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/*

 * MPEG-4 ALS decoder

 * Copyright (c) 2009 Thilo Borgmann 

 *

 * 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

 */

/**

 * @file

 * MPEG-4 ALS decoder

 * @author Thilo Borgmann 

 */

#include "avcodec.h"

#include "get_bits.h"

#include "unary.h"

#include "mpeg4audio.h"

#include "bytestream.h"

#include "bgmc.h"

#include "dsputil.h"

#include "internal.h"

#include "libavutil/samplefmt.h"

#include "libavutil/crc.h"

#include 

/** Rice parameters and corresponding index offsets for decoding the

 *  indices of scaled PARCOR values. The table chosen is set globally

 *  by the encoder and stored in ALSSpecificConfig.

 */

static const int8_t parcor_rice_table[3][20][2] = {

    { {-52, 4}, {-29, 5}, {-31, 4}, { 19, 4}, {-16, 4},

      { 12, 3}, { -7, 3}, {  9, 3}, { -5, 3}, {  6, 3},

      { -4, 3}, {  3, 3}, { -3, 2}, {  3, 2}, { -2, 2},

      {  3, 2}, { -1, 2}, {  2, 2}, { -1, 2}, {  2, 2} },

    { {-58, 3}, {-42, 4}, {-46, 4}, { 37, 5}, {-36, 4},

      { 29, 4}, {-29, 4}, { 25, 4}, {-23, 4}, { 20, 4},

      {-17, 4}, { 16, 4}, {-12, 4}, { 12, 3}, {-10, 4},

      {  7, 3}, { -4, 4}, {  3, 3}, { -1, 3}, {  1, 3} },

    { {-59, 3}, {-45, 5}, {-50, 4}, { 38, 4}, {-39, 4},

      { 32, 4}, {-30, 4}, { 25, 3}, {-23, 3}, { 20, 3},

      {-20, 3}, { 16, 3}, {-13, 3}, { 10, 3}, { -7, 3},

      {  3, 3}, {  0, 3}, { -1, 3}, {  2, 3}, { -1, 2} }

};

/** Scaled PARCOR values used for the first two PARCOR coefficients.

 *  To be indexed by the Rice coded indices.

 *  Generated by: parcor_scaled_values[i] = 32 + ((i * (i+1)) << 7) - (1 << 20)

 *  Actual values are divided by 32 in order to be stored in 16 bits.

 */

static const int16_t parcor_scaled_values[] = {

    -1048544 / 32, -1048288 / 32, -1047776 / 32, -1047008 / 32,

    -1045984 / 32, -1044704 / 32, -1043168 / 32, -1041376 / 32,

    -1039328 / 32, -1037024 / 32, -1034464 / 32, -1031648 / 32,

    -1028576 / 32, -1025248 / 32, -1021664 / 32, -1017824 / 32,

    -1013728 / 32, -1009376 / 32, -1004768 / 32,  -999904 / 32,

     -994784 / 32,  -989408 / 32,  -983776 / 32,  -977888 / 32,

     -971744 / 32,  -965344 / 32,  -958688 / 32,  -951776 / 32,

     -944608 / 32,  -937184 / 32,  -929504 / 32,  -921568 / 32,

     -913376 / 32,  -904928 / 32,  -896224 / 32,  -887264 / 32,

     -878048 / 32,  -868576 / 32,  -858848 / 32,  -848864 / 32,

     -838624 / 32,  -828128 / 32,  -817376 / 32,  -806368 / 32,

     -795104 / 32,  -783584 / 32,  -771808 / 32,  -759776 / 32,

     -747488 / 32,  -734944 / 32,  -722144 / 32,  -709088 / 32,

     -695776 / 32,  -682208 / 32,  -668384 / 32,  -654304 / 32,

     -639968 / 32,  -625376 / 32,  -610528 / 32,  -595424 / 32,

     -580064 / 32,  -564448 / 32,  -548576 / 32,  -532448 / 32,

     -516064 / 32,  -499424 / 32,  -482528 / 32,  -465376 / 32,

     -447968 / 32,  -430304 / 32,  -412384 / 32,  -394208 / 32,

     -375776 / 32,  -357088 / 32,  -338144 / 32,  -318944 / 32,

     -299488 / 32,  -279776 / 32,  -259808 / 32,  -239584 / 32,

     -219104 / 32,  -198368 / 32,  -177376 / 32,  -156128 / 32,

     -134624 / 32,  -112864 / 32,   -90848 / 32,   -68576 / 32,

      -46048 / 32,   -23264 / 32,     -224 / 32,    23072 / 32,

       46624 / 32,    70432 / 32,    94496 / 32,   118816 / 32,

      143392 / 32,   168224 / 32,   193312 / 32,   218656 / 32,

      244256 / 32,   270112 / 32,   296224 / 32,   322592 / 32,

      349216 / 32,   376096 / 32,   403232 / 32,   430624 / 32,

      458272 / 32,   486176 / 32,   514336 / 32,   542752 / 32,

      571424 / 32,   600352 / 32,   629536 / 32,   658976 / 32,

      688672 / 32,   718624 / 32,   748832 / 32,   779296 / 32,

      810016 / 32,   840992 / 32,   872224 / 32,   903712 / 32,

      935456 / 32,   967456 / 32,   999712 / 32,  1032224 / 32

};

/** Gain values of p(0) for long-term prediction.

 *  To be indexed by the Rice coded indices.

 */

static const uint8_t ltp_gain_values [4][4] = {

    { 0,  8, 16,  24},

    {32, 40, 48,  56},

    {64, 70, 76,  82},

    {88, 92, 96, 100}

};

/** Inter-channel weighting factors for multi-channel correlation.

 *  To be indexed by the Rice coded indices.

 */

static const int16_t mcc_weightings[] = {

    204,  192,  179,  166,  153,  140,  128,  115,

    102,   89,   76,   64,   51,   38,   25,   12,

      0,  -12,  -25,  -38,  -51,  -64,  -76,  -89,

   -102, -115, -128, -140, -153, -166, -179, -192

};

/** Tail codes used in arithmetic coding using block Gilbert-Moore codes.

 */

static const uint8_t tail_code[16][6] = {

    { 74, 44, 25, 13,  7, 3},

    { 68, 42, 24, 13,  7, 3},

    { 58, 39, 23, 13,  7, 3},

    {126, 70, 37, 19, 10, 5},

    {132, 70, 37, 20, 10, 5},

    {124, 70, 38, 20, 10, 5},

    {120, 69, 37, 20, 11, 5},

    {116, 67, 37, 20, 11, 5},

    {108, 66, 36, 20, 10, 5},

    {102, 62, 36, 20, 10, 5},

    { 88, 58, 34, 19, 10, 5},

    {162, 89, 49, 25, 13, 7},

    {156, 87, 49, 26, 14, 7},

    {150, 86, 47, 26, 14, 7},

    {142, 84, 47, 26, 14, 7},

    {131, 79, 46, 26, 14, 7}

};

enum RA_Flag {

    RA_FLAG_NONE,

    RA_FLAG_FRAMES,

    RA_FLAG_HEADER

};

typedef struct {

    uint32_t samples;         ///< number of samples, 0xFFFFFFFF if unknown

    int resolution;           ///< 000 = 8-bit; 001 = 16-bit; 010 = 24-bit; 011 = 32-bit

    int floating;             ///< 1 = IEEE 32-bit floating-point, 0 = integer

    int msb_first;            ///< 1 = original CRC calculated on big-endian system, 0 = little-endian

    int frame_length;         ///< frame length for each frame (last frame may differ)

    int ra_distance;          ///< distance between RA frames (in frames, 0...255)

    enum RA_Flag ra_flag;     ///< indicates where the size of ra units is stored

    int adapt_order;          ///< adaptive order: 1 = on, 0 = off

    int coef_table;           ///< table index of Rice code parameters

    int long_term_prediction; ///< long term prediction (LTP): 1 = on, 0 = off

    int max_order;            ///< maximum prediction order (0..1023)

    int block_switching;      ///< number of block switching levels

    int bgmc;                 ///< "Block Gilbert-Moore Code": 1 = on, 0 = off (Rice coding only)

    int sb_part;              ///< sub-block partition

    int joint_stereo;         ///< joint stereo: 1 = on, 0 = off

    int mc_coding;            ///< extended inter-channel coding (multi channel coding): 1 = on, 0 = off

    int chan_config;          ///< indicates that a chan_config_info field is present

    int chan_sort;            ///< channel rearrangement: 1 = on, 0 = off

    int rlslms;               ///< use "Recursive Least Square-Least Mean Square" predictor: 1 = on, 0 = off

    int chan_config_info;     ///< mapping of channels to loudspeaker locations. Unused until setting channel configuration is implemented.

    int *chan_pos;            ///< original channel positions

    int crc_enabled;          ///< enable Cyclic Redundancy Checksum

} ALSSpecificConfig;

typedef struct {

    int stop_flag;

    int master_channel;

    int time_diff_flag;

    int time_diff_sign;

    int time_diff_index;

    int weighting[6];

} ALSChannelData;

typedef struct {

    AVCodecContext *avctx;

    ALSSpecificConfig sconf;

    GetBitContext gb;

    DSPContext dsp;

    const AVCRC *crc_table;

    uint32_t crc_org;               ///< CRC value of the original input data

    uint32_t crc;                   ///< CRC value calculated from decoded data

    unsigned int cur_frame_length;  ///< length of the current frame to decode

    unsigned int frame_id;          ///< the frame ID / number of the current frame

    unsigned int js_switch;         ///< if true, joint-stereo decoding is enforced

    unsigned int cs_switch;         ///< if true, channel rearrangement is done

    unsigned int num_blocks;        ///< number of blocks used in the current frame

    unsigned int s_max;             ///< maximum Rice parameter allowed in entropy coding

    uint8_t *bgmc_lut;              ///< pointer at lookup tables used for BGMC

    int *bgmc_lut_status;           ///< pointer at lookup table status flags used for BGMC

    int ltp_lag_length;             ///< number of bits used for ltp lag value

    int *const_block;               ///< contains const_block flags for all channels

    unsigned int *shift_lsbs;       ///< contains shift_lsbs flags for all channels

    unsigned int *opt_order;        ///< contains opt_order flags for all channels

    int *store_prev_samples;        ///< contains store_prev_samples flags for all channels

    int *use_ltp;                   ///< contains use_ltp flags for all channels

    int *ltp_lag;                   ///< contains ltp lag values for all channels

    int **ltp_gain;                 ///< gain values for ltp 5-tap filter for a channel

    int *ltp_gain_buffer;           ///< contains all gain values for ltp 5-tap filter

    int32_t **quant_cof;            ///< quantized parcor coefficients for a channel

    int32_t *quant_cof_buffer;      ///< contains all quantized parcor coefficients

    int32_t **lpc_cof;              ///< coefficients of the direct form prediction filter for a channel

    int32_t *lpc_cof_buffer;        ///< contains all coefficients of the direct form prediction filter

    int32_t *lpc_cof_reversed_buffer; ///< temporary buffer to set up a reversed versio of lpc_cof_buffer

    ALSChannelData **chan_data;     ///< channel data for multi-channel correlation

    ALSChannelData *chan_data_buffer; ///< contains channel data for all channels

    int *reverted_channels;         ///< stores a flag for each reverted channel

    int32_t *prev_raw_samples;      ///< contains unshifted raw samples from the previous block

    int32_t **raw_samples;          ///< decoded raw samples for each channel

    int32_t *raw_buffer;            ///< contains all decoded raw samples including carryover samples

    uint8_t *crc_buffer;            ///< buffer of byte order corrected samples used for CRC check

} ALSDecContext;

typedef struct {

    unsigned int block_length;      ///< number of samples within the block

    unsigned int ra_block;          ///< if true, this is a random access block

    int          *const_block;      ///< if true, this is a constant value block

    int          js_blocks;         ///< true if this block contains a difference signal

    unsigned int *shift_lsbs;       ///< shift of values for this block

    unsigned int *opt_order;        ///< prediction order of this block

    int          *store_prev_samples;///< if true, carryover samples have to be stored

    int          *use_ltp;          ///< if true, long-term prediction is used

    int          *ltp_lag;          ///< lag value for long-term prediction

    int          *ltp_gain;         ///< gain values for ltp 5-tap filter

    int32_t      *quant_cof;        ///< quantized parcor coefficients

    int32_t      *lpc_cof;          ///< coefficients of the direct form prediction

    int32_t      *raw_samples;      ///< decoded raw samples / residuals for this block

    int32_t      *prev_raw_samples; ///< contains unshifted raw samples from the previous block

    int32_t      *raw_other;        ///< decoded raw samples of the other channel of a channel pair

} ALSBlockData;

static av_cold void dprint_specific_config(ALSDecContext *ctx)

{

#ifdef DEBUG

    AVCodecContext *avctx    = ctx->avctx;

    ALSSpecificConfig *sconf = &ctx->sconf;

    av_dlog(avctx, "resolution = %i\n",           sconf->resolution);

    av_dlog(avctx, "floating = %i\n",             sconf->floating);

    av_dlog(avctx, "frame_length = %i\n",         sconf->frame_length);

    av_dlog(avctx, "ra_distance = %i\n",          sconf->ra_distance);

    av_dlog(avctx, "ra_flag = %i\n",              sconf->ra_flag);

    av_dlog(avctx, "adapt_order = %i\n",          sconf->adapt_order);

    av_dlog(avctx, "coef_table = %i\n",           sconf->coef_table);

    av_dlog(avctx, "long_term_prediction = %i\n", sconf->long_term_prediction);

    av_dlog(avctx, "max_order = %i\n",            sconf->max_order);

    av_dlog(avctx, "block_switching = %i\n",      sconf->block_switching);

    av_dlog(avctx, "bgmc = %i\n",                 sconf->bgmc);

    av_dlog(avctx, "sb_part = %i\n",              sconf->sb_part);

    av_dlog(avctx, "joint_stereo = %i\n",         sconf->joint_stereo);

    av_dlog(avctx, "mc_coding = %i\n",            sconf->mc_coding);

    av_dlog(avctx, "chan_config = %i\n",          sconf->chan_config);

    av_dlog(avctx, "chan_sort = %i\n",            sconf->chan_sort);

    av_dlog(avctx, "RLSLMS = %i\n",               sconf->rlslms);

    av_dlog(avctx, "chan_config_info = %i\n",     sconf->chan_config_info);

#endif

}

/** Read an ALSSpecificConfig from a buffer into the output struct.

 */

static av_cold int read_specific_config(ALSDecContext *ctx)

{

    GetBitContext gb;

    uint64_t ht_size;

    int i, config_offset;

    MPEG4AudioConfig m4ac;

    ALSSpecificConfig *sconf = &ctx->sconf;

    AVCodecContext *avctx    = ctx->avctx;

    uint32_t als_id, header_size, trailer_size;

    int ret;

    if ((ret = init_get_bits8(&gb, avctx->extradata, avctx->extradata_size)) < 0)

        return ret;

    config_offset = avpriv_mpeg4audio_get_config(&m4ac, avctx->extradata,

                                                 avctx->extradata_size * 8, 1);

    if (config_offset < 0)

        return AVERROR_INVALIDDATA;

    skip_bits_long(&gb, config_offset);

    if (get_bits_left(&gb) < (30 << 3))

        return AVERROR_INVALIDDATA;

    // read the fixed items

    als_id                      = get_bits_long(&gb, 32);

    avctx->sample_rate          = m4ac.sample_rate;

    skip_bits_long(&gb, 32); // sample rate already known

    sconf->samples              = get_bits_long(&gb, 32);

    avctx->channels             = m4ac.channels;

    skip_bits(&gb, 16);      // number of channels already known

    skip_bits(&gb, 3);       // skip file_type

    sconf->resolution           = get_bits(&gb, 3);

    sconf->floating             = get_bits1(&gb);

    sconf->msb_first            = get_bits1(&gb);

    sconf->frame_length         = get_bits(&gb, 16) + 1;

    sconf->ra_distance          = get_bits(&gb, 8);

    sconf->ra_flag              = get_bits(&gb, 2);

    sconf->adapt_order          = get_bits1(&gb);

    sconf->coef_table           = get_bits(&gb, 2);

    sconf->long_term_prediction = get_bits1(&gb);

    sconf->max_order            = get_bits(&gb, 10);

    sconf->block_switching      = get_bits(&gb, 2);

    sconf->bgmc                 = get_bits1(&gb);

    sconf->sb_part              = get_bits1(&gb);

    sconf->joint_stereo         = get_bits1(&gb);

    sconf->mc_coding            = get_bits1(&gb);

    sconf->chan_config          = get_bits1(&gb);

    sconf->chan_sort            = get_bits1(&gb);

    sconf->crc_enabled          = get_bits1(&gb);

    sconf->rlslms               = get_bits1(&gb);

    skip_bits(&gb, 5);       // skip 5 reserved bits

    skip_bits1(&gb);         // skip aux_data_enabled

    // check for ALSSpecificConfig struct

    if (als_id != MKBETAG('A','L','S','\0'))

        return AVERROR_INVALIDDATA;

    ctx->cur_frame_length = sconf->frame_length;

    // read channel config

    if (sconf->chan_config)

        sconf->chan_config_info = get_bits(&gb, 16);

    // TODO: use this to set avctx->channel_layout

    // read channel sorting

    if (sconf->chan_sort && avctx->channels > 1) {

        int chan_pos_bits = av_ceil_log2(avctx->channels);

        int bits_needed  = avctx->channels * chan_pos_bits + 7;

        if (get_bits_left(&gb) < bits_needed)

            return AVERROR_INVALIDDATA;

        if (!(sconf->chan_pos = av_malloc(avctx->channels * sizeof(*sconf->chan_pos))))

            return AVERROR(ENOMEM);

        ctx->cs_switch = 1;

        for (i = 0; i < avctx->channels; i++) {

            int idx;

            idx = get_bits(&gb, chan_pos_bits);

            if (idx >= avctx->channels) {

                av_log(avctx, AV_LOG_WARNING, "Invalid channel reordering.\n");

                ctx->cs_switch = 0;

                break;

            }

            sconf->chan_pos[idx] = i;

        }

        align_get_bits(&gb);

    }

    // read fixed header and trailer sizes,

    // if size = 0xFFFFFFFF then there is no data field!

    if (get_bits_left(&gb) < 64)

        return AVERROR_INVALIDDATA;

    header_size  = get_bits_long(&gb, 32);

    trailer_size = get_bits_long(&gb, 32);

    if (header_size  == 0xFFFFFFFF)

        header_size  = 0;

    if (trailer_size == 0xFFFFFFFF)

        trailer_size = 0;

    ht_size = ((int64_t)(header_size) + (int64_t)(trailer_size)) << 3;

    // skip the header and trailer data

    if (get_bits_left(&gb) < ht_size)

        return AVERROR_INVALIDDATA;

    if (ht_size > INT32_MAX)

        return AVERROR_PATCHWELCOME;

    skip_bits_long(&gb, ht_size);

    // initialize CRC calculation

    if (sconf->crc_enabled) {

        if (get_bits_left(&gb) < 32)

            return AVERROR_INVALIDDATA;

        if (avctx->err_recognition & (AV_EF_CRCCHECK|AV_EF_CAREFUL)) {

            ctx->crc_table = av_crc_get_table(AV_CRC_32_IEEE_LE);

            ctx->crc       = 0xFFFFFFFF;

            ctx->crc_org   = ~get_bits_long(&gb, 32);

        } else

            skip_bits_long(&gb, 32);

    }

    // no need to read the rest of ALSSpecificConfig (ra_unit_size & aux data)

    dprint_specific_config(ctx);

    return 0;

}

/** Check the ALSSpecificConfig for unsupported features.

 */

static int check_specific_config(ALSDecContext *ctx)

{

    ALSSpecificConfig *sconf = &ctx->sconf;

    int error = 0;

    // report unsupported feature and set error value

    #define MISSING_ERR(cond, str, errval)              \

    {                                                   \

        if (cond) {                                     \

            avpriv_report_missing_feature(ctx->avctx,   \

                                          str);         \

            error = errval;                             \

        }                                               \

    }

    MISSING_ERR(sconf->floating,  "Floating point decoding",     AVERROR_PATCHWELCOME);

    MISSING_ERR(sconf->rlslms,    "Adaptive RLS-LMS prediction", AVERROR_PATCHWELCOME);

    return error;

}

/** Parse the bs_info field to extract the block partitioning used in

 *  block switching mode, refer to ISO/IEC 14496-3, section 11.6.2.

 */

static void parse_bs_info(const uint32_t bs_info, unsigned int n,

                          unsigned int div, unsigned int **div_blocks,

                          unsigned int *num_blocks)

{

    if (n < 31 && ((bs_info << n) & 0x40000000)) {

        // if the level is valid and the investigated bit n is set

        // then recursively check both children at bits (2n+1) and (2n+2)

        n   *= 2;

        div += 1;

        parse_bs_info(bs_info, n + 1, div, div_blocks, num_blocks);

        parse_bs_info(bs_info, n + 2, div, div_blocks, num_blocks);

    } else {

        // else the bit is not set or the last level has been reached

        // (bit implicitly not set)

        **div_blocks = div;

        (*div_blocks)++;

        (*num_blocks)++;

    }

}

/** Read and decode a Rice codeword.

 */

static int32_t decode_rice(GetBitContext *gb, unsigned int k)

{

    int max = get_bits_left(gb) - k;

    int q   = get_unary(gb, 0, max);

    int r   = k ? get_bits1(gb) : !(q & 1);

    if (k > 1) {

        q <<= (k - 1);

        q  += get_bits_long(gb, k - 1);

    } else if (!k) {

        q >>= 1;

    }

    return r ? q : ~q;

}

/** Convert PARCOR coefficient k to direct filter coefficient.

 */

static void parcor_to_lpc(unsigned int k, const int32_t *par, int32_t *cof)

{

    int i, j;

    for (i = 0, j = k - 1; i < j; i++, j--) {

        int tmp1 = ((MUL64(par[k], cof[j]) + (1 << 19)) >> 20);

        cof[j]  += ((MUL64(par[k], cof[i]) + (1 << 19)) >> 20);

        cof[i]  += tmp1;

    }

    if (i == j)

        cof[i] += ((MUL64(par[k], cof[j]) + (1 << 19)) >> 20);

    cof[k] = par[k];

}

/** Read block switching field if necessary and set actual block sizes.

 *  Also assure that the block sizes of the last frame correspond to the

 *  actual number of samples.

 */

static void get_block_sizes(ALSDecContext *ctx, unsigned int *div_blocks,

                            uint32_t *bs_info)

{

    ALSSpecificConfig *sconf     = &ctx->sconf;

    GetBitContext *gb            = &ctx->gb;

    unsigned int *ptr_div_blocks = div_blocks;

    unsigned int b;

    if (sconf->block_switching) {

        unsigned int bs_info_len = 1 << (sconf->block_switching + 2);

        *bs_info = get_bits_long(gb, bs_info_len);

        *bs_info <<= (32 - bs_info_len);

    }

    ctx->num_blocks = 0;

    parse_bs_info(*bs_info, 0, 0, &ptr_div_blocks, &ctx->num_blocks);

    // The last frame may have an overdetermined block structure given in

    // the bitstream. In that case the defined block structure would need

    // more samples than available to be consistent.

    // The block structure is actually used but the block sizes are adapted

    // to fit the actual number of available samples.

    // Example: 5 samples, 2nd level block sizes: 2 2 2 2.

    // This results in the actual block sizes:    2 2 1 0.

    // This is not specified in 14496-3 but actually done by the reference

    // codec RM22 revision 2.

    // This appears to happen in case of an odd number of samples in the last

    // frame which is actually not allowed by the block length switching part

    // of 14496-3.

    // The ALS conformance files feature an odd number of samples in the last

    // frame.

    for (b = 0; b < ctx->num_blocks; b++)

        div_blocks[b] = ctx->sconf.frame_length >> div_blocks[b];

    if (ctx->cur_frame_length != ctx->sconf.frame_length) {

        unsigned int remaining = ctx->cur_frame_length;

        for (b = 0; b < ctx->num_blocks; b++) {

            if (remaining <= div_blocks[b]) {

                div_blocks[b] = remaining;

                ctx->num_blocks = b + 1;

                break;

            }

            remaining -= div_blocks[b];

        }

    }

}

/** Read the block data for a constant block

 */

static int read_const_block_data(ALSDecContext *ctx, ALSBlockData *bd)

{

    ALSSpecificConfig *sconf = &ctx->sconf;

    AVCodecContext *avctx    = ctx->avctx;

    GetBitContext *gb        = &ctx->gb;

    if (bd->block_length <= 0)

        return AVERROR_INVALIDDATA;

    *bd->raw_samples = 0;

    *bd->const_block = get_bits1(gb);    // 1 = constant value, 0 = zero block (silence)

    bd->js_blocks    = get_bits1(gb);

    // skip 5 reserved bits

    skip_bits(gb, 5);

    if (*bd->const_block) {

        unsigned int const_val_bits = sconf->floating ? 24 : avctx->bits_per_raw_sample;

        *bd->raw_samples = get_sbits_long(gb, const_val_bits);

    }

    // ensure constant block decoding by reusing this field

    *bd->const_block = 1;

    return 0;

}

/** Decode the block data for a constant block

 */

static void decode_const_block_data(ALSDecContext *ctx, ALSBlockData *bd)

{

    int      smp = bd->block_length - 1;

    int32_t  val = *bd->raw_samples;

    int32_t *dst = bd->raw_samples + 1;

    // write raw samples into buffer

    for (; smp; smp--)

        *dst++ = val;

}

/** Read the block data for a non-constant block

 */

static int read_var_block_data(ALSDecContext *ctx, ALSBlockData *bd)

{

    ALSSpecificConfig *sconf = &ctx->sconf;

    AVCodecContext *avctx    = ctx->avctx;

    GetBitContext *gb        = &ctx->gb;

    unsigned int k;

    unsigned int s[8];

    unsigned int sx[8];

    unsigned int sub_blocks, log2_sub_blocks, sb_length;

    unsigned int start      = 0;

    unsigned int opt_order;

    int          sb;

    int32_t      *quant_cof = bd->quant_cof;

    int32_t      *current_res;

    // ensure variable block decoding by reusing this field

    *bd->const_block = 0;

    *bd->opt_order  = 1;

    bd->js_blocks   = get_bits1(gb);

    opt_order       = *bd->opt_order;

    // determine the number of subblocks for entropy decoding

    if (!sconf->bgmc && !sconf->sb_part) {

        log2_sub_blocks = 0;

    } else {

        if (sconf->bgmc && sconf->sb_part)

            log2_sub_blocks = get_bits(gb, 2);

        else

            log2_sub_blocks = 2 * get_bits1(gb);

    }

    sub_blocks = 1 << log2_sub_blocks;

    // do not continue in case of a damaged stream since

    // block_length must be evenly divisible by sub_blocks

    if (bd->block_length & (sub_blocks - 1)) {

        av_log(avctx, AV_LOG_WARNING,

               "Block length is not evenly divisible by the number of subblocks.\n");

        return AVERROR_INVALIDDATA;

    }

    sb_length = bd->block_length >> log2_sub_blocks;

    if (sconf->bgmc) {

        s[0] = get_bits(gb, 8 + (sconf->resolution > 1));

        for (k = 1; k < sub_blocks; k++)

            s[k] = s[k - 1] + decode_rice(gb, 2);

        for (k = 0; k < sub_blocks; k++) {

            sx[k]   = s[k] & 0x0F;

            s [k] >>= 4;

        }

    } else {

        s[0] = get_bits(gb, 4 + (sconf->resolution > 1));

        for (k = 1; k < sub_blocks; k++)

            s[k] = s[k - 1] + decode_rice(gb, 0);

    }

    for (k = 1; k < sub_blocks; k++)

        if (s[k] > 32) {

            av_log(avctx, AV_LOG_ERROR, "k invalid for rice code.\n");

            return AVERROR_INVALIDDATA;

        }

    if (get_bits1(gb))

        *bd->shift_lsbs = get_bits(gb, 4) + 1;

    *bd->store_prev_samples = (bd->js_blocks && bd->raw_other) || *bd->shift_lsbs;

    if (!sconf->rlslms) {

        if (sconf->adapt_order) {

            int opt_order_length = av_ceil_log2(av_clip((bd->block_length >> 3) - 1,

                                                2, sconf->max_order + 1));

            *bd->opt_order       = get_bits(gb, opt_order_length);

            if (*bd->opt_order > sconf->max_order) {

                *bd->opt_order = sconf->max_order;

                av_log(avctx, AV_LOG_ERROR, "Predictor order too large.\n");

                return AVERROR_INVALIDDATA;

            }

        } else {

            *bd->opt_order = sconf->max_order;

        }

        opt_order = *bd->opt_order;

        if (opt_order) {

            int add_base;

            if (sconf->coef_table == 3) {

                add_base = 0x7F;

                // read coefficient 0

                quant_cof[0] = 32 * parcor_scaled_values[get_bits(gb, 7)];

                // read coefficient 1

                if (opt_order > 1)

                    quant_cof[1] = -32 * parcor_scaled_values[get_bits(gb, 7)];

                // read coefficients 2 to opt_order

                for (k = 2; k < opt_order; k++)

                    quant_cof[k] = get_bits(gb, 7);

            } else {

                int k_max;

                add_base = 1;

                // read coefficient 0 to 19

                k_max = FFMIN(opt_order, 20);

                for (k = 0; k < k_max; k++) {

                    int rice_param = parcor_rice_table[sconf->coef_table][k][1];

                    int offset     = parcor_rice_table[sconf->coef_table][k][0];

                    quant_cof[k] = decode_rice(gb, rice_param) + offset;

                    if (quant_cof[k] < -64 || quant_cof[k] > 63) {

                        av_log(avctx, AV_LOG_ERROR, "quant_cof %d is out of range.\n", quant_cof[k]);

                        return AVERROR_INVALIDDATA;

                    }

                }

                // read coefficients 20 to 126

                k_max = FFMIN(opt_order, 127);

                for (; k < k_max; k++)

                    quant_cof[k] = decode_rice(gb, 2) + (k & 1);

                // read coefficients 127 to opt_order

                for (; k < opt_order; k++)

                    quant_cof[k] = decode_rice(gb, 1);

                quant_cof[0] = 32 * parcor_scaled_values[quant_cof[0] + 64];

                if (opt_order > 1)

                    quant_cof[1] = -32 * parcor_scaled_values[quant_cof[1] + 64];

            }

            for (k = 2; k < opt_order; k++)

                quant_cof[k] = (quant_cof[k] << 14) + (add_base << 13);

        }

    }

    // read LTP gain and lag values

    if (sconf->long_term_prediction) {

        *bd->use_ltp = get_bits1(gb);

        if (*bd->use_ltp) {

            int r, c;

            bd->ltp_gain[0]   = decode_rice(gb, 1) << 3;

            bd->ltp_gain[1]   = decode_rice(gb, 2) << 3;

            r                 = get_unary(gb, 0, 3);

            c                 = get_bits(gb, 2);

            bd->ltp_gain[2]   = ltp_gain_values[r][c];

            bd->ltp_gain[3]   = decode_rice(gb, 2) << 3;

            bd->ltp_gain[4]   = decode_rice(gb, 1) << 3;

            *bd->ltp_lag      = get_bits(gb, ctx->ltp_lag_length);

            *bd->ltp_lag     += FFMAX(4, opt_order + 1);

        }

    }

    // read first value and residuals in case of a random access block

    if (bd->ra_block) {

        if (opt_order)

            bd->raw_samples[0] = decode_rice(gb, avctx->bits_per_raw_sample - 4);

        if (opt_order > 1)

            bd->raw_samples[1] = decode_rice(gb, FFMIN(s[0] + 3, ctx->s_max));

        if (opt_order > 2)

            bd->raw_samples[2] = decode_rice(gb, FFMIN(s[0] + 1, ctx->s_max));

        start = FFMIN(opt_order, 3);

    }

    // read all residuals

    if (sconf->bgmc) {

        int          delta[8];

        unsigned int k    [8];

        unsigned int b = av_clip((av_ceil_log2(bd->block_length) - 3) >> 1, 0, 5);

        // read most significant bits

        unsigned int high;

        unsigned int low;

        unsigned int value;

        ff_bgmc_decode_init(gb, &high, &low, &value);

        current_res = bd->raw_samples + start;

        for (sb = 0; sb < sub_blocks; sb++) {

            unsigned int sb_len  = sb_length - (sb ? 0 : start);

            k    [sb] = s[sb] > b ? s[sb] - b : 0;

            delta[sb] = 5 - s[sb] + k[sb];

            ff_bgmc_decode(gb, sb_len, current_res,

                        delta[sb], sx[sb], &high, &low, &value, ctx->bgmc_lut, ctx->bgmc_lut_status);

            current_res += sb_len;

        }

        ff_bgmc_decode_end(gb);

        // read least significant bits and tails

        current_res = bd->raw_samples + start;

        for (sb = 0; sb < sub_blocks; sb++, start = 0) {

            unsigned int cur_tail_code = tail_code[sx[sb]][delta[sb]];

            unsigned int cur_k         = k[sb];

            unsigned int cur_s         = s[sb];

            for (; start < sb_length; start++) {

                int32_t res = *current_res;

                if (res == cur_tail_code) {

                    unsigned int max_msb =   (2 + (sx[sb] > 2) + (sx[sb] > 10))

                                          << (5 - delta[sb]);

                    res = decode_rice(gb, cur_s);

                    if (res >= 0) {

                        res += (max_msb    ) << cur_k;

                    } else {

                        res -= (max_msb - 1) << cur_k;

                    }

                } else {

                    if (res > cur_tail_code)

                        res--;

                    if (res & 1)

                        res = -res;

                    res >>= 1;

                    if (cur_k) {

                        res <<= cur_k;

                        res  |= get_bits_long(gb, cur_k);

                    }

                }

                *current_res++ = res;

            }

        }

    } else {

        current_res = bd->raw_samples + start;

        for (sb = 0; sb < sub_blocks; sb++, start = 0)

            for (; start < sb_length; start++)

                *current_res++ = decode_rice(gb, s[sb]);

     }

    if (!sconf->mc_coding || ctx->js_switch)

        align_get_bits(gb);

    return 0;

}

/** Decode the block data for a non-constant block

 */

static int decode_var_block_data(ALSDecContext *ctx, ALSBlockData *bd)

{

    ALSSpecificConfig *sconf = &ctx->sconf;

    unsigned int block_length = bd->block_length;

    unsigned int smp = 0;

    unsigned int k;

    int opt_order             = *bd->opt_order;

    int sb;

    int64_t y;

    int32_t *quant_cof        = bd->quant_cof;

    int32_t *lpc_cof          = bd->lpc_cof;

    int32_t *raw_samples      = bd->raw_samples;

    int32_t *raw_samples_end  = bd->raw_samples + bd->block_length;

    int32_t *lpc_cof_reversed = ctx->lpc_cof_reversed_buffer;

    // reverse long-term prediction

    if (*bd->use_ltp) {

        int ltp_smp;

        for (ltp_smp = FFMAX(*bd->ltp_lag - 2, 0); ltp_smp < block_length; ltp_smp++) {

            int center = ltp_smp - *bd->ltp_lag;

            int begin  = FFMAX(0, center - 2);

            int end    = center + 3;

            int tab    = 5 - (end - begin);

            int base;

            y = 1 << 6;

            for (base = begin; base < end; base++, tab++)

                y += MUL64(bd->ltp_gain[tab], raw_samples[base]);

            raw_samples[ltp_smp] += y >> 7;

        }

    }

    // reconstruct all samples from residuals

    if (bd->ra_block) {

        for (smp = 0; smp < opt_order; smp++) {

            y = 1 << 19;

            for (sb = 0; sb < smp; sb++)

                y += MUL64(lpc_cof[sb], raw_samples[-(sb + 1)]);

            *raw_samples++ -= y >> 20;

            parcor_to_lpc(smp, quant_cof, lpc_cof);

        }

    } else {

        for (k = 0; k < opt_order; k++)

            parcor_to_lpc(k, quant_cof, lpc_cof);

        // store previous samples in case that they have to be altered

        if (*bd->store_prev_samples)

            memcpy(bd->prev_raw_samples, raw_samples - sconf->max_order,

                   sizeof(*bd->prev_raw_samples) * sconf->max_order);

        // reconstruct difference signal for prediction (joint-stereo)

        if (bd->js_blocks && bd->raw_other) {

            int32_t *left, *right;

            if (bd->raw_other > raw_samples) {  // D = R - L

                left  = raw_samples;

                right = bd->raw_other;

            } else {                                // D = R - L

                left  = bd->raw_other;

                right = raw_samples;

            }

            for (sb = -1; sb >= -sconf->max_order; sb--)

                raw_samples[sb] = right[sb] - left[sb];

        }

        // reconstruct shifted signal

        if (*bd->shift_lsbs)

            for (sb = -1; sb >= -sconf->max_order; sb--)

                raw_samples[sb] >>= *bd->shift_lsbs;

    }

    // reverse linear prediction coefficients for efficiency

    lpc_cof = lpc_cof + opt_order;

    for (sb = 0; sb < opt_order; sb++)

        lpc_cof_reversed[sb] = lpc_cof[-(sb + 1)];

    // reconstruct raw samples

    raw_samples = bd->raw_samples + smp;

    lpc_cof     = lpc_cof_reversed + opt_order;

    for (; raw_samples < raw_samples_end; raw_samples++) {

        y = 1 << 19;

        for (sb = -opt_order; sb < 0; sb++)

            y += MUL64(lpc_cof[sb], raw_samples[sb]);

        *raw_samples -= y >> 20;

    }

    raw_samples = bd->raw_samples;

    // restore previous samples in case that they have been altered

    if (*bd->store_prev_samples)

        memcpy(raw_samples - sconf->max_order, bd->prev_raw_samples,

               sizeof(*raw_samples) * sconf->max_order);

    return 0;

}

/** Read the block data.

 */

static int read_block(ALSDecContext *ctx, ALSBlockData *bd)

{

    int ret;

    GetBitContext *gb        = &ctx->gb;

    *bd->shift_lsbs = 0;

    // read block type flag and read the samples accordingly

    if (get_bits1(gb)) {

        ret = read_var_block_data(ctx, bd);

    } else {

        ret = read_const_block_data(ctx, bd);

    }

    return ret;

}

/** Decode the block data.

 */

static int decode_block(ALSDecContext *ctx, ALSBlockData *bd)

{

    unsigned int smp;

    int ret = 0;

    // read block type flag and read the samples accordingly

    if (*bd->const_block)

        decode_const_block_data(ctx, bd);

    else

        ret = decode_var_block_data(ctx, bd); // always return 0

    if (ret < 0)

        return ret;

    // TODO: read RLSLMS extension data

    if (*bd->shift_lsbs)

        for (smp = 0; smp < bd->block_length; smp++)

            bd->raw_samples[smp] <<= *bd->shift_lsbs;

    return 0;

}

/** Read and decode block data successively.

 */

static int read_decode_block(ALSDecContext *ctx, ALSBlockData *bd)

{

    int ret;

    if ((ret = read_block(ctx, bd)) < 0)

        return ret;

    return decode_block(ctx, bd);

}

/** Compute the number of samples left to decode for the current frame and

 *  sets these samples to zero.

 */

static void zero_remaining(unsigned int b, unsigned int b_max,

                           const unsigned int *div_blocks, int32_t *buf)

{

    unsigned int count = 0;

    while (b < b_max)

        count += div_blocks[b++];

    if (count)

        memset(buf, 0, sizeof(*buf) * count);

}

/** Decode blocks independently.

 */

static int decode_blocks_ind(ALSDecContext *ctx, unsigned int ra_frame,

                             unsigned int c, const unsigned int *div_blocks,

                             unsigned int *js_blocks)

{

    int ret;

    unsigned int b;

    ALSBlockData bd = { 0 };

    bd.ra_block         = ra_frame;

    bd.const_block      = ctx->const_block;

    bd.shift_lsbs       = ctx->shift_lsbs;

    bd.opt_order        = ctx->opt_order;

    bd.store_prev_samples = ctx->store_prev_samples;

    bd.use_ltp          = ctx->use_ltp;

    bd.ltp_lag          = ctx->ltp_lag;

    bd.ltp_gain         = ctx->ltp_gain[0];

    bd.quant_cof        = ctx->quant_cof[0];

    bd.lpc_cof          = ctx->lpc_cof[0];

    bd.prev_raw_samples = ctx->prev_raw_samples;

    bd.raw_samples      = ctx->raw_samples[c];

    for (b = 0; b < ctx->num_blocks; b++) {

        bd.block_length     = div_blocks[b];

        if ((ret = read_decode_block(ctx, &bd)) < 0) {

            // damaged block, write zero for the rest of the frame

            zero_remaining(b, ctx->num_blocks, div_blocks, bd.raw_samples);

            return ret;

        }

        bd.raw_samples += div_blocks[b];

        bd.ra_block     = 0;

    }

    return 0;

}

/** Decode blocks dependently.

 */

static int decode_blocks(ALSDecContext *ctx, unsigned int ra_frame,

                         unsigned int c, const unsigned int *div_blocks,

                         unsigned int *js_blocks)

{

    ALSSpecificConfig *sconf = &ctx->sconf;

    unsigned int offset = 0;

    unsigned int b;

    int ret;

    ALSBlockData bd[2] = { { 0 } };

    bd[0].ra_block         = ra_frame;

    bd[0].const_block      = ctx->const_block;

    bd[0].shift_lsbs       = ctx->shift_lsbs;

    bd[0].opt_order        = ctx->opt_order;

    bd[0].store_prev_samples = ctx->store_prev_samples;

    bd[0].use_ltp          = ctx->use_ltp;

    bd[0].ltp_lag          = ctx->ltp_lag;

    bd[0].ltp_gain         = ctx->ltp_gain[0];

    bd[0].quant_cof        = ctx->quant_cof[0];

    bd[0].lpc_cof          = ctx->lpc_cof[0];

    bd[0].prev_raw_samples = ctx->prev_raw_samples;

    bd[0].js_blocks        = *js_blocks;

    bd[1].ra_block         = ra_frame;

    bd[1].const_block      = ctx->const_block;

    bd[1].shift_lsbs       = ctx->shift_lsbs;

    bd[1].opt_order        = ctx->opt_order;

    bd[1].store_prev_samples = ctx->store_prev_samples;

    bd[1].use_ltp          = ctx->use_ltp;

    bd[1].ltp_lag          = ctx->ltp_lag;

    bd[1].ltp_gain         = ctx->ltp_gain[0];

    bd[1].quant_cof        = ctx->quant_cof[0];

    bd[1].lpc_cof          = ctx->lpc_cof[0];

    bd[1].prev_raw_samples = ctx->prev_raw_samples;

    bd[1].js_blocks        = *(js_blocks + 1);

    // decode all blocks

    for (b = 0; b < ctx->num_blocks; b++) {

        unsigned int s;