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/*

 * Matroska muxer

 * Copyright (c) 2007 David Conrad

 *

 * This file is part of FFmpeg.

 *

 * FFmpeg is free software; you can redistribute it and/or

 * modify it under the terms of the GNU Lesser General Public

 * License as published by the Free Software Foundation; either

 * version 2.1 of the License, or (at your option) any later version.

 *

 * FFmpeg is distributed in the hope that it will be useful,

 * but WITHOUT ANY WARRANTY; without even the implied warranty of

 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU

 * Lesser General Public License for more details.

 *

 * You should have received a copy of the GNU Lesser General Public

 * License along with FFmpeg; if not, write to the Free Software

 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA

 */

#include "avc.h"

#include "avformat.h"

#include "avio_internal.h"

#include "avlanguage.h"

#include "flacenc.h"

#include "internal.h"

#include "isom.h"

#include "matroska.h"

#include "riff.h"

#include "subtitles.h"

#include "wv.h"

#include "libavutil/avstring.h"

#include "libavutil/dict.h"

#include "libavutil/intfloat.h"

#include "libavutil/intreadwrite.h"

#include "libavutil/lfg.h"

#include "libavutil/mathematics.h"

#include "libavutil/opt.h"

#include "libavutil/random_seed.h"

#include "libavutil/samplefmt.h"

#include "libavutil/sha.h"

#include "libavcodec/xiph.h"

#include "libavcodec/mpeg4audio.h"

#include "libavcodec/internal.h"

typedef struct ebml_master {

    int64_t         pos;                ///< absolute offset in the file where the master's elements start

    int             sizebytes;          ///< how many bytes were reserved for the size

} ebml_master;

typedef struct mkv_seekhead_entry {

    unsigned int    elementid;

    uint64_t        segmentpos;

} mkv_seekhead_entry;

typedef struct mkv_seekhead {

    int64_t                 filepos;

    int64_t                 segment_offset;     ///< the file offset to the beginning of the segment

    int                     reserved_size;      ///< -1 if appending to file

    int                     max_entries;

    mkv_seekhead_entry      *entries;

    int                     num_entries;

} mkv_seekhead;

typedef struct {

    uint64_t        pts;

    int             tracknum;

    int64_t         cluster_pos;        ///< file offset of the cluster containing the block

    int64_t         relative_pos;       ///< relative offset from the position of the cluster containing the block

    int64_t         duration;           ///< duration of the block according to time base

} mkv_cuepoint;

typedef struct {

    int64_t         segment_offset;

    mkv_cuepoint    *entries;

    int             num_entries;

} mkv_cues;

typedef struct {

    int             write_dts;

    int             has_cue;

} mkv_track;

#define MODE_MATROSKAv2 0x01

#define MODE_WEBM       0x02

typedef struct MatroskaMuxContext {

    const AVClass  *class;

    int             mode;

    AVIOContext   *dyn_bc;

    ebml_master     segment;

    int64_t         segment_offset;

    ebml_master     cluster;

    int64_t         cluster_pos;        ///< file offset of the current cluster

    int64_t         cluster_pts;

    int64_t         duration_offset;

    int64_t         duration;

    mkv_seekhead    *main_seekhead;

    mkv_cues        *cues;

    mkv_track       *tracks;

    AVPacket        cur_audio_pkt;

    int have_attachments;

    int reserve_cues_space;

    int cluster_size_limit;

    int64_t cues_pos;

    int64_t cluster_time_limit;

    uint32_t chapter_id_offset;

    int wrote_chapters;

} MatroskaMuxContext;

/** 2 bytes * 3 for EBML IDs, 3 1-byte EBML lengths, 8 bytes for 64 bit

 * offset, 4 bytes for target EBML ID */

#define MAX_SEEKENTRY_SIZE 21

/** per-cuepoint-track - 5 1-byte EBML IDs, 5 1-byte EBML sizes, 4

 * 8-byte uint max */

#define MAX_CUETRACKPOS_SIZE 42

/** per-cuepoint - 2 1-byte EBML IDs, 2 1-byte EBML sizes, 8-byte uint max */

#define MAX_CUEPOINT_SIZE(num_tracks) 12 + MAX_CUETRACKPOS_SIZE*num_tracks

/** Seek preroll value for opus */

#define OPUS_SEEK_PREROLL 80000000

static int ebml_id_size(unsigned int id)

{

    return (av_log2(id+1)-1)/7+1;

}

static void put_ebml_id(AVIOContext *pb, unsigned int id)

{

    int i = ebml_id_size(id);

    while (i--)

        avio_w8(pb, (uint8_t)(id >> (i*8)));

}

/**

 * Write an EBML size meaning "unknown size".

 *

 * @param bytes The number of bytes the size should occupy (maximum: 8).

 */

static void put_ebml_size_unknown(AVIOContext *pb, int bytes)

{

    av_assert0(bytes <= 8);

    avio_w8(pb, 0x1ff >> bytes);

    ffio_fill(pb, 0xff, bytes - 1);

}

/**

 * Calculate how many bytes are needed to represent a given number in EBML.

 */

static int ebml_num_size(uint64_t num)

{

    int bytes = 1;

    while ((num+1) >> bytes*7) bytes++;

    return bytes;

}

/**

 * Write a number in EBML variable length format.

 *

 * @param bytes The number of bytes that need to be used to write the number.

 *              If zero, any number of bytes can be used.

 */

static void put_ebml_num(AVIOContext *pb, uint64_t num, int bytes)

{

    int i, needed_bytes = ebml_num_size(num);

    // sizes larger than this are currently undefined in EBML

    av_assert0(num < (1ULL<<56)-1);

    if (bytes == 0)

        // don't care how many bytes are used, so use the min

        bytes = needed_bytes;

    // the bytes needed to write the given size would exceed the bytes

    // that we need to use, so write unknown size. This shouldn't happen.

    av_assert0(bytes >= needed_bytes);

    num |= 1ULL << bytes*7;

    for (i = bytes - 1; i >= 0; i--)

        avio_w8(pb, (uint8_t)(num >> i*8));

}

static void put_ebml_uint(AVIOContext *pb, unsigned int elementid, uint64_t val)

{

    int i, bytes = 1;

    uint64_t tmp = val;

    while (tmp>>=8) bytes++;

    put_ebml_id(pb, elementid);

    put_ebml_num(pb, bytes, 0);

    for (i = bytes - 1; i >= 0; i--)

        avio_w8(pb, (uint8_t)(val >> i*8));

}

static void put_ebml_float(AVIOContext *pb, unsigned int elementid, double val)

{

    put_ebml_id(pb, elementid);

    put_ebml_num(pb, 8, 0);

    avio_wb64(pb, av_double2int(val));

}

static void put_ebml_binary(AVIOContext *pb, unsigned int elementid,

                            const void *buf, int size)

{

    put_ebml_id(pb, elementid);

    put_ebml_num(pb, size, 0);

    avio_write(pb, buf, size);

}

static void put_ebml_string(AVIOContext *pb, unsigned int elementid, const char *str)

{

    put_ebml_binary(pb, elementid, str, strlen(str));

}

/**

 * Write a void element of a given size. Useful for reserving space in

 * the file to be written to later.

 *

 * @param size The number of bytes to reserve, which must be at least 2.

 */

static void put_ebml_void(AVIOContext *pb, uint64_t size)

{

    int64_t currentpos = avio_tell(pb);

    av_assert0(size >= 2);

    put_ebml_id(pb, EBML_ID_VOID);

    // we need to subtract the length needed to store the size from the

    // size we need to reserve so 2 cases, we use 8 bytes to store the

    // size if possible, 1 byte otherwise

    if (size < 10)

        put_ebml_num(pb, size-1, 0);

    else

        put_ebml_num(pb, size-9, 8);

    ffio_fill(pb, 0, currentpos + size - avio_tell(pb));

}

static ebml_master start_ebml_master(AVIOContext *pb, unsigned int elementid, uint64_t expectedsize)

{

    int bytes = expectedsize ? ebml_num_size(expectedsize) : 8;

    put_ebml_id(pb, elementid);

    put_ebml_size_unknown(pb, bytes);

    return (ebml_master){ avio_tell(pb), bytes };

}

static void end_ebml_master(AVIOContext *pb, ebml_master master)

{

    int64_t pos = avio_tell(pb);

    if (avio_seek(pb, master.pos - master.sizebytes, SEEK_SET) < 0)

        return;

    put_ebml_num(pb, pos - master.pos, master.sizebytes);

    avio_seek(pb, pos, SEEK_SET);

}

static void put_xiph_size(AVIOContext *pb, int size)

{

    ffio_fill(pb, 255, size / 255);

    avio_w8(pb, size % 255);

}

/**

 * Initialize a mkv_seekhead element to be ready to index level 1 Matroska

 * elements. If a maximum number of elements is specified, enough space

 * will be reserved at the current file location to write a seek head of

 * that size.

 *

 * @param segment_offset The absolute offset to the position in the file

 *                       where the segment begins.

 * @param numelements The maximum number of elements that will be indexed

 *                    by this seek head, 0 if unlimited.

 */

static mkv_seekhead * mkv_start_seekhead(AVIOContext *pb, int64_t segment_offset, int numelements)

{

    mkv_seekhead *new_seekhead = av_mallocz(sizeof(mkv_seekhead));

    if (new_seekhead == NULL)

        return NULL;

    new_seekhead->segment_offset = segment_offset;

    if (numelements > 0) {

        new_seekhead->filepos = avio_tell(pb);

        // 21 bytes max for a seek entry, 10 bytes max for the SeekHead ID

        // and size, and 3 bytes to guarantee that an EBML void element

        // will fit afterwards

        new_seekhead->reserved_size = numelements * MAX_SEEKENTRY_SIZE + 13;

        new_seekhead->max_entries = numelements;

        put_ebml_void(pb, new_seekhead->reserved_size);

    }

    return new_seekhead;

}

static int mkv_add_seekhead_entry(mkv_seekhead *seekhead, unsigned int elementid, uint64_t filepos)

{

    mkv_seekhead_entry *entries = seekhead->entries;

    // don't store more elements than we reserved space for

    if (seekhead->max_entries > 0 && seekhead->max_entries <= seekhead->num_entries)

        return -1;

    entries = av_realloc_array(entries, seekhead->num_entries + 1, sizeof(mkv_seekhead_entry));

    if (entries == NULL)

        return AVERROR(ENOMEM);

    seekhead->entries = entries;

    seekhead->entries[seekhead->num_entries].elementid    = elementid;

    seekhead->entries[seekhead->num_entries++].segmentpos = filepos - seekhead->segment_offset;

    return 0;

}

/**

 * Write the seek head to the file and free it. If a maximum number of

 * elements was specified to mkv_start_seekhead(), the seek head will

 * be written at the location reserved for it. Otherwise, it is written

 * at the current location in the file.

 *

 * @return The file offset where the seekhead was written,

 * -1 if an error occurred.

 */

static int64_t mkv_write_seekhead(AVIOContext *pb, mkv_seekhead *seekhead)

{

    ebml_master metaseek, seekentry;

    int64_t currentpos;

    int i;

    currentpos = avio_tell(pb);

    if (seekhead->reserved_size > 0) {

        if (avio_seek(pb, seekhead->filepos, SEEK_SET) < 0) {

            currentpos = -1;

            goto fail;

        }

    }

    metaseek = start_ebml_master(pb, MATROSKA_ID_SEEKHEAD, seekhead->reserved_size);

    for (i = 0; i < seekhead->num_entries; i++) {

        mkv_seekhead_entry *entry = &seekhead->entries[i];

        seekentry = start_ebml_master(pb, MATROSKA_ID_SEEKENTRY, MAX_SEEKENTRY_SIZE);

        put_ebml_id(pb, MATROSKA_ID_SEEKID);

        put_ebml_num(pb, ebml_id_size(entry->elementid), 0);

        put_ebml_id(pb, entry->elementid);

        put_ebml_uint(pb, MATROSKA_ID_SEEKPOSITION, entry->segmentpos);

        end_ebml_master(pb, seekentry);

    }

    end_ebml_master(pb, metaseek);

    if (seekhead->reserved_size > 0) {

        uint64_t remaining = seekhead->filepos + seekhead->reserved_size - avio_tell(pb);

        put_ebml_void(pb, remaining);

        avio_seek(pb, currentpos, SEEK_SET);

        currentpos = seekhead->filepos;

    }

fail:

    av_freep(&seekhead->entries);

    av_free(seekhead);

    return currentpos;

}

static mkv_cues * mkv_start_cues(int64_t segment_offset)

{

    mkv_cues *cues = av_mallocz(sizeof(mkv_cues));

    if (cues == NULL)

        return NULL;

    cues->segment_offset = segment_offset;

    return cues;

}

static int mkv_add_cuepoint(mkv_cues *cues, int stream, int64_t ts, int64_t cluster_pos, int64_t relative_pos,

                            int64_t duration)

{

    mkv_cuepoint *entries = cues->entries;

    if (ts < 0)

        return 0;

    entries = av_realloc_array(entries, cues->num_entries + 1, sizeof(mkv_cuepoint));

    if (entries == NULL)

        return AVERROR(ENOMEM);

    cues->entries = entries;

    cues->entries[cues->num_entries].pts           = ts;

    cues->entries[cues->num_entries].tracknum      = stream + 1;

    cues->entries[cues->num_entries].cluster_pos   = cluster_pos - cues->segment_offset;

    cues->entries[cues->num_entries].relative_pos  = relative_pos;

    cues->entries[cues->num_entries++].duration    = duration;

    return 0;

}

static int64_t mkv_write_cues(AVIOContext *pb, mkv_cues *cues, mkv_track *tracks, int num_tracks)

{

    ebml_master cues_element;

    int64_t currentpos;

    int i, j;

    currentpos = avio_tell(pb);

    cues_element = start_ebml_master(pb, MATROSKA_ID_CUES, 0);

    for (i = 0; i < cues->num_entries; i++) {

        ebml_master cuepoint, track_positions;

        mkv_cuepoint *entry = &cues->entries[i];

        uint64_t pts = entry->pts;

        cuepoint = start_ebml_master(pb, MATROSKA_ID_POINTENTRY, MAX_CUEPOINT_SIZE(num_tracks));

        put_ebml_uint(pb, MATROSKA_ID_CUETIME, pts);

        // put all the entries from different tracks that have the exact same

        // timestamp into the same CuePoint

        for (j = 0; j < num_tracks; j++)

            tracks[j].has_cue = 0;

        for (j = 0; j < cues->num_entries - i && entry[j].pts == pts; j++) {

            int tracknum = entry[j].tracknum - 1;

            av_assert0(tracknum>=0 && tracknum

            if (tracks[tracknum].has_cue)

                continue;

            tracks[tracknum].has_cue = 1;

            track_positions = start_ebml_master(pb, MATROSKA_ID_CUETRACKPOSITION, MAX_CUETRACKPOS_SIZE);

            put_ebml_uint(pb, MATROSKA_ID_CUETRACK           , entry[j].tracknum   );

            put_ebml_uint(pb, MATROSKA_ID_CUECLUSTERPOSITION , entry[j].cluster_pos);

            put_ebml_uint(pb, MATROSKA_ID_CUERELATIVEPOSITION, entry[j].relative_pos);

            if (entry[j].duration != -1)

                put_ebml_uint(pb, MATROSKA_ID_CUEDURATION    , entry[j].duration);

            end_ebml_master(pb, track_positions);

        }

        i += j - 1;

        end_ebml_master(pb, cuepoint);

    }

    end_ebml_master(pb, cues_element);

    return currentpos;

}

static int put_xiph_codecpriv(AVFormatContext *s, AVIOContext *pb, AVCodecContext *codec)

{

    uint8_t *header_start[3];

    int header_len[3];

    int first_header_size;

    int j;

    if (codec->codec_id == AV_CODEC_ID_VORBIS)

        first_header_size = 30;

    else

        first_header_size = 42;

    if (avpriv_split_xiph_headers(codec->extradata, codec->extradata_size,

                              first_header_size, header_start, header_len) < 0) {

        av_log(s, AV_LOG_ERROR, "Extradata corrupt.\n");

        return -1;

    }

    avio_w8(pb, 2);                    // number packets - 1

    for (j = 0; j < 2; j++) {

        put_xiph_size(pb, header_len[j]);

    }

    for (j = 0; j < 3; j++)

        avio_write(pb, header_start[j], header_len[j]);

    return 0;

}

static int put_wv_codecpriv(AVIOContext *pb, AVCodecContext *codec)

{

    if (codec->extradata && codec->extradata_size == 2)

        avio_write(pb, codec->extradata, 2);

    else

        avio_wl16(pb, 0x403); // fallback to the version mentioned in matroska specs

    return 0;

}

static void get_aac_sample_rates(AVFormatContext *s, AVCodecContext *codec, int *sample_rate, int *output_sample_rate)

{

    MPEG4AudioConfig mp4ac;

    if (avpriv_mpeg4audio_get_config(&mp4ac, codec->extradata,

                                     codec->extradata_size * 8, 1) < 0) {

        av_log(s, AV_LOG_WARNING, "Error parsing AAC extradata, unable to determine samplerate.\n");

        return;

    }

    *sample_rate        = mp4ac.sample_rate;

    *output_sample_rate = mp4ac.ext_sample_rate;

}

static int mkv_write_codecprivate(AVFormatContext *s, AVIOContext *pb, AVCodecContext *codec, int native_id, int qt_id)

{

    AVIOContext *dyn_cp;

    uint8_t *codecpriv;

    int ret, codecpriv_size;

    ret = avio_open_dyn_buf(&dyn_cp);

    if(ret < 0)

        return ret;

    if (native_id) {

        if (codec->codec_id == AV_CODEC_ID_VORBIS || codec->codec_id == AV_CODEC_ID_THEORA)

            ret = put_xiph_codecpriv(s, dyn_cp, codec);

        else if (codec->codec_id == AV_CODEC_ID_FLAC)

            ret = ff_flac_write_header(dyn_cp, codec, 1);

        else if (codec->codec_id == AV_CODEC_ID_WAVPACK)

            ret = put_wv_codecpriv(dyn_cp, codec);

        else if (codec->codec_id == AV_CODEC_ID_H264)

            ret = ff_isom_write_avcc(dyn_cp, codec->extradata, codec->extradata_size);

        else if (codec->codec_id == AV_CODEC_ID_ALAC) {

            if (codec->extradata_size < 36) {

                av_log(s, AV_LOG_ERROR,

                       "Invalid extradata found, ALAC expects a 36-byte "

                       "QuickTime atom.");

                ret = AVERROR_INVALIDDATA;

            } else

                avio_write(dyn_cp, codec->extradata + 12,

                                   codec->extradata_size - 12);

        }

        else if (codec->extradata_size && codec->codec_id != AV_CODEC_ID_TTA)

            avio_write(dyn_cp, codec->extradata, codec->extradata_size);

    } else if (codec->codec_type == AVMEDIA_TYPE_VIDEO) {

        if (qt_id) {

            if (!codec->codec_tag)

                codec->codec_tag = ff_codec_get_tag(ff_codec_movvideo_tags, codec->codec_id);

            if (codec->extradata_size)

                avio_write(dyn_cp, codec->extradata, codec->extradata_size);

        } else {

            if (!codec->codec_tag)

                codec->codec_tag = ff_codec_get_tag(ff_codec_bmp_tags, codec->codec_id);

            if (!codec->codec_tag) {

                av_log(s, AV_LOG_ERROR, "No bmp codec tag found for codec %s\n",

                       avcodec_get_name(codec->codec_id));

                ret = AVERROR(EINVAL);

            }

            ff_put_bmp_header(dyn_cp, codec, ff_codec_bmp_tags, 0);

        }

    } else if (codec->codec_type == AVMEDIA_TYPE_AUDIO) {

        unsigned int tag;

        tag = ff_codec_get_tag(ff_codec_wav_tags, codec->codec_id);

        if (!tag) {

            av_log(s, AV_LOG_ERROR, "No wav codec tag found for codec %s\n",

                   avcodec_get_name(codec->codec_id));

            ret = AVERROR(EINVAL);

        }

        if (!codec->codec_tag)

            codec->codec_tag = tag;

        ff_put_wav_header(dyn_cp, codec);

    }

    codecpriv_size = avio_close_dyn_buf(dyn_cp, &codecpriv);

    if (codecpriv_size)

        put_ebml_binary(pb, MATROSKA_ID_CODECPRIVATE, codecpriv, codecpriv_size);

    av_free(codecpriv);

    return ret;

}

static int mkv_write_tracks(AVFormatContext *s)

{

    MatroskaMuxContext *mkv = s->priv_data;

    AVIOContext *pb = s->pb;

    ebml_master tracks;

    int i, j, ret, default_stream_exists = 0;

    ret = mkv_add_seekhead_entry(mkv->main_seekhead, MATROSKA_ID_TRACKS, avio_tell(pb));

    if (ret < 0) return ret;

    tracks = start_ebml_master(pb, MATROSKA_ID_TRACKS, 0);

    for (i = 0; i < s->nb_streams; i++) {

        AVStream *st = s->streams[i];

        default_stream_exists |= st->disposition & AV_DISPOSITION_DEFAULT;

    }

    for (i = 0; i < s->nb_streams; i++) {

        AVStream *st = s->streams[i];

        AVCodecContext *codec = st->codec;

        ebml_master subinfo, track;

        int native_id = 0;

        int qt_id = 0;

        int bit_depth = av_get_bits_per_sample(codec->codec_id);

        int sample_rate = codec->sample_rate;

        int output_sample_rate = 0;

        AVDictionaryEntry *tag;

        if (codec->codec_type == AVMEDIA_TYPE_ATTACHMENT) {

            mkv->have_attachments = 1;

            continue;

        }

        if (!bit_depth)

            bit_depth = av_get_bytes_per_sample(codec->sample_fmt) << 3;

        if (!bit_depth)

            bit_depth = codec->bits_per_coded_sample;

        if (codec->codec_id == AV_CODEC_ID_AAC)

            get_aac_sample_rates(s, codec, &sample_rate, &output_sample_rate);

        track = start_ebml_master(pb, MATROSKA_ID_TRACKENTRY, 0);

        put_ebml_uint (pb, MATROSKA_ID_TRACKNUMBER     , i + 1);

        put_ebml_uint (pb, MATROSKA_ID_TRACKUID        , i + 1);

        put_ebml_uint (pb, MATROSKA_ID_TRACKFLAGLACING , 0);    // no lacing (yet)

        if ((tag = av_dict_get(st->metadata, "title", NULL, 0)))

            put_ebml_string(pb, MATROSKA_ID_TRACKNAME, tag->value);

        tag = av_dict_get(st->metadata, "language", NULL, 0);

        if (mkv->mode != MODE_WEBM || codec->codec_id != AV_CODEC_ID_WEBVTT) {

            put_ebml_string(pb, MATROSKA_ID_TRACKLANGUAGE, tag ? tag->value:"und");

        } else if (tag && tag->value) {

            put_ebml_string(pb, MATROSKA_ID_TRACKLANGUAGE, tag->value);

        }

        // The default value for TRACKFLAGDEFAULT is 1, so add element

        // if we need to clear it.

        if (default_stream_exists && !(st->disposition & AV_DISPOSITION_DEFAULT))

            put_ebml_uint(pb, MATROSKA_ID_TRACKFLAGDEFAULT, !!(st->disposition & AV_DISPOSITION_DEFAULT));

        if (st->disposition & AV_DISPOSITION_FORCED)

            put_ebml_uint(pb, MATROSKA_ID_TRACKFLAGFORCED, 1);

        if (mkv->mode == MODE_WEBM && codec->codec_id == AV_CODEC_ID_WEBVTT) {

            const char *codec_id;

            if (st->disposition & AV_DISPOSITION_CAPTIONS) {

                codec_id = "D_WEBVTT/CAPTIONS";

                native_id = MATROSKA_TRACK_TYPE_SUBTITLE;

            } else if (st->disposition & AV_DISPOSITION_DESCRIPTIONS) {

                codec_id = "D_WEBVTT/DESCRIPTIONS";

                native_id = MATROSKA_TRACK_TYPE_METADATA;

            } else if (st->disposition & AV_DISPOSITION_METADATA) {

                codec_id = "D_WEBVTT/METADATA";

                native_id = MATROSKA_TRACK_TYPE_METADATA;

            } else {

                codec_id = "D_WEBVTT/SUBTITLES";

                native_id = MATROSKA_TRACK_TYPE_SUBTITLE;

            }

            put_ebml_string(pb, MATROSKA_ID_CODECID, codec_id);

        } else {

            // look for a codec ID string specific to mkv to use,

            // if none are found, use AVI codes

            for (j = 0; ff_mkv_codec_tags[j].id != AV_CODEC_ID_NONE; j++) {

                if (ff_mkv_codec_tags[j].id == codec->codec_id) {

                    put_ebml_string(pb, MATROSKA_ID_CODECID, ff_mkv_codec_tags[j].str);

                    native_id = 1;

                    break;

                }

            }

        }

        if (codec->codec_id == AV_CODEC_ID_OPUS) {

            uint64_t codec_delay =av_rescale_q(codec->delay,

                                               (AVRational){1, codec->sample_rate},

                                               (AVRational){1, 1000000000});

            put_ebml_uint(pb, MATROSKA_ID_CODECDELAY, codec_delay);

            put_ebml_uint(pb, MATROSKA_ID_SEEKPREROLL, OPUS_SEEK_PREROLL);

        }

        if (mkv->mode == MODE_WEBM && !(codec->codec_id == AV_CODEC_ID_VP8 ||

                                        codec->codec_id == AV_CODEC_ID_VP9 ||

                                      ((codec->codec_id == AV_CODEC_ID_OPUS)&&(codec->strict_std_compliance <= FF_COMPLIANCE_EXPERIMENTAL)) ||

                                        codec->codec_id == AV_CODEC_ID_VORBIS ||

                                        codec->codec_id == AV_CODEC_ID_WEBVTT)) {

            av_log(s, AV_LOG_ERROR,

                   "Only VP8,VP9 video and Vorbis,Opus(experimental, use -strict -2) audio and WebVTT subtitles are supported for WebM.\n");

            return AVERROR(EINVAL);

        }

        switch (codec->codec_type) {

            case AVMEDIA_TYPE_VIDEO:

                put_ebml_uint(pb, MATROSKA_ID_TRACKTYPE, MATROSKA_TRACK_TYPE_VIDEO);

                if(st->avg_frame_rate.num && st->avg_frame_rate.den && 1.0/av_q2d(st->avg_frame_rate) > av_q2d(codec->time_base))

                    put_ebml_uint(pb, MATROSKA_ID_TRACKDEFAULTDURATION, 1E9/av_q2d(st->avg_frame_rate));

                else

                    put_ebml_uint(pb, MATROSKA_ID_TRACKDEFAULTDURATION, av_q2d(codec->time_base)*1E9);

                if (!native_id &&

                      ff_codec_get_tag(ff_codec_movvideo_tags, codec->codec_id) &&

                    (!ff_codec_get_tag(ff_codec_bmp_tags,   codec->codec_id)

                     || codec->codec_id == AV_CODEC_ID_SVQ1

                     || codec->codec_id == AV_CODEC_ID_SVQ3

                     || codec->codec_id == AV_CODEC_ID_CINEPAK))

                    qt_id = 1;

                if (qt_id)

                    put_ebml_string(pb, MATROSKA_ID_CODECID, "V_QUICKTIME");

                else if (!native_id) {

                    // if there is no mkv-specific codec ID, use VFW mode

                    put_ebml_string(pb, MATROSKA_ID_CODECID, "V_MS/VFW/FOURCC");

                    mkv->tracks[i].write_dts = 1;

                }

                subinfo = start_ebml_master(pb, MATROSKA_ID_TRACKVIDEO, 0);

                // XXX: interlace flag?

                put_ebml_uint (pb, MATROSKA_ID_VIDEOPIXELWIDTH , codec->width);

                put_ebml_uint (pb, MATROSKA_ID_VIDEOPIXELHEIGHT, codec->height);

                if ((tag = av_dict_get(st->metadata, "stereo_mode", NULL, 0)) ||

                    (tag = av_dict_get( s->metadata, "stereo_mode", NULL, 0))) {

                    // save stereo mode flag

                    uint64_t st_mode = MATROSKA_VIDEO_STEREO_MODE_COUNT;

                    for (j=0; j

                        if (!strcmp(tag->value, ff_matroska_video_stereo_mode[j])){

                            st_mode = j;

                            break;

                        }

                    if ((mkv->mode == MODE_WEBM && st_mode > 3 && st_mode != 11)

                        || st_mode >= MATROSKA_VIDEO_STEREO_MODE_COUNT) {

                        av_log(s, AV_LOG_ERROR,

                               "The specified stereo mode is not valid.\n");

                        return AVERROR(EINVAL);

                    } else

                        put_ebml_uint(pb, MATROSKA_ID_VIDEOSTEREOMODE, st_mode);

                }

                if ((tag = av_dict_get(st->metadata, "alpha_mode", NULL, 0)) ||

                    (tag = av_dict_get( s->metadata, "alpha_mode", NULL, 0)) ||

                    (codec->pix_fmt == AV_PIX_FMT_YUVA420P)) {

                    put_ebml_uint(pb, MATROSKA_ID_VIDEOALPHAMODE, 1);

                }

                if (st->sample_aspect_ratio.num) {

                    int64_t d_width = av_rescale(codec->width, st->sample_aspect_ratio.num, st->sample_aspect_ratio.den);

                    if (d_width > INT_MAX) {

                        av_log(s, AV_LOG_ERROR, "Overflow in display width\n");

                        return AVERROR(EINVAL);

                    }

                    put_ebml_uint(pb, MATROSKA_ID_VIDEODISPLAYWIDTH , d_width);

                    put_ebml_uint(pb, MATROSKA_ID_VIDEODISPLAYHEIGHT, codec->height);

                }

                if (codec->codec_id == AV_CODEC_ID_RAWVIDEO) {

                    uint32_t color_space = av_le2ne32(codec->codec_tag);

                    put_ebml_binary(pb, MATROSKA_ID_VIDEOCOLORSPACE, &color_space, sizeof(color_space));

                }

                end_ebml_master(pb, subinfo);

                break;

            case AVMEDIA_TYPE_AUDIO:

                put_ebml_uint(pb, MATROSKA_ID_TRACKTYPE, MATROSKA_TRACK_TYPE_AUDIO);

                if (!native_id)

                    // no mkv-specific ID, use ACM mode

                    put_ebml_string(pb, MATROSKA_ID_CODECID, "A_MS/ACM");

                subinfo = start_ebml_master(pb, MATROSKA_ID_TRACKAUDIO, 0);

                put_ebml_uint  (pb, MATROSKA_ID_AUDIOCHANNELS    , codec->channels);

                put_ebml_float (pb, MATROSKA_ID_AUDIOSAMPLINGFREQ, sample_rate);

                if (output_sample_rate)

                    put_ebml_float(pb, MATROSKA_ID_AUDIOOUTSAMPLINGFREQ, output_sample_rate);

                if (bit_depth)

                    put_ebml_uint(pb, MATROSKA_ID_AUDIOBITDEPTH, bit_depth);

                end_ebml_master(pb, subinfo);

                break;

            case AVMEDIA_TYPE_SUBTITLE:

                if (!native_id) {

                    av_log(s, AV_LOG_ERROR, "Subtitle codec %d is not supported.\n", codec->codec_id);

                    return AVERROR(ENOSYS);

                }

                if (mkv->mode != MODE_WEBM || codec->codec_id != AV_CODEC_ID_WEBVTT)

                    native_id = MATROSKA_TRACK_TYPE_SUBTITLE;

                put_ebml_uint(pb, MATROSKA_ID_TRACKTYPE, native_id);

                break;

            default:

                av_log(s, AV_LOG_ERROR, "Only audio, video, and subtitles are supported for Matroska.\n");

                return AVERROR(EINVAL);

        }

        if (mkv->mode != MODE_WEBM || codec->codec_id != AV_CODEC_ID_WEBVTT) {

            ret = mkv_write_codecprivate(s, pb, codec, native_id, qt_id);

            if (ret < 0) return ret;

        }

        end_ebml_master(pb, track);

        // ms precision is the de-facto standard timescale for mkv files

        avpriv_set_pts_info(st, 64, 1, 1000);

    }

    end_ebml_master(pb, tracks);

    return 0;

}

static int mkv_write_chapters(AVFormatContext *s)

{

    MatroskaMuxContext *mkv = s->priv_data;

    AVIOContext *pb = s->pb;

    ebml_master chapters, editionentry;

    AVRational scale = {1, 1E9};

    int i, ret;

    if (!s->nb_chapters || mkv->wrote_chapters)

        return 0;

    ret = mkv_add_seekhead_entry(mkv->main_seekhead, MATROSKA_ID_CHAPTERS, avio_tell(pb));

    if (ret < 0) return ret;

    chapters     = start_ebml_master(pb, MATROSKA_ID_CHAPTERS    , 0);

    editionentry = start_ebml_master(pb, MATROSKA_ID_EDITIONENTRY, 0);

    put_ebml_uint(pb, MATROSKA_ID_EDITIONFLAGDEFAULT, 1);

    put_ebml_uint(pb, MATROSKA_ID_EDITIONFLAGHIDDEN , 0);

    for (i = 0; i < s->nb_chapters; i++) {

        ebml_master chapteratom, chapterdisplay;

        AVChapter *c     = s->chapters[i];

        AVDictionaryEntry *t = NULL;

        chapteratom = start_ebml_master(pb, MATROSKA_ID_CHAPTERATOM, 0);

        put_ebml_uint(pb, MATROSKA_ID_CHAPTERUID, c->id + mkv->chapter_id_offset);

        put_ebml_uint(pb, MATROSKA_ID_CHAPTERTIMESTART,

                      av_rescale_q(c->start, c->time_base, scale));

        put_ebml_uint(pb, MATROSKA_ID_CHAPTERTIMEEND,

                      av_rescale_q(c->end,   c->time_base, scale));

        put_ebml_uint(pb, MATROSKA_ID_CHAPTERFLAGHIDDEN , 0);

        put_ebml_uint(pb, MATROSKA_ID_CHAPTERFLAGENABLED, 1);

        if ((t = av_dict_get(c->metadata, "title", NULL, 0))) {

            chapterdisplay = start_ebml_master(pb, MATROSKA_ID_CHAPTERDISPLAY, 0);

            put_ebml_string(pb, MATROSKA_ID_CHAPSTRING, t->value);

            put_ebml_string(pb, MATROSKA_ID_CHAPLANG  , "und");

            end_ebml_master(pb, chapterdisplay);

        }

        end_ebml_master(pb, chapteratom);

    }

    end_ebml_master(pb, editionentry);

    end_ebml_master(pb, chapters);

    mkv->wrote_chapters = 1;

    return 0;

}

static void mkv_write_simpletag(AVIOContext *pb, AVDictionaryEntry *t)

{

    uint8_t *key = av_strdup(t->key);

    uint8_t *p   = key;

    const uint8_t *lang = NULL;

    ebml_master tag;

    if ((p = strrchr(p, '-')) &&

        (lang = av_convert_lang_to(p + 1, AV_LANG_ISO639_2_BIBL)))

        *p = 0;

    p = key;

    while (*p) {

        if (*p == ' ')

            *p = '_';

        else if (*p >= 'a' && *p <= 'z')

            *p -= 'a' - 'A';

        p++;

    }

    tag = start_ebml_master(pb, MATROSKA_ID_SIMPLETAG, 0);

    put_ebml_string(pb, MATROSKA_ID_TAGNAME, key);

    if (lang)

        put_ebml_string(pb, MATROSKA_ID_TAGLANG, lang);

    put_ebml_string(pb, MATROSKA_ID_TAGSTRING, t->value);

    end_ebml_master(pb, tag);

    av_freep(&key);

}

static int mkv_write_tag(AVFormatContext *s, AVDictionary *m, unsigned int elementid,

                         unsigned int uid, ebml_master *tags)

{

    MatroskaMuxContext *mkv = s->priv_data;

    ebml_master tag, targets;

    AVDictionaryEntry *t = NULL;

    int ret;

    if (!tags->pos) {

        ret = mkv_add_seekhead_entry(mkv->main_seekhead, MATROSKA_ID_TAGS, avio_tell(s->pb));

        if (ret < 0) return ret;

        *tags = start_ebml_master(s->pb, MATROSKA_ID_TAGS, 0);

    }

    tag     = start_ebml_master(s->pb, MATROSKA_ID_TAG,        0);

    targets = start_ebml_master(s->pb, MATROSKA_ID_TAGTARGETS, 0);

    if (elementid)

        put_ebml_uint(s->pb, elementid, uid);

    end_ebml_master(s->pb, targets);

    while ((t = av_dict_get(m, "", t, AV_DICT_IGNORE_SUFFIX)))

        if (av_strcasecmp(t->key, "title") && av_strcasecmp(t->key, "stereo_mode"))

            mkv_write_simpletag(s->pb, t);

    end_ebml_master(s->pb, tag);

    return 0;

}

static int mkv_check_tag(AVDictionary *m)

{

    AVDictionaryEntry *t = NULL;

    while ((t = av_dict_get(m, "", t, AV_DICT_IGNORE_SUFFIX)))

        if (av_strcasecmp(t->key, "title") && av_strcasecmp(t->key, "stereo_mode"))

            return 1;

    return 0;

}

static int mkv_write_tags(AVFormatContext *s)

{

    MatroskaMuxContext *mkv = s->priv_data;

    ebml_master tags = {0};

    int i, ret;

    ff_metadata_conv_ctx(s, ff_mkv_metadata_conv, NULL);

    if (mkv_check_tag(s->metadata)) {

        ret = mkv_write_tag(s, s->metadata, 0, 0, &tags);

        if (ret < 0) return ret;

    }

    for (i = 0; i < s->nb_streams; i++) {

        AVStream *st = s->streams[i];

        if (!mkv_check_tag(st->metadata))

            continue;

        ret = mkv_write_tag(s, st->metadata, MATROSKA_ID_TAGTARGETS_TRACKUID, i + 1, &tags);

        if (ret < 0) return ret;

    }

    for (i = 0; i < s->nb_chapters; i++) {

        AVChapter *ch = s->chapters[i];

        if (!mkv_check_tag(ch->metadata))

            continue;

        ret = mkv_write_tag(s, ch->metadata, MATROSKA_ID_TAGTARGETS_CHAPTERUID, ch->id + mkv->chapter_id_offset, &tags);

        if (ret < 0) return ret;

    }

    if (tags.pos)

        end_ebml_master(s->pb, tags);

    return 0;

}

static int mkv_write_attachments(AVFormatContext *s)

{

    MatroskaMuxContext *mkv = s->priv_data;

    AVIOContext *pb = s->pb;

    ebml_master attachments;

    AVLFG c;

    int i, ret;

    if (!mkv->have_attachments)

        return 0;

    av_lfg_init(&c, av_get_random_seed());

    ret = mkv_add_seekhead_entry(mkv->main_seekhead, MATROSKA_ID_ATTACHMENTS, avio_tell(pb));

    if (ret < 0) return ret;

    attachments = start_ebml_master(pb, MATROSKA_ID_ATTACHMENTS, 0);

    for (i = 0; i < s->nb_streams; i++) {

        AVStream *st = s->streams[i];

        ebml_master attached_file;

        AVDictionaryEntry *t;

        const char *mimetype = NULL;

        uint64_t fileuid;

        if (st->codec->codec_type != AVMEDIA_TYPE_ATTACHMENT)

            continue;

        attached_file = start_ebml_master(pb, MATROSKA_ID_ATTACHEDFILE, 0);

        if (t = av_dict_get(st->metadata, "title", NULL, 0))

            put_ebml_string(pb, MATROSKA_ID_FILEDESC, t->value);

        if (!(t = av_dict_get(st->metadata, "filename", NULL, 0))) {

            av_log(s, AV_LOG_ERROR, "Attachment stream %d has no filename tag.\n", i);

            return AVERROR(EINVAL);

        }

        put_ebml_string(pb, MATROSKA_ID_FILENAME, t->value);

        if (t = av_dict_get(st->metadata, "mimetype", NULL, 0))

            mimetype = t->value;

        else if (st->codec->codec_id != AV_CODEC_ID_NONE ) {

            int i;

            for (i = 0; ff_mkv_mime_tags[i].id != AV_CODEC_ID_NONE; i++)

                if (ff_mkv_mime_tags[i].id == st->codec->codec_id) {

                    mimetype = ff_mkv_mime_tags[i].str;

                    break;

                }

        }

        if (!mimetype) {

            av_log(s, AV_LOG_ERROR, "Attachment stream %d has no mimetype tag and "

                                    "it cannot be deduced from the codec id.\n", i);

            return AVERROR(EINVAL);

        }

        if (st->codec->flags & CODEC_FLAG_BITEXACT) {

            struct AVSHA *sha = av_sha_alloc();

            uint8_t digest[20];

            if (!sha)

                return AVERROR(ENOMEM);

            av_sha_init(sha, 160);

            av_sha_update(sha, st->codec->extradata, st->codec->extradata_size);

            av_sha_final(sha, digest);

            av_free(sha);

            fileuid = AV_RL64(digest);

        } else {

            fileuid = av_lfg_get(&c);

        }

        av_log(s, AV_LOG_VERBOSE, "Using %.16"PRIx64" for attachment %d\n",

               fileuid, i);

        put_ebml_string(pb, MATROSKA_ID_FILEMIMETYPE, mimetype);

        put_ebml_binary(pb, MATROSKA_ID_FILEDATA, st->codec->extradata, st->codec->extradata_size);

        put_ebml_uint(pb, MATROSKA_ID_FILEUID, fileuid);

        end_ebml_master(pb, attached_file);

    }

    end_ebml_master(pb, attachments);

    return 0;

}

static int mkv_write_header(AVFormatContext *s)

{

    MatroskaMuxContext *mkv = s->priv_data;

    AVIOContext *pb = s->pb;

    ebml_master ebml_header, segment_info;

    AVDictionaryEntry *tag;

    int ret, i;

    if (!strcmp(s->oformat->name, "webm")) mkv->mode = MODE_WEBM;

    else                                   mkv->mode = MODE_MATROSKAv2;

    if (s->avoid_negative_ts < 0)

        s->avoid_negative_ts = 1;

    for (i = 0; i < s->nb_streams; i++)

        if (s->streams[i]->codec->codec_id == AV_CODEC_ID_ATRAC3 ||

            s->streams[i]->codec->codec_id == AV_CODEC_ID_COOK ||

            s->streams[i]->codec->codec_id == AV_CODEC_ID_RA_288 ||

            s->streams[i]->codec->codec_id == AV_CODEC_ID_SIPR ||

            s->streams[i]->codec->codec_id == AV_CODEC_ID_RV10 ||

            s->streams[i]->codec->codec_id == AV_CODEC_ID_RV20) {

            av_log(s, AV_LOG_ERROR,

                   "The Matroska muxer does not yet support muxing %s\n",

                   avcodec_get_name(s->streams[i]->codec->codec_id));

            return AVERROR_PATCHWELCOME;

        }

    mkv->tracks = av_mallocz(s->nb_streams * sizeof(*mkv->tracks));

    if (!mkv->tracks)

        return AVERROR(ENOMEM);

    ebml_header = start_ebml_master(pb, EBML_ID_HEADER, 0);

    put_ebml_uint   (pb, EBML_ID_EBMLVERSION        ,           1);

    put_ebml_uint   (pb, EBML_ID_EBMLREADVERSION    ,           1);

    put_ebml_uint   (pb, EBML_ID_EBMLMAXIDLENGTH    ,           4);

    put_ebml_uint   (pb, EBML_ID_EBMLMAXSIZELENGTH  ,           8);

    put_ebml_string (pb, EBML_ID_DOCTYPE            , s->oformat->name);

    put_ebml_uint   (pb, EBML_ID_DOCTYPEVERSION     ,           4);

    put_ebml_uint   (pb, EBML_ID_DOCTYPEREADVERSION ,           2);

    end_ebml_master(pb, ebml_header);

    mkv->segment = start_ebml_master(pb, MATROSKA_ID_SEGMENT, 0);

    mkv->segment_offset = avio_tell(pb);

    // we write 2 seek heads - one at the end of the file to point to each

    // cluster, and one at the beginning to point to all other level one

    // elements (including the seek head at the end of the file), which

    // isn't more than 10 elements if we only write one of each other

    // currently defined level 1 element

    mkv->main_seekhead    = mkv_start_seekhead(pb, mkv->segment_offset, 10);

    if (!mkv->main_seekhead)

        return AVERROR(ENOMEM);

    ret = mkv_add_seekhead_entry(mkv->main_seekhead, MATROSKA_ID_INFO, avio_tell(pb));

    if (ret < 0) return ret;

    segment_info = start_ebml_master(pb, MATROSKA_ID_INFO, 0);

    put_ebml_uint(pb, MATROSKA_ID_TIMECODESCALE, 1000000);

    if ((tag = av_dict_get(s->metadata, "title", NULL, 0)))

        put_ebml_string(pb, MATROSKA_ID_TITLE, tag->value);

    if (!(s->streams[0]->codec->flags & CODEC_FLAG_BITEXACT)) {

        uint32_t segment_uid[4];

        AVLFG lfg;

        av_lfg_init(&lfg, av_get_random_seed());

        for (i = 0; i < 4; i++)

            segment_uid[i] = av_lfg_get(&lfg);

        put_ebml_string(pb, MATROSKA_ID_MUXINGAPP , LIBAVFORMAT_IDENT);

        put_ebml_string(pb, MATROSKA_ID_WRITINGAPP, LIBAVFORMAT_IDENT);

        put_ebml_binary(pb, MATROSKA_ID_SEGMENTUID, segment_uid, 16);

    } else {

        const char *ident = "Lavf";

        put_ebml_string(pb, MATROSKA_ID_MUXINGAPP , ident);

        put_ebml_string(pb, MATROSKA_ID_WRITINGAPP, ident);

    }

    if (tag = av_dict_get(s->metadata, "creation_time", NULL, 0)) {

        // Adjust time so it's relative to 2001-01-01 and convert to nanoseconds.

        int64_t date_utc = (ff_iso8601_to_unix_time(tag->value) - 978307200) * 1000000000;

        uint8_t date_utc_buf[8];

        AV_WB64(date_utc_buf, date_utc);

        put_ebml_binary(pb, MATROSKA_ID_DATEUTC, date_utc_buf, 8);

    }

    // reserve space for the duration

    mkv->duration = 0;

    mkv->duration_offset = avio_tell(pb);

    put_ebml_void(pb, 11);                  // assumes double-precision float to be written

    end_ebml_master(pb, segment_info);

    ret = mkv_write_tracks(s);

    if (ret < 0) return ret;

    for (i = 0; i < s->nb_chapters; i++)

        mkv->chapter_id_offset = FFMAX(mkv->chapter_id_offset, 1LL - s->chapters[i]->id);

    if (mkv->mode != MODE_WEBM) {

        ret = mkv_write_chapters(s);