Monkey Audio decoder

Originally committed as revision 10484 to svn://svn.ffmpeg.org/ffmpeg/trunk

1 files changed, 922 insertions, 0 deletions

diff --git a/libavcodec/apedec.c b/libavcodec/apedec.c
new file mode 100644
index 0000000000..68358e1868
--- /dev/null
+++ b/libavcodec/apedec.c
@@ -0,0 +1,922 @@
+/*
+ * 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
+ */
+
+#define ALT_BITSTREAM_READER_LE
+#include "avcodec.h"
+#include "dsputil.h"
+#include "bitstream.h"
+#include "bytestream.h"
+
+/**
+ * @file apedec.c
+ * Monkey's Audio lossless audio decoder
+ */
+
+#define BLOCKS_PER_LOOP     4608
+#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 uint16_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 {
+    AVCodecContext *avctx;
+    DSPContext dsp;
+    int channels;
+    int samples;                             ///< samples left to decode in current frame
+
+    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
+    int currentframeblocks;                  ///< samples (per channel) in current frame
+    int blocksdecoded;                       ///< count of decoded samples in current frame
+    APEPredictor predictor;                  ///< predictor used for final reconstruction
+
+    int32_t decoded0[BLOCKS_PER_LOOP];       ///< decoded data for the first channel
+    int32_t decoded1[BLOCKS_PER_LOOP];       ///< decoded data for the second channel
+
+    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
+    uint8_t *ptr;                            ///< current position in frame data
+    uint8_t *last_ptr;                       ///< position where last 4608-sample block ended
+} APEContext;
+
+// TODO: dsputilize
+static inline void vector_add(int16_t * v1, int16_t * v2, int order)
+{
+    while (order--)
+       *v1++ += *v2++;
+}
+
+// TODO: dsputilize
+static inline void vector_sub(int16_t * v1, int16_t * v2, int order)
+{
+    while (order--)
+        *v1++ -= *v2++;
+}
+
+// TODO: dsputilize
+static inline int32_t scalarproduct(int16_t * v1, int16_t * v2, int order)
+{
+    int res = 0;
+
+    while (order--)
+        res += *v1++ * *v2++;
+
+    return res;
+}
+
+static 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 -1;
+    }
+    if (avctx->bits_per_sample != 16) {
+        av_log(avctx, AV_LOG_ERROR, "Only 16-bit samples are supported\n");
+        return -1;
+    }
+    if (avctx->channels > 2) {
+        av_log(avctx, AV_LOG_ERROR, "Only mono and stereo is supported\n");
+        return -1;
+    }
+    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) {
+        av_log(avctx, AV_LOG_ERROR, "Incorrect compression level %d\n", s->compression_level);
+        return -1;
+    }
+    s->fset = s->compression_level / 1000 - 1;
+    for (i = 0; i < APE_FILTER_LEVELS; i++) {
+        if (!ape_filter_orders[s->fset][i])
+            break;
+        s->filterbuf[i] = av_malloc((ape_filter_orders[s->fset][i] * 3 + HISTORY_SIZE) * 4);
+    }
+
+    dsputil_init(&s->dsp, avctx);
+    return 0;
+}
+
+static 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]);
+
+    return 0;
+}
+
+/**
+ * @defgroup rangecoder APE range decoder
+ * @{
+ */
+
+#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 = (ctx->rc.buffer << 8) | bytestream_get_byte(&ctx->ptr);
+        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 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 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 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 uint32_t counts_3970[65] = {
+        0, 14824, 28224, 39348, 47855, 53994, 58171, 60926,
+    62682, 63786, 64463, 64878, 65126, 65276, 65365, 65419,
+    65450, 65469, 65480, 65487, 65491, 65493, 65494, 65495,
+    65496, 65497, 65498, 65499, 65500, 65501, 65502, 65503,
+    65504, 65505, 65506, 65507, 65508, 65509, 65510, 65511,
+    65512, 65513, 65514, 65515, 65516, 65517, 65518, 65519,
+    65520, 65521, 65522, 65523, 65524, 65525, 65526, 65527,
+    65528, 65529, 65530, 65531, 65532, 65533, 65534, 65535,
+    65536
+};
+
+/**
+ * Probability ranges for symbols in Monkey Audio version 3.97
+ */
+static const uint16_t counts_diff_3970[64] = {
+    14824, 13400, 11124, 8507, 6139, 4177, 2755, 1756,
+    1104, 677, 415, 248, 150, 89, 54, 31,
+    19, 11, 7, 4, 2, 1, 1, 1,
+    1, 1, 1, 1, 1, 1, 1, 1,
+    1, 1, 1, 1, 1, 1, 1, 1,
+    1, 1, 1, 1, 1, 1, 1, 1,
+    1, 1, 1, 1, 1, 1, 1, 1,
+    1, 1, 1, 1, 1, 1, 1, 1
+};
+
+/**
+ * Fixed probabilities for symbols in Monkey Audio version 3.98
+ */
+static const uint32_t counts_3980[65] = {
+        0, 19578, 36160, 48417, 56323, 60899, 63265, 64435,
+    64971, 65232, 65351, 65416, 65447, 65466, 65476, 65482,
+    65485, 65488, 65490, 65491, 65492, 65493, 65494, 65495,
+    65496, 65497, 65498, 65499, 65500, 65501, 65502, 65503,
+    65504, 65505, 65506, 65507, 65508, 65509, 65510, 65511,
+    65512, 65513, 65514, 65515, 65516, 65517, 65518, 65519,
+    65520, 65521, 65522, 65523, 65524, 65525, 65526, 65527,
+    65528, 65529, 65530, 65531, 65532, 65533, 65534, 65535,
+    65536
+};
+
+/**
+ * Probability ranges for symbols in Monkey Audio version 3.98
+ */
+static const uint16_t counts_diff_3980[64] = {
+    19578, 16582, 12257, 7906, 4576, 2366, 1170, 536,
+    261, 119, 65, 31, 19, 10, 6, 3,
+    3, 2, 1, 1, 1, 1, 1, 1,
+    1, 1, 1, 1, 1, 1, 1, 1,
+    1, 1, 1, 1, 1, 1, 1, 1,
+    1, 1, 1, 1, 1, 1, 1, 1,
+    1, 1, 1, 1, 1, 1, 1, 1,
+    1, 1, 1, 1, 1, 1, 1, 1
+};
+
+/**
+ * Decode symbol
+ * @param counts probability range start position
+ * @param count_diffs probability range widths
+ */
+static inline int range_get_symbol(APEContext * ctx,
+                                   const uint32_t counts[],
+                                   const uint16_t counts_diff[])
+{
+    int symbol, cf;
+
+    cf = range_decode_culshift(ctx, 16);
+
+    /* 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, int x)
+{
+    rice->ksum += ((x + 1) / 2) - ((rice->ksum + 16) >> 5);
+
+    if (rice->k == 0)
+        rice->k = 1;
+    else if (rice->ksum < (1 << (rice->k + 4)))
+        rice->k--;
+    else if (rice->ksum >= (1 << (rice->k + 5)))
+        rice->k++;
+}
+
+static inline int ape_decode_value(APEContext * ctx, APERice *rice)
+{
+    int x, overflow;
+
+    if (ctx->fileversion < 3980) {
+        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 {
+            x = range_decode_bits(ctx, 16);
+            x |= (range_decode_bits(ctx, tmpk - 16) << 16);
+        }
+        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);
+        }
+
+        base = range_decode_culfreq(ctx, pivot);
+        range_decode_update(ctx, 1, base);
+
+        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->decoded0;
+    int32_t *decoded1 = ctx->decoded1;
+
+    ctx->blocksdecoded = blockstodecode;
+
+    if (ctx->frameflags & APE_FRAMECODE_STEREO_SILENCE) {
+        /* We are pure silence, just memset the output buffer. */
+        memset(decoded0, 0, blockstodecode * sizeof(int32_t));
+        memset(decoded1, 0, blockstodecode * sizeof(int32_t));
+    } else {
+        while (blockstodecode--) {
+            *decoded0++ = ape_decode_value(ctx, &ctx->riceY);
+            if (stereo)
+                *decoded1++ = ape_decode_value(ctx, &ctx->riceX);
+        }
+    }
+
+    if (ctx->blocksdecoded == ctx->currentframeblocks)
+        range_dec_normalize(ctx);   /* normalize to use up all bytes */
+}
+
+static void init_entropy_decoder(APEContext * ctx)
+{
+    /* Read the CRC */
+    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;
+
+        ctx->frameflags = bytestream_get_be32(&ctx->ptr);
+    }
+
+    /* Keep a count of the blocks decoded in this frame */
+    ctx->blocksdecoded = 0;
+
+    /* Initialise 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);
+}
+
+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(int32_t));
+    p->buf = p->historybuffer;
+
+    /* Initialise and zero the co-efficients */
+    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 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;
+
+    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);
+
+    if (!decoded) // no need updating filter coefficients
+        return p->filterA[filter];
+
+    if (decoded > 0) {
+        p->coeffsA[filter][0] -= p->buf[adaptA    ];
+        p->coeffsA[filter][1] -= p->buf[adaptA - 1];
+        p->coeffsA[filter][2] -= p->buf[adaptA - 2];
+        p->coeffsA[filter][3] -= p->buf[adaptA - 3];
+
+        p->coeffsB[filter][0] -= p->buf[adaptB    ];
+        p->coeffsB[filter][1] -= p->buf[adaptB - 1];
+        p->coeffsB[filter][2] -= p->buf[adaptB - 2];
+        p->coeffsB[filter][3] -= p->buf[adaptB - 3];
+        p->coeffsB[filter][4] -= p->buf[adaptB - 4];
+    } else {
+        p->coeffsA[filter][0] += p->buf[adaptA    ];
+        p->coeffsA[filter][1] += p->buf[adaptA - 1];
+        p->coeffsA[filter][2] += p->buf[adaptA - 2];
+        p->coeffsA[filter][3] += p->buf[adaptA - 3];
+
+        p->coeffsB[filter][0] += p->buf[adaptB    ];
+        p->coeffsB[filter][1] += p->buf[adaptB - 1];
+        p->coeffsB[filter][2] += p->buf[adaptB - 2];
+        p->coeffsB[filter][3] += p->buf[adaptB - 3];
+        p->coeffsB[filter][4] += p->buf[adaptB - 4];
+    }
+    return p->filterA[filter];
+}
+
+static void predictor_decode_stereo(APEContext * ctx, int count)
+{
+    int32_t predictionA, predictionB;
+    APEPredictor *p = &ctx->predictor;
+    int32_t *decoded0 = ctx->decoded0;
+    int32_t *decoded1 = ctx->decoded1;
+
+    while (count--) {
+        /* Predictor Y */
+        predictionA = predictor_update_filter(p, *decoded0, 0, YDELAYA, YDELAYB, YADAPTCOEFFSA, YADAPTCOEFFSB);
+        predictionB = predictor_update_filter(p, *decoded1, 1, XDELAYA, XDELAYB, XADAPTCOEFFSA, XADAPTCOEFFSB);
+        *(decoded0++) = predictionA;
+        *(decoded1++) = predictionB;
+
+        /* Combined */
+        p->buf++;
+
+        /* Have we filled the history buffer? */
+        if (p->buf == p->historybuffer + HISTORY_SIZE) {
+            memmove(p->historybuffer, p->buf, PREDICTOR_SIZE * sizeof(int32_t));
+            p->buf = p->historybuffer;
+        }
+    }
+}
+
+static void predictor_decode_mono(APEContext * ctx, int count)
+{
+    APEPredictor *p = &ctx->predictor;
+    int32_t *decoded0 = ctx->decoded0;
+    int32_t predictionA, currentA, A;
+
+    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]);
+
+        if (A > 0) {
+            p->coeffsA[0][0] -= p->buf[YADAPTCOEFFSA    ];
+            p->coeffsA[0][1] -= p->buf[YADAPTCOEFFSA - 1];
+            p->coeffsA[0][2] -= p->buf[YADAPTCOEFFSA - 2];
+            p->coeffsA[0][3] -= p->buf[YADAPTCOEFFSA - 3];
+        } else if (A < 0) {
+            p->coeffsA[0][0] += p->buf[YADAPTCOEFFSA    ];
+            p->coeffsA[0][1] += p->buf[YADAPTCOEFFSA - 1];
+            p->coeffsA[0][2] += p->buf[YADAPTCOEFFSA - 2];
+            p->coeffsA[0][3] += p->buf[YADAPTCOEFFSA - 3];
+        }
+
+        p->buf++;
+
+        /* Have we filled the history buffer? */
+        if (p->buf == p->historybuffer + HISTORY_SIZE) {
+            memmove(p->historybuffer, p->buf, PREDICTOR_SIZE * sizeof(int32_t));
+            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(int16_t));
+    memset(f->coeffs, 0, order * sizeof(int16_t));
+    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 inline void do_apply_filter(int version, APEFilter *f, int32_t *data, int count, int order, int fracbits)
+{
+    int res;
+    int absres;
+
+    while (count--) {
+        /* round fixedpoint scalar product */
+        res = (scalarproduct(f->delay - order, f->coeffs, order) + (1 << (fracbits - 1))) >> fracbits;
+
+        if (*data < 0)
+            vector_add(f->coeffs, f->adaptcoeffs - order, order);
+        else if (*data > 0)
+            vector_sub(f->coeffs, f->adaptcoeffs - order, order);
+
+        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 = (res < 0 ? -res : res);
+
+            if (absres > (f->avg * 3))
+                *f->adaptcoeffs = ((res >> 25) & 64) - 32;
+            else if (absres > (f->avg * 4) / 3)
+                *f->adaptcoeffs = ((res >> 26) & 32) - 16;
+            else if (absres > 0)
+                *f->adaptcoeffs = ((res >> 27) & 16) - 8;
+            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(int16_t));
+            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->fileversion, &f[0], data0, count, order, fracbits);
+    if (data1)
+        do_apply_filter(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 void init_frame_decoder(APEContext * ctx)
+{
+    int i;
+    init_entropy_decoder(ctx);
+    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]);
+    }
+}
+
+static void ape_unpack_mono(APEContext * ctx, int count)
+{
+    int32_t left;
+    int32_t *decoded0 = ctx->decoded0;
+    int32_t *decoded1 = ctx->decoded1;
+
+    if (ctx->frameflags & APE_FRAMECODE_STEREO_SILENCE) {
+        entropy_decode(ctx, count, 0);
+        /* 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, decoded0, 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) {
+        while (count--) {
+            left = *decoded0;
+            *(decoded1++) = *(decoded0++) = left;
+        }
+    }
+}
+
+static void ape_unpack_stereo(APEContext * ctx, int count)
+{
+    int32_t left, right;
+    int32_t *decoded0 = ctx->decoded0;
+    int32_t *decoded1 = ctx->decoded1;
+
+    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 *data_size,
+                            uint8_t * buf, int buf_size)
+{
+    APEContext *s = avctx->priv_data;
+    int16_t *samples = data;
+    int nblocks;
+    int i, n;
+    int blockstodecode;
+    int bytes_used;
+
+    if (buf_size == 0 && !s->samples) {
+        *data_size = 0;
+        return 0;
+    }
+
+    /* should not happen but who knows */
+    if (BLOCKS_PER_LOOP * 2 * avctx->channels > *data_size) {
+        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);
+        return -1;
+    }
+
+    if(!s->samples){
+        s->data = av_realloc(s->data, (buf_size + 3) & ~3);
+        s->dsp.bswap_buf(s->data, buf, buf_size >> 2);
+        s->ptr = s->last_ptr = s->data;
+        s->data_end = s->data + buf_size;
+
+        nblocks = s->samples = bytestream_get_be32(&s->ptr);
+        n =  bytestream_get_be32(&s->ptr);
+        if(n < 0 || n > 3){
+            av_log(avctx, AV_LOG_ERROR, "Incorrect offset passed\n");
+            s->data = NULL;
+            return -1;
+        }
+        s->ptr += n;
+
+        s->currentframeblocks = nblocks;
+        buf += 4;
+        if (s->samples <= 0) {
+            *data_size = 0;
+            return buf_size;
+        }
+
+        memset(s->decoded0,  0, sizeof(s->decoded0));
+        memset(s->decoded1,  0, sizeof(s->decoded1));
+
+        /* Initialize the frame decoder */
+        init_frame_decoder(s);
+    }
+
+    if (!s->data) {
+        *data_size = 0;
+        return buf_size;
+    }
+
+    nblocks = s->samples;
+    blockstodecode = FFMIN(BLOCKS_PER_LOOP, nblocks);
+
+    if ((s->channels == 1) || (s->frameflags & APE_FRAMECODE_PSEUDO_STEREO))
+        ape_unpack_mono(s, blockstodecode);
+    else
+        ape_unpack_stereo(s, blockstodecode);
+
+    for (i = 0; i < blockstodecode; i++) {
+        *samples++ = s->decoded0[i];
+        if(s->channels == 2)
+            *samples++ = s->decoded1[i];
+    }
+
+    s->samples -= blockstodecode;
+
+    *data_size = blockstodecode * 2 * s->channels;
+    bytes_used = s->samples ? s->ptr - s->last_ptr : buf_size;
+    s->last_ptr = s->ptr;
+    return bytes_used;
+}
+
+AVCodec ape_decoder = {
+    "ape",
+    CODEC_TYPE_AUDIO,
+    CODEC_ID_APE,
+    sizeof(APEContext),
+    ape_decode_init,
+    NULL,
+    ape_decode_close,
+    ape_decode_frame,
+};