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Versions: 00 01 02 03 04 05 06 07 08                     Standards Track
cellar                                                         S. Lhomme
Internet-Draft
Intended status: Standards Track                               M. Bunkus
Expires: 12 April 2022
                                                                 D. Rice
                                                          9 October 2021


             Matroska Media Container Format Specifications
                     draft-ietf-cellar-matroska-08

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-
   Drafts is at https://datatracker.ietf.org/drafts/current/.

   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 12 April 2022.

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
   and restrictions with respect to this document.  Code Components
   extracted from this document must include Simplified BSD License text
   as described in Section 4.e of the Trust Legal Provisions and are
   provided without warranty as described in the Simplified BSD License.




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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   5
   2.  Status of this document . . . . . . . . . . . . . . . . . . .   6
   3.  Security Considerations . . . . . . . . . . . . . . . . . . .   6
   4.  Notation and Conventions  . . . . . . . . . . . . . . . . . .   7
   5.  Basis in EBML . . . . . . . . . . . . . . . . . . . . . . . .   7
     5.1.  Added Constraints on EBML . . . . . . . . . . . . . . . .   7
     5.2.  Matroska Design . . . . . . . . . . . . . . . . . . . . .   8
   6.  Language Codes  . . . . . . . . . . . . . . . . . . . . . . .   8
   7.  Matroska Structure  . . . . . . . . . . . . . . . . . . . . .   8
   8.  Matroska Schema . . . . . . . . . . . . . . . . . . . . . . .  16
     8.1.  Segment Element . . . . . . . . . . . . . . . . . . . . .  16
       8.1.1.  SeekHead Element  . . . . . . . . . . . . . . . . . .  17
         8.1.1.1.  Seek Element  . . . . . . . . . . . . . . . . . .  17
       8.1.2.  Info Element  . . . . . . . . . . . . . . . . . . . .  18
         8.1.2.1.  SegmentUID Element  . . . . . . . . . . . . . . .  18
         8.1.2.2.  SegmentFilename Element . . . . . . . . . . . . .  19
         8.1.2.3.  PrevUID Element . . . . . . . . . . . . . . . . .  19
         8.1.2.4.  PrevFilename Element  . . . . . . . . . . . . . .  20
         8.1.2.5.  NextUID Element . . . . . . . . . . . . . . . . .  20
         8.1.2.6.  NextFilename Element  . . . . . . . . . . . . . .  20
         8.1.2.7.  SegmentFamily Element . . . . . . . . . . . . . .  21
         8.1.2.8.  ChapterTranslate Element  . . . . . . . . . . . .  21
         8.1.2.9.  TimestampScale Element  . . . . . . . . . . . . .  23
         8.1.2.10. Duration Element  . . . . . . . . . . . . . . . .  23
         8.1.2.11. DateUTC Element . . . . . . . . . . . . . . . . .  23
         8.1.2.12. Title Element . . . . . . . . . . . . . . . . . .  24
         8.1.2.13. MuxingApp Element . . . . . . . . . . . . . . . .  24
         8.1.2.14. WritingApp Element  . . . . . . . . . . . . . . .  25
       8.1.3.  Cluster Element . . . . . . . . . . . . . . . . . . .  25
         8.1.3.1.  Timestamp Element . . . . . . . . . . . . . . . .  25
         8.1.3.2.  Position Element  . . . . . . . . . . . . . . . .  26
         8.1.3.3.  PrevSize Element  . . . . . . . . . . . . . . . .  26
         8.1.3.4.  SimpleBlock Element . . . . . . . . . . . . . . .  26
         8.1.3.5.  BlockGroup Element  . . . . . . . . . . . . . . .  27
       8.1.4.  Tracks Element  . . . . . . . . . . . . . . . . . . .  32
         8.1.4.1.  TrackEntry Element  . . . . . . . . . . . . . . .  33
       8.1.5.  Cues Element  . . . . . . . . . . . . . . . . . . . .  89
         8.1.5.1.  CuePoint Element  . . . . . . . . . . . . . . . .  89
       8.1.6.  Attachments Element . . . . . . . . . . . . . . . . .  93
         8.1.6.1.  AttachedFile Element  . . . . . . . . . . . . . .  94
       8.1.7.  Chapters Element  . . . . . . . . . . . . . . . . . .  96
         8.1.7.1.  EditionEntry Element  . . . . . . . . . . . . . .  96
       8.1.8.  Tags Element  . . . . . . . . . . . . . . . . . . . . 105
         8.1.8.1.  Tag Element . . . . . . . . . . . . . . . . . . . 106
   9.  Matroska Element Ordering . . . . . . . . . . . . . . . . . . 113
     9.1.  Top-Level Elements  . . . . . . . . . . . . . . . . . . . 113



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     9.2.  CRC-32  . . . . . . . . . . . . . . . . . . . . . . . . . 114
     9.3.  SeekHead  . . . . . . . . . . . . . . . . . . . . . . . . 114
     9.4.  Cues (index)  . . . . . . . . . . . . . . . . . . . . . . 114
     9.5.  Info  . . . . . . . . . . . . . . . . . . . . . . . . . . 115
     9.6.  Chapters Element  . . . . . . . . . . . . . . . . . . . . 115
     9.7.  Attachments . . . . . . . . . . . . . . . . . . . . . . . 115
     9.8.  Tags  . . . . . . . . . . . . . . . . . . . . . . . . . . 115
     9.9.  Optimum layout from a muxer . . . . . . . . . . . . . . . 115
     9.10. Optimum layout after editing tags . . . . . . . . . . . . 116
     9.11. Optimum layout with Cues at the front . . . . . . . . . . 116
     9.12. Cluster Timestamp . . . . . . . . . . . . . . . . . . . . 117
   10. Unknown elements  . . . . . . . . . . . . . . . . . . . . . . 117
   11. DefaultDecodedFieldDuration . . . . . . . . . . . . . . . . . 117
   12. Block Structure . . . . . . . . . . . . . . . . . . . . . . . 118
     12.1.  Block Header . . . . . . . . . . . . . . . . . . . . . . 118
     12.2.  Block Header Flags . . . . . . . . . . . . . . . . . . . 118
     12.3.  Lacing . . . . . . . . . . . . . . . . . . . . . . . . . 119
       12.3.1.  Xiph lacing  . . . . . . . . . . . . . . . . . . . . 119
       12.3.2.  EBML lacing  . . . . . . . . . . . . . . . . . . . . 120
       12.3.3.  Fixed-size lacing  . . . . . . . . . . . . . . . . . 121
     12.4.  SimpleBlock Structure  . . . . . . . . . . . . . . . . . 121
       12.4.1.  SimpleBlock Header . . . . . . . . . . . . . . . . . 121
       12.4.2.  SimpleBlock Header Flags . . . . . . . . . . . . . . 122
       12.4.3.  Laced Data . . . . . . . . . . . . . . . . . . . . . 122
   13. Timestamps  . . . . . . . . . . . . . . . . . . . . . . . . . 123
     13.1.  Timestamp Types  . . . . . . . . . . . . . . . . . . . . 123
     13.2.  Block Timestamps . . . . . . . . . . . . . . . . . . . . 123
     13.3.  Raw Timestamp  . . . . . . . . . . . . . . . . . . . . . 124
     13.4.  TimestampScale . . . . . . . . . . . . . . . . . . . . . 124
     13.5.  TimestampScale Rounding  . . . . . . . . . . . . . . . . 124
     13.6.  TrackTimestampScale  . . . . . . . . . . . . . . . . . . 126
   14. Encryption  . . . . . . . . . . . . . . . . . . . . . . . . . 128
   15. Image Presentation  . . . . . . . . . . . . . . . . . . . . . 128
     15.1.  Cropping . . . . . . . . . . . . . . . . . . . . . . . . 128
     15.2.  Rotation . . . . . . . . . . . . . . . . . . . . . . . . 129
   16. Matroska versioning . . . . . . . . . . . . . . . . . . . . . 129
   17. MIME Types  . . . . . . . . . . . . . . . . . . . . . . . . . 130
   18. Segment Position  . . . . . . . . . . . . . . . . . . . . . . 130
     18.1.  Segment Position Exception . . . . . . . . . . . . . . . 130
     18.2.  Example of Segment Position  . . . . . . . . . . . . . . 130
   19. Linked Segments . . . . . . . . . . . . . . . . . . . . . . . 131
     19.1.  Hard Linking . . . . . . . . . . . . . . . . . . . . . . 131
     19.2.  Medium Linking . . . . . . . . . . . . . . . . . . . . . 133
       19.2.1.  Variation 1: Linked-Duration . . . . . . . . . . . . 134
       19.2.2.  Variation 2: Linked-Edition  . . . . . . . . . . . . 134
     19.3.  Soft Linking . . . . . . . . . . . . . . . . . . . . . . 134
   20. Track Flags . . . . . . . . . . . . . . . . . . . . . . . . . 134
     20.1.  Default flag . . . . . . . . . . . . . . . . . . . . . . 134



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     20.2.  Forced flag  . . . . . . . . . . . . . . . . . . . . . . 135
     20.3.  Hearing-impaired flag  . . . . . . . . . . . . . . . . . 135
     20.4.  Visual-impaired flag . . . . . . . . . . . . . . . . . . 135
     20.5.  Descriptions flag  . . . . . . . . . . . . . . . . . . . 135
     20.6.  Original flag  . . . . . . . . . . . . . . . . . . . . . 135
     20.7.  Commentary flag  . . . . . . . . . . . . . . . . . . . . 135
     20.8.  Track Operation  . . . . . . . . . . . . . . . . . . . . 136
     20.9.  Overlay Track  . . . . . . . . . . . . . . . . . . . . . 136
     20.10. Multi-planar and 3D videos . . . . . . . . . . . . . . . 136
   21. Default track selection . . . . . . . . . . . . . . . . . . . 137
     21.1.  Audio Selection  . . . . . . . . . . . . . . . . . . . . 137
     21.2.  Subtitle selection . . . . . . . . . . . . . . . . . . . 139
   22. Chapters  . . . . . . . . . . . . . . . . . . . . . . . . . . 141
     22.1.  EditionEntry . . . . . . . . . . . . . . . . . . . . . . 141
       22.1.1.  EditionFlagDefault . . . . . . . . . . . . . . . . . 141
       22.1.2.  Default Edition  . . . . . . . . . . . . . . . . . . 141
       22.1.3.  EditionFlagOrdered . . . . . . . . . . . . . . . . . 142
         22.1.3.1.  Ordered-Edition and Matroska Segment-Linking . . 143
     22.2.  ChapterAtom  . . . . . . . . . . . . . . . . . . . . . . 144
       22.2.1.  ChapterTimeStart . . . . . . . . . . . . . . . . . . 144
       22.2.2.  ChapterTimeEnd . . . . . . . . . . . . . . . . . . . 144
       22.2.3.  ChapterFlagHidden  . . . . . . . . . . . . . . . . . 144
     22.3.  Menu features  . . . . . . . . . . . . . . . . . . . . . 145
     22.4.  Physical Types . . . . . . . . . . . . . . . . . . . . . 145
     22.5.  Chapter Examples . . . . . . . . . . . . . . . . . . . . 146
       22.5.1.  Example 1 : basic chaptering . . . . . . . . . . . . 146
       22.5.2.  Example 2 : nested chapters  . . . . . . . . . . . . 148
         22.5.2.1.  The Micronauts "Bleep To Bleep"  . . . . . . . . 148
   23. Attachments . . . . . . . . . . . . . . . . . . . . . . . . . 150
     23.1.  Cover Art  . . . . . . . . . . . . . . . . . . . . . . . 151
   24. Cues  . . . . . . . . . . . . . . . . . . . . . . . . . . . . 152
     24.1.  Recommendations  . . . . . . . . . . . . . . . . . . . . 152
   25. Matroska Streaming  . . . . . . . . . . . . . . . . . . . . . 153
     25.1.  File Access  . . . . . . . . . . . . . . . . . . . . . . 153
     25.2.  Livestreaming  . . . . . . . . . . . . . . . . . . . . . 154
   26. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 154
     26.1.  Matroska Element IDs Registry  . . . . . . . . . . . . . 154
     26.2.  ChapterCodecID Registry  . . . . . . . . . . . . . . . . 154
     26.3.  Historic Deprecated Element IDs Registry . . . . . . . . 154
       26.3.1.  SilentTracks Element . . . . . . . . . . . . . . . . 155
       26.3.2.  SilentTrackNumber Element  . . . . . . . . . . . . . 155
       26.3.3.  BlockVirtual Element . . . . . . . . . . . . . . . . 155
       26.3.4.  ReferenceVirtual Element . . . . . . . . . . . . . . 155
       26.3.5.  FrameNumber Element  . . . . . . . . . . . . . . . . 156
       26.3.6.  BlockAdditionID Element  . . . . . . . . . . . . . . 156
       26.3.7.  Delay Element  . . . . . . . . . . . . . . . . . . . 156
       26.3.8.  SliceDuration Element  . . . . . . . . . . . . . . . 156
       26.3.9.  ReferenceFrame Element . . . . . . . . . . . . . . . 156



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       26.3.10. ReferenceOffset Element  . . . . . . . . . . . . . . 157
       26.3.11. ReferenceTimestamp Element . . . . . . . . . . . . . 157
       26.3.12. EncryptedBlock Element . . . . . . . . . . . . . . . 157
       26.3.13. TrackOffset Element  . . . . . . . . . . . . . . . . 157
       26.3.14. CodecSettings Element  . . . . . . . . . . . . . . . 158
       26.3.15. CodecInfoURL Element . . . . . . . . . . . . . . . . 158
       26.3.16. CodecDownloadURL Element . . . . . . . . . . . . . . 158
       26.3.17. CodecDecodeAll Element . . . . . . . . . . . . . . . 158
       26.3.18. OldStereoMode Element  . . . . . . . . . . . . . . . 158
       26.3.19. AspectRatioType Element  . . . . . . . . . . . . . . 159
       26.3.20. GammaValue Element . . . . . . . . . . . . . . . . . 159
       26.3.21. FrameRate Element  . . . . . . . . . . . . . . . . . 159
       26.3.22. ChannelPositions Element . . . . . . . . . . . . . . 159
       26.3.23. TrickTrackUID Element  . . . . . . . . . . . . . . . 160
       26.3.24. TrickTrackSegmentUID Element . . . . . . . . . . . . 160
       26.3.25. TrickTrackFlag Element . . . . . . . . . . . . . . . 160
       26.3.26. TrickMasterTrackUID Element  . . . . . . . . . . . . 160
       26.3.27. TrickMasterTrackSegmentUID Element . . . . . . . . . 161
       26.3.28. ContentSignature Element . . . . . . . . . . . . . . 161
       26.3.29. ContentSigKeyID Element  . . . . . . . . . . . . . . 161
       26.3.30. ContentSigAlgo Element . . . . . . . . . . . . . . . 161
       26.3.31. ContentSigHashAlgo Element . . . . . . . . . . . . . 162
       26.3.32. CueRefCluster Element  . . . . . . . . . . . . . . . 162
       26.3.33. CueRefNumber Element . . . . . . . . . . . . . . . . 162
       26.3.34. CueRefCodecState Element . . . . . . . . . . . . . . 162
       26.3.35. FileReferral Element . . . . . . . . . . . . . . . . 163
       26.3.36. FileUsedStartTime Element  . . . . . . . . . . . . . 163
       26.3.37. FileUsedEndTime Element  . . . . . . . . . . . . . . 163
       26.3.38. TagDefaultBogus Element  . . . . . . . . . . . . . . 163
   27. Normative References  . . . . . . . . . . . . . . . . . . . . 164
   28. Informative References  . . . . . . . . . . . . . . . . . . . 165
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . . 166

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.  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.

5.  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).

5.1.  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".

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

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




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5.2.  Matroska Design

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

6.  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.

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



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   *  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.

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

                 Figure 1: Basic layout of a Matroska file.

   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 |
   +--------------------------------+



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              Figure 2: 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.

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

    Figure 3: 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



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   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.

   +------------------------------------+
   | 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          |
   |--------------------------------------------------------|



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

   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 5: 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 6: 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 7: 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
   the Timestamp Element in the Cluster.  For example, if the Timestamp



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   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 8: 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 9: 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 10: 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.  Segment Element

   name:  Segment

   path:  \Segment

   id:  0x18538067

   minOccurs:  1




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   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.

8.1.1.  SeekHead Element

   name:  SeekHead

   path:  \Segment\SeekHead

   id:  0x114D9B74

   maxOccurs:  2

   type:  master

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

8.1.1.1.  Seek Element

   name:  Seek

   path:  \Segment\SeekHead\Seek

   id:  0x4DBB

   minOccurs:  1

   type:  master

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

8.1.1.1.1.  SeekID Element

   name:  SeekID

   path:  \Segment\SeekHead\Seek\SeekID

   id:  0x53AB

   minOccurs:  1



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   maxOccurs:  1

   type:  binary

   definition:  The binary ID corresponding to the Element name.

8.1.1.1.2.  SeekPosition Element

   name:  SeekPosition

   path:  \Segment\SeekHead\Seek\SeekPosition

   id:  0x53AC

   minOccurs:  1

   maxOccurs:  1

   type:  uinteger

   definition:  The Segment Position of the Element.

8.1.2.  Info Element

   name:  Info

   path:  \Segment\Info

   id:  0x1549A966

   minOccurs:  1

   maxOccurs:  1

   type:  master

   recurring:  1

   definition:  Contains general information about the Segment.

8.1.2.1.  SegmentUID Element

   name:  SegmentUID

   path:  \Segment\Info\SegmentUID

   id:  0x73A4




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   maxOccurs:  1

   range:  not 0

   type:  binary

   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.

8.1.2.2.  SegmentFilename Element

   name:  SegmentFilename

   path:  \Segment\Info\SegmentFilename

   id:  0x7384

   maxOccurs:  1

   type:  utf-8

   definition:  A filename corresponding to this Segment.

8.1.2.3.  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.





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8.1.2.4.  PrevFilename Element

   name:  PrevFilename

   path:  \Segment\Info\PrevFilename

   id:  0x3C83AB

   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.

8.1.2.5.  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.

8.1.2.6.  NextFilename Element

   name:  NextFilename

   path:  \Segment\Info\NextFilename

   id:  0x3E83BB




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

8.1.2.7.  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.

8.1.2.8.  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.

8.1.2.8.1.  ChapterTranslateEditionUID Element

   name:  ChapterTranslateEditionUID

   path:  \Segment\Info\ChapterTranslate\ChapterTranslateEditionUID

   id:  0x69FC




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   type:  uinteger

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

8.1.2.8.2.  ChapterTranslateCodec Element

   name:  ChapterTranslateCodec

   path:  \Segment\Info\ChapterTranslate\ChapterTranslateCodec

   id:  0x69BF

   minOccurs:  1

   maxOccurs:  1

   type:  uinteger

   definition:  The chapter codec; see Section 8.1.7.1.4.15.

   restrictions:

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

                                  Table 1:
                           ChapterTranslateCodec
                                   values

8.1.2.8.3.  ChapterTranslateID Element

   name:  ChapterTranslateID

   path:  \Segment\Info\ChapterTranslate\ChapterTranslateID

   id:  0x69A5

   minOccurs:  1

   maxOccurs:  1




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   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 8.1.7.1.4.15.

8.1.2.9.  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).

8.1.2.10.  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.

8.1.2.11.  DateUTC Element

   name:  DateUTC




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   path:  \Segment\Info\DateUTC

   id:  0x4461

   maxOccurs:  1

   type:  date

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

8.1.2.12.  Title Element

   name:  Title

   path:  \Segment\Info\Title

   id:  0x7BA9

   maxOccurs:  1

   type:  utf-8

   definition:  General name of the Segment.

8.1.2.13.  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.







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8.1.2.14.  WritingApp Element

   name:  WritingApp

   path:  \Segment\Info\WritingApp

   id:  0x5741

   minOccurs:  1

   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.

8.1.3.  Cluster Element

   name:  Cluster

   path:  \Segment\Cluster

   id:  0x1F43B675

   type:  master

   unknownsizeallowed:  1

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

8.1.3.1.  Timestamp Element

   name:  Timestamp

   path:  \Segment\Cluster\Timestamp

   id:  0xE7

   minOccurs:  1

   maxOccurs:  1

   type:  uinteger




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

8.1.3.2.  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.

8.1.3.3.  PrevSize Element

   name:  PrevSize

   path:  \Segment\Cluster\PrevSize

   id:  0xAB

   maxOccurs:  1

   type:  uinteger

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

8.1.3.4.  SimpleBlock Element

   name:  SimpleBlock

   path:  \Segment\Cluster\SimpleBlock

   id:  0xA3

   type:  binary

   minver:  2

   definition:  Similar to Block, see Section 12, but without all the




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      extra information, mostly used to reduced overhead when no extra
      feature is needed; see Section 12.4 on SimpleBlock Structure.

8.1.3.5.  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.

8.1.3.5.1.  Block Element

   name:  Block

   path:  \Segment\Cluster\BlockGroup\Block

   id:  0xA1

   minOccurs:  1

   maxOccurs:  1

   type:  binary

   definition:  Block containing the actual data to be rendered and a
      timestamp relative to the Cluster Timestamp; see Section 12 on
      Block Structure.

8.1.3.5.2.  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




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      EBML parser that has no knowledge of the Block structure could
      still see and use/skip these data.

8.1.3.5.2.1.  BlockMore Element

   name:  BlockMore

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

   id:  0xA6

   minOccurs:  1

   type:  master

   definition:  Contain the BlockAdditional and some parameters.

8.1.3.5.2.2.  BlockAddID Element

   name:  BlockAddID

   path:  \Segment\Cluster\BlockGroup\BlockAdditions\BlockMore\BlockAddI
      D

   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.

8.1.3.5.2.3.  BlockAdditional Element

   name:  BlockAdditional

   path:  \Segment\Cluster\BlockGroup\BlockAdditions\BlockMore\BlockAddi
      tional




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   id:  0xA5

   minOccurs:  1

   maxOccurs:  1

   type:  binary

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

8.1.3.5.3.  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.

   notes:

















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     +===========+===================================================+
     | 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 |
     |           | timestampof this Block and the timestamp of the   |
     |           | next Block in "display" order (not coding order). |
     +-----------+---------------------------------------------------+

                Table 2: BlockDuration implementation notes

8.1.3.5.4.  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.

8.1.3.5.5.  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




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      P frame).  The timestamp is relative to the block it's attached
      to.

8.1.3.5.6.  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.

8.1.3.5.7.  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.

8.1.3.5.8.  Slices Element

   name:  Slices

   path:  \Segment\Cluster\BlockGroup\Slices

   id:  0x8E



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   maxOccurs:  1

   type:  master

   maxver:  1

   definition:  Contains slices description.

8.1.3.5.8.1.  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.

8.1.3.5.8.2.  LaceNumber Element

   name:  LaceNumber

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

   id:  0xCC

   maxOccurs:  1

   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.

8.1.4.  Tracks Element

   name:  Tracks

   path:  \Segment\Tracks




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   id:  0x1654AE6B

   maxOccurs:  1

   type:  master

   recurring:  1

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

8.1.4.1.  TrackEntry Element

   name:  TrackEntry

   path:  \Segment\Tracks\TrackEntry

   id:  0xAE

   minOccurs:  1

   type:  master

   definition:  Describes a track with all Elements.

8.1.4.1.1.  TrackNumber Element

   name:  TrackNumber

   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).







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8.1.4.1.2.  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.

   usage notes:  The value of this Element SHOULD be kept the same when
      making a direct stream copy to another file.

8.1.4.1.3.  TrackType Element

   name:  TrackType

   path:  \Segment\Tracks\TrackEntry\TrackType

   id:  0x83

   minOccurs:  1

   maxOccurs:  1

   type:  uinteger

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

   restrictions:













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

                         Table 3: TrackType values

8.1.4.1.4.  FlagEnabled Element

   name:  FlagEnabled

   path:  \Segment\Tracks\TrackEntry\FlagEnabled

   id:  0xB9

   minOccurs:  1

   maxOccurs:  1

   range:  0-1

   default:  1

   type:  uinteger

   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.






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8.1.4.1.5.  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 21 for
      more details.

8.1.4.1.6.  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
      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 21 for more details.





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8.1.4.1.7.  FlagHearingImpaired Element

   name:  FlagHearingImpaired

   path:  \Segment\Tracks\TrackEntry\FlagHearingImpaired

   id:  0x55AB

   maxOccurs:  1

   range:  0-1

   type:  uinteger

   minver:  4

   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.

8.1.4.1.8.  FlagVisualImpaired Element

   name:  FlagVisualImpaired

   path:  \Segment\Tracks\TrackEntry\FlagVisualImpaired

   id:  0x55AC

   maxOccurs:  1

   range:  0-1

   type:  uinteger

   minver:  4

   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.

8.1.4.1.9.  FlagTextDescriptions Element

   name:  FlagTextDescriptions

   path:  \Segment\Tracks\TrackEntry\FlagTextDescriptions

   id:  0x55AD




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   maxOccurs:  1

   range:  0-1

   type:  uinteger

   minver:  4

   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.

8.1.4.1.10.  FlagOriginal Element

   name:  FlagOriginal

   path:  \Segment\Tracks\TrackEntry\FlagOriginal

   id:  0x55AE

   maxOccurs:  1

   range:  0-1

   type:  uinteger

   minver:  4

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

8.1.4.1.11.  FlagCommentary Element

   name:  FlagCommentary

   path:  \Segment\Tracks\TrackEntry\FlagCommentary

   id:  0x55AF

   maxOccurs:  1

   range:  0-1

   type:  uinteger

   minver:  4

   definition:  Set to 1 if that track contains commentary, set to 0 if



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      it does not contain commentary.

8.1.4.1.12.  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.

8.1.4.1.13.  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.

8.1.4.1.14.  MaxCache Element

   name:  MaxCache

   path:  \Segment\Tracks\TrackEntry\MaxCache




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   id:  0x6DF8

   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.

8.1.4.1.15.  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).

8.1.4.1.16.  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 11 for more information





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8.1.4.1.17.  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).

8.1.4.1.18.  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 8.1.3.5.2.2).
      A value 0 means there is no BlockAdditions (Section 8.1.3.5.2) for
      this track.

8.1.4.1.19.  BlockAdditionMapping Element

   name:  BlockAdditionMapping




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   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 8.1.3.5.2.2), or to the track as a whole with
      BlockAddIDExtraData.

8.1.4.1.19.1.  BlockAddIDValue Element

   name:  BlockAddIDValue

   path:  \Segment\Tracks\TrackEntry\BlockAdditionMapping\BlockAddIDValu
      e

   id:  0x41F0

   maxOccurs:  1

   range:  >=2

   type:  uinteger

   minver:  4

   definition:  If the track format extension needs content beside
      frames, the value refers to the BlockAddID (Section 8.1.3.5.2.2),
      value being described.  To keep MaxBlockAdditionID as low as
      possible, small values SHOULD be used.

8.1.4.1.19.2.  BlockAddIDName Element

   name:  BlockAddIDName

   path:  \Segment\Tracks\TrackEntry\BlockAdditionMapping\BlockAddIDName

   id:  0x41A4

   maxOccurs:  1

   type:  string

   minver:  4



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

8.1.4.1.19.3.  BlockAddIDType Element

   name:  BlockAddIDType

   path:  \Segment\Tracks\TrackEntry\BlockAdditionMapping\BlockAddIDType

   id:  0x41E7

   minOccurs:  1

   maxOccurs:  1

   default:  0

   type:  uinteger

   minver:  4

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

8.1.4.1.19.4.  BlockAddIDExtraData Element

   name:  BlockAddIDExtraData

   path:  \Segment\Tracks\TrackEntry\BlockAdditionMapping\BlockAddIDExtr
      aData

   id:  0x41ED

   maxOccurs:  1

   type:  binary

   minver:  4

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







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8.1.4.1.20.  Name Element

   name:  Name

   path:  \Segment\Tracks\TrackEntry\Name

   id:  0x536E

   maxOccurs:  1

   type:  utf-8

   definition:  A human-readable track name.

8.1.4.1.21.  Language Element

   name:  Language

   path:  \Segment\Tracks\TrackEntry\Language

   id:  0x22B59C

   minOccurs:  1

   maxOccurs:  1

   default:  eng

   type:  string

   definition:  Specifies the language of the track in the Matroska
      languages form; see Section 6 on language codes.  This Element
      MUST be ignored if the LanguageIETF Element is used in the same
      TrackEntry.

8.1.4.1.22.  LanguageIETF Element

   name:  LanguageIETF

   path:  \Segment\Tracks\TrackEntry\LanguageIETF

   id:  0x22B59D

   maxOccurs:  1

   type:  string

   minver:  4



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   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.

8.1.4.1.23.  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 [MatroskaCodec]
      for more info.

8.1.4.1.24.  CodecPrivate Element

   name:  CodecPrivate

   path:  \Segment\Tracks\TrackEntry\CodecPrivate

   id:  0x63A2

   maxOccurs:  1

   type:  binary

   definition:  Private data only known to the codec.

8.1.4.1.25.  CodecName Element

   name:  CodecName

   path:  \Segment\Tracks\TrackEntry\CodecName

   id:  0x258688

   maxOccurs:  1

   type:  utf-8




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   definition:  A human-readable string specifying the codec.

8.1.4.1.26.  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.

8.1.4.1.27.  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 26.3.1 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.

8.1.4.1.28.  CodecDelay Element

   name:  CodecDelay

   path:  \Segment\Tracks\TrackEntry\CodecDelay

   id:  0x56AA

   maxOccurs:  1

   type:  uinteger



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   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.

8.1.4.1.29.  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.

8.1.4.1.30.  TrackTranslate Element

   name:  TrackTranslate

   path:  \Segment\Tracks\TrackEntry\TrackTranslate

   id:  0x6624

   type:  master

   definition:  The track identification for the given Chapter Codec.

8.1.4.1.30.1.  TrackTranslateEditionUID Element

   name:  TrackTranslateEditionUID

   path:  \Segment\Tracks\TrackEntry\TrackTranslate\TrackTranslateEditio
      nUID



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   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.

8.1.4.1.30.2.  TrackTranslateCodec Element

   name:  TrackTranslateCodec

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

   id:  0x66BF

   minOccurs:  1

   maxOccurs:  1

   type:  uinteger

   definition:  The chapter codec; see Section 8.1.7.1.4.15.

   restrictions:

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

                                  Table 4:
                            TrackTranslateCodec
                                   values

8.1.4.1.30.3.  TrackTranslateTrackID Element

   name:  TrackTranslateTrackID

   path:  \Segment\Tracks\TrackEntry\TrackTranslate\TrackTranslateTrackI
      D

   id:  0x66A5

   minOccurs:  1



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   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 8.1.7.1.4.15.

8.1.4.1.31.  Video Element

   name:  Video

   path:  \Segment\Tracks\TrackEntry\Video

   id:  0xE0

   maxOccurs:  1

   type:  master

   definition:  Video settings.

8.1.4.1.31.1.  FlagInterlaced Element

   name:  FlagInterlaced

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

   id:  0x9A

   minOccurs:  1

   maxOccurs:  1

   default:  0

   type:  uinteger

   minver:  2

   definition:  Specify whether the video frames in this track are
      interlaced or not.

   defined values:







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            +=======+==============+==========================+
            | value | label        | definition               |
            +=======+==============+==========================+
            | 0     | undetermined | Unknown status.This      |
            |       |              | value SHOULD be avoided. |
            +-------+--------------+--------------------------+
            | 1     | interlaced   | Interlaced frames.       |
            +-------+--------------+--------------------------+
            | 2     | progressive  | No interlacing.          |
            +-------+--------------+--------------------------+

                       Table 5: FlagInterlaced values

8.1.4.1.31.2.  FieldOrder Element

   name:  FieldOrder

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

   id:  0x9D

   minOccurs:  1

   maxOccurs:  1

   default:  2

   type:  uinteger

   minver:  4

   definition:  Specify the field ordering of video frames in this
      track.

   usage notes:  If FlagInterlaced is not set to 1, this Element MUST be
      ignored.

   defined values:













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   +===============+==============+====================================+
   | value         | label        | definition                         |
   +===============+==============+====================================+
   | 0             | progressive  | Interlaced frames.This             |
   |               |              | value SHOULD be avoided,           |
   |               |              | setting FlagInterlaced             |
   |               |              | to 2 is sufficient.                |
   +---------------+--------------+------------------------------------+
   | 1             | tff          | Top field displayed                |
   |               |              | first.  Top field stored           |
   |               |              | first.                             |
   +---------------+--------------+------------------------------------+
   | 2             | undetermined | Unknown field order.This           |
   |               |              | value SHOULD be avoided.           |
   +---------------+--------------+------------------------------------+
   | 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 6: FieldOrder values

8.1.4.1.31.3.  StereoMode Element

   name:  StereoMode

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

   id:  0x53B8




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   minOccurs:  1

   maxOccurs:  1

   default:  0

   type:  uinteger

   minver:  3

   definition:  Stereo-3D video mode.  There are some more details in
      Section 20.10.

   restrictions:





































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       +=======+===================================================+
       | 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 7: StereoMode values

8.1.4.1.31.4.  AlphaMode Element

   name:  AlphaMode

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

   id:  0x53C0

   maxOccurs:  1

   default:  0




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   type:  uinteger

   minver:  3

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

8.1.4.1.31.5.  PixelWidth Element

   name:  PixelWidth

   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.

8.1.4.1.31.6.  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.

8.1.4.1.31.7.  PixelCropBottom Element

   name:  PixelCropBottom

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



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   id:  0x54AA

   maxOccurs:  1

   default:  0

   type:  uinteger

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

8.1.4.1.31.8.  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.

8.1.4.1.31.9.  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.







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8.1.4.1.31.10.  PixelCropRight Element

   name:  PixelCropRight

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

   id:  0x54DD

   maxOccurs:  1

   default:  0

   type:  uinteger

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

8.1.4.1.31.11.  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).

   notes:

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

                 Table 8: DisplayWidth implementation notes



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8.1.4.1.31.12.  DisplayHeight Element

   name:  DisplayHeight

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

   id:  0x54BA

   maxOccurs:  1

   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).

   notes:

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

               Table 9: DisplayHeight implementation notes

8.1.4.1.31.13.  DisplayUnit Element

   name:  DisplayUnit

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

   id:  0x54B2

   minOccurs:  1

   maxOccurs:  1

   default:  0

   type:  uinteger




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   definition:  How DisplayWidth & DisplayHeight are interpreted.

   restrictions:

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

                       Table 10: DisplayUnit values

8.1.4.1.31.14.  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.

   notes:












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

                Table 11: ColourSpace implementation notes

8.1.4.1.31.15.  Colour Element

   name:  Colour

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

   id:  0x55B0

   maxOccurs:  1

   type:  master

   minver:  4

   definition:  Settings describing the colour format.

8.1.4.1.31.16.  MatrixCoefficients Element

   name:  MatrixCoefficients

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

   id:  0x55B1

   minOccurs:  1

   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.



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   restrictions:

             +=======+=======================================+
             | 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 12: MatrixCoefficients values

8.1.4.1.31.17.  BitsPerChannel Element

   name:  BitsPerChannel

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

   id:  0x55B2

   maxOccurs:  1




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   default:  0

   type:  uinteger

   minver:  4

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

8.1.4.1.31.18.  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.

8.1.4.1.31.19.  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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8.1.4.1.31.20.  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.

8.1.4.1.31.21.  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.

8.1.4.1.31.22.  ChromaSitingHorz Element

   name:  ChromaSitingHorz

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

   id:  0x55B7

   minOccurs:  1




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   maxOccurs:  1

   default:  0

   type:  uinteger

   minver:  4

   definition:  How chroma is subsampled horizontally.

   restrictions:

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

                                 Table 13:
                          ChromaSitingHorz values

8.1.4.1.31.23.  ChromaSitingVert Element

   name:  ChromaSitingVert

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

   id:  0x55B8

   minOccurs:  1

   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 14:
                             ChromaSitingVert
                                  values

8.1.4.1.31.24.  Range Element

   name:  Range

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

   id:  0x55B9

   minOccurs:  1

   maxOccurs:  1

   default:  0

   type:  uinteger

   minver:  4

   definition:  Clipping of the color ranges.

   restrictions:
















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

                           Table 15: Range values

8.1.4.1.31.25.  TransferCharacteristics Element

   name:  TransferCharacteristics

   path:  \Segment\Tracks\TrackEntry\Video\Colour\TransferCharacteristic
      s

   id:  0x55BA

   minOccurs:  1

   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 16: TransferCharacteristics values

8.1.4.1.31.26.  Primaries Element

   name:  Primaries




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

   id:  0x55BB

   minOccurs:  1

   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 17: Primaries values

8.1.4.1.31.27.  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).

8.1.4.1.31.28.  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).

8.1.4.1.31.29.  MasteringMetadata Element

   name:  MasteringMetadata

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

   id:  0x55D0

   maxOccurs:  1

   type:  master

   minver:  4

   definition:  SMPTE 2086 mastering data.

8.1.4.1.31.30.  PrimaryRChromaticityX Element

   name:  PrimaryRChromaticityX

   path:  \Segment\Tracks\TrackEntry\Video\Colour\MasteringMetadata\Prim
      aryRChromaticityX

   id:  0x55D1

   maxOccurs:  1

   range:  0-1



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   type:  float

   minver:  4

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

8.1.4.1.31.31.  PrimaryRChromaticityY Element

   name:  PrimaryRChromaticityY

   path:  \Segment\Tracks\TrackEntry\Video\Colour\MasteringMetadata\Prim
      aryRChromaticityY

   id:  0x55D2

   maxOccurs:  1

   range:  0-1

   type:  float

   minver:  4

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

8.1.4.1.31.32.  PrimaryGChromaticityX Element

   name:  PrimaryGChromaticityX

   path:  \Segment\Tracks\TrackEntry\Video\Colour\MasteringMetadata\Prim
      aryGChromaticityX

   id:  0x55D3

   maxOccurs:  1

   range:  0-1

   type:  float

   minver:  4

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

8.1.4.1.31.33.  PrimaryGChromaticityY Element

   name:  PrimaryGChromaticityY




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   path:  \Segment\Tracks\TrackEntry\Video\Colour\MasteringMetadata\Prim
      aryGChromaticityY

   id:  0x55D4

   maxOccurs:  1

   range:  0-1

   type:  float

   minver:  4

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

8.1.4.1.31.34.  PrimaryBChromaticityX Element

   name:  PrimaryBChromaticityX

   path:  \Segment\Tracks\TrackEntry\Video\Colour\MasteringMetadata\Prim
      aryBChromaticityX

   id:  0x55D5

   maxOccurs:  1

   range:  0-1

   type:  float

   minver:  4

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

8.1.4.1.31.35.  PrimaryBChromaticityY Element

   name:  PrimaryBChromaticityY

   path:  \Segment\Tracks\TrackEntry\Video\Colour\MasteringMetadata\Prim
      aryBChromaticityY

   id:  0x55D6

   maxOccurs:  1

   range:  0-1

   type:  float



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   minver:  4

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

8.1.4.1.31.36.  WhitePointChromaticityX Element

   name:  WhitePointChromaticityX

   path:  \Segment\Tracks\TrackEntry\Video\Colour\MasteringMetadata\Whit
      ePointChromaticityX

   id:  0x55D7

   maxOccurs:  1

   range:  0-1

   type:  float

   minver:  4

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

8.1.4.1.31.37.  WhitePointChromaticityY Element

   name:  WhitePointChromaticityY

   path:  \Segment\Tracks\TrackEntry\Video\Colour\MasteringMetadata\Whit
      ePointChromaticityY

   id:  0x55D8

   maxOccurs:  1

   range:  0-1

   type:  float

   minver:  4

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

8.1.4.1.31.38.  LuminanceMax Element

   name:  LuminanceMax

   path:  \Segment\Tracks\TrackEntry\Video\Colour\MasteringMetadata\Lumi
      nanceMax



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   id:  0x55D9

   maxOccurs:  1

   range:  >= 0x0p+0

   type:  float

   minver:  4

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

8.1.4.1.31.39.  LuminanceMin Element

   name:  LuminanceMin

   path:  \Segment\Tracks\TrackEntry\Video\Colour\MasteringMetadata\Lumi
      nanceMin

   id:  0x55DA

   maxOccurs:  1

   range:  >= 0x0p+0

   type:  float

   minver:  4

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

8.1.4.1.31.40.  Projection Element

   name:  Projection

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

   id:  0x7670

   maxOccurs:  1

   type:  master

   minver:  4

   definition:  Describes the video projection details.  Used to render



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      spherical and VR videos.

8.1.4.1.31.41.  ProjectionType Element

   name:  ProjectionType

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

   id:  0x7671

   minOccurs:  1

   maxOccurs:  1

   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 18:
                           ProjectionType values

8.1.4.1.31.42.  ProjectionPrivate Element

   name:  ProjectionPrivate

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

   id:  0x7672

   maxOccurs:  1



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   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.

8.1.4.1.31.43.  ProjectionPoseYaw Element

   name:  ProjectionPoseYaw

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

   id:  0x7673

   minOccurs:  1

   maxOccurs:  1

   default:  0x0p+0

   type:  float

   minver:  4

   definition:  Specifies a yaw rotation to the projection.






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   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.

8.1.4.1.31.44.  ProjectionPosePitch Element

   name:  ProjectionPosePitch

   path:  \Segment\Tracks\TrackEntry\Video\Projection\ProjectionPosePitc
      h

   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.

8.1.4.1.31.45.  ProjectionPoseRoll Element

   name:  ProjectionPoseRoll

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

   id:  0x7675

   minOccurs:  1

   maxOccurs:  1

   default:  0x0p+0

   type:  float




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   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.

8.1.4.1.32.  Audio Element

   name:  Audio

   path:  \Segment\Tracks\TrackEntry\Audio

   id:  0xE1

   maxOccurs:  1

   type:  master

   definition:  Audio settings.

8.1.4.1.32.1.  SamplingFrequency Element

   name:  SamplingFrequency

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

   id:  0xB5

   minOccurs:  1

   maxOccurs:  1

   range:  > 0x0p+0

   default:  0x1.f4p+12

   type:  float

   definition:  Sampling frequency in Hz.

8.1.4.1.32.2.  OutputSamplingFrequency Element

   name:  OutputSamplingFrequency

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



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   id:  0x78B5

   maxOccurs:  1

   range:  > 0x0p+0

   default: see implementation notes

   type:  float

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

   notes:

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

          Table 19: OutputSamplingFrequency implementation notes

8.1.4.1.32.3.  Channels Element

   name:  Channels

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

   id:  0x9F

   minOccurs:  1

   maxOccurs:  1

   range:  not 0

   default:  1

   type:  uinteger

   definition:  Numbers of channels in the track.

8.1.4.1.32.4.  BitDepth Element

   name:  BitDepth




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

   id:  0x6264

   maxOccurs:  1

   range:  not 0

   type:  uinteger

   definition:  Bits per sample, mostly used for PCM.

8.1.4.1.33.  TrackOperation Element

   name:  TrackOperation

   path:  \Segment\Tracks\TrackEntry\TrackOperation

   id:  0xE2

   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 20.8.

8.1.4.1.33.1.  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






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8.1.4.1.33.2.  TrackPlane Element

   name:  TrackPlane

   path:  \Segment\Tracks\TrackEntry\TrackOperation\TrackCombinePlanes\T
      rackPlane

   id:  0xE4

   minOccurs:  1

   type:  master

   minver:  3

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

8.1.4.1.33.3.  TrackPlaneUID Element

   name:  TrackPlaneUID

   path:  \Segment\Tracks\TrackEntry\TrackOperation\TrackCombinePlanes\T
      rackPlane\TrackPlaneUID

   id:  0xE5

   minOccurs:  1

   maxOccurs:  1

   range:  not 0

   type:  uinteger

   minver:  3

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

8.1.4.1.33.4.  TrackPlaneType Element

   name:  TrackPlaneType

   path:  \Segment\Tracks\TrackEntry\TrackOperation\TrackCombinePlanes\T
      rackPlane\TrackPlaneType

   id:  0xE6




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   minOccurs:  1

   maxOccurs:  1

   type:  uinteger

   minver:  3

   definition:  The kind of plane this track corresponds to.

   restrictions:

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

                                 Table 20:
                           TrackPlaneType values

8.1.4.1.33.5.  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

8.1.4.1.33.6.  TrackJoinUID Element

   name:  TrackJoinUID

   path:  \Segment\Tracks\TrackEntry\TrackOperation\TrackJoinBlocks\Trac
      kJoinUID



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   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.

8.1.4.1.34.  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.

8.1.4.1.34.1.  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.

8.1.4.1.34.2.  ContentEncodingOrder Element

   name:  ContentEncodingOrder

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



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      ntentEncodingOrder

   id:  0x5031

   minOccurs:  1

   maxOccurs:  1

   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.

8.1.4.1.34.3.  ContentEncodingScope Element

   name:  ContentEncodingScope

   path:  \Segment\Tracks\TrackEntry\ContentEncodings\ContentEncoding\Co
      ntentEncodingScope

   id:  0x5032

   minOccurs:  1

   maxOccurs:  1

   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:











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         +=======+===============================================+
         | 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 21: ContentEncodingScope values

8.1.4.1.34.4.  ContentEncodingType Element

   name:  ContentEncodingType

   path:  \Segment\Tracks\TrackEntry\ContentEncodings\ContentEncoding\Co
      ntentEncodingType

   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 22:
                            ContentEncodingType
                                   values




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8.1.4.1.34.5.  ContentCompression Element

   name:  ContentCompression

   path:  \Segment\Tracks\TrackEntry\ContentEncodings\ContentEncoding\Co
      ntentCompression

   id:  0x5034

   maxOccurs:  1

   type:  master

   definition:  Settings describing the compression used.  This Element
      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.

8.1.4.1.34.6.  ContentCompAlgo Element

   name:  ContentCompAlgo

   path:  \Segment\Tracks\TrackEntry\ContentEncodings\ContentEncoding\Co
      ntentCompression\ContentCompAlgo

   id:  0x4254

   minOccurs:  1

   maxOccurs:  1

   default:  0

   type:  uinteger

   definition:  The compression algorithm used.

   defined values:













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       +=======+===========+======================================+
       | value | label     | definition                           |
       +=======+===========+======================================+
       | 0     | zlib      | zlib compression [RFC1950].          |
       +-------+-----------+--------------------------------------+
       | 1     | bzlib     | bzip2 compression [BZIP2].           |
       +-------+-----------+--------------------------------------+
       | 2     | lzo1x     | Lempel– (U+2013)Ziv–                 |
       |       |           | (U+2013)Oberhumer compression [LZO]. |
       +-------+-----------+--------------------------------------+
       | 3     | Header    | Octets in ContentCompSettings        |
       |       | Stripping | (Section 8.1.4.1.34.7) have been     |
       |       |           | stripped from each frame.            |
       +-------+-----------+--------------------------------------+

                     Table 23: ContentCompAlgo values

8.1.4.1.34.7.  ContentCompSettings Element

   name:  ContentCompSettings

   path:  \Segment\Tracks\TrackEntry\ContentEncodings\ContentEncoding\Co
      ntentCompression\ContentCompSettings

   id:  0x4255

   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.

8.1.4.1.34.8.  ContentEncryption Element

   name:  ContentEncryption

   path:  \Segment\Tracks\TrackEntry\ContentEncodings\ContentEncoding\Co
      ntentEncryption

   id:  0x5035

   maxOccurs:  1

   type:  master

   definition:  Settings describing the encryption used.  This Element



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      MUST be present if the value of ContentEncodingType is 1
      (encryption) and MUST be ignored otherwise.

8.1.4.1.34.9.  ContentEncAlgo Element

   name:  ContentEncAlgo

   path:  \Segment\Tracks\TrackEntry\ContentEncodings\ContentEncoding\Co
      ntentEncryption\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.

   defined values:

          +=======+===============+============================+
          | value | label         | definition                 |
          +=======+===============+============================+
          | 0     | Not encrypted |                            |
          +-------+---------------+----------------------------+
          | 1     | DES           | Data Encryption Standard   |
          |       |               | (DES) [FIPS.46-3].         |
          +-------+---------------+----------------------------+
          | 2     | 3DES          | Triple Data Encryption     |
          |       |               | Algorithm [RFC1851].       |
          +-------+---------------+----------------------------+
          | 3     | Twofish       | Twofish Encryption         |
          |       |               | Algorithm [Twofish].       |
          +-------+---------------+----------------------------+
          | 4     | Blowfish      | Blowfish Encryption        |
          |       |               | Algorithm [Blowfish].      |
          +-------+---------------+----------------------------+
          | 5     | AES           | Advanced Encryption        |
          |       |               | Standard (AES) [FIPS.197]. |
          +-------+---------------+----------------------------+

                     Table 24: ContentEncAlgo values




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8.1.4.1.34.10.  ContentEncKeyID Element

   name:  ContentEncKeyID

   path:  \Segment\Tracks\TrackEntry\ContentEncodings\ContentEncoding\Co
      ntentEncryption\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.

8.1.4.1.34.11.  ContentEncAESSettings Element

   name:  ContentEncAESSettings

   path:  \Segment\Tracks\TrackEntry\ContentEncodings\ContentEncoding\Co
      ntentEncryption\ContentEncAESSettings

   id:  0x47E7

   maxOccurs:  1

   type:  master

   minver:  4

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

8.1.4.1.34.12.  AESSettingsCipherMode Element

   name:  AESSettingsCipherMode

   path:  \Segment\Tracks\TrackEntry\ContentEncodings\ContentEncoding\Co
      ntentEncryption\ContentEncAESSettings\AESSettingsCipherMode

   id:  0x47E8

   minOccurs:  1

   maxOccurs:  1

   type:  uinteger



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   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 25: AESSettingsCipherMode values

8.1.5.  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.

   notes:

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

                   Table 26: Cues implementation notes

8.1.5.1.  CuePoint Element

   name:  CuePoint




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   path:  \Segment\Cues\CuePoint

   id:  0xBB

   minOccurs:  1

   type:  master

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

8.1.5.1.1.  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.

8.1.5.1.2.  CueTrackPositions Element

   name:  CueTrackPositions

   path:  \Segment\Cues\CuePoint\CueTrackPositions

   id:  0xB7

   minOccurs:  1

   type:  master

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

8.1.5.1.2.1.  CueTrack Element

   name:  CueTrack

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




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   id:  0xF7

   minOccurs:  1

   maxOccurs:  1

   range:  not 0

   type:  uinteger

   definition:  The track for which a position is given.

8.1.5.1.2.2.  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.

8.1.5.1.2.3.  CueRelativePosition Element

   name:  CueRelativePosition

   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.





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8.1.5.1.2.4.  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.

8.1.5.1.2.5.  CueBlockNumber Element

   name:  CueBlockNumber

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

   id:  0x5378

   maxOccurs:  1

   range:  not 0

   type:  uinteger

   definition:  Number of the Block in the specified Cluster.

8.1.5.1.2.6.  CueCodecState Element

   name:  CueCodecState

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

   id:  0xEA

   maxOccurs:  1

   default:  0

   type:  uinteger




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   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.

8.1.5.1.2.7.  CueReference Element

   name:  CueReference

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

   id:  0xDB

   type:  master

   minver:  2

   definition:  The Clusters containing the referenced Blocks.

8.1.5.1.2.8.  CueRefTime Element

   name:  CueRefTime

   path:  \Segment\Cues\CuePoint\CueTrackPositions\CueReference\CueRefTi
      me

   id:  0x96

   minOccurs:  1

   maxOccurs:  1

   type:  uinteger

   minver:  2

   definition:  Timestamp of the referenced Block.

8.1.6.  Attachments Element

   name:  Attachments

   path:  \Segment\Attachments

   id:  0x1941A469

   maxOccurs:  1



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   type:  master

   definition:  Contain attached files.

8.1.6.1.  AttachedFile Element

   name:  AttachedFile

   path:  \Segment\Attachments\AttachedFile

   id:  0x61A7

   minOccurs:  1

   type:  master

   definition:  An attached file.

8.1.6.1.1.  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.

8.1.6.1.2.  FileName Element

   name:  FileName

   path:  \Segment\Attachments\AttachedFile\FileName

   id:  0x466E

   minOccurs:  1

   maxOccurs:  1

   type:  utf-8

   definition:  Filename of the attached file.




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8.1.6.1.3.  FileMimeType Element

   name:  FileMimeType

   path:  \Segment\Attachments\AttachedFile\FileMimeType

   id:  0x4660

   minOccurs:  1

   maxOccurs:  1

   type:  string

   definition:  MIME type of the file.

8.1.6.1.4.  FileData Element

   name:  FileData

   path:  \Segment\Attachments\AttachedFile\FileData

   id:  0x465C

   minOccurs:  1

   maxOccurs:  1

   type:  binary

   definition:  The data of the file.

8.1.6.1.5.  FileUID Element

   name:  FileUID

   path:  \Segment\Attachments\AttachedFile\FileUID

   id:  0x46AE

   minOccurs:  1

   maxOccurs:  1

   range:  not 0

   type:  uinteger




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

8.1.7.  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 22.

8.1.7.1.  EditionEntry Element

   name:  EditionEntry

   path:  \Segment\Chapters\EditionEntry

   id:  0x45B9

   minOccurs:  1

   type:  master

   definition:  Contains all information about a Segment edition.

8.1.7.1.1.  EditionUID Element

   name:  EditionUID

   path:  \Segment\Chapters\EditionEntry\EditionUID

   id:  0x45BC

   maxOccurs:  1

   range:  not 0

   type:  uinteger




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

8.1.7.1.2.  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.

8.1.7.1.3.  EditionFlagOrdered Element

   name:  EditionFlagOrdered

   path:  \Segment\Chapters\EditionEntry\EditionFlagOrdered

   id:  0x45DD

   minOccurs:  1

   maxOccurs:  1

   range:  0-1

   default:  0

   type:  uinteger

   definition:  Set to 1 if the chapters can be defined multiple times
      and the order to play them is enforced; see Section 22.1.3.







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8.1.7.1.4.  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).

8.1.7.1.4.1.  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.

8.1.7.1.4.2.  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].

8.1.7.1.4.3.  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).

8.1.7.1.4.4.  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.

   usage notes:  If the Edition is an ordered edition, see
      Section 22.1.3, then this Element is REQUIRED.

8.1.7.1.4.5.  ChapterFlagHidden Element

   name:  ChapterFlagHidden

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

   id:  0x98

   minOccurs:  1




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   maxOccurs:  1

   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 22.2.3 on Chapter flags).

8.1.7.1.4.6.  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.

   notes:

        +===========+=============================================+
        | attribute | note                                        |
        +===========+=============================================+
        | minOccurs | ChapterSegmentUID MUST be set (minOccurs=1) |
        |           | if ChapterSegmentEditionUID is used; see    |
        |           | Section 19.2 on medium-linking Segments.    |
        +-----------+---------------------------------------------+

              Table 27: ChapterSegmentUID implementation notes

8.1.7.1.4.7.  ChapterSegmentEditionUID Element

   name:  ChapterSegmentEditionUID

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



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      ionUID

   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; see Section 19.2 on
      medium-linking Segments.

8.1.7.1.4.8.  ChapterPhysicalEquiv Element

   name:  ChapterPhysicalEquiv

   path:  \Segment\Chapters\EditionEntry\+ChapterAtom\ChapterPhysicalEqu
      iv

   id:  0x63C3

   maxOccurs:  1

   type:  uinteger

   definition:  Specify the physical equivalent of this ChapterAtom like
      "DVD" (60) or "SIDE" (50); see Section 22.4 for a complete list of
      values.

8.1.7.1.4.9.  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.







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8.1.7.1.4.10.  ChapString Element

   name:  ChapString

   path:  \Segment\Chapters\EditionEntry\+ChapterAtom\ChapterDisplay\Cha
      pString

   id:  0x85

   minOccurs:  1

   maxOccurs:  1

   type:  utf-8

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

8.1.7.1.4.11.  ChapLanguage Element

   name:  ChapLanguage

   path:  \Segment\Chapters\EditionEntry\+ChapterAtom\ChapterDisplay\Cha
      pLanguage

   id:  0x437C

   minOccurs:  1

   default:  eng

   type:  string

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

8.1.7.1.4.12.  ChapLanguageIETF Element

   name:  ChapLanguageIETF

   path:  \Segment\Chapters\EditionEntry\+ChapterAtom\ChapterDisplay\Cha
      pLanguageIETF

   id:  0x437D

   type:  string




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   minver:  4

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

8.1.7.1.4.13.  ChapCountry Element

   name:  ChapCountry

   path:  \Segment\Chapters\EditionEntry\+ChapterAtom\ChapterDisplay\Cha
      pCountry

   id:  0x437E

   type:  string

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

8.1.7.1.4.14.  ChapProcess Element

   name:  ChapProcess

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

   id:  0x6944

   type:  master

   definition:  Contains all the commands associated to the Atom.

8.1.7.1.4.15.  ChapProcessCodecID Element

   name:  ChapProcessCodecID

   path:  \Segment\Chapters\EditionEntry\+ChapterAtom\ChapProcess\ChapPr
      ocessCodecID

   id:  0x6955

   minOccurs:  1




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   maxOccurs:  1

   default:  0

   type:  uinteger

   definition:  Contains the type of the codec used for the processing.
      A value of 0 means native Matroska processing (to be defined), a
      value of 1 means the DVD command set is used; see Section 22.3 on
      DVD menus.  More codec IDs can be added later.

8.1.7.1.4.16.  ChapProcessPrivate Element

   name:  ChapProcessPrivate

   path:  \Segment\Chapters\EditionEntry\+ChapterAtom\ChapProcess\ChapPr
      ocessPrivate

   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 22.3 on DVD menus.

8.1.7.1.4.17.  ChapProcessCommand Element

   name:  ChapProcessCommand

   path:  \Segment\Chapters\EditionEntry\+ChapterAtom\ChapProcess\ChapPr
      ocessCommand

   id:  0x6911

   type:  master

   definition:  Contains all the commands associated to the Atom.

8.1.7.1.4.18.  ChapProcessTime Element

   name:  ChapProcessTime

   path:  \Segment\Chapters\EditionEntry\+ChapterAtom\ChapProcess\ChapPr
      ocessCommand\ChapProcessTime




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   id:  0x6922

   minOccurs:  1

   maxOccurs:  1

   type:  uinteger

   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 28: ChapProcessTime values

8.1.7.1.4.19.  ChapProcessData Element

   name:  ChapProcessData

   path:  \Segment\Chapters\EditionEntry\+ChapterAtom\ChapProcess\ChapPr
      ocessCommand\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 22.3 on DVD menus.

8.1.8.  Tags Element

   name:  Tags




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   path:  \Segment\Tags

   id:  0x1254C367

   type:  master

   definition:  Element containing metadata describing Tracks, Editions,
      Chapters, Attachments, or the Segment as a whole.  A list of valid
      tags can be found in [MatroskaTags].

8.1.8.1.  Tag Element

   name:  Tag

   path:  \Segment\Tags\Tag

   id:  0x7373

   minOccurs:  1

   type:  master

   definition:  A single metadata descriptor.

8.1.8.1.1.  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.

8.1.8.1.1.1.  TargetTypeValue Element

   name:  TargetTypeValue

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




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   id:  0x68CA

   maxOccurs:  1

   default:  50

   type:  uinteger

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

   defined values:

   +=======+==========================+================================+
   | value | label                    | definition                     |
   +=======+==========================+================================+
   | 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 29: TargetTypeValue values

8.1.8.1.1.2.  TargetType Element

   name:  TargetType

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




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   id:  0x63CA

   maxOccurs:  1

   type:  string

   definition:  An informational string that can be used to display the
      logical level of the target like "ALBUM", "TRACK", "MOVIE",
      "CHAPTER", etc ; see Section 6.4 of [MatroskaTags].

   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    |



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                        +------------+------------+
                        | SUBTRACK   | SUBTRACK   |
                        +------------+------------+
                        | PART       | PART       |
                        +------------+------------+
                        | MOVEMENT   | MOVEMENT   |
                        +------------+------------+
                        | SCENE      | SCENE      |
                        +------------+------------+
                        | SHOT       | SHOT       |
                        +------------+------------+

                        Table 30: TargetType values

8.1.8.1.1.3.  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.

   usage notes:  If the value is 0 at this level, the tags apply to all
      tracks in the Segment.  If set to any other value, it MUST match
      the TrackUID value of a track found in this Segment.

8.1.8.1.1.4.  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.

   usage notes:  If the value is 0 at this level, the tags apply to all



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      editions in the Segment.  If set to any other value, it MUST match
      the EditionUID value of an edition found in this Segment.

8.1.8.1.1.5.  TagChapterUID Element

   name:  TagChapterUID

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

   id:  0x63C4

   default:  0

   type:  uinteger

   definition:  A unique ID to identify the Chapter(s) the tags belong
      to.

   usage notes:  If the value is 0 at this level, the tags apply to all
      chapters in the Segment.  If set to any other value, it MUST match
      the ChapterUID value of a chapter found in this Segment.

8.1.8.1.1.6.  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.

   usage notes:  If the value is 0 at this level, the tags apply to all
      the attachments in the Segment.  If set to any other value, it
      MUST match the FileUID value of an attachment found in this
      Segment.

8.1.8.1.2.  SimpleTag Element

   name:  SimpleTag

   path:  \Segment\Tags\Tag\+SimpleTag




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   id:  0x67C8

   minOccurs:  1

   type:  master

   recursive:  1

   definition:  Contains general information about the target.

8.1.8.1.2.1.  TagName Element

   name:  TagName

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

   id:  0x45A3

   minOccurs:  1

   maxOccurs:  1

   type:  utf-8

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

8.1.8.1.2.2.  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 on language codes.  This
      Element MUST be ignored if the TagLanguageIETF Element is used
      within the same SimpleTag Element.





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8.1.8.1.2.3.  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.

8.1.8.1.2.4.  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.

8.1.8.1.2.5.  TagString Element

   name:  TagString

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

   id:  0x4487




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   maxOccurs:  1

   type:  utf-8

   definition:  The value of the Tag.

8.1.8.1.2.6.  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
      cannot be used in the same SimpleTag as TagString.

9.  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.

9.1.  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.












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   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.

9.2.  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.

9.3.  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.

9.4.  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.



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9.5.  Info

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

9.6.  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.

9.7.  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.

9.8.  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.

9.9.  Optimum layout from a muxer

   *  SeekHead

   *  Info

   *  Tracks



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   *  Chapters

   *  Attachments

   *  Tags

   *  Clusters

   *  Cues

9.10.  Optimum layout after editing tags

   *  SeekHead

   *  Info

   *  Tracks

   *  Chapters

   *  Attachments

   *  Void

   *  Clusters

   *  Cues

   *  Tags

9.11.  Optimum layout with Cues at the front

   *  SeekHead

   *  Info

   *  Tracks

   *  Chapters

   *  Attachments

   *  Tags

   *  Cues

   *  Clusters




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9.12.  Cluster Timestamp

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

10.  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
   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.

11.  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




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   *  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")

12.  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.

12.1.  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 31: Block Header base parts

12.2.  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                 |



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      +--------+-----+--------+------------------------------------+
      |        |     |        | * 11 : EBML lacing                 |
      +--------+-----+--------+------------------------------------+
      |        |     |        | * 10 : fixed-size lacing           |
      +--------+-----+--------+------------------------------------+
      | 0x03+  | 7   | -      | not used                           |
      +--------+-----+--------+------------------------------------+

                    Table 32: Block Header flags part

12.3.  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

   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:

12.3.1.  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.




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12.3.2.  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:

   +==========================+=======================================+
   | 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 2^20-1             |
   | xxxx                     |                                       |
   +--------------------------+---------------------------------------+
   | 0001 xxxx xxxx xxxx xxxx | value -(2^27-1) to 2^27-1             |
   | xxxx xxxx xxxx           |                                       |
   +--------------------------+---------------------------------------+
   | 0000 1xxx xxxx xxxx xxxx | value -(2^34-1) to 2^34-1             |
   | xxxx xxxx xxxx xxxx xxxx |                                       |
   +--------------------------+---------------------------------------+
   | 0000 01xx xxxx xxxx xxxx | value -(2^41-1) to 2^41-1             |
   | xxxx xxxx xxxx xxxx xxxx |                                       |
   | xxxx xxxx                |                                       |
   +--------------------------+---------------------------------------+
   | 0000 001x xxxx xxxx xxxx | value -(2^48-1) to 2^48-1             |
   | xxxx xxxx xxxx xxxx xxxx |                                       |
   | xxxx xxxx xxxx xxxx      |                                       |
   +--------------------------+---------------------------------------+

                     Table 33: EBML Lacing bits usage

   *  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



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   *  Data in frame 3

12.3.3.  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

12.4.  SimpleBlock Structure

   The SimpleBlock is inspired by the Block structure; see Section 12.
   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.

12.4.1.  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 34: SimpleBlock Header base parts




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12.4.2.  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 35: SimpleBlock Header flags part

12.4.3.  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 36: Lace sizes coded in the Block

   For (possibly) Laced Data



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

                   Table 37: Lace data after lace sizes

13.  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.

13.1.  Timestamp Types

   *  Absolute Timestamp = Block+Cluster

   *  Relative Timestamp = Block

   *  Scaled Timestamp = Block+Cluster

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

13.2.  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 13.4
   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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13.3.  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.

13.4.  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.

13.5.  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.

   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



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   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.

13.6.  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
   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.





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   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 13.3, 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 13.1, of 100 seconds would have a Raw Timestamp of
   104.66666667 seconds, and so would be stored in that part of the
   file.

   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.






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   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.

14.  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.

15.  Image Presentation

15.1.  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



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   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.

15.2.  Rotation

   The ProjectionPoseRoll Element (see Section 8.1.4.1.31.45) 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 8.1.4.1.31.40) 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>

                        Figure 11: Rotation example.

16.  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.





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   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 10.

17.  MIME Types

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

   *  .mka : Matroska audio audio/x-matroska

   *  .mkv : Matroska video video/x-matroska

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

18.  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.

18.1.  Segment Position Exception

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

18.2.  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|




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   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.

   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'.

19.  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.

19.1.  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 38: Usual Hard Linking UIDs

   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 39: Hard Linking without PrevUID

   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 40: Hard Linking without NextUID



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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 41: Hard Linking with mixed UID links

19.2.  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.

   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.

19.2.1.  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 NOT be set.

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

19.2.2.  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.

19.3.  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.

20.  Track Flags

20.1.  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.




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

20.2.  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.

20.3.  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.

20.4.  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.

20.5.  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.

20.6.  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.

20.7.  Commentary flag

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







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20.8.  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.

20.9.  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.

20.10.  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 colors separated).  For compatibility
   with such movies, there is a value of the StereoMode that corresponds
   to AnaGlyph.





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   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 20.8 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.

21.  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.

21.1.  Audio Selection

   Example track set:













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   +===+=====+====+======+========+=======+================+===========+
   |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 42: Audio Tracks for default selection

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

   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



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   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.

21.2.  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 43: Subtitle Tracks for default selection

   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.

22.  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.

22.1.  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.

22.1.1.  EditionFlagDefault

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

22.1.2.  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.








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

                   Table 44: Default edition, all default

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

                   Table 45: Default edition, no default

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

                  Table 46: Default edition, with default

22.1.3.  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
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   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.

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

                     Table 47: elements only found in
                             ordered chapters

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

22.1.3.1.  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.






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   *  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 19 on the Linked Segments for more information about Hard
   Linking, Soft Linking, and Medium Linking.

22.2.  ChapterAtom

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

22.2.1.  ChapterTimeStart

   The timestamp of the start of Chapter with nanosecond accuracy, not
   scaled by TimestampScale.  For Simple Chapters this is the position
   of the chapter markers in the timeline.

22.2.2.  ChapterTimeEnd

   The timestamp of the end of Chapter with nanosecond accuracy, not
   scaled by TimestampScale.  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
   strictly greater than the start timestamp.

      +===========+=================+===============+===============+
      | Chapter   | Start timestamp | End timestamp | Duration      |
      +===========+=================+===============+===============+
      | Chapter 1 | 0               | 1000000000    | 1000000000    |
      +-----------+-----------------+---------------+---------------+
      | Chapter 2 | 1000000000      | 5000000000    | 4000000000    |
      +-----------+-----------------+---------------+---------------+
      | Chapter 3 | 6000000000      | 6000000000    | Invalid (0)   |
      +-----------+-----------------+---------------+---------------+
      | Chapter 4 | 9000000000      | 8000000000    | Invalid       |
      |           |                 |               | (-1000000000) |
      +-----------+-----------------+---------------+---------------+

                Table 48: ChapterTimeEnd usage possibilities

22.2.3.  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.



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        +==========================+===================+=========+
        | 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 49: ChapterFlagHidden nested visibility

22.3.  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.

   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.

22.4.  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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   +=======+=======================+=============+=====================+
   | Value | Audio                 | Video       | Comment             |
   +=======+=======================+=============+=====================+
   | 70    | SET / PACKAGE         | SET /       | the collection of   |
   |       |                       | PACKAGE     | different media     |
   +-------+-----------------------+-------------+---------------------+
   | 60    | CD / 12" / 10" / 7" / | DVD / VHS   | the physical medium |
   |       | TAPE / MINIDISC / DAT | /           | like a CD or a DVD  |
   |       |                       | LASERDISC   |                     |
   +-------+-----------------------+-------------+---------------------+
   | 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 50: ChapterPhysicalEquiv meaning per track type

22.5.  Chapter Examples

22.5.1.  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




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   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>
         </ChapterDisplay>
       </ChapterAtom>
       <ChapterAtom>
         <ChapterUID>2311527</ChapterUID>
         <ChapterTimeStart>5000000000</ChapterTimeStart>
         <ChapterTimeEnd>25000000000</ChapterTimeEnd>
         <ChapterDisplay>
           <ChapString>Before the crime</ChapString>
         </ChapterDisplay>
         <ChapterDisplay>
           <ChapString>Avant le crime</ChapString>
           <ChapLanguage>fra</ChapLanguage>
         </ChapterDisplay>
       </ChapterAtom>
       <ChapterAtom>
         <ChapterUID>3430008</ChapterUID>
         <ChapterTimeStart>25000000000</ChapterTimeStart>
         <ChapterTimeEnd>27500000000</ChapterTimeEnd>
         <ChapterDisplay>
           <ChapString>The crime</ChapString>
         </ChapterDisplay>
         <ChapterDisplay>
           <ChapString>Le crime</ChapString>
           <ChapLanguage>fra</ChapLanguage>
         </ChapterDisplay>
       </ChapterAtom>
       <ChapterAtom>
         <ChapterUID>4548489</ChapterUID>
         <ChapterTimeStart>27500000000</ChapterTimeStart>
         <ChapterTimeEnd>38000000000</ChapterTimeEnd>
         <ChapterDisplay>
           <ChapString>After the crime</ChapString>
         </ChapterDisplay>
         <ChapterDisplay>
           <ChapString>Après le crime</ChapString>
           <ChapLanguage>fra</ChapLanguage>
         </ChapterDisplay>



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       </ChapterAtom>
       <ChapterAtom>
         <ChapterUID>5666960</ChapterUID>
         <ChapterTimeStart>38000000000</ChapterTimeStart>
         <ChapterTimeEnd>43000000000</ChapterTimeEnd>
         <ChapterDisplay>
           <ChapString>Credits</ChapString>
         </ChapterDisplay>
         <ChapterDisplay>
           <ChapString>Générique</ChapString>
           <ChapLanguage>fra</ChapLanguage>
         </ChapterDisplay>
       </ChapterAtom>
     </EditionEntry>
   </Chapters>

                     Figure 12: Basic Chapters Example.

22.5.2.  Example 2 : nested chapters

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

22.5.2.1.  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







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   <Chapters>
     <EditionEntry>
       <EditionUID>1281690858003401414</EditionUID>
       <ChapterAtom>
         <ChapterUID>1</ChapterUID>
         <ChapterTimeStart>0</ChapterTimeStart>
         <ChapterTimeEnd>748000000</ChapterTimeEnd>
         <ChapterDisplay>
           <ChapString>Baby wants to Bleep/Rock</ChapString>
         </ChapterDisplay>
         <ChapterAtom>
           <ChapterUID>2</ChapterUID>
           <ChapterTimeStart>0</ChapterTimeStart>
           <ChapterTimeEnd>278000000</ChapterTimeEnd>
           <ChapterDisplay>
             <ChapString>Baby wants to bleep (pt.1)</ChapString>
           </ChapterDisplay>
         </ChapterAtom>
         <ChapterAtom>
           <ChapterUID>3</ChapterUID>
           <ChapterTimeStart>278000000</ChapterTimeStart>
           <ChapterTimeEnd>432000000</ChapterTimeEnd>
           <ChapterDisplay>
             <ChapString>Baby wants to rock</ChapString>
           </ChapterDisplay>
         </ChapterAtom>
         <ChapterAtom>
           <ChapterUID>4</ChapterUID>
           <ChapterTimeStart>432000000</ChapterTimeStart>
           <ChapterTimeEnd>633000000</ChapterTimeEnd>
           <ChapterDisplay>
             <ChapString>Baby wants to bleep (pt.2)</ChapString>
           </ChapterDisplay>
         </ChapterAtom>
         <ChapterAtom>
           <ChapterUID>5</ChapterUID>
           <ChapterTimeStart>633000000</ChapterTimeStart>
           <ChapterTimeEnd>748000000</ChapterTimeEnd>
           <ChapterDisplay>
             <ChapString>Baby wants to bleep (pt.3)</ChapString>
           </ChapterDisplay>
         </ChapterAtom>
       </ChapterAtom>
       <ChapterAtom>
         <ChapterUID>6</ChapterUID>
         <ChapterTimeStart>750000000</ChapterTimeStart>
         <ChapterTimeEnd>1178500000</ChapterTimeEnd>
         <ChapterDisplay>



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           <ChapString>Bleeper_O+2</ChapString>
         </ChapterDisplay>
       </ChapterAtom>
       <ChapterAtom>
         <ChapterUID>7</ChapterUID>
         <ChapterTimeStart>1180500000</ChapterTimeStart>
         <ChapterTimeEnd>1340000000</ChapterTimeEnd>
         <ChapterDisplay>
           <ChapString>Baby wants to bleep (pt.4)</ChapString>
         </ChapterDisplay>
       </ChapterAtom>
       <ChapterAtom>
         <ChapterUID>8</ChapterUID>
         <ChapterTimeStart>1342000000</ChapterTimeStart>
         <ChapterTimeEnd>1518000000</ChapterTimeEnd>
         <ChapterDisplay>
           <ChapString>Bleep to bleep</ChapString>
         </ChapterDisplay>
       </ChapterAtom>
       <ChapterAtom>
         <ChapterUID>9</ChapterUID>
         <ChapterTimeStart>1520000000</ChapterTimeStart>
         <ChapterTimeEnd>2015000000</ChapterTimeEnd>
         <ChapterDisplay>
           <ChapString>Baby wants to bleep (k)</ChapString>
         </ChapterDisplay>
       </ChapterAtom>
       <ChapterAtom>
         <ChapterUID>10</ChapterUID>
         <ChapterTimeStart>2017000000</ChapterTimeStart>
         <ChapterTimeEnd>2668000000</ChapterTimeEnd>
         <ChapterDisplay>
           <ChapString>Bleeper</ChapString>
         </ChapterDisplay>
       </ChapterAtom>
     </EditionEntry>
   </Chapters>

                    Figure 13: Nested Chapters Example.

23.  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.




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   Matroska Readers MUST NOT execute files stored as Attachment
   Elements.

23.1.  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 51: Cover Art Filenames

24.  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.

24.1.  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.

25.  Matroska Streaming

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

25.1.  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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25.2.  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.

26.  IANA Considerations

26.1.  Matroska Element IDs Registry

26.2.  ChapterCodecID Registry

26.3.  Historic Deprecated Element IDs Registry

   As Matroska evolved since 2002 many parts that were considered for
   use in the format were never used and often incorrectly designed.
   Many of the elements that were then defined are not found in any
   known files but were part of public specs.  DivX also had a few
   custom elements that were designed for custom features.




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   We list these elements that have a known ID that SHOULD NOT be reused
   to avoid colliding with existing files.

26.3.1.  SilentTracks Element

   path:  \Segment\Cluster\SilentTracks

   id:  0x5854

   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.

26.3.2.  SilentTrackNumber Element

   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.

26.3.3.  BlockVirtual Element

   path:  \Segment\Cluster\BlockGroup\BlockVirtual

   id:  0xA2

   type:  binary

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

26.3.4.  ReferenceVirtual Element

   path:  \Segment\Cluster\BlockGroup\ReferenceVirtual

   id:  0xFD

   type:  integer

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



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26.3.5.  FrameNumber Element

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

   id:  0xCD

   type:  uinteger

   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).

26.3.6.  BlockAdditionID Element

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

   id:  0xCB

   type:  uinteger

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

26.3.7.  Delay Element

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

   id:  0xCE

   type:  uinteger

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

26.3.8.  SliceDuration Element

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

   id:  0xCF

   type:  uinteger

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

26.3.9.  ReferenceFrame Element

   path:  \Segment\Cluster\BlockGroup\ReferenceFrame

   id:  0xC8



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   type:  master

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

26.3.10.  ReferenceOffset Element

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

   id:  0xC9

   type:  uinteger

   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].

26.3.11.  ReferenceTimestamp Element

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

   id:  0xCA

   type:  uinteger

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

26.3.12.  EncryptedBlock Element

   path:  \Segment\Cluster\EncryptedBlock

   id:  0xAF

   type:  binary

   definition:  Similar to SimpleBlock, see Section 12.4, but the data
      inside the Block are Transformed (encrypt and/or signed).

26.3.13.  TrackOffset Element

   path:  \Segment\Tracks\TrackEntry\TrackOffset

   id:  0x537F

   type:  integer

   definition:  A value to add to the Block's Timestamp.  This can be



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      used to adjust the playback offset of a track.

26.3.14.  CodecSettings Element

   path:  \Segment\Tracks\TrackEntry\CodecSettings

   id:  0x3A9697

   type:  utf-8

   definition:  A string describing the encoding setting used.

26.3.15.  CodecInfoURL Element

   path:  \Segment\Tracks\TrackEntry\CodecInfoURL

   id:  0x3B4040

   type:  string

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

26.3.16.  CodecDownloadURL Element

   path:  \Segment\Tracks\TrackEntry\CodecDownloadURL

   id:  0x26B240

   type:  string

   definition:  A URL to download about the codec used.

26.3.17.  CodecDecodeAll Element

   path:  \Segment\Tracks\TrackEntry\CodecDecodeAll

   id:  0xAA

   type:  uinteger

   definition:  Set to 1 if the codec can decode potentially damaged
      data.

26.3.18.  OldStereoMode Element

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

   id:  0x53B9



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   type:  uinteger

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

26.3.19.  AspectRatioType Element

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

   id:  0x54B3

   type:  uinteger

   definition:  Specify the possible modifications to the aspect ratio.

26.3.20.  GammaValue Element

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

   id:  0x2FB523

   type:  float

   definition:  Gamma Value.

26.3.21.  FrameRate Element

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

   id:  0x2383E3

   type:  float

   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.

26.3.22.  ChannelPositions Element

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

   id:  0x7D7B

   type:  binary

   definition:  Table of horizontal angles for each successive channel.




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26.3.23.  TrickTrackUID Element

   path:  \Segment\Tracks\TrackEntry\TrickTrackUID

   id:  0xC0

   type:  uinteger

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

26.3.24.  TrickTrackSegmentUID Element

   path:  \Segment\Tracks\TrackEntry\TrickTrackSegmentUID

   id:  0xC1

   type:  binary

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

26.3.25.  TrickTrackFlag Element

   path:  \Segment\Tracks\TrackEntry\TrickTrackFlag

   id:  0xC6

   type:  uinteger

   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].

26.3.26.  TrickMasterTrackUID Element

   path:  \Segment\Tracks\TrackEntry\TrickMasterTrackUID

   id:  0xC7

   type:  uinteger

   definition:  The TrackUID of the video track in the paired EBML




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      structure that corresponds to this Smooth FF/RW track.  See
      [DivXTrickTrack].

26.3.27.  TrickMasterTrackSegmentUID Element

   path:  \Segment\Tracks\TrackEntry\TrickMasterTrackSegmentUID

   id:  0xC4

   type:  binary

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

26.3.28.  ContentSignature Element

   path:  \Segment\Tracks\TrackEntry\ContentEncodings\ContentEncoding\Co
      ntentEncryption\ContentSignature

   id:  0x47E3

   type:  binary

   definition:  A cryptographic signature of the contents.

26.3.29.  ContentSigKeyID Element

   path:  \Segment\Tracks\TrackEntry\ContentEncodings\ContentEncoding\Co
      ntentEncryption\ContentSigKeyID

   id:  0x47E4

   type:  binary

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

26.3.30.  ContentSigAlgo Element

   path:  \Segment\Tracks\TrackEntry\ContentEncodings\ContentEncoding\Co
      ntentEncryption\ContentSigAlgo

   id:  0x47E5

   type:  uinteger

   definition:  The algorithm used for the signature.




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26.3.31.  ContentSigHashAlgo Element

   path:  \Segment\Tracks\TrackEntry\ContentEncodings\ContentEncoding\Co
      ntentEncryption\ContentSigHashAlgo

   id:  0x47E6

   type:  uinteger

   definition:  The hash algorithm used for the signature.

26.3.32.  CueRefCluster Element

   path:  \Segment\Cues\CuePoint\CueTrackPositions\CueReference\CueRefCl
      uster

   id:  0x97

   type:  uinteger

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

26.3.33.  CueRefNumber Element

   path:  \Segment\Cues\CuePoint\CueTrackPositions\CueReference\CueRefNu
      mber

   id:  0x535F

   type:  uinteger

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

26.3.34.  CueRefCodecState Element

   path:  \Segment\Cues\CuePoint\CueTrackPositions\CueReference\CueRefCo
      decState

   id:  0xEB

   type:  uinteger

   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.




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26.3.35.  FileReferral Element

   path:  \Segment\Attachments\AttachedFile\FileReferral

   id:  0x4675

   type:  binary

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

26.3.36.  FileUsedStartTime Element

   path:  \Segment\Attachments\AttachedFile\FileUsedStartTime

   id:  0x4661

   type:  uinteger

   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].

26.3.37.  FileUsedEndTime Element

   path:  \Segment\Attachments\AttachedFile\FileUsedEndTime

   id:  0x4662

   type:  uinteger

   definition:  The timecode at which this optimized font attachment
      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].

26.3.38.  TagDefaultBogus Element

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

   id:  0x44B4

   type:  uinteger

   definition:  A variant of the TagDefault element with a bogus Element
      ID; see Section 8.1.8.1.2.4.




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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>.

   [Blowfish] Schneier, B., "The Blowfish Encryption Algorithm", 1993,
              <https://www.schneier.com/academic/blowfish/>.

   [BZIP2]    Seward, J., "bzip2", 18 July 1996,
              <https://sourceware.org/bzip2/>.

   [FIPS.197] US National Institute of Standards and Technology,
              "Advanced Encryption Standard (AES)",
              DOI 10.6028/NIST.FIPS.197, 26 November 2001,
              <https://csrc.nist.gov/publications/detail/fips/197/
              final>.

   [FIPS.46-3]
              US National Institute of Standards and Technology, "Data
              Encryption Standard (DES)", FIPS PUB 46, 25 October 1999,
              <https://csrc.nist.gov/publications/detail/fips/46/3/
              archive/1999-10-25>.

   [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>.

   [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>.

   [LZO]      Tarreau, W., Rodgman, R., and M. Oberhumer,
              "Lempel–Ziv–Oberhumer compression", 30 October 2018,
              <https://www.kernel.org/doc/Documentation/lzo.txt>.




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   [MatroskaCodec]
              Lhomme, S., Bunkus, M., and D. Rice, "Media Container
              Codec Specifications", Work in Progress, Internet-Draft,
              draft-ietf-cellar-codec-06, 12 April 2021,
              <https://datatracker.ietf.org/doc/html/draft-ietf-cellar-
              codec-06>.

   [MatroskaTags]
              Lhomme, S., Bunkus, M., and D. Rice, "Matroska Media
              Container Tag Specifications", Work in Progress, Internet-
              Draft, draft-ietf-cellar-tags-06, 12 April 2021,
              <https://datatracker.ietf.org/doc/html/draft-ietf-cellar-
              tags-06>.

   [RFC1851]  Karn, P., Metzger, P., and W. Simpson, "The ESP Triple DES
              Transform", RFC 1851, DOI 10.17487/RFC1851, September
              1995, <https://www.rfc-editor.org/info/rfc1851>.

   [RFC1950]  Deutsch, P. and J-L. Gailly, "ZLIB Compressed Data Format
              Specification version 3.3", RFC 1950,
              DOI 10.17487/RFC1950, May 1996,
              <https://www.rfc-editor.org/info/rfc1950>.

   [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>.

   [Twofish]  Schneier, B., Kelsey, J., Whiting, D., Wagner, D., Hall,
              C., and N. Ferguson, "Twofish: A 128-Bit Block Cipher", 15
              June 1998, <https://www.schneier.com/academic/twofish/>.

   [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






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   [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


   Moritz Bunkus

   Email: moritz@bunkus.org


   Dave Rice

   Email: dave@dericed.com























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