVCodecContext *avctx)
 {
     APEContext *s = avctx->priv_data;
     s->samples= 0;
 }
 

 #define OFFSET(x) offsetof(APEContext, x)
 #define PAR (AV_OPT_FLAG_DECODING_PARAM | AV_OPT_FLAG_AUDIO_PARAM)
 static const AVOption options[] = {

     { "max_samples", "maximum number of samples decoded per call",             OFFSET(blocks_per_loop), AV_OPT_TYPE_INT,   { .i64 = 4608 },    1,       INT_MAX, PAR, "max_samples" },

     { "all",         "no maximum. decode all samples for each packet at once", 0,                       AV_OPT_TYPE_CONST, { .i64 = INT_MAX }, INT_MIN, INT_MAX, PAR, "max_samples" },

     { NULL},
 };
 
 static const AVClass ape_decoder_class = {
     .class_name = "APE decoder",
     .item_name  = av_default_item_name,
     .option     = options,
     .version    = LIBAVUTIL_VERSION_INT,
 };
 

 AVCodec ff_ape_decoder = {

     .name           = "ape",
     .type           = AVMEDIA_TYPE_AUDIO,

     .id             = AV_CODEC_ID_APE,

     .priv_data_size = sizeof(APEContext),
     .init           = ape_decode_init,
     .close          = ape_decode_close,
     .decode         = ape_decode_frame,

     .capabilities   = CODEC_CAP_SUBFRAMES | CODEC_CAP_DELAY | CODEC_CAP_DR1,

     .flush          = ape_flush,
     .long_name      = NULL_IF_CONFIG_SMALL("Monkey's Audio"),

     .sample_fmts    = (const enum AVSampleFormat[]) { AV_SAMPLE_FMT_U8P,
                                                       AV_SAMPLE_FMT_S16P,
                                                       AV_SAMPLE_FMT_S32P,
                                                       AV_SAMPLE_FMT_NONE },

     .priv_class     = &ape_decoder_class,

 };