/*****************************************************************************
 * flac.c: flac packetizer module.
 *****************************************************************************
 * Copyright (C) 1999-2001 VLC authors and VideoLAN
 * $Id: ecf854f0eb36c6aa1906304b02d802b07c03be3d $
 *
 * Authors: Gildas Bazin <gbazin@videolan.org>
 *          Sigmund Augdal Helberg <dnumgis@videolan.org>
 *
 * This program 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.
 *
 * This program 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 this program; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin Street, Fifth Floor, Boston MA 02110-1301, USA.
 *****************************************************************************/

/*****************************************************************************
 * Preamble
 *****************************************************************************/

#ifdef HAVE_CONFIG_H
# include "config.h"
#endif

#include <vlc_common.h>
#include <vlc_plugin.h>
#include <vlc_codec.h>

#include <vlc_block_helper.h>
#include <vlc_bits.h>
#include "packetizer_helper.h"

/*****************************************************************************
 * Module descriptor
 *****************************************************************************/
static int  Open (vlc_object_t *);
static void Close(vlc_object_t *);

vlc_module_begin()
    set_category(CAT_SOUT)
    set_subcategory(SUBCAT_SOUT_PACKETIZER)
    set_description(N_("Flac audio packetizer"))
    set_capability("packetizer", 50)
    set_callbacks(Open, Close)
vlc_module_end()

/*****************************************************************************
 * decoder_sys_t : FLAC decoder descriptor
 *****************************************************************************/
#define MAX_FLAC_HEADER_SIZE 16
#define MIN_FLAC_FRAME_SIZE ((48+(8 + 4 + 1*4)+16)/8)
struct decoder_sys_t
{
    /*
     * Input properties
     */
    int i_state;

    block_bytestream_t bytestream;

    /*
     * FLAC properties
     */
    struct
    {
        unsigned min_blocksize, max_blocksize;
        unsigned min_framesize, max_framesize;
        unsigned sample_rate;
        unsigned channels;
        unsigned bits_per_sample;

    } stream_info;
    bool b_stream_info;

    /*
     * Common properties
     */
    mtime_t i_pts;
    mtime_t i_duration;

    int i_frame_length;
    size_t i_frame_size;
    uint16_t crc;
    unsigned int i_rate, i_channels, i_bits_per_sample;
};

static const int pi_channels_maps[9] =
{
    0,
    AOUT_CHAN_CENTER,
    AOUT_CHAN_LEFT | AOUT_CHAN_RIGHT,
    AOUT_CHAN_CENTER | AOUT_CHAN_LEFT | AOUT_CHAN_RIGHT,
    AOUT_CHAN_LEFT | AOUT_CHAN_RIGHT | AOUT_CHAN_REARLEFT
     | AOUT_CHAN_REARRIGHT,
    AOUT_CHAN_LEFT | AOUT_CHAN_RIGHT | AOUT_CHAN_CENTER
     | AOUT_CHAN_REARLEFT | AOUT_CHAN_REARRIGHT,
    AOUT_CHAN_LEFT | AOUT_CHAN_RIGHT | AOUT_CHAN_CENTER
     | AOUT_CHAN_REARLEFT | AOUT_CHAN_REARRIGHT | AOUT_CHAN_LFE,
    AOUT_CHAN_LEFT | AOUT_CHAN_RIGHT | AOUT_CHAN_CENTER
     | AOUT_CHAN_REARLEFT | AOUT_CHAN_REARRIGHT | AOUT_CHAN_MIDDLELEFT
     | AOUT_CHAN_MIDDLERIGHT,
    AOUT_CHAN_LEFT | AOUT_CHAN_RIGHT | AOUT_CHAN_CENTER | AOUT_CHAN_REARLEFT
     | AOUT_CHAN_REARRIGHT | AOUT_CHAN_MIDDLELEFT | AOUT_CHAN_MIDDLERIGHT
     | AOUT_CHAN_LFE
};


/*****************************************************************************
 * ProcessHeader: process Flac header.
 *****************************************************************************/
static void ProcessHeader(decoder_t *p_dec)
{
    decoder_sys_t *p_sys = p_dec->p_sys;

    bs_t bs;
    int i_extra = p_dec->fmt_in.i_extra;
    char *p_extra = p_dec->fmt_in.p_extra;

    if (i_extra > 8 && !memcmp(p_extra, "fLaC", 4)) {
        i_extra -= 8;
        p_extra += 8;
    }

    if (p_dec->fmt_in.i_extra < 14)
        return;

    bs_init(&bs, p_extra, i_extra);

    p_sys->stream_info.min_blocksize = bs_read(&bs, 16);
    p_sys->stream_info.min_blocksize =
            __MIN( __MAX( p_sys->stream_info.min_blocksize, 16 ), 65535 );
    p_sys->stream_info.max_blocksize = bs_read(&bs, 16);
    p_sys->stream_info.max_blocksize =
                __MAX( __MIN( p_sys->stream_info.max_blocksize, 65535 ), 16 );

    p_sys->stream_info.min_framesize = bs_read(&bs, 24);
    p_sys->stream_info.min_framesize =
            __MAX( p_sys->stream_info.min_framesize, MIN_FLAC_FRAME_SIZE );
    p_sys->stream_info.max_framesize = bs_read(&bs, 24);

    p_sys->stream_info.sample_rate = bs_read(&bs, 20);
    p_sys->stream_info.channels = bs_read(&bs, 3) + 1;
    p_sys->stream_info.bits_per_sample = bs_read(&bs, 5) + 1;

    p_sys->b_stream_info = true;

    p_dec->fmt_out.i_extra = i_extra;
    free(p_dec->fmt_out.p_extra);
    p_dec->fmt_out.p_extra = malloc(i_extra);
    if (p_dec->fmt_out.p_extra)
        memcpy(p_dec->fmt_out.p_extra, p_extra, i_extra);
    else
        p_dec->fmt_out.i_extra = 0;
}

/* Will return INT64_MAX for an invalid utf-8 sequence */
static int64_t read_utf8(const uint8_t *p_buf, int *pi_read)
{
    /* Max coding bits is 56 - 8 */
    /* Value max precision is 36 bits */
    int64_t i_result = 0;
    unsigned i;

    if (!(p_buf[0] & 0x80)) { /* 0xxxxxxx */
        i_result = p_buf[0];
        i = 0;
    } else if (p_buf[0] & 0xC0 && !(p_buf[0] & 0x20)) { /* 110xxxxx */
        i_result = p_buf[0] & 0x1F;
        i = 1;
    } else if (p_buf[0] & 0xE0 && !(p_buf[0] & 0x10)) { /* 1110xxxx */
        i_result = p_buf[0] & 0x0F;
        i = 2;
    } else if (p_buf[0] & 0xF0 && !(p_buf[0] & 0x08)) { /* 11110xxx */
        i_result = p_buf[0] & 0x07;
        i = 3;
    } else if (p_buf[0] & 0xF8 && !(p_buf[0] & 0x04)) { /* 111110xx */
        i_result = p_buf[0] & 0x03;
        i = 4;
    } else if (p_buf[0] & 0xFC && !(p_buf[0] & 0x02)) { /* 1111110x */
        i_result = p_buf[0] & 0x01;
        i = 5;
    } else if (p_buf[0] & 0xFE && !(p_buf[0] & 0x01)) { /* 11111110 */
        i_result = 0;
        i = 6;
    } else {
        return INT64_MAX;
    }

    for (unsigned j = 1; j <= i; j++) {
        if (!(p_buf[j] & 0x80) || (p_buf[j] & 0x40)) { /* 10xxxxxx */
            return INT64_MAX;
        }
        i_result <<= 6;
        i_result |= (p_buf[j] & 0x3F);
    }

    *pi_read = i;
    return i_result;
}

/* CRC-8, poly = x^8 + x^2 + x^1 + x^0, init = 0 */
static const uint8_t flac_crc8_table[256] = {
        0x00, 0x07, 0x0E, 0x09, 0x1C, 0x1B, 0x12, 0x15,
        0x38, 0x3F, 0x36, 0x31, 0x24, 0x23, 0x2A, 0x2D,
        0x70, 0x77, 0x7E, 0x79, 0x6C, 0x6B, 0x62, 0x65,
        0x48, 0x4F, 0x46, 0x41, 0x54, 0x53, 0x5A, 0x5D,
        0xE0, 0xE7, 0xEE, 0xE9, 0xFC, 0xFB, 0xF2, 0xF5,
        0xD8, 0xDF, 0xD6, 0xD1, 0xC4, 0xC3, 0xCA, 0xCD,
        0x90, 0x97, 0x9E, 0x99, 0x8C, 0x8B, 0x82, 0x85,
        0xA8, 0xAF, 0xA6, 0xA1, 0xB4, 0xB3, 0xBA, 0xBD,
        0xC7, 0xC0, 0xC9, 0xCE, 0xDB, 0xDC, 0xD5, 0xD2,
        0xFF, 0xF8, 0xF1, 0xF6, 0xE3, 0xE4, 0xED, 0xEA,
        0xB7, 0xB0, 0xB9, 0xBE, 0xAB, 0xAC, 0xA5, 0xA2,
        0x8F, 0x88, 0x81, 0x86, 0x93, 0x94, 0x9D, 0x9A,
        0x27, 0x20, 0x29, 0x2E, 0x3B, 0x3C, 0x35, 0x32,
        0x1F, 0x18, 0x11, 0x16, 0x03, 0x04, 0x0D, 0x0A,
        0x57, 0x50, 0x59, 0x5E, 0x4B, 0x4C, 0x45, 0x42,
        0x6F, 0x68, 0x61, 0x66, 0x73, 0x74, 0x7D, 0x7A,
        0x89, 0x8E, 0x87, 0x80, 0x95, 0x92, 0x9B, 0x9C,
        0xB1, 0xB6, 0xBF, 0xB8, 0xAD, 0xAA, 0xA3, 0xA4,
        0xF9, 0xFE, 0xF7, 0xF0, 0xE5, 0xE2, 0xEB, 0xEC,
        0xC1, 0xC6, 0xCF, 0xC8, 0xDD, 0xDA, 0xD3, 0xD4,
        0x69, 0x6E, 0x67, 0x60, 0x75, 0x72, 0x7B, 0x7C,
        0x51, 0x56, 0x5F, 0x58, 0x4D, 0x4A, 0x43, 0x44,
        0x19, 0x1E, 0x17, 0x10, 0x05, 0x02, 0x0B, 0x0C,
        0x21, 0x26, 0x2F, 0x28, 0x3D, 0x3A, 0x33, 0x34,
        0x4E, 0x49, 0x40, 0x47, 0x52, 0x55, 0x5C, 0x5B,
        0x76, 0x71, 0x78, 0x7F, 0x6A, 0x6D, 0x64, 0x63,
        0x3E, 0x39, 0x30, 0x37, 0x22, 0x25, 0x2C, 0x2B,
        0x06, 0x01, 0x08, 0x0F, 0x1A, 0x1D, 0x14, 0x13,
        0xAE, 0xA9, 0xA0, 0xA7, 0xB2, 0xB5, 0xBC, 0xBB,
        0x96, 0x91, 0x98, 0x9F, 0x8A, 0x8D, 0x84, 0x83,
        0xDE, 0xD9, 0xD0, 0xD7, 0xC2, 0xC5, 0xCC, 0xCB,
        0xE6, 0xE1, 0xE8, 0xEF, 0xFA, 0xFD, 0xF4, 0xF3
};

static uint8_t flac_crc8(const uint8_t *data, unsigned len)
{
    uint8_t crc = 0;

    while (len--)
        crc = flac_crc8_table[crc ^ *data++];

    return crc;
}

/* CRC-16, poly = x^16 + x^15 + x^2 + x^0, init = 0 */
static const uint16_t flac_crc16_table[256] = {
    0x0000,  0x8005,  0x800f,  0x000a,  0x801b,  0x001e,  0x0014,  0x8011,
    0x8033,  0x0036,  0x003c,  0x8039,  0x0028,  0x802d,  0x8027,  0x0022,
    0x8063,  0x0066,  0x006c,  0x8069,  0x0078,  0x807d,  0x8077,  0x0072,
    0x0050,  0x8055,  0x805f,  0x005a,  0x804b,  0x004e,  0x0044,  0x8041,
    0x80c3,  0x00c6,  0x00cc,  0x80c9,  0x00d8,  0x80dd,  0x80d7,  0x00d2,
    0x00f0,  0x80f5,  0x80ff,  0x00fa,  0x80eb,  0x00ee,  0x00e4,  0x80e1,
    0x00a0,  0x80a5,  0x80af,  0x00aa,  0x80bb,  0x00be,  0x00b4,  0x80b1,
    0x8093,  0x0096,  0x009c,  0x8099,  0x0088,  0x808d,  0x8087,  0x0082,
    0x8183,  0x0186,  0x018c,  0x8189,  0x0198,  0x819d,  0x8197,  0x0192,
    0x01b0,  0x81b5,  0x81bf,  0x01ba,  0x81ab,  0x01ae,  0x01a4,  0x81a1,
    0x01e0,  0x81e5,  0x81ef,  0x01ea,  0x81fb,  0x01fe,  0x01f4,  0x81f1,
    0x81d3,  0x01d6,  0x01dc,  0x81d9,  0x01c8,  0x81cd,  0x81c7,  0x01c2,
    0x0140,  0x8145,  0x814f,  0x014a,  0x815b,  0x015e,  0x0154,  0x8151,
    0x8173,  0x0176,  0x017c,  0x8179,  0x0168,  0x816d,  0x8167,  0x0162,
    0x8123,  0x0126,  0x012c,  0x8129,  0x0138,  0x813d,  0x8137,  0x0132,
    0x0110,  0x8115,  0x811f,  0x011a,  0x810b,  0x010e,  0x0104,  0x8101,
    0x8303,  0x0306,  0x030c,  0x8309,  0x0318,  0x831d,  0x8317,  0x0312,
    0x0330,  0x8335,  0x833f,  0x033a,  0x832b,  0x032e,  0x0324,  0x8321,
    0x0360,  0x8365,  0x836f,  0x036a,  0x837b,  0x037e,  0x0374,  0x8371,
    0x8353,  0x0356,  0x035c,  0x8359,  0x0348,  0x834d,  0x8347,  0x0342,
    0x03c0,  0x83c5,  0x83cf,  0x03ca,  0x83db,  0x03de,  0x03d4,  0x83d1,
    0x83f3,  0x03f6,  0x03fc,  0x83f9,  0x03e8,  0x83ed,  0x83e7,  0x03e2,
    0x83a3,  0x03a6,  0x03ac,  0x83a9,  0x03b8,  0x83bd,  0x83b7,  0x03b2,
    0x0390,  0x8395,  0x839f,  0x039a,  0x838b,  0x038e,  0x0384,  0x8381,
    0x0280,  0x8285,  0x828f,  0x028a,  0x829b,  0x029e,  0x0294,  0x8291,
    0x82b3,  0x02b6,  0x02bc,  0x82b9,  0x02a8,  0x82ad,  0x82a7,  0x02a2,
    0x82e3,  0x02e6,  0x02ec,  0x82e9,  0x02f8,  0x82fd,  0x82f7,  0x02f2,
    0x02d0,  0x82d5,  0x82df,  0x02da,  0x82cb,  0x02ce,  0x02c4,  0x82c1,
    0x8243,  0x0246,  0x024c,  0x8249,  0x0258,  0x825d,  0x8257,  0x0252,
    0x0270,  0x8275,  0x827f,  0x027a,  0x826b,  0x026e,  0x0264,  0x8261,
    0x0220,  0x8225,  0x822f,  0x022a,  0x823b,  0x023e,  0x0234,  0x8231,
    0x8213,  0x0216,  0x021c,  0x8219,  0x0208,  0x820d,  0x8207,  0x0202
};

static uint16_t flac_crc16(uint16_t crc, uint8_t byte)
{
    return (crc << 8) ^ flac_crc16_table[(crc >> 8) ^ byte];
}

/* Gives the previous CRC value, before hashing last_byte through it */
static uint16_t flac_crc16_undo(uint16_t crc, const uint8_t last_byte)
{
    /*
     * Given a byte b, gives a position X in flac_crc16_table, such as:
     *      flac_crc16_rev_table[flac_crc16_table[X] & 0xff] == X
     * This works because flac_crc16_table[i] & 0xff yields 256 unique values.
     */
    static const uint8_t flac_crc16_rev_table[256] = {
        0x00, 0x7f, 0xff, 0x80, 0x7e, 0x01, 0x81, 0xfe,
        0xfc, 0x83, 0x03, 0x7c, 0x82, 0xfd, 0x7d, 0x02,
        0x78, 0x07, 0x87, 0xf8, 0x06, 0x79, 0xf9, 0x86,
        0x84, 0xfb, 0x7b, 0x04, 0xfa, 0x85, 0x05, 0x7a,
        0xf0, 0x8f, 0x0f, 0x70, 0x8e, 0xf1, 0x71, 0x0e,
        0x0c, 0x73, 0xf3, 0x8c, 0x72, 0x0d, 0x8d, 0xf2,
        0x88, 0xf7, 0x77, 0x08, 0xf6, 0x89, 0x09, 0x76,
        0x74, 0x0b, 0x8b, 0xf4, 0x0a, 0x75, 0xf5, 0x8a,
        0x60, 0x1f, 0x9f, 0xe0, 0x1e, 0x61, 0xe1, 0x9e,
        0x9c, 0xe3, 0x63, 0x1c, 0xe2, 0x9d, 0x1d, 0x62,
        0x18, 0x67, 0xe7, 0x98, 0x66, 0x19, 0x99, 0xe6,
        0xe4, 0x9b, 0x1b, 0x64, 0x9a, 0xe5, 0x65, 0x1a,
        0x90, 0xef, 0x6f, 0x10, 0xee, 0x91, 0x11, 0x6e,
        0x6c, 0x13, 0x93, 0xec, 0x12, 0x6d, 0xed, 0x92,
        0xe8, 0x97, 0x17, 0x68, 0x96, 0xe9, 0x69, 0x16,
        0x14, 0x6b, 0xeb, 0x94, 0x6a, 0x15, 0x95, 0xea,
        0xc0, 0xbf, 0x3f, 0x40, 0xbe, 0xc1, 0x41, 0x3e,
        0x3c, 0x43, 0xc3, 0xbc, 0x42, 0x3d, 0xbd, 0xc2,
        0xb8, 0xc7, 0x47, 0x38, 0xc6, 0xb9, 0x39, 0x46,
        0x44, 0x3b, 0xbb, 0xc4, 0x3a, 0x45, 0xc5, 0xba,
        0x30, 0x4f, 0xcf, 0xb0, 0x4e, 0x31, 0xb1, 0xce,
        0xcc, 0xb3, 0x33, 0x4c, 0xb2, 0xcd, 0x4d, 0x32,
        0x48, 0x37, 0xb7, 0xc8, 0x36, 0x49, 0xc9, 0xb6,
        0xb4, 0xcb, 0x4b, 0x34, 0xca, 0xb5, 0x35, 0x4a,
        0xa0, 0xdf, 0x5f, 0x20, 0xde, 0xa1, 0x21, 0x5e,
        0x5c, 0x23, 0xa3, 0xdc, 0x22, 0x5d, 0xdd, 0xa2,
        0xd8, 0xa7, 0x27, 0x58, 0xa6, 0xd9, 0x59, 0x26,
        0x24, 0x5b, 0xdb, 0xa4, 0x5a, 0x25, 0xa5, 0xda,
        0x50, 0x2f, 0xaf, 0xd0, 0x2e, 0x51, 0xd1, 0xae,
        0xac, 0xd3, 0x53, 0x2c, 0xd2, 0xad, 0x2d, 0x52,
        0x28, 0x57, 0xd7, 0xa8, 0x56, 0x29, 0xa9, 0xd6,
        0xd4, 0xab, 0x2b, 0x54, 0xaa, 0xd5, 0x55, 0x2a,
    };
    uint8_t idx = flac_crc16_rev_table[crc & 0xff];
    return ((idx ^ last_byte) << 8) | ((crc ^ flac_crc16_table[idx]) >> 8);
}

/*****************************************************************************
 * SyncInfo: parse FLAC sync info
 *****************************************************************************/
static int SyncInfo(decoder_t *p_dec, uint8_t *p_buf,
                     unsigned int * pi_channels,
                     unsigned int * pi_sample_rate,
                     unsigned int * pi_bits_per_sample,
                     mtime_t * pi_pts,
                     mtime_t * pi_duration )
{
    decoder_sys_t *p_sys = p_dec->p_sys;

    /* Check syncword */
    if (p_buf[0] != 0xFF || (p_buf[1] & 0xFE) != 0xF8)
        return 0;

    /* Check there is no emulated sync code in the rest of the header */
    if (p_buf[2] == 0xff || p_buf[3] == 0xFF)
        return 0;

    /* Find blocksize (framelength) */
    int blocksize_hint = 0;
    unsigned blocksize = p_buf[2] >> 4;
    if (blocksize >= 8) {
        blocksize = 256 << (blocksize - 8);
    } else if (blocksize == 0) { /* value 0 is reserved */
        if (p_sys->b_stream_info &&
            p_sys->stream_info.min_blocksize == p_sys->stream_info.max_blocksize)
            blocksize = p_sys->stream_info.min_blocksize;
        else
            return 0; /* We can't do anything with this */
    } else if (blocksize == 1) {
        blocksize = 192;
    } else if (blocksize == 6 || blocksize == 7) {
        blocksize_hint = blocksize;
        blocksize = 0;
    } else /* 2, 3, 4, 5 */ {
        blocksize = 576 << (blocksize - 2);
    }

    if (p_sys->b_stream_info && !blocksize_hint )
        if (blocksize < p_sys->stream_info.min_blocksize ||
            blocksize > p_sys->stream_info.max_blocksize)
            return 0;

    /* Find samplerate */
    int samplerate_hint = p_buf[2] & 0xf;;
    unsigned int samplerate;
    if (samplerate_hint == 0) {
        if (p_sys->b_stream_info)
            samplerate = p_sys->stream_info.sample_rate;
        else
            return 0; /* We can't do anything with this */
    } else if (samplerate_hint == 15) {
        return 0; /* invalid */
    } else if (samplerate_hint < 12) {
        static const int16_t flac_samplerate[12] = {
            0,    8820, 17640, 19200,
            800,  1600, 2205,  2400,
            3200, 4410, 4800,  9600, 
        };
        samplerate = flac_samplerate[samplerate_hint] * 10;
    } else {
        samplerate = 0; /* at end of header */
    }

    /* Find channels */
    unsigned channels = p_buf[3] >> 4;
    if (channels >= 8) {
        if (channels >= 11) /* reserved */
            return 0;
        channels = 2;
    } else
        channels++;


    /* Find bits per sample */
    static const int8_t flac_bits_per_sample[8] = {
        0, 8, 12, -1, 16, 20, 24, -1
    };
    int bits_per_sample = flac_bits_per_sample[(p_buf[3] & 0x0e) >> 1];
    if (bits_per_sample == 0) {
        if (p_sys->b_stream_info)
            bits_per_sample = p_sys->stream_info.bits_per_sample;
        else
            return 0;
    } else if (bits_per_sample < 0)
        return 0;


    /* reserved for future use */
    if (p_buf[3] & 0x01)
        return 0;

    /* End of fixed size header */
    int i_header = 4;

    /* Check Sample/Frame number */
    int i_read;
    int64_t i_fsnumber = read_utf8(&p_buf[i_header++], &i_read);
    if ( i_fsnumber == INT64_MAX )
        return 0;

    i_header += i_read;

    /* Read blocksize */
    if (blocksize_hint) {
        blocksize = p_buf[i_header++];
        if (blocksize_hint == 7) {
            blocksize <<= 8;
            blocksize |= p_buf[i_header++];
        }
        blocksize++;
    }

    /* Read sample rate */
    if (samplerate == 0) {
        samplerate = p_buf[i_header++];
        if (samplerate_hint != 12) { /* 16 bits */
            samplerate <<= 8;
            samplerate |= p_buf[i_header++];
        }

        if (samplerate_hint == 12)
            samplerate *= 1000;
        else if (samplerate_hint == 14)
            samplerate *= 10;
    }

    if ( !samplerate )
        return 0;

    /* Check the CRC-8 byte */
    if (flac_crc8(p_buf, i_header) != p_buf[i_header])
        return 0;

    /* Sanity check using stream info header when possible */
    if (p_sys->b_stream_info) {
        if (blocksize < p_sys->stream_info.min_blocksize ||
            blocksize > p_sys->stream_info.max_blocksize)
            return 0;
        if ((unsigned)bits_per_sample != p_sys->stream_info.bits_per_sample)
            return 0;
        if (samplerate != p_sys->stream_info.sample_rate)
            return 0;
    }

    if( pi_pts )
    {
        *pi_pts = VLC_TS_0;
        if ( (p_buf[1] & 0x01) == 0  ) /* Fixed blocksize stream / Frames */
            *pi_pts += CLOCK_FREQ * blocksize * i_fsnumber / samplerate;
        else /* Variable blocksize stream / Samples */
            *pi_pts += CLOCK_FREQ * i_fsnumber / samplerate;
    }

    if ( pi_duration )
        *pi_duration = CLOCK_FREQ * blocksize / samplerate;

    *pi_bits_per_sample = bits_per_sample;
    *pi_sample_rate = samplerate;
    *pi_channels = channels;

    return blocksize;
}

/* */
static block_t *Packetize(decoder_t *p_dec, block_t **pp_block)
{
    decoder_sys_t *p_sys = p_dec->p_sys;
    uint8_t p_header[MAX_FLAC_HEADER_SIZE];
    block_t *out, *in = NULL;

    if ( pp_block && *pp_block)
    {
        in = *pp_block;

        if (in->i_flags&(BLOCK_FLAG_DISCONTINUITY|BLOCK_FLAG_CORRUPTED)) {
            if (in->i_flags&BLOCK_FLAG_CORRUPTED) {
                p_sys->i_state = STATE_NOSYNC;
                block_BytestreamEmpty(&p_sys->bytestream);
            }
            block_Release(*pp_block);
            return NULL;
        }
    }

    if (!p_sys->b_stream_info)
        ProcessHeader(p_dec);

    if (p_sys->stream_info.channels > 8) {
        msg_Err(p_dec, "This stream uses too many audio channels (%d > 8)",
            p_sys->stream_info.channels);
        return NULL;
    }

    if ( p_sys->i_pts <= VLC_TS_INVALID )
    {
        if ( in && in->i_pts == p_sys->i_pts )
        {
            /* We've just started the stream, wait for the first PTS. */
            block_Release(in);
            return NULL;
        }
        p_sys->i_rate = p_dec->fmt_out.audio.i_rate;
    }

    if ( in )
        block_BytestreamPush(&p_sys->bytestream, in);

    while (1) switch (p_sys->i_state) {
    case STATE_NOSYNC:
        while (!block_PeekBytes(&p_sys->bytestream, p_header, 2)) {
            if (p_header[0] == 0xFF && (p_header[1] & 0xFE) == 0xF8) {
                p_sys->i_state = STATE_SYNC;
                break;
            }
            block_SkipByte(&p_sys->bytestream);
        }
        if (p_sys->i_state != STATE_SYNC) {
            block_BytestreamFlush(&p_sys->bytestream);
            return NULL; /* Need more data */
        }

    case STATE_SYNC:
        /* Sync state is unverified until we have read frame header and checked CRC
           Once validated, we'll send data from NEXT_SYNC state where we'll
           compute frame size */
        p_sys->i_state = STATE_HEADER;

    case STATE_HEADER:
        /* Get FLAC frame header (MAX_FLAC_HEADER_SIZE bytes) */
        if (block_PeekBytes(&p_sys->bytestream, p_header, MAX_FLAC_HEADER_SIZE))
            return NULL; /* Need more data */

        /* Check if frame is valid and get frame info */
        p_sys->i_frame_length = SyncInfo(p_dec, p_header,
                                          &p_sys->i_channels,
                                          &p_sys->i_rate,
                                          &p_sys->i_bits_per_sample,
                                          &p_sys->i_pts,
                                          &p_sys->i_duration );
        if (!p_sys->i_frame_length) {
            msg_Dbg(p_dec, "emulated sync word");
            block_SkipByte(&p_sys->bytestream);
            p_sys->i_state = STATE_NOSYNC;
            break;
        }
        if (p_sys->i_rate != p_dec->fmt_out.audio.i_rate) {
            p_dec->fmt_out.audio.i_rate = p_sys->i_rate;
        }
        p_sys->i_state = STATE_NEXT_SYNC;
        p_sys->i_frame_size = ( p_sys->b_stream_info ) ? p_sys->stream_info.min_framesize :
                                                         MIN_FLAC_FRAME_SIZE;

        /* We have to read until next frame sync code to compute current frame size
         * from that boundary.
         * The confusing part below is that sync code needs to be verified in case
         * it would appear in data, so we also need to check next frame header CRC
         */
    case STATE_NEXT_SYNC:
    {
        /* Calculate the initial CRC for the minimal frame size,
         * We'll update it as we look for the next start code. */
        uint8_t *buf = malloc(p_sys->i_frame_size);
        if (!buf)
            return NULL;

        if (block_PeekOffsetBytes(&p_sys->bytestream, 0, buf, p_sys->i_frame_size)) {
            free(buf);
            return NULL;
        }

        uint16_t crc = 0;
        for (unsigned i = 0; i < p_sys->i_frame_size; i++)
            crc = flac_crc16(crc, buf[i]);
        free(buf);
        p_sys->crc = crc;

        /* Check if next expected frame contains the sync word */
        while (!block_PeekOffsetBytes(&p_sys->bytestream, p_sys->i_frame_size,
                    p_header, MAX_FLAC_HEADER_SIZE)) {
            if (p_header[0] == 0xFF && (p_header[1] & 0xFE) == 0xF8) {
                /* Check if frame is valid and get frame info */
                int i_frame_length =
                    SyncInfo(p_dec, p_header,
                              &p_sys->i_channels,
                              &p_sys->i_rate,
                              &p_sys->i_bits_per_sample,
                              NULL, NULL );

                if (i_frame_length) {
                    uint8_t crc_bytes[2];
                    block_PeekOffsetBytes(&p_sys->bytestream,
                        p_sys->i_frame_size - 2, crc_bytes, 2);
                    /* Get the frame CRC */
                    uint16_t stream_crc = (crc_bytes[0] << 8) | crc_bytes[1];
                    /* Calculate the frame CRC: remove the last 2 bytes */
                    uint16_t crc = flac_crc16_undo(p_sys->crc, crc_bytes[1]);
                             crc = flac_crc16_undo(crc,        crc_bytes[0]);
                    if (stream_crc != crc) {
                        msg_Warn(p_dec, "Bad CRC for frame size %zu: 0x%x != 0x%x",
                            p_sys->i_frame_size, crc, stream_crc);
                        block_SkipByte(&p_sys->bytestream);
                        p_sys->i_state = STATE_NOSYNC;
                    } else {
                        p_sys->i_state = STATE_SEND_DATA;
                        p_sys->crc = 0;
                        break;
                    }
                }
            }
            p_sys->crc = flac_crc16(p_sys->crc, p_header[0]); /* update CRC */
            p_sys->i_frame_size++;
        }

        if (p_sys->i_state != STATE_SEND_DATA) {
            if (p_sys->b_stream_info && p_sys->stream_info.max_framesize > 0 &&
                p_sys->i_frame_size > p_sys->stream_info.max_framesize) {
                block_SkipByte(&p_sys->bytestream);
                msg_Warn(p_dec, "Frame is too big (%zu > %d), couldn't find start code",
                        p_sys->i_frame_size, p_sys->stream_info.max_framesize);
                p_sys->i_state = STATE_NOSYNC;
                return NULL;
            }

            if ( !in )
            {
                /* There's no following frame, so we need to read current
                 * data until the frame footer matches (crc16) == stream crc.
                 * In the worst case, if crc might be a false positive and data
                 * will be truncated. */
                uint8_t crc_bytes[2];
                if ( !block_PeekOffsetBytes(&p_sys->bytestream,
                                    p_sys->i_frame_size - 2, crc_bytes, 2) )
                {
                    while ( true )
                    {
                        /* Read the frame CRC */
                        uint16_t stream_crc = (crc_bytes[0] << 8) | crc_bytes[1];
                        /* Calculate the frame CRC: remove the last 2 bytes */
                        uint16_t crc = flac_crc16_undo(p_sys->crc, crc_bytes[1]);
                                 crc = flac_crc16_undo(crc,        crc_bytes[0]);
                        if (stream_crc == crc)
                        {
                            p_sys->i_state = STATE_SEND_DATA;
                            break;
                        }
                        p_sys->i_frame_size++;
                        if ( block_PeekOffsetBytes(&p_sys->bytestream,
                                                   p_sys->i_frame_size - 2, crc_bytes, 2) )
                            break;
                        /* Update current crc */
                        p_sys->crc = flac_crc16(p_sys->crc, crc_bytes[1]);
                    }
                }

                if ( p_sys->i_state != STATE_SEND_DATA )
                    return NULL;
            }
            else
            {
                /* Need more data */
                return NULL;
            }
        }
    }
    case STATE_SEND_DATA:
        out = block_Alloc(p_sys->i_frame_size);

        /* Copy the whole frame into the buffer. When we reach this point
         * we already know we have enough data available. */
        block_GetBytes(&p_sys->bytestream, out->p_buffer,
                        p_sys->i_frame_size);

        p_dec->fmt_out.audio.i_channels = p_sys->i_channels;
        p_dec->fmt_out.audio.i_physical_channels =
            p_dec->fmt_out.audio.i_original_channels =
                pi_channels_maps[p_sys->stream_info.channels];

        /* So p_block doesn't get re-added several times */
        if ( in )
            *pp_block = block_BytestreamPop(&p_sys->bytestream);
        else
            block_BytestreamFlush(&p_sys->bytestream);

        p_sys->i_state = STATE_NOSYNC;

        out->i_dts = out->i_pts = p_sys->i_pts;
        out->i_length = p_sys->i_duration;

        return out;
    }

    return NULL;
}

static int Open(vlc_object_t *p_this)
{
    decoder_t *p_dec = (decoder_t*)p_this;
    decoder_sys_t *p_sys;

    if (p_dec->fmt_in.i_codec != VLC_CODEC_FLAC)
        return VLC_EGENERIC;

    /* */
    p_dec->p_sys = p_sys = malloc(sizeof(*p_sys));
    if (!p_sys)
        return VLC_ENOMEM;

    p_sys->i_state       = STATE_NOSYNC;
    p_sys->b_stream_info = false;
    p_sys->i_pts         = VLC_TS_INVALID;
    block_BytestreamInit(&p_sys->bytestream);

    /* */
    es_format_Copy(&p_dec->fmt_out, &p_dec->fmt_in);
    p_dec->fmt_out.i_cat   = AUDIO_ES;
    p_dec->fmt_out.i_codec = VLC_CODEC_FLAC;

    /* */
    p_dec->pf_decode_audio = NULL;
    p_dec->pf_packetize    = Packetize;

    return VLC_SUCCESS;
}

static void Close(vlc_object_t *p_this)
{
    decoder_t *p_dec = (decoder_t *)p_this;
    decoder_sys_t *p_sys = p_dec->p_sys;

    es_format_Clean(&p_dec->fmt_out);
    block_BytestreamRelease(&p_sys->bytestream);
    free(p_sys);
}
