/*

  * 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 <stdint.h>
 

 #include "avc.h"

 #include "hevc.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 "vorbiscomment.h"

 #include "wv.h"

 
 #include "libavutil/avstring.h"

 #include "libavutil/channel_layout.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             stream_idx;

     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;

     int64_t         ts_offset;

 } 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;

     int is_dash;
     int dash_track_number;

 
     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_sint(AVIOContext *pb, unsigned int elementid, int64_t val)
 {
     int i, bytes = 1;

     uint64_t tmp = 2*(val < 0 ? val^-1 : 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, int tracknum, 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].stream_idx    = stream;
     cues->entries[cues->num_entries].tracknum      = tracknum;

     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(AVFormatContext *s, mkv_cues *cues, mkv_track *tracks, int num_tracks)

 {

     AVIOContext *pb = s->pb;

     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].stream_idx;

             av_assert0(tracknum>=0 && tracknum<num_tracks);

             if (tracks[tracknum].has_cue && s->streams[tracknum]->codec->codec_type != AVMEDIA_TYPE_SUBTITLE)

                 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 int put_flac_codecpriv(AVFormatContext *s,
                               AVIOContext *pb, AVCodecContext *codec)
 {
     int write_comment = (codec->channel_layout &&
                          !(codec->channel_layout & ~0x3ffffULL) &&
                          !ff_flac_is_native_layout(codec->channel_layout));

     int ret = ff_flac_write_header(pb, codec->extradata, codec->extradata_size,
                                    !write_comment);

 
     if (ret < 0)
         return ret;
 
     if (write_comment) {
         const char *vendor = (s->flags & AVFMT_FLAG_BITEXACT) ?

                              "Lavf" : LIBAVFORMAT_IDENT;

         AVDictionary *dict = NULL;
         uint8_t buf[32], *data, *p;
         int len;
 
         snprintf(buf, sizeof(buf), "0x%"PRIx64, codec->channel_layout);
         av_dict_set(&dict, "WAVEFORMATEXTENSIBLE_CHANNEL_MASK", buf, 0);
 
         len = ff_vorbiscomment_length(dict, vendor);
         data = av_malloc(len + 4);
         if (!data) {
             av_dict_free(&dict);
             return AVERROR(ENOMEM);
         }
 
         data[0] = 0x84;
         AV_WB24(data + 1, len);
 
         p = data + 4;
         ff_vorbiscomment_write(&p, &dict, vendor);
 
         avio_write(pb, data, len + 4);
 
         av_freep(&data);
         av_dict_free(&dict);
     }
 
     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_native_codecprivate(AVFormatContext *s,
                                          AVCodecContext *codec,
                                          AVIOContext *dyn_cp)
 {
     switch (codec->codec_id) {
     case AV_CODEC_ID_VORBIS:
     case AV_CODEC_ID_THEORA:
         return put_xiph_codecpriv(s, dyn_cp, codec);
     case AV_CODEC_ID_FLAC:
         return put_flac_codecpriv(s, dyn_cp, codec);
     case AV_CODEC_ID_WAVPACK:
         return put_wv_codecpriv(dyn_cp, codec);
     case AV_CODEC_ID_H264:
         return ff_isom_write_avcc(dyn_cp, codec->extradata,
                                   codec->extradata_size);
     case AV_CODEC_ID_HEVC:
         return ff_isom_write_hvcc(dyn_cp, codec->extradata,
                                   codec->extradata_size, 0);
     case 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.");
             return AVERROR_INVALIDDATA;
         } else
             avio_write(dyn_cp, codec->extradata + 12,
                        codec->extradata_size - 12);
         break;
     default:

         if (codec->codec_id == AV_CODEC_ID_PRORES &&
             ff_codec_get_id(ff_codec_movvideo_tags, codec->codec_tag) == AV_CODEC_ID_PRORES) {
             avio_wl32(dyn_cp, codec->codec_tag);
         } else if (codec->extradata_size && codec->codec_id != AV_CODEC_ID_TTA)
             avio_write(dyn_cp, codec->extradata, codec->extradata_size);

     }
 
     return 0;
 }
 

 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) {

         ret = mkv_write_native_codecprivate(s, codec, dyn_cp);

     } 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) {
                 if (   ff_codec_get_id(ff_codec_movvideo_tags, codec->codec_tag) == codec->codec_id

                     && ff_codec_get_id(ff_codec_movvideo_tags, AV_RL32(codec->extradata + 4)) != codec->codec_id

                 ) {
                     int i;
                     avio_wb32(dyn_cp, 0x5a + codec->extradata_size);
                     avio_wl32(dyn_cp, codec->codec_tag);

                     for(i = 0; i < 0x5a - 8; i++)

                         avio_w8(dyn_cp, 0);
                 }

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

             }

         } else {

             if (!ff_codec_get_tag(ff_codec_bmp_tags, codec->codec_id))
                 av_log(s, AV_LOG_WARNING, "codec %s is not supported by this format\n",
                        avcodec_get_name(codec->codec_id));
 

             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, 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, FF_PUT_WAV_HEADER_FORCE_WAVEFORMATEX);

     }

     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_stereo_mode(AVFormatContext *s, AVIOContext *pb, int st_mode,

                                   int mode)
 {

     if ((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);

     return 0;

 }
 

 static int mkv_write_track(AVFormatContext *s, MatroskaMuxContext *mkv,

                            int i, AVIOContext *pb, int default_stream_exists)

 {

     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;

     int display_width_div = 1;
     int display_height_div = 1;

     int j, ret;
     AVDictionaryEntry *tag;
 
     // ms precision is the de-facto standard timescale for mkv files
     avpriv_set_pts_info(st, 64, 1, 1000);
 
     if (codec->codec_type == AVMEDIA_TYPE_ATTACHMENT) {
         mkv->have_attachments = 1;
         return 0;

     }

     if (!bit_depth && codec->codec_id != AV_CODEC_ID_ADPCM_G726)

         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,
                    mkv->is_dash ? mkv->dash_track_number : i + 1);
     put_ebml_uint (pb, MATROSKA_ID_TRACKUID,
                    mkv->is_dash ? mkv->dash_track_number : 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_type == AVMEDIA_TYPE_AUDIO && codec->delay && codec->codec_id == AV_CODEC_ID_OPUS) {
 //         mkv->tracks[i].ts_offset = av_rescale_q(codec->delay,
 //                                                 (AVRational){ 1, codec->sample_rate },
 //                                                 st->time_base);

         put_ebml_uint(pb, MATROSKA_ID_CODECDELAY,
                       av_rescale_q(codec->delay, (AVRational){ 1, codec->sample_rate },
                                    (AVRational){ 1, 1000000000 }));
     }

     if (codec->codec_id == AV_CODEC_ID_OPUS) {
         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->codec_id == AV_CODEC_ID_VORBIS ||
                                     codec->codec_id == AV_CODEC_ID_WEBVTT)) {

         av_log(s, AV_LOG_ERROR,

                "Only VP8 or VP9 video and Vorbis or Opus 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 > 0 && st->avg_frame_rate.den > 0
            && 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))) {

             int st_mode = MATROSKA_VIDEO_STEREO_MODE_COUNT;

 
             for (j=0; j<MATROSKA_VIDEO_STEREO_MODE_COUNT; j++)
                 if (!strcmp(tag->value, ff_matroska_video_stereo_mode[j])){
                     st_mode = j;

                     break;

                 }
 

             if (mkv_write_stereo_mode(s, pb, st_mode, mkv->mode) < 0)

                 return AVERROR(EINVAL);
 
             switch (st_mode) {
             case 1:
             case 8:
             case 9:
             case 11:
                 display_width_div = 2;

                 break;

             case 2:
             case 3:
             case 6:
             case 7:
                 display_height_div = 2;

                 break;

             }

         }

         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 / display_width_div);
             put_ebml_uint(pb, MATROSKA_ID_VIDEODISPLAYHEIGHT, codec->height / display_height_div);
         } else if (display_width_div != 1 || display_height_div != 1) {
             put_ebml_uint(pb, MATROSKA_ID_VIDEODISPLAYWIDTH , codec->width / display_width_div);
             put_ebml_uint(pb, MATROSKA_ID_VIDEODISPLAYHEIGHT, codec->height / display_height_div);

         }

         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);

     return 0;
 }

 static int mkv_write_tracks(AVFormatContext *s)
 {
     MatroskaMuxContext *mkv = s->priv_data;
     AVIOContext *pb = s->pb;
     ebml_master tracks;

     int i, 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++) {
         ret = mkv_write_track(s, mkv, i, pb, default_stream_exists);

         if (ret < 0)
             return ret;

     }
     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") &&

             av_strcasecmp(t->key, "encoding_tool"))

             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 (s->flags & AVFMT_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, version = 2;

     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;
 

     if (mkv->mode != MODE_WEBM ||
         av_dict_get(s->metadata, "stereo_mode", NULL, 0) ||
         av_dict_get(s->metadata, "alpha_mode", NULL, 0))
         version = 4;
 
     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;
         }

         if (s->streams[i]->codec->codec_id == AV_CODEC_ID_OPUS ||
             av_dict_get(s->streams[i]->metadata, "stereo_mode", NULL, 0) ||
             av_dict_get(s->streams[i]->metadata, "alpha_mode", NULL, 0))
             version = 4;
     }

     mkv->tracks = av_mallocz_array(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     ,     version);

     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->flags & AVFMT_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);

         if ((tag = av_dict_get(s->metadata, "encoding_tool", NULL, 0)))
             put_ebml_string(pb, MATROSKA_ID_WRITINGAPP, tag->value);
         else
             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);

         if (ret < 0)
             return ret;

 
         ret = mkv_write_tags(s);

         if (ret < 0)
             return ret;

 
         ret = mkv_write_attachments(s);

         if (ret < 0)
             return ret;

     }

     if (!s->pb->seekable)

         mkv_write_seekhead(pb, mkv->main_seekhead);
 

     mkv->cues = mkv_start_cues(mkv->segment_offset);
     if (mkv->cues == NULL)

         return AVERROR(ENOMEM);

     if (pb->seekable && mkv->reserve_cues_space) {
         mkv->cues_pos = avio_tell(pb);
         put_ebml_void(pb, mkv->reserve_cues_space);
     }
 

     av_init_packet(&mkv->cur_audio_pkt);
     mkv->cur_audio_pkt.size = 0;

     mkv->cluster_pos = -1;

     avio_flush(pb);

 
     // start a new cluster every 5 MB or 5 sec, or 32k / 1 sec for streaming or
     // after 4k and on a keyframe
     if (pb->seekable) {
         if (mkv->cluster_time_limit < 0)
             mkv->cluster_time_limit = 5000;
         if (mkv->cluster_size_limit < 0)
             mkv->cluster_size_limit = 5 * 1024 * 1024;
     } else {
         if (mkv->cluster_time_limit < 0)
             mkv->cluster_time_limit = 1000;
         if (mkv->cluster_size_limit < 0)
             mkv->cluster_size_limit = 32 * 1024;
     }
 

     return 0;
 }
 

 static int mkv_blockgroup_size(int pkt_size)

 {

     int size = pkt_size + 4;

     size += ebml_num_size(size);

     size += 2;              // EBML ID for block and block duration
     size += 8;              // max size of block duration

     size += ebml_num_size(size);

     size += 1;              // blockgroup EBML ID
     return size;
 }
 

 static int ass_get_duration(const uint8_t *p)
 {
     int sh, sm, ss, sc, eh, em, es, ec;
     uint64_t start, end;
 
     if (sscanf(p, "%*[^,],%d:%d:%d%*c%d,%d:%d:%d%*c%d",
                &sh, &sm, &ss, &sc, &eh, &em, &es, &ec) != 8)
         return 0;

     start = 3600000LL * sh + 60000LL * sm + 1000LL * ss + 10LL * sc;
     end   = 3600000LL * eh + 60000LL * em + 1000LL * es + 10LL * ec;

     return end - start;
 }
 

 #if FF_API_ASS_SSA

 /* Writes the contents of pkt to a block, using the data starting at *datap.
  * If pkt corresponds to more than one block, this writes the contents of the first block
  * (starting from *datap) and updates *datap so it points to the beginning of the data
  * corresponding to the next block.
  */

 static int mkv_write_ass_block(AVFormatContext *s, AVIOContext *pb,
                                AVPacket *pkt, uint8_t **datap)

 {
     MatroskaMuxContext *mkv = s->priv_data;

     int i, layer = 0, size, line_size, data_size = pkt->size - (*datap - pkt->data);
     uint8_t *start, *end, *data = *datap;

     ebml_master blockgroup;
     char buffer[2048];
 
         int duration = ass_get_duration(data);

         end          = memchr(data, '\n', data_size);
         size         = line_size = end ? end - data + 1 : data_size;
         size        -= end ? (end[-1] == '\r') + 1 : 0;
         start        = data;
         for (i = 0; i < 3; i++, start++)
             if (!(start = memchr(start, ',', size - (start - data))))

                 return duration;

         size -= start - data;
         sscanf(data, "Dialogue: %d,", &layer);

         i = snprintf(buffer, sizeof(buffer), "%" PRId64 ",%d,",

                      s->streams[pkt->stream_index]->nb_frames, layer);

         size = FFMIN(i + size, sizeof(buffer));
         memcpy(buffer + i, start, size - i);

         av_log(s, AV_LOG_DEBUG,
                "Writing block at offset %" PRIu64 ", size %d, "

                "pts %" PRId64 ", duration %d\n",

                avio_tell(pb), size, pkt->pts, duration);

         blockgroup = start_ebml_master(pb, MATROSKA_ID_BLOCKGROUP,
                                        mkv_blockgroup_size(size));

         put_ebml_id(pb, MATROSKA_ID_BLOCK);

         put_ebml_num(pb, size + 4, 0);
         // this assumes stream_index is less than 126
         avio_w8(pb, 0x80 | (pkt->stream_index + 1));

         avio_wb16(pb, pkt->pts - mkv->cluster_pts);
         avio_w8(pb, 0);
         avio_write(pb, buffer, size);

         put_ebml_uint(pb, MATROSKA_ID_BLOCKDURATION, duration);
         end_ebml_master(pb, blockgroup);
 

         *datap += line_size;

     return duration;

 }

 #endif

 static int mkv_strip_wavpack(const uint8_t *src, uint8_t **pdst, int *size)
 {
     uint8_t *dst;
     int srclen = *size;
     int offset = 0;
     int ret;
 
     dst = av_malloc(srclen);
     if (!dst)
         return AVERROR(ENOMEM);
 
     while (srclen >= WV_HEADER_SIZE) {
         WvHeader header;
 
         ret = ff_wv_parse_header(&header, src);
         if (ret < 0)
             goto fail;
         src    += WV_HEADER_SIZE;
         srclen -= WV_HEADER_SIZE;
 
         if (srclen < header.blocksize) {
             ret = AVERROR_INVALIDDATA;
             goto fail;
         }
 
         if (header.initial) {
             AV_WL32(dst + offset, header.samples);
             offset += 4;
         }
         AV_WL32(dst + offset,     header.flags);
         AV_WL32(dst + offset + 4, header.crc);
         offset += 8;
 
         if (!(header.initial && header.final)) {
             AV_WL32(dst + offset, header.blocksize);
             offset += 4;
         }
 
         memcpy(dst + offset, src, header.blocksize);
         src    += header.blocksize;
         srclen -= header.blocksize;
         offset += header.blocksize;
     }
 
     *pdst = dst;
     *size = offset;
 
     return 0;
 fail:
     av_freep(&dst);
     return ret;
 }
 

 static void mkv_write_block(AVFormatContext *s, AVIOContext *pb,

                             unsigned int blockid, AVPacket *pkt, int flags)

 {
     MatroskaMuxContext *mkv = s->priv_data;

     AVCodecContext *codec = s->streams[pkt->stream_index]->codec;

     uint8_t *data = NULL, *side_data = NULL;
     int offset = 0, size = pkt->size, side_data_size = 0;

     int64_t ts = mkv->tracks[pkt->stream_index].write_dts ? pkt->dts : pkt->pts;

     uint64_t additional_id = 0;
     int64_t discard_padding = 0;

     ebml_master block_group, block_additions, block_more;

     av_log(s, AV_LOG_DEBUG, "Writing block at offset %" PRIu64 ", size %d, "
            "pts %" PRId64 ", dts %" PRId64 ", duration %d, flags %d\n",

            avio_tell(pb), pkt->size, pkt->pts, pkt->dts, pkt->duration, flags);

     if (codec->codec_id == AV_CODEC_ID_H264 && codec->extradata_size > 0 &&

         (AV_RB24(codec->extradata) == 1 || AV_RB32(codec->extradata) == 1))
         ff_avc_parse_nal_units_buf(pkt->data, &data, &size);

     else if (codec->codec_id == AV_CODEC_ID_HEVC && codec->extradata_size > 6 &&
              (AV_RB24(codec->extradata) == 1 || AV_RB32(codec->extradata) == 1))
         /* extradata is Annex B, assume the bitstream is too and convert it */
         ff_hevc_annexb2mp4_buf(pkt->data, &data, &size, 0, NULL);

     else if (codec->codec_id == AV_CODEC_ID_WAVPACK) {
         int ret = mkv_strip_wavpack(pkt->data, &data, &size);
         if (ret < 0) {
             av_log(s, AV_LOG_ERROR, "Error stripping a WavPack packet.\n");
             return;
         }
     } else

         data = pkt->data;

 
     if (codec->codec_id == AV_CODEC_ID_PRORES) {
         /* Matroska specification requires to remove the first QuickTime atom
          */

         size  -= 8;

         offset = 8;
     }
 

     side_data = av_packet_get_side_data(pkt,

                                         AV_PKT_DATA_SKIP_SAMPLES,
                                         &side_data_size);
 
     if (side_data && side_data_size >= 10) {
         discard_padding = av_rescale_q(AV_RL32(side_data + 4),
                                        (AVRational){1, codec->sample_rate},
                                        (AVRational){1, 1000000000});
     }
 
     side_data = av_packet_get_side_data(pkt,

                                         AV_PKT_DATA_MATROSKA_BLOCKADDITIONAL,
                                         &side_data_size);
     if (side_data) {
         additional_id = AV_RB64(side_data);
         side_data += 8;
         side_data_size -= 8;
     }
 

     if ((side_data_size && additional_id == 1) || discard_padding) {

         block_group = start_ebml_master(pb, MATROSKA_ID_BLOCKGROUP, 0);

         blockid = MATROSKA_ID_BLOCK;
     }
 
     put_ebml_id(pb, blockid);

     put_ebml_num(pb, size + 4, 0);

     // this assumes stream_index is less than 126
     avio_w8(pb, 0x80 | (mkv->is_dash ? mkv->dash_track_number : (pkt->stream_index + 1)));

     avio_wb16(pb, ts - mkv->cluster_pts);
     avio_w8(pb, flags);
     avio_write(pb, data + offset, size);
     if (data != pkt->data)
         av_free(data);
 

     if (discard_padding) {

         put_ebml_sint(pb, MATROSKA_ID_DISCARDPADDING, discard_padding);

     }
 

     if (side_data_size && additional_id == 1) {

         block_additions = start_ebml_master(pb, MATROSKA_ID_BLOCKADDITIONS, 0);
         block_more = start_ebml_master(pb, MATROSKA_ID_BLOCKMORE, 0);
         put_ebml_uint(pb, MATROSKA_ID_BLOCKADDID, 1);
         put_ebml_id(pb, MATROSKA_ID_BLOCKADDITIONAL);
         put_ebml_num(pb, side_data_size, 0);
         avio_write(pb, side_data, side_data_size);
         end_ebml_master(pb, block_more);
         end_ebml_master(pb, block_additions);

     }
     if ((side_data_size && additional_id == 1) || discard_padding) {

         end_ebml_master(pb, block_group);
     }

 }
 

 static int srt_get_duration(uint8_t **buf)
 {
     int i, duration = 0;
 

     for (i = 0; i < 2 && !duration; i++) {

         int s_hour, s_min, s_sec, s_hsec, e_hour, e_min, e_sec, e_hsec;
         if (sscanf(*buf, "%d:%2d:%2d%*1[,.]%3d --> %d:%2d:%2d%*1[,.]%3d",
                    &s_hour, &s_min, &s_sec, &s_hsec,
                    &e_hour, &e_min, &e_sec, &e_hsec) == 8) {

             s_min += 60 * s_hour;
             e_min += 60 * e_hour;
             s_sec += 60 * s_min;
 
             e_sec  += 60 * e_min;
             s_hsec += 1000 * s_sec;
             e_hsec += 1000 * e_sec;
 

             duration = e_hsec - s_hsec;
         }

         *buf += ff_subtitles_next_line(*buf);

     }
     return duration;
 }
 

 static int mkv_write_srt_blocks(AVFormatContext *s, AVIOContext *pb,
                                 AVPacket *pkt)

 {
     ebml_master blockgroup;
     AVPacket pkt2 = *pkt;
     int64_t duration = srt_get_duration(&pkt2.data);
     pkt2.size -= pkt2.data - pkt->data;
 
     blockgroup = start_ebml_master(pb, MATROSKA_ID_BLOCKGROUP,
                                    mkv_blockgroup_size(pkt2.size));
     mkv_write_block(s, pb, MATROSKA_ID_BLOCK, &pkt2, 0);
     put_ebml_uint(pb, MATROSKA_ID_BLOCKDURATION, duration);
     end_ebml_master(pb, blockgroup);
 
     return duration;
 }
 

 static int mkv_write_vtt_blocks(AVFormatContext *s, AVIOContext *pb, AVPacket *pkt)
 {
     MatroskaMuxContext *mkv = s->priv_data;
     ebml_master blockgroup;
     int id_size, settings_size, size;
     uint8_t *id, *settings;
     int64_t ts = mkv->tracks[pkt->stream_index].write_dts ? pkt->dts : pkt->pts;
     const int flags = 0;
 
     id_size = 0;
     id = av_packet_get_side_data(pkt, AV_PKT_DATA_WEBVTT_IDENTIFIER,
                                  &id_size);
 
     settings_size = 0;
     settings = av_packet_get_side_data(pkt, AV_PKT_DATA_WEBVTT_SETTINGS,
                                        &settings_size);
 
     size = id_size + 1 + settings_size + 1 + pkt->size;
 
     av_log(s, AV_LOG_DEBUG, "Writing block at offset %" PRIu64 ", size %d, "
            "pts %" PRId64 ", dts %" PRId64 ", duration %d, flags %d\n",
            avio_tell(pb), size, pkt->pts, pkt->dts, pkt->duration, flags);
 
     blockgroup = start_ebml_master(pb, MATROSKA_ID_BLOCKGROUP, mkv_blockgroup_size(size));
 
     put_ebml_id(pb, MATROSKA_ID_BLOCK);

     put_ebml_num(pb, size + 4, 0);

     avio_w8(pb, 0x80 | (pkt->stream_index + 1));     // this assumes stream_index is less than 126
     avio_wb16(pb, ts - mkv->cluster_pts);
     avio_w8(pb, flags);
     avio_printf(pb, "%.*s\n%.*s\n%.*s", id_size, id, settings_size, settings, pkt->size, pkt->data);
 
     put_ebml_uint(pb, MATROSKA_ID_BLOCKDURATION, pkt->duration);
     end_ebml_master(pb, blockgroup);
 
     return pkt->duration;
 }
 

 static void mkv_flush_dynbuf(AVFormatContext *s)
 {
     MatroskaMuxContext *mkv = s->priv_data;
     int bufsize;
     uint8_t *dyn_buf;
 
     if (!mkv->dyn_bc)
         return;
 

     bufsize = avio_close_dyn_buf(mkv->dyn_bc, &dyn_buf);

     avio_write(s->pb, dyn_buf, bufsize);

     av_free(dyn_buf);
     mkv->dyn_bc = NULL;
 }
 

 static int mkv_write_packet_internal(AVFormatContext *s, AVPacket *pkt, int add_cue)

 {

     MatroskaMuxContext *mkv = s->priv_data;

     AVIOContext *pb         = s->pb;
     AVCodecContext *codec   = s->streams[pkt->stream_index]->codec;
     int keyframe            = !!(pkt->flags & AV_PKT_FLAG_KEY);
     int duration            = pkt->duration;

     int ret;

     int64_t ts = mkv->tracks[pkt->stream_index].write_dts ? pkt->dts : pkt->pts;

     int64_t relative_packet_pos;

     uint8_t *data_offset = pkt->data;
     int dash_tracknum = mkv->is_dash ? mkv->dash_track_number : pkt->stream_index + 1;

     if (ts == AV_NOPTS_VALUE) {
         av_log(s, AV_LOG_ERROR, "Can't write packet with unknown timestamp\n");
         return AVERROR(EINVAL);
     }

     ts += mkv->tracks[pkt->stream_index].ts_offset;

     if (!s->pb->seekable) {

         if (!mkv->dyn_bc) {
             if ((ret = avio_open_dyn_buf(&mkv->dyn_bc)) < 0) {
                 av_log(s, AV_LOG_ERROR, "Failed to open dynamic buffer\n");
                 return ret;
             }
         }

         pb = mkv->dyn_bc;
     }
 

     if (mkv->cluster_pos == -1) {

         mkv->cluster_pos = avio_tell(s->pb);

         mkv->cluster     = start_ebml_master(pb, MATROSKA_ID_CLUSTER, 0);

         put_ebml_uint(pb, MATROSKA_ID_CLUSTERTIMECODE, FFMAX(0, ts));
         mkv->cluster_pts = FFMAX(0, ts);

     }
 

     relative_packet_pos = avio_tell(s->pb) - mkv->cluster.pos;
 

     if (codec->codec_type != AVMEDIA_TYPE_SUBTITLE) {

         mkv_write_block(s, pb, MATROSKA_ID_SIMPLEBLOCK, pkt, keyframe << 7);

         if (codec->codec_type == AVMEDIA_TYPE_VIDEO && keyframe || add_cue) {

             ret = mkv_add_cuepoint(mkv->cues, pkt->stream_index, dash_tracknum, ts, mkv->cluster_pos, relative_packet_pos, -1);
             if (ret < 0) return ret;
         }

 #if FF_API_ASS_SSA

     } else if (codec->codec_id == AV_CODEC_ID_SSA) {

         while (data_offset < pkt->data + pkt->size) {
             duration = mkv_write_ass_block(s, pb, pkt, &data_offset);
             ret = mkv_add_cuepoint(mkv->cues, pkt->stream_index, dash_tracknum, ts, mkv->cluster_pos, relative_packet_pos, duration);
             if (ret < 0) return ret;
             relative_packet_pos = avio_tell(s->pb) - mkv->cluster.pos;
         }

 #endif

     } else {
     if (codec->codec_id == AV_CODEC_ID_SRT) {

         duration = mkv_write_srt_blocks(s, pb, pkt);

     } else if (codec->codec_id == AV_CODEC_ID_WEBVTT) {
         duration = mkv_write_vtt_blocks(s, pb, pkt);

     } else {

         ebml_master blockgroup = start_ebml_master(pb, MATROSKA_ID_BLOCKGROUP,
                                                    mkv_blockgroup_size(pkt->size));

         /* For backward compatibility, prefer convergence_duration. */
         if (pkt->convergence_duration > 0) {
             duration = pkt->convergence_duration;
         }

         mkv_write_block(s, pb, MATROSKA_ID_BLOCK, pkt, 0);

         put_ebml_uint(pb, MATROSKA_ID_BLOCKDURATION, duration);

         end_ebml_master(pb, blockgroup);
     }

     ret = mkv_add_cuepoint(mkv->cues, pkt->stream_index, dash_tracknum, ts,
                            mkv->cluster_pos, relative_packet_pos, duration);
     if (ret < 0)
         return ret;

     }
 

     mkv->duration = FFMAX(mkv->duration, ts + duration);
     return 0;
 }
 
 static int mkv_write_packet(AVFormatContext *s, AVPacket *pkt)
 {
     MatroskaMuxContext *mkv = s->priv_data;

     int codec_type          = s->streams[pkt->stream_index]->codec->codec_type;
     int keyframe            = !!(pkt->flags & AV_PKT_FLAG_KEY);
     int cluster_size;
     int64_t cluster_time;
     AVIOContext *pb;
     int ret;

     int start_new_cluster;

 
     if (mkv->tracks[pkt->stream_index].write_dts)
         cluster_time = pkt->dts - mkv->cluster_pts;
     else
         cluster_time = pkt->pts - mkv->cluster_pts;

     cluster_time += mkv->tracks[pkt->stream_index].ts_offset;

 
     // start a new cluster every 5 MB or 5 sec, or 32k / 1 sec for streaming or
     // after 4k and on a keyframe

     if (s->pb->seekable) {
         pb = s->pb;
         cluster_size = avio_tell(pb) - mkv->cluster_pos;
     } else {
         pb = mkv->dyn_bc;
         cluster_size = avio_tell(pb);
     }
 

     if (mkv->is_dash && codec_type == AVMEDIA_TYPE_VIDEO) {
         // WebM DASH specification states that the first block of every cluster
         // has to be a key frame. So for DASH video, we only create a cluster
         // on seeing key frames.
         start_new_cluster = keyframe;
     } else if (mkv->is_dash && codec_type == AVMEDIA_TYPE_AUDIO &&
                cluster_time > mkv->cluster_time_limit) {
         // For DASH audio, we create a Cluster based on cluster_time_limit
         start_new_cluster = 1;
     } else if (!mkv->is_dash &&
                (cluster_size > mkv->cluster_size_limit ||
                 cluster_time > mkv->cluster_time_limit ||
                 (codec_type == AVMEDIA_TYPE_VIDEO && keyframe &&
                  cluster_size > 4 * 1024))) {
         start_new_cluster = 1;
     } else {
         start_new_cluster = 0;
     }
 
     if (mkv->cluster_pos != -1 && start_new_cluster) {

         av_log(s, AV_LOG_DEBUG,
                "Starting new cluster at offset %" PRIu64 " bytes, "
                "pts %" PRIu64 "dts %" PRIu64 "\n",

                avio_tell(pb), pkt->pts, pkt->dts);

         end_ebml_master(pb, mkv->cluster);

         mkv->cluster_pos = -1;

         if (mkv->dyn_bc)
             mkv_flush_dynbuf(s);

         avio_flush(s->pb);

     }
 

     // check if we have an audio packet cached
     if (mkv->cur_audio_pkt.size > 0) {

         // for DASH audio, a CuePoint has to be added when there is a new cluster.
         ret = mkv_write_packet_internal(s, &mkv->cur_audio_pkt,
                                         mkv->is_dash ? start_new_cluster : 0);

         av_free_packet(&mkv->cur_audio_pkt);

         if (ret < 0) {

             av_log(s, AV_LOG_ERROR,
                    "Could not write cached audio packet ret:%d\n", ret);

             return ret;
         }
     }
 
     // buffer an audio packet to ensure the packet containing the video
     // keyframe's timecode is contained in the same cluster for WebM

     if (codec_type == AVMEDIA_TYPE_AUDIO) {

         mkv->cur_audio_pkt = *pkt;

         if (pkt->buf) {
             mkv->cur_audio_pkt.buf = av_buffer_ref(pkt->buf);
             ret = mkv->cur_audio_pkt.buf ? 0 : AVERROR(ENOMEM);
         } else
             ret = av_dup_packet(&mkv->cur_audio_pkt);

         if (mkv->cur_audio_pkt.side_data_elems > 0) {
             ret = av_copy_packet_side_data(&mkv->cur_audio_pkt, &mkv->cur_audio_pkt);
         }

     } else

         ret = mkv_write_packet_internal(s, pkt, 0);

     return ret;

 }
 

 static int mkv_write_flush_packet(AVFormatContext *s, AVPacket *pkt)
 {
     MatroskaMuxContext *mkv = s->priv_data;
     AVIOContext *pb;
     if (s->pb->seekable)
         pb = s->pb;
     else
         pb = mkv->dyn_bc;
     if (!pkt) {

         if (mkv->cluster_pos != -1) {

             av_log(s, AV_LOG_DEBUG,
                    "Flushing cluster at offset %" PRIu64 " bytes\n",
                    avio_tell(pb));

             end_ebml_master(pb, mkv->cluster);

             mkv->cluster_pos = -1;

             if (mkv->dyn_bc)
                 mkv_flush_dynbuf(s);
             avio_flush(s->pb);
         }
         return 0;
     }
     return mkv_write_packet(s, pkt);
 }
 

 static int mkv_write_trailer(AVFormatContext *s)
 {
     MatroskaMuxContext *mkv = s->priv_data;

     AVIOContext *pb = s->pb;

     int64_t currentpos, cuespos;

     int ret;

     // check if we have an audio packet cached
     if (mkv->cur_audio_pkt.size > 0) {

         ret = mkv_write_packet_internal(s, &mkv->cur_audio_pkt, 0);

         av_free_packet(&mkv->cur_audio_pkt);

         if (ret < 0) {

             av_log(s, AV_LOG_ERROR,
                    "Could not write cached audio packet ret:%d\n", ret);

             return ret;
         }
     }
 

     if (mkv->dyn_bc) {
         end_ebml_master(mkv->dyn_bc, mkv->cluster);
         mkv_flush_dynbuf(s);

     } else if (mkv->cluster_pos != -1) {

         end_ebml_master(pb, mkv->cluster);
     }

     if (mkv->mode != MODE_WEBM) {
         ret = mkv_write_chapters(s);

         if (ret < 0)
             return ret;

     }
 

     if (pb->seekable) {

         if (mkv->cues->num_entries) {

             if (mkv->reserve_cues_space) {
                 int64_t cues_end;
 
                 currentpos = avio_tell(pb);
                 avio_seek(pb, mkv->cues_pos, SEEK_SET);
 

                 cuespos  = mkv_write_cues(s, mkv->cues, mkv->tracks, s->nb_streams);

                 cues_end = avio_tell(pb);
                 if (cues_end > cuespos + mkv->reserve_cues_space) {

                     av_log(s, AV_LOG_ERROR,
                            "Insufficient space reserved for cues: %d "
                            "(needed: %" PRId64 ").\n",
                            mkv->reserve_cues_space, cues_end - cuespos);

                     return AVERROR(EINVAL);
                 }
 
                 if (cues_end < cuespos + mkv->reserve_cues_space)

                     put_ebml_void(pb, mkv->reserve_cues_space -
                                   (cues_end - cuespos));

 
                 avio_seek(pb, currentpos, SEEK_SET);
             } else {

                 cuespos = mkv_write_cues(s, mkv->cues, mkv->tracks, s->nb_streams);

             }

             ret = mkv_add_seekhead_entry(mkv->main_seekhead, MATROSKA_ID_CUES,
                                          cuespos);
             if (ret < 0)
                 return ret;

         }

         mkv_write_seekhead(pb, mkv->main_seekhead);
 
         // update the duration
         av_log(s, AV_LOG_DEBUG, "end duration = %" PRIu64 "\n", mkv->duration);

         currentpos = avio_tell(pb);

         avio_seek(pb, mkv->duration_offset, SEEK_SET);

         put_ebml_float(pb, MATROSKA_ID_DURATION, mkv->duration);
 

         avio_seek(pb, currentpos, SEEK_SET);

     }

     end_ebml_master(pb, mkv->segment);

     av_freep(&mkv->tracks);

     av_freep(&mkv->cues->entries);
     av_freep(&mkv->cues);

     return 0;
 }
 

 static int mkv_query_codec(enum AVCodecID codec_id, int std_compliance)

 {
     int i;

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

         if (ff_mkv_codec_tags[i].id == codec_id)
             return 1;
 

     if (std_compliance < FF_COMPLIANCE_NORMAL) {
         enum AVMediaType type = avcodec_get_type(codec_id);
         // mkv theoretically supports any video/audio through VFW/ACM

         if (type == AVMEDIA_TYPE_VIDEO || type == AVMEDIA_TYPE_AUDIO)
             return 1;
     }
 
     return 0;
 }
 

 static const AVCodecTag additional_audio_tags[] = {

     { AV_CODEC_ID_ALAC,      0XFFFFFFFF },
     { AV_CODEC_ID_EAC3,      0XFFFFFFFF },
     { AV_CODEC_ID_MLP,       0xFFFFFFFF },
     { AV_CODEC_ID_OPUS,      0xFFFFFFFF },
     { AV_CODEC_ID_PCM_S16BE, 0xFFFFFFFF },
     { AV_CODEC_ID_PCM_S24BE, 0xFFFFFFFF },
     { AV_CODEC_ID_PCM_S32BE, 0xFFFFFFFF },
     { AV_CODEC_ID_QDM2,      0xFFFFFFFF },
     { AV_CODEC_ID_RA_144,    0xFFFFFFFF },
     { AV_CODEC_ID_RA_288,    0xFFFFFFFF },
     { AV_CODEC_ID_COOK,      0xFFFFFFFF },
     { AV_CODEC_ID_TRUEHD,    0xFFFFFFFF },
     { AV_CODEC_ID_NONE,      0xFFFFFFFF }
 };
 

 static const AVCodecTag additional_video_tags[] = {

     { AV_CODEC_ID_RV10,      0xFFFFFFFF },
     { AV_CODEC_ID_RV20,      0xFFFFFFFF },
     { AV_CODEC_ID_RV30,      0xFFFFFFFF },
     { AV_CODEC_ID_RV40,      0xFFFFFFFF },
     { AV_CODEC_ID_VP9,       0xFFFFFFFF },
     { AV_CODEC_ID_NONE,      0xFFFFFFFF }
 };
 

 #define OFFSET(x) offsetof(MatroskaMuxContext, x)
 #define FLAGS AV_OPT_FLAG_ENCODING_PARAM
 static const AVOption options[] = {

     { "reserve_index_space", "Reserve a given amount of space (in bytes) at the beginning of the file for the index (cues).", OFFSET(reserve_cues_space), AV_OPT_TYPE_INT,   { .i64 = 0 },   0, INT_MAX,   FLAGS },
     { "cluster_size_limit",  "Store at most the provided amount of bytes in a cluster. ",                                     OFFSET(cluster_size_limit), AV_OPT_TYPE_INT  , { .i64 = -1 }, -1, INT_MAX,   FLAGS },
     { "cluster_time_limit",  "Store at most the provided number of milliseconds in a cluster.",                               OFFSET(cluster_time_limit), AV_OPT_TYPE_INT64, { .i64 = -1 }, -1, INT64_MAX, FLAGS },

     { "dash", "Create a WebM file conforming to WebM DASH specification", OFFSET(is_dash), AV_OPT_TYPE_INT, { .i64 = 0 }, 0, 1, FLAGS },
     { "dash_track_number", "Track number for the DASH stream", OFFSET(dash_track_number), AV_OPT_TYPE_INT, { .i64 = 1 }, 0, 127, FLAGS },

     { NULL },
 };
 

 #if CONFIG_MATROSKA_MUXER

 static const AVClass matroska_class = {
     .class_name = "matroska muxer",
     .item_name  = av_default_item_name,
     .option     = options,
     .version    = LIBAVUTIL_VERSION_INT,
 };
 

 AVOutputFormat ff_matroska_muxer = {

     .name              = "matroska",

     .long_name         = NULL_IF_CONFIG_SMALL("Matroska"),

     .mime_type         = "video/x-matroska",
     .extensions        = "mkv",
     .priv_data_size    = sizeof(MatroskaMuxContext),

     .audio_codec       = CONFIG_LIBVORBIS_ENCODER ?

                          AV_CODEC_ID_VORBIS : AV_CODEC_ID_AC3,

     .video_codec       = CONFIG_LIBX264_ENCODER ?

                          AV_CODEC_ID_H264 : AV_CODEC_ID_MPEG4,

     .write_header      = mkv_write_header,

     .write_packet      = mkv_write_flush_packet,

     .write_trailer     = mkv_write_trailer,

     .flags             = AVFMT_GLOBALHEADER | AVFMT_VARIABLE_FPS |

                          AVFMT_TS_NONSTRICT | AVFMT_ALLOW_FLUSH,

     .codec_tag         = (const AVCodecTag* const []){
          ff_codec_bmp_tags, ff_codec_wav_tags,
          additional_audio_tags, additional_video_tags, 0
     },

 #if FF_API_ASS_SSA

     .subtitle_codec    = AV_CODEC_ID_SSA,

 #else
     .subtitle_codec    = AV_CODEC_ID_ASS,
 #endif

     .query_codec       = mkv_query_codec,

     .priv_class        = &matroska_class,

 };

 #endif
 
 #if CONFIG_WEBM_MUXER

 static const AVClass webm_class = {
     .class_name = "webm muxer",
     .item_name  = av_default_item_name,
     .option     = options,
     .version    = LIBAVUTIL_VERSION_INT,
 };
 

 AVOutputFormat ff_webm_muxer = {

     .name              = "webm",

     .long_name         = NULL_IF_CONFIG_SMALL("WebM"),

     .mime_type         = "video/webm",
     .extensions        = "webm",
     .priv_data_size    = sizeof(MatroskaMuxContext),

     .audio_codec       = AV_CODEC_ID_VORBIS,
     .video_codec       = AV_CODEC_ID_VP8,

     .subtitle_codec    = AV_CODEC_ID_WEBVTT,

     .write_header      = mkv_write_header,

     .write_packet      = mkv_write_flush_packet,

     .write_trailer     = mkv_write_trailer,

     .flags             = AVFMT_GLOBALHEADER | AVFMT_VARIABLE_FPS |

                          AVFMT_TS_NONSTRICT | AVFMT_ALLOW_FLUSH,

     .priv_class        = &webm_class,

 };
 #endif

 #if CONFIG_MATROSKA_AUDIO_MUXER

 static const AVClass mka_class = {
     .class_name = "matroska audio muxer",
     .item_name  = av_default_item_name,
     .option     = options,
     .version    = LIBAVUTIL_VERSION_INT,
 };

 AVOutputFormat ff_matroska_audio_muxer = {

     .name              = "matroska",

     .long_name         = NULL_IF_CONFIG_SMALL("Matroska Audio"),

     .mime_type         = "audio/x-matroska",
     .extensions        = "mka",
     .priv_data_size    = sizeof(MatroskaMuxContext),

     .audio_codec       = CONFIG_LIBVORBIS_ENCODER ?

                          AV_CODEC_ID_VORBIS : AV_CODEC_ID_AC3,
     .video_codec       = AV_CODEC_ID_NONE,

     .write_header      = mkv_write_header,

     .write_packet      = mkv_write_flush_packet,

     .write_trailer     = mkv_write_trailer,

     .flags             = AVFMT_GLOBALHEADER | AVFMT_TS_NONSTRICT |
                          AVFMT_ALLOW_FLUSH,

     .codec_tag         = (const AVCodecTag* const []){
         ff_codec_wav_tags, additional_audio_tags, 0
     },

     .priv_class        = &mka_class,

 };

 #endif