Matroska Media Container Format Specifications
draft-ietf-cellar-matroska-07

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Last updated 2021-04-12
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cellar                                                         S. Lhomme
Internet-Draft                                                          
Intended status: Informational                                 M. Bunkus
Expires: 14 October 2021                                                
                                                                 D. Rice
                                                           12 April 2021

             Matroska Media Container Format Specifications
                     draft-ietf-cellar-matroska-07

Abstract

   This document defines the Matroska audiovisual container, including
   definitions of its structural elements, as well as its terminology,
   vocabulary, and application.

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF).  Note that other groups may also distribute
   working documents as Internet-Drafts.  The list of current Internet-
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   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on 14 October 2021.

Copyright Notice

   Copyright (c) 2021 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents (https://trustee.ietf.org/
   license-info) in effect on the date of publication of this document.
   Please review these documents carefully, as they describe your rights
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   provided without warranty as described in the Simplified BSD License.

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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   4
   2.  Status of this document . . . . . . . . . . . . . . . . . . .   5
   3.  Security Considerations . . . . . . . . . . . . . . . . . . .   5
   4.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   6
   5.  Notation and Conventions  . . . . . . . . . . . . . . . . . .   6
   6.  Basis in EBML . . . . . . . . . . . . . . . . . . . . . . . .   6
     6.1.  Added Constraints on EBML . . . . . . . . . . . . . . . .   6
     6.2.  Matroska Design . . . . . . . . . . . . . . . . . . . . .   7
       6.2.1.  Language Codes  . . . . . . . . . . . . . . . . . . .   7
       6.2.2.  Physical Types  . . . . . . . . . . . . . . . . . . .   7
       6.2.3.  Block Structure . . . . . . . . . . . . . . . . . . .   8
       6.2.4.  Lacing  . . . . . . . . . . . . . . . . . . . . . . .   9
   7.  Matroska Structure  . . . . . . . . . . . . . . . . . . . . .  14
   8.  Matroska Schema . . . . . . . . . . . . . . . . . . . . . . .  22
     8.1.  EBMLMaxIDLength Element . . . . . . . . . . . . . . . . .  22
     8.2.  EBMLMaxSizeLength Element . . . . . . . . . . . . . . . .  23
   9.  Segment Element . . . . . . . . . . . . . . . . . . . . . . .  23
     9.1.  SeekHead Element  . . . . . . . . . . . . . . . . . . . .  24
       9.1.1.  Seek Element  . . . . . . . . . . . . . . . . . . . .  24
     9.2.  Info Element  . . . . . . . . . . . . . . . . . . . . . .  25
       9.2.1.  SegmentUID Element  . . . . . . . . . . . . . . . . .  25
       9.2.2.  SegmentFilename Element . . . . . . . . . . . . . . .  26
       9.2.3.  PrevUID Element . . . . . . . . . . . . . . . . . . .  26
       9.2.4.  PrevFilename Element  . . . . . . . . . . . . . . . .  26
       9.2.5.  NextUID Element . . . . . . . . . . . . . . . . . . .  27
       9.2.6.  NextFilename Element  . . . . . . . . . . . . . . . .  27
       9.2.7.  SegmentFamily Element . . . . . . . . . . . . . . . .  28
       9.2.8.  ChapterTranslate Element  . . . . . . . . . . . . . .  28
       9.2.9.  TimestampScale Element  . . . . . . . . . . . . . . .  30
       9.2.10. Duration Element  . . . . . . . . . . . . . . . . . .  30
       9.2.11. DateUTC Element . . . . . . . . . . . . . . . . . . .  30
       9.2.12. Title Element . . . . . . . . . . . . . . . . . . . .  31
       9.2.13. MuxingApp Element . . . . . . . . . . . . . . . . . .  31
       9.2.14. WritingApp Element  . . . . . . . . . . . . . . . . .  31
     9.3.  Cluster Element . . . . . . . . . . . . . . . . . . . . .  32
       9.3.1.  Timestamp Element . . . . . . . . . . . . . . . . . .  32
       9.3.2.  SilentTracks Element  . . . . . . . . . . . . . . . .  32
       9.3.3.  Position Element  . . . . . . . . . . . . . . . . . .  33
       9.3.4.  PrevSize Element  . . . . . . . . . . . . . . . . . .  33
       9.3.5.  SimpleBlock Element . . . . . . . . . . . . . . . . .  34
       9.3.6.  BlockGroup Element  . . . . . . . . . . . . . . . . .  34
       9.3.7.  EncryptedBlock Element  . . . . . . . . . . . . . . .  43
     9.4.  Tracks Element  . . . . . . . . . . . . . . . . . . . . .  44
       9.4.1.  TrackEntry Element  . . . . . . . . . . . . . . . . .  44
     9.5.  Cues Element  . . . . . . . . . . . . . . . . . . . . . . 108
       9.5.1.  CuePoint Element  . . . . . . . . . . . . . . . . . . 109

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     9.6.  Attachments Element . . . . . . . . . . . . . . . . . . . 114
       9.6.1.  AttachedFile Element  . . . . . . . . . . . . . . . . 114
     9.7.  Chapters Element  . . . . . . . . . . . . . . . . . . . . 118
       9.7.1.  EditionEntry Element  . . . . . . . . . . . . . . . . 118
     9.8.  Tags Element  . . . . . . . . . . . . . . . . . . . . . . 127
       9.8.1.  Tag Element . . . . . . . . . . . . . . . . . . . . . 128
   10. Matroska Element Ordering . . . . . . . . . . . . . . . . . . 135
     10.1.  Top-Level Elements . . . . . . . . . . . . . . . . . . . 135
     10.2.  CRC-32 . . . . . . . . . . . . . . . . . . . . . . . . . 135
     10.3.  SeekHead . . . . . . . . . . . . . . . . . . . . . . . . 136
     10.4.  Cues (index) . . . . . . . . . . . . . . . . . . . . . . 136
     10.5.  Info . . . . . . . . . . . . . . . . . . . . . . . . . . 136
     10.6.  Chapters Element . . . . . . . . . . . . . . . . . . . . 136
     10.7.  Attachments  . . . . . . . . . . . . . . . . . . . . . . 137
     10.8.  Tags . . . . . . . . . . . . . . . . . . . . . . . . . . 137
     10.9.  Optimum layout from a muxer  . . . . . . . . . . . . . . 137
     10.10. Optimum layout after editing tags  . . . . . . . . . . . 137
     10.11. Optimum layout with Cues at the front  . . . . . . . . . 138
     10.12. Cluster Timestamp  . . . . . . . . . . . . . . . . . . . 138
   11. Chapters  . . . . . . . . . . . . . . . . . . . . . . . . . . 138
     11.1.  EditionEntry . . . . . . . . . . . . . . . . . . . . . . 139
       11.1.1.  EditionFlagDefault . . . . . . . . . . . . . . . . . 139
       11.1.2.  Default Edition  . . . . . . . . . . . . . . . . . . 139
       11.1.3.  EditionFlagOrdered . . . . . . . . . . . . . . . . . 140
       11.1.4.  ChapterSegmentUID  . . . . . . . . . . . . . . . . . 141
     11.2.  ChapterAtom  . . . . . . . . . . . . . . . . . . . . . . 142
       11.2.1.  ChapterTimeStart . . . . . . . . . . . . . . . . . . 142
       11.2.2.  ChapterTimeEnd . . . . . . . . . . . . . . . . . . . 142
       11.2.3.  ChapterFlagHidden  . . . . . . . . . . . . . . . . . 143
     11.3.  Menu features  . . . . . . . . . . . . . . . . . . . . . 143
     11.4.  Chapter Examples . . . . . . . . . . . . . . . . . . . . 144
       11.4.1.  Example 1 : basic chaptering . . . . . . . . . . . . 144
       11.4.2.  Example 2 : nested chapters  . . . . . . . . . . . . 146
   12. Attachments . . . . . . . . . . . . . . . . . . . . . . . . . 149
     12.1.  Cover Art  . . . . . . . . . . . . . . . . . . . . . . . 149
   13. Cues  . . . . . . . . . . . . . . . . . . . . . . . . . . . . 150
     13.1.  Recommendations  . . . . . . . . . . . . . . . . . . . . 150
   14. Matroska Streaming  . . . . . . . . . . . . . . . . . . . . . 151
     14.1.  File Access  . . . . . . . . . . . . . . . . . . . . . . 151
     14.2.  Livestreaming  . . . . . . . . . . . . . . . . . . . . . 152
   15. Unknown elements  . . . . . . . . . . . . . . . . . . . . . . 152
   16. Default Values  . . . . . . . . . . . . . . . . . . . . . . . 153
   17. DefaultDecodedFieldDuration . . . . . . . . . . . . . . . . . 153
   18. Encryption  . . . . . . . . . . . . . . . . . . . . . . . . . 154
   19. Image Presentation  . . . . . . . . . . . . . . . . . . . . . 154
     19.1.  Cropping . . . . . . . . . . . . . . . . . . . . . . . . 154
     19.2.  Rotation . . . . . . . . . . . . . . . . . . . . . . . . 155
   20. Matroska versioning . . . . . . . . . . . . . . . . . . . . . 155

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   21. MIME Types  . . . . . . . . . . . . . . . . . . . . . . . . . 155
   22. Segment Position  . . . . . . . . . . . . . . . . . . . . . . 156
     22.1.  Segment Position Exception . . . . . . . . . . . . . . . 156
     22.2.  Example of Segment Position  . . . . . . . . . . . . . . 156
   23. Linked Segments . . . . . . . . . . . . . . . . . . . . . . . 157
     23.1.  Hard Linking . . . . . . . . . . . . . . . . . . . . . . 157
     23.2.  Medium Linking . . . . . . . . . . . . . . . . . . . . . 159
     23.3.  Soft Linking . . . . . . . . . . . . . . . . . . . . . . 160
   24. Track Flags . . . . . . . . . . . . . . . . . . . . . . . . . 160
     24.1.  Default flag . . . . . . . . . . . . . . . . . . . . . . 160
     24.2.  Forced flag  . . . . . . . . . . . . . . . . . . . . . . 160
     24.3.  Hearing-impaired flag  . . . . . . . . . . . . . . . . . 160
     24.4.  Visual-impaired flag . . . . . . . . . . . . . . . . . . 161
     24.5.  Descriptions flag  . . . . . . . . . . . . . . . . . . . 161
     24.6.  Original flag  . . . . . . . . . . . . . . . . . . . . . 161
     24.7.  Commentary flag  . . . . . . . . . . . . . . . . . . . . 161
     24.8.  Track Operation  . . . . . . . . . . . . . . . . . . . . 161
     24.9.  Overlay Track  . . . . . . . . . . . . . . . . . . . . . 162
     24.10. Multi-planar and 3D videos . . . . . . . . . . . . . . . 162
   25. Default track selection . . . . . . . . . . . . . . . . . . . 163
     25.1.  Audio Selection  . . . . . . . . . . . . . . . . . . . . 163
     25.2.  Subtitle selection . . . . . . . . . . . . . . . . . . . 164
   26. Timestamps  . . . . . . . . . . . . . . . . . . . . . . . . . 166
     26.1.  Timestamp Types  . . . . . . . . . . . . . . . . . . . . 166
     26.2.  Block Timestamps . . . . . . . . . . . . . . . . . . . . 166
     26.3.  Raw Timestamp  . . . . . . . . . . . . . . . . . . . . . 167
     26.4.  TimestampScale . . . . . . . . . . . . . . . . . . . . . 167
     26.5.  TimestampScale Rounding  . . . . . . . . . . . . . . . . 167
     26.6.  TrackTimestampScale  . . . . . . . . . . . . . . . . . . 169
   27. Normative References  . . . . . . . . . . . . . . . . . . . . 171
   28. Informative References  . . . . . . . . . . . . . . . . . . . 172
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . . 172

1.  Introduction

   Matroska aims to become THE standard of multimedia container formats.
   It was derived from a project called [MCF], but differentiates from
   it significantly because it is based on EBML (Extensible Binary Meta
   Language) [RFC8794], a binary derivative of XML.  EBML enables
   significant advantages in terms of future format extensibility,
   without breaking file support in old parsers.

   First, it is essential to clarify exactly "What an Audio/Video
   container is", to avoid any misunderstandings:

   *  It is NOT a video or audio compression format (codec)

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   *  It is an envelope for which there can be many audio, video, and
      subtitles streams, allowing the user to store a complete movie or
      CD in a single file.

   Matroska is designed with the future in mind.  It incorporates
   features like:

   *  Fast seeking in the file

   *  Chapter entries

   *  Full metadata (tags) support

   *  Selectable subtitle/audio/video streams

   *  Modularly expandable

   *  Error resilience (can recover playback even when the stream is
      damaged)

   *  Streamable over the internet and local networks (HTTP, CIFS, FTP,
      etc)

   *  Menus (like DVDs have)

   Matroska is an open standards project.  This means for personal use
   it is absolutely free to use and that the technical specifications
   describing the bitstream are open to everybody, even to companies
   that would like to support it in their products.

2.  Status of this document

   This document is a work-in-progress specification defining the
   Matroska file format as part of the IETF Cellar working group
   (https://datatracker.ietf.org/wg/cellar/charter/).  But since it's
   quite complete it is used as a reference for the development of
   libmatroska.

   Note that versions 1, 2, and 3 have been finalized.  Version 4 is
   currently work in progress.  There MAY be further additions to v4.

3.  Security Considerations

   Matroska inherits security considerations from EBML.

   Attacks on a "Matroska Reader" could include:

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   *  Storage of a arbitrary and potentially executable data within an
      "Attachment Element".  "Matroska Readers" that extract or use data
      from Matroska Attachments SHOULD check that the data adheres to
      expectations.

   *  A "Matroska Attachment" with an inaccurate mime-type.

4.  IANA Considerations

   To be determined.

5.  Notation and Conventions

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
   "OPTIONAL" in this document are to be interpreted as described in BCP
   14 [RFC2119] [RFC8174] when, and only when, they appear in all
   capitals, as shown here.

   This document defines specific terms in order to define the format
   and application of "Matroska".  Specific terms are defined below:

   "Matroska":  A multimedia container format based on EBML (Extensible
      Binary Meta Language).

   "Matroska Reader":  A data parser that interprets the semantics of a
      Matroska document and creates a way for programs to use
      "Matroska".

   "Matroska Player":  A "Matroska Reader" with a primary purpose of
      playing audiovisual files, including "Matroska" documents.

6.  Basis in EBML

   Matroska is a Document Type of EBML (Extensible Binary Meta
   Language).  This specification is dependent on the EBML Specification
   [RFC8794].  For an understanding of Matroska's EBML Schema, see in
   particular the sections of the EBML Specification covering EBML
   Element Types (Section 7), EBML Schema (Section 11.1), and EBML
   Structure (Section 3).

6.1.  Added Constraints on EBML

   As an EBML Document Type, Matroska adds the following constraints to
   the EBML specification.

   *  The "docType" of the "EBML Header" MUST be "matroska".

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   *  The "EBMLMaxIDLength" of the "EBML Header" MUST be "4".

   *  The "EBMLMaxSizeLength" of the "EBML Header" MUST be between "1"
      and "8" inclusive.

6.2.  Matroska Design

   All top-levels elements (Segment and direct sub-elements) are coded
   on 4 octets -- i.e. class D elements.

6.2.1.  Language Codes

   Matroska from version 1 through 3 uses language codes that can be
   either the 3 letters bibliographic ISO-639-2 form [ISO639-2] (like
   "fre" for french), or such a language code followed by a dash and a
   country code for specialities in languages (like "fre-ca" for
   Canadian French).  The "ISO 639-2 Language Elements" are "Language
   Element", "TagLanguage Element", and "ChapLanguage Element".

   Starting in Matroska version 4, either [ISO639-2] or [BCP47] MAY be
   used, although "BCP 47" is RECOMMENDED.  The "BCP 47 Language
   Elements" are "LanguageIETF Element", "TagLanguageIETF Element", and
   "ChapLanguageIETF Element".  If a "BCP 47 Language Element" and an
   "ISO 639-2 Language Element" are used within the same "Parent
   Element", then the "ISO 639-2 Language Element" MUST be ignored and
   precedence given to the "BCP 47 Language Element".

   Country codes are the same 2 octets country-codes as in Internet
   domains [IANADomains] based on [ISO3166-1] alpha-2 codes.

6.2.2.  Physical Types

   Each level can have different meanings for audio and video.  The
   ORIGINAL_MEDIUM tag can be used to specify a string for
   ChapterPhysicalEquiv = 60.  Here is the list of possible levels for
   both audio and video:

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    +======================+============+===========+=================+
    | ChapterPhysicalEquiv | Audio      | Video     | Comment         |
    +======================+============+===========+=================+
    | 70                   | SET /      | SET /     | the collection  |
    |                      | PACKAGE    | PACKAGE   | of different    |
    |                      |            |           | media           |
    +----------------------+------------+-----------+-----------------+
    | 60                   | CD / 12" / | DVD / VHS | the physical    |
    |                      | 10" / 7" / | /         | medium like a   |
    |                      | TAPE /     | LASERDISC | CD or a DVD     |
    |                      | MINIDISC / |           |                 |
    |                      | DAT        |           |                 |
    +----------------------+------------+-----------+-----------------+
    | 50                   | SIDE       | SIDE      | when the        |
    |                      |            |           | original medium |
    |                      |            |           | (LP/DVD) has    |
    |                      |            |           | different sides |
    +----------------------+------------+-----------+-----------------+
    | 40                   | -          | LAYER     | another         |
    |                      |            |           | physical level  |
    |                      |            |           | on DVDs         |
    +----------------------+------------+-----------+-----------------+
    | 30                   | SESSION    | SESSION   | as found on CDs |
    |                      |            |           | and DVDs        |
    +----------------------+------------+-----------+-----------------+
    | 20                   | TRACK      | -         | as found on     |
    |                      |            |           | audio CDs       |
    +----------------------+------------+-----------+-----------------+
    | 10                   | INDEX      | -         | the first       |
    |                      |            |           | logical level   |
    |                      |            |           | of the side/    |
    |                      |            |           | medium          |
    +----------------------+------------+-----------+-----------------+

                                  Table 1

6.2.3.  Block Structure

   Bit 0 is the most significant bit.

   Frames using references SHOULD be stored in "coding order".  That
   means the references first, and then the frames referencing them.  A
   consequence is that timestamps might not be consecutive.  But a frame
   with a past timestamp MUST reference a frame already known, otherwise
   it's considered bad/void.

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6.2.3.1.  Block Header

     +========+========+=============================================+
     | Offset | Player | Description                                 |
     +========+========+=============================================+
     | 0x00+  | MUST   | Track Number (Track Entry).  It is coded in |
     |        |        | EBML like form (1 octet if the value is <   |
     |        |        | 0x80, 2 if < 0x4000, etc) (most significant |
     |        |        | bits set to increase the range).            |
     +--------+--------+---------------------------------------------+
     | 0x01+  | MUST   | Timestamp (relative to Cluster timestamp,   |
     |        |        | signed int16)                               |
     +--------+--------+---------------------------------------------+

                                  Table 2

6.2.3.2.  Block Header Flags

      +========+=====+========+====================================+
      | Offset | Bit | Player | Description                        |
      +========+=====+========+====================================+
      | 0x03+  | 0-3 | -      | Reserved, set to 0                 |
      +--------+-----+--------+------------------------------------+
      | 0x03+  | 4   | -      | Invisible, the codec SHOULD decode |
      |        |     |        | this frame but not display it      |
      +--------+-----+--------+------------------------------------+
      | 0x03+  | 5-6 | MUST   | Lacing                             |
      +--------+-----+--------+------------------------------------+
      |        |     |        | * 00 : no lacing                   |
      +--------+-----+--------+------------------------------------+
      |        |     |        | * 01 : Xiph lacing                 |
      +--------+-----+--------+------------------------------------+
      |        |     |        | * 11 : EBML lacing                 |
      +--------+-----+--------+------------------------------------+
      |        |     |        | * 10 : fixed-size lacing           |
      +--------+-----+--------+------------------------------------+
      | 0x03+  | 7   | -      | not used                           |
      +--------+-----+--------+------------------------------------+

                                 Table 3

6.2.4.  Lacing

   Lacing is a mechanism to save space when storing data.  It is
   typically used for small blocks of data (referred to as frames in
   Matroska).  There are 3 types of lacing:

   1.  Xiph, inspired by what is found in the Ogg container

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   2.  EBML, which is the same with sizes coded differently

   3.  fixed-size, where the size is not coded

   For example, a user wants to store 3 frames of the same track.  The
   first frame is 800 octets long, the second is 500 octets long and the
   third is 1000 octets long.  As these data are small, they can be
   stored in a lace to save space.  They will then be stored in the same
   block as follows:

6.2.4.1.  Xiph lacing

   *  Block head (with lacing bits set to 01)

   *  Lacing head: Number of frames in the lace -1 -- i.e. 2 (the 800
      and 500 octets one)

   *  Lacing sizes: only the 2 first ones will be coded, 800 gives
      255;255;255;35, 500 gives 255;245.  The size of the last frame is
      deduced from the total size of the Block.

   *  Data in frame 1

   *  Data in frame 2

   *  Data in frame 3

   A frame with a size multiple of 255 is coded with a 0 at the end of
   the size -- for example, 765 is coded 255;255;255;0.

6.2.4.2.  EBML lacing

   In this case, the size is not coded as blocks of 255 bytes, but as a
   difference with the previous size and this size is coded as in EBML.
   The first size in the lace is unsigned as in EBML.  The others use a
   range shifting to get a sign on each value:

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        +==========================+=============================+
        | Bit Representation       | Value                       |
        +==========================+=============================+
        | 1xxx xxxx                | value -(2^(6)-1) to 2^(6)-1 |
        |                          | (ie 0 to 2^(7)-2 minus      |
        |                          | 2^(6)-1, half of the range) |
        +--------------------------+-----------------------------+
        | 01xx xxxx xxxx xxxx      | value -(2^(13)-1) to        |
        |                          | 2^(13)-1                    |
        +--------------------------+-----------------------------+
        | 001x xxxx xxxx xxxx xxxx | value -(2^(20)-1) to        |
        | xxxx                     | 2^(20)-1                    |
        +--------------------------+-----------------------------+
        | 0001 xxxx xxxx xxxx xxxx | value -(2^(27)-1) to        |
        | xxxx xxxx xxxx           | 2^(27)-1                    |
        +--------------------------+-----------------------------+
        | 0000 1xxx xxxx xxxx xxxx | value -(2^(34)-1) to        |
        | xxxx xxxx xxxx xxxx xxxx | 2^(34)-1                    |
        +--------------------------+-----------------------------+
        | 0000 01xx xxxx xxxx xxxx | value -(2^(41)-1) to        |
        | xxxx xxxx xxxx xxxx xxxx | 2^(41)-1                    |
        | xxxx xxxx                |                             |
        +--------------------------+-----------------------------+
        | 0000 001x xxxx xxxx xxxx | value -(2^(48)-1) to        |
        | xxxx xxxx xxxx xxxx xxxx | 2^(48)-1                    |
        | xxxx xxxx xxxx xxxx      |                             |
        +--------------------------+-----------------------------+

                                 Table 4

   *  Block head (with lacing bits set to 11)

   *  Lacing head: Number of frames in the lace -1 -- i.e. 2 (the 800
      and 500 octets one)

   *  Lacing sizes: only the 2 first ones will be coded, 800 gives 0x320
      0x4000 = 0x4320, 500 is coded as -300 : - 0x12C + 0x1FFF + 0x4000
      = 0x5ED3.  The size of the last frame is deduced from the total
      size of the Block.

   *  Data in frame 1

   *  Data in frame 2

   *  Data in frame 3

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6.2.4.3.  Fixed-size lacing

   In this case, only the number of frames in the lace is saved, the
   size of each frame is deduced from the total size of the Block.  For
   example, for 3 frames of 800 octets each:

   *  Block head (with lacing bits set to 10)

   *  Lacing head: Number of frames in the lace -1 -- i.e. 2

   *  Data in frame 1

   *  Data in frame 2

   *  Data in frame 3

6.2.4.4.  SimpleBlock Structure

   The "SimpleBlock" is inspired by the Block structure; see
   Section 6.2.3.  The main differences are the added Keyframe flag and
   Discardable flag.  Otherwise everything is the same.

   Bit 0 is the most significant bit.

   Frames using references SHOULD be stored in "coding order".  That
   means the references first, and then the frames referencing them.  A
   consequence is that timestamps might not be consecutive.  But a frame
   with a past timestamp MUST reference a frame already known, otherwise
   it's considered bad/void.

6.2.4.4.1.  SimpleBlock Header

     +========+========+=============================================+
     | Offset | Player | Description                                 |
     +========+========+=============================================+
     | 0x00+  | MUST   | Track Number (Track Entry).  It is coded in |
     |        |        | EBML like form (1 octet if the value is <   |
     |        |        | 0x80, 2 if < 0x4000, etc) (most significant |
     |        |        | bits set to increase the range).            |
     +--------+--------+---------------------------------------------+
     | 0x01+  | MUST   | Timestamp (relative to Cluster timestamp,   |
     |        |        | signed int16)                               |
     +--------+--------+---------------------------------------------+

                                  Table 5

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6.2.4.4.2.  SimpleBlock Header Flags

   +========+=====+========+==========================================+
   | Offset | Bit | Player | Description                              |
   +========+=====+========+==========================================+
   | 0x03+  | 0   | -      | Keyframe, set when the Block contains    |
   |        |     |        | only keyframes                           |
   +--------+-----+--------+------------------------------------------+
   | 0x03+  | 1-3 | -      | Reserved, set to 0                       |
   +--------+-----+--------+------------------------------------------+
   | 0x03+  | 4   | -      | Invisible, the codec SHOULD decode this  |
   |        |     |        | frame but not display it                 |
   +--------+-----+--------+------------------------------------------+
   | 0x03+  | 5-6 | MUST   | Lacing                                   |
   +--------+-----+--------+------------------------------------------+
   |        |     |        | * 00 : no lacing                         |
   +--------+-----+--------+------------------------------------------+
   |        |     |        | * 01 : Xiph lacing                       |
   +--------+-----+--------+------------------------------------------+
   |        |     |        | * 11 : EBML lacing                       |
   +--------+-----+--------+------------------------------------------+
   |        |     |        | * 10 : fixed-size lacing                 |
   +--------+-----+--------+------------------------------------------+
   | 0x03+  | 7   | -      | Discardable, the frames of the Block can |
   |        |     |        | be discarded during playing if needed    |
   +--------+-----+--------+------------------------------------------+

                                 Table 6

6.2.4.5.  Laced Data

   When lacing bit is set.

     +========+========+=============================================+
     | Offset | Player | Description                                 |
     +========+========+=============================================+
     | 0x00   | MUST   | Number of frames in the lace-1 (uint8)      |
     +--------+--------+---------------------------------------------+
     | 0x01 / | MUST*  | Lace-coded size of each frame of the lace,  |
     | 0xXX   |        | except for the last one (multiple uint8).   |
     |        |        | *This is not used with Fixed-size lacing as |
     |        |        | it is calculated automatically from (total  |
     |        |        | size of lace) / (number of frames in lace). |
     +--------+--------+---------------------------------------------+

                                  Table 7

   For (possibly) Laced Data

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              +========+========+==========================+
              | Offset | Player | Description              |
              +========+========+==========================+
              | 0x00   | MUST   | Consecutive laced frames |
              +--------+--------+--------------------------+

                                 Table 8

7.  Matroska Structure

   A Matroska file MUST be composed of at least one "EBML Document"
   using the "Matroska Document Type".  Each "EBML Document" MUST start
   with an "EBML Header" and MUST be followed by the "EBML Root
   Element", defined as "Segment" in Matroska.  Matroska defines several
   "Top Level Elements" which MAY occur within the "Segment".

   As an example, a simple Matroska file consisting of a single "EBML
   Document" could be represented like this:

   *  "EBML Header"

   *  "Segment"

   A more complex Matroska file consisting of an "EBML Stream"
   (consisting of two "EBML Documents") could be represented like this:

   *  "EBML Header"

   *  "Segment"

   *  "EBML Header"

   *  "Segment"

   The following diagram represents a simple Matroska file, comprised of
   an "EBML Document" with an "EBML Header", a "Segment Element" (the
   "Root Element"), and all eight Matroska "Top Level Elements".  In the
   following diagrams of this section, horizontal spacing expresses a
   parent-child relationship between Matroska Elements (e.g., the "Info
   Element" is contained within the "Segment Element") whereas vertical
   alignment represents the storage order within the file.

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   +-------------+
   | EBML Header |
   +---------------------------+
   | Segment     | SeekHead    |
   |             |-------------|
   |             | Info        |
   |             |-------------|
   |             | Tracks      |
   |             |-------------|
   |             | Chapters    |
   |             |-------------|
   |             | Cluster     |
   |             |-------------|
   |             | Cues        |
   |             |-------------|
   |             | Attachments |
   |             |-------------|
   |             | Tags        |
   +---------------------------+

   The Matroska "EBML Schema" defines eight "Top Level Elements":
   "SeekHead", "Info", "Tracks", "Chapters", "Cluster", "Cues",
   "Attachments", and "Tags".

   The "SeekHead Element" (also known as "MetaSeek") contains an index
   of "Top Level Elements" locations within the "Segment".  Use of the
   "SeekHead Element" is RECOMMENDED.  Without a "SeekHead Element", a
   Matroska parser would have to search the entire file to find all of
   the other "Top Level Elements".  This is due to Matroska's flexible
   ordering requirements; for instance, it is acceptable for the
   "Chapters Element" to be stored after the "Cluster Elements".

   +--------------------------------+
   | SeekHead | Seek | SeekID       |
   |          |      |--------------|
   |          |      | SeekPosition |
   +--------------------------------+

             Figure 1: Representation of a "SeekHead Element".

   The "Info Element" contains vital information for identifying the
   whole "Segment".  This includes the title for the "Segment", a
   randomly generated unique identifier, and the unique identifier(s) of
   any linked "Segment Elements".

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   +-------------------------+
   | Info | SegmentUID       |
   |      |------------------|
   |      | SegmentFilename  |
   |      |------------------|
   |      | PrevUID          |
   |      |------------------|
   |      | PrevFilename     |
   |      |------------------|
   |      | NextUID          |
   |      |------------------|
   |      | NextFilename     |
   |      |------------------|
   |      | SegmentFamily    |
   |      |------------------|
   |      | ChapterTranslate |
   |      |------------------|
   |      | TimestampScale   |
   |      |------------------|
   |      | Duration         |
   |      |------------------|
   |      | DateUTC          |
   |      |------------------|
   |      | Title            |
   |      |------------------|
   |      | MuxingApp        |
   |      |------------------|
   |      | WritingApp       |
   |-------------------------|

        Figure 2: Representation of an "Info Element" and its "Child
                                 Elements".

   The "Tracks Element" defines the technical details for each track and
   can store the name, number, unique identifier, language, and type
   (audio, video, subtitles, etc.) of each track.  For example, the
   "Tracks Element" MAY store information about the resolution of a
   video track or sample rate of an audio track.

   The "Tracks Element" MUST identify all the data needed by the codec
   to decode the data of the specified track.  However, the data
   required is contingent on the codec used for the track.  For example,
   a "Track Element" for uncompressed audio only requires the audio bit
   rate to be present.  A codec such as AC-3 would require that the
   "CodecID Element" be present for all tracks, as it is the primary way
   to identify which codec to use to decode the track.

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   +------------------------------------+
   | Tracks | TrackEntry | TrackNumber  |
   |        |            |--------------|
   |        |            | TrackUID     |
   |        |            |--------------|
   |        |            | TrackType    |
   |        |            |--------------|
   |        |            | Name         |
   |        |            |--------------|
   |        |            | Language     |
   |        |            |--------------|
   |        |            | CodecID      |
   |        |            |--------------|
   |        |            | CodecPrivate |
   |        |            |--------------|
   |        |            | CodecName    |
   |        |            |----------------------------------+
   |        |            | Video        | FlagInterlaced    |
   |        |            |              |-------------------|
   |        |            |              | FieldOrder        |
   |        |            |              |-------------------|
   |        |            |              | StereoMode        |
   |        |            |              |-------------------|
   |        |            |              | AlphaMode         |
   |        |            |              |-------------------|
   |        |            |              | PixelWidth        |
   |        |            |              |-------------------|
   |        |            |              | PixelHeight       |
   |        |            |              |-------------------|
   |        |            |              | DisplayWidth      |
   |        |            |              |-------------------|
   |        |            |              | DisplayHeight     |
   |        |            |              |-------------------|
   |        |            |              | AspectRatioType   |
   |        |            |              |-------------------|
   |        |            |              | Color             |
   |        |            |----------------------------------|
   |        |            | Audio        | SamplingFrequency |
   |        |            |              |-------------------|
   |        |            |              | Channels          |
   |        |            |              |-------------------|
   |        |            |              | BitDepth          |
   |--------------------------------------------------------|

      Figure 3: Representation of the "Tracks Element" and a selection
                       of its "Descendant Elements".

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   The "Chapters Element" lists all of the chapters.  Chapters are a way
   to set predefined points to jump to in video or audio.

   +-----------------------------------------+
   | Chapters | Edition | EditionUID         |
   |          | Entry   |--------------------|
   |          |         | EditionFlagDefault |
   |          |         |--------------------|
   |          |         | EditionFlagOrdered |
   |          |         |---------------------------------+
   |          |         | ChapterAtom | ChapterUID        |
   |          |         |             |-------------------|
   |          |         |             | ChapterStringUID  |
   |          |         |             |-------------------|
   |          |         |             | ChapterTimeStart  |
   |          |         |             |-------------------|
   |          |         |             | ChapterTimeEnd    |
   |          |         |             |-------------------|
   |          |         |             | ChapterFlagHidden |
   |          |         |             |-------------------------------+
   |          |         |             | ChapterDisplay | ChapString   |
   |          |         |             |                |--------------|
   |          |         |             |                | ChapLanguage |
   +------------------------------------------------------------------+

          Figure 4: Representation of the "Chapters Element" and a
                  selection of its "Descendant Elements".

   "Cluster Elements" contain the content for each track, e.g., video
   frames.  A Matroska file SHOULD contain at least one "Cluster
   Element".  The "Cluster Element" helps to break up "SimpleBlock" or
   "BlockGroup Elements" and helps with seeking and error protection.
   It is RECOMMENDED that the size of each individual "Cluster Element"
   be limited to store no more than 5 seconds or 5 megabytes.  Every
   "Cluster Element" MUST contain a "Timestamp Element".  This SHOULD be
   the "Timestamp Element" used to play the first "Block" in the
   "Cluster Element".  There SHOULD be one or more "BlockGroup" or
   "SimpleBlock Element" in each "Cluster Element".  A "BlockGroup
   Element" MAY contain a "Block" of data and any information relating
   directly to that "Block".

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   +--------------------------+
   | Cluster | Timestamp      |
   |         |----------------|
   |         | SilentTracks   |
   |         |----------------|
   |         | Position       |
   |         |----------------|
   |         | PrevSize       |
   |         |----------------|
   |         | SimpleBlock    |
   |         |----------------|
   |         | BlockGroup     |
   |         |----------------|
   |         | EncryptedBlock |
   +--------------------------+

     Figure 5: Representation of a "Cluster Element" and its immediate
                             "Child Elements".

   +----------------------------------+
   | Block | Portion of | Data Type   |
   |       | a Block    |  - Bit Flag |
   |       |--------------------------+
   |       | Header     | TrackNumber |
   |       |            |-------------|
   |       |            | Timestamp   |
   |       |            |-------------|
   |       |            | Flags       |
   |       |            |  - Gap      |
   |       |            |  - Lacing   |
   |       |            |  - Reserved |
   |       |--------------------------|
   |       | Optional   | FrameSize   |
   |       |--------------------------|
   |       | Data       | Frame       |
   +----------------------------------+

         Figure 6: Representation of the "Block Element" structure.

   Each "Cluster" MUST contain exactly one "Timestamp Element".  The
   "Timestamp Element" value MUST be stored once per "Cluster".  The
   "Timestamp Element" in the "Cluster" is relative to the entire
   "Segment".  The "Timestamp Element" SHOULD be the first "Element" in
   the "Cluster".

   Additionally, the "Block" contains an offset that, when added to the
   "Cluster"'s "Timestamp Element" value, yields the "Block"'s effective
   timestamp.  Therefore, timestamp in the "Block" itself is relative to

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   the "Timestamp Element" in the "Cluster".  For example, if the
   "Timestamp Element" in the "Cluster" is set to 10 seconds and a
   "Block" in that "Cluster" is supposed to be played 12 seconds into
   the clip, the timestamp in the "Block" would be set to 2 seconds.

   The "ReferenceBlock" in the "BlockGroup" is used instead of the basic
   "P-frame"/"B-frame" description.  Instead of simply saying that this
   "Block" depends on the "Block" directly before, or directly
   afterwards, the "Timestamp" of the necessary "Block" is used.
   Because there can be as many "ReferenceBlock Elements" as necessary
   for a "Block", it allows for some extremely complex referencing.

   The "Cues Element" is used to seek when playing back a file by
   providing a temporal index for some of the "Tracks".  It is similar
   to the "SeekHead Element", but used for seeking to a specific time
   when playing back the file.  It is possible to seek without this
   element, but it is much more difficult because a "Matroska Reader"
   would have to 'hunt and peck' through the file looking for the
   correct timestamp.

   The "Cues Element" SHOULD contain at least one "CuePoint Element".
   Each "CuePoint Element" stores the position of the "Cluster" that
   contains the "BlockGroup" or "SimpleBlock Element".  The timestamp is
   stored in the "CueTime Element" and location is stored in the
   "CueTrackPositions Element".

   The "Cues Element" is flexible.  For instance, "Cues Element" can be
   used to index every single timestamp of every "Block" or they can be
   indexed selectively.  For video files, it is RECOMMENDED to index at
   least the keyframes of the video track.

   +-------------------------------------+
   | Cues | CuePoint | CueTime           |
   |      |          |-------------------|
   |      |          | CueTrackPositions |
   |      |------------------------------|
   |      | CuePoint | CueTime           |
   |      |          |-------------------|
   |      |          | CueTrackPositions |
   +-------------------------------------+

       Figure 7: Representation of a "Cues Element" and two levels of
                         its "Descendant Elements".

   The "Attachments Element" is for attaching files to a Matroska file
   such as pictures, webpages, programs, or even the codec needed to
   play back the file.

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   +------------------------------------------------+
   | Attachments | AttachedFile | FileDescription   |
   |             |              |-------------------|
   |             |              | FileName          |
   |             |              |-------------------|
   |             |              | FileMimeType      |
   |             |              |-------------------|
   |             |              | FileData          |
   |             |              |-------------------|
   |             |              | FileUID           |
   |             |              |-------------------|
   |             |              | FileName          |
   |             |              |-------------------|
   |             |              | FileReferral      |
   |             |              |-------------------|
   |             |              | FileUsedStartTime |
   |             |              |-------------------|
   |             |              | FileUsedEndTime   |
   +------------------------------------------------+

            Figure 8: Representation of a "Attachments Element".

   The "Tags Element" contains metadata that describes the "Segment" and
   potentially its "Tracks", "Chapters", and "Attachments".  Each
   "Track" or "Chapter" that those tags applies to has its UID listed in
   the "Tags".  The "Tags" contain all extra information about the file:
   scriptwriter, singer, actors, directors, titles, edition, price,
   dates, genre, comments, etc.  Tags can contain their values in
   multiple languages.  For example, a movie's "title" "Tag" might
   contain both the original English title as well as the title it was
   released as in Germany.

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   +-------------------------------------------+
   | Tags | Tag | Targets   | TargetTypeValue  |
   |      |     |           |------------------|
   |      |     |           | TargetType       |
   |      |     |           |------------------|
   |      |     |           | TagTrackUID      |
   |      |     |           |------------------|
   |      |     |           | TagEditionUID    |
   |      |     |           |------------------|
   |      |     |           | TagChapterUID    |
   |      |     |           |------------------|
   |      |     |           | TagAttachmentUID |
   |      |     |------------------------------|
   |      |     | SimpleTag | TagName          |
   |      |     |           |------------------|
   |      |     |           | TagLanguage      |
   |      |     |           |------------------|
   |      |     |           | TagDefault       |
   |      |     |           |------------------|
   |      |     |           | TagString        |
   |      |     |           |------------------|
   |      |     |           | TagBinary        |
   |      |     |           |------------------|
   |      |     |           | SimpleTag        |
   +-------------------------------------------+

      Figure 9: Representation of a "Tags Element" and three levels of
                          its "Children Elements".

8.  Matroska Schema

   This specification includes an "EBML Schema", which defines the
   Elements and structure of Matroska as an EBML Document Type.  The
   EBML Schema defines every valid Matroska element in a manner defined
   by the EBML specification.

   Here the definition of each Matroska Element is provided.

8.1.  EBMLMaxIDLength Element

   name:  EBMLMaxIDLength

   path:  "\EBML\EBMLMaxIDLength"

   id:  0x42F2

   minOccurs:  1

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   maxOccurs:  1

   range:  4

   default:  4

   type:  uinteger

8.2.  EBMLMaxSizeLength Element

   name:  EBMLMaxSizeLength

   path:  "\EBML\EBMLMaxSizeLength"

   id:  0x42F3

   minOccurs:  1

   maxOccurs:  1

   range:  1-8

   default:  8

   type:  uinteger

9.  Segment Element

   name:  Segment

   path:  "\Segment"

   id:  0x18538067

   minOccurs:  1

   maxOccurs:  1

   type:  master

   unknownsizeallowed:  1

   definition:  The Root Element that contains all other Top-Level
      Elements (Elements defined only at Level 1).  A Matroska file is
      composed of 1 Segment.

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9.1.  SeekHead Element

   name:  SeekHead

   path:  "\Segment\SeekHead"

   id:  0x114D9B74

   maxOccurs:  2

   type:  master

   definition:  Contains the Segment Position of other Top-Level
      Elements.

9.1.1.  Seek Element

   name:  Seek

   path:  "\Segment\SeekHead\Seek"

   id:  0x4DBB

   minOccurs:  1

   type:  master

   definition:  Contains a single seek entry to an EBML Element.

9.1.1.1.  SeekID Element

   name:  SeekID

   path:  "\Segment\SeekHead\Seek\SeekID"

   id:  0x53AB

   minOccurs:  1

   maxOccurs:  1

   type:  binary

   definition:  The binary ID corresponding to the Element name.

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9.1.1.2.  SeekPosition Element

   name:  SeekPosition

   path:  "\Segment\SeekHead\Seek\SeekPosition"

   id:  0x53AC

   minOccurs:  1

   maxOccurs:  1

   type:  uinteger

   definition:  The Segment Position of the Element.

9.2.  Info Element

   name:  Info

   path:  "\Segment\Info"

   id:  0x1549A966

   minOccurs:  1

   maxOccurs:  1

   type:  master

   recurring:  1

   definition:  Contains general information about the Segment.

9.2.1.  SegmentUID Element

   name:  SegmentUID

   path:  "\Segment\Info\SegmentUID"

   id:  0x73A4

   maxOccurs:  1

   range:  not 0

   type:  binary

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   definition:  A randomly generated unique ID to identify the Segment
      amongst many others (128 bits).

   usage notes:  If the Segment is a part of a Linked Segment, then this
      Element is REQUIRED.

9.2.2.  SegmentFilename Element

   name:  SegmentFilename

   path:  "\Segment\Info\SegmentFilename"

   id:  0x7384

   maxOccurs:  1

   type:  utf-8

   definition:  A filename corresponding to this Segment.

9.2.3.  PrevUID Element

   name:  PrevUID

   path:  "\Segment\Info\PrevUID"

   id:  0x3CB923

   maxOccurs:  1

   type:  binary

   definition:  A unique ID to identify the previous Segment of a Linked
      Segment (128 bits).

   usage notes:  If the Segment is a part of a Linked Segment that uses
      Hard Linking, then either the PrevUID or the NextUID Element is
      REQUIRED.  If a Segment contains a PrevUID but not a NextUID, then
      it MAY be considered as the last Segment of the Linked Segment.
      The PrevUID MUST NOT be equal to the SegmentUID.

9.2.4.  PrevFilename Element

   name:  PrevFilename

   path:  "\Segment\Info\PrevFilename"

   id:  0x3C83AB

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   maxOccurs:  1

   type:  utf-8

   definition:  A filename corresponding to the file of the previous
      Linked Segment.

   usage notes:  Provision of the previous filename is for display
      convenience, but PrevUID SHOULD be considered authoritative for
      identifying the previous Segment in a Linked Segment.

9.2.5.  NextUID Element

   name:  NextUID

   path:  "\Segment\Info\NextUID"

   id:  0x3EB923

   maxOccurs:  1

   type:  binary

   definition:  A unique ID to identify the next Segment of a Linked
      Segment (128 bits).

   usage notes:  If the Segment is a part of a Linked Segment that uses
      Hard Linking, then either the PrevUID or the NextUID Element is
      REQUIRED.  If a Segment contains a NextUID but not a PrevUID, then
      it MAY be considered as the first Segment of the Linked Segment.
      The NextUID MUST NOT be equal to the SegmentUID.

9.2.6.  NextFilename Element

   name:  NextFilename

   path:  "\Segment\Info\NextFilename"

   id:  0x3E83BB

   maxOccurs:  1

   type:  utf-8

   definition:  A filename corresponding to the file of the next Linked
      Segment.

   usage notes:  Provision of the next filename is for display

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      convenience, but NextUID SHOULD be considered authoritative for
      identifying the Next Segment.

9.2.7.  SegmentFamily Element

   name:  SegmentFamily

   path:  "\Segment\Info\SegmentFamily"

   id:  0x4444

   type:  binary

   definition:  A randomly generated unique ID that all Segments of a
      Linked Segment MUST share (128 bits).

   usage notes:  If the Segment is a part of a Linked Segment that uses
      Soft Linking, then this Element is REQUIRED.

9.2.8.  ChapterTranslate Element

   name:  ChapterTranslate

   path:  "\Segment\Info\ChapterTranslate"

   id:  0x6924

   type:  master

   definition:  A tuple of corresponding ID used by chapter codecs to
      represent this Segment.

9.2.8.1.  ChapterTranslateEditionUID Element

   name:  ChapterTranslateEditionUID

   path:  "\Segment\Info\ChapterTranslate\ChapterTranslateEditionUID"

   id:  0x69FC

   type:  uinteger

   definition:  Specify an edition UID on which this correspondence
      applies.  When not specified, it means for all editions found in
      the Segment.

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9.2.8.2.  ChapterTranslateCodec Element

   name:  ChapterTranslateCodec

   path:  "\Segment\Info\ChapterTranslate\ChapterTranslateCodec"

   id:  0x69BF

   minOccurs:  1

   maxOccurs:  1

   type:  uinteger

   definition:  The chapter codec; see Section 9.7.1.4.10.1.

   restrictions:

                        +=======+=================+
                        | value | label           |
                        +=======+=================+
                        | 0     | Matroska Script |
                        +-------+-----------------+
                        | 1     | DVD-menu        |
                        +-------+-----------------+

                                  Table 9

9.2.8.3.  ChapterTranslateID Element

   name:  ChapterTranslateID

   path:  "\Segment\Info\ChapterTranslate\ChapterTranslateID"

   id:  0x69A5

   minOccurs:  1

   maxOccurs:  1

   type:  binary

   definition:  The binary value used to represent this Segment in the
      chapter codec data.  The format depends on the ChapProcessCodecID
      used; see Section 9.7.1.4.10.1.

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9.2.9.  TimestampScale Element

   name:  TimestampScale

   path:  "\Segment\Info\TimestampScale"

   id:  0x2AD7B1

   minOccurs:  1

   maxOccurs:  1

   range:  not 0

   default:  1000000

   type:  uinteger

   definition:  Timestamp scale in nanoseconds (1.000.000 means all
      timestamps in the Segment are expressed in milliseconds).

9.2.10.  Duration Element

   name:  Duration

   path:  "\Segment\Info\Duration"

   id:  0x4489

   maxOccurs:  1

   range:  > 0x0p+0

   type:  float

   definition:  Duration of the Segment in nanoseconds based on
      TimestampScale.

9.2.11.  DateUTC Element

   name:  DateUTC

   path:  "\Segment\Info\DateUTC"

   id:  0x4461

   maxOccurs:  1

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   type:  date

   definition:  The date and time that the Segment was created by the
      muxing application or library.

9.2.12.  Title Element

   name:  Title

   path:  "\Segment\Info\Title"

   id:  0x7BA9

   maxOccurs:  1

   type:  utf-8

   definition:  General name of the Segment.

9.2.13.  MuxingApp Element

   name:  MuxingApp

   path:  "\Segment\Info\MuxingApp"

   id:  0x4D80

   minOccurs:  1

   maxOccurs:  1

   type:  utf-8

   definition:  Muxing application or library (example: "libmatroska-
      0.4.3").

   usage notes:  Include the full name of the application or library
      followed by the version number.

9.2.14.  WritingApp Element

   name:  WritingApp

   path:  "\Segment\Info\WritingApp"

   id:  0x5741

   minOccurs:  1

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   maxOccurs:  1

   type:  utf-8

   definition:  Writing application (example: "mkvmerge-0.3.3").

   usage notes:  Include the full name of the application followed by
      the version number.

9.3.  Cluster Element

   name:  Cluster

   path:  "\Segment\Cluster"

   id:  0x1F43B675

   type:  master

   unknownsizeallowed:  1

   definition:  The Top-Level Element containing the (monolithic) Block
      structure.

9.3.1.  Timestamp Element

   name:  Timestamp

   path:  "\Segment\Cluster\Timestamp"

   id:  0xE7

   minOccurs:  1

   maxOccurs:  1

   type:  uinteger

   definition:  Absolute timestamp of the cluster (based on
      TimestampScale).

9.3.2.  SilentTracks Element

   name:  SilentTracks

   path:  "\Segment\Cluster\SilentTracks"

   id:  0x5854

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   maxOccurs:  1

   type:  master

   definition:  The list of tracks that are not used in that part of the
      stream.  It is useful when using overlay tracks on seeking or to
      decide what track to use.

9.3.2.1.  SilentTrackNumber Element

   name:  SilentTrackNumber

   path:  "\Segment\Cluster\SilentTracks\SilentTrackNumber"

   id:  0x58D7

   type:  uinteger

   definition:  One of the track number that are not used from now on in
      the stream.  It could change later if not specified as silent in a
      further Cluster.

9.3.3.  Position Element

   name:  Position

   path:  "\Segment\Cluster\Position"

   id:  0xA7

   maxOccurs:  1

   type:  uinteger

   definition:  The Segment Position of the Cluster in the Segment (0 in
      live streams).  It might help to resynchronise offset on damaged
      streams.

9.3.4.  PrevSize Element

   name:  PrevSize

   path:  "\Segment\Cluster\PrevSize"

   id:  0xAB

   maxOccurs:  1

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   type:  uinteger

   definition:  Size of the previous Cluster, in octets.  Can be useful
      for backward playing.

9.3.5.  SimpleBlock Element

   name:  SimpleBlock

   path:  "\Segment\Cluster\SimpleBlock"

   id:  0xA3

   type:  binary

   minver:  2

   definition:  Similar to Block, see Section 6.2.3, but without all the
      extra information, mostly used to reduced overhead when no extra
      feature is needed; see Section 6.2.4.4 on SimpleBlock Structure.

9.3.6.  BlockGroup Element

   name:  BlockGroup

   path:  "\Segment\Cluster\BlockGroup"

   id:  0xA0

   type:  master

   definition:  Basic container of information containing a single Block
      and information specific to that Block.

9.3.6.1.  Block Element

   name:  Block

   path:  "\Segment\Cluster\BlockGroup\Block"

   id:  0xA1

   minOccurs:  1

   maxOccurs:  1

   type:  binary

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   definition:  Block containing the actual data to be rendered and a
      timestamp relative to the Cluster Timestamp; see Section 6.2.3 on
      Block Structure.

9.3.6.2.  BlockVirtual Element

   name:  BlockVirtual

   path:  "\Segment\Cluster\BlockGroup\BlockVirtual"

   id:  0xA2

   maxOccurs:  1

   type:  binary

   minver:  0

   maxver:  0

   definition:  A Block with no data.  It MUST be stored in the stream
      at the place the real Block would be in display order.

9.3.6.3.  BlockAdditions Element

   name:  BlockAdditions

   path:  "\Segment\Cluster\BlockGroup\BlockAdditions"

   id:  0x75A1

   maxOccurs:  1

   type:  master

   definition:  Contain additional blocks to complete the main one.  An
      EBML parser that has no knowledge of the Block structure could
      still see and use/skip these data.

9.3.6.3.1.  BlockMore Element

   name:  BlockMore

   path:  "\Segment\Cluster\BlockGroup\BlockAdditions\BlockMore"

   id:  0xA6

   minOccurs:  1

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   type:  master

   definition:  Contain the BlockAdditional and some parameters.

9.3.6.3.1.1.  BlockAddID Element

   name:  BlockAddID

   path:  "\Segment\Cluster\BlockGroup\BlockAdditions\BlockMore\BlockAdd
      ID"

   id:  0xEE

   minOccurs:  1

   maxOccurs:  1

   range:  not 0

   default:  1

   type:  uinteger

   definition:  An ID to identify the BlockAdditional level.  If
      BlockAddIDType of the corresponding block is 0, this value is also
      the value of BlockAddIDType for the meaning of the content of
      BlockAdditional.

9.3.6.3.1.2.  BlockAdditional Element

   name:  BlockAdditional

   path:  "\Segment\Cluster\BlockGroup\BlockAdditions\BlockMore\BlockAdd
      itional"

   id:  0xA5

   minOccurs:  1

   maxOccurs:  1

   type:  binary

   definition:  Interpreted by the codec as it wishes (using the
      BlockAddID).

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9.3.6.4.  BlockDuration Element

   name:  BlockDuration

   path:  "\Segment\Cluster\BlockGroup\BlockDuration"

   id:  0x9B

   minOccurs: see implementation notes

   maxOccurs:  1

   default: see implementation notes

   type:  uinteger

   definition:  The duration of the Block (based on TimestampScale).
      The BlockDuration Element can be useful at the end of a Track to
      define the duration of the last frame (as there is no subsequent
      Block available), or when there is a break in a track like for
      subtitle tracks.

   implementation notes:

       +==========================+===============================+
       | attribute                | note                          |
       +==========================+===============================+
       | minOccurs                | BlockDuration MUST be set     |
       |                          | (minOccurs=1) if the          |
       |                          | associated TrackEntry stores  |
       |                          | a DefaultDuration value.      |
       +--------------------------+-------------------------------+
       | default                  | When not written and with no  |
       |                          | DefaultDuration, the value is |
       |                          | assumed to be the difference  |
       |                          | between the timestamp         |
       +--------------------------+-------------------------------+
       | of this Block and the    |                               |
       | timestamp of the next    |                               |
       | Block in "display" order |                               |
       | (not coding order).      |                               |
       +--------------------------+-------------------------------+

                                 Table 10

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9.3.6.5.  ReferencePriority Element

   name:  ReferencePriority

   path:  "\Segment\Cluster\BlockGroup\ReferencePriority"

   id:  0xFA

   minOccurs:  1

   maxOccurs:  1

   default:  0

   type:  uinteger

   definition:  This frame is referenced and has the specified cache
      priority.  In cache only a frame of the same or higher priority
      can replace this frame.  A value of 0 means the frame is not
      referenced.

9.3.6.6.  ReferenceBlock Element

   name:  ReferenceBlock

   path:  "\Segment\Cluster\BlockGroup\ReferenceBlock"

   id:  0xFB

   type:  integer

   definition:  Timestamp of another frame used as a reference (ie: B or
      P frame).  The timestamp is relative to the block it's attached
      to.

9.3.6.7.  ReferenceVirtual Element

   name:  ReferenceVirtual

   path:  "\Segment\Cluster\BlockGroup\ReferenceVirtual"

   id:  0xFD

   maxOccurs:  1

   type:  integer

   minver:  0

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   maxver:  0

   definition:  The Segment Position of the data that would otherwise be
      in position of the virtual block.

9.3.6.8.  CodecState Element

   name:  CodecState

   path:  "\Segment\Cluster\BlockGroup\CodecState"

   id:  0xA4

   maxOccurs:  1

   type:  binary

   minver:  2

   definition:  The new codec state to use.  Data interpretation is
      private to the codec.  This information SHOULD always be
      referenced by a seek entry.

9.3.6.9.  DiscardPadding Element

   name:  DiscardPadding

   path:  "\Segment\Cluster\BlockGroup\DiscardPadding"

   id:  0x75A2

   maxOccurs:  1

   type:  integer

   minver:  4

   definition:  Duration in nanoseconds of the silent data added to the
      Block (padding at the end of the Block for positive value, at the
      beginning of the Block for negative value).  The duration of
      DiscardPadding is not calculated in the duration of the TrackEntry
      and SHOULD be discarded during playback.

9.3.6.10.  Slices Element

   name:  Slices

   path:  "\Segment\Cluster\BlockGroup\Slices"

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   id:  0x8E

   maxOccurs:  1

   type:  master

   definition:  Contains slices description.

9.3.6.10.1.  TimeSlice Element

   name:  TimeSlice

   path:  "\Segment\Cluster\BlockGroup\Slices\TimeSlice"

   id:  0xE8

   type:  master

   maxver:  1

   definition:  Contains extra time information about the data contained
      in the Block.  Being able to interpret this Element is not
      REQUIRED for playback.

9.3.6.10.1.1.  LaceNumber Element

   name:  LaceNumber

   path:  "\Segment\Cluster\BlockGroup\Slices\TimeSlice\LaceNumber"

   id:  0xCC

   maxOccurs:  1

   default:  0

   type:  uinteger

   maxver:  1

   definition:  The reverse number of the frame in the lace (0 is the
      last frame, 1 is the next to last, etc).  Being able to interpret
      this Element is not REQUIRED for playback.

9.3.6.10.1.2.  FrameNumber Element

   name:  FrameNumber

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   path:  "\Segment\Cluster\BlockGroup\Slices\TimeSlice\FrameNumber"

   id:  0xCD

   maxOccurs:  1

   default:  0

   type:  uinteger

   minver:  0

   maxver:  0

   definition:  The number of the frame to generate from this lace with
      this delay (allow you to generate many frames from the same Block/
      Frame).

9.3.6.10.1.3.  BlockAdditionID Element

   name:  BlockAdditionID

   path:  "\Segment\Cluster\BlockGroup\Slices\TimeSlice\BlockAdditionID"

   id:  0xCB

   maxOccurs:  1

   default:  0

   type:  uinteger

   minver:  0

   maxver:  0

   definition:  The ID of the BlockAdditional Element (0 is the main
      Block).

9.3.6.10.1.4.  Delay Element

   name:  Delay

   path:  "\Segment\Cluster\BlockGroup\Slices\TimeSlice\Delay"

   id:  0xCE

   maxOccurs:  1

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   default:  0

   type:  uinteger

   minver:  0

   maxver:  0

   definition:  The (scaled) delay to apply to the Element.

9.3.6.10.1.5.  SliceDuration Element

   name:  SliceDuration

   path:  "\Segment\Cluster\BlockGroup\Slices\TimeSlice\SliceDuration"

   id:  0xCF

   maxOccurs:  1

   default:  0

   type:  uinteger

   minver:  0

   maxver:  0

   definition:  The (scaled) duration to apply to the Element.

9.3.6.11.  ReferenceFrame Element

   name:  ReferenceFrame

   path:  "\Segment\Cluster\BlockGroup\ReferenceFrame"

   id:  0xC8

   maxOccurs:  1

   type:  master

   minver:  0

   maxver:  0

   definition:  Contains information about the last reference frame.
      See [DivXTrickTrack].

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9.3.6.11.1.  ReferenceOffset Element

   name:  ReferenceOffset

   path:  "\Segment\Cluster\BlockGroup\ReferenceFrame\ReferenceOffset"

   id:  0xC9

   minOccurs:  1

   maxOccurs:  1

   type:  uinteger

   minver:  0

   maxver:  0

   definition:  The relative offset, in bytes, from the previous
      BlockGroup element for this Smooth FF/RW video track to the
      containing BlockGroup element.  See [DivXTrickTrack].

9.3.6.11.2.  ReferenceTimestamp Element

   name:  ReferenceTimestamp

   path:  "\Segment\Cluster\BlockGroup\ReferenceFrame\ReferenceTimestamp
      "

   id:  0xCA

   minOccurs:  1

   maxOccurs:  1

   type:  uinteger

   minver:  0

   maxver:  0

   definition:  The timecode of the BlockGroup pointed to by
      ReferenceOffset.  See [DivXTrickTrack].

9.3.7.  EncryptedBlock Element

   name:  EncryptedBlock

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   path:  "\Segment\Cluster\EncryptedBlock"

   id:  0xAF

   type:  binary

   minver:  0

   maxver:  0

   definition:  Similar to SimpleBlock, see Section 6.2.4.4, but the
      data inside the Block are Transformed (encrypt and/or signed).

9.4.  Tracks Element

   name:  Tracks

   path:  "\Segment\Tracks"

   id:  0x1654AE6B

   maxOccurs:  1

   type:  master

   recurring:  1

   definition:  A Top-Level Element of information with many tracks
      described.

9.4.1.  TrackEntry Element

   name:  TrackEntry

   path:  "\Segment\Tracks\TrackEntry"

   id:  0xAE

   minOccurs:  1

   type:  master

   definition:  Describes a track with all Elements.

9.4.1.1.  TrackNumber Element

   name:  TrackNumber

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   path:  "\Segment\Tracks\TrackEntry\TrackNumber"

   id:  0xD7

   minOccurs:  1

   maxOccurs:  1

   range:  not 0

   type:  uinteger

   definition:  The track number as used in the Block Header (using more
      than 127 tracks is not encouraged, though the design allows an
      unlimited number).

9.4.1.2.  TrackUID Element

   name:  TrackUID

   path:  "\Segment\Tracks\TrackEntry\TrackUID"

   id:  0x73C5

   minOccurs:  1

   maxOccurs:  1

   range:  not 0

   type:  uinteger

   definition:  A unique ID to identify the Track.  This SHOULD be kept
      the same when making a direct stream copy of the Track to another
      file.

9.4.1.3.  TrackType Element

   name:  TrackType

   path:  "\Segment\Tracks\TrackEntry\TrackType"

   id:  0x83

   minOccurs:  1

   maxOccurs:  1

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   range:  1-254

   type:  uinteger

   definition:  A set of track types coded on 8 bits.

   restrictions:

                           +=======+==========+
                           | value | label    |
                           +=======+==========+
                           | 1     | video    |
                           +-------+----------+
                           | 2     | audio    |
                           +-------+----------+
                           | 3     | complex  |
                           +-------+----------+
                           | 16    | logo     |
                           +-------+----------+
                           | 17    | subtitle |
                           +-------+----------+
                           | 18    | buttons  |
                           +-------+----------+
                           | 32    | control  |
                           +-------+----------+
                           | 33    | metadata |
                           +-------+----------+

                                 Table 11

9.4.1.4.  FlagEnabled Element

   name:  FlagEnabled

   path:  "\Segment\Tracks\TrackEntry\FlagEnabled"

   id:  0xB9

   minOccurs:  1

   maxOccurs:  1

   range:  0-1

   default:  1

   type:  uinteger

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   minver:  2

   definition:  Set to 1 if the track is usable.  It is possible to turn
      a not usable track into a usable track using chapter codecs or
      control tracks.

9.4.1.5.  FlagDefault Element

   name:  FlagDefault

   path:  "\Segment\Tracks\TrackEntry\FlagDefault"

   id:  0x88

   minOccurs:  1

   maxOccurs:  1

   range:  0-1

   default:  1

   type:  uinteger

   definition:  Set if that track (audio, video or subs) SHOULD be
      eligible for automatic selection by the player; see Section 25 for
      more details.

9.4.1.6.  FlagForced Element

   name:  FlagForced

   path:  "\Segment\Tracks\TrackEntry\FlagForced"

   id:  0x55AA

   minOccurs:  1

   maxOccurs:  1

   range:  0-1

   default:  0

   type:  uinteger

   definition:  Applies only to subtitles.  Set if that track SHOULD be

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      eligible for automatic selection by the player if it matches the
      user's language preference, even if the user's preferences would
      normally not enable subtitles with the selected audio track; this
      can be used for tracks containing only translations of foreign-
      language audio or onscreen text.  See Section 25 for more details.

9.4.1.7.  FlagHearingImpaired Element

   name:  FlagHearingImpaired

   path:  "\Segment\Tracks\TrackEntry\FlagHearingImpaired"

   id:  0x55AB

   maxOccurs:  1

   range:  0-1

   type:  uinteger

   definition:  Set to 1 if that track is suitable for users with
      hearing impairments, set to 0 if it is unsuitable for users with
      hearing impairments.

9.4.1.8.  FlagVisualImpaired Element

   name:  FlagVisualImpaired

   path:  "\Segment\Tracks\TrackEntry\FlagVisualImpaired"

   id:  0x55AC

   maxOccurs:  1

   range:  0-1

   type:  uinteger

   definition:  Set to 1 if that track is suitable for users with visual
      impairments, set to 0 if it is unsuitable for users with visual
      impairments.

9.4.1.9.  FlagTextDescriptions Element

   name:  FlagTextDescriptions

   path:  "\Segment\Tracks\TrackEntry\FlagTextDescriptions"

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   id:  0x55AD

   maxOccurs:  1

   range:  0-1

   type:  uinteger

   definition:  Set to 1 if that track contains textual descriptions of
      video content, set to 0 if that track does not contain textual
      descriptions of video content.

9.4.1.10.  FlagOriginal Element

   name:  FlagOriginal

   path:  "\Segment\Tracks\TrackEntry\FlagOriginal"

   id:  0x55AE

   maxOccurs:  1

   range:  0-1

   type:  uinteger

   definition:  Set to 1 if that track is in the content's original
      language, set to 0 if it is a translation.

9.4.1.11.  FlagCommentary Element

   name:  FlagCommentary

   path:  "\Segment\Tracks\TrackEntry\FlagCommentary"

   id:  0x55AF

   maxOccurs:  1

   range:  0-1

   type:  uinteger

   definition:  Set to 1 if that track contains commentary, set to 0 if
      it does not contain commentary.

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9.4.1.12.  FlagLacing Element

   name:  FlagLacing

   path:  "\Segment\Tracks\TrackEntry\FlagLacing"

   id:  0x9C

   minOccurs:  1

   maxOccurs:  1

   range:  0-1

   default:  1

   type:  uinteger

   definition:  Set to 1 if the track MAY contain blocks using lacing.

9.4.1.13.  MinCache Element

   name:  MinCache

   path:  "\Segment\Tracks\TrackEntry\MinCache"

   id:  0x6DE7

   minOccurs:  1

   maxOccurs:  1

   default:  0

   type:  uinteger

   definition:  The minimum number of frames a player SHOULD be able to
      cache during playback.  If set to 0, the reference pseudo-cache
      system is not used.

9.4.1.14.  MaxCache Element

   name:  MaxCache

   path:  "\Segment\Tracks\TrackEntry\MaxCache"

   id:  0x6DF8

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   maxOccurs:  1

   type:  uinteger

   definition:  The maximum cache size necessary to store referenced
      frames in and the current frame. 0 means no cache is needed.

9.4.1.15.  DefaultDuration Element

   name:  DefaultDuration

   path:  "\Segment\Tracks\TrackEntry\DefaultDuration"

   id:  0x23E383

   maxOccurs:  1

   range:  not 0

   type:  uinteger

   definition:  Number of nanoseconds (not scaled via TimestampScale)
      per frame (frame in the Matroska sense -- one Element put into a
      (Simple)Block).

9.4.1.16.  DefaultDecodedFieldDuration Element

   name:  DefaultDecodedFieldDuration

   path:  "\Segment\Tracks\TrackEntry\DefaultDecodedFieldDuration"

   id:  0x234E7A

   maxOccurs:  1

   range:  not 0

   type:  uinteger

   minver:  4

   definition:  The period in nanoseconds (not scaled by TimestampScale)
      between two successive fields at the output of the decoding
      process, see Section 17 for more information

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9.4.1.17.  TrackTimestampScale Element

   name:  TrackTimestampScale

   path:  "\Segment\Tracks\TrackEntry\TrackTimestampScale"

   id:  0x23314F

   minOccurs:  1

   maxOccurs:  1

   range:  > 0x0p+0

   default:  0x1p+0

   type:  float

   maxver:  3

   definition:  DEPRECATED, DO NOT USE.  The scale to apply on this
      track to work at normal speed in relation with other tracks
      (mostly used to adjust video speed when the audio length differs).

9.4.1.18.  TrackOffset Element

   name:  TrackOffset

   path:  "\Segment\Tracks\TrackEntry\TrackOffset"

   id:  0x537F

   maxOccurs:  1

   default:  0

   type:  integer

   minver:  0

   maxver:  0

   definition:  A value to add to the Block's Timestamp.  This can be
      used to adjust the playback offset of a track.

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9.4.1.19.  MaxBlockAdditionID Element

   name:  MaxBlockAdditionID

   path:  "\Segment\Tracks\TrackEntry\MaxBlockAdditionID"

   id:  0x55EE

   minOccurs:  1

   maxOccurs:  1

   default:  0

   type:  uinteger

   definition:  The maximum value of BlockAddID (Section 9.3.6.3.1.1).
      A value 0 means there is no BlockAdditions (Section 9.3.6.3) for
      this track.

9.4.1.20.  BlockAdditionMapping Element

   name:  BlockAdditionMapping

   path:  "\Segment\Tracks\TrackEntry\BlockAdditionMapping"

   id:  0x41E4

   type:  master

   minver:  4

   definition:  Contains elements that extend the track format, by
      adding content either to each frame, with BlockAddID
      (Section 9.3.6.3.1.1), or to the track as a whole with
      BlockAddIDExtraData.

9.4.1.20.1.  BlockAddIDValue Element

   name:  BlockAddIDValue

   path:  "\Segment\Tracks\TrackEntry\BlockAdditionMapping\BlockAddIDVal
      ue"

   id:  0x41F0

   maxOccurs:  1

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   range:  >=2

   type:  uinteger

   minver:  4

   definition:  If the track format extension needs content beside
      frames, the value refers to the BlockAddID (Section 9.3.6.3.1.1),
      value being described.  To keep MaxBlockAdditionID as low as
      possible, small values SHOULD be used.

9.4.1.20.2.  BlockAddIDName Element

   name:  BlockAddIDName

   path:  "\Segment\Tracks\TrackEntry\BlockAdditionMapping\BlockAddIDNam
      e"

   id:  0x41A4

   maxOccurs:  1

   type:  string

   minver:  4

   definition:  A human-friendly name describing the type of
      BlockAdditional data, as defined by the associated Block
      Additional Mapping.

9.4.1.20.3.  BlockAddIDType Element

   name:  BlockAddIDType

   path:  "\Segment\Tracks\TrackEntry\BlockAdditionMapping\BlockAddIDTyp
      e"

   id:  0x41E7

   minOccurs:  1

   maxOccurs:  1

   default:  0

   type:  uinteger

   minver:  4

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   definition:  Stores the registered identifer of the Block Additional
      Mapping to define how the BlockAdditional data should be handled.

9.4.1.20.4.  BlockAddIDExtraData Element

   name:  BlockAddIDExtraData

   path:  "\Segment\Tracks\TrackEntry\BlockAdditionMapping\BlockAddIDExt
      raData"

   id:  0x41ED

   maxOccurs:  1

   type:  binary

   minver:  4

   definition:  Extra binary data that the BlockAddIDType can use to
      interpret the BlockAdditional data.  The intepretation of the
      binary data depends on the BlockAddIDType value and the
      corresponding Block Additional Mapping.

9.4.1.21.  Name Element

   name:  Name

   path:  "\Segment\Tracks\TrackEntry\Name"

   id:  0x536E

   maxOccurs:  1

   type:  utf-8

   definition:  A human-readable track name.

9.4.1.22.  Language Element

   name:  Language

   path:  "\Segment\Tracks\TrackEntry\Language"

   id:  0x22B59C

   minOccurs:  1

   maxOccurs:  1

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   default:  eng

   type:  string

   definition:  Specifies the language of the track in the Matroska
      languages form; see Section 6.2.1 on language codes.  This Element
      MUST be ignored if the LanguageIETF Element is used in the same
      TrackEntry.

9.4.1.23.  LanguageIETF Element

   name:  LanguageIETF

   path:  "\Segment\Tracks\TrackEntry\LanguageIETF"

   id:  0x22B59D

   maxOccurs:  1

   type:  string

   minver:  4

   definition:  Specifies the language of the track according to [BCP47]
      and using the IANA Language Subtag Registry [IANALangRegistry].
      If this Element is used, then any Language Elements used in the
      same TrackEntry MUST be ignored.

9.4.1.24.  CodecID Element

   name:  CodecID

   path:  "\Segment\Tracks\TrackEntry\CodecID"

   id:  0x86

   minOccurs:  1

   maxOccurs:  1

   type:  string

   definition:  An ID corresponding to the codec, see
      [I-D.ietf-cellar-codec] for more info.

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9.4.1.25.  CodecPrivate Element

   name:  CodecPrivate

   path:  "\Segment\Tracks\TrackEntry\CodecPrivate"

   id:  0x63A2

   maxOccurs:  1

   type:  binary

   definition:  Private data only known to the codec.

9.4.1.26.  CodecName Element

   name:  CodecName

   path:  "\Segment\Tracks\TrackEntry\CodecName"

   id:  0x258688

   maxOccurs:  1

   type:  utf-8

   definition:  A human-readable string specifying the codec.

9.4.1.27.  AttachmentLink Element

   name:  AttachmentLink

   path:  "\Segment\Tracks\TrackEntry\AttachmentLink"

   id:  0x7446

   maxOccurs:  1

   range:  not 0

   type:  uinteger

   maxver:  3

   definition:  The UID of an attachment that is used by this codec.

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9.4.1.28.  CodecSettings Element

   name:  CodecSettings

   path:  "\Segment\Tracks\TrackEntry\CodecSettings"

   id:  0x3A9697

   maxOccurs:  1

   type:  utf-8

   minver:  0

   maxver:  0

   definition:  A string describing the encoding setting used.

9.4.1.29.  CodecInfoURL Element

   name:  CodecInfoURL

   path:  "\Segment\Tracks\TrackEntry\CodecInfoURL"

   id:  0x3B4040

   type:  string

   minver:  0

   maxver:  0

   definition:  A URL to find information about the codec used.

9.4.1.30.  CodecDownloadURL Element

   name:  CodecDownloadURL

   path:  "\Segment\Tracks\TrackEntry\CodecDownloadURL"

   id:  0x26B240

   type:  string

   minver:  0

   maxver:  0

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   definition:  A URL to download about the codec used.

9.4.1.31.  CodecDecodeAll Element

   name:  CodecDecodeAll

   path:  "\Segment\Tracks\TrackEntry\CodecDecodeAll"

   id:  0xAA

   minOccurs:  1

   maxOccurs:  1

   range:  0-1

   default:  1

   type:  uinteger

   minver:  2

   definition:  The codec can decode potentially damaged data.

9.4.1.32.  TrackOverlay Element

   name:  TrackOverlay

   path:  "\Segment\Tracks\TrackEntry\TrackOverlay"

   id:  0x6FAB

   type:  uinteger

   definition:  Specify that this track is an overlay track for the
      Track specified (in the u-integer).  That means when this track
      has a gap, see Section 9.3.2 on SilentTracks, the overlay track
      SHOULD be used instead.  The order of multiple TrackOverlay
      matters, the first one is the one that SHOULD be used.  If not
      found it SHOULD be the second, etc.

9.4.1.33.  CodecDelay Element

   name:  CodecDelay

   path:  "\Segment\Tracks\TrackEntry\CodecDelay"

   id:  0x56AA

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   maxOccurs:  1

   default:  0

   type:  uinteger

   minver:  4

   definition:  CodecDelay is The codec-built-in delay in nanoseconds.
      This value MUST be subtracted from each block timestamp in order
      to get the actual timestamp.  The value SHOULD be small so the
      muxing of tracks with the same actual timestamp are in the same
      Cluster.

9.4.1.34.  SeekPreRoll Element

   name:  SeekPreRoll

   path:  "\Segment\Tracks\TrackEntry\SeekPreRoll"

   id:  0x56BB

   minOccurs:  1

   maxOccurs:  1

   default:  0

   type:  uinteger

   minver:  4

   definition:  After a discontinuity, SeekPreRoll is the duration in
      nanoseconds of the data the decoder MUST decode before the decoded
      data is valid.

9.4.1.35.  TrackTranslate Element

   name:  TrackTranslate

   path:  "\Segment\Tracks\TrackEntry\TrackTranslate"

   id:  0x6624

   type:  master

   definition:  The track identification for the given Chapter Codec.

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9.4.1.35.1.  TrackTranslateEditionUID Element

   name:  TrackTranslateEditionUID

   path:  "\Segment\Tracks\TrackEntry\TrackTranslate\TrackTranslateEditi
      onUID"

   id:  0x66FC

   type:  uinteger

   definition:  Specify an edition UID on which this translation
      applies.  When not specified, it means for all editions found in
      the Segment.

9.4.1.35.2.  TrackTranslateCodec Element

   name:  TrackTranslateCodec

   path:  "\Segment\Tracks\TrackEntry\TrackTranslate\TrackTranslateCodec
      "

   id:  0x66BF

   minOccurs:  1

   maxOccurs:  1

   type:  uinteger

   definition:  The chapter codec; see Section 9.7.1.4.10.1.

   restrictions:

                        +=======+=================+
                        | value | label           |
                        +=======+=================+
                        | 0     | Matroska Script |
                        +-------+-----------------+
                        | 1     | DVD-menu        |
                        +-------+-----------------+

                                  Table 12

9.4.1.35.3.  TrackTranslateTrackID Element

   name:  TrackTranslateTrackID

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   path:  "\Segment\Tracks\TrackEntry\TrackTranslate\TrackTranslateTrack
      ID"

   id:  0x66A5

   minOccurs:  1

   maxOccurs:  1

   type:  binary

   definition:  The binary value used to represent this track in the
      chapter codec data.  The format depends on the ChapProcessCodecID
      used; see Section 9.7.1.4.10.1.

9.4.1.36.  Video Element

   name:  Video

   path:  "\Segment\Tracks\TrackEntry\Video"

   id:  0xE0

   maxOccurs:  1

   type:  master

   definition:  Video settings.

9.4.1.36.1.  FlagInterlaced Element

   name:  FlagInterlaced

   path:  "\Segment\Tracks\TrackEntry\Video\FlagInterlaced"

   id:  0x9A

   minOccurs:  1

   maxOccurs:  1

   range:  0-2

   default:  0

   type:  uinteger

   minver:  2

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   definition:  A flag to declare if the video is known to be
      progressive, or interlaced, and if applicable to declare details
      about the interlacement.

   restrictions:

                         +=======+==============+
                         | value | label        |
                         +=======+==============+
                         | 0     | undetermined |
                         +-------+--------------+
                         | 1     | interlaced   |
                         +-------+--------------+
                         | 2     | progressive  |
                         +-------+--------------+

                                 Table 13

9.4.1.36.2.  FieldOrder Element

   name:  FieldOrder

   path:  "\Segment\Tracks\TrackEntry\Video\FieldOrder"

   id:  0x9D

   minOccurs:  1

   maxOccurs:  1

   range:  0-14

   default:  2

   type:  uinteger

   minver:  4

   definition:  Declare the field ordering of the video.  If
      FlagInterlaced is not set to 1, this Element MUST be ignored.

   restrictions:

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   +===================+==============+===============================+
   | value             | label        | documentation                 |
   +===================+==============+===============================+
   | 0                 | progressive  |                               |
   +-------------------+--------------+-------------------------------+
   | 1                 | tff          | Top field displayed first.    |
   |                   |              | Top field stored first.       |
   +-------------------+--------------+-------------------------------+
   | 2                 | undetermined |                               |
   +-------------------+--------------+-------------------------------+
   | 6                 | bff          | Bottom field displayed first. |
   |                   |              | Bottom field stored first.    |
   +-------------------+--------------+-------------------------------+
   | 9                 | bff(swapped) | Top field displayed first.    |
   |                   |              | Fields are interleaved in     |
   |                   |              | storage                       |
   +-------------------+--------------+-------------------------------+
   | with the top line |              |                               |
   | of the top field  |              |                               |
   | stored first.     |              |                               |
   +-------------------+--------------+-------------------------------+
   | 14                | tff(swapped) | Bottom field displayed first. |
   |                   |              | Fields are interleaved in     |
   |                   |              | storage                       |
   +-------------------+--------------+-------------------------------+
   | with the top line |              |                               |
   | of the top field  |              |                               |
   | stored first.     |              |                               |
   +-------------------+--------------+-------------------------------+

                                 Table 14

9.4.1.36.3.  StereoMode Element

   name:  StereoMode

   path:  "\Segment\Tracks\TrackEntry\Video\StereoMode"

   id:  0x53B8

   maxOccurs:  1

   default:  0

   type:  uinteger

   minver:  3

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   definition:  Stereo-3D video mode.  There are some more details in
      Section 24.10.

   restrictions:

       +=======+===================================================+
       | value | label                                             |
       +=======+===================================================+
       | 0     | mono                                              |
       +-------+---------------------------------------------------+
       | 1     | side by side (left eye first)                     |
       +-------+---------------------------------------------------+
       | 2     | top - bottom (right eye is first)                 |
       +-------+---------------------------------------------------+
       | 3     | top - bottom (left eye is first)                  |
       +-------+---------------------------------------------------+
       | 4     | checkboard (right eye is first)                   |
       +-------+---------------------------------------------------+
       | 5     | checkboard (left eye is first)                    |
       +-------+---------------------------------------------------+
       | 6     | row interleaved (right eye is first)              |
       +-------+---------------------------------------------------+
       | 7     | row interleaved (left eye is first)               |
       +-------+---------------------------------------------------+
       | 8     | column interleaved (right eye is first)           |
       +-------+---------------------------------------------------+
       | 9     | column interleaved (left eye is first)            |
       +-------+---------------------------------------------------+
       | 10    | anaglyph (cyan/red)                               |
       +-------+---------------------------------------------------+
       | 11    | side by side (right eye first)                    |
       +-------+---------------------------------------------------+
       | 12    | anaglyph (green/magenta)                          |
       +-------+---------------------------------------------------+
       | 13    | both eyes laced in one Block (left eye is first)  |
       +-------+---------------------------------------------------+
       | 14    | both eyes laced in one Block (right eye is first) |
       +-------+---------------------------------------------------+

                                  Table 15

9.4.1.36.4.  AlphaMode Element

   name:  AlphaMode

   path:  "\Segment\Tracks\TrackEntry\Video\AlphaMode"

   id:  0x53C0

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   maxOccurs:  1

   default:  0

   type:  uinteger

   minver:  3

   definition:  Alpha Video Mode.  Presence of this Element indicates
      that the BlockAdditional Element could contain Alpha data.

9.4.1.36.5.  OldStereoMode Element

   name:  OldStereoMode

   path:  "\Segment\Tracks\TrackEntry\Video\OldStereoMode"

   id:  0x53B9

   maxOccurs:  1

   type:  uinteger

   maxver:  0

   definition:  DEPRECATED, DO NOT USE.  Bogus StereoMode value used in
      old versions of libmatroska.

   restrictions:

                           +=======+===========+
                           | value | label     |
                           +=======+===========+
                           | 0     | mono      |
                           +-------+-----------+
                           | 1     | right eye |
                           +-------+-----------+
                           | 2     | left eye  |
                           +-------+-----------+
                           | 3     | both eyes |
                           +-------+-----------+

                                  Table 16

9.4.1.36.6.  PixelWidth Element

   name:  PixelWidth

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   path:  "\Segment\Tracks\TrackEntry\Video\PixelWidth"

   id:  0xB0

   minOccurs:  1

   maxOccurs:  1

   range:  not 0

   type:  uinteger

   definition:  Width of the encoded video frames in pixels.

9.4.1.36.7.  PixelHeight Element

   name:  PixelHeight

   path:  "\Segment\Tracks\TrackEntry\Video\PixelHeight"

   id:  0xBA

   minOccurs:  1

   maxOccurs:  1

   range:  not 0

   type:  uinteger

   definition:  Height of the encoded video frames in pixels.

9.4.1.36.8.  PixelCropBottom Element

   name:  PixelCropBottom

   path:  "\Segment\Tracks\TrackEntry\Video\PixelCropBottom"

   id:  0x54AA

   maxOccurs:  1

   default:  0

   type:  uinteger

   definition:  The number of video pixels to remove at the bottom of
      the image.

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9.4.1.36.9.  PixelCropTop Element

   name:  PixelCropTop

   path:  "\Segment\Tracks\TrackEntry\Video\PixelCropTop"

   id:  0x54BB

   maxOccurs:  1

   default:  0

   type:  uinteger

   definition:  The number of video pixels to remove at the top of the
      image.

9.4.1.36.10.  PixelCropLeft Element

   name:  PixelCropLeft

   path:  "\Segment\Tracks\TrackEntry\Video\PixelCropLeft"

   id:  0x54CC

   maxOccurs:  1

   default:  0

   type:  uinteger

   definition:  The number of video pixels to remove on the left of the
      image.

9.4.1.36.11.  PixelCropRight Element

   name:  PixelCropRight

   path:  "\Segment\Tracks\TrackEntry\Video\PixelCropRight"

   id:  0x54DD

   maxOccurs:  1

   default:  0

   type:  uinteger

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   definition:  The number of video pixels to remove on the right of the
      image.

9.4.1.36.12.  DisplayWidth Element

   name:  DisplayWidth

   path:  "\Segment\Tracks\TrackEntry\Video\DisplayWidth"

   id:  0x54B0

   maxOccurs:  1

   range:  not 0

   default: see implementation notes

   type:  uinteger

   definition:  Width of the video frames to display.  Applies to the
      video frame after cropping (PixelCrop* Elements).

   implementation notes:

    +============================+====================================+
    | attribute                  | note                               |
    +============================+====================================+
    | default                    | If the DisplayUnit of the same     |
    |                            | TrackEntry is 0, then the default  |
    |                            | value for DisplayWidth is equal to |
    +----------------------------+------------------------------------+
    | PixelWidth - PixelCropLeft |                                    |
    | - PixelCropRight, else     |                                    |
    | there is no default value. |                                    |
    +----------------------------+------------------------------------+

                                  Table 17

9.4.1.36.13.  DisplayHeight Element

   name:  DisplayHeight

   path:  "\Segment\Tracks\TrackEntry\Video\DisplayHeight"

   id:  0x54BA

   maxOccurs:  1

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   range:  not 0

   default: see implementation notes

   type:  uinteger

   definition:  Height of the video frames to display.  Applies to the
      video frame after cropping (PixelCrop* Elements).

   implementation notes:

   +============================+=====================================+
   | attribute                  | note                                |
   +============================+=====================================+
   | default                    | If the DisplayUnit of the same      |
   |                            | TrackEntry is 0, then the default   |
   |                            | value for DisplayHeight is equal to |
   +----------------------------+-------------------------------------+
   | PixelHeight - PixelCropTop |                                     |
   | - PixelCropBottom, else    |                                     |
   | there is no default value. |                                     |
   +----------------------------+-------------------------------------+

                                 Table 18

9.4.1.36.14.  DisplayUnit Element

   name:  DisplayUnit

   path:  "\Segment\Tracks\TrackEntry\Video\DisplayUnit"

   id:  0x54B2

   maxOccurs:  1

   default:  0

   type:  uinteger

   definition:  How DisplayWidth & DisplayHeight are interpreted.

   restrictions:

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                     +=======+======================+
                     | value | label                |
                     +=======+======================+
                     | 0     | pixels               |
                     +-------+----------------------+
                     | 1     | centimeters          |
                     +-------+----------------------+
                     | 2     | inches               |
                     +-------+----------------------+
                     | 3     | display aspect ratio |
                     +-------+----------------------+
                     | 4     | unknown              |
                     +-------+----------------------+

                                 Table 19

9.4.1.36.15.  AspectRatioType Element

   name:  AspectRatioType

   path:  "\Segment\Tracks\TrackEntry\Video\AspectRatioType"

   id:  0x54B3

   maxOccurs:  1

   default:  0

   type:  uinteger

   definition:  Specify the possible modifications to the aspect ratio.

   restrictions:

                       +=======+===================+
                       | value | label             |
                       +=======+===================+
                       | 0     | free resizing     |
                       +-------+-------------------+
                       | 1     | keep aspect ratio |
                       +-------+-------------------+
                       | 2     | fixed             |
                       +-------+-------------------+

                                  Table 20

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9.4.1.36.16.  ColourSpace Element

   name:  ColourSpace

   path:  "\Segment\Tracks\TrackEntry\Video\ColourSpace"

   id:  0x2EB524

   minOccurs: see implementation notes

   maxOccurs:  1

   type:  binary

   definition:  Specify the pixel format used for the Track's data as a
      FourCC.  This value is similar in scope to the biCompression value
      of AVI's BITMAPINFOHEADER.

   implementation notes:

        +===========+============================================+
        | attribute | note                                       |
        +===========+============================================+
        | minOccurs | ColourSpace MUST be set (minOccurs=1) in   |
        |           | TrackEntry, when the CodecID Element of    |
        |           | the TrackEntry is set to "V_UNCOMPRESSED". |
        +-----------+--------------------------------------------+

                                 Table 21

9.4.1.36.17.  GammaValue Element

   name:  GammaValue

   path:  "\Segment\Tracks\TrackEntry\Video\GammaValue"

   id:  0x2FB523

   maxOccurs:  1

   range:  > 0x0p+0

   type:  float

   minver:  0

   maxver:  0

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   definition:  Gamma Value.

9.4.1.36.18.  FrameRate Element

   name:  FrameRate

   path:  "\Segment\Tracks\TrackEntry\Video\FrameRate"

   id:  0x2383E3

   maxOccurs:  1

   range:  > 0x0p+0

   type:  float

   minver:  0

   maxver:  0

   definition:  Number of frames per second.  This value is
      Informational only.  It is intended for constant frame rate
      streams, and SHOULD NOT be used for a variable frame rate
      TrackEntry.

9.4.1.36.19.  Colour Element

   name:  Colour

   path:  "\Segment\Tracks\TrackEntry\Video\Colour"

   id:  0x55B0

   maxOccurs:  1

   type:  master

   minver:  4

   definition:  Settings describing the colour format.

9.4.1.36.19.1.  MatrixCoefficients Element

   name:  MatrixCoefficients

   path:  "\Segment\Tracks\TrackEntry\Video\Colour\MatrixCoefficients"

   id:  0x55B1

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   maxOccurs:  1

   default:  2

   type:  uinteger

   minver:  4

   definition:  The Matrix Coefficients of the video used to derive luma
      and chroma values from red, green, and blue color primaries.  For
      clarity, the value and meanings for MatrixCoefficients are adopted
      from Table 4 of ISO/IEC 23001-8:2016 or ITU-T H.273.

   restrictions:

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             +=======+=======================================+
             | value | label                                 |
             +=======+=======================================+
             | 0     | Identity                              |
             +-------+---------------------------------------+
             | 1     | ITU-R BT.709                          |
             +-------+---------------------------------------+
             | 2     | unspecified                           |
             +-------+---------------------------------------+
             | 3     | reserved                              |
             +-------+---------------------------------------+
             | 4     | US FCC 73.682                         |
             +-------+---------------------------------------+
             | 5     | ITU-R BT.470BG                        |
             +-------+---------------------------------------+
             | 6     | SMPTE 170M                            |
             +-------+---------------------------------------+
             | 7     | SMPTE 240M                            |
             +-------+---------------------------------------+
             | 8     | YCoCg                                 |
             +-------+---------------------------------------+
             | 9     | BT2020 Non-constant Luminance         |
             +-------+---------------------------------------+
             | 10    | BT2020 Constant Luminance             |
             +-------+---------------------------------------+
             | 11    | SMPTE ST 2085                         |
             +-------+---------------------------------------+
             | 12    | Chroma-derived Non-constant Luminance |
             +-------+---------------------------------------+
             | 13    | Chroma-derived Constant Luminance     |
             +-------+---------------------------------------+
             | 14    | ITU-R BT.2100-0                       |
             +-------+---------------------------------------+

                                  Table 22

9.4.1.36.19.2.  BitsPerChannel Element

   name:  BitsPerChannel

   path:  "\Segment\Tracks\TrackEntry\Video\Colour\BitsPerChannel"

   id:  0x55B2

   maxOccurs:  1

   default:  0

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   type:  uinteger

   minver:  4

   definition:  Number of decoded bits per channel.  A value of 0
      indicates that the BitsPerChannel is unspecified.

9.4.1.36.19.3.  ChromaSubsamplingHorz Element

   name:  ChromaSubsamplingHorz

   path:  "\Segment\Tracks\TrackEntry\Video\Colour\ChromaSubsamplingHorz
      "

   id:  0x55B3

   maxOccurs:  1

   type:  uinteger

   minver:  4

   definition:  The amount of pixels to remove in the Cr and Cb channels
      for every pixel not removed horizontally.  Example: For video with
      4:2:0 chroma subsampling, the ChromaSubsamplingHorz SHOULD be set
      to 1.

9.4.1.36.19.4.  ChromaSubsamplingVert Element

   name:  ChromaSubsamplingVert

   path:  "\Segment\Tracks\TrackEntry\Video\Colour\ChromaSubsamplingVert
      "

   id:  0x55B4

   maxOccurs:  1

   type:  uinteger

   minver:  4

   definition:  The amount of pixels to remove in the Cr and Cb channels
      for every pixel not removed vertically.  Example: For video with
      4:2:0 chroma subsampling, the ChromaSubsamplingVert SHOULD be set
      to 1.

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9.4.1.36.19.5.  CbSubsamplingHorz Element

   name:  CbSubsamplingHorz

   path:  "\Segment\Tracks\TrackEntry\Video\Colour\CbSubsamplingHorz"

   id:  0x55B5

   maxOccurs:  1

   type:  uinteger

   minver:  4

   definition:  The amount of pixels to remove in the Cb channel for
      every pixel not removed horizontally.  This is additive with
      ChromaSubsamplingHorz.  Example: For video with 4:2:1 chroma
      subsampling, the ChromaSubsamplingHorz SHOULD be set to 1 and
      CbSubsamplingHorz SHOULD be set to 1.

9.4.1.36.19.6.  CbSubsamplingVert Element

   name:  CbSubsamplingVert

   path:  "\Segment\Tracks\TrackEntry\Video\Colour\CbSubsamplingVert"

   id:  0x55B6

   maxOccurs:  1

   type:  uinteger

   minver:  4

   definition:  The amount of pixels to remove in the Cb channel for
      every pixel not removed vertically.  This is additive with
      ChromaSubsamplingVert.

9.4.1.36.19.7.  ChromaSitingHorz Element

   name:  ChromaSitingHorz

   path:  "\Segment\Tracks\TrackEntry\Video\Colour\ChromaSitingHorz"

   id:  0x55B7

   maxOccurs:  1

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   default:  0

   type:  uinteger

   minver:  4

   definition:  How chroma is subsampled horizontally.

   restrictions:

                        +=======+=================+
                        | value | label           |
                        +=======+=================+
                        | 0     | unspecified     |
                        +-------+-----------------+
                        | 1     | left collocated |
                        +-------+-----------------+
                        | 2     | half            |
                        +-------+-----------------+

                                  Table 23

9.4.1.36.19.8.  ChromaSitingVert Element

   name:  ChromaSitingVert

   path:  "\Segment\Tracks\TrackEntry\Video\Colour\ChromaSitingVert"

   id:  0x55B8

   maxOccurs:  1

   default:  0

   type:  uinteger

   minver:  4

   definition:  How chroma is subsampled vertically.

   restrictions:

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                        +=======+================+
                        | value | label          |
                        +=======+================+
                        | 0     | unspecified    |
                        +-------+----------------+
                        | 1     | top collocated |
                        +-------+----------------+
                        | 2     | half           |
                        +-------+----------------+

                                 Table 24

9.4.1.36.19.9.  Range Element

   name:  Range

   path:  "\Segment\Tracks\TrackEntry\Video\Colour\Range"

   id:  0x55B9

   maxOccurs:  1

   default:  0

   type:  uinteger

   minver:  4

   definition:  Clipping of the color ranges.

   restrictions:

    +=======+=========================================================+
    | value | label                                                   |
    +=======+=========================================================+
    | 0     | unspecified                                             |
    +-------+---------------------------------------------------------+
    | 1     | broadcast range                                         |
    +-------+---------------------------------------------------------+
    | 2     | full range (no clipping)                                |
    +-------+---------------------------------------------------------+
    | 3     | defined by MatrixCoefficients / TransferCharacteristics |
    +-------+---------------------------------------------------------+

                                  Table 25

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9.4.1.36.19.10.  TransferCharacteristics Element

   name:  TransferCharacteristics

   path:  "\Segment\Tracks\TrackEntry\Video\Colour\TransferCharacteristi
      cs"

   id:  0x55BA

   maxOccurs:  1

   default:  2

   type:  uinteger

   minver:  4

   definition:  The transfer characteristics of the video.  For clarity,
      the value and meanings for TransferCharacteristics are adopted
      from Table 3 of ISO/IEC 23091-4 or ITU-T H.273.

   restrictions:

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             +=======+=======================================+
             | value | label                                 |
             +=======+=======================================+
             | 0     | reserved                              |
             +-------+---------------------------------------+
             | 1     | ITU-R BT.709                          |
             +-------+---------------------------------------+
             | 2     | unspecified                           |
             +-------+---------------------------------------+
             | 3     | reserved                              |
             +-------+---------------------------------------+
             | 4     | Gamma 2.2 curve - BT.470M             |
             +-------+---------------------------------------+
             | 5     | Gamma 2.8 curve - BT.470BG            |
             +-------+---------------------------------------+
             | 6     | SMPTE 170M                            |
             +-------+---------------------------------------+
             | 7     | SMPTE 240M                            |
             +-------+---------------------------------------+
             | 8     | Linear                                |
             +-------+---------------------------------------+
             | 9     | Log                                   |
             +-------+---------------------------------------+
             | 10    | Log Sqrt                              |
             +-------+---------------------------------------+
             | 11    | IEC 61966-2-4                         |
             +-------+---------------------------------------+
             | 12    | ITU-R BT.1361 Extended Colour Gamut   |
             +-------+---------------------------------------+
             | 13    | IEC 61966-2-1                         |
             +-------+---------------------------------------+
             | 14    | ITU-R BT.2020 10 bit                  |
             +-------+---------------------------------------+
             | 15    | ITU-R BT.2020 12 bit                  |
             +-------+---------------------------------------+
             | 16    | ITU-R BT.2100 Perceptual Quantization |
             +-------+---------------------------------------+
             | 17    | SMPTE ST 428-1                        |
             +-------+---------------------------------------+
             | 18    | ARIB STD-B67 (HLG)                    |
             +-------+---------------------------------------+

                                  Table 26

9.4.1.36.19.11.  Primaries Element

   name:  Primaries

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   path:  "\Segment\Tracks\TrackEntry\Video\Colour\Primaries"

   id:  0x55BB

   maxOccurs:  1

   default:  2

   type:  uinteger

   minver:  4

   definition:  The colour primaries of the video.  For clarity, the
      value and meanings for Primaries are adopted from Table 2 of ISO/
      IEC 23091-4 or ITU-T H.273.

   restrictions:

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            +=======+========================================+
            | value | label                                  |
            +=======+========================================+
            | 0     | reserved                               |
            +-------+----------------------------------------+
            | 1     | ITU-R BT.709                           |
            +-------+----------------------------------------+
            | 2     | unspecified                            |
            +-------+----------------------------------------+
            | 3     | reserved                               |
            +-------+----------------------------------------+
            | 4     | ITU-R BT.470M                          |
            +-------+----------------------------------------+
            | 5     | ITU-R BT.470BG - BT.601 625            |
            +-------+----------------------------------------+
            | 6     | ITU-R BT.601 525 - SMPTE 170M          |
            +-------+----------------------------------------+
            | 7     | SMPTE 240M                             |
            +-------+----------------------------------------+
            | 8     | FILM                                   |
            +-------+----------------------------------------+
            | 9     | ITU-R BT.2020                          |
            +-------+----------------------------------------+
            | 10    | SMPTE ST 428-1                         |
            +-------+----------------------------------------+
            | 11    | SMPTE RP 432-2                         |
            +-------+----------------------------------------+
            | 12    | SMPTE EG 432-2                         |
            +-------+----------------------------------------+
            | 22    | EBU Tech. 3213-E - JEDEC P22 phosphors |
            +-------+----------------------------------------+

                                 Table 27

9.4.1.36.19.12.  MaxCLL Element

   name:  MaxCLL

   path:  "\Segment\Tracks\TrackEntry\Video\Colour\MaxCLL"

   id:  0x55BC

   maxOccurs:  1

   type:  uinteger

   minver:  4

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   definition:  Maximum brightness of a single pixel (Maximum Content
      Light Level) in candelas per square meter (cd/m^(2)).

9.4.1.36.19.13.  MaxFALL Element

   name:  MaxFALL

   path:  "\Segment\Tracks\TrackEntry\Video\Colour\MaxFALL"

   id:  0x55BD

   maxOccurs:  1

   type:  uinteger

   minver:  4

   definition:  Maximum brightness of a single full frame (Maximum
      Frame-Average Light Level) in candelas per square meter (cd/
      m^(2)).

9.4.1.36.19.14.  MasteringMetadata Element

   name:  MasteringMetadata

   path:  "\Segment\Tracks\TrackEntry\Video\Colour\MasteringMetadata"

   id:  0x55D0

   maxOccurs:  1

   type:  master

   minver:  4

   definition:  SMPTE 2086 mastering data.

9.4.1.36.19.15.  PrimaryRChromaticityX Element

   name:  PrimaryRChromaticityX

   path:  "\Segment\Tracks\TrackEntry\Video\Colour\MasteringMetadata\Pri
      maryRChromaticityX"

   id:  0x55D1

   maxOccurs:  1

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   range:  0-1

   type:  float

   minver:  4

   definition:  Red X chromaticity coordinate, as defined by CIE 1931.

9.4.1.36.19.16.  PrimaryRChromaticityY Element

   name:  PrimaryRChromaticityY

   path:  "\Segment\Tracks\TrackEntry\Video\Colour\MasteringMetadata\Pri
      maryRChromaticityY"

   id:  0x55D2

   maxOccurs:  1

   range:  0-1

   type:  float

   minver:  4

   definition:  Red Y chromaticity coordinate, as defined by CIE 1931.

9.4.1.36.19.17.  PrimaryGChromaticityX Element

   name:  PrimaryGChromaticityX

   path:  "\Segment\Tracks\TrackEntry\Video\Colour\MasteringMetadata\Pri
      maryGChromaticityX"

   id:  0x55D3

   maxOccurs:  1

   range:  0-1

   type:  float

   minver:  4

   definition:  Green X chromaticity coordinate, as defined by CIE 1931.

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9.4.1.36.19.18.  PrimaryGChromaticityY Element

   name:  PrimaryGChromaticityY

   path:  "\Segment\Tracks\TrackEntry\Video\Colour\MasteringMetadata\Pri
      maryGChromaticityY"

   id:  0x55D4

   maxOccurs:  1

   range:  0-1

   type:  float

   minver:  4

   definition:  Green Y chromaticity coordinate, as defined by CIE 1931.

9.4.1.36.19.19.  PrimaryBChromaticityX Element

   name:  PrimaryBChromaticityX

   path:  "\Segment\Tracks\TrackEntry\Video\Colour\MasteringMetadata\Pri
      maryBChromaticityX"

   id:  0x55D5

   maxOccurs:  1

   range:  0-1

   type:  float

   minver:  4

   definition:  Blue X chromaticity coordinate, as defined by CIE 1931.

9.4.1.36.19.20.  PrimaryBChromaticityY Element

   name:  PrimaryBChromaticityY

   path:  "\Segment\Tracks\TrackEntry\Video\Colour\MasteringMetadata\Pri
      maryBChromaticityY"

   id:  0x55D6

   maxOccurs:  1

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   range:  0-1

   type:  float

   minver:  4

   definition:  Blue Y chromaticity coordinate, as defined by CIE 1931.

9.4.1.36.19.21.  WhitePointChromaticityX Element

   name:  WhitePointChromaticityX

   path:  "\Segment\Tracks\TrackEntry\Video\Colour\MasteringMetadata\Whi
      tePointChromaticityX"

   id:  0x55D7

   maxOccurs:  1

   range:  0-1

   type:  float

   minver:  4

   definition:  White X chromaticity coordinate, as defined by CIE 1931.

9.4.1.36.19.22.  WhitePointChromaticityY Element

   name:  WhitePointChromaticityY

   path:  "\Segment\Tracks\TrackEntry\Video\Colour\MasteringMetadata\Whi
      tePointChromaticityY"

   id:  0x55D8

   maxOccurs:  1

   range:  0-1

   type:  float

   minver:  4

   definition:  White Y chromaticity coordinate, as defined by CIE 1931.

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9.4.1.36.19.23.  LuminanceMax Element

   name:  LuminanceMax

   path:  "\Segment\Tracks\TrackEntry\Video\Colour\MasteringMetadata\Lum
      inanceMax"

   id:  0x55D9

   maxOccurs:  1

   range:  >= 0x0p+0

   type:  float

   minver:  4

   definition:  Maximum luminance.  Represented in candelas per square
      meter (cd/m^(2)).

9.4.1.36.19.24.  LuminanceMin Element

   name:  LuminanceMin

   path:  "\Segment\Tracks\TrackEntry\Video\Colour\MasteringMetadata\Lum
      inanceMin"

   id:  0x55DA

   maxOccurs:  1

   range:  >= 0x0p+0

   type:  float

   minver:  4

   definition:  Minimum luminance.  Represented in candelas per square
      meter (cd/m^(2)).

9.4.1.36.20.  Projection Element

   name:  Projection

   path:  "\Segment\Tracks\TrackEntry\Video\Projection"

   id:  0x7670

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   maxOccurs:  1

   type:  master

   minver:  4

   definition:  Describes the video projection details.  Used to render
      spherical and VR videos.

9.4.1.36.20.1.  ProjectionType Element

   name:  ProjectionType

   path:  "\Segment\Tracks\TrackEntry\Video\Projection\ProjectionType"

   id:  0x7671

   minOccurs:  1

   maxOccurs:  1

   range:  0-3

   default:  0

   type:  uinteger

   minver:  4

   definition:  Describes the projection used for this video track.

   restrictions:

                        +=======+=================+
                        | value | label           |
                        +=======+=================+
                        | 0     | rectangular     |
                        +-------+-----------------+
                        | 1     | equirectangular |
                        +-------+-----------------+
                        | 2     | cubemap         |
                        +-------+-----------------+
                        | 3     | mesh            |
                        +-------+-----------------+

                                  Table 28

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9.4.1.36.20.2.  ProjectionPrivate Element

   name:  ProjectionPrivate

   path:  "\Segment\Tracks\TrackEntry\Video\Projection\ProjectionPrivate
      "

   id:  0x7672

   maxOccurs:  1

   type:  binary

   minver:  4

   definition:  Private data that only applies to a specific projection.

   *  If "ProjectionType" equals 0 (Rectangular), then this element must
      not be present.

   *  If "ProjectionType" equals 1 (Equirectangular), then this element
      must be present and contain the same binary data that would be
      stored inside an ISOBMFF Equirectangular Projection Box ('equi').

   *  If "ProjectionType" equals 2 (Cubemap), then this element must be
      present and contain the same binary data that would be stored
      inside an ISOBMFF Cubemap Projection Box ('cbmp').

   *  If "ProjectionType" equals 3 (Mesh), then this element must be
      present and contain the same binary data that would be stored
      inside an ISOBMFF Mesh Projection Box ('mshp').

   usage notes:  ISOBMFF box size and fourcc fields are not included in
      the binary data, but the FullBox version and flag fields are.
      This is to avoid redundant framing information while preserving
      versioning and semantics between the two container formats.

9.4.1.36.20.3.  ProjectionPoseYaw Element

   name:  ProjectionPoseYaw

   path:  "\Segment\Tracks\TrackEntry\Video\Projection\ProjectionPoseYaw
      "

   id:  0x7673

   minOccurs:  1

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   maxOccurs:  1

   default:  0x0p+0

   type:  float

   minver:  4

   definition:  Specifies a yaw rotation to the projection.

   Value represents a clockwise rotation, in degrees, around the up
   vector.  This rotation must be applied before any
   "ProjectionPosePitch" or "ProjectionPoseRoll" rotations.  The value
   of this field should be in the -180 to 180 degree range.

9.4.1.36.20.4.  ProjectionPosePitch Element

   name:  ProjectionPosePitch

   path:  "\Segment\Tracks\TrackEntry\Video\Projection\ProjectionPosePit
      ch"

   id:  0x7674

   minOccurs:  1

   maxOccurs:  1

   default:  0x0p+0

   type:  float

   minver:  4

   definition:  Specifies a pitch rotation to the projection.

   Value represents a counter-clockwise rotation, in degrees, around the
   right vector.  This rotation must be applied after the
   "ProjectionPoseYaw" rotation and before the "ProjectionPoseRoll"
   rotation.  The value of this field should be in the -90 to 90 degree
   range.

9.4.1.36.20.5.  ProjectionPoseRoll Element

   name:  ProjectionPoseRoll

   path:  "\Segment\Tracks\TrackEntry\Video\Projection\ProjectionPoseRol
      l"

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   id:  0x7675

   minOccurs:  1

   maxOccurs:  1

   default:  0x0p+0

   type:  float

   minver:  4

   definition:  Specifies a roll rotation to the projection.

   Value represents a counter-clockwise rotation, in degrees, around the
   forward vector.  This rotation must be applied after the
   "ProjectionPoseYaw" and "ProjectionPosePitch" rotations.  The value
   of this field should be in the -180 to 180 degree range.

9.4.1.37.  Audio Element

   name:  Audio

   path:  "\Segment\Tracks\TrackEntry\Audio"

   id:  0xE1

   maxOccurs:  1

   type:  master

   definition:  Audio settings.

9.4.1.37.1.  SamplingFrequency Element

   name:  SamplingFrequency

   path:  "\Segment\Tracks\TrackEntry\Audio\SamplingFrequency"

   id:  0xB5

   minOccurs:  1

   maxOccurs:  1

   range:  > 0x0p+0

   default:  0x1.f4p+12

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   type:  float

   definition:  Sampling frequency in Hz.

9.4.1.37.2.  OutputSamplingFrequency Element

   name:  OutputSamplingFrequency

   path:  "\Segment\Tracks\TrackEntry\Audio\OutputSamplingFrequency"

   id:  0x78B5

   maxOccurs:  1

   range:  > 0x0p+0

   default: see implementation notes

   type:  float

   definition:  Real output sampling frequency in Hz (used for SBR
      techniques).

   implementation notes:

   +===========+======================================================+
   | attribute | note                                                 |
   +===========+======================================================+
   | default   | The default value for OutputSamplingFrequency of the |
   |           | same TrackEntry is equal to the SamplingFrequency.   |
   +-----------+------------------------------------------------------+

                                 Table 29

9.4.1.37.3.  Channels Element

   name:  Channels

   path:  "\Segment\Tracks\TrackEntry\Audio\Channels"

   id:  0x9F

   minOccurs:  1

   maxOccurs:  1

   range:  not 0

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   default:  1

   type:  uinteger

   definition:  Numbers of channels in the track.

9.4.1.37.4.  ChannelPositions Element

   name:  ChannelPositions

   path:  "\Segment\Tracks\TrackEntry\Audio\ChannelPositions"

   id:  0x7D7B

   maxOccurs:  1

   type:  binary

   minver:  0

   maxver:  0

   definition:  Table of horizontal angles for each successive channel.

9.4.1.37.5.  BitDepth Element

   name:  BitDepth

   path:  "\Segment\Tracks\TrackEntry\Audio\BitDepth"

   id:  0x6264

   maxOccurs:  1

   range:  not 0

   type:  uinteger

   definition:  Bits per sample, mostly used for PCM.

9.4.1.38.  TrackOperation Element

   name:  TrackOperation

   path:  "\Segment\Tracks\TrackEntry\TrackOperation"

   id:  0xE2

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   maxOccurs:  1

   type:  master

   minver:  3

   definition:  Operation that needs to be applied on tracks to create
      this virtual track.  For more details look at Section 24.8.

9.4.1.38.1.  TrackCombinePlanes Element

   name:  TrackCombinePlanes

   path:  "\Segment\Tracks\TrackEntry\TrackOperation\TrackCombinePlanes"

   id:  0xE3

   maxOccurs:  1

   type:  master

   minver:  3

   definition:  Contains the list of all video plane tracks that need to
      be combined to create this 3D track

9.4.1.38.1.1.  TrackPlane Element

   name:  TrackPlane

   path:  "\Segment\Tracks\TrackEntry\TrackOperation\TrackCombinePlanes\
      TrackPlane"

   id:  0xE4

   minOccurs:  1

   type:  master

   minver:  3

   definition:  Contains a video plane track that need to be combined to
      create this 3D track

9.4.1.38.1.2.  TrackPlaneUID Element

   name:  TrackPlaneUID

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   path:  "\Segment\Tracks\TrackEntry\TrackOperation\TrackCombinePlanes\
      TrackPlane\TrackPlaneUID"

   id:  0xE5

   minOccurs:  1

   maxOccurs:  1

   range:  not 0

   type:  uinteger

   minver:  3

   definition:  The trackUID number of the track representing the plane.

9.4.1.38.1.3.  TrackPlaneType Element

   name:  TrackPlaneType

   path:  "\Segment\Tracks\TrackEntry\TrackOperation\TrackCombinePlanes\
      TrackPlane\TrackPlaneType"

   id:  0xE6

   minOccurs:  1

   maxOccurs:  1

   type:  uinteger

   minver:  3

   definition:  The kind of plane this track corresponds to.

   restrictions:

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                          +=======+============+
                          | value | label      |
                          +=======+============+
                          | 0     | left eye   |
                          +-------+------------+
                          | 1     | right eye  |
                          +-------+------------+
                          | 2     | background |
                          +-------+------------+

                                 Table 30

9.4.1.38.2.  TrackJoinBlocks Element

   name:  TrackJoinBlocks

   path:  "\Segment\Tracks\TrackEntry\TrackOperation\TrackJoinBlocks"

   id:  0xE9

   maxOccurs:  1

   type:  master

   minver:  3

   definition:  Contains the list of all tracks whose Blocks need to be
      combined to create this virtual track

9.4.1.38.2.1.  TrackJoinUID Element

   name:  TrackJoinUID

   path:  "\Segment\Tracks\TrackEntry\TrackOperation\TrackJoinBlocks\Tra
      ckJoinUID"

   id:  0xED

   minOccurs:  1

   range:  not 0

   type:  uinteger

   minver:  3

   definition:  The trackUID number of a track whose blocks are used to
      create this virtual track.

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9.4.1.39.  TrickTrackUID Element

   name:  TrickTrackUID

   path:  "\Segment\Tracks\TrackEntry\TrickTrackUID"

   id:  0xC0

   maxOccurs:  1

   type:  uinteger

   minver:  0

   maxver:  0

   definition:  The TrackUID of the Smooth FF/RW video in the paired
      EBML structure corresponding to this video track.  See
      [DivXTrickTrack].

9.4.1.40.  TrickTrackSegmentUID Element

   name:  TrickTrackSegmentUID

   path:  "\Segment\Tracks\TrackEntry\TrickTrackSegmentUID"

   id:  0xC1

   maxOccurs:  1

   type:  binary

   minver:  0

   maxver:  0

   definition:  The SegmentUID of the Segment containing the track
      identified by TrickTrackUID.  See [DivXTrickTrack].

9.4.1.41.  TrickTrackFlag Element

   name:  TrickTrackFlag

   path:  "\Segment\Tracks\TrackEntry\TrickTrackFlag"

   id:  0xC6

   maxOccurs:  1

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   default:  0

   type:  uinteger

   minver:  0

   maxver:  0

   definition:  Set to 1 if this video track is a Smooth FF/RW track.
      If set to 1, MasterTrackUID and MasterTrackSegUID should must be
      present and BlockGroups for this track must contain ReferenceFrame
      structures.  Otherwise, TrickTrackUID and TrickTrackSegUID must be
      present if this track has a corresponding Smooth FF/RW track.  See
      [DivXTrickTrack].

9.4.1.42.  TrickMasterTrackUID Element

   name:  TrickMasterTrackUID

   path:  "\Segment\Tracks\TrackEntry\TrickMasterTrackUID"

   id:  0xC7

   maxOccurs:  1

   type:  uinteger

   minver:  0

   maxver:  0

   definition:  The TrackUID of the video track in the paired EBML
      structure that corresponds to this Smooth FF/RW track.  See
      [DivXTrickTrack].

9.4.1.43.  TrickMasterTrackSegmentUID Element

   name:  TrickMasterTrackSegmentUID

   path:  "\Segment\Tracks\TrackEntry\TrickMasterTrackSegmentUID"

   id:  0xC4

   maxOccurs:  1

   type:  binary

   minver:  0

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   maxver:  0

   definition:  The SegmentUID of the Segment containing the track
      identified by MasterTrackUID.  See [DivXTrickTrack].

9.4.1.44.  ContentEncodings Element

   name:  ContentEncodings

   path:  "\Segment\Tracks\TrackEntry\ContentEncodings"

   id:  0x6D80

   maxOccurs:  1

   type:  master

   definition:  Settings for several content encoding mechanisms like
      compression or encryption.

9.4.1.44.1.  ContentEncoding Element

   name:  ContentEncoding

   path:  "\Segment\Tracks\TrackEntry\ContentEncodings\ContentEncoding"

   id:  0x6240

   minOccurs:  1

   type:  master

   definition:  Settings for one content encoding like compression or
      encryption.

9.4.1.44.1.1.  ContentEncodingOrder Element

   name:  ContentEncodingOrder

   path:  "\Segment\Tracks\TrackEntry\ContentEncodings\ContentEncoding\C
      ontentEncodingOrder"

   id:  0x5031

   minOccurs:  1

   maxOccurs:  1

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   default:  0

   type:  uinteger

   definition:  Tells when this modification was used during encoding/
      muxing starting with 0 and counting upwards.  The decoder/demuxer
      has to start with the highest order number it finds and work its
      way down.  This value has to be unique over all
      ContentEncodingOrder Elements in the TrackEntry that contains this
      ContentEncodingOrder element.

9.4.1.44.1.2.  ContentEncodingScope Element

   name:  ContentEncodingScope

   path:  "\Segment\Tracks\TrackEntry\ContentEncodings\ContentEncoding\C
      ontentEncodingScope"

   id:  0x5032

   minOccurs:  1

   maxOccurs:  1

   range:  not 0

   default:  1

   type:  uinteger

   definition:  A bit field that describes which Elements have been
      modified in this way.  Values (big-endian) can be OR'ed.

   restrictions:

       +=======+==================================================+
       | value | label                                            |
       +=======+==================================================+
       | 1     | All frame contents, excluding lacing data        |
       +-------+--------------------------------------------------+
       | 2     | The track's private data                         |
       +-------+--------------------------------------------------+
       | 4     | The next ContentEncoding (next                   |
       |       | "ContentEncodingOrder".  Either the data inside  |
       |       | "ContentCompression" and/or "ContentEncryption") |
       +-------+--------------------------------------------------+

                                 Table 31

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9.4.1.44.1.3.  ContentEncodingType Element

   name:  ContentEncodingType

   path:  "\Segment\Tracks\TrackEntry\ContentEncodings\ContentEncoding\C
      ontentEncodingType"

   id:  0x5033

   minOccurs:  1

   maxOccurs:  1

   default:  0

   type:  uinteger

   definition:  A value describing what kind of transformation is
      applied.

   restrictions:

                          +=======+=============+
                          | value | label       |
                          +=======+=============+
                          | 0     | Compression |
                          +-------+-------------+
                          | 1     | Encryption  |
                          +-------+-------------+

                                  Table 32

9.4.1.44.1.4.  ContentCompression Element

   name:  ContentCompression

   path:  "\Segment\Tracks\TrackEntry\ContentEncodings\ContentEncoding\C
      ontentCompression"

   id:  0x5034

   maxOccurs:  1

   type:  master

   definition:  Settings describing the compression used.  This Element

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      MUST be present if the value of ContentEncodingType is 0 and
      absent otherwise.  Each block MUST be decompressable even if no
      previous block is available in order not to prevent seeking.

9.4.1.44.1.5.  ContentCompAlgo Element

   name:  ContentCompAlgo

   path:  "\Segment\Tracks\TrackEntry\ContentEncodings\ContentEncoding\C
      ontentCompression\ContentCompAlgo"

   id:  0x4254

   minOccurs:  1

   maxOccurs:  1

   default:  0

   type:  uinteger

   definition:  The compression algorithm used.

   restrictions:

                       +=======+==================+
                       | value | label            |
                       +=======+==================+
                       | 0     | zlib             |
                       +-------+------------------+
                       | 1     | bzlib            |
                       +-------+------------------+
                       | 2     | lzo1x            |
                       +-------+------------------+
                       | 3     | Header Stripping |
                       +-------+------------------+

                                 Table 33

9.4.1.44.1.6.  ContentCompSettings Element

   name:  ContentCompSettings

   path:  "\Segment\Tracks\TrackEntry\ContentEncodings\ContentEncoding\C
      ontentCompression\ContentCompSettings"

   id:  0x4255

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   maxOccurs:  1

   type:  binary

   definition:  Settings that might be needed by the decompressor.  For
      Header Stripping ("ContentCompAlgo"=3), the bytes that were
      removed from the beginning of each frames of the track.

9.4.1.44.1.7.  ContentEncryption Element

   name:  ContentEncryption

   path:  "\Segment\Tracks\TrackEntry\ContentEncodings\ContentEncoding\C
      ontentEncryption"

   id:  0x5035

   maxOccurs:  1

   type:  master

   definition:  Settings describing the encryption used.  This Element
      MUST be present if the value of "ContentEncodingType" is 1
      (encryption) and MUST be ignored otherwise.

9.4.1.44.1.8.  ContentEncAlgo Element

   name:  ContentEncAlgo

   path:  "\Segment\Tracks\TrackEntry\ContentEncodings\ContentEncoding\C
      ontentEncryption\ContentEncAlgo"

   id:  0x47E1

   minOccurs:  1

   maxOccurs:  1

   default:  0

   type:  uinteger

   definition:  The encryption algorithm used.  The value "0" means that
      the contents have not been encrypted but only signed.

   restrictions:

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                     +=======+=======================+
                     | value | label                 |
                     +=======+=======================+
                     | 0     | Not encrypted         |
                     +-------+-----------------------+
                     | 1     | DES - FIPS 46-3       |
                     +-------+-----------------------+
                     | 2     | Triple DES - RFC 1851 |
                     +-------+-----------------------+
                     | 3     | Twofish               |
                     +-------+-----------------------+
                     | 4     | Blowfish              |
                     +-------+-----------------------+
                     | 5     | AES - FIPS 187        |
                     +-------+-----------------------+

                                  Table 34

9.4.1.44.1.9.  ContentEncKeyID Element

   name:  ContentEncKeyID

   path:  "\Segment\Tracks\TrackEntry\ContentEncodings\ContentEncoding\C
      ontentEncryption\ContentEncKeyID"

   id:  0x47E2

   maxOccurs:  1

   type:  binary

   definition:  For public key algorithms this is the ID of the public
      key the the data was encrypted with.

9.4.1.44.1.10.  ContentEncAESSettings Element

   name:  ContentEncAESSettings

   path:  "\Segment\Tracks\TrackEntry\ContentEncodings\ContentEncoding\C
      ontentEncryption\ContentEncAESSettings"

   id:  0x47E7

   maxOccurs:  1

   type:  master

   minver:  4

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   definition:  Settings describing the encryption algorithm used.  If
      "ContentEncAlgo" != 5 this MUST be ignored.

9.4.1.44.1.11.  AESSettingsCipherMode Element

   name:  AESSettingsCipherMode

   path:  "\Segment\Tracks\TrackEntry\ContentEncodings\ContentEncoding\C
      ontentEncryption\ContentEncAESSettings\AESSettingsCipherMode"

   id:  0x47E8

   minOccurs:  1

   maxOccurs:  1

   type:  uinteger

   minver:  4

   definition:  The AES cipher mode used in the encryption.

   restrictions:

       +=======+==================================================+
       | value | label                                            |
       +=======+==================================================+
       | 1     | AES-CTR / Counter, NIST SP 800-38A               |
       +-------+--------------------------------------------------+
       | 2     | AES-CBC / Cipher Block Chaining, NIST SP 800-38A |
       +-------+--------------------------------------------------+

                                 Table 35

9.4.1.44.1.12.  ContentSignature Element

   name:  ContentSignature

   path:  "\Segment\Tracks\TrackEntry\ContentEncodings\ContentEncoding\C
      ontentEncryption\ContentSignature"

   id:  0x47E3

   maxOccurs:  1

   type:  binary

   definition:  A cryptographic signature of the contents.

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9.4.1.44.1.13.  ContentSigKeyID Element

   name:  ContentSigKeyID

   path:  "\Segment\Tracks\TrackEntry\ContentEncodings\ContentEncoding\C
      ontentEncryption\ContentSigKeyID"

   id:  0x47E4

   maxOccurs:  1

   type:  binary

   definition:  This is the ID of the private key the data was signed
      with.

9.4.1.44.1.14.  ContentSigAlgo Element

   name:  ContentSigAlgo

   path:  "\Segment\Tracks\TrackEntry\ContentEncodings\ContentEncoding\C
      ontentEncryption\ContentSigAlgo"

   id:  0x47E5

   maxOccurs:  1

   default:  0

   type:  uinteger

   definition:  The algorithm used for the signature.

   restrictions:

                          +=======+============+
                          | value | label      |
                          +=======+============+
                          | 0     | Not signed |
                          +-------+------------+
                          | 1     | RSA        |
                          +-------+------------+

                                 Table 36

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9.4.1.44.1.15.  ContentSigHashAlgo Element

   name:  ContentSigHashAlgo

   path:  "\Segment\Tracks\TrackEntry\ContentEncodings\ContentEncoding\C
      ontentEncryption\ContentSigHashAlgo"

   id:  0x47E6

   maxOccurs:  1

   default:  0

   type:  uinteger

   definition:  The hash algorithm used for the signature.

   restrictions:

                          +=======+============+
                          | value | label      |
                          +=======+============+
                          | 0     | Not signed |
                          +-------+------------+
                          | 1     | SHA1-160   |
                          +-------+------------+
                          | 2     | MD5        |
                          +-------+------------+

                                 Table 37

9.5.  Cues Element

   name:  Cues

   path:  "\Segment\Cues"

   id:  0x1C53BB6B

   minOccurs: see implementation notes

   maxOccurs:  1

   type:  master

   definition:  A Top-Level Element to speed seeking access.  All
      entries are local to the Segment.

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   implementation notes:

    +===========+====================================================+
    | attribute | note                                               |
    +===========+====================================================+
    | minOccurs | This Element SHOULD be set when the Segment is not |
    |           | transmitted as a live stream (see #livestreaming). |
    +-----------+----------------------------------------------------+

                                 Table 38

9.5.1.  CuePoint Element

   name:  CuePoint

   path:  "\Segment\Cues\CuePoint"

   id:  0xBB

   minOccurs:  1

   type:  master

   definition:  Contains all information relative to a seek point in the
      Segment.

9.5.1.1.  CueTime Element

   name:  CueTime

   path:  "\Segment\Cues\CuePoint\CueTime"

   id:  0xB3

   minOccurs:  1

   maxOccurs:  1

   type:  uinteger

   definition:  Absolute timestamp according to the Segment time base.

9.5.1.2.  CueTrackPositions Element

   name:  CueTrackPositions

   path:  "\Segment\Cues\CuePoint\CueTrackPositions"

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   id:  0xB7

   minOccurs:  1

   type:  master

   definition:  Contain positions for different tracks corresponding to
      the timestamp.

9.5.1.2.1.  CueTrack Element

   name:  CueTrack

   path:  "\Segment\Cues\CuePoint\CueTrackPositions\CueTrack"

   id:  0xF7

   minOccurs:  1

   maxOccurs:  1

   range:  not 0

   type:  uinteger

   definition:  The track for which a position is given.

9.5.1.2.2.  CueClusterPosition Element

   name:  CueClusterPosition

   path:  "\Segment\Cues\CuePoint\CueTrackPositions\CueClusterPosition"

   id:  0xF1

   minOccurs:  1

   maxOccurs:  1

   type:  uinteger

   definition:  The Segment Position of the Cluster containing the
      associated Block.

9.5.1.2.3.  CueRelativePosition Element

   name:  CueRelativePosition

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   path:  "\Segment\Cues\CuePoint\CueTrackPositions\CueRelativePosition"

   id:  0xF0

   maxOccurs:  1

   type:  uinteger

   minver:  4

   definition:  The relative position inside the Cluster of the
      referenced SimpleBlock or BlockGroup with 0 being the first
      possible position for an Element inside that Cluster.

9.5.1.2.4.  CueDuration Element

   name:  CueDuration

   path:  "\Segment\Cues\CuePoint\CueTrackPositions\CueDuration"

   id:  0xB2

   maxOccurs:  1

   type:  uinteger

   minver:  4

   definition:  The duration of the block according to the Segment time
      base.  If missing the track's DefaultDuration does not apply and
      no duration information is available in terms of the cues.

9.5.1.2.5.  CueBlockNumber Element

   name:  CueBlockNumber

   path:  "\Segment\Cues\CuePoint\CueTrackPositions\CueBlockNumber"

   id:  0x5378

   maxOccurs:  1

   range:  not 0

   default:  1

   type:  uinteger

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   definition:  Number of the Block in the specified Cluster.

9.5.1.2.6.  CueCodecState Element

   name:  CueCodecState

   path:  "\Segment\Cues\CuePoint\CueTrackPositions\CueCodecState"

   id:  0xEA

   maxOccurs:  1

   default:  0

   type:  uinteger

   minver:  2

   definition:  The Segment Position of the Codec State corresponding to
      this Cue Element. 0 means that the data is taken from the initial
      Track Entry.

9.5.1.2.7.  CueReference Element

   name:  CueReference

   path:  "\Segment\Cues\CuePoint\CueTrackPositions\CueReference"

   id:  0xDB

   type:  master

   minver:  2

   definition:  The Clusters containing the referenced Blocks.

9.5.1.2.7.1.  CueRefTime Element

   name:  CueRefTime

   path:  "\Segment\Cues\CuePoint\CueTrackPositions\CueReference\CueRefT
      ime"

   id:  0x96

   minOccurs:  1

   maxOccurs:  1

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   type:  uinteger

   minver:  2

   definition:  Timestamp of the referenced Block.

9.5.1.2.7.2.  CueRefCluster Element

   name:  CueRefCluster

   path:  "\Segment\Cues\CuePoint\CueTrackPositions\CueReference\CueRefC
      luster"

   id:  0x97

   minOccurs:  1

   maxOccurs:  1

   type:  uinteger

   minver:  0

   maxver:  0

   definition:  The Segment Position of the Cluster containing the
      referenced Block.

9.5.1.2.7.3.  CueRefNumber Element

   name:  CueRefNumber

   path:  "\Segment\Cues\CuePoint\CueTrackPositions\CueReference\CueRefN
      umber"

   id:  0x535F

   maxOccurs:  1

   range:  not 0

   default:  1

   type:  uinteger

   minver:  0

   maxver:  0

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   definition:  Number of the referenced Block of Track X in the
      specified Cluster.

9.5.1.2.7.4.  CueRefCodecState Element

   name:  CueRefCodecState

   path:  "\Segment\Cues\CuePoint\CueTrackPositions\CueReference\CueRefC
      odecState"

   id:  0xEB

   maxOccurs:  1

   default:  0

   type:  uinteger

   minver:  0

   maxver:  0

   definition:  The Segment Position of the Codec State corresponding to
      this referenced Element. 0 means that the data is taken from the
      initial Track Entry.

9.6.  Attachments Element

   name:  Attachments

   path:  "\Segment\Attachments"

   id:  0x1941A469

   maxOccurs:  1

   type:  master

   definition:  Contain attached files.

9.6.1.  AttachedFile Element

   name:  AttachedFile

   path:  "\Segment\Attachments\AttachedFile"

   id:  0x61A7

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   minOccurs:  1

   type:  master

   definition:  An attached file.

9.6.1.1.  FileDescription Element

   name:  FileDescription

   path:  "\Segment\Attachments\AttachedFile\FileDescription"

   id:  0x467E

   maxOccurs:  1

   type:  utf-8

   definition:  A human-friendly name for the attached file.

9.6.1.2.  FileName Element

   name:  FileName

   path:  "\Segment\Attachments\AttachedFile\FileName"

   id:  0x466E

   minOccurs:  1

   maxOccurs:  1

   type:  utf-8

   definition:  Filename of the attached file.

9.6.1.3.  FileMimeType Element

   name:  FileMimeType

   path:  "\Segment\Attachments\AttachedFile\FileMimeType"

   id:  0x4660

   minOccurs:  1

   maxOccurs:  1

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   type:  string

   definition:  MIME type of the file.

9.6.1.4.  FileData Element

   name:  FileData

   path:  "\Segment\Attachments\AttachedFile\FileData"

   id:  0x465C

   minOccurs:  1

   maxOccurs:  1

   type:  binary

   definition:  The data of the file.

9.6.1.5.  FileUID Element

   name:  FileUID

   path:  "\Segment\Attachments\AttachedFile\FileUID"

   id:  0x46AE

   minOccurs:  1

   maxOccurs:  1

   range:  not 0

   type:  uinteger

   definition:  Unique ID representing the file, as random as possible.

9.6.1.6.  FileReferral Element

   name:  FileReferral

   path:  "\Segment\Attachments\AttachedFile\FileReferral"

   id:  0x4675

   maxOccurs:  1

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   type:  binary

   minver:  0

   maxver:  0

   definition:  A binary value that a track/codec can refer to when the
      attachment is needed.

9.6.1.7.  FileUsedStartTime Element

   name:  FileUsedStartTime

   path:  "\Segment\Attachments\AttachedFile\FileUsedStartTime"

   id:  0x4661

   maxOccurs:  1

   type:  uinteger

   minver:  0

   maxver:  0

   definition:  The timecode at which this optimized font attachment
      comes into context, based on the Segment TimecodeScale.  This
      element is reserved for future use and if written must be the
      segment start time.  See [DivXWorldFonts].

9.6.1.8.  FileUsedEndTime Element

   name:  FileUsedEndTime

   path:  "\Segment\Attachments\AttachedFile\FileUsedEndTime"

   id:  0x4662

   maxOccurs:  1

   type:  uinteger

   minver:  0

   maxver:  0

   definition:  The timecode at which this optimized font attachment

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      goes out of context, based on the Segment TimecodeScale.  This
      element is reserved for future use and if written must be the
      segment end time.  See [DivXWorldFonts].

9.7.  Chapters Element

   name:  Chapters

   path:  "\Segment\Chapters"

   id:  0x1043A770

   maxOccurs:  1

   type:  master

   recurring:  1

   definition:  A system to define basic menus and partition data.  For
      more detailed information, look at the Chapters explanation in
      Section 11.

9.7.1.  EditionEntry Element

   name:  EditionEntry

   path:  "\Segment\Chapters\EditionEntry"

   id:  0x45B9

   minOccurs:  1

   type:  master

   definition:  Contains all information about a Segment edition.

9.7.1.1.  EditionUID Element

   name:  EditionUID

   path:  "\Segment\Chapters\EditionEntry\EditionUID"

   id:  0x45BC

   maxOccurs:  1

   range:  not 0

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   type:  uinteger

   definition:  A unique ID to identify the edition.  It's useful for
      tagging an edition.

9.7.1.2.  EditionFlagDefault Element

   name:  EditionFlagDefault

   path:  "\Segment\Chapters\EditionEntry\EditionFlagDefault"

   id:  0x45DB

   minOccurs:  1

   maxOccurs:  1

   range:  0-1

   default:  0

   type:  uinteger

   definition:  Set to 1 if the edition SHOULD be used as the default
      one.

9.7.1.3.  EditionFlagOrdered Element

   name:  EditionFlagOrdered

   path:  "\Segment\Chapters\EditionEntry\EditionFlagOrdered"

   id:  0x45DD

   maxOccurs:  1

   range:  0-1

   default:  0

   type:  uinteger

   definition:  Specify if the chapters can be defined multiple times
      and the order to play them is enforced.

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9.7.1.4.  ChapterAtom Element

   name:  ChapterAtom

   path:  "\Segment\Chapters\EditionEntry\+ChapterAtom"

   id:  0xB6

   minOccurs:  1

   type:  master

   recursive:  1

   definition:  Contains the atom information to use as the chapter atom
      (apply to all tracks).

9.7.1.4.1.  ChapterUID Element

   name:  ChapterUID

   path:  "\Segment\Chapters\EditionEntry\+ChapterAtom\ChapterUID"

   id:  0x73C4

   minOccurs:  1

   maxOccurs:  1

   range:  not 0

   type:  uinteger

   definition:  A unique ID to identify the Chapter.

9.7.1.4.2.  ChapterStringUID Element

   name:  ChapterStringUID

   path:  "\Segment\Chapters\EditionEntry\+ChapterAtom\ChapterStringUID"

   id:  0x5654

   maxOccurs:  1

   type:  utf-8

   minver:  3

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   definition:  A unique string ID to identify the Chapter.  Use for
      WebVTT cue identifier storage [WebVTT].

9.7.1.4.3.  ChapterTimeStart Element

   name:  ChapterTimeStart

   path:  "\Segment\Chapters\EditionEntry\+ChapterAtom\ChapterTimeStart"

   id:  0x91

   minOccurs:  1

   maxOccurs:  1

   type:  uinteger

   definition:  Timestamp of the start of Chapter (not scaled).

9.7.1.4.4.  ChapterTimeEnd Element

   name:  ChapterTimeEnd

   path:  "\Segment\Chapters\EditionEntry\+ChapterAtom\ChapterTimeEnd"

   id:  0x92

   maxOccurs:  1

   type:  uinteger

   definition:  Timestamp of the end of Chapter (timestamp excluded, not
      scaled).  The value MUST be strictly greater than the
      "ChapterTimeStart" of the same "ChapterAtom".

9.7.1.4.5.  ChapterFlagHidden Element

   name:  ChapterFlagHidden

   path:  "\Segment\Chapters\EditionEntry\+ChapterAtom\ChapterFlagHidden
      "

   id:  0x98

   minOccurs:  1

   maxOccurs:  1

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   range:  0-1

   default:  0

   type:  uinteger

   definition:  Set to 1 if a chapter is hidden.  Hidden chapters it
      SHOULD NOT be available to the user interface (but still to
      Control Tracks; see Section 11.2.3 on Chapter flags).

9.7.1.4.6.  ChapterSegmentUID Element

   name:  ChapterSegmentUID

   path:  "\Segment\Chapters\EditionEntry\+ChapterAtom\ChapterSegmentUID
      "

   id:  0x6E67

   minOccurs: see implementation notes

   maxOccurs:  1

   range:  >0

   type:  binary

   definition:  The SegmentUID of another Segment to play during this
      chapter.

   implementation notes:

        +===========+=============================================+
        | attribute | note                                        |
        +===========+=============================================+
        | minOccurs | ChapterSegmentUID MUST be set (minOccurs=1) |
        |           | if ChapterSegmentEditionUID is used.        |
        +-----------+---------------------------------------------+

                                  Table 39

9.7.1.4.7.  ChapterSegmentEditionUID Element

   name:  ChapterSegmentEditionUID

   path:  "\Segment\Chapters\EditionEntry\+ChapterAtom\ChapterSegmentEdi
      tionUID"

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   id:  0x6EBC

   maxOccurs:  1

   range:  not 0

   type:  uinteger

   definition:  The EditionUID to play from the Segment linked in
      ChapterSegmentUID.  If ChapterSegmentEditionUID is undeclared,
      then no Edition of the linked Segment is used.

9.7.1.4.8.  ChapterPhysicalEquiv Element

   name:  ChapterPhysicalEquiv

   path:  "\Segment\Chapters\EditionEntry\+ChapterAtom\ChapterPhysicalEq
      uiv"

   id:  0x63C3

   maxOccurs:  1

   type:  uinteger

   definition:  Specify the physical equivalent of this ChapterAtom like
      "DVD" (60) or "SIDE" (50); see Section 6.2.2 for a complete list
      of values.

9.7.1.4.9.  ChapterDisplay Element

   name:  ChapterDisplay

   path:  "\Segment\Chapters\EditionEntry\+ChapterAtom\ChapterDisplay"

   id:  0x80

   type:  master

   definition:  Contains all possible strings to use for the chapter
      display.

9.7.1.4.9.1.  ChapString Element

   name:  ChapString

   path:  "\Segment\Chapters\EditionEntry\+ChapterAtom\ChapterDisplay\Ch
      apString"

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   id:  0x85

   minOccurs:  1

   maxOccurs:  1

   type:  utf-8

   definition:  Contains the string to use as the chapter atom.

9.7.1.4.9.2.  ChapLanguage Element

   name:  ChapLanguage

   path:  "\Segment\Chapters\EditionEntry\+ChapterAtom\ChapterDisplay\Ch
      apLanguage"

   id:  0x437C

   minOccurs:  1

   default:  eng

   type:  string

   definition:  The languages corresponding to the string, in the
      bibliographic ISO-639-2 form [ISO639-2].  This Element MUST be
      ignored if the ChapLanguageIETF Element is used within the same
      ChapterDisplay Element.

9.7.1.4.9.3.  ChapLanguageIETF Element

   name:  ChapLanguageIETF

   path:  "\Segment\Chapters\EditionEntry\+ChapterAtom\ChapterDisplay\Ch
      apLanguageIETF"

   id:  0x437D

   type:  string

   minver:  4

   definition:  Specifies the language used in the ChapString according
      to [BCP47] and using the IANA Language Subtag Registry
      [IANALangRegistry].  If this Element is used, then any
      ChapLanguage Elements used in the same ChapterDisplay MUST be
      ignored.

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9.7.1.4.9.4.  ChapCountry Element

   name:  ChapCountry

   path:  "\Segment\Chapters\EditionEntry\+ChapterAtom\ChapterDisplay\Ch
      apCountry"

   id:  0x437E

   type:  string

   definition:  The countries corresponding to the string, same 2 octets
      country-codes as in Internet domains [IANADomains] based on
      [ISO3166-1] alpha-2 codes.  This Element MUST be ignored if the
      ChapLanguageIETF Element is used within the same ChapterDisplay
      Element.

9.7.1.4.10.  ChapProcess Element

   name:  ChapProcess

   path:  "\Segment\Chapters\EditionEntry\+ChapterAtom\ChapProcess"

   id:  0x6944

   type:  master

   definition:  Contains all the commands associated to the Atom.

9.7.1.4.10.1.  ChapProcessCodecID Element

   name:  ChapProcessCodecID

   path:  "\Segment\Chapters\EditionEntry\+ChapterAtom\ChapProcess\ChapP
      rocessCodecID"

   id:  0x6955

   minOccurs:  1

   maxOccurs:  1

   default:  0

   type:  uinteger

   definition:  Contains the type of the codec used for the processing.

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      A value of 0 means native Matroska processing (to be defined), a
      value of 1 means the DVD command set is used; see Section 11.3 on
      DVD menus.  More codec IDs can be added later.

9.7.1.4.10.2.  ChapProcessPrivate Element

   name:  ChapProcessPrivate

   path:  "\Segment\Chapters\EditionEntry\+ChapterAtom\ChapProcess\ChapP
      rocessPrivate"

   id:  0x450D

   maxOccurs:  1

   type:  binary

   definition:  Some optional data attached to the ChapProcessCodecID
      information.  For ChapProcessCodecID = 1, it is the "DVD level"
      equivalent; see Section 11.3 on DVD menus.

9.7.1.4.10.3.  ChapProcessCommand Element

   name:  ChapProcessCommand

   path:  "\Segment\Chapters\EditionEntry\+ChapterAtom\ChapProcess\ChapP
      rocessCommand"

   id:  0x6911

   type:  master

   definition:  Contains all the commands associated to the Atom.

9.7.1.4.10.4.  ChapProcessTime Element

   name:  ChapProcessTime

   path:  "\Segment\Chapters\EditionEntry\+ChapterAtom\ChapProcess\ChapP
      rocessCommand\ChapProcessTime"

   id:  0x6922

   minOccurs:  1

   maxOccurs:  1

   type:  uinteger

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   definition:  Defines when the process command SHOULD be handled

   restrictions:

                 +=======+===============================+
                 | value | label                         |
                 +=======+===============================+
                 | 0     | during the whole chapter      |
                 +-------+-------------------------------+
                 | 1     | before starting playback      |
                 +-------+-------------------------------+
                 | 2     | after playback of the chapter |
                 +-------+-------------------------------+

                                  Table 40

9.7.1.4.10.5.  ChapProcessData Element

   name:  ChapProcessData

   path:  "\Segment\Chapters\EditionEntry\+ChapterAtom\ChapProcess\ChapP
      rocessCommand\ChapProcessData"

   id:  0x6933

   minOccurs:  1

   maxOccurs:  1

   type:  binary

   definition:  Contains the command information.  The data SHOULD be
      interpreted depending on the ChapProcessCodecID value.  For
      ChapProcessCodecID = 1, the data correspond to the binary DVD cell
      pre/post commands; see Section 11.3 on DVD menus.

9.8.  Tags Element

   name:  Tags

   path:  "\Segment\Tags"

   id:  0x1254C367

   type:  master

   definition:  Element containing metadata describing Tracks, Editions,

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      Chapters, Attachments, or the Segment as a whole.  A list of valid
      tags can be found in [I-D.ietf-cellar-tags].

9.8.1.  Tag Element

   name:  Tag

   path:  "\Segment\Tags\Tag"

   id:  0x7373

   minOccurs:  1

   type:  master

   definition:  A single metadata descriptor.

9.8.1.1.  Targets Element

   name:  Targets

   path:  "\Segment\Tags\Tag\Targets"

   id:  0x63C0

   minOccurs:  1

   maxOccurs:  1

   type:  master

   definition:  Specifies which other elements the metadata represented
      by the Tag applies to.  If empty or not present, then the Tag
      describes everything in the Segment.

9.8.1.1.1.  TargetTypeValue Element

   name:  TargetTypeValue

   path:  "\Segment\Tags\Tag\Targets\TargetTypeValue"

   id:  0x68CA

   maxOccurs:  1

   default:  50

   type:  uinteger

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   definition:  A number to indicate the logical level of the target.

   restrictions:

   +=======+==========================+================================+
   | value | label                    | documentation                  |
   +=======+==========================+================================+
   | 70    | COLLECTION               | The highest hierarchical level |
   |       |                          | that tags can describe.        |
   +-------+--------------------------+--------------------------------+
   | 60    | EDITION / ISSUE /        | A list of lower levels grouped |
   |       | VOLUME / OPUS /          | together.                      |
   |       | SEASON / SEQUEL          |                                |
   +-------+--------------------------+--------------------------------+
   | 50    | ALBUM / OPERA /          | The most common grouping level |
   |       | CONCERT / MOVIE /        | of music and video (equals to  |
   |       | EPISODE / CONCERT        | an episode for TV series).     |
   +-------+--------------------------+--------------------------------+
   | 40    | PART / SESSION           | When an album or episode has   |
   |       |                          | different logical parts.       |
   +-------+--------------------------+--------------------------------+
   | 30    | TRACK / SONG /           | The common parts of an album   |
   |       | CHAPTER                  | or movie.                      |
   +-------+--------------------------+--------------------------------+
   | 20    | SUBTRACK / PART /        | Corresponds to parts of a      |
   |       | MOVEMENT / SCENE         | track for audio (like a        |
   |       |                          | movement).                     |
   +-------+--------------------------+--------------------------------+
   | 10    | SHOT                     | The lowest hierarchy found in  |
   |       |                          | music or movies.               |
   +-------+--------------------------+--------------------------------+

                                  Table 41

9.8.1.1.2.  TargetType Element

   name:  TargetType

   path:  "\Segment\Tags\Tag\Targets\TargetType"

   id:  0x63CA

   maxOccurs:  1

   type:  string

   definition:  An informational string that can be used to display the

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      logical level of the target like "ALBUM", "TRACK", "MOVIE",
      "CHAPTER", etc ; see Section 6.4 of [I-D.ietf-cellar-tags].

   restrictions:

                        +============+============+
                        | value      | label      |
                        +============+============+
                        | COLLECTION | COLLECTION |
                        +------------+------------+
                        | EDITION    | EDITION    |
                        +------------+------------+
                        | ISSUE      | ISSUE      |
                        +------------+------------+
                        | VOLUME     | VOLUME     |
                        +------------+------------+
                        | OPUS       | OPUS       |
                        +------------+------------+
                        | SEASON     | SEASON     |
                        +------------+------------+
                        | SEQUEL     | SEQUEL     |
                        +------------+------------+
                        | ALBUM      | ALBUM      |
                        +------------+------------+
                        | OPERA      | OPERA      |
                        +------------+------------+
                        | CONCERT    | CONCERT    |
                        +------------+------------+
                        | MOVIE      | MOVIE      |
                        +------------+------------+
                        | EPISODE    | EPISODE    |
                        +------------+------------+
                        | PART       | PART       |
                        +------------+------------+
                        | SESSION    | SESSION    |
                        +------------+------------+
                        | TRACK      | TRACK      |
                        +------------+------------+
                        | SONG       | SONG       |
                        +------------+------------+
                        | CHAPTER    | CHAPTER    |
                        +------------+------------+
                        | SUBTRACK   | SUBTRACK   |
                        +------------+------------+
                        | PART       | PART       |
                        +------------+------------+
                        | MOVEMENT   | MOVEMENT   |
                        +------------+------------+

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                        | SCENE      | SCENE      |
                        +------------+------------+
                        | SHOT       | SHOT       |
                        +------------+------------+

                                  Table 42

9.8.1.1.3.  TagTrackUID Element

   name:  TagTrackUID

   path:  "\Segment\Tags\Tag\Targets\TagTrackUID"

   id:  0x63C5

   default:  0

   type:  uinteger

   definition:  A unique ID to identify the Track(s) the tags belong to.
      If the value is 0 at this level, the tags apply to all tracks in
      the Segment.

9.8.1.1.4.  TagEditionUID Element

   name:  TagEditionUID

   path:  "\Segment\Tags\Tag\Targets\TagEditionUID"

   id:  0x63C9

   default:  0

   type:  uinteger

   definition:  A unique ID to identify the EditionEntry(s) the tags
      belong to.  If the value is 0 at this level, the tags apply to all
      editions in the Segment.

9.8.1.1.5.  TagChapterUID Element

   name:  TagChapterUID

   path:  "\Segment\Tags\Tag\Targets\TagChapterUID"

   id:  0x63C4

   default:  0

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   type:  uinteger

   definition:  A unique ID to identify the Chapter(s) the tags belong
      to.  If the value is 0 at this level, the tags apply to all
      chapters in the Segment.

9.8.1.1.6.  TagAttachmentUID Element

   name:  TagAttachmentUID

   path:  "\Segment\Tags\Tag\Targets\TagAttachmentUID"

   id:  0x63C6

   default:  0

   type:  uinteger

   definition:  A unique ID to identify the Attachment(s) the tags
      belong to.  If the value is 0 at this level, the tags apply to all
      the attachments in the Segment.

9.8.1.2.  SimpleTag Element

   name:  SimpleTag

   path:  "\Segment\Tags\Tag\+SimpleTag"

   id:  0x67C8

   minOccurs:  1

   type:  master

   recursive:  1

   definition:  Contains general information about the target.

9.8.1.2.1.  TagName Element

   name:  TagName

   path:  "\Segment\Tags\Tag\+SimpleTag\TagName"

   id:  0x45A3

   minOccurs:  1

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   maxOccurs:  1

   type:  utf-8

   definition:  The name of the Tag that is going to be stored.

9.8.1.2.2.  TagLanguage Element

   name:  TagLanguage

   path:  "\Segment\Tags\Tag\+SimpleTag\TagLanguage"

   id:  0x447A

   minOccurs:  1

   maxOccurs:  1

   default:  und

   type:  string

   definition:  Specifies the language of the tag specified, in the
      Matroska languages form; see Section 6.2.1 on language codes.
      This Element MUST be ignored if the TagLanguageIETF Element is
      used within the same SimpleTag Element.

9.8.1.2.3.  TagLanguageIETF Element

   name:  TagLanguageIETF

   path:  "\Segment\Tags\Tag\+SimpleTag\TagLanguageIETF"

   id:  0x447B

   maxOccurs:  1

   type:  string

   minver:  4

   definition:  Specifies the language used in the TagString according
      to [BCP47] and using the IANA Language Subtag Registry
      [IANALangRegistry].  If this Element is used, then any TagLanguage
      Elements used in the same SimpleTag MUST be ignored.

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9.8.1.2.4.  TagDefault Element

   name:  TagDefault

   path:  "\Segment\Tags\Tag\+SimpleTag\TagDefault"

   id:  0x4484

   minOccurs:  1

   maxOccurs:  1

   range:  0-1

   default:  1

   type:  uinteger

   definition:  A boolean value to indicate if this is the default/
      original language to use for the given tag.

9.8.1.2.5.  TagString Element

   name:  TagString

   path:  "\Segment\Tags\Tag\+SimpleTag\TagString"

   id:  0x4487

   maxOccurs:  1

   type:  utf-8

   definition:  The value of the Tag.

9.8.1.2.6.  TagBinary Element

   name:  TagBinary

   path:  "\Segment\Tags\Tag\+SimpleTag\TagBinary"

   id:  0x4485

   maxOccurs:  1

   type:  binary

   definition:  The values of the Tag, if it is binary.  Note that this

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      cannot be used in the same SimpleTag as TagString.

10.  Matroska Element Ordering

   Except for the "EBML Header" and the "CRC-32 Element", the EBML
   specification does not require any particular storage order for
   "Elements".  The Matroska specification however defines mandates and
   recommendations for ordering certain "Elements" in order to
   facilitate better playback, seeking, and editing efficiency.  This
   section describes and offers rationale for ordering requirements and
   recommendations for Matroska.

10.1.  Top-Level Elements

   The "Info Element" is the only REQUIRED "Top-Level Element" in a
   Matroska file.  To be playable, Matroska MUST also contain at least
   one "Tracks Element" and "Cluster Element".  The first "Info Element"
   and the first "Tracks Element" MUST either be stored before the first
   "Cluster Element" or both SHALL be referenced by a "SeekHead Element"
   occurring before the first "Cluster Element".

   It is possible to edit a Matroska file after it has been created.
   For example, chapters, tags, or attachments can be added.  When new
   "Top-Level Elements" are added to a Matroska file, the "SeekHead"
   Element(s) MUST be updated so that the "SeekHead" Element(s) itemize
   the identity and position of all "Top-Level Elements".  Editing,
   removing, or adding "Elements" to a Matroska file often requires that
   some existing "Elements" be voided or extended; therefore, it is
   RECOMMENDED to use "Void Elements" as padding in between "Top-Level
   Elements".

10.2.  CRC-32

   As noted by the EBML specification, if a "CRC-32 Element" is used,
   then the "CRC-32 Element" MUST be the first ordered "Element" within
   its "Parent Element".  The Matroska specification recommends that
   "CRC-32 Elements" SHOULD NOT be used as an immediate "Child Element"
   of the "Segment Element"; however all "Top-Level Elements" of an
   "EBML Document" SHOULD include a "CRC-32 Element" as a "Child
   Element".

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10.3.  SeekHead

   If used, the first "SeekHead Element" SHOULD be the first non-"CRC-32
   Child Element" of the "Segment Element".  If a second "SeekHead
   Element" is used, then the first "SeekHead Element" MUST reference
   the identity and position of the second "SeekHead".  Additionally,
   the second "SeekHead Element" MUST only reference "Cluster" Elements
   and not any other "Top-Level Element" already contained within the
   first "SeekHead Element".  The second "SeekHead Element" MAY be
   stored in any order relative to the other "Top-Level Elements".
   Whether one or two "SeekHead Element(s)" are used, the "SeekHead
   Element(s)" MUST collectively reference the identity and position of
   all "Top-Level Elements" except for the first "SeekHead Element".

   It is RECOMMENDED that the first "SeekHead Element" be followed by a
   "Void Element" to allow for the "SeekHead Element" to be expanded to
   cover new "Top-Level Elements" that could be added to the Matroska
   file, such as "Tags", "Chapters", and "Attachments" Elements.

10.4.  Cues (index)

   The "Cues Element" is RECOMMENDED to optimize seeking access in
   Matroska.  It is programmatically simpler to add the "Cues Element"
   after all "Cluster Elements" have been written because this does not
   require a prediction of how much space to reserve before writing the
   "Cluster Elements".  However, storing the "Cues Element" before the
   "Cluster Elements" can provide some seeking advantages.  If the "Cues
   Element" is present, then it SHOULD either be stored before the first
   "Cluster Element" or be referenced by a "SeekHead Element".

10.5.  Info

   The first "Info Element" SHOULD occur before the first "Tracks
   Element" and first "Cluster Element" except when referenced by a
   "SeekHead Element".

10.6.  Chapters Element

   The "Chapters Element" SHOULD be placed before the "Cluster
   Element(s)".  The "Chapters Element" can be used during playback even
   if the user does not need to seek.  It immediately gives the user
   information about what section is being read and what other sections
   are available.  In the case of Ordered Chapters it is RECOMMENDED to
   evaluate the logical linking even before playing.  The "Chapters
   Element" SHOULD be placed before the first "Tracks Element" and after
   the first "Info Element".

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10.7.  Attachments

   The "Attachments Element" is not intended to be used by default when
   playing the file, but could contain information relevant to the
   content, such as cover art or fonts.  Cover art is useful even before
   the file is played and fonts could be needed before playback starts
   for initialization of subtitles.  The "Attachments Element" MAY be
   placed before the first "Cluster Element"; however if the
   "Attachments Element" is likely to be edited, then it SHOULD be
   placed after the last "Cluster Element".

10.8.  Tags

   The "Tags Element" is most subject to changes after the file was
   originally created.  For easier editing, the "Tags Element" SHOULD be
   placed at the end of the "Segment Element", even after the
   "Attachments Element".  On the other hand, it is inconvenient to have
   to seek in the "Segment" for tags, especially for network streams.
   So it's better if the "Tags Element" is found early in the stream.
   When editing the "Tags Element", the original "Tags Element" at the
   beginning can be overwritten with a "Void Element" and a new "Tags
   Element" written at the end of the "Segment Element".  The file size
   will only marginally change.

10.9.  Optimum layout from a muxer

   *  SeekHead

   *  Info

   *  Tracks

   *  Chapters

   *  Attachments

   *  Tags

   *  Clusters

   *  Cues

10.10.  Optimum layout after editing tags

   *  SeekHead

   *  Info

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   *  Tracks

   *  Chapters

   *  Attachments

   *  Void

   *  Clusters

   *  Cues

   *  Tags

10.11.  Optimum layout with Cues at the front

   *  SeekHead

   *  Info

   *  Tracks

   *  Chapters

   *  Attachments

   *  Tags

   *  Cues

   *  Clusters

10.12.  Cluster Timestamp

   The "Timestamp Element" MUST occur as in storage order before any
   "SimpleBlock", "BlockGroup", or "EncryptedBlock", within the "Cluster
   Element".

11.  Chapters

   The Matroska Chapters system can have multiple "Editions" and each
   "Edition" can consist of "Simple Chapters" where a chapter start time
   is used as marker in the timeline only.  An "Edition" can be more
   complex with "Ordered Chapters" where a chapter end time stamp is
   additionally used or much more complex with "Linked Chapters".  The
   Matroska Chapters system can also have a menu structure, borrowed
   from the DVD menu system, or have it's own Native Matroska menu
   structure.

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11.1.  EditionEntry

   The "EditionEntry" is also called an "Edition".  An "Edition"
   contains a set of "Edition" flags and MUST contain at least one
   "ChapterAtom Element".  Chapters are always inside an "Edition" (or a
   Chapter itself part of an "Edition").  Multiple Editions are allowed.
   Some of these Editions MAY be ordered and others not.

11.1.1.  EditionFlagDefault

   Only one "Edition" SHOULD have an "EditionFlagDefault" flag set to
   "true".

11.1.2.  Default Edition

   The "Default Edition" is the "Edition" that a "Matroska Player"
   SHOULD use for playback by default.

   The first "Edition" with the "EditionFlagDefault" flag set to "true"
   is the "Default Edition".

   When all "EditionFlagDefault" flags are set to "false", then the
   first "Edition" is the "Default Edition".

               +===========+=============+=================+
               | Edition   | FlagDefault | Default Edition |
               +===========+=============+=================+
               | Edition 1 | true        | X               |
               +-----------+-------------+-----------------+
               | Edition 2 | true        |                 |
               +-----------+-------------+-----------------+
               | Edition 3 | true        |                 |
               +-----------+-------------+-----------------+

                   Table 43: Default edition, all default

               +===========+=============+=================+
               | Edition   | FlagDefault | Default Edition |
               +===========+=============+=================+
               | Edition 1 | false       | X               |
               +-----------+-------------+-----------------+
               | Edition 2 | false       |                 |
               +-----------+-------------+-----------------+
               | Edition 3 | false       |                 |
               +-----------+-------------+-----------------+

                   Table 44: Default edition, no default

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               +===========+=============+=================+
               | Edition   | FlagDefault | Default Edition |
               +===========+=============+=================+
               | Edition 1 | false       |                 |
               +-----------+-------------+-----------------+
               | Edition 2 | true        | X               |
               +-----------+-------------+-----------------+
               | Edition 3 | false       |                 |
               +-----------+-------------+-----------------+

                  Table 45: Default edition, with default

11.1.3.  EditionFlagOrdered

   The "EditionFlagOrdered Flag" is a significant feature as it enables
   an "Edition" of "Ordered Chapters" which defines and arranges a
   virtual timeline rather than simply labeling points within the
   timeline.  For example, with "Editions" of "Ordered Chapters" a
   single "Matroska file" can present multiple edits of a film without
   duplicating content.  Alternatively, if a videotape is digitized in
   full, one "Ordered Edition" could present the full content (including
   colorbars, countdown, slate, a feature presentation, and black
   frames), while another "Edition" of "Ordered Chapters" can use
   "Chapters" that only mark the intended presentation with the
   colorbars and other ancillary visual information excluded.  If an
   "Edition" of "Ordered Chapters" is enabled, then the "Matroska
   Player" MUST play those Chapters in their stored order from the
   timestamp marked in the "ChapterTimeStart Element" to the timestamp
   marked in to "ChapterTimeEnd Element".

   If the "EditionFlagOrdered Flag" is set to "false", "Simple Chapters"
   are used and only the "ChapterTimeStart" of a "Chapter" is used as
   chapter mark to jump to the predefined point in the timeline.  With
   "Simple Chapters", a "Matroska Player" MUST ignore certain "Chapter
   Elements".  All these elements are now informational only.

   The following list shows the different Chapter elements only found in
   "Ordered Chapters".

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                 +======================================+
                 | Ordered Chapter elements             |
                 +======================================+
                 | ChapterAtom/ChapterSegmentUID        |
                 +--------------------------------------+
                 | ChapterAtom/ChapterSegmentEditionUID |
                 +--------------------------------------+
                 | ChapterAtom/ChapterTrack             |
                 +--------------------------------------+
                 | ChapterAtom/ChapProcess              |
                 +--------------------------------------+
                 | Info/SegmentFamily                   |
                 +--------------------------------------+
                 | Info/ChapterTranslate                |
                 +--------------------------------------+
                 | TrackEntry/TrackTranslate            |
                 +--------------------------------------+

                     Table 46: elements only found in
                             ordered chapters

   Furthermore there are other EBML "Elements" which could be used if
   the "EditionFlagOrdered" flag is set to "true".

11.1.3.1.  Ordered-Edition and Matroska Segment-Linking

   *  Hard Linking: "Ordered-Chapters" supersedes the "Hard Linking".

   *  Soft Linking: In this complex system "Ordered Chapters" are
      REQUIRED and a "Chapter CODEC" MUST interpret the "ChapProcess" of
      all chapters.

   *  Medium Linking: "Ordered Chapters" are used in a normal way and
      can be combined with the "ChapterSegmentUID" element which
      establishes a link to another Segment.

   See Section 23 on the Linked Segments for more information about
   "Hard Linking", "Soft Linking", and "Medium Linking".

11.1.4.  ChapterSegmentUID

   The "ChapterSegmentUID" is a binary value and the base element to set
   up a "Linked Chapter" in 2 variations: the Linked-Duration linking
   and the Linked-Edition linking.  For both variations, the following 3
   conditions MUST be met:

   1.  The "EditionFlagOrdered Flag" MUST be true.

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   2.  The "ChapterSegmentUID" MUST NOT be the "SegmentUID" of its own
       "Segment".

   3.  The linked Segments MUST BE in the same folder.

11.1.4.1.  Variation 1: Linked-Duration

   Two more conditions MUST be met:

   1.  "ChapterTimeStart" and "ChapterTimeEnd" timestamps MUST be in the
       range of the linked Segment duration.

   2.  "ChapterSegmentEditionUID" MUST be not set.

   A "Matroska Player" MUST play the content of the linked Segment from
   the "ChapterTimeStart" until "ChapterTimeEnd" timestamp.

11.1.4.2.  Variation 2: Linked-Edition

   When the "ChapterSegmentEditionUID" is set to a valid "EditionUID"
   from the linked Segment.  A "Matroska Player" MUST play these linked
   "Edition".

11.2.  ChapterAtom

   The "ChapterAtom" is also called a "Chapter".  A "Chapter" element
   can be used recursively.  Such a child "Chapter" is called "Nested
   Chapter".

11.2.1.  ChapterTimeStart

   A not scaled timestamp of the start of "Chapter" with nanosecond
   accuracy.  For "Simple Chapters" this is the position of the chapter
   markers in the timeline.

11.2.2.  ChapterTimeEnd

   A not scaled timestamp of the end of "Chapter" with nanosecond
   accuracy.  The end timestamp is used when the "EditionFlagOrdered"
   flag of the "Edition" is set to "true".  The timestamp defined by the
   "ChapterTimeEnd" is not part of the "Chapter".  A "Matroska Player"
   calculates the duration of this "Chapter" using the difference
   between the "ChapterTimeEnd" and "ChapterTimeStart".  The end
   timestamp MUST be greater than the start timestamp otherwise the
   duration would be negative which is illegal.  If the duration of a
   "Chapter" is 0, this "Chapter" MUST be ignored.

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       +===========+=================+===============+=============+
       | Chapter   | Start timestamp | End timestamp | Duration    |
       +===========+=================+===============+=============+
       | Chapter 1 | 0               | 1000000000    | 1000000000  |
       +-----------+-----------------+---------------+-------------+
       | Chapter 2 | 1000000000      | 5000000000    | 4000000000  |
       +-----------+-----------------+---------------+-------------+
       | Chapter 3 | 6000000000      | 6000000000    | 0 (chapter  |
       |           |                 |               | not used)   |
       +-----------+-----------------+---------------+-------------+
       | Chapter 4 | 9000000000      | 8000000000    | -1000000000 |
       |           |                 |               | (illegal)   |
       +-----------+-----------------+---------------+-------------+

                                  Table 47

11.2.3.  ChapterFlagHidden

   Each Chapter "ChapterFlagHidden" flag works independently from parent
   chapters.  A "Nested Chapter" with "ChapterFlagHidden" flag set to
   "false" remains visible even if the "Parent Chapter"
   "ChapterFlagHidden" flag is set to "true".

        +==========================+===================+=========+
        | Chapter + Nested Chapter | ChapterFlagHidden | visible |
        +==========================+===================+=========+
        | Chapter 1                | false             | yes     |
        +--------------------------+-------------------+---------+
        | Nested Chapter 1.1       | false             | yes     |
        +--------------------------+-------------------+---------+
        | Nested Chapter 1.2       | true              | no      |
        +--------------------------+-------------------+---------+
        | Chapter 2                | true              | no      |
        +--------------------------+-------------------+---------+
        | Nested Chapter 2.1       | false             | yes     |
        +--------------------------+-------------------+---------+
        | Nested Chapter 2.2       | true              | no      |
        +--------------------------+-------------------+---------+

                                 Table 48

11.3.  Menu features

   The menu features are handled like a "chapter codec".  That means
   each codec has a type, some private data and some data in the
   chapters.

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   The type of the menu system is defined by the "ChapProcessCodecID"
   parameter.  For now, only 2 values are supported : 0 matroska script,
   1 menu borrowed from the DVD.  The private data depend on the type of
   menu system (stored in "ChapProcessPrivate"), idem for the data in
   the chapters (stored in "ChapProcessData").

   The menu system, as well a Chapter Codecs in general, can do actions
   on the "Matroska Player" like jumping to another Chapter or Edition,
   selecting different tracks and possibly more.  The scope of all the
   possibilities of Chapter Codecs is not covered in this document as it
   depends on the Chapter Codec features and its integration in a
   "Matroska Player".

11.4.  Chapter Examples

11.4.1.  Example 1 : basic chaptering

   In this example a movie is split in different chapters.  It could
   also just be an audio file (album) on which each track corresponds to
   a chapter.

   *  00000ms - 05000ms : Intro

   *  05000ms - 25000ms : Before the crime

   *  25000ms - 27500ms : The crime

   *  27500ms - 38000ms : The killer arrested

   *  38000ms - 43000ms : Credits

   This would translate in the following matroska form :

   <Chapters>
     <EditionEntry>
       <EditionUID>16603393396715046047</EditionUID>
       <ChapterAtom>
         <ChapterUID>1193046</ChapterUID>
         <ChapterTimeStart>0</ChapterTimeStart>
         <ChapterTimeEnd>5000000000</ChapterTimeEnd>
         <ChapterDisplay>
           <ChapString>Intro</ChapString>
           <ChapLanguage>eng</ChapLanguage>
         </ChapterDisplay>
         <ChapterFlagHidden>0</ChapterFlagHidden>
       </ChapterAtom>
       <ChapterAtom>
         <ChapterUID>2311527</ChapterUID>

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         <ChapterTimeStart>5000000000</ChapterTimeStart>
         <ChapterTimeEnd>25000000000</ChapterTimeEnd>
         <ChapterDisplay>
           <ChapString>Before the crime</ChapString>
           <ChapLanguage>eng</ChapLanguage>
         </ChapterDisplay>
         <ChapterDisplay>
           <ChapString>Avant le crime</ChapString>
           <ChapLanguage>fra</ChapLanguage>
         </ChapterDisplay>
         <ChapterFlagHidden>0</ChapterFlagHidden>
       </ChapterAtom>
       <ChapterAtom>
         <ChapterUID>3430008</ChapterUID>
         <ChapterTimeStart>25000000000</ChapterTimeStart>
         <ChapterTimeEnd>27500000000</ChapterTimeEnd>
         <ChapterDisplay>
           <ChapString>The crime</ChapString>
           <ChapLanguage>eng</ChapLanguage>
         </ChapterDisplay>
         <ChapterDisplay>
           <ChapString>Le crime</ChapString>
           <ChapLanguage>fra</ChapLanguage>
         </ChapterDisplay>
         <ChapterFlagHidden>0</ChapterFlagHidden>
       </ChapterAtom>
       <ChapterAtom>
         <ChapterUID>4548489</ChapterUID>
         <ChapterTimeStart>27500000000</ChapterTimeStart>
         <ChapterTimeEnd>38000000000</ChapterTimeEnd>
         <ChapterDisplay>
           <ChapString>After the crime</ChapString>
           <ChapLanguage>eng</ChapLanguage>
         </ChapterDisplay>
         <ChapterDisplay>
           <ChapString>Après le crime</ChapString>
           <ChapLanguage>fra</ChapLanguage>
         </ChapterDisplay>
         <ChapterFlagHidden>0</ChapterFlagHidden>
       </ChapterAtom>
       <ChapterAtom>
         <ChapterUID>5666960</ChapterUID>
         <ChapterTimeStart>38000000000</ChapterTimeStart>
         <ChapterTimeEnd>43000000000</ChapterTimeEnd>
         <ChapterDisplay>
           <ChapString>Credits</ChapString>
           <ChapLanguage>eng</ChapLanguage>
         </ChapterDisplay>

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         <ChapterDisplay>
           <ChapString>Générique</ChapString>
           <ChapLanguage>fra</ChapLanguage>
         </ChapterDisplay>
         <ChapterFlagHidden>0</ChapterFlagHidden>
       </ChapterAtom>
       <EditionFlagDefault>0</EditionFlagDefault>
     </EditionEntry>
   </Chapters>

11.4.2.  Example 2 : nested chapters

   In this example an (existing) album is split into different chapters,
   and one of them contain another splitting.

11.4.2.1.  The Micronauts "Bleep To Bleep"

   *  00:00 - 12:28 : Baby Wants To Bleep/Rock

      -  00:00 - 04:38 : Baby wants to bleep (pt.1)

      -  04:38 - 07:12 : Baby wants to rock

      -  07:12 - 10:33 : Baby wants to bleep (pt.2)

      -  10:33 - 12:28 : Baby wants to bleep (pt.3)

   *  12:30 - 19:38 : Bleeper_O+2

   *  19:40 - 22:20 : Baby wants to bleep (pt.4)

   *  22:22 - 25:18 : Bleep to bleep

   *  25:20 - 33:35 : Baby wants to bleep (k)

   *  33:37 - 44:28 : Bleeper

   <Chapters>
     <EditionEntry>
       <EditionUID>1281690858003401414</EditionUID>
       <ChapterAtom>
         <ChapterUID>1</ChapterUID>
         <ChapterTimeStart>0</ChapterTimeStart>
         <ChapterTimeEnd>748000000</ChapterTimeEnd>
         <ChapterDisplay>
           <ChapString>Baby wants to Bleep/Rock</ChapString>
           <ChapLanguage>eng</ChapLanguage>
         </ChapterDisplay>

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         <ChapterAtom>
           <ChapterUID>2</ChapterUID>
           <ChapterTimeStart>0</ChapterTimeStart>
           <ChapterTimeEnd>278000000</ChapterTimeEnd>
           <ChapterDisplay>
             <ChapString>Baby wants to bleep (pt.1)</ChapString>
             <ChapLanguage>eng</ChapLanguage>
           </ChapterDisplay>
           <ChapterFlagHidden>0</ChapterFlagHidden>
         </ChapterAtom>
         <ChapterAtom>
           <ChapterUID>3</ChapterUID>
           <ChapterTimeStart>278000000</ChapterTimeStart>
           <ChapterTimeEnd>432000000</ChapterTimeEnd>
           <ChapterDisplay>
             <ChapString>Baby wants to rock</ChapString>
             <ChapLanguage>eng</ChapLanguage>
           </ChapterDisplay>
           <ChapterFlagHidden>0</ChapterFlagHidden>
         </ChapterAtom>
         <ChapterAtom>
           <ChapterUID>4</ChapterUID>
           <ChapterTimeStart>432000000</ChapterTimeStart>
           <ChapterTimeEnd>633000000</ChapterTimeEnd>
           <ChapterDisplay>
             <ChapString>Baby wants to bleep (pt.2)</ChapString>
             <ChapLanguage>eng</ChapLanguage>
           </ChapterDisplay>
           <ChapterFlagHidden>0</ChapterFlagHidden>
         </ChapterAtom>
         <ChapterAtom>
           <ChapterUID>5</ChapterUID>
           <ChapterTimeStart>633000000</ChapterTimeStart>
           <ChapterTimeEnd>748000000</ChapterTimeEnd>
           <ChapterDisplay>
             <ChapString>Baby wants to bleep (pt.3)</ChapString>
             <ChapLanguage>eng</ChapLanguage>
           </ChapterDisplay>
           <ChapterFlagHidden>0</ChapterFlagHidden>
         </ChapterAtom>
         <ChapterFlagHidden>0</ChapterFlagHidden>
       </ChapterAtom>
       <ChapterAtom>
         <ChapterUID>6</ChapterUID>
         <ChapterTimeStart>750000000</ChapterTimeStart>
         <ChapterTimeEnd>1178500000</ChapterTimeEnd>
         <ChapterDisplay>
           <ChapString>Bleeper_O+2</ChapString>

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           <ChapLanguage>eng</ChapLanguage>
         </ChapterDisplay>
         <ChapterFlagHidden>0</ChapterFlagHidden>
       </ChapterAtom>
       <ChapterAtom>
         <ChapterUID>7</ChapterUID>
         <ChapterTimeStart>1180500000</ChapterTimeStart>
         <ChapterTimeEnd>1340000000</ChapterTimeEnd>
         <ChapterDisplay>
           <ChapString>Baby wants to bleep (pt.4)</ChapString>
           <ChapLanguage>eng</ChapLanguage>
         </ChapterDisplay>
         <ChapterFlagHidden>0</ChapterFlagHidden>
       </ChapterAtom>
       <ChapterAtom>
         <ChapterUID>8</ChapterUID>
         <ChapterTimeStart>1342000000</ChapterTimeStart>
         <ChapterTimeEnd>1518000000</ChapterTimeEnd>
         <ChapterDisplay>
           <ChapString>Bleep to bleep</ChapString>
           <ChapLanguage>eng</ChapLanguage>
         </ChapterDisplay>
         <ChapterFlagHidden>0</ChapterFlagHidden>
       </ChapterAtom>
       <ChapterAtom>
         <ChapterUID>9</ChapterUID>
         <ChapterTimeStart>1520000000</ChapterTimeStart>
         <ChapterTimeEnd>2015000000</ChapterTimeEnd>
         <ChapterDisplay>
           <ChapString>Baby wants to bleep (k)</ChapString>
           <ChapLanguage>eng</ChapLanguage>
         </ChapterDisplay>
         <ChapterFlagHidden>0</ChapterFlagHidden>
       </ChapterAtom>
       <ChapterAtom>
         <ChapterUID>10</ChapterUID>
         <ChapterTimeStart>2017000000</ChapterTimeStart>
         <ChapterTimeEnd>2668000000</ChapterTimeEnd>
         <ChapterDisplay>
           <ChapString>Bleeper</ChapString>
           <ChapLanguage>eng</ChapLanguage>
         </ChapterDisplay>
         <ChapterFlagHidden>0</ChapterFlagHidden>
       </ChapterAtom>
       <EditionFlagDefault>0</EditionFlagDefault>
     </EditionEntry>
   </Chapters>

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12.  Attachments

   Matroska supports storage of related files and data in the
   "Attachments Element" (a "Top-Level Element").  "Attachment Elements"
   can be used to store related cover art, font files, transcripts,
   reports, error recovery files, picture, or text-based annotations,
   copies of specifications, or other ancillary files related to the
   "Segment".

   "Matroska Readers" MUST NOT execute files stored as "Attachment
   Elements".

12.1.  Cover Art

   This section defines a set of guidelines for the storage of cover art
   in Matroska files.  A "Matroska Reader" MAY use embedded cover art to
   display a representational still-image depiction of the multimedia
   contents of the Matroska file.

   Only JPEG and PNG image formats SHOULD be used for cover art
   pictures.

   There can be two different covers for a movie/album: a portrait style
   (e.g., a DVD case) and a landscape style (e.g., a wide banner ad).

   There can be two versions of the same cover, the "normal cover" and
   the "small cover".  The dimension of the "normal cover" SHOULD be 600
   pixels on the smallest side -- for example, 960x600 for landscape,
   600x800 for portrait, or 600x600 for square.  The dimension of the
   "small cover" SHOULD be 120 pixels on the smallest side -- for
   example, 192x120 or 120x160.

   Versions of cover art can be differentiated by the filename, which is
   stored in the "FileName Element".  The default filename of the
   "normal cover" in square or portrait mode is "cover.(jpg|png)".  When
   stored, the "normal cover" SHOULD be the first Attachment in storage
   order.  The "small cover" SHOULD be prefixed with "small_", such as
   "small_cover.(jpg|png)".  The landscape variant SHOULD be suffixed
   with "_land", such as "cover_land.(jpg|png)".  The filenames are case
   sensitive.

   The following table provides examples of file names for cover art in
   Attachments.

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      +======================+===================+=================+
      | FileName             | Image Orientation | Pixel Length of |
      |                      |                   | Smallest Side   |
      +======================+===================+=================+
      | cover.jpg            | Portrait or       | 600             |
      |                      | square            |                 |
      +----------------------+-------------------+-----------------+
      | small_cover.png      | Portrait or       | 120             |
      |                      | square            |                 |
      +----------------------+-------------------+-----------------+
      | cover_land.png       | Landscape         | 600             |
      +----------------------+-------------------+-----------------+
      | small_cover_land.jpg | Landscape         | 120             |
      +----------------------+-------------------+-----------------+

                                 Table 49

13.  Cues

   The "Cues Element" provides an index of certain "Cluster Elements" to
   allow for optimized seeking to absolute timestamps within the
   "Segment".  The "Cues Element" contains one or many "CuePoint
   Elements" which each MUST reference an absolute timestamp (via the
   "CueTime Element"), a "Track" (via the "CueTrack Element"), and a
   "Segment Position" (via the "CueClusterPosition Element").
   Additional non-mandated Elements are part of the "CuePoint Element"
   such as "CueDuration", "CueRelativePosition", "CueCodecState" and
   others which provide any "Matroska Reader" with additional
   information to use in the optimization of seeking performance.

13.1.  Recommendations

   The following recommendations are provided to optimize Matroska
   performance.

   *  Unless Matroska is used as a live stream, it SHOULD contain a
      "Cues Element".

   *  For each video track, each keyframe SHOULD be referenced by a
      "CuePoint Element".

   *  It is RECOMMENDED to not reference non-keyframes of video tracks
      in "Cues" unless it references a "Cluster Element" which contains
      a "CodecState Element" but no keyframes.

   *  For each subtitle track present, each subtitle frame SHOULD be
      referenced by a "CuePoint Element" with a "CueDuration Element".

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   *  References to audio tracks MAY be skipped in "CuePoint Elements"
      if a video track is present.  When included the "CuePoint
      Elements" SHOULD reference audio keyframes at most once every 500
      milliseconds.

   *  If the referenced frame is not stored within the first
      "SimpleBlock", or first "BlockGroup" within its "Cluster Element",
      then the "CueRelativePosition Element" SHOULD be written to
      reference where in the "Cluster" the reference frame is stored.

   *  If a "CuePoint Element" references "Cluster Element" that includes
      a "CodecState Element", then that "CuePoint Element" MUST use a
      "CueCodecState Element".

   *  "CuePoint Elements" SHOULD be numerically sorted in storage order
      by the value of the "CueTime Element".

14.  Matroska Streaming

   In Matroska, there are two kinds of streaming: file access and
   livestreaming.

14.1.  File Access

   File access can simply be reading a file located on your computer,
   but also includes accessing a file from an HTTP (web) server or CIFS
   (Windows share) server.  These protocols are usually safe from
   reading errors and seeking in the stream is possible.  However, when
   a file is stored far away or on a slow server, seeking can be an
   expensive operation and SHOULD be avoided.  The following guidelines,
   when followed, help reduce the number of seeking operations for
   regular playback and also have the playback start quickly without a
   lot of data needed to read first (like a "Cues Element", "Attachment
   Element" or "SeekHead Element").

   Matroska, having a small overhead, is well suited for storing music/
   videos on file servers without a big impact on the bandwidth used.
   Matroska does not require the index to be loaded before playing,
   which allows playback to start very quickly.  The index can be loaded
   only when seeking is requested the first time.

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14.2.  Livestreaming

   Livestreaming is the equivalent of television broadcasting on the
   internet.  There are 2 families of servers for livestreaming: RTP/
   RTSP and HTTP.  Matroska is not meant to be used over RTP.  RTP
   already has timing and channel mechanisms that would be wasted if
   doubled in Matroska.  Additionally, having the same information at
   the RTP and Matroska level would be a source of confusion if they do
   not match.  Livestreaming of Matroska over HTTP (or any other plain
   protocol based on TCP) is possible.

   A live Matroska stream is different from a file because it usually
   has no known end (only ending when the client disconnects).  For
   this, all bits of the "size" portion of the "Segment Element" MUST be
   set to 1.  Another option is to concatenate "Segment Elements" with
   known sizes, one after the other.  This solution allows a change of
   codec/resolution between each segment.  For example, this allows for
   a switch between 4:3 and 16:9 in a television program.

   When "Segment Elements" are continuous, certain "Elements", like
   "MetaSeek", "Cues", "Chapters", and "Attachments", MUST NOT be used.

   It is possible for a "Matroska Player" to detect that a stream is not
   seekable.  If the stream has neither a "MetaSeek" list or a "Cues"
   list at the beginning of the stream, it SHOULD be considered non-
   seekable.  Even though it is possible to seek blindly forward in the
   stream, it is NOT RECOMMENDED.

   In the context of live radio or web TV, it is possible to "tag" the
   content while it is playing.  The "Tags Element" can be placed
   between "Clusters" each time it is necessary.  In that case, the new
   "Tags Element" MUST reset the previously encountered "Tags Elements"
   and use the new values instead.

15.  Unknown elements

   Matroska is based upon the principle that a reading application does
   not have to support 100% of the specifications in order to be able to
   play the file.  A Matroska file therefore contains version indicators
   that tell a reading application what to expect.

   It is possible and valid to have the version fields indicate that the
   file contains Matroska "Elements" from a higher specification version
   number while signaling that a reading application MUST only support a
   lower version number properly in order to play it back (possibly with
   a reduced feature set).  For example, a reading application
   supporting at least Matroska version "V" reading a file whose
   "DocTypeReadVersion" field is equal to or lower than "V" MUST skip

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   Matroska/EBML "Elements" it encounters but does not know about if
   that unknown element fits into the size constraints set by the
   current "Parent Element".

16.  Default Values

   The default value of an "Element" is assumed when not present in the
   data stream.  It is assumed only in the scope of its "Parent
   Element".  For example, the "Language Element" is in the scope of the
   "Track Element".  If the "Parent Element" is not present or assumed,
   then the "Child Element" cannot be assumed.

17.  DefaultDecodedFieldDuration

   The "DefaultDecodedFieldDuration Element" can signal to the
   displaying application how often fields of a video sequence will be
   available for displaying.  It can be used for both interlaced and
   progressive content.  If the video sequence is signaled as
   interlaced, then the period between two successive fields at the
   output of the decoding process equals "DefaultDecodedFieldDuration".

   For video sequences signaled as progressive, it is twice the value of
   "DefaultDecodedFieldDuration".

   These values are valid at the end of the decoding process before
   post-processing (such as deinterlacing or inverse telecine) is
   applied.

   Examples:

   *  Blu-ray movie: 1000000000ns/(48/1.001) = 20854167ns

   *  PAL broadcast/DVD: 1000000000ns/(50/1.000) = 20000000ns

   *  N/ATSC broadcast: 1000000000ns/(60/1.001) = 16683333ns

   *  hard-telecined DVD: 1000000000ns/(60/1.001) = 16683333ns (60
      encoded interlaced fields per second)

   *  soft-telecined DVD: 1000000000ns/(60/1.001) = 16683333ns (48
      encoded interlaced fields per second, with "repeat_first_field =
      1")

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18.  Encryption

   Encryption in Matroska is designed in a very generic style to allow
   people to implement whatever form of encryption is best for them.  It
   is possible to use the encryption framework in Matroska as a type of
   DRM (Digital Rights Management).

   Because encryption occurs within the "Block Element", it is possible
   to manipulate encrypted streams without decrypting them.  The streams
   could potentially be copied, deleted, cut, appended, or any number of
   other possible editing techniques without decryption.  The data can
   be used without having to expose it or go through the decrypting
   process.

   Encryption can also be layered within Matroska.  This means that two
   completely different types of encryption can be used, requiring two
   separate keys to be able to decrypt a stream.

   Encryption information is stored in the "ContentEncodings Element"
   under the "ContentEncryption Element".

19.  Image Presentation

19.1.  Cropping

   The "PixelCrop Elements" ("PixelCropTop", "PixelCropBottom",
   "PixelCropRight", and "PixelCropLeft") indicate when, and by how
   much, encoded videos frames SHOULD be cropped for display.  These
   Elements allow edges of the frame that are not intended for display,
   such as the sprockets of a full-frame film scan or the VANC area of a
   digitized analog videotape, to be stored but hidden.  "PixelCropTop"
   and "PixelCropBottom" store an integer of how many rows of pixels
   SHOULD be cropped from the top and bottom of the image
   (respectively).  "PixelCropLeft" and "PixelCropRight" store an
   integer of how many columns of pixels SHOULD be cropped from the left
   and right of the image (respectively).  For example, a pillar-boxed
   video that stores a 1440x1080 visual image within the center of a
   padded 1920x1080 encoded image MAY set both "PixelCropLeft" and
   "PixelCropRight" to "240", so that a "Matroska Player" SHOULD crop
   off 240 columns of pixels from the left and right of the encoded
   image to present the image with the pillar-boxes hidden.

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19.2.  Rotation

   The ProjectionPoseRoll Element (see Section 9.4.1.36.20.5) can be
   used to indicate that the image from the associated video track
   SHOULD be rotated for presentation.  For instance, the following
   representation of the Projection Element Section 9.4.1.36.20) and the
   ProjectionPoseRoll Element represents a video track where the image
   SHOULD be presentation with a 90 degree counter-clockwise rotation.

   <Projection>
     <ProjectionPoseRoll>90</ProjectionPoseRoll>
   </Projection>

20.  Matroska versioning

   The "EBML Header" of each Matroska document informs the reading
   application on what version of Matroska to expect.  The "Elements"
   within "EBML Header" with jurisdiction over this information are
   "DocTypeVersion" and "DocTypeReadVersion".

   "DocTypeVersion" MUST be equal to or greater than the highest
   Matroska version number of any "Element" present in the Matroska
   file.  For example, a file using the "SimpleBlock Element" MUST have
   a "DocTypeVersion" equal to or greater than 2.  A file containing
   "CueRelativePosition" Elements MUST have a "DocTypeVersion" equal to
   or greater than 4.

   The "DocTypeReadVersion" MUST contain the minimum version number that
   a reading application can minimally support in order to play the file
   back -- optionally with a reduced feature set.  For example, if a
   file contains only "Elements" of version 2 or lower except for
   "CueRelativePosition" (which is a version 4 Matroska "Element"), then
   "DocTypeReadVersion" SHOULD still be set to 2 and not 4 because
   evaluating "CueRelativePosition" is not necessary for standard
   playback -- it makes seeking more precise if used.

   "DocTypeVersion" MUST always be equal to or greater than
   "DocTypeReadVersion".

   A reading application supporting Matroska version "V" MUST NOT refuse
   to read an application with "DocReadTypeVersion" equal to or lower
   than "V" even if "DocTypeVersion" is greater than "V".  See also the
   note about Unknown Elements in Section 15.

21.  MIME Types

   There is no IETF endorsed MIME type for Matroska files.  These
   definitions can be used:

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   *  .mka : Matroska audio "audio/x-matroska"

   *  .mkv : Matroska video "video/x-matroska"

   *  .mk3d : Matroska 3D video "video/x-matroska-3d"

22.  Segment Position

   The "Segment Position" of an "Element" refers to the position of the
   first octet of the "Element ID" of that "Element", measured in
   octets, from the beginning of the "Element Data" section of the
   containing "Segment Element".  In other words, the "Segment Position"
   of an "Element" is the distance in octets from the beginning of its
   containing "Segment Element" minus the size of the "Element ID" and
   "Element Data Size" of that "Segment Element".  The "Segment
   Position" of the first "Child Element" of the "Segment Element" is 0.
   An "Element" which is not stored within a "Segment Element", such as
   the "Elements" of the "EBML Header", do not have a "Segment
   Position".

22.1.  Segment Position Exception

   "Elements" that are defined to store a "Segment Position" MAY define
   reserved values to indicate a special meaning.

22.2.  Example of Segment Position

   This table presents an example of "Segment Position" by showing a
   hexadecimal representation of a very small Matroska file with labels
   to show the offsets in octets.  The file contains a "Segment Element"
   with an "Element ID" of "0x18538067" and a "MuxingApp Element" with
   an "Element ID" of "0x4D80".

        0                             1                             2
        0  1  2  3  4  5  6  7  8  9  0  1  2  3  4  5  6  7  8  9  0
        +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
      0 |1A|45|DF|A3|8B|42|82|88|6D|61|74|72|6F|73|6B|61|18|53|80|67|
     20 |93|15|49|A9|66|8E|4D|80|84|69|65|74|66|57|41|84|69|65|74|66|

   In the above example, the "Element ID" of the "Segment Element" is
   stored at offset 16, the "Element Data Size" of the "Segment Element"
   is stored at offset 20, and the "Element Data" of the "Segment
   Element" is stored at offset 21.

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   The "MuxingApp Element" is stored at offset 26.  Since the "Segment
   Position" of an "Element" is calculated by subtracting the position
   of the "Element Data" of the containing "Segment Element" from the
   position of that "Element", the "Segment Position" of "MuxingApp
   Element" in the above example is '26 - 21' or '5'.

23.  Linked Segments

   Matroska provides several methods to link two or many "Segment
   Elements" together to create a "Linked Segment".  A "Linked Segment"
   is a set of multiple "Segments" related together into a single
   presentation by using Hard Linking, Medium Linking, or Soft Linking.
   All "Segments" within a "Linked Segment" MUST utilize the same track
   numbers and timescale.  All "Segments" within a "Linked Segment" MUST
   be stored within the same directory.  All "Segments" within a "Linked
   Segment" MUST store a "SegmentUID".

23.1.  Hard Linking

   Hard Linking (also called splitting) is the process of creating a
   "Linked Segment" by relating multiple "Segment Elements" using the
   "NextUID" and "PrevUID" Elements.  Within a "Linked Segment", the
   timestamps of each "Segment" MUST follow consecutively in linking
   order.  With Hard Linking, the chapters of any "Segment" within the
   "Linked Segment" MUST only reference the current "Segment".  With
   Hard Linking, the "NextUID" and "PrevUID" MUST reference the
   respective "SegmentUID" values of the next and previous "Segments".
   The first "Segment" of a "Linked Segment" SHOULD have a "NextUID
   Element" and MUST NOT have a "PrevUID Element".  The last "Segment"
   of a "Linked Segment" SHOULD have a "PrevUID Element" and MUST NOT
   have a "NextUID Element".  The middle "Segments" of a "Linked
   Segment" SHOULD have both a "NextUID Element" and a "PrevUID
   Element".

   In a chain of "Linked Segments" the "NextUID" always takes precedence
   over the "PrevUID".  So if SegmentA has a NextUID to SegmentB and
   SegmentB has a PrevUID to SegmentC, the link to use is SegmentA to
   SegmentB.  If SegmentB has a PrevUID to SegmentA but SegmentA has no
   NextUID, then the Matroska Player MAY consider these two Segments
   linked as SegmentA followed by SegmentB.

   As an example, three "Segments" can be Hard Linked as a "Linked
   Segment" through cross-referencing each other with "SegmentUID",
   "PrevUID", and "NextUID", as in this table.

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   +==========+==================+==================+==================+
   |file name | SegmentUID       | PrevUID          | NextUID          |
   +==========+==================+==================+==================+
   |start.mkv | 71000c23cd310998 | n/a              | a77b3598941cb803 |
   |          | 53fbc94dd984a5dd |                  | eac0fcdafe44fac9 |
   +----------+------------------+------------------+------------------+
   |middle.mkv| a77b3598941cb803 | 71000c23cd310998 | 6c92285fa6d3e827 |
   |          | eac0fcdafe44fac9 | 53fbc94dd984a5dd | b198d120ea3ac674 |
   +----------+------------------+------------------+------------------+
   |end.mkv   | 6c92285fa6d3e827 | a77b3598941cb803 | n/a              |
   |          | b198d120ea3ac674 | eac0fcdafe44fac9 |                  |
   +----------+------------------+------------------+------------------+

                                  Table 50

   An other example where only the "NextUID" Element is used.

      +============+==================+=========+==================+
      | file name  | SegmentUID       | PrevUID | NextUID          |
      +============+==================+=========+==================+
      | start.mkv  | 71000c23cd310998 | n/a     | a77b3598941cb803 |
      |            | 53fbc94dd984a5dd |         | eac0fcdafe44fac9 |
      +------------+------------------+---------+------------------+
      | middle.mkv | a77b3598941cb803 | n/a     | 6c92285fa6d3e827 |
      |            | eac0fcdafe44fac9 |         | b198d120ea3ac674 |
      +------------+------------------+---------+------------------+
      | end.mkv    | 6c92285fa6d3e827 | n/a     | n/a              |
      |            | b198d120ea3ac674 |         |                  |
      +------------+------------------+---------+------------------+

                                 Table 51

   A next example where only the "PrevUID" Element is used.

      +============+==================+==================+=========+
      | file name  | SegmentUID       | PrevUID          | NextUID |
      +============+==================+==================+=========+
      | start.mkv  | 71000c23cd310998 | n/a              | n/a     |
      |            | 53fbc94dd984a5dd |                  |         |
      +------------+------------------+------------------+---------+
      | middle.mkv | a77b3598941cb803 | 71000c23cd310998 | n/a     |
      |            | eac0fcdafe44fac9 | 53fbc94dd984a5dd |         |
      +------------+------------------+------------------+---------+
      | end.mkv    | 6c92285fa6d3e827 | a77b3598941cb803 | n/a     |
      |            | b198d120ea3ac674 | eac0fcdafe44fac9 |         |
      +------------+------------------+------------------+---------+

                                 Table 52

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   In this example only the "middle.mkv" is using the "PrevUID" and
   "NextUID" Elements.

   +==========+==================+==================+==================+
   |file name | SegmentUID       | PrevUID          | NextUID          |
   +==========+==================+==================+==================+
   |start.mkv | 71000c23cd310998 | n/a              | n/a              |
   |          | 53fbc94dd984a5dd |                  |                  |
   +----------+------------------+------------------+------------------+
   |middle.mkv| a77b3598941cb803 | 71000c23cd310998 | 6c92285fa6d3e827 |
   |          | eac0fcdafe44fac9 | 53fbc94dd984a5dd | b198d120ea3ac674 |
   +----------+------------------+------------------+------------------+
   |end.mkv   | 6c92285fa6d3e827 | n/a              | n/a              |
   |          | b198d120ea3ac674 |                  |                  |
   +----------+------------------+------------------+------------------+

                                  Table 53

23.2.  Medium Linking

   Medium Linking creates relationships between "Segments" using Ordered
   Chapters and the "ChapterSegmentUID Element".  A "Segment Edition"
   with Ordered Chapters MAY contain Chapter elements that reference
   timestamp ranges from other "Segments".  The "Segment" referenced by
   the Ordered Chapter via the "ChapterSegmentUID Element" SHOULD be
   played as part of a Linked Segment.  The timestamps of Segment
   content referenced by Ordered Chapters MUST be adjusted according to
   the cumulative duration of the the previous Ordered Chapters.

   As an example a file named "intro.mkv" could have a "SegmentUID" of
   "0xb16a58609fc7e60653a60c984fc11ead".  Another file called
   "program.mkv" could use a Chapter Edition that contains two Ordered
   Chapters.  The first chapter references the "Segment" of "intro.mkv"
   with the use of a "ChapterSegmentUID", "ChapterSegmentEditionUID",
   "ChapterTimeStart", and optionally a "ChapterTimeEnd" element.  The
   second chapter references content within the "Segment" of
   "program.mkv".  A "Matroska Player" SHOULD recognize the "Linked
   Segment" created by the use of "ChapterSegmentUID" in an enabled
   "Edition" and present the reference content of the two "Segments"
   together.

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23.3.  Soft Linking

   Soft Linking is used by codec chapters.  They can reference another
   "Segment" and jump to that "Segment".  The way the "Segments" are
   described are internal to the chapter codec and unknown to the
   Matroska level.  But there are "Elements" within the "Info Element"
   (such as "ChapterTranslate") that can translate a value representing
   a "Segment" in the chapter codec and to the current "SegmentUID".
   All "Segments" that could be used in a "Linked Segment" in this way
   SHOULD be marked as members of the same family via the "SegmentFamily
   Element", so that the "Matroska Player" can quickly switch from one
   to the other.

24.  Track Flags

24.1.  Default flag

   The "default track" flag is a hint for a "Matroska Player" indicating
   that a given track SHOULD be eligible to be automatically selected as
   the default track for a given language.  If no tracks in a given
   language have the default track flag set, then all tracks in that
   language are eligible for automatic selection.  This can be used to
   indicate that a track provides "regular service" suitable for users
   with default settings, as opposed to specialized services, such as
   commentary, hearing-impaired captions, or descriptive audio.

   The "Matroska Player" MAY override the "default track" flag for any
   reason, including user preferences to prefer tracks providing
   accessibility services.

24.2.  Forced flag

   The "forced" flag tells the "Matroska Player" that it SHOULD display
   this subtitle track, even if user preferences usually would not call
   for any subtitles to be displayed alongside the current selected
   audio track.  This can be used to indicate that a track contains
   translations of onscreen text, or of dialogue spoken in a different
   language than the track's primary one.

24.3.  Hearing-impaired flag

   The "hearing impaired" flag tells the "Matroska Player" that it
   SHOULD prefer this track when selecting a default track for a
   hearing-impaired user, and that it MAY prefer to select a different
   track when selecting a default track for a non-hearing-impaired user.

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24.4.  Visual-impaired flag

   The "visual impaired" flag tells the "Matroska Player" that it SHOULD
   prefer this track when selecting a default track for a visually-
   impaired user, and that it MAY prefer to select a different track
   when selecting a default track for a non-visually-impaired user.

24.5.  Descriptions flag

   The "descriptions" flag tells the "Matroska Player" that this track
   is suitable to play via a text-to-speech system for a visually-
   impaired user, and that it SHOULD NOT automatically select this track
   when selecting a default track for a non-visually-impaired user.

24.6.  Original flag

   The "original" flag tells the "Matroska Player" that this track is in
   the original language, and that it SHOULD prefer it if configured to
   prefer original-language tracks of this track's type.

24.7.  Commentary flag

   The "commentary" flag tells the "Matroska Player" that this track
   contains commentary on the content.

24.8.  Track Operation

   "TrackOperation" allows combining multiple tracks to make a virtual
   one.  It uses two separate system to combine tracks.  One to create a
   3D "composition" (left/right/background planes) and one to simplify
   join two tracks together to make a single track.

   A track created with "TrackOperation" is a proper track with a UID
   and all its flags.  However the codec ID is meaningless because each
   "sub" track needs to be decoded by its own decoder before the
   "operation" is applied.  The "Cues Elements" corresponding to such a
   virtual track SHOULD be the sum of the "Cues Elements" for each of
   the tracks it's composed of (when the "Cues" are defined per track).

   In the case of "TrackJoinBlocks", the "Block Elements" (from
   "BlockGroup" and "SimpleBlock") of all the tracks SHOULD be used as
   if they were defined for this new virtual "Track".  When two "Block
   Elements" have overlapping start or end timestamps, it's up to the
   underlying system to either drop some of these frames or render them
   the way they overlap.  This situation SHOULD be avoided when creating
   such tracks as you can never be sure of the end result on different
   platforms.

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24.9.  Overlay Track

   Overlay tracks SHOULD be rendered in the same channel as the track
   its linked to.  When content is found in such a track, it SHOULD be
   played on the rendering channel instead of the original track.

24.10.  Multi-planar and 3D videos

   There are two different ways to compress 3D videos: have each eye
   track in a separate track and have one track have both eyes combined
   inside (which is more efficient, compression-wise).  Matroska
   supports both ways.

   For the single track variant, there is the "StereoMode Element",
   which defines how planes are assembled in the track (mono or left-
   right combined).  Odd values of StereoMode means the left plane comes
   first for more convenient reading.  The pixel count of the track
   ("PixelWidth"/"PixelHeight") is the raw amount of pixels, for example
   3840x1080 for full HD side by side, and the
   "DisplayWidth"/"DisplayHeight" in pixels is the amount of pixels for
   one plane (1920x1080 for that full HD stream).  Old stereo 3D were
   displayed using anaglyph (cyan and red colours separated).  For
   compatibility with such movies, there is a value of the StereoMode
   that corresponds to AnaGlyph.

   There is also a "packed" mode (values 13 and 14) which consists of
   packing two frames together in a "Block" using lacing.  The first
   frame is the left eye and the other frame is the right eye (or vice
   versa).  The frames SHOULD be decoded in that order and are possibly
   dependent on each other (P and B frames).

   For separate tracks, Matroska needs to define exactly which track
   does what.  "TrackOperation" with "TrackCombinePlanes" do that.  For
   more details look at Section 24.8 on how TrackOperation works.

   The 3D support is still in infancy and may evolve to support more
   features.

   The StereoMode used to be part of Matroska v2 but it didn't meet the
   requirement for multiple tracks.  There was also a bug in libmatroska
   prior to 0.9.0 that would save/read it as 0x53B9 instead of 0x53B8.
   "Matroska Readers" may support these legacy files by checking
   Matroska v2 or 0x53B9.  The older values were 0: mono, 1: right eye,
   2: left eye, 3: both eyes.

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25.  Default track selection

   This section provides some example sets of Tracks and hypothetical
   user settings, along with indications of which ones a similarly-
   configured "Matroska Player" SHOULD automatically select for playback
   by default in such a situation.  A player MAY provide additional
   settings with more detailed controls for more nuanced scenarios.
   These examples are provided as guidelines to illustrate the intended
   usages of the various supported Track flags, and their expected
   behaviors.

   Track names are shown in English for illustrative purposes; actual
   files may have titles in the language of each track, or provide
   titles in multiple languages.

25.1.  Audio Selection

   Example track set:

   +===+=====+====+======+========+=======+================+===========+
   |No.|Type |Lang|Layout|Original|Default|Other flags     |Name       |
   +===+=====+====+======+========+=======+================+===========+
   |1  |Video|und |N/A   |N/A     |N/A    |None            |           |
   +---+-----+----+------+--------+-------+----------------+-----------+
   |2  |Audio|eng |5.1   |1       |1      |None            |           |
   +---+-----+----+------+--------+-------+----------------+-----------+
   |3  |Audio|eng |2.0   |1       |1      |None            |           |
   +---+-----+----+------+--------+-------+----------------+-----------+
   |4  |Audio|eng |2.0   |1       |0      |Visual-impaired |Descriptive|
   |   |     |    |      |        |       |                |audio      |
   +---+-----+----+------+--------+-------+----------------+-----------+
   |5  |Audio|esp |5.1   |0       |1      |None            |           |
   +---+-----+----+------+--------+-------+----------------+-----------+
   |6  |Audio|esp |2.0   |0       |0      |Visual-impaired |Descriptive|
   |   |     |    |      |        |       |                |audio      |
   +---+-----+----+------+--------+-------+----------------+-----------+
   |7  |Audio|eng |2.0   |1       |0      |Commentary      |Director's |
   |   |     |    |      |        |       |                |Commentary |
   +---+-----+----+------+--------+-------+----------------+-----------+
   |8  |Audio|eng |2.0   |1       |0      |None            |Karaoke    |
   +---+-----+----+------+--------+-------+----------------+-----------+

                                  Table 54

   Here we have a file with 7 audio tracks, of which 5 are in English
   and 2 are in Spanish.

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   The English tracks all have the Original flag, indicating that
   English is the original content language.

   Generally the player will first consider the track languages: if the
   player has an option to prefer original-language audio and the user
   has enabled it, then it should prefer one of the Original-flagged
   tracks.  If configured to specifically prefer audio tracks in English
   or Spanish, the player should select one of the tracks in the
   corresponding language.  The player may also wish to prefer an
   Original-flagged track if no tracks matching any of the user's
   explicitly-preferred languages are available.

   Two of the tracks have the Visual-impaired flag.  If the player has
   been configured to prefer such tracks, it should select one;
   otherwise, it should avoid them if possible.

   If selecting an English track, when other settings have left multiple
   possible options, it may be useful to exclude the tracks that lack
   the Default flag: here, one provides descriptive service for the
   visually impaired (which has its own flag and may be automatically
   selected by user configuration, but is unsuitable for users with
   default-configured players), one is a commentary track (which has its
   own flag, which the player may or may not have specialized handling
   for), and the last contains karaoke versions of the music that plays
   during the film, which is an unusual specialized audio service that
   Matroska has no built-in support for indicating, so it's indicated in
   the track name instead.  By not setting the Default flag on these
   specialized tracks, the file's author hints that they should not be
   automatically selected by a default-configured player.

   Having narrowed its choices down, our example player now may have to
   select between tracks 2 and 3.  The only difference between these
   tracks is their channel layouts: 2 is 5.1 surround, while 3 is
   stereo.  If the player is aware that the output device is a pair of
   headphones or stereo speakers, it may wish to prefer the stereo mix
   automatically.  On the other hand, if it knows that the device is a
   surround system, it may wish to prefer the surround mix.

   If the player finishes analyzing all of the available audio tracks
   and finds that multiple seem equally and maximally preferable, it
   SHOULD default to the first of the group.

25.2.  Subtitle selection

   Example track set:

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   +===+===========+====+=========+=======+======+==========+==========+
   |No.| Type      |Lang|Original |Default|Forced| Other    | Name     |
   |   |           |    |         |       |      | flags    |          |
   +===+===========+====+=========+=======+======+==========+==========+
   |1  | Video     |und |N/A      |N/A    |N/A   | None     |          |
   +---+-----------+----+---------+-------+------+----------+----------+
   |2  | Audio     |fra |1        |1      |N/A   | None     |          |
   +---+-----------+----+---------+-------+------+----------+----------+
   |3  | Audio     |por |0        |1      |N/A   | None     |          |
   +---+-----------+----+---------+-------+------+----------+----------+
   |4  | Subtitles |fra |1        |1      |0     | None     |          |
   +---+-----------+----+---------+-------+------+----------+----------+
   |5  | Subtitles |fra |1        |0      |0     | Hearing- | Captions |
   |   |           |    |         |       |      | impaired | for the  |
   |   |           |    |         |       |      |          | hearing- |
   |   |           |    |         |       |      |          | impaired |
   +---+-----------+----+---------+-------+------+----------+----------+
   |6  | Subtitles |por |0        |1      |0     | None     |          |
   +---+-----------+----+---------+-------+------+----------+----------+
   |7  | Subtitles |por |0        |0      |1     | None     | Signs    |
   +---+-----------+----+---------+-------+------+----------+----------+
   |8  | Subtitles |por |0        |0      |0     | Hearing- | SDH      |
   |   |           |    |         |       |      | impaired |          |
   +---+-----------+----+---------+-------+------+----------+----------+

                                  Table 55

   Here we have 2 audio tracks and 5 subtitle tracks.  As we can see,
   French is the original language.

   We'll start by discussing the case where the user prefers French (or
   Original-language) audio (or has explicitly selected the French audio
   track), and also prefers French subtitles.

   In this case, if the player isn't configured to display captions when
   the audio matches their preferred subtitle languages, the player
   doesn't need to select a subtitle track at all.

   If the user _has_ indicated that they want captions to be displayed,
   the selection simply comes down to whether Hearing-impaired subtitles
   are preferred.

   The situation for a user who prefers Portuguese subtitles starts out
   somewhat analogous.  If they select the original French audio (either
   by explicit audio language preference, preference for Original-
   language tracks, or by explicitly selecting that track), then the
   selection once again comes down to the hearing-impaired preference.

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   However, the case where the Portuguese audio track is selected has an
   important catch: a Forced track in Portuguese is present.  This may
   contain translations of onscreen text from the video track, or of
   portions of the audio that are not translated (music, for instance).
   This means that even if the user's preferences wouldn't normally call
   for captions here, the Forced track should be selected nonetheless,
   rather than selecting no track at all.  On the other hand, if the
   user's preferences _do_ call for captions, the non-Forced tracks
   should be preferred, as the Forced track will not contain captioning
   for the dialogue.

26.  Timestamps

   Historically timestamps in Matroska were mistakenly called timecodes.
   The "Timestamp Element" was called Timecode, the "TimestampScale
   Element" was called TimecodeScale, the "TrackTimestampScale Element"
   was called TrackTimecodeScale and the "ReferenceTimestamp Element"
   was called ReferenceTimeCode.

26.1.  Timestamp Types

   *  Absolute Timestamp = Block+Cluster

   *  Relative Timestamp = Block

   *  Scaled Timestamp = Block+Cluster

   *  Raw Timestamp = (Block+Cluster)*TimestampScale*TrackTimestampScale

26.2.  Block Timestamps

   The "Block Element"'s timestamp MUST be a signed integer that
   represents the "Raw Timestamp" relative to the "Cluster"'s "Timestamp
   Element", multiplied by the "TimestampScale Element".  See
   Section 26.4 for more information.

   The "Block Element"'s timestamp MUST be represented by a 16bit signed
   integer (sint16).  The "Block"'s timestamp has a range of -32768 to
   +32767 units.  When using the default value of the "TimestampScale
   Element", each integer represents 1ms.  The maximum time span of
   "Block Elements" in a "Cluster" using the default "TimestampScale
   Element" of 1ms is 65536ms.

   If a "Cluster"'s "Timestamp Element" is set to zero, it is possible
   to have "Block Elements" with a negative "Raw Timestamp".  "Block
   Elements" with a negative "Raw Timestamp" are not valid.

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26.3.  Raw Timestamp

   The exact time of an object SHOULD be represented in nanoseconds.  To
   find out a "Block"'s "Raw Timestamp", you need the "Block"'s
   "Timestamp Element", the "Cluster"'s "Timestamp Element", and the
   "TimestampScale Element".

26.4.  TimestampScale

   The "TimestampScale Element" is used to calculate the "Raw Timestamp"
   of a "Block".  The timestamp is obtained by adding the "Block"'s
   timestamp to the "Cluster"'s "Timestamp Element", and then
   multiplying that result by the "TimestampScale".  The result will be
   the "Block"'s "Raw Timestamp" in nanoseconds.  The formula for this
   would look like:

   (a + b) * c

   a = `Block`'s Timestamp
   b = `Cluster`'s Timestamp
   c = `TimestampScale`

   For example, assume a "Cluster"'s "Timestamp" has a value of 564264,
   the "Block" has a "Timestamp" of 1233, and the "TimestampScale
   Element" is the default of 1000000.

   (1233 + 564264) * 1000000 = 565497000000

   So, the "Block" in this example has a specific time of 565497000000
   in nanoseconds.  In milliseconds this would be 565497ms.

26.5.  TimestampScale Rounding

   Because the default value of "TimestampScale" is 1000000, which makes
   each integer in the "Cluster" and "Block" "Timestamp Elements" equal
   1ms, this is the most commonly used.  When dealing with audio, this
   causes inaccuracy when seeking.  When the audio is combined with
   video, this is not an issue.  For most cases, the the synch of audio
   to video does not need to be more than 1ms accurate.  This becomes
   obvious when one considers that sound will take 2-3ms to travel a
   single meter, so distance from your speakers will have a greater
   effect on audio/visual synch than this.

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   However, when dealing with audio-only files, seeking accuracy can
   become critical.  For instance, when storing a whole CD in a single
   track, a user will want to be able to seek to the exact sample that a
   song begins at.  If seeking a few sample ahead or behind, a crack or
   pop may result as a few odd samples are rendered.  Also, when
   performing precise editing, it may be very useful to have the audio
   accuracy down to a single sample.

   When storing timestamps for an audio stream, the "TimestampScale
   Element" SHOULD have an accuracy of at least that of the audio sample
   rate, otherwise there are rounding errors that prevent users from
   knowing the precise location of a sample.  Here's how a program has
   to round each timestamp in order to be able to recreate the sample
   number accurately.

   Let's assume that the application has an audio track with a sample
   rate of 44100.  As written above the "TimestampScale" MUST have at
   least the accuracy of the sample rate itself: 1000000000 / 44100 =
   22675.7369614512.  This value MUST always be truncated.  Otherwise
   the accuracy will not suffice.  So in this example the application
   will use 22675 for the "TimestampScale".  The application could even
   use some lower value like 22674, which would allow it to be a little
   bit imprecise about the original timestamps.  But more about that in
   a minute.

   Next the application wants to write sample number 52340 and
   calculates the timestamp.  This is easy.  In order to calculate the
   "Raw Timestamp" in ns all it has to do is calculate "Raw Timestamp =
   round(1000000000 * sample_number / sample_rate)".  Rounding at this
   stage is very important!  The application might skip it if it choses
   a slightly smaller value for the "TimestampScale" factor instead of
   the truncated one like shown above.  Otherwise it has to round or the
   results won't be reversible.  For our example we get "Raw Timestamp =
   round(1000000000 * 52340 / 44100) = round(1186848072.56236) =
   1186848073".

   The next step is to calculate the "Absolute Timestamp" - that is the
   timestamp that will be stored in the Matroska file.  Here the
   application has to divide the "Raw Timestamp" from the previous
   paragraph by the "TimestampScale" factor and round the result:
   "Absolute Timestamp = round(Raw Timestamp / TimestampScale_factor)",
   which will result in the following for our example: "Absolute
   Timestamp = round(1186848073 / 22675) = round(52341.7011245866) =
   52342".  This number is the one the application has to write to the
   file.

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   Now our file is complete, and we want to play it back with another
   application.  Its task is to find out which sample the first
   application wrote into the file.  So it starts reading the Matroska
   file and finds the "TimestampScale" factor 22675 and the audio sample
   rate 44100.  Later it finds a data block with the "Absolute
   Timestamp" of 52342.  But how does it get the sample number from
   these numbers?

   First it has to calculate the "Raw Timestamp" of the block it has
   just read.  Here's no rounding involved, just an integer
   multiplication: "Raw Timestamp = Absolute Timestamp *
   TimestampScale_factor".  In our example: "Raw Timestamp = 52342 *
   22675 = 1186854850".

   The conversion from the "Raw Timestamp" to the sample number again
   requires rounding: "sample_number = round(Raw Timestamp * sample_rate
   / 1000000000)".  In our example: "sample_number = round(1186854850 *
   44100 / 1000000000) = round(52340.298885) = 52340".  This is exactly
   the sample number that the previous program started with.

   Some general notes for a program:

   1.  Always calculate the timestamps / sample numbers with floating
       point numbers of at least 64bit precision (called 'double' in
       most modern programming languages).  If you're calculating with
       integers, then make sure they're 64bit long, too.

   2.  Always round if you divide.  Always!  If you don't you'll end up
       with situations in which you have a timestamp in the Matroska
       file that does not correspond to the sample number that it
       started with.  Using a slightly lower timestamp scale factor can
       help here in that it removes the need for proper rounding in the
       conversion from sample number to "Raw Timestamp".

26.6.  TrackTimestampScale

   The "TrackTimestampScale Element" is used align tracks that would
   otherwise be played at different speeds.  An example of this would be
   if you have a film that was originally recorded at 24fps video.  When
   playing this back through a PAL broadcasting system, it is standard
   to speed up the film to 25fps to match the 25fps display speed of the
   PAL broadcasting standard.  However, when broadcasting the video
   through NTSC, it is typical to leave the film at its original speed.
   If you wanted to make a single file where there was one video stream,
   and an audio stream used from the PAL broadcast, as well as an audio
   stream used from the NTSC broadcast, you would have the problem that
   the PAL audio stream would be 1/24th faster than the NTSC audio
   stream, quickly leading to problems.  It is possible to stretch out

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   the PAL audio track and re-encode it at a slower speed, however when
   dealing with lossy audio codecs, this often results in a loss of
   audio quality and/or larger file sizes.

   This is the type of problem that "TrackTimestampScale" was designed
   to fix.  Using it, the video can be played back at a speed that will
   synch with either the NTSC or the PAL audio stream, depending on
   which is being used for playback.  To continue the above example:

   Track 1: Video
   Track 2: NTSC Audio
   Track 3: PAL Audio

   Because the NTSC track is at the original speed, it will used as the
   default value of 1.0 for its "TrackTimestampScale".  The video will
   also be aligned to the NTSC track with the default value of 1.0.

   The "TrackTimestampScale" value to use for the PAL track would be
   calculated by determining how much faster the PAL track is than the
   NTSC track.  In this case, because we know the video for the NTSC
   audio is being played back at 24fps and the video for the PAL audio
   is being played back at 25fps, the calculation would be:

   25/24 is almost 1.04166666666666666667

   When writing a file that uses a non-default "TrackTimestampScale",
   the values of the "Block"'s timestamp are whatever they would be when
   normally storing the track with a default value for the
   "TrackTimestampScale".  However, the data is interleaved a little
   differently.  Data SHOULD be interleaved by its Raw Timestamp, see
   Section 26.3, in the order handed back from the encoder.  The "Raw
   Timestamp" of a "Block" from a track using "TrackTimestampScale" is
   calculated using:

   "(Block's Timestamp + Cluster's Timestamp) * TimestampScale *
   TrackTimestampScale"

   So, a Block from the PAL track above that had a Scaled Timestamp, see
   Section 26.1, of 100 seconds would have a "Raw Timestamp" of
   104.66666667 seconds, and so would be stored in that part of the
   file.

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   When playing back a track using the "TrackTimestampScale", if the
   track is being played by itself, there is no need to scale it.  From
   the above example, when playing the Video with the NTSC Audio,
   neither are scaled.  However, when playing back the Video with the
   PAL Audio, the timestamps from the PAL Audio track are scaled using
   the "TrackTimestampScale", resulting in the video playing back in
   synch with the audio.

   It would be possible for a "Matroska Player" to also adjust the
   audio's samplerate at the same time as adjusting the timestamps if
   you wanted to play the two audio streams synchronously.  It would
   also be possible to adjust the video to match the audio's speed.
   However, for playback, the selected track(s) timestamps SHOULD be
   adjusted if they need to be scaled.

   While the above example deals specifically with audio tracks, this
   element can be used to align video, audio, subtitles, or any other
   type of track contained in a Matroska file.

27.  Normative References

   [BCP47]    Phillips, A., Ed. and M. Davis, Ed., "Tags for Identifying
              Languages", DOI 10.17487/RFC5646, September 2009,
              <https://www.rfc-editor.org/info/rfc5646>.

   [I-D.ietf-cellar-codec]
              Lhomme, S., Bunkus, M., and D. Rice, "Matroska Media
              Container Codec Specifications", Work in Progress,
              Internet-Draft, draft-ietf-cellar-codec-05, 19 October
              2020,
              <https://tools.ietf.org/html/draft-ietf-cellar-codec-05>.

   [I-D.ietf-cellar-tags]
              Lhomme, S., Bunkus, M., and D. Rice, "Matroska Media
              Container Tag Specifications", Work in Progress, Internet-
              Draft, draft-ietf-cellar-tags-05, 19 October 2020,
              <https://tools.ietf.org/html/draft-ietf-cellar-tags-05>.

   [IANADomains]
              "IANA Root Zone Database",
              <https://www.iana.org/domains/root/db>.

   [IANALangRegistry]
              "IANA Language Subtag Registry", 28 February 2013,
              <https://www.iana.org/assignments/language-subtag-
              registry/language-subtag-registry>.

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   [ISO3166-1]
              International Organization for Standardization, "Codes for
              the representation of names of countries and their
              subdivisions -- Part 1: Country code", ISO 3166-1:2020,
              August 2020, <https://www.iso.org/standard/72482.html>.

   [ISO639-2] United States Library Of Congress, "Codes for the
              Representation of Names of Languages", ISO 639-2:1998, 21
              December 2017, <https://www.loc.gov/standards/iso639-
              2/php/code_list.php>.

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,
              <https://www.rfc-editor.org/info/rfc2119>.

   [RFC8174]  Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
              2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
              May 2017, <https://www.rfc-editor.org/info/rfc8174>.

   [RFC8794]  Lhomme, S., Rice, D., and M. Bunkus, "Extensible Binary
              Meta Language", RFC 8794, DOI 10.17487/RFC8794, July 2020,
              <https://www.rfc-editor.org/info/rfc8794>.

   [WebVTT]   Pieters, S., Pfeiffer, S., Ed., Jägenstedt, P., and I.
              Hickson, "WebVTT Cue Identifier", 4 April 2019,
              <https://www.w3.org/TR/webvtt1/#webvtt-cue-identifier>.

28.  Informative References

   [DivXTrickTrack]
              "DivX Trick Track Extensions", 14 December 2010,
              <http://web.archive.org/web/20101222001148/
              http://labs.divx.com/node/16601>.

   [DivXWorldFonts]
              "DivX World Fonts Extensions", 14 December 2010,
              <http://web.archive.org/web/20110214132246/
              http://labs.divx.com/node/16602>.

   [MCF]      "Media Container Format", 17 July 2002,
              <http://mukoli.free.fr/mcf/mcf.html>.

Authors' Addresses

   Steve Lhomme

   Email: slhomme@matroska.org

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   Moritz Bunkus

   Email: moritz@bunkus.org

   Dave Rice

   Email: dave@dericed.com

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