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Matroska Media Container Format Specifications
draft-ietf-cellar-matroska-19

The information below is for an old version of the document.
Document Type
This is an older version of an Internet-Draft whose latest revision state is "Active".
Authors Steve Lhomme, Moritz Bunkus, Dave Rice
Last updated 2023-10-02 (Latest revision 2023-08-12)
RFC stream Internet Engineering Task Force (IETF)
Formats
Reviews
Additional resources Mailing list discussion
Stream WG state Submitted to IESG for Publication
Associated WG milestones
Oct 2018
Adopt matroska specifications as WG documents
Apr 2022
Submit specification for Matroska container to IESG (Standards Track)
Document shepherd Michael Richardson
Shepherd write-up Show Last changed 2022-09-26
IESG IESG state IESG Evaluation::Revised I-D Needed
Consensus boilerplate Yes
Telechat date (None)
Needs 2 more YES or NO OBJECTION positions to pass.
Responsible AD Murray Kucherawy
Send notices to mcr+ietf@sandelman.ca
IANA IANA review state Version Changed - Review Needed
draft-ietf-cellar-matroska-19
CELLAR Group                                                   S. Lhomme
Internet-Draft                                                          
Intended status: Standards Track                               M. Bunkus
Expires: 13 February 2024                                               
                                                                 D. Rice
                                                          12 August 2023

             Matroska Media Container Format Specifications
                     draft-ietf-cellar-matroska-19

Abstract

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

   This document updates [RFC8794] to permit the use of a previously
   reserved EBML Element ID.

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 13 February 2024.

Copyright Notice

   Copyright (c) 2023 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

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   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 Revised BSD License text as
   described in Section 4.e of the Trust Legal Provisions and are
   provided without warranty as described in the Revised BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   6
   2.  Status of this document . . . . . . . . . . . . . . . . . . .   7
   3.  Notation and Conventions  . . . . . . . . . . . . . . . . . .   7
   4.  Matroska Overview . . . . . . . . . . . . . . . . . . . . . .   7
     4.1.  Principles  . . . . . . . . . . . . . . . . . . . . . . .   7
     4.2.  Updates to RFC 8794 . . . . . . . . . . . . . . . . . . .   7
     4.3.  Added EBML Constraints  . . . . . . . . . . . . . . . . .   8
     4.4.  Design Rules  . . . . . . . . . . . . . . . . . . . . . .   9
     4.5.  Data Layout . . . . . . . . . . . . . . . . . . . . . . .   9
   5.  Matroska Schema . . . . . . . . . . . . . . . . . . . . . . .  18
     5.1.  Segment Element . . . . . . . . . . . . . . . . . . . . .  18
       5.1.1.  SeekHead Element  . . . . . . . . . . . . . . . . . .  19
         5.1.1.1.  Seek Element  . . . . . . . . . . . . . . . . . .  19
       5.1.2.  Info Element  . . . . . . . . . . . . . . . . . . . .  19
         5.1.2.1.  SegmentUUID Element . . . . . . . . . . . . . . .  19
         5.1.2.2.  SegmentFilename Element . . . . . . . . . . . . .  20
         5.1.2.3.  PrevUUID Element  . . . . . . . . . . . . . . . .  20
         5.1.2.4.  PrevFilename Element  . . . . . . . . . . . . . .  20
         5.1.2.5.  NextUUID Element  . . . . . . . . . . . . . . . .  20
         5.1.2.6.  NextFilename Element  . . . . . . . . . . . . . .  21
         5.1.2.7.  SegmentFamily Element . . . . . . . . . . . . . .  21
         5.1.2.8.  ChapterTranslate Element  . . . . . . . . . . . .  21
         5.1.2.9.  TimestampScale Element  . . . . . . . . . . . . .  22
         5.1.2.10. Duration Element  . . . . . . . . . . . . . . . .  23
         5.1.2.11. DateUTC Element . . . . . . . . . . . . . . . . .  23
         5.1.2.12. Title Element . . . . . . . . . . . . . . . . . .  23
         5.1.2.13. MuxingApp Element . . . . . . . . . . . . . . . .  23
         5.1.2.14. WritingApp Element  . . . . . . . . . . . . . . .  23
       5.1.3.  Cluster Element . . . . . . . . . . . . . . . . . . .  24
         5.1.3.1.  Timestamp Element . . . . . . . . . . . . . . . .  24
         5.1.3.2.  Position Element  . . . . . . . . . . . . . . . .  24
         5.1.3.3.  PrevSize Element  . . . . . . . . . . . . . . . .  24
         5.1.3.4.  SimpleBlock Element . . . . . . . . . . . . . . .  24
         5.1.3.5.  BlockGroup Element  . . . . . . . . . . . . . . .  25
       5.1.4.  Tracks Element  . . . . . . . . . . . . . . . . . . .  28
         5.1.4.1.  TrackEntry Element  . . . . . . . . . . . . . . .  28
       5.1.5.  Cues Element  . . . . . . . . . . . . . . . . . . . .  67

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         5.1.5.1.  CuePoint Element  . . . . . . . . . . . . . . . .  67
       5.1.6.  Attachments Element . . . . . . . . . . . . . . . . .  69
         5.1.6.1.  AttachedFile Element  . . . . . . . . . . . . . .  69
       5.1.7.  Chapters Element  . . . . . . . . . . . . . . . . . .  70
         5.1.7.1.  EditionEntry Element  . . . . . . . . . . . . . .  71
       5.1.8.  Tags Element  . . . . . . . . . . . . . . . . . . . .  76
         5.1.8.1.  Tag Element . . . . . . . . . . . . . . . . . . .  76
   6.  Matroska Element Ordering . . . . . . . . . . . . . . . . . .  82
     6.1.  Top-Level Elements  . . . . . . . . . . . . . . . . . . .  82
     6.2.  CRC-32  . . . . . . . . . . . . . . . . . . . . . . . . .  83
     6.3.  SeekHead  . . . . . . . . . . . . . . . . . . . . . . . .  83
     6.4.  Cues (index)  . . . . . . . . . . . . . . . . . . . . . .  83
     6.5.  Info  . . . . . . . . . . . . . . . . . . . . . . . . . .  83
     6.6.  Chapters Element  . . . . . . . . . . . . . . . . . . . .  84
     6.7.  Attachments . . . . . . . . . . . . . . . . . . . . . . .  84
     6.8.  Tags  . . . . . . . . . . . . . . . . . . . . . . . . . .  84
   7.  Matroska versioning . . . . . . . . . . . . . . . . . . . . .  84
   8.  Stream Copy . . . . . . . . . . . . . . . . . . . . . . . . .  85
   9.  DefaultDecodedFieldDuration . . . . . . . . . . . . . . . . .  86
   10. Cluster Blocks  . . . . . . . . . . . . . . . . . . . . . . .  86
     10.1.  Block Structure  . . . . . . . . . . . . . . . . . . . .  87
     10.2.  SimpleBlock Structure  . . . . . . . . . . . . . . . . .  88
     10.3.  Block Lacing . . . . . . . . . . . . . . . . . . . . . .  90
       10.3.1.  No lacing  . . . . . . . . . . . . . . . . . . . . .  90
       10.3.2.  Xiph lacing  . . . . . . . . . . . . . . . . . . . .  91
       10.3.3.  EBML lacing  . . . . . . . . . . . . . . . . . . . .  92
       10.3.4.  Fixed-size lacing  . . . . . . . . . . . . . . . . .  94
       10.3.5.  Laced Frames Timestamp . . . . . . . . . . . . . . .  94
     10.4.  Random Access Points . . . . . . . . . . . . . . . . . .  95
   11. Timestamps  . . . . . . . . . . . . . . . . . . . . . . . . .  98
     11.1.  Timestamp Ticks  . . . . . . . . . . . . . . . . . . . .  99
       11.1.1.  Matroska Ticks . . . . . . . . . . . . . . . . . . .  99
       11.1.2.  Segment Ticks  . . . . . . . . . . . . . . . . . . .  99
       11.1.3.  Track Ticks  . . . . . . . . . . . . . . . . . . . . 100
     11.2.  Block Timestamps . . . . . . . . . . . . . . . . . . . . 100
     11.3.  TimestampScale Rounding  . . . . . . . . . . . . . . . . 101
   12. Language Codes  . . . . . . . . . . . . . . . . . . . . . . . 101
   13. Country Codes . . . . . . . . . . . . . . . . . . . . . . . . 102
   14. Encryption  . . . . . . . . . . . . . . . . . . . . . . . . . 102
   15. Image Presentation  . . . . . . . . . . . . . . . . . . . . . 103
     15.1.  Cropping . . . . . . . . . . . . . . . . . . . . . . . . 103
     15.2.  Rotation . . . . . . . . . . . . . . . . . . . . . . . . 104
   16. Segment Position  . . . . . . . . . . . . . . . . . . . . . . 104
     16.1.  Segment Position Exception . . . . . . . . . . . . . . . 104
     16.2.  Example of Segment Position  . . . . . . . . . . . . . . 104
   17. Linked Segments . . . . . . . . . . . . . . . . . . . . . . . 105
     17.1.  Hard Linking . . . . . . . . . . . . . . . . . . . . . . 106
     17.2.  Medium Linking . . . . . . . . . . . . . . . . . . . . . 108

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       17.2.1.  Linked-Duration  . . . . . . . . . . . . . . . . . . 109
       17.2.2.  Linked-Edition . . . . . . . . . . . . . . . . . . . 109
   18. Track Flags . . . . . . . . . . . . . . . . . . . . . . . . . 109
     18.1.  Default flag . . . . . . . . . . . . . . . . . . . . . . 109
     18.2.  Forced flag  . . . . . . . . . . . . . . . . . . . . . . 110
     18.3.  Hearing-impaired flag  . . . . . . . . . . . . . . . . . 110
     18.4.  Visual-impaired flag . . . . . . . . . . . . . . . . . . 110
     18.5.  Descriptions flag  . . . . . . . . . . . . . . . . . . . 110
     18.6.  Original flag  . . . . . . . . . . . . . . . . . . . . . 110
     18.7.  Commentary flag  . . . . . . . . . . . . . . . . . . . . 110
     18.8.  Track Operation  . . . . . . . . . . . . . . . . . . . . 110
     18.9.  Overlay Track  . . . . . . . . . . . . . . . . . . . . . 111
     18.10. Multi-planar and 3D videos . . . . . . . . . . . . . . . 111
   19. Default track selection . . . . . . . . . . . . . . . . . . . 112
     19.1.  Audio Selection  . . . . . . . . . . . . . . . . . . . . 112
     19.2.  Subtitle selection . . . . . . . . . . . . . . . . . . . 114
   20. Chapters  . . . . . . . . . . . . . . . . . . . . . . . . . . 116
     20.1.  EditionEntry . . . . . . . . . . . . . . . . . . . . . . 116
       20.1.1.  EditionFlagDefault . . . . . . . . . . . . . . . . . 116
       20.1.2.  Default Edition  . . . . . . . . . . . . . . . . . . 116
       20.1.3.  EditionFlagOrdered . . . . . . . . . . . . . . . . . 117
         20.1.3.1.  Ordered-Edition and Matroska Segment-Linking . . 118
     20.2.  ChapterAtom  . . . . . . . . . . . . . . . . . . . . . . 119
       20.2.1.  ChapterTimeStart . . . . . . . . . . . . . . . . . . 119
       20.2.2.  ChapterTimeEnd . . . . . . . . . . . . . . . . . . . 119
       20.2.3.  Nested Chapters  . . . . . . . . . . . . . . . . . . 119
       20.2.4.  Nested Chapters in Ordered Chapters  . . . . . . . . 120
       20.2.5.  ChapterFlagHidden  . . . . . . . . . . . . . . . . . 120
     20.3.  Menu features  . . . . . . . . . . . . . . . . . . . . . 121
     20.4.  Physical Types . . . . . . . . . . . . . . . . . . . . . 121
     20.5.  Chapter Examples . . . . . . . . . . . . . . . . . . . . 122
       20.5.1.  Example 1 : basic chaptering . . . . . . . . . . . . 122
       20.5.2.  Example 2 : nested chapters  . . . . . . . . . . . . 124
         20.5.2.1.  The Micronauts "Bleep To Bleep"  . . . . . . . . 124
   21. Attachments . . . . . . . . . . . . . . . . . . . . . . . . . 126
     21.1.  Cover Art  . . . . . . . . . . . . . . . . . . . . . . . 126
     21.2.  Font files . . . . . . . . . . . . . . . . . . . . . . . 128
   22. Cues  . . . . . . . . . . . . . . . . . . . . . . . . . . . . 129
     22.1.  Recommendations  . . . . . . . . . . . . . . . . . . . . 130
   23. Matroska Streaming  . . . . . . . . . . . . . . . . . . . . . 130
     23.1.  File Access  . . . . . . . . . . . . . . . . . . . . . . 130
     23.2.  Livestreaming  . . . . . . . . . . . . . . . . . . . . . 131
   24. Tags  . . . . . . . . . . . . . . . . . . . . . . . . . . . . 132
     24.1.  Tags Precedence  . . . . . . . . . . . . . . . . . . . . 132
     24.2.  Tag Levels . . . . . . . . . . . . . . . . . . . . . . . 133
   25. Implementation Recommendations  . . . . . . . . . . . . . . . 133
     25.1.  Cluster  . . . . . . . . . . . . . . . . . . . . . . . . 133
     25.2.  SeekHead . . . . . . . . . . . . . . . . . . . . . . . . 133

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     25.3.  Optimum Layouts  . . . . . . . . . . . . . . . . . . . . 133
       25.3.1.  Optimum layout for a muxer . . . . . . . . . . . . . 133
       25.3.2.  Optimum layout after editing tags  . . . . . . . . . 134
       25.3.3.  Optimum layout with Cues at the front  . . . . . . . 134
       25.3.4.  Optimum layout for livestreaming . . . . . . . . . . 134
   26. Security Considerations . . . . . . . . . . . . . . . . . . . 135
   27. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 135
     27.1.  Matroska Element IDs Registry  . . . . . . . . . . . . . 136
     27.2.  Chapter Codec IDs Registry . . . . . . . . . . . . . . . 152
     27.3.  Media Types  . . . . . . . . . . . . . . . . . . . . . . 153
       27.3.1.  For files containing video tracks  . . . . . . . . . 153
       27.3.2.  For files containing audio tracks with no video
               tracks  . . . . . . . . . . . . . . . . . . . . . . . 154
       27.3.3.  For files containing a stereoscopic video track  . . 154
   28. Annex A: Historic Deprecated Elements . . . . . . . . . . . . 155
     28.1.  SilentTracks Element . . . . . . . . . . . . . . . . . . 155
     28.2.  SilentTrackNumber Element  . . . . . . . . . . . . . . . 156
     28.3.  BlockVirtual Element . . . . . . . . . . . . . . . . . . 156
     28.4.  ReferenceVirtual Element . . . . . . . . . . . . . . . . 156
     28.5.  Slices Element . . . . . . . . . . . . . . . . . . . . . 156
     28.6.  TimeSlice Element  . . . . . . . . . . . . . . . . . . . 156
     28.7.  LaceNumber Element . . . . . . . . . . . . . . . . . . . 156
     28.8.  FrameNumber Element  . . . . . . . . . . . . . . . . . . 157
     28.9.  BlockAdditionID Element  . . . . . . . . . . . . . . . . 157
     28.10. Delay Element  . . . . . . . . . . . . . . . . . . . . . 157
     28.11. SliceDuration Element  . . . . . . . . . . . . . . . . . 157
     28.12. ReferenceFrame Element . . . . . . . . . . . . . . . . . 157
     28.13. ReferenceOffset Element  . . . . . . . . . . . . . . . . 157
     28.14. ReferenceTimestamp Element . . . . . . . . . . . . . . . 157
     28.15. EncryptedBlock Element . . . . . . . . . . . . . . . . . 158
     28.16. MinCache Element . . . . . . . . . . . . . . . . . . . . 158
     28.17. MaxCache Element . . . . . . . . . . . . . . . . . . . . 158
     28.18. TrackOffset Element  . . . . . . . . . . . . . . . . . . 158
     28.19. CodecSettings Element  . . . . . . . . . . . . . . . . . 158
     28.20. CodecInfoURL Element . . . . . . . . . . . . . . . . . . 158
     28.21. CodecDownloadURL Element . . . . . . . . . . . . . . . . 159
     28.22. CodecDecodeAll Element . . . . . . . . . . . . . . . . . 159
     28.23. TrackOverlay Element . . . . . . . . . . . . . . . . . . 159
     28.24. AspectRatioType Element  . . . . . . . . . . . . . . . . 159
     28.25. GammaValue Element . . . . . . . . . . . . . . . . . . . 159
     28.26. FrameRate Element  . . . . . . . . . . . . . . . . . . . 159
     28.27. ChannelPositions Element . . . . . . . . . . . . . . . . 160
     28.28. TrickTrackUID Element  . . . . . . . . . . . . . . . . . 160
     28.29. TrickTrackSegmentUID Element . . . . . . . . . . . . . . 160
     28.30. TrickTrackFlag Element . . . . . . . . . . . . . . . . . 160
     28.31. TrickMasterTrackUID Element  . . . . . . . . . . . . . . 160
     28.32. TrickMasterTrackSegmentUID Element . . . . . . . . . . . 160
     28.33. ContentSignature Element . . . . . . . . . . . . . . . . 161

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     28.34. ContentSigKeyID Element  . . . . . . . . . . . . . . . . 161
     28.35. ContentSigAlgo Element . . . . . . . . . . . . . . . . . 161
     28.36. ContentSigHashAlgo Element . . . . . . . . . . . . . . . 161
     28.37. CueRefCluster Element  . . . . . . . . . . . . . . . . . 161
     28.38. CueRefNumber Element . . . . . . . . . . . . . . . . . . 161
     28.39. CueRefCodecState Element . . . . . . . . . . . . . . . . 161
     28.40. FileReferral Element . . . . . . . . . . . . . . . . . . 162
     28.41. FileUsedStartTime Element  . . . . . . . . . . . . . . . 162
     28.42. FileUsedEndTime Element  . . . . . . . . . . . . . . . . 162
     28.43. TagDefaultBogus Element  . . . . . . . . . . . . . . . . 162
   29. Normative References  . . . . . . . . . . . . . . . . . . . . 162
   30. Informative References  . . . . . . . . . . . . . . . . . . . 164
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . . 166

1.  Introduction

   Matroska is an audiovisual data container format.  It was derived
   from a project called [MCF], but diverges from it significantly
   because it is based on EBML (Extensible Binary Meta Language)
   [RFC8794], a binary derivative of XML.  EBML provides 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)
   *  It is an envelope in 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 such as:

   *  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 [RFC9110],
      FTP [RFC0959], SMB [SMB-CIFS], etc.)
   *  Menus (like DVDs have [DVD-Video])

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2.  Status of this document

   This document covers Matroska versions 1, 2, 3 and 4.  Matroska v4 is
   the current version.  Matroska 1 to 3 are no longer maintained.  No
   new elements are expected in files with version numbers 1, 2, or 3.

3.  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.
   Matroska Writer:  A data writer that creates Matroska documents.

4.  Matroska Overview

4.1.  Principles

   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).

4.2.  Updates to RFC 8794

   Because of an oversight, [RFC8794] reserved EBML ID 0x80, which is
   used by deployed Matroska implementations.  For this reason, this
   specification updates [RFC8794] to make 0x80 a legal EBML ID.
   Specifically, the following are changed in [RFC8794]:

   *  From Errata 7189

   OLD:

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   One-octet Element IDs MUST be between 0x81 and 0xFE.  These items are
   valuable because they are short, and they need to be used for
   commonly repeated elements.  Element IDs are to be allocated within
   this range according to the "RFC Required" policy [RFC8126].

   The following one-octet Element IDs are RESERVED: 0xFF and 0x80.

   NEW:

   One-octet Element IDs MUST be between 0x80 and 0xFE.  These items are
   valuable because they are short, and they need to be used for
   commonly repeated elements.  Element IDs are to be allocated within
   this range according to the "RFC Required" policy [RFC8126].

   The following one-octet Element ID is RESERVED: 0xFF.

   *  From Errata 7191

   OLD:

     +=========================+================+=================+
     | Element ID Octet Length | Range of Valid | Number of Valid |
     |                         |  Element IDs   |     Element IDs |
     +=========================+================+=================+
     |            1            |  0x81 - 0xFE   |             126 |
     +-------------------------+----------------+-----------------+

   NEW:

     +=========================+================+=================+
     | Element ID Octet Length | Range of Valid | Number of Valid |
     |                         |  Element IDs   |     Element IDs |
     +=========================+================+=================+
     |            1            |  0x80 - 0xFE   |             127 |
     +-------------------------+----------------+-----------------+

4.3.  Added EBML Constraints

   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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4.4.  Design Rules

   The Root Element and all Top-Levels Elements MUST use 4 octets for
   their EBML Element ID -- i.e. Segment and direct children of Segment.

   Legacy EBML/Matroska parsers did not handle Empty Elements properly,
   elements present in the file but with a length of zero.  They always
   assumed the value was 0 for integers/dates or 0x0p+0, the textual
   expression of floats using the [ISO9899] format, no matter the
   default value of the element which should have been used instead.
   Therefore, Matroska writers MUST NOT use EBML Empty Elements, if the
   element has a default value that is not 0 for integers/dates and
   0x0p+0 for floats.

   When adding new elements to Matroska, these rules apply:

   *  A non-mandatory integer/date Element MUST NOT have a default value
      other than 0.
   *  A non-mandatory float Element MUST NOT have a default value other
      than 0x0p+0.
   *  A non-mandatory string Element MUST NOT have a default value, as
      empty string cannot be defined in the XML Schema.

4.5.  Data Layout

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

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

   *  EBML Header
   *  Segment

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

   *  EBML Header
   *  Segment
   *  EBML Header
   *  Segment

   The following diagram represents a simple Matroska file, comprised of
   an EBML Document with an EBML Header, a Segment Element (the Root
   Element), and all eight Matroska Top-Level Elements.  In the

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   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 (Section 6.3),
   *  Info (Section 6.5),
   *  Tracks (Section 18),
   *  Chapters (Section 20),
   *  Cluster (Section 10),
   *  Cues (Section 22),
   *  Attachments (Section 21),
   *  and Tags (Section 6.8).

   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.

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

              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 | SegmentUUID      |
   |      |------------------|
   |      | SegmentFilename  |
   |      |------------------|
   |      | PrevUUID         |
   |      |------------------|
   |      | PrevFilename     |
   |      |------------------|
   |      | NextUUID         |
   |      |------------------|
   |      | NextFilename     |
   |      |------------------|
   |      | SegmentFamily    |
   |      |------------------|
   |      | ChapterTranslate |
   |      |------------------|
   |      | TimestampScale   |
   |      |------------------|
   |      | Duration         |
   |      |------------------|
   |      | DateUTC          |
   |      |------------------|
   |      | Title            |
   |      |------------------|
   |      | MuxingApp        |
   |      |------------------|
   |      | WritingApp       |
   |-------------------------|

    Figure 3: Representation of an Info Element and its Child Elements.

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

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

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

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

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

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

      Figure 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.
   In the rare case it doesn't, there should be a form of Segment
   linking with other Segments, possibly using Chapters, see Section 17.

   The Cluster Element helps to break up SimpleBlock or BlockGroup
   Elements and helps with seeking and error protection.  Every Cluster
   Element MUST contain a Timestamp Element.  This SHOULD be the
   Timestamp Element used to play the first Block in the Cluster
   Element, unless a different value is needed to accommodate for more
   Blocks, see Section 11.2.

   Cluster Elements contain one or more block element, such as
   BlockGroup or SimpleBlock elements.  In some situations, a Cluster
   Element MAY contain no block element, for example in a live recording
   when no data has been collected.

   A BlockGroup Element MAY contain a Block of data and any information
   relating directly to that Block.

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

      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 it
   belongs to, or the second Element if that Cluster contains a CRC-32
   element (Section 6.2)

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   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
   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.

   +-------------------------------------+
   | 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, fonts, webpages, etc.

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

            Figure 9: Representation of an 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.

5.  Matroska Schema

   This specification includes an EBML Schema, which defines the
   Elements and structure of Matroska using the EBML Schema elements and
   attributes defined in Section 11.1 of [RFC8794].  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.

5.1.  Segment Element

   id / type:  0x18538067 / master

   unknownsizeallowed: True

   path:  \Segment
   minOccurs / maxOccurs:  1 / 1
   definition:  The Root Element that contains all other Top-Level

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      Elements; see Section 4.5.

5.1.1.  SeekHead Element

   id / type:  0x114D9B74 / master
   path:  \Segment\SeekHead
   maxOccurs:  2
   definition:  Contains seeking information of Top-Level Elements; see
      Section 4.5.

5.1.1.1.  Seek Element

   id / type:  0x4DBB / master
   path:  \Segment\SeekHead\Seek
   minOccurs:  1
   definition:  Contains a single seek entry to an EBML Element.

5.1.1.1.1.  SeekID Element

   id / type:  0x53AB / binary
   length:  4
   path:  \Segment\SeekHead\Seek\SeekID
   minOccurs / maxOccurs:  1 / 1
   definition:  The binary EBML ID of a Top-Level Element.

5.1.1.1.2.  SeekPosition Element

   id / type:  0x53AC / uinteger
   path:  \Segment\SeekHead\Seek\SeekPosition
   minOccurs / maxOccurs:  1 / 1
   definition:  The Segment Position (Section 16) of a Top-Level
      Element.

5.1.2.  Info Element

   id / type:  0x1549A966 / master
   path:  \Segment\Info
   minOccurs / maxOccurs:  1 / 1

   recurring: True

   definition:  Contains general information about the Segment.

5.1.2.1.  SegmentUUID Element

   id / type:  0x73A4 / binary
   length:  16
   path:  \Segment\Info\SegmentUUID

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   maxOccurs:  1
   definition:  A randomly generated unique ID to identify the Segment
      amongst many others (128 bits).  It is equivalent to a UUID v4
      [RFC4122] with all bits randomly (or pseudo-randomly) chosen.  An
      actual UUID v4 value, where some bits are not random, MAY also be
      used.
   usage notes:  If the Segment is a part of a Linked Segment, then this
      Element is REQUIRED.  The value of the unique ID MUST contain at
      least one bit set to 1.

5.1.2.2.  SegmentFilename Element

   id / type:  0x7384 / utf-8
   path:  \Segment\Info\SegmentFilename
   maxOccurs:  1
   definition:  A filename corresponding to this Segment.

5.1.2.3.  PrevUUID Element

   id / type:  0x3CB923 / binary
   length:  16
   path:  \Segment\Info\PrevUUID
   maxOccurs:  1
   definition:  An ID to identify the previous Segment of a Linked
      Segment.
   usage notes:  If the Segment is a part of a Linked Segment that uses
      Hard Linking (Section 17.1), then either the PrevUUID or the
      NextUUID Element is REQUIRED.  If a Segment contains a PrevUUID
      but not a NextUUID, then it MAY be considered as the last Segment
      of the Linked Segment.  The PrevUUID MUST NOT be equal to the
      SegmentUUID.

5.1.2.4.  PrevFilename Element

   id / type:  0x3C83AB / utf-8
   path:  \Segment\Info\PrevFilename
   maxOccurs:  1
   definition:  A filename corresponding to the file of the previous
      Linked Segment.
   usage notes:  Provision of the previous filename is for display
      convenience, but PrevUUID SHOULD be considered authoritative for
      identifying the previous Segment in a Linked Segment.

5.1.2.5.  NextUUID Element

   id / type:  0x3EB923 / binary
   length:  16
   path:  \Segment\Info\NextUUID

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   maxOccurs:  1
   definition:  An ID to identify the next Segment of a Linked Segment.
   usage notes:  If the Segment is a part of a Linked Segment that uses
      Hard Linking (Section 17.1), then either the PrevUUID or the
      NextUUID Element is REQUIRED.  If a Segment contains a NextUUID
      but not a PrevUUID, then it MAY be considered as the first Segment
      of the Linked Segment.  The NextUUID MUST NOT be equal to the
      SegmentUUID.

5.1.2.6.  NextFilename Element

   id / type:  0x3E83BB / utf-8
   path:  \Segment\Info\NextFilename
   maxOccurs:  1
   definition:  A filename corresponding to the file of the next Linked
      Segment.
   usage notes:  Provision of the next filename is for display
      convenience, but NextUUID SHOULD be considered authoritative for
      identifying the Next Segment.

5.1.2.7.  SegmentFamily Element

   id / type:  0x4444 / binary
   length:  16
   path:  \Segment\Info\SegmentFamily
   definition:  A unique ID that all Segments of a Linked Segment MUST
      share (128 bits).  It is equivalent to a UUID v4 [RFC4122] with
      all bits randomly (or pseudo-randomly) chosen.  An actual UUID v4
      value, where some bits are not random, MAY also be used.
   usage notes:  If the Segment Info contains a ChapterTranslate
      element, this Element is REQUIRED.

5.1.2.8.  ChapterTranslate Element

   id / type:  0x6924 / master
   path:  \Segment\Info\ChapterTranslate
   definition:  The mapping between this Segment and a segment value in
      the given Chapter Codec.
   rationale:  Chapter Codec may need to address different segments, but
      they may not know of the way to identify such segment when stored
      in Matroska.  This element and its child elements add a way to map
      the internal segments known to the Chapter Codec to the Segment
      IDs in Matroska.  This allows remuxing a file with Chapter Codec
      without changing the content of the codec data, just the Segment
      mapping.

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5.1.2.8.1.  ChapterTranslateID Element

   id / type:  0x69A5 / binary
   path:  \Segment\Info\ChapterTranslate\ChapterTranslateID
   minOccurs / maxOccurs:  1 / 1
   definition:  The binary value used to represent this Segment in the
      chapter codec data.  The format depends on the ChapProcessCodecID
      used; see Section 5.1.7.1.4.15.

5.1.2.8.2.  ChapterTranslateCodec Element

   id / type:  0x69BF / uinteger
   path:  \Segment\Info\ChapterTranslate\ChapterTranslateCodec
   minOccurs / maxOccurs:  1 / 1
   definition:  This ChapterTranslate applies to this chapter codec of
      the given chapter edition(s); see Section 5.1.7.1.4.15.

   defined values:

         +=======+=================+============================+
         | value | label           | definition                 |
         +=======+=================+============================+
         | 0     | Matroska Script | Chapter commands using the |
         |       |                 | Matroska Script codec.     |
         +-------+-----------------+----------------------------+
         | 1     | DVD-menu        | Chapter commands using the |
         |       |                 | DVD-like codec.            |
         +-------+-----------------+----------------------------+

                  Table 1: ChapterTranslateCodec values

5.1.2.8.3.  ChapterTranslateEditionUID Element

   id / type:  0x69FC / uinteger
   path:  \Segment\Info\ChapterTranslate\ChapterTranslateEditionUID
   definition:  Specify a chapter edition UID on which this
      ChapterTranslate applies.
   usage notes:  When no ChapterTranslateEditionUID is specified in the
      ChapterTranslate, the ChapterTranslate applies to all chapter
      editions found in the Segment using the given
      ChapterTranslateCodec.

5.1.2.9.  TimestampScale Element

   id / type / default:  0x2AD7B1 / uinteger / 1000000
   range:  not 0
   path:  \Segment\Info\TimestampScale
   minOccurs / maxOccurs:  1 / 1

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   definition:  Base unit for Segment Ticks and Track Ticks, in
      nanoseconds.  A TimestampScale value of 1000000 means scaled
      timestamps in the Segment are expressed in milliseconds; see
      Section 11 on how to interpret timestamps.

5.1.2.10.  Duration Element

   id / type:  0x4489 / float
   range:  > 0x0p+0
   path:  \Segment\Info\Duration
   maxOccurs:  1
   definition:  Duration of the Segment, expressed in Segment Ticks
      which is based on TimestampScale; see Section 11.1.

5.1.2.11.  DateUTC Element

   id / type:  0x4461 / date
   path:  \Segment\Info\DateUTC
   maxOccurs:  1
   definition:  The date and time that the Segment was created by the
      muxing application or library.

5.1.2.12.  Title Element

   id / type:  0x7BA9 / utf-8
   path:  \Segment\Info\Title
   maxOccurs:  1
   definition:  General name of the Segment.

5.1.2.13.  MuxingApp Element

   id / type:  0x4D80 / utf-8
   path:  \Segment\Info\MuxingApp
   minOccurs / maxOccurs:  1 / 1
   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.

5.1.2.14.  WritingApp Element

   id / type:  0x5741 / utf-8
   path:  \Segment\Info\WritingApp
   minOccurs / maxOccurs:  1 / 1
   definition:  Writing application (example: "mkvmerge-0.3.3").
   usage notes:  Include the full name of the application followed by
      the version number.

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5.1.3.  Cluster Element

   id / type:  0x1F43B675 / master

   unknownsizeallowed: True

   path:  \Segment\Cluster
   definition:  The Top-Level Element containing the (monolithic) Block
      structure.

5.1.3.1.  Timestamp Element

   id / type:  0xE7 / uinteger
   path:  \Segment\Cluster\Timestamp
   minOccurs / maxOccurs:  1 / 1
   definition:  Absolute timestamp of the cluster, expressed in Segment
      Ticks which is based on TimestampScale; see Section 11.1.
   usage notes:  This element SHOULD be the first child element of the
      Cluster it belongs to, or the second if that Cluster contains a
      CRC-32 element (Section 6.2).

5.1.3.2.  Position Element

   id / type:  0xA7 / uinteger
   path:  \Segment\Cluster\Position
   maxOccurs:  1
   maxver:  4
   definition:  The Segment Position of the Cluster in the Segment (0 in
      live streams).  It might help to resynchronise offset on damaged
      streams.

5.1.3.3.  PrevSize Element

   id / type:  0xAB / uinteger
   path:  \Segment\Cluster\PrevSize
   maxOccurs:  1
   definition:  Size of the previous Cluster, in octets.  Can be useful
      for backward playing.

5.1.3.4.  SimpleBlock Element

   id / type:  0xA3 / binary
   path:  \Segment\Cluster\SimpleBlock
   minver:  2
   definition:  Similar to Block, see Section 10.1, but without all the
      extra information, mostly used to reduced overhead when no extra
      feature is needed; see Section 10.2 on SimpleBlock Structure.

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5.1.3.5.  BlockGroup Element

   id / type:  0xA0 / master
   path:  \Segment\Cluster\BlockGroup
   definition:  Basic container of information containing a single Block
      and information specific to that Block.

5.1.3.5.1.  Block Element

   id / type:  0xA1 / binary
   path:  \Segment\Cluster\BlockGroup\Block
   minOccurs / maxOccurs:  1 / 1
   definition:  Block containing the actual data to be rendered and a
      timestamp relative to the Cluster Timestamp; see Section 10.1 on
      Block Structure.

5.1.3.5.2.  BlockAdditions Element

   id / type:  0x75A1 / master
   path:  \Segment\Cluster\BlockGroup\BlockAdditions
   maxOccurs:  1
   definition:  Contain additional binary data to complete the main one;
      see Codec BlockAdditions section of [MatroskaCodec] for more
      information.  An EBML parser that has no knowledge of the Block
      structure could still see and use/skip these data.

5.1.3.5.2.1.  BlockMore Element

   id / type:  0xA6 / master
   path:  \Segment\Cluster\BlockGroup\BlockAdditions\BlockMore
   minOccurs:  1
   definition:  Contain the BlockAdditional and some parameters.

5.1.3.5.2.2.  BlockAdditional Element

   id / type:  0xA5 / binary
   path:  \Segment\Cluster\BlockGroup\BlockAdditions\BlockMore\BlockAddi
      tional
   minOccurs / maxOccurs:  1 / 1
   definition:  Interpreted by the codec as it wishes (using the
      BlockAddID).

5.1.3.5.2.3.  BlockAddID Element

   id / type / default:  0xEE / uinteger / 1
   range:  not 0
   path:  \Segment\Cluster\BlockGroup\BlockAdditions\BlockMore\BlockAddI
      D

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   minOccurs / maxOccurs:  1 / 1
   definition:  An ID to identify how to interpret the BlockAdditional
      data; see Codec BlockAdditions section of [MatroskaCodec] for more
      information.  A value of 1 indicates that the meaning of the
      BlockAdditional data is defined by the codec.  Any other value
      indicates the meaning of the BlockAdditional data is found in the
      BlockAddIDType found in the TrackEntry.
   usage notes:  Each BlockAddID value MUST be unique between all
      BlockMore elements found in a BlockAdditions.
   usage notes:  To keep MaxBlockAdditionID as low as possible, small
      values SHOULD be used.

5.1.3.5.3.  BlockDuration Element

   id / type:  0x9B / uinteger
   path:  \Segment\Cluster\BlockGroup\BlockDuration
   minOccurs / maxOccurs:  see implementation notes / 1
   definition:  The duration of the Block, expressed in Track Ticks; see
      Section 11.1.  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:

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

                Table 2: BlockDuration implementation notes

5.1.3.5.4.  ReferencePriority Element

   id / type / default:  0xFA / uinteger / 0
   path:  \Segment\Cluster\BlockGroup\ReferencePriority
   minOccurs / maxOccurs:  1 / 1
   definition:  This frame is referenced and has the specified cache

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      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.

5.1.3.5.5.  ReferenceBlock Element

   id / type:  0xFB / integer
   path:  \Segment\Cluster\BlockGroup\ReferenceBlock
   definition:  A timestamp value, relative to the timestamp of the
      Block in this BlockGroup, expressed in Track Ticks; see
      Section 11.1.  This is used to reference other frames necessary to
      decode this frame.  The relative value SHOULD correspond to a
      valid Block this Block depends on.  Historically Matroska Writer
      didn't write the actual Block(s) this Block depends on, but _some_
      Block in the past.

   The value "0" MAY also be used to signify this Block cannot be
   decoded on its own, but without knownledge of which Block is
   necessary.  In this case, other ReferenceBlock MUST NOT be found in
   the same BlockGroup.

   If the BlockGroup doesn't have any ReferenceBlock element, then the
   Block it contains can be decoded without using any other Block data.

5.1.3.5.6.  CodecState Element

   id / type:  0xA4 / binary
   path:  \Segment\Cluster\BlockGroup\CodecState
   maxOccurs:  1
   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.

5.1.3.5.7.  DiscardPadding Element

   id / type:  0x75A2 / integer
   path:  \Segment\Cluster\BlockGroup\DiscardPadding
   maxOccurs:  1
   minver:  4
   definition:  Duration of the silent data added to the Block,
      expressed in Matroska Ticks -- i.e., in nanoseconds; see
      Section 11.1 (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.

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5.1.4.  Tracks Element

   id / type:  0x1654AE6B / master
   path:  \Segment\Tracks
   maxOccurs:  1

   recurring: True

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

5.1.4.1.  TrackEntry Element

   id / type:  0xAE / master
   path:  \Segment\Tracks\TrackEntry
   minOccurs:  1
   definition:  Describes a track with all Elements.

5.1.4.1.1.  TrackNumber Element

   id / type:  0xD7 / uinteger
   range:  not 0
   path:  \Segment\Tracks\TrackEntry\TrackNumber
   minOccurs / maxOccurs:  1 / 1
   definition:  The track number as used in the Block Header.

5.1.4.1.2.  TrackUID Element

   id / type:  0x73C5 / uinteger
   range:  not 0
   path:  \Segment\Tracks\TrackEntry\TrackUID
   minOccurs / maxOccurs:  1 / 1
   definition:  A unique ID to identify the Track.

   stream copy: True (Section 8)

5.1.4.1.3.  TrackType Element

   id / type:  0x83 / uinteger
   path:  \Segment\Tracks\TrackEntry\TrackType
   minOccurs / maxOccurs:  1 / 1
   definition:  The TrackType defines the type of each frame found in
      the Track.  The value SHOULD be stored on 1 octet.

   defined values:

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      +=======+==========+==========================================+
      | value | label    | each frame contains                      |
      +=======+==========+==========================================+
      | 1     | video    | An image.                                |
      +-------+----------+------------------------------------------+
      | 2     | audio    | Audio samples.                           |
      +-------+----------+------------------------------------------+
      | 3     | complex  | A mix of different other TrackType.  The |
      |       |          | codec needs to define how the Matroska   |
      |       |          | Player should interpret such data.       |
      +-------+----------+------------------------------------------+
      | 16    | logo     | An image to be rendered over the video   |
      |       |          | track(s).                                |
      +-------+----------+------------------------------------------+
      | 17    | subtitle | Subtitle or closed caption data to be    |
      |       |          | rendered over the video track(s).        |
      +-------+----------+------------------------------------------+
      | 18    | buttons  | Interactive button(s) to be rendered     |
      |       |          | over the video track(s).                 |
      +-------+----------+------------------------------------------+
      | 32    | control  | Metadata used to control the player of   |
      |       |          | the Matroska Player.                     |
      +-------+----------+------------------------------------------+
      | 33    | metadata | Timed metadata that can be passed on to  |
      |       |          | the Matroska Player.                     |
      +-------+----------+------------------------------------------+

                         Table 3: TrackType values

   stream copy: True (Section 8)

5.1.4.1.4.  FlagEnabled Element

   id / type / default:  0xB9 / uinteger / 1
   range:  0-1
   path:  \Segment\Tracks\TrackEntry\FlagEnabled
   minOccurs / maxOccurs:  1 / 1
   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.

5.1.4.1.5.  FlagDefault Element

   id / type / default:  0x88 / uinteger / 1
   range:  0-1
   path:  \Segment\Tracks\TrackEntry\FlagDefault
   minOccurs / maxOccurs:  1 / 1

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   definition:  Set if that track (audio, video or subs) is eligible for
      automatic selection by the player; see Section 19 for more
      details.

5.1.4.1.6.  FlagForced Element

   id / type / default:  0x55AA / uinteger / 0
   range:  0-1
   path:  \Segment\Tracks\TrackEntry\FlagForced
   minOccurs / maxOccurs:  1 / 1
   definition:  Applies only to subtitles.  Set if that track is
      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 19 for more details.

5.1.4.1.7.  FlagHearingImpaired Element

   id / type:  0x55AB / uinteger
   range:  0-1
   path:  \Segment\Tracks\TrackEntry\FlagHearingImpaired
   maxOccurs:  1
   minver:  4
   definition:  Set to 1 if and only if that track is suitable for users
      with hearing impairments.

5.1.4.1.8.  FlagVisualImpaired Element

   id / type:  0x55AC / uinteger
   range:  0-1
   path:  \Segment\Tracks\TrackEntry\FlagVisualImpaired
   maxOccurs:  1
   minver:  4
   definition:  Set to 1 if and only if that track is suitable for users
      with visual impairments.

5.1.4.1.9.  FlagTextDescriptions Element

   id / type:  0x55AD / uinteger
   range:  0-1
   path:  \Segment\Tracks\TrackEntry\FlagTextDescriptions
   maxOccurs:  1
   minver:  4
   definition:  Set to 1 if and only if that track contains textual
      descriptions of video content.

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5.1.4.1.10.  FlagOriginal Element

   id / type:  0x55AE / uinteger
   range:  0-1
   path:  \Segment\Tracks\TrackEntry\FlagOriginal
   maxOccurs:  1
   minver:  4
   definition:  Set to 1 if and only if that track is in the content's
      original language.

5.1.4.1.11.  FlagCommentary Element

   id / type:  0x55AF / uinteger
   range:  0-1
   path:  \Segment\Tracks\TrackEntry\FlagCommentary
   maxOccurs:  1
   minver:  4
   definition:  Set to 1 if and only if that track contains commentary.

5.1.4.1.12.  FlagLacing Element

   id / type / default:  0x9C / uinteger / 1
   range:  0-1
   path:  \Segment\Tracks\TrackEntry\FlagLacing
   minOccurs / maxOccurs:  1 / 1
   definition:  Set to 1 if the track MAY contain blocks using lacing.
      When set to 0 all blocks MUST have their lacing flags set to No
      lacing; see Section 10.3 on Block Lacing.

5.1.4.1.13.  DefaultDuration Element

   id / type:  0x23E383 / uinteger
   range:  not 0
   path:  \Segment\Tracks\TrackEntry\DefaultDuration
   maxOccurs:  1
   definition:  Number of nanoseconds per frame, expressed in Matroska
      Ticks -- i.e., in nanoseconds; see Section 11.1 (frame in the
      Matroska sense -- one Element put into a (Simple)Block).

   stream copy: True (Section 8)

5.1.4.1.14.  DefaultDecodedFieldDuration Element

   id / type:  0x234E7A / uinteger
   range:  not 0
   path:  \Segment\Tracks\TrackEntry\DefaultDecodedFieldDuration
   maxOccurs:  1
   minver:  4

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   definition:  The period between two successive fields at the output
      of the decoding process, expressed in Matroska Ticks -- i.e., in
      nanoseconds; see Section 11.1. see Section 9 for more information

   stream copy: True (Section 8)

5.1.4.1.15.  TrackTimestampScale Element

   id / type / default:  0x23314F / float / 0x1p+0
   range:  > 0x0p+0
   path:  \Segment\Tracks\TrackEntry\TrackTimestampScale
   minOccurs / maxOccurs:  1 / 1
   maxver:  3
   definition:  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).

   stream copy: True (Section 8)

5.1.4.1.16.  MaxBlockAdditionID Element

   id / type / default:  0x55EE / uinteger / 0
   path:  \Segment\Tracks\TrackEntry\MaxBlockAdditionID
   minOccurs / maxOccurs:  1 / 1
   definition:  The maximum value of BlockAddID (Section 5.1.3.5.2.3).
      A value 0 means there is no BlockAdditions (Section 5.1.3.5.2) for
      this track.

5.1.4.1.17.  BlockAdditionMapping Element

   id / type:  0x41E4 / master
   path:  \Segment\Tracks\TrackEntry\BlockAdditionMapping
   minver:  4
   definition:  Contains elements that extend the track format, by
      adding content either to each frame, with BlockAddID
      (Section 5.1.3.5.2.3), or to the track as a whole with
      BlockAddIDExtraData.

5.1.4.1.17.1.  BlockAddIDValue Element

   id / type:  0x41F0 / uinteger
   range:  >=2
   path:  \Segment\Tracks\TrackEntry\BlockAdditionMapping\BlockAddIDValu
      e
   maxOccurs:  1
   minver:  4
   definition:  If the track format extension needs content beside

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      frames, the value refers to the BlockAddID (Section 5.1.3.5.2.3),
      value being described.
   usage notes:  To keep MaxBlockAdditionID as low as possible, small
      values SHOULD be used.

5.1.4.1.17.2.  BlockAddIDName Element

   id / type:  0x41A4 / string
   path:  \Segment\Tracks\TrackEntry\BlockAdditionMapping\BlockAddIDName
   maxOccurs:  1
   minver:  4
   definition:  A human-friendly name describing the type of
      BlockAdditional data, as defined by the associated Block
      Additional Mapping.

5.1.4.1.17.3.  BlockAddIDType Element

   id / type / default:  0x41E7 / uinteger / 0
   path:  \Segment\Tracks\TrackEntry\BlockAdditionMapping\BlockAddIDType
   minOccurs / maxOccurs:  1 / 1
   minver:  4
   definition:  Stores the registered identifier of the Block Additional
      Mapping to define how the BlockAdditional data should be handled.
   usage notes:  If BlockAddIDType is 0, the BlockAddIDValue and
      corresponding BlockAddID values MUST be 1.

5.1.4.1.17.4.  BlockAddIDExtraData Element

   id / type:  0x41ED / binary
   path:  \Segment\Tracks\TrackEntry\BlockAdditionMapping\BlockAddIDExtr
      aData
   maxOccurs:  1
   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.

5.1.4.1.18.  Name Element

   id / type:  0x536E / utf-8
   path:  \Segment\Tracks\TrackEntry\Name
   maxOccurs:  1
   definition:  A human-readable track name.

5.1.4.1.19.  Language Element

   id / type / default:  0x22B59C / string / eng

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   path:  \Segment\Tracks\TrackEntry\Language
   minOccurs / maxOccurs:  1 / 1
   definition:  The language of the track, in the Matroska languages
      form; see Section 12 on language codes.  This Element MUST be
      ignored if the LanguageBCP47 Element is used in the same
      TrackEntry.

5.1.4.1.20.  LanguageBCP47 Element

   id / type:  0x22B59D / string
   path:  \Segment\Tracks\TrackEntry\LanguageBCP47
   maxOccurs:  1
   minver:  4
   definition:  The language of the track, in the [BCP47] form; see
      Section 12 on language codes.  If this Element is used, then any
      Language Elements used in the same TrackEntry MUST be ignored.

5.1.4.1.21.  CodecID Element

   id / type:  0x86 / string
   path:  \Segment\Tracks\TrackEntry\CodecID
   minOccurs / maxOccurs:  1 / 1
   definition:  An ID corresponding to the codec, see [MatroskaCodec]
      for more info.

   stream copy: True (Section 8)

5.1.4.1.22.  CodecPrivate Element

   id / type:  0x63A2 / binary
   path:  \Segment\Tracks\TrackEntry\CodecPrivate
   maxOccurs:  1
   definition:  Private data only known to the codec.

   stream copy: True (Section 8)

5.1.4.1.23.  CodecName Element

   id / type:  0x258688 / utf-8
   path:  \Segment\Tracks\TrackEntry\CodecName
   maxOccurs:  1
   definition:  A human-readable string specifying the codec.

5.1.4.1.24.  AttachmentLink Element

   id / type:  0x7446 / uinteger
   range:  not 0
   path:  \Segment\Tracks\TrackEntry\AttachmentLink

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   maxOccurs:  1
   maxver:  3
   definition:  The UID of an attachment that is used by this codec.
   usage notes:  The value MUST match the FileUID value of an attachment
      found in this Segment.

5.1.4.1.25.  CodecDelay Element

   id / type / default:  0x56AA / uinteger / 0
   path:  \Segment\Tracks\TrackEntry\CodecDelay
   minOccurs / maxOccurs:  1 / 1
   minver:  4
   definition:  CodecDelay is The codec-built-in delay, expressed in
      Matroska Ticks -- i.e., in nanoseconds; see Section 11.1.  It
      represents the amount of codec samples that will be discarded by
      the decoder during playback.  This timestamp value MUST be
      subtracted from each frame timestamp in order to get the timestamp
      that will be actually played.  The value SHOULD be small so the
      muxing of tracks with the same actual timestamp are in the same
      Cluster.

   stream copy: True (Section 8)

5.1.4.1.26.  SeekPreRoll Element

   id / type / default:  0x56BB / uinteger / 0
   path:  \Segment\Tracks\TrackEntry\SeekPreRoll
   minOccurs / maxOccurs:  1 / 1
   minver:  4
   definition:  After a discontinuity, SeekPreRoll is the duration of
      the data the decoder MUST decode before the decoded data is valid,
      expressed in Matroska Ticks -- i.e., in nanoseconds; see
      Section 11.1.

   stream copy: True (Section 8)

5.1.4.1.27.  TrackTranslate Element

   id / type:  0x6624 / master
   path:  \Segment\Tracks\TrackEntry\TrackTranslate
   definition:  The mapping between this TrackEntry and a track value in
      the given Chapter Codec.
   rationale:  Chapter Codec may need to address content in specific
      track, but they may not know of the way to identify tracks in
      Matroska.  This element and its child elements add a way to map
      the internal tracks known to the Chapter Codec to the track IDs in
      Matroska.  This allows remuxing a file with Chapter Codec without
      changing the content of the codec data, just the track mapping.

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5.1.4.1.27.1.  TrackTranslateTrackID Element

   id / type:  0x66A5 / binary
   path:  \Segment\Tracks\TrackEntry\TrackTranslate\TrackTranslateTrackI
      D
   minOccurs / maxOccurs:  1 / 1
   definition:  The binary value used to represent this TrackEntry in
      the chapter codec data.  The format depends on the
      ChapProcessCodecID used; see Section 5.1.7.1.4.15.

5.1.4.1.27.2.  TrackTranslateCodec Element

   id / type:  0x66BF / uinteger
   path:  \Segment\Tracks\TrackEntry\TrackTranslate\TrackTranslateCodec
   minOccurs / maxOccurs:  1 / 1
   definition:  This TrackTranslate applies to this chapter codec of the
      given chapter edition(s); see Section 5.1.7.1.4.15.

   defined values:

         +=======+=================+============================+
         | value | label           | definition                 |
         +=======+=================+============================+
         | 0     | Matroska Script | Chapter commands using the |
         |       |                 | Matroska Script codec.     |
         +-------+-----------------+----------------------------+
         | 1     | DVD-menu        | Chapter commands using the |
         |       |                 | DVD-like codec.            |
         +-------+-----------------+----------------------------+

                   Table 4: TrackTranslateCodec values

5.1.4.1.27.3.  TrackTranslateEditionUID Element

   id / type:  0x66FC / uinteger
   path:  \Segment\Tracks\TrackEntry\TrackTranslate\TrackTranslateEditio
      nUID
   definition:  Specify a chapter edition UID on which this
      TrackTranslate applies.
   usage notes:  When no TrackTranslateEditionUID is specified in the
      TrackTranslate, the TrackTranslate applies to all chapter editions
      found in the Segment using the given TrackTranslateCodec.

5.1.4.1.28.  Video Element

   id / type:  0xE0 / master
   path:  \Segment\Tracks\TrackEntry\Video
   maxOccurs:  1

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   definition:  Video settings.

5.1.4.1.28.1.  FlagInterlaced Element

   id / type / default:  0x9A / uinteger / 0
   path:  \Segment\Tracks\TrackEntry\Video\FlagInterlaced
   minOccurs / maxOccurs:  1 / 1
   minver:  2
   definition:  Specify whether the video frames in this track are
      interlaced.

   defined values:

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

                       Table 5: FlagInterlaced values

   stream copy: True (Section 8)

5.1.4.1.28.2.  FieldOrder Element

   id / type / default:  0x9D / uinteger / 2
   path:  \Segment\Tracks\TrackEntry\Video\FieldOrder
   minOccurs / maxOccurs:  1 / 1
   minver:  4
   definition:  Specify the field ordering of video frames in this
      track.

   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

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

   stream copy: True (Section 8)

5.1.4.1.28.3.  StereoMode Element

   id / type / default:  0x53B8 / uinteger / 0
   path:  \Segment\Tracks\TrackEntry\Video\StereoMode
   minOccurs / maxOccurs:  1 / 1
   minver:  3
   definition:  Stereo-3D video mode.  There are some more details in
      Section 18.10.

   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

   stream copy: True (Section 8)

5.1.4.1.28.4.  AlphaMode Element

   id / type / default:  0x53C0 / uinteger / 0
   path:  \Segment\Tracks\TrackEntry\Video\AlphaMode
   minOccurs / maxOccurs:  1 / 1
   minver:  3
   definition:  Indicate whether the BlockAdditional Element with

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      BlockAddID of "1" contains Alpha data, as defined by to the Codec
      Mapping for the CodecID.  Undefined values SHOULD NOT be used as
      the behavior of known implementations is different (considered
      either as 0 or 1).

   defined values:

     +=======+=========+============================================+
     | value | label   | definition                                 |
     +=======+=========+============================================+
     | 0     | none    | The BlockAdditional Element with           |
     |       |         | BlockAddID of "1" does not exist or SHOULD |
     |       |         | NOT be considered as containing such data. |
     +-------+---------+--------------------------------------------+
     | 1     | present | The BlockAdditional Element with           |
     |       |         | BlockAddID of "1" contains alpha channel   |
     |       |         | data.                                      |
     +-------+---------+--------------------------------------------+

                        Table 8: AlphaMode values

   stream copy: True (Section 8)

5.1.4.1.28.5.  OldStereoMode Element

   id / type:  0x53B9 / uinteger
   path:  \Segment\Tracks\TrackEntry\Video\OldStereoMode
   maxOccurs:  1
   maxver:  2
   definition:  Bogus StereoMode value used in old versions of
      libmatroska.

   restrictions:

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

                           Table 9: OldStereoMode
                                   values

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   usage notes:  This Element MUST NOT be used.  It was an incorrect
      value used in libmatroska up to 0.9.0.

5.1.4.1.28.6.  PixelWidth Element

   id / type:  0xB0 / uinteger
   range:  not 0
   path:  \Segment\Tracks\TrackEntry\Video\PixelWidth
   minOccurs / maxOccurs:  1 / 1
   definition:  Width of the encoded video frames in pixels.

   stream copy: True (Section 8)

5.1.4.1.28.7.  PixelHeight Element

   id / type:  0xBA / uinteger
   range:  not 0
   path:  \Segment\Tracks\TrackEntry\Video\PixelHeight
   minOccurs / maxOccurs:  1 / 1
   definition:  Height of the encoded video frames in pixels.

   stream copy: True (Section 8)

5.1.4.1.28.8.  PixelCropBottom Element

   id / type / default:  0x54AA / uinteger / 0
   path:  \Segment\Tracks\TrackEntry\Video\PixelCropBottom
   minOccurs / maxOccurs:  1 / 1
   definition:  The number of video pixels to remove at the bottom of
      the image.

   stream copy: True (Section 8)

5.1.4.1.28.9.  PixelCropTop Element

   id / type / default:  0x54BB / uinteger / 0
   path:  \Segment\Tracks\TrackEntry\Video\PixelCropTop
   minOccurs / maxOccurs:  1 / 1
   definition:  The number of video pixels to remove at the top of the
      image.

   stream copy: True (Section 8)

5.1.4.1.28.10.  PixelCropLeft Element

   id / type / default:  0x54CC / uinteger / 0
   path:  \Segment\Tracks\TrackEntry\Video\PixelCropLeft
   minOccurs / maxOccurs:  1 / 1

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

   stream copy: True (Section 8)

5.1.4.1.28.11.  PixelCropRight Element

   id / type / default:  0x54DD / uinteger / 0
   path:  \Segment\Tracks\TrackEntry\Video\PixelCropRight
   minOccurs / maxOccurs:  1 / 1
   definition:  The number of video pixels to remove on the right of the
      image.

   stream copy: True (Section 8)

5.1.4.1.28.12.  DisplayWidth Element

   id / type:  0x54B0 / uinteger
   range:  not 0
   path:  \Segment\Tracks\TrackEntry\Video\DisplayWidth
   maxOccurs:  1
   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 10: DisplayWidth implementation notes

   stream copy: True (Section 8)

5.1.4.1.28.13.  DisplayHeight Element

   id / type:  0x54BA / uinteger
   range:  not 0
   path:  \Segment\Tracks\TrackEntry\Video\DisplayHeight
   maxOccurs:  1
   definition:  Height of the video frames to display.  Applies to the
      video frame after cropping (PixelCrop* Elements).

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   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 11: DisplayHeight implementation notes

   stream copy: True (Section 8)

5.1.4.1.28.14.  DisplayUnit Element

   id / type / default:  0x54B2 / uinteger / 0
   path:  \Segment\Tracks\TrackEntry\Video\DisplayUnit
   minOccurs / maxOccurs:  1 / 1
   definition:  How DisplayWidth & DisplayHeight are interpreted.

   restrictions:

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

                       Table 12: DisplayUnit values

5.1.4.1.28.15.  UncompressedFourCC Element

   id / type:  0x2EB524 / binary
   length:  4
   path:  \Segment\Tracks\TrackEntry\Video\UncompressedFourCC
   minOccurs / maxOccurs:  see implementation notes / 1
   definition:  Specify the uncompressed pixel format used for the

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      Track's data as a FourCC.  This value is similar in scope to the
      biCompression value of AVI's BITMAPINFO [AVIFormat].  There is no
      definitive list of FourCC values, nor an official registry.  Some
      common values for YUV pixel formats can be found at [MSYUV8],
      [MSYUV16] and [FourCC-YUV].  Some common values for uncompressed
      RGB pixel formats can be found at [MSRGB] and [FourCC-RGB].

   notes:

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

            Table 13: UncompressedFourCC implementation notes

   stream copy: True (Section 8)

5.1.4.1.28.16.  Colour Element

   id / type:  0x55B0 / master
   path:  \Segment\Tracks\TrackEntry\Video\Colour
   maxOccurs:  1
   minver:  4
   definition:  Settings describing the colour format.

   stream copy: True (Section 8)

5.1.4.1.28.17.  MatrixCoefficients Element

   id / type / default:  0x55B1 / uinteger / 2
   path:  \Segment\Tracks\TrackEntry\Video\Colour\MatrixCoefficients
   minOccurs / maxOccurs:  1 / 1
   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 [ITU-H.273].

   restrictions:

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

                    Table 14: MatrixCoefficients values

   stream copy: True (Section 8)

5.1.4.1.28.18.  BitsPerChannel Element

   id / type / default:  0x55B2 / uinteger / 0
   path:  \Segment\Tracks\TrackEntry\Video\Colour\BitsPerChannel
   minOccurs / maxOccurs:  1 / 1
   minver:  4
   definition:  Number of decoded bits per channel.  A value of 0
      indicates that the BitsPerChannel is unspecified.

   stream copy: True (Section 8)

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5.1.4.1.28.19.  ChromaSubsamplingHorz Element

   id / type:  0x55B3 / uinteger
   path:  \Segment\Tracks\TrackEntry\Video\Colour\ChromaSubsamplingHorz
   maxOccurs:  1
   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.

   stream copy: True (Section 8)

5.1.4.1.28.20.  ChromaSubsamplingVert Element

   id / type:  0x55B4 / uinteger
   path:  \Segment\Tracks\TrackEntry\Video\Colour\ChromaSubsamplingVert
   maxOccurs:  1
   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.

   stream copy: True (Section 8)

5.1.4.1.28.21.  CbSubsamplingHorz Element

   id / type:  0x55B5 / uinteger
   path:  \Segment\Tracks\TrackEntry\Video\Colour\CbSubsamplingHorz
   maxOccurs:  1
   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.

   stream copy: True (Section 8)

5.1.4.1.28.22.  CbSubsamplingVert Element

   id / type:  0x55B6 / uinteger
   path:  \Segment\Tracks\TrackEntry\Video\Colour\CbSubsamplingVert
   maxOccurs:  1
   minver:  4
   definition:  The amount of pixels to remove in the Cb channel for

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      every pixel not removed vertically.  This is additive with
      ChromaSubsamplingVert.

   stream copy: True (Section 8)

5.1.4.1.28.23.  ChromaSitingHorz Element

   id / type / default:  0x55B7 / uinteger / 0
   path:  \Segment\Tracks\TrackEntry\Video\Colour\ChromaSitingHorz
   minOccurs / maxOccurs:  1 / 1
   minver:  4
   definition:  How chroma is subsampled horizontally.

   restrictions:

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

                                 Table 15:
                          ChromaSitingHorz values

   stream copy: True (Section 8)

5.1.4.1.28.24.  ChromaSitingVert Element

   id / type / default:  0x55B8 / uinteger / 0
   path:  \Segment\Tracks\TrackEntry\Video\Colour\ChromaSitingVert
   minOccurs / maxOccurs:  1 / 1
   minver:  4
   definition:  How chroma is subsampled vertically.

   restrictions:

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

                                Table 16:
                             ChromaSitingVert
                                  values

   stream copy: True (Section 8)

5.1.4.1.28.25.  Range Element

   id / type / default:  0x55B9 / uinteger / 0
   path:  \Segment\Tracks\TrackEntry\Video\Colour\Range
   minOccurs / maxOccurs:  1 / 1
   minver:  4
   definition:  Clipping of the color ranges.

   restrictions:

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

                           Table 17: Range values

   stream copy: True (Section 8)

5.1.4.1.28.26.  TransferCharacteristics Element

   id / type / default:  0x55BA / uinteger / 2
   path:  \Segment\Tracks\TrackEntry\Video\Colour\TransferCharacteristic
      s
   minOccurs / maxOccurs:  1 / 1

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   minver:  4
   definition:  The transfer characteristics of the video.  For clarity,
      the value and meanings for TransferCharacteristics are adopted
      from Table 3 of [ITU-H.273].

   restrictions:

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             +=======+=======================================+
             | value | label                                 |
             +=======+=======================================+
             | 0     | reserved                              |
             +-------+---------------------------------------+
             | 1     | ITU-R BT.709                          |
             +-------+---------------------------------------+
             | 2     | unspecified                           |
             +-------+---------------------------------------+
             | 3     | reserved2                             |
             +-------+---------------------------------------+
             | 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 18: TransferCharacteristics values

   stream copy: True (Section 8)

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5.1.4.1.28.27.  Primaries Element

   id / type / default:  0x55BB / uinteger / 2
   path:  \Segment\Tracks\TrackEntry\Video\Colour\Primaries
   minOccurs / maxOccurs:  1 / 1
   minver:  4
   definition:  The colour primaries of the video.  For clarity, the
      value and meanings for Primaries are adopted from Table 2 of
      [ITU-H.273].

   restrictions:

            +=======+========================================+
            | value | label                                  |
            +=======+========================================+
            | 0     | reserved                               |
            +-------+----------------------------------------+
            | 1     | ITU-R BT.709                           |
            +-------+----------------------------------------+
            | 2     | unspecified                            |
            +-------+----------------------------------------+
            | 3     | reserved2                              |
            +-------+----------------------------------------+
            | 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 19: Primaries values

   stream copy: True (Section 8)

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5.1.4.1.28.28.  MaxCLL Element

   id / type:  0x55BC / uinteger
   path:  \Segment\Tracks\TrackEntry\Video\Colour\MaxCLL
   maxOccurs:  1
   minver:  4
   definition:  Maximum brightness of a single pixel (Maximum Content
      Light Level) in candelas per square meter (cd/m^2).

   stream copy: True (Section 8)

5.1.4.1.28.29.  MaxFALL Element

   id / type:  0x55BD / uinteger
   path:  \Segment\Tracks\TrackEntry\Video\Colour\MaxFALL
   maxOccurs:  1
   minver:  4
   definition:  Maximum brightness of a single full frame (Maximum
      Frame-Average Light Level) in candelas per square meter (cd/m^2).

   stream copy: True (Section 8)

5.1.4.1.28.30.  MasteringMetadata Element

   id / type:  0x55D0 / master
   path:  \Segment\Tracks\TrackEntry\Video\Colour\MasteringMetadata
   maxOccurs:  1
   minver:  4
   definition:  SMPTE 2086 mastering data.

   stream copy: True (Section 8)

5.1.4.1.28.31.  PrimaryRChromaticityX Element

   id / type:  0x55D1 / float
   range:  0x0p+0-0x1p+0
   path:  \Segment\Tracks\TrackEntry\Video\Colour\MasteringMetadata\Prim
      aryRChromaticityX
   maxOccurs:  1
   minver:  4
   definition:  Red X chromaticity coordinate, as defined by [CIE-1931].

   stream copy: True (Section 8)

5.1.4.1.28.32.  PrimaryRChromaticityY Element

   id / type:  0x55D2 / float
   range:  0x0p+0-0x1p+0

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   path:  \Segment\Tracks\TrackEntry\Video\Colour\MasteringMetadata\Prim
      aryRChromaticityY
   maxOccurs:  1
   minver:  4
   definition:  Red Y chromaticity coordinate, as defined by [CIE-1931].

   stream copy: True (Section 8)

5.1.4.1.28.33.  PrimaryGChromaticityX Element

   id / type:  0x55D3 / float
   range:  0x0p+0-0x1p+0
   path:  \Segment\Tracks\TrackEntry\Video\Colour\MasteringMetadata\Prim
      aryGChromaticityX
   maxOccurs:  1
   minver:  4
   definition:  Green X chromaticity coordinate, as defined by
      [CIE-1931].

   stream copy: True (Section 8)

5.1.4.1.28.34.  PrimaryGChromaticityY Element

   id / type:  0x55D4 / float
   range:  0x0p+0-0x1p+0
   path:  \Segment\Tracks\TrackEntry\Video\Colour\MasteringMetadata\Prim
      aryGChromaticityY
   maxOccurs:  1
   minver:  4
   definition:  Green Y chromaticity coordinate, as defined by
      [CIE-1931].

   stream copy: True (Section 8)

5.1.4.1.28.35.  PrimaryBChromaticityX Element

   id / type:  0x55D5 / float
   range:  0x0p+0-0x1p+0
   path:  \Segment\Tracks\TrackEntry\Video\Colour\MasteringMetadata\Prim
      aryBChromaticityX
   maxOccurs:  1
   minver:  4
   definition:  Blue X chromaticity coordinate, as defined by
      [CIE-1931].

   stream copy: True (Section 8)

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5.1.4.1.28.36.  PrimaryBChromaticityY Element

   id / type:  0x55D6 / float
   range:  0x0p+0-0x1p+0
   path:  \Segment\Tracks\TrackEntry\Video\Colour\MasteringMetadata\Prim
      aryBChromaticityY
   maxOccurs:  1
   minver:  4
   definition:  Blue Y chromaticity coordinate, as defined by
      [CIE-1931].

   stream copy: True (Section 8)

5.1.4.1.28.37.  WhitePointChromaticityX Element

   id / type:  0x55D7 / float
   range:  0x0p+0-0x1p+0
   path:  \Segment\Tracks\TrackEntry\Video\Colour\MasteringMetadata\Whit
      ePointChromaticityX
   maxOccurs:  1
   minver:  4
   definition:  White X chromaticity coordinate, as defined by
      [CIE-1931].

   stream copy: True (Section 8)

5.1.4.1.28.38.  WhitePointChromaticityY Element

   id / type:  0x55D8 / float
   range:  0x0p+0-0x1p+0
   path:  \Segment\Tracks\TrackEntry\Video\Colour\MasteringMetadata\Whit
      ePointChromaticityY
   maxOccurs:  1
   minver:  4
   definition:  White Y chromaticity coordinate, as defined by
      [CIE-1931].

   stream copy: True (Section 8)

5.1.4.1.28.39.  LuminanceMax Element

   id / type:  0x55D9 / float
   range:  >= 0x0p+0
   path:  \Segment\Tracks\TrackEntry\Video\Colour\MasteringMetadata\Lumi
      nanceMax
   maxOccurs:  1
   minver:  4
   definition:  Maximum luminance.  Represented in candelas per square

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      meter (cd/m^2).

   stream copy: True (Section 8)

5.1.4.1.28.40.  LuminanceMin Element

   id / type:  0x55DA / float
   range:  >= 0x0p+0
   path:  \Segment\Tracks\TrackEntry\Video\Colour\MasteringMetadata\Lumi
      nanceMin
   maxOccurs:  1
   minver:  4
   definition:  Minimum luminance.  Represented in candelas per square
      meter (cd/m^2).

   stream copy: True (Section 8)

5.1.4.1.28.41.  Projection Element

   id / type:  0x7670 / master
   path:  \Segment\Tracks\TrackEntry\Video\Projection
   maxOccurs:  1
   minver:  4
   definition:  Describes the video projection details.  Used to render
      spherical, VR videos or flipping videos horizontally/vertically.

   stream copy: True (Section 8)

5.1.4.1.28.42.  ProjectionType Element

   id / type / default:  0x7671 / uinteger / 0
   path:  \Segment\Tracks\TrackEntry\Video\Projection\ProjectionType
   minOccurs / maxOccurs:  1 / 1
   minver:  4
   definition:  Describes the projection used for this video track.

   restrictions:

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

                                 Table 20:
                           ProjectionType values

   stream copy: True (Section 8)

5.1.4.1.28.43.  ProjectionPrivate Element

   id / type:  0x7672 / binary
   path:  \Segment\Tracks\TrackEntry\Video\Projection\ProjectionPrivate
   maxOccurs:  1
   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.

   stream copy: True (Section 8)

5.1.4.1.28.44.  ProjectionPoseYaw Element

   id / type / default:  0x7673 / float / 0x0p+0
   range:  >= -0xB4p+0, <= 0xB4p+0

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   path:  \Segment\Tracks\TrackEntry\Video\Projection\ProjectionPoseYaw
   minOccurs / maxOccurs:  1 / 1
   minver:  4
   definition:  Specifies a yaw rotation to the projection.

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

   Setting ProjectionPoseYaw to 180 or -180 degrees, with the
   ProjectionPoseRoll and ProjectionPosePitch set to 0 degrees flips the
   image horizontally.

   stream copy: True (Section 8)

5.1.4.1.28.45.  ProjectionPosePitch Element

   id / type / default:  0x7674 / float / 0x0p+0
   range:  >= -0x5Ap+0, <= 0x5Ap+0
   path:  \Segment\Tracks\TrackEntry\Video\Projection\ProjectionPosePitc
      h
   minOccurs / maxOccurs:  1 / 1
   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 element MUST be in the -90 to 90 degree
   range, both included.

   stream copy: True (Section 8)

5.1.4.1.28.46.  ProjectionPoseRoll Element

   id / type / default:  0x7675 / float / 0x0p+0
   range:  >= -0xB4p+0, <= 0xB4p+0
   path:  \Segment\Tracks\TrackEntry\Video\Projection\ProjectionPoseRoll
   minOccurs / maxOccurs:  1 / 1
   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 element MUST be in the -180 to 180 degree range, both included.

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   Setting ProjectionPoseRoll to 180 or -180 degrees, the
   ProjectionPoseYaw to 180 or -180 degrees with ProjectionPosePitch set
   to 0 degrees flips the image vertically.

   Setting ProjectionPoseRoll to 180 or -180 degrees, with the
   ProjectionPoseYaw and ProjectionPosePitch set to 0 degrees flips the
   image horizontally and vertically.

   stream copy: True (Section 8)

5.1.4.1.29.  Audio Element

   id / type:  0xE1 / master
   path:  \Segment\Tracks\TrackEntry\Audio
   maxOccurs:  1
   definition:  Audio settings.

5.1.4.1.29.1.  SamplingFrequency Element

   id / type / default:  0xB5 / float / 0x1.f4p+12
   range:  > 0x0p+0
   path:  \Segment\Tracks\TrackEntry\Audio\SamplingFrequency
   minOccurs / maxOccurs:  1 / 1
   definition:  Sampling frequency in Hz.

   stream copy: True (Section 8)

5.1.4.1.29.2.  OutputSamplingFrequency Element

   id / type:  0x78B5 / float
   range:  > 0x0p+0
   path:  \Segment\Tracks\TrackEntry\Audio\OutputSamplingFrequency
   maxOccurs:  1
   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 21: OutputSamplingFrequency implementation notes

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5.1.4.1.29.3.  Channels Element

   id / type / default:  0x9F / uinteger / 1
   range:  not 0
   path:  \Segment\Tracks\TrackEntry\Audio\Channels
   minOccurs / maxOccurs:  1 / 1
   definition:  Numbers of channels in the track.

   stream copy: True (Section 8)

5.1.4.1.29.4.  BitDepth Element

   id / type:  0x6264 / uinteger
   range:  not 0
   path:  \Segment\Tracks\TrackEntry\Audio\BitDepth
   maxOccurs:  1
   definition:  Bits per sample, mostly used for PCM.

   stream copy: True (Section 8)

5.1.4.1.30.  TrackOperation Element

   id / type:  0xE2 / master
   path:  \Segment\Tracks\TrackEntry\TrackOperation
   maxOccurs:  1
   minver:  3
   definition:  Operation that needs to be applied on tracks to create
      this virtual track.  For more details look at Section 18.8.

   stream copy: True (Section 8)

5.1.4.1.30.1.  TrackCombinePlanes Element

   id / type:  0xE3 / master
   path:  \Segment\Tracks\TrackEntry\TrackOperation\TrackCombinePlanes
   maxOccurs:  1
   minver:  3
   definition:  Contains the list of all video plane tracks that need to
      be combined to create this 3D track

   stream copy: True (Section 8)

5.1.4.1.30.2.  TrackPlane Element

   id / type:  0xE4 / master
   path:  \Segment\Tracks\TrackEntry\TrackOperation\TrackCombinePlanes\T
      rackPlane
   minOccurs:  1

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

   stream copy: True (Section 8)

5.1.4.1.30.3.  TrackPlaneUID Element

   id / type:  0xE5 / uinteger
   range:  not 0
   path:  \Segment\Tracks\TrackEntry\TrackOperation\TrackCombinePlanes\T
      rackPlane\TrackPlaneUID
   minOccurs / maxOccurs:  1 / 1
   minver:  3
   definition:  The trackUID number of the track representing the plane.

   stream copy: True (Section 8)

5.1.4.1.30.4.  TrackPlaneType Element

   id / type:  0xE6 / uinteger
   path:  \Segment\Tracks\TrackEntry\TrackOperation\TrackCombinePlanes\T
      rackPlane\TrackPlaneType
   minOccurs / maxOccurs:  1 / 1
   minver:  3
   definition:  The kind of plane this track corresponds to.

   restrictions:

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

                                 Table 22:
                           TrackPlaneType values

   stream copy: True (Section 8)

5.1.4.1.30.5.  TrackJoinBlocks Element

   id / type:  0xE9 / master
   path:  \Segment\Tracks\TrackEntry\TrackOperation\TrackJoinBlocks

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   maxOccurs:  1
   minver:  3
   definition:  Contains the list of all tracks whose Blocks need to be
      combined to create this virtual track

   stream copy: True (Section 8)

5.1.4.1.30.6.  TrackJoinUID Element

   id / type:  0xED / uinteger
   range:  not 0
   path:  \Segment\Tracks\TrackEntry\TrackOperation\TrackJoinBlocks\Trac
      kJoinUID
   minOccurs:  1
   minver:  3
   definition:  The trackUID number of a track whose blocks are used to
      create this virtual track.

   stream copy: True (Section 8)

5.1.4.1.31.  ContentEncodings Element

   id / type:  0x6D80 / master
   path:  \Segment\Tracks\TrackEntry\ContentEncodings
   maxOccurs:  1
   definition:  Settings for several content encoding mechanisms like
      compression or encryption.

   stream copy: True (Section 8)

5.1.4.1.31.1.  ContentEncoding Element

   id / type:  0x6240 / master
   path:  \Segment\Tracks\TrackEntry\ContentEncodings\ContentEncoding
   minOccurs:  1
   definition:  Settings for one content encoding like compression or
      encryption.

   stream copy: True (Section 8)

5.1.4.1.31.2.  ContentEncodingOrder Element

   id / type / default:  0x5031 / uinteger / 0
   path:  \Segment\Tracks\TrackEntry\ContentEncodings\ContentEncoding\Co
      ntentEncodingOrder
   minOccurs / maxOccurs:  1 / 1
   definition:  Tell in which order to apply each ContentEncoding of the

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      ContentEncodings.  The decoder/demuxer MUST start with the
      ContentEncoding with the highest ContentEncodingOrder and work its
      way down to the ContentEncoding with the lowest
      ContentEncodingOrder.  This value MUST be unique over for each
      ContentEncoding found in the ContentEncodings of this TrackEntry.

   stream copy: True (Section 8)

5.1.4.1.31.3.  ContentEncodingScope Element

   id / type / default:  0x5032 / uinteger / 1
   path:  \Segment\Tracks\TrackEntry\ContentEncodings\ContentEncoding\Co
      ntentEncodingScope
   minOccurs / maxOccurs:  1 / 1
   definition:  A bit field that describes which Elements have been
      modified in this way.  Values (big-endian) can be OR'ed.

   defined values:

      +=======+=========+===========================================+
      | value | label   | definition                                |
      +=======+=========+===========================================+
      | 1     | Block   | All frame contents, excluding lacing      |
      |       |         | data.                                     |
      +-------+---------+-------------------------------------------+
      | 2     | Private | The track's CodecPrivate data.            |
      +-------+---------+-------------------------------------------+
      | 4     | Next    | The next ContentEncoding (next            |
      |       |         | ContentEncodingOrder.  Either the data    |
      |       |         | inside ContentCompression and/or          |
      |       |         | ContentEncryption).This value SHOULD NOT  |
      |       |         | be used as it's not supported by players. |
      +-------+---------+-------------------------------------------+

                   Table 23: ContentEncodingScope values

   stream copy: True (Section 8)

5.1.4.1.31.4.  ContentEncodingType Element

   id / type / default:  0x5033 / uinteger / 0
   path:  \Segment\Tracks\TrackEntry\ContentEncodings\ContentEncoding\Co
      ntentEncodingType
   minOccurs / maxOccurs:  1 / 1
   definition:  A value describing what kind of transformation is
      applied.

   restrictions:

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

                                 Table 24:
                            ContentEncodingType
                                   values

   stream copy: True (Section 8)

5.1.4.1.31.5.  ContentCompression Element

   id / type:  0x5034 / master
   path:  \Segment\Tracks\TrackEntry\ContentEncodings\ContentEncoding\Co
      ntentCompression
   maxOccurs:  1
   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.

   stream copy: True (Section 8)

5.1.4.1.31.6.  ContentCompAlgo Element

   id / type / default:  0x4254 / uinteger / 0
   path:  \Segment\Tracks\TrackEntry\ContentEncodings\ContentEncoding\Co
      ntentCompression\ContentCompAlgo
   minOccurs / maxOccurs:  1 / 1
   definition:  The compression algorithm used.

   defined values:

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      +=======+===========+=========================================+
      | value | label     | definition                              |
      +=======+===========+=========================================+
      | 0     | zlib      | zlib compression [RFC1950].             |
      +-------+-----------+-----------------------------------------+
      | 1     | bzlib     | bzip2 compression [BZIP2], SHOULD NOT   |
      |       |           | be used; see usage notes.               |
      +-------+-----------+-----------------------------------------+
      | 2     | lzo1x     | Lempel-Ziv-Oberhumer compression [LZO], |
      |       |           | SHOULD NOT be used; see usage notes.    |
      +-------+-----------+-----------------------------------------+
      | 3     | Header    | Octets in ContentCompSettings           |
      |       | Stripping | (Section 5.1.4.1.31.7) have been        |
      |       |           | stripped from each frame.               |
      +-------+-----------+-----------------------------------------+

                      Table 25: ContentCompAlgo values

   usage notes:  Compression method "1" (bzlib) and "2" (lzo1x) are
      lacking proper documentation on the format which limits
      implementation possibilities.  Due to licensing conflicts on
      commonly available libraries compression methods "2" (lzo1x) does
      not offer widespread interoperability.  A Matroska Writer SHOULD
      NOT use these compression methods by default.  A Matroska Reader
      MAY support methods "1" and "2" as possible, and SHOULD support
      other methods.

   stream copy: True (Section 8)

5.1.4.1.31.7.  ContentCompSettings Element

   id / type:  0x4255 / binary
   path:  \Segment\Tracks\TrackEntry\ContentEncodings\ContentEncoding\Co
      ntentCompression\ContentCompSettings
   maxOccurs:  1
   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.

   stream copy: True (Section 8)

5.1.4.1.31.8.  ContentEncryption Element

   id / type:  0x5035 / master
   path:  \Segment\Tracks\TrackEntry\ContentEncodings\ContentEncoding\Co
      ntentEncryption
   maxOccurs:  1
   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.  A Matroska Player MAY
      support encryption.

   stream copy: True (Section 8)

5.1.4.1.31.9.  ContentEncAlgo Element

   id / type / default:  0x47E1 / uinteger / 0
   path:  \Segment\Tracks\TrackEntry\ContentEncodings\ContentEncoding\Co
      ntentEncryption\ContentEncAlgo
   minOccurs / maxOccurs:  1 / 1
   definition:  The encryption algorithm used.

   defined values:

   +=======+===============+===========================================+
   | value | label         | definition                                |
   +=======+===============+===========================================+
   | 0     | Not           | The data are not encrypted.               |
   |       | encrypted     |                                           |
   +-------+---------------+-------------------------------------------+
   | 1     | DES           | Data Encryption Standard (DES)            |
   |       |               | [FIPS.46-3].This value SHOULD be avoided. |
   +-------+---------------+-------------------------------------------+
   | 2     | 3DES          | Triple Data Encryption Algorithm          |
   |       |               | [SP.800-67].This value SHOULD be avoided. |
   +-------+---------------+-------------------------------------------+
   | 3     | Twofish       | Twofish Encryption Algorithm [Twofish].   |
   +-------+---------------+-------------------------------------------+
   | 4     | Blowfish      | Blowfish Encryption Algorithm             |
   |       |               | [Blowfish].This value SHOULD be avoided.  |
   +-------+---------------+-------------------------------------------+
   | 5     | AES           | Advanced Encryption Standard (AES)        |
   |       |               | [FIPS.197].                               |
   +-------+---------------+-------------------------------------------+

                      Table 26: ContentEncAlgo values

   stream copy: True (Section 8)

5.1.4.1.31.10.  ContentEncKeyID Element

   id / type:  0x47E2 / binary
   path:  \Segment\Tracks\TrackEntry\ContentEncodings\ContentEncoding\Co
      ntentEncryption\ContentEncKeyID
   maxOccurs:  1
   definition:  For public key algorithms this is the ID of the public

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      key the data was encrypted with.

   stream copy: True (Section 8)

5.1.4.1.31.11.  ContentEncAESSettings Element

   id / type:  0x47E7 / master
   path:  \Segment\Tracks\TrackEntry\ContentEncodings\ContentEncoding\Co
      ntentEncryption\ContentEncAESSettings
   maxOccurs:  1
   minver:  4
   definition:  Settings describing the encryption algorithm used.

   notes:

      +===========+=================================================+
      | attribute | note                                            |
      +===========+=================================================+
      | maxOccurs | ContentEncAESSettings MUST NOT be set           |
      |           | (maxOccurs=0) if ContentEncAlgo is not AES (5). |
      +-----------+-------------------------------------------------+

            Table 27: ContentEncAESSettings implementation notes

   stream copy: True (Section 8)

5.1.4.1.31.12.  AESSettingsCipherMode Element

   id / type:  0x47E8 / uinteger
   path:  \Segment\Tracks\TrackEntry\ContentEncodings\ContentEncoding\Co
      ntentEncryption\ContentEncAESSettings\AESSettingsCipherMode
   minOccurs / maxOccurs:  1 / 1
   minver:  4
   definition:  The AES cipher mode used in the encryption.

   defined values:

         +=======+=========+=====================================+
         | value | label   | definition                          |
         +=======+=========+=====================================+
         | 1     | AES-CTR | Counter [SP.800-38A].               |
         +-------+---------+-------------------------------------+
         | 2     | AES-CBC | Cipher Block Chaining [SP.800-38A]. |
         +-------+---------+-------------------------------------+

                   Table 28: AESSettingsCipherMode values

   notes:

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      +===========+=================================================+
      | attribute | note                                            |
      +===========+=================================================+
      | maxOccurs | AESSettingsCipherMode MUST NOT be set           |
      |           | (maxOccurs=0) if ContentEncAlgo is not AES (5). |
      +-----------+-------------------------------------------------+

            Table 29: AESSettingsCipherMode implementation notes

   stream copy: True (Section 8)

5.1.5.  Cues Element

   id / type:  0x1C53BB6B / master
   path:  \Segment\Cues
   minOccurs / maxOccurs:  see implementation notes / 1
   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 Section 23.2.    |
    +-----------+----------------------------------------------------+

                   Table 30: Cues implementation notes

5.1.5.1.  CuePoint Element

   id / type:  0xBB / master
   path:  \Segment\Cues\CuePoint
   minOccurs:  1
   definition:  Contains all information relative to a seek point in the
      Segment.

5.1.5.1.1.  CueTime Element

   id / type:  0xB3 / uinteger
   path:  \Segment\Cues\CuePoint\CueTime
   minOccurs / maxOccurs:  1 / 1
   definition:  Absolute timestamp of the seek point, expressed in
      Matroska Ticks -- i.e., in nanoseconds; see Section 11.1.

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5.1.5.1.2.  CueTrackPositions Element

   id / type:  0xB7 / master
   path:  \Segment\Cues\CuePoint\CueTrackPositions
   minOccurs:  1
   definition:  Contain positions for different tracks corresponding to
      the timestamp.

5.1.5.1.2.1.  CueTrack Element

   id / type:  0xF7 / uinteger
   range:  not 0
   path:  \Segment\Cues\CuePoint\CueTrackPositions\CueTrack
   minOccurs / maxOccurs:  1 / 1
   definition:  The track for which a position is given.

5.1.5.1.2.2.  CueClusterPosition Element

   id / type:  0xF1 / uinteger
   path:  \Segment\Cues\CuePoint\CueTrackPositions\CueClusterPosition
   minOccurs / maxOccurs:  1 / 1
   definition:  The Segment Position (Section 16) of the Cluster
      containing the associated Block.

5.1.5.1.2.3.  CueRelativePosition Element

   id / type:  0xF0 / uinteger
   path:  \Segment\Cues\CuePoint\CueTrackPositions\CueRelativePosition
   maxOccurs:  1
   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.

5.1.5.1.2.4.  CueDuration Element

   id / type:  0xB2 / uinteger
   path:  \Segment\Cues\CuePoint\CueTrackPositions\CueDuration
   maxOccurs:  1
   minver:  4
   definition:  The duration of the block, expressed in Segment Ticks
      which is based on TimestampScale; see Section 11.1.  If missing,
      the track's DefaultDuration does not apply and no duration
      information is available in terms of the cues.

5.1.5.1.2.5.  CueBlockNumber Element

   id / type:  0x5378 / uinteger

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   range:  not 0
   path:  \Segment\Cues\CuePoint\CueTrackPositions\CueBlockNumber
   maxOccurs:  1
   definition:  Number of the Block in the specified Cluster.

5.1.5.1.2.6.  CueCodecState Element

   id / type / default:  0xEA / uinteger / 0
   path:  \Segment\Cues\CuePoint\CueTrackPositions\CueCodecState
   minOccurs / maxOccurs:  1 / 1
   minver:  2
   definition:  The Segment Position (Section 16) of the Codec State
      corresponding to this Cue Element. 0 means that the data is taken
      from the initial Track Entry.

5.1.5.1.2.7.  CueReference Element

   id / type:  0xDB / master
   path:  \Segment\Cues\CuePoint\CueTrackPositions\CueReference
   minver:  2
   definition:  The Clusters containing the referenced Blocks.

5.1.5.1.2.8.  CueRefTime Element

   id / type:  0x96 / uinteger
   path:  \Segment\Cues\CuePoint\CueTrackPositions\CueReference\CueRefTi
      me
   minOccurs / maxOccurs:  1 / 1
   minver:  2
   definition:  Timestamp of the referenced Block, expressed in Matroska
      Ticks -- i.e., in nanoseconds; see Section 11.1.

5.1.6.  Attachments Element

   id / type:  0x1941A469 / master
   path:  \Segment\Attachments
   maxOccurs:  1
   definition:  Contain attached files.

5.1.6.1.  AttachedFile Element

   id / type:  0x61A7 / master
   path:  \Segment\Attachments\AttachedFile
   minOccurs:  1
   definition:  An attached file.

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5.1.6.1.1.  FileDescription Element

   id / type:  0x467E / utf-8
   path:  \Segment\Attachments\AttachedFile\FileDescription
   maxOccurs:  1
   definition:  A human-friendly name for the attached file.

5.1.6.1.2.  FileName Element

   id / type:  0x466E / utf-8
   path:  \Segment\Attachments\AttachedFile\FileName
   minOccurs / maxOccurs:  1 / 1
   definition:  Filename of the attached file.

5.1.6.1.3.  FileMediaType Element

   id / type:  0x4660 / string
   path:  \Segment\Attachments\AttachedFile\FileMediaType
   minOccurs / maxOccurs:  1 / 1
   definition:  Media type of the file following the [RFC6838] format.

   stream copy: True (Section 8)

5.1.6.1.4.  FileData Element

   id / type:  0x465C / binary
   path:  \Segment\Attachments\AttachedFile\FileData
   minOccurs / maxOccurs:  1 / 1
   definition:  The data of the file.

   stream copy: True (Section 8)

5.1.6.1.5.  FileUID Element

   id / type:  0x46AE / uinteger
   range:  not 0
   path:  \Segment\Attachments\AttachedFile\FileUID
   minOccurs / maxOccurs:  1 / 1
   definition:  Unique ID representing the file, as random as possible.

   stream copy: True (Section 8)

5.1.7.  Chapters Element

   id / type:  0x1043A770 / master
   path:  \Segment\Chapters
   maxOccurs:  1

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   recurring: True

   definition:  A system to define basic menus and partition data.  For
      more detailed information, look at the Chapters explanation in
      Section 20.

5.1.7.1.  EditionEntry Element

   id / type:  0x45B9 / master
   path:  \Segment\Chapters\EditionEntry
   minOccurs:  1
   definition:  Contains all information about a Segment edition.

5.1.7.1.1.  EditionUID Element

   id / type:  0x45BC / uinteger
   range:  not 0
   path:  \Segment\Chapters\EditionEntry\EditionUID
   maxOccurs:  1
   definition:  A unique ID to identify the edition.  It's useful for
      tagging an edition.

   stream copy: True (Section 8)

5.1.7.1.2.  EditionFlagDefault Element

   id / type / default:  0x45DB / uinteger / 0
   range:  0-1
   path:  \Segment\Chapters\EditionEntry\EditionFlagDefault
   minOccurs / maxOccurs:  1 / 1
   definition:  Set to 1 if the edition SHOULD be used as the default
      one.

5.1.7.1.3.  EditionFlagOrdered Element

   id / type / default:  0x45DD / uinteger / 0
   range:  0-1
   path:  \Segment\Chapters\EditionEntry\EditionFlagOrdered
   minOccurs / maxOccurs:  1 / 1
   definition:  Set to 1 if the chapters can be defined multiple times
      and the order to play them is enforced; see Section 20.1.3.

5.1.7.1.4.  ChapterAtom Element

   id / type:  0xB6 / master
   path:  \Segment\Chapters\EditionEntry\+ChapterAtom
   minOccurs:  1

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   recursive: True

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

5.1.7.1.4.1.  ChapterUID Element

   id / type:  0x73C4 / uinteger
   range:  not 0
   path:  \Segment\Chapters\EditionEntry\+ChapterAtom\ChapterUID
   minOccurs / maxOccurs:  1 / 1
   definition:  A unique ID to identify the Chapter.

   stream copy: True (Section 8)

5.1.7.1.4.2.  ChapterStringUID Element

   id / type:  0x5654 / utf-8
   path:  \Segment\Chapters\EditionEntry\+ChapterAtom\ChapterStringUID
   maxOccurs:  1
   minver:  3
   definition:  A unique string ID to identify the Chapter.  For example
      it is used as the storage for [WebVTT] cue identifier values.

5.1.7.1.4.3.  ChapterTimeStart Element

   id / type:  0x91 / uinteger
   path:  \Segment\Chapters\EditionEntry\+ChapterAtom\ChapterTimeStart
   minOccurs / maxOccurs:  1 / 1
   definition:  Timestamp of the start of Chapter, expressed in Matroska
      Ticks -- i.e., in nanoseconds; see Section 11.1.

5.1.7.1.4.4.  ChapterTimeEnd Element

   id / type:  0x92 / uinteger
   path:  \Segment\Chapters\EditionEntry\+ChapterAtom\ChapterTimeEnd
   minOccurs / maxOccurs:  see implementation notes / 1
   definition:  Timestamp of the end of Chapter timestamp excluded,
      expressed in Matroska Ticks -- i.e., in nanoseconds; see
      Section 11.1.  The value MUST be greater than or equal to the
      ChapterTimeStart of the same ChapterAtom.
   usage notes:  The ChapterTimeEnd timestamp value being excluded, it
      MUST take in account the duration of the last frame it includes,
      especially for the ChapterAtom using the last frames of the
      Segment.

   notes:

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    +===========+====================================================+
    | attribute | note                                               |
    +===========+====================================================+
    | minOccurs | ChapterTimeEnd MUST be set (minOccurs=1) if the    |
    |           | Edition is an ordered edition; see Section 20.1.3, |
    |           | unless it's a Parent Chapter; see Section 20.2.3   |
    +-----------+----------------------------------------------------+

              Table 31: ChapterTimeEnd implementation notes

5.1.7.1.4.5.  ChapterFlagHidden Element

   id / type / default:  0x98 / uinteger / 0
   range:  0-1
   path:  \Segment\Chapters\EditionEntry\+ChapterAtom\ChapterFlagHidden
   minOccurs / maxOccurs:  1 / 1
   definition:  Set to 1 if a chapter is hidden.  Hidden chapters SHOULD
      NOT be available to the user interface (but still to Control
      Tracks; see Section 20.2.5 on Chapter flags).

5.1.7.1.4.6.  ChapterSegmentUUID Element

   id / type:  0x6E67 / binary
   length:  16
   path:  \Segment\Chapters\EditionEntry\+ChapterAtom\ChapterSegmentUUID
   minOccurs / maxOccurs:  see implementation notes / 1
   definition:  The SegmentUUID of another Segment to play during this
      chapter.
   usage notes:  The value MUST NOT be the SegmentUUID value of the
      Segment it belongs to.

   notes:

       +===========+==============================================+
       | attribute | note                                         |
       +===========+==============================================+
       | minOccurs | ChapterSegmentUUID MUST be set (minOccurs=1) |
       |           | if ChapterSegmentEditionUID is used; see     |
       |           | Section 17.2 on medium-linking Segments.     |
       +-----------+----------------------------------------------+

            Table 32: ChapterSegmentUUID implementation notes

5.1.7.1.4.7.  ChapterSegmentEditionUID Element

   id / type:  0x6EBC / uinteger
   range:  not 0
   path:  \Segment\Chapters\EditionEntry\+ChapterAtom\ChapterSegmentEdit

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      ionUID
   maxOccurs:  1
   definition:  The EditionUID to play from the Segment linked in
      ChapterSegmentUUID.  If ChapterSegmentEditionUID is undeclared,
      then no Edition of the linked Segment is used; see Section 17.2 on
      medium-linking Segments.

5.1.7.1.4.8.  ChapterPhysicalEquiv Element

   id / type:  0x63C3 / uinteger
   path:  \Segment\Chapters\EditionEntry\+ChapterAtom\ChapterPhysicalEqu
      iv
   maxOccurs:  1
   definition:  Specify the physical equivalent of this ChapterAtom like
      "DVD" (60) or "SIDE" (50); see Section 20.4 for a complete list of
      values.

5.1.7.1.4.9.  ChapterDisplay Element

   id / type:  0x80 / master
   path:  \Segment\Chapters\EditionEntry\+ChapterAtom\ChapterDisplay
   definition:  Contains all possible strings to use for the chapter
      display.

5.1.7.1.4.10.  ChapString Element

   id / type:  0x85 / utf-8
   path:  \Segment\Chapters\EditionEntry\+ChapterAtom\ChapterDisplay\Cha
      pString
   minOccurs / maxOccurs:  1 / 1
   definition:  Contains the string to use as the chapter atom.

5.1.7.1.4.11.  ChapLanguage Element

   id / type / default:  0x437C / string / eng
   path:  \Segment\Chapters\EditionEntry\+ChapterAtom\ChapterDisplay\Cha
      pLanguage
   minOccurs:  1
   definition:  A language corresponding to the string, in the Matroska
      languages form; see Section 12 on language codes.  This Element
      MUST be ignored if a ChapLanguageBCP47 Element is used within the
      same ChapterDisplay Element.

5.1.7.1.4.12.  ChapLanguageBCP47 Element

   id / type:  0x437D / string
   path:  \Segment\Chapters\EditionEntry\+ChapterAtom\ChapterDisplay\Cha
      pLanguageBCP47

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   minver:  4
   definition:  A language corresponding to the ChapString, in the
      [BCP47] form; see Section 12 on language codes.  If a
      ChapLanguageBCP47 Element is used, then any ChapLanguage and
      ChapCountry Elements used in the same ChapterDisplay MUST be
      ignored.

5.1.7.1.4.13.  ChapCountry Element

   id / type:  0x437E / string
   path:  \Segment\Chapters\EditionEntry\+ChapterAtom\ChapterDisplay\Cha
      pCountry
   definition:  A country corresponding to the string, in the Matroska
      countries form; see Section 13 on country codes.  This Element
      MUST be ignored if a ChapLanguageBCP47 Element is used within the
      same ChapterDisplay Element.

5.1.7.1.4.14.  ChapProcess Element

   id / type:  0x6944 / master
   path:  \Segment\Chapters\EditionEntry\+ChapterAtom\ChapProcess
   definition:  Contains all the commands associated to the Atom.

5.1.7.1.4.15.  ChapProcessCodecID Element

   id / type / default:  0x6955 / uinteger / 0
   path:  \Segment\Chapters\EditionEntry\+ChapterAtom\ChapProcess\ChapPr
      ocessCodecID
   minOccurs / maxOccurs:  1 / 1
   definition:  Contains the type of the codec used for the processing.
      A value of 0 means built-in Matroska processing (to be defined), a
      value of 1 means the DVD command set is used; see Section 20.3 on
      DVD menus.  More codec IDs can be added later.

5.1.7.1.4.16.  ChapProcessPrivate Element

   id / type:  0x450D / binary
   path:  \Segment\Chapters\EditionEntry\+ChapterAtom\ChapProcess\ChapPr
      ocessPrivate
   maxOccurs:  1
   definition:  Some optional data attached to the ChapProcessCodecID
      information.  For ChapProcessCodecID = 1, it is the "DVD level"
      equivalent; see Section 20.3 on DVD menus.

5.1.7.1.4.17.  ChapProcessCommand Element

   id / type:  0x6911 / master
   path:  \Segment\Chapters\EditionEntry\+ChapterAtom\ChapProcess\ChapPr

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      ocessCommand
   definition:  Contains all the commands associated to the Atom.

5.1.7.1.4.18.  ChapProcessTime Element

   id / type:  0x6922 / uinteger
   path:  \Segment\Chapters\EditionEntry\+ChapterAtom\ChapProcess\ChapPr
      ocessCommand\ChapProcessTime
   minOccurs / maxOccurs:  1 / 1
   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 33: ChapProcessTime values

5.1.7.1.4.19.  ChapProcessData Element

   id / type:  0x6933 / binary
   path:  \Segment\Chapters\EditionEntry\+ChapterAtom\ChapProcess\ChapPr
      ocessCommand\ChapProcessData
   minOccurs / maxOccurs:  1 / 1
   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 20.3 on DVD menus.

5.1.8.  Tags Element

   id / type:  0x1254C367 / master
   path:  \Segment\Tags
   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].

5.1.8.1.  Tag Element

   id / type:  0x7373 / master
   path:  \Segment\Tags\Tag

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   minOccurs:  1
   definition:  A single metadata descriptor.

5.1.8.1.1.  Targets Element

   id / type:  0x63C0 / master
   path:  \Segment\Tags\Tag\Targets
   minOccurs / maxOccurs:  1 / 1
   definition:  Specifies which other elements the metadata represented
      by the Tag applies to.  If empty or omitted, then the Tag
      describes everything in the Segment.

5.1.8.1.1.1.  TargetTypeValue Element

   id / type / default:  0x68CA / uinteger / 50
   path:  \Segment\Tags\Tag\Targets\TargetTypeValue
   minOccurs / maxOccurs:  1 / 1
   definition:  A number to indicate the logical level of the target.

   defined values:

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      +=======+===================+=================================+
      | 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           | 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 or |
      |       | CHAPTER           | movie.                          |
      +-------+-------------------+---------------------------------+
      | 20    | SUBTRACK /        | Corresponds to parts of a track |
      |       | MOVEMENT / SCENE  | for audio like a movement, or a |
      |       |                   | scene in a movie.               |
      +-------+-------------------+---------------------------------+
      | 10    | SHOT              | The lowest hierarchy found in   |
      |       |                   | music or movies.                |
      +-------+-------------------+---------------------------------+

                      Table 34: TargetTypeValue values

5.1.8.1.1.2.  TargetType Element

   id / type:  0x63CA / string
   path:  \Segment\Tags\Tag\Targets\TargetType
   maxOccurs:  1
   definition:  An informational string that can be used to display the
      logical level of the target like "ALBUM", "TRACK", "MOVIE",
      "CHAPTER", etc.

   restrictions:

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                    +============+====================+
                    | value      | label              |
                    +============+====================+
                    | COLLECTION | TargetTypeValue 70 |
                    +------------+--------------------+
                    | EDITION    | TargetTypeValue 60 |
                    +------------+--------------------+
                    | ISSUE      | TargetTypeValue 60 |
                    +------------+--------------------+
                    | VOLUME     | TargetTypeValue 60 |
                    +------------+--------------------+
                    | OPUS       | TargetTypeValue 60 |
                    +------------+--------------------+
                    | SEASON     | TargetTypeValue 60 |
                    +------------+--------------------+
                    | SEQUEL     | TargetTypeValue 60 |
                    +------------+--------------------+
                    | ALBUM      | TargetTypeValue 50 |
                    +------------+--------------------+
                    | OPERA      | TargetTypeValue 50 |
                    +------------+--------------------+
                    | CONCERT    | TargetTypeValue 50 |
                    +------------+--------------------+
                    | MOVIE      | TargetTypeValue 50 |
                    +------------+--------------------+
                    | EPISODE    | TargetTypeValue 50 |
                    +------------+--------------------+
                    | PART       | TargetTypeValue 40 |
                    +------------+--------------------+
                    | SESSION    | TargetTypeValue 40 |
                    +------------+--------------------+
                    | TRACK      | TargetTypeValue 30 |
                    +------------+--------------------+
                    | SONG       | TargetTypeValue 30 |
                    +------------+--------------------+
                    | CHAPTER    | TargetTypeValue 30 |
                    +------------+--------------------+
                    | SUBTRACK   | TargetTypeValue 20 |
                    +------------+--------------------+
                    | MOVEMENT   | TargetTypeValue 20 |
                    +------------+--------------------+
                    | SCENE      | TargetTypeValue 20 |
                    +------------+--------------------+
                    | SHOT       | TargetTypeValue 10 |
                    +------------+--------------------+

                        Table 35: TargetType values

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5.1.8.1.1.3.  TagTrackUID Element

   id / type / default:  0x63C5 / uinteger / 0
   path:  \Segment\Tags\Tag\Targets\TagTrackUID
   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.

5.1.8.1.1.4.  TagEditionUID Element

   id / type / default:  0x63C9 / uinteger / 0
   path:  \Segment\Tags\Tag\Targets\TagEditionUID
   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
      editions in the Segment.  If set to any other value, it MUST match
      the EditionUID value of an edition found in this Segment.

5.1.8.1.1.5.  TagChapterUID Element

   id / type / default:  0x63C4 / uinteger / 0
   path:  \Segment\Tags\Tag\Targets\TagChapterUID
   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.

5.1.8.1.1.6.  TagAttachmentUID Element

   id / type / default:  0x63C6 / uinteger / 0
   path:  \Segment\Tags\Tag\Targets\TagAttachmentUID
   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.

5.1.8.1.2.  SimpleTag Element

   id / type:  0x67C8 / master
   path:  \Segment\Tags\Tag\+SimpleTag
   minOccurs:  1

   recursive: True

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   definition:  Contains general information about the target.

5.1.8.1.2.1.  TagName Element

   id / type:  0x45A3 / utf-8
   path:  \Segment\Tags\Tag\+SimpleTag\TagName
   minOccurs / maxOccurs:  1 / 1
   definition:  The name of the Tag that is going to be stored.

5.1.8.1.2.2.  TagLanguage Element

   id / type / default:  0x447A / string / und
   path:  \Segment\Tags\Tag\+SimpleTag\TagLanguage
   minOccurs / maxOccurs:  1 / 1
   definition:  Specifies the language of the tag specified, in the
      Matroska languages form; see Section 12 on language codes.  This
      Element MUST be ignored if the TagLanguageBCP47 Element is used
      within the same SimpleTag Element.

5.1.8.1.2.3.  TagLanguageBCP47 Element

   id / type:  0x447B / string
   path:  \Segment\Tags\Tag\+SimpleTag\TagLanguageBCP47
   maxOccurs:  1
   minver:  4
   definition:  The language used in the TagString, in the [BCP47] form;
      see Section 12 on language codes.  If this Element is used, then
      any TagLanguage Elements used in the same SimpleTag MUST be
      ignored.

5.1.8.1.2.4.  TagDefault Element

   id / type / default:  0x4484 / uinteger / 1
   range:  0-1
   path:  \Segment\Tags\Tag\+SimpleTag\TagDefault
   minOccurs / maxOccurs:  1 / 1
   definition:  A boolean value to indicate if this is the default/
      original language to use for the given tag.

5.1.8.1.2.5.  TagString Element

   id / type:  0x4487 / utf-8
   path:  \Segment\Tags\Tag\+SimpleTag\TagString
   maxOccurs:  1
   definition:  The value of the Tag.

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5.1.8.1.2.6.  TagBinary Element

   id / type:  0x4485 / binary
   path:  \Segment\Tags\Tag\+SimpleTag\TagBinary
   maxOccurs:  1
   definition:  The values of the Tag, if it is binary.  Note that this
      cannot be used in the same SimpleTag as TagString.

6.  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.  This 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.

6.1.  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.

   All Top-Level Elements MUST use a 4-octet long EBML Element ID.

   When using Medium Linking, chapters are used to reference other
   Segments to play in a given order Section 17.2.  A Segment containing
   these linked Chapters does not require a Track Element or a Cluster
   Element.

   It is possible to edit a Matroska file after it has been created.
   For example, chapters, tags, or attachments can be added.  When new
   Top-Level Elements are added to a Matroska file, the SeekHead
   Element(s) MUST be updated so that the SeekHead Element(s) itemize
   the identity and position of all Top-Level Elements.

   Editing, removing, or adding Elements to a Matroska file often
   requires that some existing Elements be voided or extended.
   Transforming the existing Elements into Void Elements as padding can
   be used as a method to avoid moving large amounts of data around.

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6.2.  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.

   In Matroska all Top-Level Elements of an EBML Document SHOULD include
   a CRC-32 Element as their first Child Element.  The Segment Element,
   which is the Root Element, SHOULD NOT have a CRC-32 Element.

6.3.  SeekHead

   If used, the first SeekHead Element MUST 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.

6.4.  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.

6.5.  Info

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

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6.6.  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.

6.7.  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.

6.8.  Tags

   The Tags Element is most subject to changes after the file was
   originally created.  For easier editing, the Tags Element can 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 and Segment sizes will only
   marginally change.

7.  Matroska versioning

   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).

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   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 (Section 5.1.3.4) MUST
   have a DocTypeVersion equal to or greater than 2.  A file containing
   CueRelativePosition Elements (Section 5.1.5.1.2.3) 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.

   A reading application supporting Matroska version V MUST NOT refuse
   to read a file with DocReadTypeVersion equal to or lower than V even
   if DocTypeVersion is greater than V.

   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.

8.  Stream Copy

   It is sometimes necessary to create a Matroska file from another
   Matroska file, for example to add subtitles in a language or to edit
   out a portion of the content.  Some values from the original Matroska
   file need to be kept the same in the destination file.  For example,
   the SamplingFrequency of an audio track wouldn't change between the
   two files.  Some other values may change between the two files, for
   example the TrackNumber of an audio track when another track has been
   added.

   An Element is marked with a property: stream copy: True when the
   values of that Element need to be kept identical between the source
   and destination file.  If that property is not set, elements may or
   may not keep the same value between the source and destination.

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9.  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 Section 5.1.4.1.28.1,
   then DefaultDecodedFieldDuration equals the period between two
   successive fields at the output of the decoding process.  For video
   sequences signaled as progressive, DefaultDecodedFieldDuration is
   half of the period between two successive frames at the output of the
   decoding process.

   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: 1000000000 ns/(48/1.001) = 20854167 ns
   *  PAL broadcast/DVD: 1000000000 ns/(50/1.000) = 20000000 ns
   *  N/ATSC broadcast: 1000000000 ns/(60/1.001) = 16683333 ns
   *  hard-telecined DVD: 1000000000 ns/(60/1.001) = 16683333 ns (60
      encoded interlaced fields per second)
   *  soft-telecined DVD: 1000000000 ns/(60/1.001) = 16683333 ns (48
      encoded interlaced fields per second, with "repeat_first_field =
      1")

10.  Cluster Blocks

   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.

   Matroska has two similar ways to store frames in a block:

   *  in a Block which is contained inside a BlockGroup,
   *  or in a SimpleBlock which is directly in the Cluster.

   The SimpleBlock is usually preferred unless some extra elements of
   the BlockGroup need to be used.  A Matroska Reader MUST support both
   types of blocks.

   Each block contains the same parts in the following order:

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   *  a variable length header,
   *  optionally the lacing information,
   *  the consecutive frame(s)

   The block header starts with the number of the Track it corresponds
   to.  The value MUST corresponding to the TrackNumber
   (Section 5.1.4.1.1) of a TrackEntry of the Segment.

   The TrackNumber is coded using the VINT mechanism described in
   Section 4 of [RFC8794].  To save space, the shortest VINT form SHOULD
   be used.  The value can be coded on up to 8 octets.  This is the only
   element with a variable size in the block header.

   The timestamp is expressed in Track Ticks; see Section 11.1.  The
   value is stored as a signed value on 16 bits.

10.1.  Block Structure

   This section describes the binary data contained in the Block Element
   Section 5.1.3.5.1.  Bit 0 is the most significant bit.

   As the TrackNumber size can vary between 1 and 8 octets, there are 8
   different sizes for the Block header.  We only provide the
   definitions for TrackNumber sizes of 1 and 2.  The other variants can
   be deduced by extending the size of the TrackNumber by multiples of 8
   bits.

     0                   1                   2                   3
     0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |               |                               |       |I|LAC|U|
    |  Track Number |         Timestamp             | Rsvrd |N|ING|N|
    |               |                               |       |V|   |U|
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

              Figure 11: Block Header with 1 octet TrackNumber

     0                   1                   2                   3
     0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |          Track Number         |         Timestamp             |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |       |I|LAC|U|
    | Rsvrd |N|ING|N|                     ...
    |       |V|   |U|
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

             Figure 12: Block Header with 2 octets TrackNumber

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   where:

   Track Number: 8, 16, 24, 32, 40, 48 or 64 bits
      an EBML VINT coded track number

   Timestamp: 16 bits
      signed timestamp in Track Ticks

   Rsvrd: 4 bits
      Reserved bits MUST be set to 0

   INV: 1 bit
      Invisible, the codec SHOULD decode this frame but not display it

   LACING: 2 bits
      using lacing mode

      *  00b : no lacing (Section 10.3.1)
      *  01b : Xiph lacing (Section 10.3.2)
      *  11b : EBML lacing (Section 10.3.3)
      *  10b : fixed-size lacing (Section 10.3.4)

   UNU: 1 bit
      unused bit

   The following data in the Block correspond to the lacing data and
   frames usage as described in each respective lacing mode.

10.2.  SimpleBlock Structure

   This section describes the binary data contained in the SimpleBlock
   Element Section 5.1.3.4.  Bit 0 is the most significant bit.

   The SimpleBlock is inspired by the Block structure; see Section 10.1.
   The main differences are the added Keyframe flag and Discardable
   flag.  Otherwise, everything is the same.

   As the TrackNumber size can vary between 1 and 8 octets, there are 8
   different sizes for the SimpleBlock header.  We only provide the
   definitions for TrackNumber sizes of 1 and 2.  The other variants can
   be deduced by extending the size of the TrackNumber by multiples of 8
   bits.

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     0                   1                   2                   3
     0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |               |                               |K|     |I|LAC|D|
    |  Track Number |         Timestamp             |E|Rsvrd|N|ING|I|
    |               |                               |Y|     |V|   |S|
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

           Figure 13: SimpleBlock Header with 1 octet TrackNumber

     0                   1                   2                   3
     0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |          Track Number         |         Timestamp             |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |K|     |I|LAC|D|
    |E|Rsvrd|N|ING|I|                     ...
    |Y|     |V|   |S|
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

          Figure 14: SimpleBlock Header with 2 octets TrackNumber

   where:

   Track Number: 8, 16, 24, 32, 40, 48 or 64 bits
      an EBML VINT coded track number

   Timestamp: 16 bits
      signed timestamp in Track Ticks

   KEY: 1 bit
      Keyframe, set when the Block contains only keyframes

   Rsvrd: 3 bits
      Reserved bits MUST be set to 0

   INV: 1 bit
      Invisible, the codec SHOULD decode this frame but not display it

   LACING: 2 bits
      using lacing mode

      *  00b : no lacing (Section 10.3.1)
      *  01b : Xiph lacing (Section 10.3.2)
      *  11b : EBML lacing (Section 10.3.3)
      *  10b : fixed-size lacing (Section 10.3.4)

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   DIS: 1 bit
      Discardable, the frames of the Block can be discarded during
      playing if needed

   The following data in the SimpleBlock correspond to the lacing data
   and frames usage as described in each respective lacing mode.

10.3.  Block 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).  It packs multiple frames into a single Block or
   SimpleBlock.

   Lacing MUST NOT be used to store a single frame in a Block or
   SimpleBlock.

   There are 3 types of lacing:

   1.  Xiph, inspired by what is found in the Ogg container [RFC3533]
   2.  EBML, which is the same with sizes coded differently
   3.  fixed-size, where the size is not coded

   When lacing is not used, i.e. to store a single frame, the lacing
   bits 5 and 6 of the Block or SimpleBlock MUST be set to zero.

   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.

   It is possible not to use lacing at all and just store a single frame
   without any extra data.  When the FlagLacing -- Section 5.1.4.1.12 --
   is set to "0" all blocks of that track MUST NOT use lacing.

10.3.1.  No lacing

   When no lacing is used, the number of frames in the lace is ommitted
   and only one frame can be stored in the Block.  The bits 5-6 of the
   Block Header flags are set to 00.

   The Block for an 800 octets frame is as follows:

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              +==============+=========+===================+
              | Block Octets | Value   | Description       |
              +==============+=========+===================+
              | 4-803        | <frame> | Single frame data |
              +--------------+---------+-------------------+

                           Table 36: No lacing

   When a Block contains a single frame, it MUST use this No lacing
   mode.

10.3.2.  Xiph lacing

   The Xiph lacing uses the same coding of size as found in the Ogg
   container [RFC3533].  The bits 5-6 of the Block Header flags are set
   to 01.

   The Block data with laced frames is stored as follows:

   *  Lacing Head on 1 Octet: Number of frames in the lace minus 1.
   *  Lacing size of each frame except the last one.
   *  Binary data of each frame consecutively.

   The lacing size is split into 255 values, stored as unsigned octets
   -- for example, 500 is coded 255;245 or [0xFF 0xF5].  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 or [0xFF 0xFF 0xFF 0x00].

   The size of the last frame is deduced from the size remaining in the
   Block after the other frames.

   Because large sizes result in large coding of the sizes, it is
   RECOMMENDED to use Xiph lacing only with small frames.

   In our example, the 800, 500 and 1000 frames are stored with Xiph
   lacing in a Block as follows:

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     +=============+=====================+==========================+
     | Block Octet | Value               | Description              |
     +=============+=====================+==========================+
     | 4           | 0x02                | Number of frames minus 1 |
     +-------------+---------------------+--------------------------+
     | 5-8         | 0xFF 0xFF 0xFF 0x23 | Size of the first frame  |
     |             |                     | (255;255;255;35)         |
     +-------------+---------------------+--------------------------+
     | 9-10        | 0xFF 0xF5           | Size of the second frame |
     |             |                     | (255;245)                |
     +-------------+---------------------+--------------------------+
     | 11-810      |                     | First frame data         |
     +-------------+---------------------+--------------------------+
     | 811-1310    |                     | Second frame data        |
     +-------------+---------------------+--------------------------+
     | 1311-2310   |                     | Third frame data         |
     +-------------+---------------------+--------------------------+

                      Table 37: Xiph lacing example

   The Block is 2311 octets large and the last frame starts at 1311, so
   we can deduce the size of the last frame is 2311 - 1311 = 1000.

10.3.3.  EBML lacing

   The EBML lacing encodes the frame size with an EBML-like encoding
   [RFC8794].  The bits 5-6 of the Block Header flags are set to 11.

   The Block data with laced frames is stored as follows:

   *  Lacing Head on 1 Octet: Number of frames in the lace minus 1.
   *  Lacing size of each frame except the last one.
   *  Binary data of each frame consecutively.

   The first frame size is encoded as an EBML Variable-Size Integer
   value, also known as VINT in [RFC8794].  The remaining frame sizes
   are encoded as signed values using the difference between the frame
   size and the previous frame size.  These signed values are encoded as
   VINT, with a mapping from signed to unsigned numbers.  Decoding the
   unsigned number stored in the VINT to a signed number is done by
   subtracting 2^((7*n)-1)-1, where n is the octet size of the VINT.

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       +===================================+======================+
       | Bit Representation of signed VINT | Possible Value Range |
       +===================================+======================+
       | 1xxx xxxx                         | 2^7 values from      |
       |                                   | -(2^6-1) to 2^6      |
       +-----------------------------------+----------------------+
       | 01xx xxxx xxxx xxxx               | 2^14 values from     |
       |                                   | -(2^13-1) to 2^13    |
       +-----------------------------------+----------------------+
       | 001x xxxx xxxx xxxx xxxx xxxx     | 2^21 values from     |
       |                                   | -(2^20-1) to 2^20    |
       +-----------------------------------+----------------------+
       | 0001 xxxx xxxx xxxx xxxx xxxx     | 2^28 values from     |
       | xxxx xxxx                         | -(2^27-1) to 2^27    |
       +-----------------------------------+----------------------+
       | 0000 1xxx xxxx xxxx xxxx xxxx     | 2^35 values from     |
       | xxxx xxxx xxxx xxxx               | -(2^34-1) to 2^34    |
       +-----------------------------------+----------------------+

               Table 38: EBML Lacing signed VINT bits usage

   In our example, the 800, 500 and 1000 frames are stored with EBML
   lacing in a Block as follows:

    +==============+===========+=====================================+
    | Block Octets | Value     | Description                         |
    +==============+===========+=====================================+
    | 4            | 0x02      | Number of frames minus 1            |
    +--------------+-----------+-------------------------------------+
    | 5-6          | 0x43 0x20 | Size of the first frame (800 =      |
    |              |           | 0x320 + 0x4000)                     |
    +--------------+-----------+-------------------------------------+
    | 7-8          | 0x5E 0xD3 | Size of the second frame (500 - 800 |
    |              |           | = -300 = - 0x12C + 0x1FFF + 0x4000) |
    +--------------+-----------+-------------------------------------+
    | 8-807        | <frame1>  | First frame data                    |
    +--------------+-----------+-------------------------------------+
    | 808-1307     | <frame2>  | Second frame data                   |
    +--------------+-----------+-------------------------------------+
    | 1308-2307    | <frame3>  | Third frame data                    |
    +--------------+-----------+-------------------------------------+

                      Table 39: EBML lacing example

   The Block is 2308 octets large and the last frame starts at 1308, so
   we can deduce the size of the last frame is 2308 - 1308 = 1000.

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10.3.4.  Fixed-size lacing

   The Fixed-size lacing doesn't store the frame size, only the number
   of frames in the lace.  Each frame MUST have the same size.  The
   frame size of each frame is deduced from the total size of the Block.
   The bits 5-6 of the Block Header flags are set to 10.

   The Block data with laced frames is stored as follows:

   *  Lacing Head on 1 Octet: Number of frames in the lace minus 1.
   *  Binary data of each frame consecutively.

   For example, for 3 frames of 800 octets each:

          +==============+==========+==========================+
          | Block Octets | Value    | Description              |
          +==============+==========+==========================+
          | 4            | 0x02     | Number of frames minus 1 |
          +--------------+----------+--------------------------+
          | 5-804        | <frame1> | First frame data         |
          +--------------+----------+--------------------------+
          | 805-1604     | <frame2> | Second frame data        |
          +--------------+----------+--------------------------+
          | 1605-2404    | <frame3> | Third frame data         |
          +--------------+----------+--------------------------+

                   Table 40: Fixed-size lacing example

   This gives a Block of 2405 octets.  When reading the Block we find
   that there are 3 frames (Octet 4).  The data start at Octet 5, so the
   size of each frame is (2405 - 5) / 3 = 800.

10.3.5.  Laced Frames Timestamp

   A Block only contains a single timestamp value.  But when lacing is
   used, it contains more than one frame.  Each frame originally has its
   own timestamp, or Presentation Timestamp (PTS).  That timestamp
   applies to the first frame in the lace.

   In the lace, each frame after the first one has an underdetermined
   timestamp.  But each of these frames MUST be contiguous -- i.e. the
   decoded data MUST NOT contain any gap between them.  If there is a
   gap in the stream, the frames around the gap MUST NOT be in the same
   Block.

   Lacing is only useful for small contiguous data to save space.  This
   is usually the case for audio tracks and not the case for video --
   which use a lot of data -- or subtitle tracks -- which have long

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   gaps.  For audio, there is usually a fixed output sampling frequency
   for the whole track.  So the decoder should be able to recover the
   timestamp of each sample, knowing each output sample is contiguous
   with a fixed frequency.  For subtitles this is usually not the case
   so lacing SHOULD NOT be used.

10.4.  Random Access Points

   Random Access Points (RAP) are positions where the parser can seek to
   and start playback without decoding of what was before.  In Matroska
   BlockGroups and SimpleBlocks can be RAPs.  To seek to these elements
   it is still necessary to seek to the Cluster containing them, read
   the Cluster Timestamp and start playback from the BlockGroup or
   SimpleBlock that is a RAP.

   Because a Matroska File is usually composed of multiple tracks
   playing at the same time -- video, audio and subtitles -- to seek
   properly to a RAP, each selected track must be taken in account.
   Usually all audio and subtitle BlockGroup or SimpleBlock are RAP.
   They are independent of each other and can be played randomly.

   Video tracks on the other hand often use references to previous and
   future frames for better coding efficiency.  Frames with such
   reference MUST either contain one or more ReferenceBlock Elements in
   their BlockGroup or MUST be marked as non-keyframe in a SimpleBlock;
   see Section 10.2.

   *  BlockGroup with a frame that references another frame, with the
      EBML tree shown as XML:

   <Cluster>
     <Timestamp>123456</Timestamp>
     <BlockGroup>
       <!-- References a Block 40 Track Ticks before this one -->
       <ReferenceBlock>-40</ReferenceBlock>
       <Block/>
     </BlockGroup>
     ...
   </Cluster>

   *  SimpleBlock with a frame that references another frame, with the
      EBML tree shown as XML:

   <Cluster>
     <Timestamp>123456</Timestamp>
     <SimpleBlock/> (octet 3 bit 0 not set)
     ...
   </Cluster>

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   Frames that are RAP -- i.e. they don't depend on other frames -- MUST
   set the keyframe flag if they are in a SimpleBlock or their parent
   BlockGroup MUST NOT contain a ReferenceBlock.

   *  BlockGroup with a frame that references no other frame, with the
      EBML tree shown as XML:

   <Cluster>
     <Timestamp>123456</Timestamp>
     <BlockGroup>
       <!-- No ReferenceBlock allowed in this BlockGroup -->
       <Block/>
     </BlockGroup>
     ...
   </Cluster>

   *  SimpleBlock with a frame that references no other frame, with the
      EBML tree shown as XML:

   <Cluster>
     <Timestamp>123456</Timestamp>
     <SimpleBlock/> (octet 3 bit 0 set)
     ...
   </Cluster>

   There may be cases where the use of BlockGroup is necessary, as the
   frame may need a BlockDuration, BlockAdditions, CodecState or a
   DiscardPadding element.  For thoses cases a SimpleBlock MUST NOT be
   used, the reference information SHOULD be recovered for non-RAP
   frames.

   *  SimpleBlock with a frame that references another frame, with the
      EBML tree shown as XML:

   <Cluster>
     <Timestamp>123456</Timestamp>
     <SimpleBlock/> (octet 3 bit 0 not set)
     ...
   </Cluster>

   *  Same frame that references another frame put inside a BlockGroup
      to add BlockDuration, with the EBML tree shown as XML:

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   <Cluster>
     <Timestamp>123456</Timestamp>
     <BlockGroup>
       <!-- ReferenceBlock value recovered based on the codec -->
       <ReferenceBlock>-40</ReferenceBlock>
       <BlockDuration>20<BlockDuration>
       <Block/>
     </BlockGroup>
     ...
   </Cluster>

   When a frame in a BlockGroup is not a RAP, the BlockGroup MUST
   contain at least a ReferenceBlock.  The ReferenceBlocks MUST be used
   in one of the following ways:

   *  each reference frame listed as a ReferenceBlock,
   *  some referenced frame listed as a ReferenceBlock, even if the
      timestamp value is accurate,
   *  or one ReferenceBlock with the timestamp value "0" corresponding
      to a self or unknown reference.

   The lack of ReferenceBlock would mean such a frame is a RAP and
   seeking on that frame that actually depends on other frames may
   create bogus output or even crash.

   *  Same frame that references another frame put inside a BlockGroup
      but the reference could not be recovered, with the EBML tree shown
      as XML:

   <Cluster>
     <Timestamp>123456</Timestamp>
     <BlockGroup>
       <!-- ReferenceBlock value not recovered from the codec -->
       <ReferenceBlock>0</ReferenceBlock>
       <BlockDuration>20<BlockDuration>
       <Block/>
     </BlockGroup>
     ...
   </Cluster>

   *  BlockGroup with a frame that references two other frames, with the
      EBML tree shown as XML:

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   <Cluster>
     <Timestamp>123456</Timestamp>
     <BlockGroup>
       <!-- References a Block 80 Track Ticks before this one -->
       <ReferenceBlock>-80</ReferenceBlock>
       <!-- References a Block 40 Track Ticks after this one -->
       <ReferenceBlock>40</ReferenceBlock>
       <Block/>
     </BlockGroup>
     ...
   </Cluster>

   Intra-only video frames, such as the ones found in AV1 or VP9, can be
   decoded without any other frame, but they don't reset the codec
   state.  So seeking to these frames is not possible as the next frames
   may need frames that are not known from this seeking point.  Such
   intra-only frames MUST NOT be considered as keyframes so the keyframe
   flag MUST NOT be set in the SimpleBlock or a ReferenceBlock MUST be
   used to signify the frame is not a RAP.  The timestamp value of the
   ReferenceBlock MUST be "0", meaning it's referencing itself.

   *  Intra-only frame not an RAP, with the EBML tree shown as XML:

   <Cluster>
     <Timestamp>123456</Timestamp>
     <BlockGroup>
       <!-- References itself to mark it should not be used as RAP -->
       <ReferenceBlock>0</ReferenceBlock>
       <Block/>
     </BlockGroup>
     ...
   </Cluster>

   Because a video SimpleBlock has less references information than a
   video BlockGroup, it is possible to remux a video track using
   BlockGroup into a SimpleBlock, as long as it doesn't use any other
   BlockGroup features than ReferenceBlock.

11.  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.

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11.1.  Timestamp Ticks

   All timestamp values in Matroska are expressed in multiples of a
   tick.  They are usually stored as integers.  There are three types of
   ticks possible:

11.1.1.  Matroska Ticks

   For such elements, the timestamp value is stored directly in
   nanoseconds.

   The elements storing values in Matroska Ticks/nanoseconds are:

   *  TrackEntry\DefaultDuration; defined in Section 5.1.4.1.13
   *  TrackEntry\DefaultDecodedFieldDuration; defined in
      Section 5.1.4.1.14
   *  TrackEntry\SeekPreRoll; defined in Section 5.1.4.1.26
   *  TrackEntry\CodecDelay; defined in Section 5.1.4.1.25
   *  BlockGroup\DiscardPadding; defined in Section 5.1.3.5.7
   *  ChapterAtom\ChapterTimeStart; defined in Section 5.1.7.1.4.3
   *  ChapterAtom\ChapterTimeEnd; defined in Section 5.1.7.1.4.4
   *  CuePoint\CueTime; defined in Section 5.1.5.1.1
   *  CueReference\CueRefTime; defined in Section 5.1.5.1.1

11.1.2.  Segment Ticks

   Elements in Segment Ticks involve the use of the TimestampScale
   Element of the Segment to get the timestamp in nanoseconds of the
   element, with the following formula:

   timestamp in nanosecond = element value * TimestampScale

   This allows storing smaller integer values in the elements.

   When using the default value of TimestampScale of "1,000,000", one
   Segment Tick represents one millisecond.

   The elements storing values in Segment Ticks are:

   *  Cluster\Timestamp; defined in Section 5.1.3.1
   *  Info\Duration is stored as a floating-point but the same formula
      applies; defined in Section 5.1.2.10
   *  CuePoint\CueTrackPositions\CueDuration; defined in
      Section 5.1.5.1.2.4

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11.1.3.  Track Ticks

   Elements in Track Ticks involve the use of the TimestampScale Element
   of the Segment and the TrackTimestampScale Element of the Track to
   get the timestamp in nanoseconds of the element, with the following
   formula:

   timestamp in nanoseconds =
       element value * TrackTimestampScale * TimestampScale

   This allows storing smaller integer values in the elements.  The
   resulting floating-point values of the timestamps are still expressed
   in nanoseconds.

   When using the default values for TimestampScale and
   TrackTimestampScale of "1,000,000" and of "1.0" respectively, one
   Track Tick represents one millisecond.

   The elements storing values in Track Ticks are:

   *  Cluster\BlockGroup\Block and Cluster\SimpleBlock timestamps;
      detailed in Section 11.2
   *  Cluster\BlockGroup\BlockDuration; defined in Section 5.1.3.5.3
   *  Cluster\BlockGroup\ReferenceBlock; defined in Section 5.1.3.5.5

   When the TrackTimestampScale is interpreted as "1.0", Track Ticks are
   equivalent to Segment Ticks and give an integer value in nanoseconds.
   This is the most common case as TrackTimestampScale is usually
   omitted.

   A value of TrackTimestampScale other than "1.0" MAY be used to scale
   the timestamps more in tune with each Track sampling frequency.  For
   historical reasons, a lot of Matroska readers don't take the
   TrackTimestampScale value in account.  So using a value other than
   "1.0" might not work in many places.

11.2.  Block Timestamps

   A Block Element and SimpleBlock Element timestamp is the time when
   the decoded data of the first frame in the Block/SimpleBlock MUST be
   presented, if the track of that Block/SimpleBlock is selected for
   playback.  This is also known as the Presentation Timestamp (PTS).

   The Block Element and SimpleBlock Element store their timestamps as
   signed integers, relative to the Cluster\Timestamp value of the
   Cluster they are stored in.  To get the timestamp of a Block or
   SimpleBlock in nanoseconds you have to use the following formula:

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   ( Cluster\Timestamp + ( block timestamp * TrackTimestampScale ) ) *
   TimestampScale

   The Block Element and SimpleBlock Element store their timestamps as
   16bit signed integers, allowing a range from "-32768" to "+32767"
   Track Ticks.  Although these values can be negative, when added to
   the Cluster\Timestamp, the resulting frame timestamp SHOULD NOT be
   negative.

   When a CodecDelay Element is set, its value MUST be substracted from
   each Block timestamp of that track.  To get the timestamp in
   nanoseconds of the first frame in a Block or SimpleBlock, the formula
   becomes:

   ( ( Cluster\Timestamp + ( block timestamp * TrackTimestampScale ) ) *
     TimestampScale ) - CodecDelay

   The resulting frame timestamp SHOULD NOT be negative.

   During playback, when a frame has a negative timestamp, the content
   MUST be decoded by the decoder but not played to the user.

11.3.  TimestampScale Rounding

   The default Track Tick duration is one millisecond.

   The TimestampScale is a floating-point value, which is usually 1.0.
   But when it's not, the multiplied Block Timestamp is a floating-point
   value in nanoseconds.  The Matroska Reader SHOULD use the nearest
   rounding value in nanosecond to get the proper nanosecond timestamp
   of a Block.  This allows some clever TimestampScale values to have
   more refined timestamp precision per frame.

12.  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".

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   Starting in Matroska version 4, either [ISO639-2] or [BCP47] MAY be
   used, although BCP 47 is RECOMMENDED.  The BCP 47 Language Elements
   are "LanguageBCP47 Element", "TagLanguageBCP47 Element", and
   "ChapLanguageBCP47 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.

13.  Country Codes

   Country codes are the [BCP47] two-letter region subtag, without the
   UK exception.

14.  Encryption

   This Matroska specification provides no interoperable solution for
   securing the data container with any assurances of confidentiality,
   integrity, authenticity, or to provide authorization.  The
   ContentEncryption Element (Section 5.1.4.1.31.8) and associated sub-
   fields (Section 5.1.4.1.31.9 to Section 5.1.4.1.31.12) are defined
   only for the benefit of implementers to construct their own
   proprietary solution or as the basis for further standardization
   activities.  How to use these fields to secure a Matroska data
   container is out of scope, as are any related issues such as key
   management and distribution.

   A Matroska Reader who encounters containers that use the fields
   defined in this section MUST rely on out-of-scope guidance to decode
   the associated content.

   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.

   For encryption systems sharing public/private keys, the creation of
   the keys and the exchange of keys are not covered by this document.
   They have to be handled by the system using Matroska.

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   The algorithms described in Table 26 support different modes of
   operations and key sizes.  The specification of these parameters is
   required for a complete solution, but is out of scope of this
   document and left to the proprietary implementations using them or
   subsequent profiles of this document.

   The ContentEncodingScope Element gives an idea of which part of the
   track are encrypted.  But each ContentEncAlgo Element and its sub
   elements like AESSettingsCipherMode really define how the encrypted
   should be exactly interpreted.

   An example of an extension that builds upon these security-related
   fields in this specification is [WebM-Enc].  It uses AES-CTR,
   ContentEncAlgo = 5 (Section 5.1.4.1.31.9) and AESSettingsCipherMode =
   1 (Section 5.1.4.1.31.12).

   A Matroska Writer MUST NOT use insecure cryptographic algorithms to
   create new archives or streams, but a Matroska Reader MAY support
   these algorithms to read previously made archives or stream.

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 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.

   Cropping has to be performed before resizing and the display
   dimensions given by DisplayWidth, DisplayHeight and DisplayUnit apply
   to the already cropped image.

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15.2.  Rotation

   The ProjectionPoseRoll Element (see Section 5.1.4.1.28.46) 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 5.1.4.1.28.41) and
   the ProjectionPoseRoll Element represents a video track where the
   image SHOULD be presented with a 90-degree counter-clockwise
   rotation, with the EBML tree shown as XML :

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

                        Figure 15: Rotation example.

16.  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.

16.1.  Segment Position Exception

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

16.2.  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".

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        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|
        ^ EBML Header
      0 |                                               |18|53|80|67|
                                                        ^ Segment ID
     20 |93|
        ^ Segment Data Size
     20 |  |15|49|A9|66|8E|4D|80|84|69|65|74|66|57|41|84|69|65|74|66|
           ^ Start of Segment data
     20 |                 |4D|80|84|69|65|74|66|57|41|84|69|65|74|66|
                          ^ MuxingApp start

   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'.

17.  Linked Segments

   Matroska provides several methods to link two or more Segment
   Elements together to create a Linked Segment.  A Linked Segment is a
   set of multiple Segments linked together into a single presentation
   by using Hard Linking or Medium Linking.

   All Segments within a Linked Segment MUST have a SegmentUUID.

   All Segments within a Linked Segment SHOULD be stored within the same
   directory or be accessible quickly based on their SegmentUUID in
   order to have seamless transition between segments.

   All Segments within a Linked Segment MAY set a SegmentFamily with a
   common value to make it easier for a Matroska Player to know which
   Segments are meant to be played together.

   The SegmentFilename, PrevFilename and NextFilename elements MAY also
   give hints on the original filenames that were used when the Segment
   links were created, in case some SegmentUUID are damaged.

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17.1.  Hard Linking

   Hard Linking, also called splitting, is the process of creating a
   Linked Segment by linking multiple Segment Elements using the
   NextUUID and PrevUUID Elements.

   All Segments within a Hard Linked Segment MUST use the same Tracks
   list and TimestampScale.

   Within a Linked Segment, the timestamps of Block and SimpleBlock MUST
   follow consecutively the timestamps of Block and SimpleBlock from the
   previous Segment in linking order.

   With Hard Linking, the chapters of any Segment within the Linked
   Segment MUST only reference the current Segment.  The NextUUID and
   PrevUUID reference the respective SegmentUUID values of the next and
   previous Segments.

   The first Segment of a Linked Segment MUST NOT have a PrevUUID
   Element.  The last Segment of a Linked Segment MUST NOT have a
   NextUUID Element.

   For each node of the chain of Segments of a Linked Segment at least
   one Segment MUST reference the other Segment within the chain.

   In a chain of Segments of a Linked Segment the NextUUID always takes
   precedence over the PrevUUID.  So if SegmentA has a NextUUID to
   SegmentB and SegmentB has a PrevUUID to SegmentC, the link to use is
   NextUUID between SegmentA and SegmentB, SegmentC is not part of the
   Linked Segment.

   If SegmentB has a PrevUUID to SegmentA but SegmentA has no NextUUID,
   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 SegmentUUID, PrevUUID, and
   NextUUID, as in this table:

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    +==========+================+==================+==================+
    |file name |SegmentUUID     | PrevUUID         | NextUUID         |
    +==========+================+==================+==================+
    |start.mkv |71000c23cd310998| Invalid          | a77b3598941cb803 |
    |          |53fbc94dd984a5dd|                  | eac0fcdafe44fac9 |
    +----------+----------------+------------------+------------------+
    |middle.mkv|a77b3598941cb803| 71000c23cd310998 | 6c92285fa6d3e827 |
    |          |eac0fcdafe44fac9| 53fbc94dd984a5dd | b198d120ea3ac674 |
    +----------+----------------+------------------+------------------+
    |end.mkv   |6c92285fa6d3e827| a77b3598941cb803 | Invalid          |
    |          |b198d120ea3ac674| eac0fcdafe44fac9 |                  |
    +----------+----------------+------------------+------------------+

                     Table 41: Usual Hard Linking UIDs

   An other example where only the NextUUID Element is used:

      +============+==================+==========+==================+
      | file name  | SegmentUUID      | PrevUUID | NextUUID         |
      +============+==================+==========+==================+
      | start.mkv  | 71000c23cd310998 | Invalid  | a77b3598941cb803 |
      |            | 53fbc94dd984a5dd |          | eac0fcdafe44fac9 |
      +------------+------------------+----------+------------------+
      | middle.mkv | a77b3598941cb803 | n/a      | 6c92285fa6d3e827 |
      |            | eac0fcdafe44fac9 |          | b198d120ea3ac674 |
      +------------+------------------+----------+------------------+
      | end.mkv    | 6c92285fa6d3e827 | n/a      | Invalid          |
      |            | b198d120ea3ac674 |          |                  |
      +------------+------------------+----------+------------------+

                  Table 42: Hard Linking without PrevUUID

   An example where only the PrevUUID Element is used:

      +============+==================+==================+==========+
      | file name  | SegmentUUID      | PrevUUID         | NextUUID |
      +============+==================+==================+==========+
      | start.mkv  | 71000c23cd310998 | Invalid          | n/a      |
      |            | 53fbc94dd984a5dd |                  |          |
      +------------+------------------+------------------+----------+
      | middle.mkv | a77b3598941cb803 | 71000c23cd310998 | n/a      |
      |            | eac0fcdafe44fac9 | 53fbc94dd984a5dd |          |
      +------------+------------------+------------------+----------+
      | end.mkv    | 6c92285fa6d3e827 | a77b3598941cb803 | Invalid  |
      |            | b198d120ea3ac674 | eac0fcdafe44fac9 |          |
      +------------+------------------+------------------+----------+

                  Table 43: Hard Linking without NextUUID

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   In this example only the middle.mkv is using the PrevUUID and
   NextUUID Elements:

    +==========+================+==================+==================+
    |file name |SegmentUUID     | PrevUUID         | NextUUID         |
    +==========+================+==================+==================+
    |start.mkv |71000c23cd310998| Invalid          | n/a              |
    |          |53fbc94dd984a5dd|                  |                  |
    +----------+----------------+------------------+------------------+
    |middle.mkv|a77b3598941cb803| 71000c23cd310998 | 6c92285fa6d3e827 |
    |          |eac0fcdafe44fac9| 53fbc94dd984a5dd | b198d120ea3ac674 |
    +----------+----------------+------------------+------------------+
    |end.mkv   |6c92285fa6d3e827| n/a              | Invalid          |
    |          |b198d120ea3ac674|                  |                  |
    +----------+----------------+------------------+------------------+

                Table 44: Hard Linking with mixed UID links

17.2.  Medium Linking

   Medium Linking creates relationships between Segments using Ordered
   Chapters (Section 20.1.3) and the ChapterSegmentUUID Element.  A
   Chapter Edition with Ordered Chapters MAY contain Chapter elements
   that reference timestamp ranges from other Segments.  The Segment
   referenced by the Ordered Chapter via the ChapterSegmentUUID 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 previous
   Ordered Chapters.

   As an example a file named intro.mkv could have a SegmentUUID 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 ChapterSegmentUUID, 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 ChapterSegmentUUID in an enabled Edition and present the
   reference content of the two Segments as a single presentation.

   The ChapterSegmentUUID represents the Segment that holds the content
   to play in place of the Linked Chapter.  The ChapterSegmentUUID MUST
   NOT be the SegmentUUID of its own Segment.

   There are 2 ways to use a chapter link:

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   *  Linked-Duration linking,

   *  Linked-Edition linking

17.2.1.  Linked-Duration

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

   ChapterTimeStart and ChapterTimeEnd represent timestamps in the
   Linked Segment matching the value of ChapterSegmentUUID.  Their
   values MUST be in the range of the linked Segment duration.

   The ChapterTimeEnd value MUST be set when using linked-duration
   chapter linking.  ChapterSegmentEditionUID MUST NOT be set.

17.2.2.  Linked-Edition

   A Matroska Player MUST play the whole linked Edition of the linked
   Segment in place of the Linked Chapter.

   ChapterSegmentEditionUID represents a valid Edition from the Linked
   Segment matching the value of ChapterSegmentUUID.

   When using linked-edition chapter linking.  ChapterTimeEnd is
   OPTIONAL.

18.  Track Flags

18.1.  Default flag

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

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

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18.2.  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.

18.3.  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.

18.4.  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.

18.5.  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.

18.6.  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.

18.7.  Commentary flag

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

18.8.  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.

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   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 union 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.

18.9.  Overlay Track

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

18.10.  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.

   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).

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   For separate tracks, Matroska needs to define exactly which track
   does what.  TrackOperation with TrackCombinePlanes do that.  For more
   details look at Section 18.8 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;
   see OldStereoMode (Section 5.1.4.1.28.5).  Matroska Readers MAY
   support these legacy files by checking Matroska v2 or 0x53B9.  The
   older values of StereoMode were 0: mono, 1: right eye, 2: left eye,
   3: both eyes, the only values that can be found in OldStereoMode.
   They are not compatible with the StereoMode values found in Matroska
   v3 and above.

19.  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.

19.1.  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 45: 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 seems equally and maximally preferable, it
   SHOULD default to the first of the group.

19.2.  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 46: 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.

20.  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 [DVD-Video], or have its own built-in Matroska menu
   structure.

20.1.  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.

20.1.1.  EditionFlagDefault

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

20.1.2.  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 47: Default edition, all default

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

                   Table 48: Default edition, no default

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

                  Table 49: Default edition, with default

20.1.3.  EditionFlagOrdered

   The EditionFlagOrdered Flag is a significant feature as it enables an
   Edition of Ordered Chapters which defines and arranges a virtual
   timeline rather than simply labeling points within the timeline.  For
   example, with Editions of Ordered Chapters a single Matroska file can
   present multiple edits of a film without duplicating content.
   Alternatively, if a videotape is digitized in full, one Ordered
   Edition could present the full content (including colorbars,
   countdown, slate, a feature presentation, and black frames), while
   another Edition of Ordered Chapters can use Chapters that only mark
   the intended presentation with the colorbars and other ancillary

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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 evaluates to "0", 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.  In
   that case these elements are informational only.

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

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

                     Table 50: elements only found in
                             ordered chapters

   Furthermore, there are other EBML Elements which could be used if the
   EditionFlagOrdered evaluates to "1".

20.1.3.1.  Ordered-Edition and Matroska Segment-Linking

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

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

   See Section 17 on the Linked Segments for more information about Hard
   Linking and Medium Linking.

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20.2.  ChapterAtom

   The ChapterAtom is also called a Chapter.

20.2.1.  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.

20.2.2.  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
   greater than or equal to the start timestamp.

   When the ChapterTimeEnd timestamp is equal to the ChapterTimeStart
   timestamp, the timestamps is included in the Chapter.  It can be
   useful to put markers in a file or add chapter commands with ordered
   chapter commands without having to play anything; see
   Section 5.1.7.1.4.14.

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

                Table 51: ChapterTimeEnd usage possibilities

20.2.3.  Nested Chapters

   A ChapterAtom element can contain other ChapterAtom elements.  That
   element is a Parent Chapter and the ChapterAtom elements it contains
   are Nested Chapters.

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   Nested Chapters can be useful to tag small parts of a Segment that
   already have tags or add Chapter Codec commands on smaller parts of a
   Segment that already have Chapter Codec commands.

   The ChapterTimeStart of a Nested Chapter MUST be greater than or
   equal to the ChapterTimeStart its Parent Chapter.

   If the Parent Chapter of a Nested Chapter has a ChapterTimeEnd, the
   ChapterTimeStart of that Nested Chapter MUST be smaller than or equal
   to the ChapterTimeEnd of the Parent Chapter.

20.2.4.  Nested Chapters in Ordered Chapters

   The ChapterTimeEnd of the lowest level of Nested Chapters MUST be set
   for Ordered Chapters.

   When used with Ordered Chapters, the ChapterTimeEnd value of a Parent
   Chapter is useless for playback as the proper playback sections are
   described in its Nested Chapters.  The ChapterTimeEnd SHOULD NOT be
   set in Parent Chapters and MUST be ignored for playback.

20.2.5.  ChapterFlagHidden

   Each Chapter ChapterFlagHidden flag works independently of parent
   chapters.  A Nested Chapter with a ChapterFlagHidden that evaluates
   to "0" remains visible in the user interface even if the Parent
   Chapter ChapterFlagHidden flag is set to "1".

        +==========================+===================+=========+
        | Chapter + Nested Chapter | ChapterFlagHidden | visible |
        +==========================+===================+=========+
        | Chapter 1                | 0                 | yes     |
        +--------------------------+-------------------+---------+
        | Nested Chapter 1.1       | 0                 | yes     |
        +--------------------------+-------------------+---------+
        | Nested Chapter 1.2       | 1                 | no      |
        +--------------------------+-------------------+---------+
        | Chapter 2                | 1                 | no      |
        +--------------------------+-------------------+---------+
        | Nested Chapter 2.1       | 0                 | yes     |
        +--------------------------+-------------------+---------+
        | Nested Chapter 2.2       | 1                 | no      |
        +--------------------------+-------------------+---------+

              Table 52: ChapterFlagHidden nested visibility

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20.3.  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 [DVD-Video].  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 as 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.

20.4.  Physical Types

   Each level can have different meanings for audio and video.  The
   ORIGINAL_MEDIA_TYPE tag [MatroskaTags] 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 53: ChapterPhysicalEquiv meaning per track type

20.5.  Chapter Examples

20.5.1.  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.

   *  00000 ms - 05000 ms : Intro
   *  05000 ms - 25000 ms : Before the crime
   *  25000 ms - 27500 ms : The crime
   *  27500 ms - 38000 ms : The killer arrested
   *  38000 ms - 43000 ms : Credits

   This would translate in the following matroska form, with the EBML
   tree shown as XML :

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   <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>Apres le crime</ChapString>
           <ChapLanguage>fra</ChapLanguage>
         </ChapterDisplay>
       </ChapterAtom>
       <ChapterAtom>

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

                     Figure 16: Basic Chapters Example.

20.5.2.  Example 2 : nested chapters

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

20.5.2.1.  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

   This would translate in the following matroska form, with the EBML
   tree shown as XML :

   <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>

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           <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>
           <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>

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       <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 17: Nested Chapters Example.

21.  Attachments

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

   Matroska Readers MUST NOT execute files stored as Attachment
   Elements.

21.1.  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.

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   Only [JPEG] and PNG [RFC2083] 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.

      +======================+===================+=================+
      | 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 54: Cover Art Filenames

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21.2.  Font files

   Font files MAY be added to a Matroska file as Attachments so that the
   font file may be used to display an associated subtitle track.  This
   allows the presentation of a Matroska file to be consistent in
   various environments where the needed fonts might not be available on
   the local system.

   Depending on the font format in question, each font file can contain
   multiple font variants.  Each font variant has a name which will be
   referred to as Font Name from now on.  This Font Name can be
   different from the Attachment's FileName, even when disregarding the
   extension.  In order to select a font for display, a Matroska player
   SHOULD consider both the Font Name and the base name of the
   Attachment's FileName, preferring the former when there are multiple
   matches.

   Subtitle codecs, such as SubStation Alpha (SSA/ASS), usually refer to
   a font by its Font Name, not by its filename.  If none of the
   Attachments are a match for the Font Name, the Matroska player SHOULD
   attempt to find a system font whose Font Name matches the one used in
   the subtitle track.

   Since loading fonts temporarily can take a while, a Matroska player
   usually loads or installs all the fonts found in attachments so they
   are ready to be used during playback.  Failure to use the font
   attachment might result in incorrect rendering of the subtitles.

   If a selected subtitle track has some AttachmentLink elements, the
   player MAY restrict its font rendering to use only these fonts.

   A Matroska player SHOULD handle the official font media types from
   [RFC8081] when the system can handle the type:

   *  font/sfnt: Generic SFNT Font Type,

   *  font/ttf: TTF Font Type,

   *  font/otf: OpenType Layout (OTF) Font Type,

   *  font/collection: Collection Font Type,

   *  font/woff: WOFF 1.0,

   *  font/woff2: WOFF 2.0.

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   Fonts in Matroska existed long before [RFC8081].  A few unofficial
   media types for fonts were used in existing files.  Therefore, it is
   RECOMMENDED for a Matroska player to support the following legacy
   media types for font attachments:

   *  application/x-truetype-font: Truetype fonts, equivalent to font/
      ttf and sometimes font/otf,

   *  application/x-font-ttf: TTF fonts, equivalent to font/ttf,

   *  application/vnd.ms-opentype: OpenType Layout fonts, equivalent to
      font/otf

   *  application/font-sfnt: Generic SFNT Font Type, equivalent to font/
      sfnt

   *  application/font-woff: WOFF 1.0, equivalent to font/woff

   There may also be some font attachments with the application/octet-
   stream media type.  In that case the Matroska player MAY try to guess
   the font type by checking the file extension of the
   AttachedFile\FileName string.  Common file extensions for fonts are:

   *  .ttf for Truetype fonts, equivalent to font/ttf,

   *  .otf for OpenType Layout fonts, equivalent to font/otf,

   *  .ttc for Collection fonts, equivalent to font/collection

   The file extension check MUST be case-insensitive.

   Matroska writers SHOULD use a valid font media type from [RFC8081] in
   the AttachedFile\FileMediaType of the font attachment.  They MAY use
   the media types found in older files when compatibility with older
   players is necessary.

22.  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.

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22.1.  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.

   *  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.

23.  Matroska Streaming

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

23.1.  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 guidelines in

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   Section 25, 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.

23.2.  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 file-like protocols like
   HTTP, QUIC, etc. 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
   SeekHead, 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 SeekHead list nor a Cues list
   at the beginning of the stream, it SHOULD be considered non-seekable.
   Even though it is possible to seek 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.

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24.  Tags

24.1.  Tags Precedence

   Tags allow tagging all kinds of Matroska parts with very detailed
   metadata in multiple languages.

   Some Matroska elements also contain their own string value like the
   Track Name (Section 5.1.4.1.18) or the Chapter String
   (Section 5.1.7.1.4.10).

   The following Matroska elements can also be defined with tags:

   *  The Track Name Element (Section 5.1.4.1.18) corresponds to a tag
      with the TagTrackUID (Section 5.1.8.1.1.3) set to the given track,
      a TagName of TITLE (Section 5.1.8.1.2.1) and a TagLanguage
      (Section 5.1.8.1.2.2) or TagLanguageBCP47 (Section 5.1.8.1.2.3) of
      "und".

   *  The Chapter String Element (Section 5.1.7.1.4.10) corresponds to a
      tag with the TagChapterUID (Section 5.1.8.1.1.5) set to the same
      chapter UID, a TagName of TITLE (Section 5.1.8.1.2.1) and a
      TagLanguage (Section 5.1.8.1.2.2) or TagLanguageBCP47
      (Section 5.1.8.1.2.3) matching the ChapLanguage
      (Section 5.1.7.1.4.11) or ChapLanguageBCP47 (Section 5.1.7.1.4.12)
      respectively.

   *  The FileDescription Element (Section 5.1.6.1.1) of an attachment
      corresponds to a tag with the TagAttachmentUID
      (Section 5.1.8.1.1.6) set to the given attachment, a TagName of
      TITLE (Section 5.1.8.1.2.1) and a TagLanguage
      (Section 5.1.8.1.2.2) or TagLanguageBCP47 (Section 5.1.8.1.2.3) of
      "und".

   When both values exist in the file, the value found in Tags takes
   precedence over the value found in original location of the element.
   For example, if you have a TrackEntry\Name element and Tag TITLE for
   that track in a Matroska Segment, the Tag string SHOULD be used and
   not the TrackEntry\Name string to identify the track.

   As the Tag element is optional, a lot of Matroska Readers do not
   handle it and will not use the tags value when it's found.  So for
   maximum compatibility, it's usually better to put the strings in the
   TrackEntry, ChapterAtom and Attachment and keep the tags matching
   these values if tags are also used.

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24.2.  Tag Levels

   Tag elements allow tagging information on multiple levels, each level
   having a TargetTypeValue Section 5.1.8.1.1.1.  An element for a given
   TargetTypeValue also applies to the lower levels denoted by smaller
   TargetTypeValue values.  If an upper value doesn't apply to a level
   but the actual value to use is not known, an empty TagString
   (Section 5.1.8.1.2.5) or an empty TagBinary (Section 5.1.8.1.2.6)
   element MUST be used as the tag value for this level.

   See [MatroskaTags] for more details on common tag names, types and
   descriptions.

25.  Implementation Recommendations

25.1.  Cluster

   It is RECOMMENDED that each individual Cluster Element contains no
   more than 5 seconds or 5 megabytes of content.

25.2.  SeekHead

   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.

   The size of this Void Element should be adjusted depending on the
   Matroska file already having Tags, Chapters, and Attachments
   Elements.

25.3.  Optimum Layouts

   While there can be Top-Level Elements in any order, some ordering of
   Elements are better than others.  Here are few optimum layouts for
   different use case:

25.3.1.  Optimum layout for a muxer

   This is the basic layout muxers should be using for an efficient
   playback experience.

   *  SeekHead
   *  Info
   *  Tracks
   *  Chapters
   *  Attachments
   *  Tags

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   *  Clusters
   *  Cues

25.3.2.  Optimum layout after editing tags

   When tags from the previous layout need to be extended, they are
   moved to the end with the extra information.  The location where the
   old tags were located is voided.

   *  SeekHead
   *  Info
   *  Tracks
   *  Chapters
   *  Attachments
   *  Void
   *  Clusters
   *  Cues
   *  Tags

25.3.3.  Optimum layout with Cues at the front

   Cues are usually a big chunk of data referencing a lot of locations
   in the file.  For players that want to seek in the file they need to
   seek to the end of the file to access these locations.  It is often
   better if they are placed early in the file.  On the other hand that
   means players that don't intend to seek will have to read/skip these
   data no matter what.

   Because the Cues reference locations further in the file, it's often
   complicated to allocate the proper space for that element before all
   the locations are known.  Therefore, this layout is rarely used.

   *  SeekHead
   *  Info
   *  Tracks
   *  Chapters
   *  Attachments
   *  Tags
   *  Cues
   *  Clusters

25.3.4.  Optimum layout for livestreaming

   In Livestreaming (Section 23.2) only a few elements make sense.
   SeekHead and Cues are useless for example.  All elements other than
   the Clusters MUST be placed before the Clusters.

   *  Info

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   *  Tracks
   *  Attachments (rare)
   *  Tags
   *  Clusters

26.  Security Considerations

   Matroska inherits security considerations from EBML.

   Attacks on a Matroska Reader could include:

   *  Storage of an 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 or not use the attachement.

   *  A Matroska Attachment with an inaccurate media type.

   *  Damage to the Encryption and Compression fields (Section 14) that
      would result in bogus binary data interpreted by the decoder.

   *  Chapter Codecs running unwanted commands on the host system.

   The same error handling done for EBML applies to Matroska files.
   Particular error handling is not covered in this specification as
   this is depends on the goal of the Matroska Readers.  It is up to the
   decision of the Matroska Readers on how to handle the errors if they
   are recoverable in their code or not.  For example, if the checksum
   of the \Segment\Tracks is invalid some could decide to try to read
   the data anyway, some will just reject the file, most will not even
   check it.

   Matroska Reader implementations need to be robust against malicious
   payloads.  Those related to denial of service are outlined in
   Section 2.1 of [RFC4732].
   Although rarer, the same may apply to a Matroska Writer.  Malicious
   stream data must not cause the Writer to misbehave, as this might
   allow an attacker access to transcoding gateways.

   As an audio and visual container format, a Matroska file or stream
   will potentially encapsulate numerous byte streams created with a
   variety of codecs.  Implementers will need to consider the security
   considerations of these encapsulated formats.

27.  IANA Considerations

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27.1.  Matroska Element IDs Registry

   This document creates a new IANA registry called the "Matroska
   Element IDs" registry.

   To register a new Element ID in this registry, one needs an Element
   ID, a Change Controller (IETF or email of registrant) and an optional
   Reference to a document describing the Element ID.

   Element IDs are encoded using the VINT mechanism described in
   Section 4 of [RFC8794] and can be between one and five octets long.
   Five-octet-long Element IDs are possible only if declared in the EBML
   header.

   Element IDs are described in Section 5 of [RFC8794] with errata 7189
   and 7191.

   One-octet Matroska Element IDs are to be allocated according to the
   "RFC Required" policy [RFC8126].

   Two-octet Matroska Element IDs are to be allocated according to the
   "Specification Required" policy [RFC8126].

   Three-octet and four-octet Matroska Element IDs are to be allocated
   according to the "First Come First Served" policy [RFC8126].

   The allowed values in the Elements IDs registry are similar to the
   ones found in the EBML Element IDs registry defined in Section 17.1
   of [RFC8794].

   EBML IDs defined for the EBML Header -- as defined in Section 17.1 of
   [RFC8794] -- MUST NOT be used as Matroska Element IDs.

   Given the scarcity of the One-octet Element IDs, they should only be
   created to save space for elements found many times in a file.  For
   example, within a BlockGroup or Chapters.  The Four-octet Element IDs
   are mostly for synchronization of large elements.  They should only
   be used for such high level elements.  Elements that are not expected
   to be used often should use Three-octet Element IDs.

   Elements found in Section 28 have an assigned Matroska Element ID for
   historical reasons.  These elements are not in use and SHOULD NOT be
   reused unless there is no other IDs available with the desired size.
   Such IDs are considered as reclaimed to the IANA registry as they
   could be used for other things in the future.

   Matroska Element IDs Values found in this document are assigned as
   initial values as follows:

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    +============+=============================+======================+
    | Element ID | Element Name                | Reference            |
    +============+=============================+======================+
    |       0x80 | ChapterDisplay              | Described in         |
    |            |                             | Section 5.1.7.1.4.9  |
    +------------+-----------------------------+----------------------+
    |       0x83 | TrackType                   | Described in         |
    |            |                             | Section 5.1.4.1.3    |
    +------------+-----------------------------+----------------------+
    |       0x85 | ChapString                  | Described in         |
    |            |                             | Section 5.1.7.1.4.10 |
    +------------+-----------------------------+----------------------+
    |       0x86 | CodecID                     | Described in         |
    |            |                             | Section 5.1.4.1.21   |
    +------------+-----------------------------+----------------------+
    |       0x88 | FlagDefault                 | Described in         |
    |            |                             | Section 5.1.4.1.5    |
    +------------+-----------------------------+----------------------+
    |       0x8E | Slices                      | Reclaimed            |
    |            |                             | (Section 28.5)       |
    +------------+-----------------------------+----------------------+
    |       0x91 | ChapterTimeStart            | Described in         |
    |            |                             | Section 5.1.7.1.4.3  |
    +------------+-----------------------------+----------------------+
    |       0x92 | ChapterTimeEnd              | Described in         |
    |            |                             | Section 5.1.7.1.4.4  |
    +------------+-----------------------------+----------------------+
    |       0x96 | CueRefTime                  | Described in         |
    |            |                             | Section 5.1.5.1.2.8  |
    +------------+-----------------------------+----------------------+
    |       0x97 | CueRefCluster               | Reclaimed            |
    |            |                             | (Section 28.37)      |
    +------------+-----------------------------+----------------------+
    |       0x98 | ChapterFlagHidden           | Described in         |
    |            |                             | Section 5.1.7.1.4.5  |
    +------------+-----------------------------+----------------------+
    |       0x9A | FlagInterlaced              | Described in         |
    |            |                             | Section 5.1.4.1.28.1 |
    +------------+-----------------------------+----------------------+
    |       0x9B | BlockDuration               | Described in         |
    |            |                             | Section 5.1.3.5.3    |
    +------------+-----------------------------+----------------------+
    |       0x9C | FlagLacing                  | Described in         |
    |            |                             | Section 5.1.4.1.12   |
    +------------+-----------------------------+----------------------+
    |       0x9D | FieldOrder                  | Described in         |
    |            |                             | Section 5.1.4.1.28.2 |
    +------------+-----------------------------+----------------------+

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    |       0x9F | Channels                    | Described in         |
    |            |                             | Section 5.1.4.1.29.3 |
    +------------+-----------------------------+----------------------+
    |       0xA0 | BlockGroup                  | Described in         |
    |            |                             | Section 5.1.3.5      |
    +------------+-----------------------------+----------------------+
    |       0xA1 | Block                       | Described in         |
    |            |                             | Section 5.1.3.5.1    |
    +------------+-----------------------------+----------------------+
    |       0xA2 | BlockVirtual                | Reclaimed            |
    |            |                             | (Section 28.3)       |
    +------------+-----------------------------+----------------------+
    |       0xA3 | SimpleBlock                 | Described in         |
    |            |                             | Section 5.1.3.4      |
    +------------+-----------------------------+----------------------+
    |       0xA4 | CodecState                  | Described in         |
    |            |                             | Section 5.1.3.5.6    |
    +------------+-----------------------------+----------------------+
    |       0xA5 | BlockAdditional             | Described in         |
    |            |                             | Section 5.1.3.5.2.2  |
    +------------+-----------------------------+----------------------+
    |       0xA6 | BlockMore                   | Described in         |
    |            |                             | Section 5.1.3.5.2.1  |
    +------------+-----------------------------+----------------------+
    |       0xA7 | Position                    | Described in         |
    |            |                             | Section 5.1.3.2      |
    +------------+-----------------------------+----------------------+
    |       0xAA | CodecDecodeAll              | Reclaimed            |
    |            |                             | (Section 28.22)      |
    +------------+-----------------------------+----------------------+
    |       0xAB | PrevSize                    | Described in         |
    |            |                             | Section 5.1.3.3      |
    +------------+-----------------------------+----------------------+
    |       0xAE | TrackEntry                  | Described in         |
    |            |                             | Section 5.1.4.1      |
    +------------+-----------------------------+----------------------+
    |       0xAF | EncryptedBlock              | Reclaimed            |
    |            |                             | (Section 28.15)      |
    +------------+-----------------------------+----------------------+
    |       0xB0 | PixelWidth                  | Described in         |
    |            |                             | Section 5.1.4.1.28.6 |
    +------------+-----------------------------+----------------------+
    |       0xB2 | CueDuration                 | Described in         |
    |            |                             | Section 5.1.5.1.2.4  |
    +------------+-----------------------------+----------------------+
    |       0xB3 | CueTime                     | Described in         |
    |            |                             | Section 5.1.5.1.1    |
    +------------+-----------------------------+----------------------+

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    |       0xB5 | SamplingFrequency           | Described in         |
    |            |                             | Section 5.1.4.1.29.1 |
    +------------+-----------------------------+----------------------+
    |       0xB6 | ChapterAtom                 | Described in         |
    |            |                             | Section 5.1.7.1.4    |
    +------------+-----------------------------+----------------------+
    |       0xB7 | CueTrackPositions           | Described in         |
    |            |                             | Section 5.1.5.1.2    |
    +------------+-----------------------------+----------------------+
    |       0xB9 | FlagEnabled                 | Described in         |
    |            |                             | Section 5.1.4.1.4    |
    +------------+-----------------------------+----------------------+
    |       0xBA | PixelHeight                 | Described in         |
    |            |                             | Section 5.1.4.1.28.7 |
    +------------+-----------------------------+----------------------+
    |       0xBB | CuePoint                    | Described in         |
    |            |                             | Section 5.1.5.1      |
    +------------+-----------------------------+----------------------+
    |       0xC0 | TrickTrackUID               | Reclaimed            |
    |            |                             | (Section 28.28)      |
    +------------+-----------------------------+----------------------+
    |       0xC1 | TrickTrackSegmentUID        | Reclaimed            |
    |            |                             | (Section 28.29)      |
    +------------+-----------------------------+----------------------+
    |       0xC4 | TrickMasterTrackSegmentUID  | Reclaimed            |
    |            |                             | (Section 28.32)      |
    +------------+-----------------------------+----------------------+
    |       0xC6 | TrickTrackFlag              | Reclaimed            |
    |            |                             | (Section 28.30)      |
    +------------+-----------------------------+----------------------+
    |       0xC7 | TrickMasterTrackUID         | Reclaimed            |
    |            |                             | (Section 28.31)      |
    +------------+-----------------------------+----------------------+
    |       0xC8 | ReferenceFrame              | Reclaimed            |
    |            |                             | (Section 28.12)      |
    +------------+-----------------------------+----------------------+
    |       0xC9 | ReferenceOffset             | Reclaimed            |
    |            |                             | (Section 28.13)      |
    +------------+-----------------------------+----------------------+
    |       0xCA | ReferenceTimestamp          | Reclaimed            |
    |            |                             | (Section 28.14)      |
    +------------+-----------------------------+----------------------+
    |       0xCB | BlockAdditionID             | Reclaimed            |
    |            |                             | (Section 28.9)       |
    +------------+-----------------------------+----------------------+
    |       0xCC | LaceNumber                  | Reclaimed            |
    |            |                             | (Section 28.7)       |
    +------------+-----------------------------+----------------------+

Lhomme, et al.          Expires 13 February 2024              [Page 139]
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    |       0xCD | FrameNumber                 | Reclaimed            |
    |            |                             | (Section 28.8)       |
    +------------+-----------------------------+----------------------+
    |       0xCE | Delay                       | Reclaimed            |
    |            |                             | (Section 28.10)      |
    +------------+-----------------------------+----------------------+
    |       0xCF | SliceDuration               | Reclaimed            |
    |            |                             | (Section 28.11)      |
    +------------+-----------------------------+----------------------+
    |       0xD7 | TrackNumber                 | Described in         |
    |            |                             | Section 5.1.4.1.1    |
    +------------+-----------------------------+----------------------+
    |       0xDB | CueReference                | Described in         |
    |            |                             | Section 5.1.5.1.2.7  |
    +------------+-----------------------------+----------------------+
    |       0xE0 | Video                       | Described in         |
    |            |                             | Section 5.1.4.1.28   |
    +------------+-----------------------------+----------------------+
    |       0xE1 | Audio                       | Described in         |
    |            |                             | Section 5.1.4.1.29   |
    +------------+-----------------------------+----------------------+
    |       0xE2 | TrackOperation              | Described in         |
    |            |                             | Section 5.1.4.1.30   |
    +------------+-----------------------------+----------------------+
    |       0xE3 | TrackCombinePlanes          | Described in         |
    |            |                             | Section 5.1.4.1.30.1 |
    +------------+-----------------------------+----------------------+
    |       0xE4 | TrackPlane                  | Described in         |
    |            |                             | Section 5.1.4.1.30.2 |
    +------------+-----------------------------+----------------------+
    |       0xE5 | TrackPlaneUID               | Described in         |
    |            |                             | Section 5.1.4.1.30.3 |
    +------------+-----------------------------+----------------------+
    |       0xE6 | TrackPlaneType              | Described in         |
    |            |                             | Section 5.1.4.1.30.4 |
    +------------+-----------------------------+----------------------+
    |       0xE7 | Timestamp                   | Described in         |
    |            |                             | Section 5.1.3.1      |
    +------------+-----------------------------+----------------------+
    |       0xE8 | TimeSlice                   | Reclaimed            |
    |            |                             | (Section 28.6)       |
    +------------+-----------------------------+----------------------+
    |       0xE9 | TrackJoinBlocks             | Described in         |
    |            |                             | Section 5.1.4.1.30.5 |
    +------------+-----------------------------+----------------------+
    |       0xEA | CueCodecState               | Described in         |
    |            |                             | Section 5.1.5.1.2.6  |
    +------------+-----------------------------+----------------------+

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    |       0xEB | CueRefCodecState            | Reclaimed            |
    |            |                             | (Section 28.39)      |
    +------------+-----------------------------+----------------------+
    |       0xED | TrackJoinUID                | Described in         |
    |            |                             | Section 5.1.4.1.30.6 |
    +------------+-----------------------------+----------------------+
    |       0xEE | BlockAddID                  | Described in         |
    |            |                             | Section 5.1.3.5.2.3  |
    +------------+-----------------------------+----------------------+
    |       0xF0 | CueRelativePosition         | Described in         |
    |            |                             | Section 5.1.5.1.2.3  |
    +------------+-----------------------------+----------------------+
    |       0xF1 | CueClusterPosition          | Described in         |
    |            |                             | Section 5.1.5.1.2.2  |
    +------------+-----------------------------+----------------------+
    |       0xF7 | CueTrack                    | Described in         |
    |            |                             | Section 5.1.5.1.2.1  |
    +------------+-----------------------------+----------------------+
    |       0xFA | ReferencePriority           | Described in         |
    |            |                             | Section 5.1.3.5.4    |
    +------------+-----------------------------+----------------------+
    |       0xFB | ReferenceBlock              | Described in         |
    |            |                             | Section 5.1.3.5.5    |
    +------------+-----------------------------+----------------------+
    |       0xFD | ReferenceVirtual            | Reclaimed            |
    |            |                             | (Section 28.4)       |
    +------------+-----------------------------+----------------------+
    |     0x41A4 | BlockAddIDName              | Described in         |
    |            |                             | Section 5.1.4.1.17.2 |
    +------------+-----------------------------+----------------------+
    |     0x41E4 | BlockAdditionMapping        | Described in         |
    |            |                             | Section 5.1.4.1.17   |
    +------------+-----------------------------+----------------------+
    |     0x41E7 | BlockAddIDType              | Described in         |
    |            |                             | Section 5.1.4.1.17.3 |
    +------------+-----------------------------+----------------------+
    |     0x41ED | BlockAddIDExtraData         | Described in         |
    |            |                             | Section 5.1.4.1.17.4 |
    +------------+-----------------------------+----------------------+
    |     0x41F0 | BlockAddIDValue             | Described in         |
    |            |                             | Section 5.1.4.1.17.1 |
    +------------+-----------------------------+----------------------+
    |     0x4254 | ContentCompAlgo             | Described in         |
    |            |                             | Section 5.1.4.1.31.6 |
    +------------+-----------------------------+----------------------+
    |     0x4255 | ContentCompSettings         | Described in         |
    |            |                             | Section 5.1.4.1.31.7 |
    +------------+-----------------------------+----------------------+

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    |     0x437C | ChapLanguage                | Described in         |
    |            |                             | Section 5.1.7.1.4.11 |
    +------------+-----------------------------+----------------------+
    |     0x437D | ChapLanguageBCP47           | Described in         |
    |            |                             | Section 5.1.7.1.4.12 |
    +------------+-----------------------------+----------------------+
    |     0x437E | ChapCountry                 | Described in         |
    |            |                             | Section 5.1.7.1.4.13 |
    +------------+-----------------------------+----------------------+
    |     0x4444 | SegmentFamily               | Described in         |
    |            |                             | Section 5.1.2.7      |
    +------------+-----------------------------+----------------------+
    |     0x4461 | DateUTC                     | Described in         |
    |            |                             | Section 5.1.2.11     |
    +------------+-----------------------------+----------------------+
    |     0x447A | TagLanguage                 | Described in         |
    |            |                             | Section 5.1.8.1.2.2  |
    +------------+-----------------------------+----------------------+
    |     0x447B | TagLanguageBCP47            | Described in         |
    |            |                             | Section 5.1.8.1.2.3  |
    +------------+-----------------------------+----------------------+
    |     0x4484 | TagDefault                  | Described in         |
    |            |                             | Section 5.1.8.1.2.4  |
    +------------+-----------------------------+----------------------+
    |     0x4485 | TagBinary                   | Described in         |
    |            |                             | Section 5.1.8.1.2.6  |
    +------------+-----------------------------+----------------------+
    |     0x4487 | TagString                   | Described in         |
    |            |                             | Section 5.1.8.1.2.5  |
    +------------+-----------------------------+----------------------+
    |     0x4489 | Duration                    | Described in         |
    |            |                             | Section 5.1.2.10     |
    +------------+-----------------------------+----------------------+
    |     0x44B4 | TagDefaultBogus             | Reclaimed            |
    |            |                             | (Section 28.43)      |
    +------------+-----------------------------+----------------------+
    |     0x450D | ChapProcessPrivate          | Described in         |
    |            |                             | Section 5.1.7.1.4.16 |
    +------------+-----------------------------+----------------------+
    |     0x45A3 | TagName                     | Described in         |
    |            |                             | Section 5.1.8.1.2.1  |
    +------------+-----------------------------+----------------------+
    |     0x45B9 | EditionEntry                | Described in         |
    |            |                             | Section 5.1.7.1      |
    +------------+-----------------------------+----------------------+
    |     0x45BC | EditionUID                  | Described in         |
    |            |                             | Section 5.1.7.1.1    |
    +------------+-----------------------------+----------------------+

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    |     0x45DB | EditionFlagDefault          | Described in         |
    |            |                             | Section 5.1.7.1.2    |
    +------------+-----------------------------+----------------------+
    |     0x45DD | EditionFlagOrdered          | Described in         |
    |            |                             | Section 5.1.7.1.3    |
    +------------+-----------------------------+----------------------+
    |     0x465C | FileData                    | Described in         |
    |            |                             | Section 5.1.6.1.4    |
    +------------+-----------------------------+----------------------+
    |     0x4660 | FileMediaType               | Described in         |
    |            |                             | Section 5.1.6.1.3    |
    +------------+-----------------------------+----------------------+
    |     0x4661 | FileUsedStartTime           | Reclaimed            |
    |            |                             | (Section 28.41)      |
    +------------+-----------------------------+----------------------+
    |     0x4662 | FileUsedEndTime             | Reclaimed            |
    |            |                             | (Section 28.42)      |
    +------------+-----------------------------+----------------------+
    |     0x466E | FileName                    | Described in         |
    |            |                             | Section 5.1.6.1.2    |
    +------------+-----------------------------+----------------------+
    |     0x4675 | FileReferral                | Reclaimed            |
    |            |                             | (Section 28.40)      |
    +------------+-----------------------------+----------------------+
    |     0x467E | FileDescription             | Described in         |
    |            |                             | Section 5.1.6.1.1    |
    +------------+-----------------------------+----------------------+
    |     0x46AE | FileUID                     | Described in         |
    |            |                             | Section 5.1.6.1.5    |
    +------------+-----------------------------+----------------------+
    |     0x47E1 | ContentEncAlgo              | Described in         |
    |            |                             | Section 5.1.4.1.31.9 |
    +------------+-----------------------------+----------------------+
    |     0x47E2 | ContentEncKeyID             | Described in Section |
    |            |                             | 5.1.4.1.31.10        |
    +------------+-----------------------------+----------------------+
    |     0x47E3 | ContentSignature            | Reclaimed            |
    |            |                             | (Section 28.33)      |
    +------------+-----------------------------+----------------------+
    |     0x47E4 | ContentSigKeyID             | Reclaimed            |
    |            |                             | (Section 28.34)      |
    +------------+-----------------------------+----------------------+
    |     0x47E5 | ContentSigAlgo              | Reclaimed            |
    |            |                             | (Section 28.35)      |
    +------------+-----------------------------+----------------------+
    |     0x47E6 | ContentSigHashAlgo          | Reclaimed            |
    |            |                             | (Section 28.36)      |
    +------------+-----------------------------+----------------------+

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    |     0x47E7 | ContentEncAESSettings       | Described in Section |
    |            |                             | 5.1.4.1.31.11        |
    +------------+-----------------------------+----------------------+
    |     0x47E8 | AESSettingsCipherMode       | Described in Section |
    |            |                             | 5.1.4.1.31.12        |
    +------------+-----------------------------+----------------------+
    |     0x4D80 | MuxingApp                   | Described in         |
    |            |                             | Section 5.1.2.13     |
    +------------+-----------------------------+----------------------+
    |     0x4DBB | Seek                        | Described in         |
    |            |                             | Section 5.1.1.1      |
    +------------+-----------------------------+----------------------+
    |     0x5031 | ContentEncodingOrder        | Described in         |
    |            |                             | Section 5.1.4.1.31.2 |
    +------------+-----------------------------+----------------------+
    |     0x5032 | ContentEncodingScope        | Described in         |
    |            |                             | Section 5.1.4.1.31.3 |
    +------------+-----------------------------+----------------------+
    |     0x5033 | ContentEncodingType         | Described in         |
    |            |                             | Section 5.1.4.1.31.4 |
    +------------+-----------------------------+----------------------+
    |     0x5034 | ContentCompression          | Described in         |
    |            |                             | Section 5.1.4.1.31.5 |
    +------------+-----------------------------+----------------------+
    |     0x5035 | ContentEncryption           | Described in         |
    |            |                             | Section 5.1.4.1.31.8 |
    +------------+-----------------------------+----------------------+
    |     0x535F | CueRefNumber                | Reclaimed            |
    |            |                             | (Section 28.38)      |
    +------------+-----------------------------+----------------------+
    |     0x536E | Name                        | Described in         |
    |            |                             | Section 5.1.4.1.18   |
    +------------+-----------------------------+----------------------+
    |     0x5378 | CueBlockNumber              | Described in         |
    |            |                             | Section 5.1.5.1.2.5  |
    +------------+-----------------------------+----------------------+
    |     0x537F | TrackOffset                 | Reclaimed            |
    |            |                             | (Section 28.18)      |
    +------------+-----------------------------+----------------------+
    |     0x53AB | SeekID                      | Described in         |
    |            |                             | Section 5.1.1.1.1    |
    +------------+-----------------------------+----------------------+
    |     0x53AC | SeekPosition                | Described in         |
    |            |                             | Section 5.1.1.1.2    |
    +------------+-----------------------------+----------------------+
    |     0x53B8 | StereoMode                  | Described in         |
    |            |                             | Section 5.1.4.1.28.3 |
    +------------+-----------------------------+----------------------+

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    |     0x53B9 | OldStereoMode               | Described in         |
    |            |                             | Section 5.1.4.1.28.5 |
    +------------+-----------------------------+----------------------+
    |     0x53C0 | AlphaMode                   | Described in         |
    |            |                             | Section 5.1.4.1.28.4 |
    +------------+-----------------------------+----------------------+
    |     0x54AA | PixelCropBottom             | Described in         |
    |            |                             | Section 5.1.4.1.28.8 |
    +------------+-----------------------------+----------------------+
    |     0x54B0 | DisplayWidth                | Described in Section |
    |            |                             | 5.1.4.1.28.12        |
    +------------+-----------------------------+----------------------+
    |     0x54B2 | DisplayUnit                 | Described in Section |
    |            |                             | 5.1.4.1.28.14        |
    +------------+-----------------------------+----------------------+
    |     0x54B3 | AspectRatioType             | Reclaimed            |
    |            |                             | (Section 28.24)      |
    +------------+-----------------------------+----------------------+
    |     0x54BA | DisplayHeight               | Described in Section |
    |            |                             | 5.1.4.1.28.13        |
    +------------+-----------------------------+----------------------+
    |     0x54BB | PixelCropTop                | Described in         |
    |            |                             | Section 5.1.4.1.28.9 |
    +------------+-----------------------------+----------------------+
    |     0x54CC | PixelCropLeft               | Described in Section |
    |            |                             | 5.1.4.1.28.10        |
    +------------+-----------------------------+----------------------+
    |     0x54DD | PixelCropRight              | Described in Section |
    |            |                             | 5.1.4.1.28.11        |
    +------------+-----------------------------+----------------------+
    |     0x55AA | FlagForced                  | Described in         |
    |            |                             | Section 5.1.4.1.6    |
    +------------+-----------------------------+----------------------+
    |     0x55AB | FlagHearingImpaired         | Described in         |
    |            |                             | Section 5.1.4.1.7    |
    +------------+-----------------------------+----------------------+
    |     0x55AC | FlagVisualImpaired          | Described in         |
    |            |                             | Section 5.1.4.1.8    |
    +------------+-----------------------------+----------------------+
    |     0x55AD | FlagTextDescriptions        | Described in         |
    |            |                             | Section 5.1.4.1.9    |
    +------------+-----------------------------+----------------------+
    |     0x55AE | FlagOriginal                | Described in         |
    |            |                             | Section 5.1.4.1.10   |
    +------------+-----------------------------+----------------------+
    |     0x55AF | FlagCommentary              | Described in         |
    |            |                             | Section 5.1.4.1.11   |
    +------------+-----------------------------+----------------------+

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    |     0x55B0 | Colour                      | Described in Section |
    |            |                             | 5.1.4.1.28.16        |
    +------------+-----------------------------+----------------------+
    |     0x55B1 | MatrixCoefficients          | Described in Section |
    |            |                             | 5.1.4.1.28.17        |
    +------------+-----------------------------+----------------------+
    |     0x55B2 | BitsPerChannel              | Described in Section |
    |            |                             | 5.1.4.1.28.18        |
    +------------+-----------------------------+----------------------+
    |     0x55B3 | ChromaSubsamplingHorz       | Described in Section |
    |            |                             | 5.1.4.1.28.19        |
    +------------+-----------------------------+----------------------+
    |     0x55B4 | ChromaSubsamplingVert       | Described in Section |
    |            |                             | 5.1.4.1.28.20        |
    +------------+-----------------------------+----------------------+
    |     0x55B5 | CbSubsamplingHorz           | Described in Section |
    |            |                             | 5.1.4.1.28.21        |
    +------------+-----------------------------+----------------------+
    |     0x55B6 | CbSubsamplingVert           | Described in Section |
    |            |                             | 5.1.4.1.28.22        |
    +------------+-----------------------------+----------------------+
    |     0x55B7 | ChromaSitingHorz            | Described in Section |
    |            |                             | 5.1.4.1.28.23        |
    +------------+-----------------------------+----------------------+
    |     0x55B8 | ChromaSitingVert            | Described in Section |
    |            |                             | 5.1.4.1.28.24        |
    +------------+-----------------------------+----------------------+
    |     0x55B9 | Range                       | Described in Section |
    |            |                             | 5.1.4.1.28.25        |
    +------------+-----------------------------+----------------------+
    |     0x55BA | TransferCharacteristics     | Described in Section |
    |            |                             | 5.1.4.1.28.26        |
    +------------+-----------------------------+----------------------+
    |     0x55BB | Primaries                   | Described in Section |
    |            |                             | 5.1.4.1.28.27        |
    +------------+-----------------------------+----------------------+
    |     0x55BC | MaxCLL                      | Described in Section |
    |            |                             | 5.1.4.1.28.28        |
    +------------+-----------------------------+----------------------+
    |     0x55BD | MaxFALL                     | Described in Section |
    |            |                             | 5.1.4.1.28.29        |
    +------------+-----------------------------+----------------------+
    |     0x55D0 | MasteringMetadata           | Described in Section |
    |            |                             | 5.1.4.1.28.30        |
    +------------+-----------------------------+----------------------+
    |     0x55D1 | PrimaryRChromaticityX       | Described in Section |
    |            |                             | 5.1.4.1.28.31        |
    +------------+-----------------------------+----------------------+

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    |     0x55D2 | PrimaryRChromaticityY       | Described in Section |
    |            |                             | 5.1.4.1.28.32        |
    +------------+-----------------------------+----------------------+
    |     0x55D3 | PrimaryGChromaticityX       | Described in Section |
    |            |                             | 5.1.4.1.28.33        |
    +------------+-----------------------------+----------------------+
    |     0x55D4 | PrimaryGChromaticityY       | Described in Section |
    |            |                             | 5.1.4.1.28.34        |
    +------------+-----------------------------+----------------------+
    |     0x55D5 | PrimaryBChromaticityX       | Described in Section |
    |            |                             | 5.1.4.1.28.35        |
    +------------+-----------------------------+----------------------+
    |     0x55D6 | PrimaryBChromaticityY       | Described in Section |
    |            |                             | 5.1.4.1.28.36        |
    +------------+-----------------------------+----------------------+
    |     0x55D7 | WhitePointChromaticityX     | Described in Section |
    |            |                             | 5.1.4.1.28.37        |
    +------------+-----------------------------+----------------------+
    |     0x55D8 | WhitePointChromaticityY     | Described in Section |
    |            |                             | 5.1.4.1.28.38        |
    +------------+-----------------------------+----------------------+
    |     0x55D9 | LuminanceMax                | Described in Section |
    |            |                             | 5.1.4.1.28.39        |
    +------------+-----------------------------+----------------------+
    |     0x55DA | LuminanceMin                | Described in Section |
    |            |                             | 5.1.4.1.28.40        |
    +------------+-----------------------------+----------------------+
    |     0x55EE | MaxBlockAdditionID          | Described in         |
    |            |                             | Section 5.1.4.1.16   |
    +------------+-----------------------------+----------------------+
    |     0x5654 | ChapterStringUID            | Described in         |
    |            |                             | Section 5.1.7.1.4.2  |
    +------------+-----------------------------+----------------------+
    |     0x56AA | CodecDelay                  | Described in         |
    |            |                             | Section 5.1.4.1.25   |
    +------------+-----------------------------+----------------------+
    |     0x56BB | SeekPreRoll                 | Described in         |
    |            |                             | Section 5.1.4.1.26   |
    +------------+-----------------------------+----------------------+
    |     0x5741 | WritingApp                  | Described in         |
    |            |                             | Section 5.1.2.14     |
    +------------+-----------------------------+----------------------+
    |     0x5854 | SilentTracks                | Reclaimed            |
    |            |                             | (Section 28.1)       |
    +------------+-----------------------------+----------------------+
    |     0x58D7 | SilentTrackNumber           | Reclaimed            |
    |            |                             | (Section 28.2)       |
    +------------+-----------------------------+----------------------+

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    |     0x61A7 | AttachedFile                | Described in         |
    |            |                             | Section 5.1.6.1      |
    +------------+-----------------------------+----------------------+
    |     0x6240 | ContentEncoding             | Described in         |
    |            |                             | Section 5.1.4.1.31.1 |
    +------------+-----------------------------+----------------------+
    |     0x6264 | BitDepth                    | Described in         |
    |            |                             | Section 5.1.4.1.29.4 |
    +------------+-----------------------------+----------------------+
    |     0x63A2 | CodecPrivate                | Described in         |
    |            |                             | Section 5.1.4.1.22   |
    +------------+-----------------------------+----------------------+
    |     0x63C0 | Targets                     | Described in         |
    |            |                             | Section 5.1.8.1.1    |
    +------------+-----------------------------+----------------------+
    |     0x63C3 | ChapterPhysicalEquiv        | Described in         |
    |            |                             | Section 5.1.7.1.4.8  |
    +------------+-----------------------------+----------------------+
    |     0x63C4 | TagChapterUID               | Described in         |
    |            |                             | Section 5.1.8.1.1.5  |
    +------------+-----------------------------+----------------------+
    |     0x63C5 | TagTrackUID                 | Described in         |
    |            |                             | Section 5.1.8.1.1.3  |
    +------------+-----------------------------+----------------------+
    |     0x63C6 | TagAttachmentUID            | Described in         |
    |            |                             | Section 5.1.8.1.1.6  |
    +------------+-----------------------------+----------------------+
    |     0x63C9 | TagEditionUID               | Described in         |
    |            |                             | Section 5.1.8.1.1.4  |
    +------------+-----------------------------+----------------------+
    |     0x63CA | TargetType                  | Described in         |
    |            |                             | Section 5.1.8.1.1.2  |
    +------------+-----------------------------+----------------------+
    |     0x6624 | TrackTranslate              | Described in         |
    |            |                             | Section 5.1.4.1.27   |
    +------------+-----------------------------+----------------------+
    |     0x66A5 | TrackTranslateTrackID       | Described in         |
    |            |                             | Section 5.1.4.1.27.1 |
    +------------+-----------------------------+----------------------+
    |     0x66BF | TrackTranslateCodec         | Described in         |
    |            |                             | Section 5.1.4.1.27.2 |
    +------------+-----------------------------+----------------------+
    |     0x66FC | TrackTranslateEditionUID    | Described in         |
    |            |                             | Section 5.1.4.1.27.3 |
    +------------+-----------------------------+----------------------+
    |     0x67C8 | SimpleTag                   | Described in         |
    |            |                             | Section 5.1.8.1.2    |
    +------------+-----------------------------+----------------------+

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    |     0x68CA | TargetTypeValue             | Described in         |
    |            |                             | Section 5.1.8.1.1.1  |
    +------------+-----------------------------+----------------------+
    |     0x6911 | ChapProcessCommand          | Described in         |
    |            |                             | Section 5.1.7.1.4.17 |
    +------------+-----------------------------+----------------------+
    |     0x6922 | ChapProcessTime             | Described in         |
    |            |                             | Section 5.1.7.1.4.18 |
    +------------+-----------------------------+----------------------+
    |     0x6924 | ChapterTranslate            | Described in         |
    |            |                             | Section 5.1.2.8      |
    +------------+-----------------------------+----------------------+
    |     0x6933 | ChapProcessData             | Described in         |
    |            |                             | Section 5.1.7.1.4.19 |
    +------------+-----------------------------+----------------------+
    |     0x6944 | ChapProcess                 | Described in         |
    |            |                             | Section 5.1.7.1.4.14 |
    +------------+-----------------------------+----------------------+
    |     0x6955 | ChapProcessCodecID          | Described in         |
    |            |                             | Section 5.1.7.1.4.15 |
    +------------+-----------------------------+----------------------+
    |     0x69A5 | ChapterTranslateID          | Described in         |
    |            |                             | Section 5.1.2.8.1    |
    +------------+-----------------------------+----------------------+
    |     0x69BF | ChapterTranslateCodec       | Described in         |
    |            |                             | Section 5.1.2.8.2    |
    +------------+-----------------------------+----------------------+
    |     0x69FC | ChapterTranslateEditionUID  | Described in         |
    |            |                             | Section 5.1.2.8.3    |
    +------------+-----------------------------+----------------------+
    |     0x6D80 | ContentEncodings            | Described in         |
    |            |                             | Section 5.1.4.1.31   |
    +------------+-----------------------------+----------------------+
    |     0x6DE7 | MinCache                    | Reclaimed            |
    |            |                             | (Section 28.16)      |
    +------------+-----------------------------+----------------------+
    |     0x6DF8 | MaxCache                    | Reclaimed            |
    |            |                             | (Section 28.17)      |
    +------------+-----------------------------+----------------------+
    |     0x6E67 | ChapterSegmentUUID          | Described in         |
    |            |                             | Section 5.1.7.1.4.6  |
    +------------+-----------------------------+----------------------+
    |     0x6EBC | ChapterSegmentEditionUID    | Described in         |
    |            |                             | Section 5.1.7.1.4.7  |
    +------------+-----------------------------+----------------------+
    |     0x6FAB | TrackOverlay                | Reclaimed            |
    |            |                             | (Section 28.23)      |
    +------------+-----------------------------+----------------------+

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    |     0x7373 | Tag                         | Described in         |
    |            |                             | Section 5.1.8.1      |
    +------------+-----------------------------+----------------------+
    |     0x7384 | SegmentFilename             | Described in         |
    |            |                             | Section 5.1.2.2      |
    +------------+-----------------------------+----------------------+
    |     0x73A4 | SegmentUUID                 | Described in         |
    |            |                             | Section 5.1.2.1      |
    +------------+-----------------------------+----------------------+
    |     0x73C4 | ChapterUID                  | Described in         |
    |            |                             | Section 5.1.7.1.4.1  |
    +------------+-----------------------------+----------------------+
    |     0x73C5 | TrackUID                    | Described in         |
    |            |                             | Section 5.1.4.1.2    |
    +------------+-----------------------------+----------------------+
    |     0x7446 | AttachmentLink              | Described in         |
    |            |                             | Section 5.1.4.1.24   |
    +------------+-----------------------------+----------------------+
    |     0x75A1 | BlockAdditions              | Described in         |
    |            |                             | Section 5.1.3.5.2    |
    +------------+-----------------------------+----------------------+
    |     0x75A2 | DiscardPadding              | Described in         |
    |            |                             | Section 5.1.3.5.7    |
    +------------+-----------------------------+----------------------+
    |     0x7670 | Projection                  | Described in Section |
    |            |                             | 5.1.4.1.28.41        |
    +------------+-----------------------------+----------------------+
    |     0x7671 | ProjectionType              | Described in Section |
    |            |                             | 5.1.4.1.28.42        |
    +------------+-----------------------------+----------------------+
    |     0x7672 | ProjectionPrivate           | Described in Section |
    |            |                             | 5.1.4.1.28.43        |
    +------------+-----------------------------+----------------------+
    |     0x7673 | ProjectionPoseYaw           | Described in Section |
    |            |                             | 5.1.4.1.28.44        |
    +------------+-----------------------------+----------------------+
    |     0x7674 | ProjectionPosePitch         | Described in Section |
    |            |                             | 5.1.4.1.28.45        |
    +------------+-----------------------------+----------------------+
    |     0x7675 | ProjectionPoseRoll          | Described in Section |
    |            |                             | 5.1.4.1.28.46        |
    +------------+-----------------------------+----------------------+
    |     0x78B5 | OutputSamplingFrequency     | Described in         |
    |            |                             | Section 5.1.4.1.29.2 |
    +------------+-----------------------------+----------------------+
    |     0x7BA9 | Title                       | Described in         |
    |            |                             | Section 5.1.2.12     |
    +------------+-----------------------------+----------------------+

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    |     0x7D7B | ChannelPositions            | Reclaimed            |
    |            |                             | (Section 28.27)      |
    +------------+-----------------------------+----------------------+
    |   0x22B59C | Language                    | Described in         |
    |            |                             | Section 5.1.4.1.19   |
    +------------+-----------------------------+----------------------+
    |   0x22B59D | LanguageBCP47               | Described in         |
    |            |                             | Section 5.1.4.1.20   |
    +------------+-----------------------------+----------------------+
    |   0x23314F | TrackTimestampScale         | Described in         |
    |            |                             | Section 5.1.4.1.15   |
    +------------+-----------------------------+----------------------+
    |   0x234E7A | DefaultDecodedFieldDuration | Described in         |
    |            |                             | Section 5.1.4.1.14   |
    +------------+-----------------------------+----------------------+
    |   0x2383E3 | FrameRate                   | Reclaimed            |
    |            |                             | (Section 28.26)      |
    +------------+-----------------------------+----------------------+
    |   0x23E383 | DefaultDuration             | Described in         |
    |            |                             | Section 5.1.4.1.13   |
    +------------+-----------------------------+----------------------+
    |   0x258688 | CodecName                   | Described in         |
    |            |                             | Section 5.1.4.1.23   |
    +------------+-----------------------------+----------------------+
    |   0x26B240 | CodecDownloadURL            | Reclaimed            |
    |            |                             | (Section 28.21)      |
    +------------+-----------------------------+----------------------+
    |   0x2AD7B1 | TimestampScale              | Described in         |
    |            |                             | Section 5.1.2.9      |
    +------------+-----------------------------+----------------------+
    |   0x2EB524 | UncompressedFourCC          | Described in Section |
    |            |                             | 5.1.4.1.28.15        |
    +------------+-----------------------------+----------------------+
    |   0x2FB523 | GammaValue                  | Reclaimed            |
    |            |                             | (Section 28.25)      |
    +------------+-----------------------------+----------------------+
    |   0x3A9697 | CodecSettings               | Reclaimed            |
    |            |                             | (Section 28.19)      |
    +------------+-----------------------------+----------------------+
    |   0x3B4040 | CodecInfoURL                | Reclaimed            |
    |            |                             | (Section 28.20)      |
    +------------+-----------------------------+----------------------+
    |   0x3C83AB | PrevFilename                | Described in         |
    |            |                             | Section 5.1.2.4      |
    +------------+-----------------------------+----------------------+
    |   0x3CB923 | PrevUUID                    | Described in         |
    |            |                             | Section 5.1.2.3      |
    +------------+-----------------------------+----------------------+

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    |   0x3E83BB | NextFilename                | Described in         |
    |            |                             | Section 5.1.2.6      |
    +------------+-----------------------------+----------------------+
    |   0x3EB923 | NextUUID                    | Described in         |
    |            |                             | Section 5.1.2.5      |
    +------------+-----------------------------+----------------------+
    | 0x1043A770 | Chapters                    | Described in         |
    |            |                             | Section 5.1.7        |
    +------------+-----------------------------+----------------------+
    | 0x114D9B74 | SeekHead                    | Described in         |
    |            |                             | Section 5.1.1        |
    +------------+-----------------------------+----------------------+
    | 0x1254C367 | Tags                        | Described in         |
    |            |                             | Section 5.1.8        |
    +------------+-----------------------------+----------------------+
    | 0x1549A966 | Info                        | Described in         |
    |            |                             | Section 5.1.2        |
    +------------+-----------------------------+----------------------+
    | 0x1654AE6B | Tracks                      | Described in         |
    |            |                             | Section 5.1.4        |
    +------------+-----------------------------+----------------------+
    | 0x18538067 | Segment                     | Described in         |
    |            |                             | Section 5.1          |
    +------------+-----------------------------+----------------------+
    | 0x1941A469 | Attachments                 | Described in         |
    |            |                             | Section 5.1.6        |
    +------------+-----------------------------+----------------------+
    | 0x1C53BB6B | Cues                        | Described in         |
    |            |                             | Section 5.1.5        |
    +------------+-----------------------------+----------------------+
    | 0x1F43B675 | Cluster                     | Described in         |
    |            |                             | Section 5.1.3        |
    +------------+-----------------------------+----------------------+

        Table 55: IDs and Names for Matroska Element IDs assigned by
                               this document

27.2.  Chapter Codec IDs Registry

   This document creates a new IANA registry called the "Matroska
   Chapter Codec IDs" registry.  The values correspond to the unsigned
   integer ChapProcessCodecID value described in Section 5.1.7.1.4.15.

   To register a new Chapter Codec ID in this registry, one needs a
   Chapter Codec ID, a Change Controller (IETF or email of registrant)
   and an optional Reference to a document describing the Chapter Codec
   ID.

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   The Chapter Codec IDs are to be allocated according to the "First
   Come First Served" policy [RFC8126].

   ChapProcessCodecID values of "0" and "1" are RESERVED to the IETF for
   future use.

27.3.  Media Types

   Matroska files and streams are found in three main forms: audio-video
   files, audio-only and occasionally with stereoscopic video tracks.

   Historically Matroska files and streams have used the following media
   types with a "x-" prefix.  For better compatibility a system SHOULD
   be able to handle both formats.  Newer systems SHOULD NOT use the
   historic format and use the format that follows the [RFC6838] format
   instead.

   Please register three media types, the [RFC6838] templates are below:

27.3.1.  For files containing video tracks

   Type name:  video
   Subtype name:  matroska
   Required parameters:  N/A
   Optional parameters:  N/A
   Encoding considerations:  as per this document and RFC8794
   Security considerations:  See Section 26.
   Interoperability considerations:  Due to the extensibility of
      Matroska, it is possible to encounter files with unknown but valid
      EBML Elements.  Readers should be ready to handle this case.  The
      fixed byte order, octet boundaries and UTF-8 usage allow for broad
      interoparability.
   Published specification:  THISRFC
   Applications that use this media type:  FFmpeg, VLC, ...
   Fragment identifier considerations:  N/A

   Additional information:

   *  Deprecated alias names for this type: video/x-matroska

   *  Magic number(s): N/A

   *  File extension(s): mkv

   *  Macintosh file type code(s): N/A

   Person & email address to contact for further information:  IETF
      CELLAR WG cellar@ietf.org

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   Intended usage:  COMMON
   Restrictions on usage:  None
   Author:  IETF CELLAR WG
   Change controller:  IETF
   Provisional registration? (standards tree only):  No

27.3.2.  For files containing audio tracks with no video tracks

   Type name:  audio
   Subtype name:  matroska
   Required parameters:  N/A
   Optional parameters:  N/A
   Encoding considerations:  as per this document and RFC8794
   Security considerations:  See Section 26.
   Interoperability considerations:  Due to the extensibility of
      Matroska, it is possible to encounter files with unknown but valid
      EBML Elements.  Readers should be ready to handle this case.  The
      fixed byte order, octet boundaries and UTF-8 usage allow for broad
      interoparability.
   Published specification:  THISRFC
   Applications that use this media type:  FFmpeg, VLC, ...
   Fragment identifier considerations:  N/A

   Additional information:

   *  Deprecated alias names for this type: audio/x-matroska

   *  Magic number(s): N/A

   *  File extension(s): mka

   *  Macintosh file type code(s): N/A

   Person & email address to contact for further information:  IETF
      CELLAR WG cellar@ietf.org
   Intended usage:  COMMON
   Restrictions on usage:  None
   Author:  IETF CELLAR WG
   Change controller:  IETF
   Provisional registration? (standards tree only):  No

27.3.3.  For files containing a stereoscopic video track

   Type name:  video
   Subtype name:  matroska-3d
   Required parameters:  N/A
   Optional parameters:  N/A
   Encoding considerations:  as per this document and RFC8794

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   Security considerations:  See Section 26.
   Interoperability considerations:  Due to the extensibility of
      Matroska, it is possible to encounter files with unknown but valid
      EBML Elements.  Readers should be ready to handle this case.  The
      fixed byte order, octet boundaries and UTF-8 usage allow for broad
      interoparability.
   Published specification:  THISRFC
   Applications that use this media type:  FFmpeg, VLC, ...
   Fragment identifier considerations:  N/A

   Additional information:

   *  Deprecated alias names for this type: video/x-matroska-3d

   *  Magic number(s): N/A

   *  File extension(s): mk3d

   *  Macintosh file type code(s): N/A

   Person & email address to contact for further information:  IETF
      CELLAR WG cellar@ietf.org
   Intended usage:  COMMON
   Restrictions on usage:  None
   Author:  IETF CELLAR WG
   Change controller:  IETF
   Provisional registration? (standards tree only):  No

28.  Annex A: Historic Deprecated Elements

   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.

   We list these elements that have a known ID that SHOULD NOT be reused
   to avoid colliding with existing files.  They might be reassigned by
   IANA in the future if there are no more IDs for a given size.  A
   short description of what each ID was used for is included, but the
   text is not normative.

28.1.  SilentTracks Element

   type / id:  master / 0x5854
   path:  \Segment\Cluster\SilentTracks
   documentation:  The list of tracks that are not used in that part of

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      the stream.  It is useful when using overlay tracks on seeking or
      to decide what track to use.

28.2.  SilentTrackNumber Element

   type / id:  uinteger / 0x58D7
   path:  \Segment\Cluster\SilentTracks\SilentTrackNumber
   documentation:  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.

28.3.  BlockVirtual Element

   type / id:  binary / 0xA2
   path:  \Segment\Cluster\BlockGroup\BlockVirtual
   documentation:  A Block with no data.  It must be stored in the
      stream at the place the real Block would be in display order.

28.4.  ReferenceVirtual Element

   type / id:  integer / 0xFD
   path:  \Segment\Cluster\BlockGroup\ReferenceVirtual
   documentation:  The Segment Position of the data that would otherwise
      be in position of the virtual block.

28.5.  Slices Element

   type / id:  master / 0x8E
   path:  \Segment\Cluster\BlockGroup\Slices
   documentation:  Contains slices description.

28.6.  TimeSlice Element

   type / id:  master / 0xE8
   path:  \Segment\Cluster\BlockGroup\Slices\TimeSlice
   documentation:  Contains extra time information about the data
      contained in the Block.  Being able to interpret this Element is
      not required for playback.

28.7.  LaceNumber Element

   type / id:  uinteger / 0xCC
   path:  \Segment\Cluster\BlockGroup\Slices\TimeSlice\LaceNumber
   documentation:  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.

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28.8.  FrameNumber Element

   type / id:  uinteger / 0xCD
   path:  \Segment\Cluster\BlockGroup\Slices\TimeSlice\FrameNumber
   documentation:  The number of the frame to generate from this lace
      with this delay (allow you to generate many frames from the same
      Block/Frame).

28.9.  BlockAdditionID Element

   type / id:  uinteger / 0xCB
   path:  \Segment\Cluster\BlockGroup\Slices\TimeSlice\BlockAdditionID
   documentation:  The ID of the BlockAdditional Element (0 is the main
      Block).

28.10.  Delay Element

   type / id:  uinteger / 0xCE
   path:  \Segment\Cluster\BlockGroup\Slices\TimeSlice\Delay
   documentation:  The delay to apply to the Element, expressed in Track
      Ticks; see Section 11.1.

28.11.  SliceDuration Element

   type / id:  uinteger / 0xCF
   path:  \Segment\Cluster\BlockGroup\Slices\TimeSlice\SliceDuration
   documentation:  The duration to apply to the Element, expressed in
      Track Ticks; see Section 11.1.

28.12.  ReferenceFrame Element

   type / id:  master / 0xC8
   path:  \Segment\Cluster\BlockGroup\ReferenceFrame
   documentation:  Contains information about the last reference frame.
      See [DivXTrickTrack].

28.13.  ReferenceOffset Element

   type / id:  uinteger / 0xC9
   path:  \Segment\Cluster\BlockGroup\ReferenceFrame\ReferenceOffset
   documentation:  The relative offset, in bytes, from the previous
      BlockGroup element for this Smooth FF/RW video track to the
      containing BlockGroup element.  See [DivXTrickTrack].

28.14.  ReferenceTimestamp Element

   type / id:  uinteger / 0xCA
   path:  \Segment\Cluster\BlockGroup\ReferenceFrame\ReferenceTimestamp

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   documentation:  The timestamp of the BlockGroup pointed to by
      ReferenceOffset, expressed in Track Ticks; see Section 11.1.  See
      [DivXTrickTrack].

28.15.  EncryptedBlock Element

   type / id:  binary / 0xAF
   path:  \Segment\Cluster\EncryptedBlock
   documentation:  Similar to SimpleBlock, see Section 10.2, but the
      data inside the Block are Transformed (encrypt and/or signed).

28.16.  MinCache Element

   type / id:  uinteger / 0x6DE7
   path:  \Segment\Tracks\TrackEntry\MinCache
   documentation:  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.

28.17.  MaxCache Element

   type / id:  uinteger / 0x6DF8
   path:  \Segment\Tracks\TrackEntry\MaxCache
   documentation:  The maximum cache size necessary to store referenced
      frames in and the current frame. 0 means no cache is needed.

28.18.  TrackOffset Element

   type / id:  integer / 0x537F
   path:  \Segment\Tracks\TrackEntry\TrackOffset
   documentation:  A value to add to the Block's Timestamp, expressed in
      Matroska Ticks -- i.e., in nanoseconds; see Section 11.1.  This
      can be used to adjust the playback offset of a track.

28.19.  CodecSettings Element

   type / id:  utf-8 / 0x3A9697
   path:  \Segment\Tracks\TrackEntry\CodecSettings
   documentation:  A string describing the encoding setting used.

28.20.  CodecInfoURL Element

   type / id:  string / 0x3B4040
   path:  \Segment\Tracks\TrackEntry\CodecInfoURL
   documentation:  A URL to find information about the codec used.

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28.21.  CodecDownloadURL Element

   type / id:  string / 0x26B240
   path:  \Segment\Tracks\TrackEntry\CodecDownloadURL
   documentation:  A URL to download about the codec used.

28.22.  CodecDecodeAll Element

   type / id:  uinteger / 0xAA
   path:  \Segment\Tracks\TrackEntry\CodecDecodeAll
   documentation:  Set to 1 if the codec can decode potentially damaged
      data.

28.23.  TrackOverlay Element

   type / id:  uinteger / 0x6FAB
   path:  \Segment\Tracks\TrackEntry\TrackOverlay
   documentation:  Specify that this track is an overlay track for the
      Track specified (in the u-integer).  That means when this track
      has a gap 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.

28.24.  AspectRatioType Element

   type / id:  uinteger / 0x54B3
   path:  \Segment\Tracks\TrackEntry\Video\AspectRatioType
   documentation:  Specify the possible modifications to the aspect
      ratio.

28.25.  GammaValue Element

   type / id:  float / 0x2FB523
   path:  \Segment\Tracks\TrackEntry\Video\GammaValue
   documentation:  Gamma Value.

28.26.  FrameRate Element

   type / id:  float / 0x2383E3
   path:  \Segment\Tracks\TrackEntry\Video\FrameRate
   documentation:  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.

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28.27.  ChannelPositions Element

   type / id:  binary / 0x7D7B
   path:  \Segment\Tracks\TrackEntry\Audio\ChannelPositions
   documentation:  Table of horizontal angles for each successive
      channel.

28.28.  TrickTrackUID Element

   type / id:  uinteger / 0xC0
   path:  \Segment\Tracks\TrackEntry\TrickTrackUID
   documentation:  The TrackUID of the Smooth FF/RW video in the paired
      EBML structure corresponding to this video track.  See
      [DivXTrickTrack].

28.29.  TrickTrackSegmentUID Element

   type / id:  binary / 0xC1
   path:  \Segment\Tracks\TrackEntry\TrickTrackSegmentUID
   documentation:  The SegmentUID of the Segment containing the track
      identified by TrickTrackUID.  See [DivXTrickTrack].

28.30.  TrickTrackFlag Element

   type / id:  uinteger / 0xC6
   path:  \Segment\Tracks\TrackEntry\TrickTrackFlag
   documentation:  Set to 1 if this video track is a Smooth FF/RW track.
      If set to 1, MasterTrackUID and MasterTrackSegUID should 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].

28.31.  TrickMasterTrackUID Element

   type / id:  uinteger / 0xC7
   path:  \Segment\Tracks\TrackEntry\TrickMasterTrackUID
   documentation:  The TrackUID of the video track in the paired EBML
      structure that corresponds to this Smooth FF/RW track.  See
      [DivXTrickTrack].

28.32.  TrickMasterTrackSegmentUID Element

   type / id:  binary / 0xC4
   path:  \Segment\Tracks\TrackEntry\TrickMasterTrackSegmentUID
   documentation:  The SegmentUID of the Segment containing the track
      identified by MasterTrackUID.  See [DivXTrickTrack].

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28.33.  ContentSignature Element

   type / id:  binary / 0x47E3
   path:  \Segment\Tracks\TrackEntry\ContentEncodings\ContentEncoding\Co
      ntentEncryption\ContentSignature
   documentation:  A cryptographic signature of the contents.

28.34.  ContentSigKeyID Element

   type / id:  binary / 0x47E4
   path:  \Segment\Tracks\TrackEntry\ContentEncodings\ContentEncoding\Co
      ntentEncryption\ContentSigKeyID
   documentation:  This is the ID of the private key the data was signed
      with.

28.35.  ContentSigAlgo Element

   type / id:  uinteger / 0x47E5
   path:  \Segment\Tracks\TrackEntry\ContentEncodings\ContentEncoding\Co
      ntentEncryption\ContentSigAlgo
   documentation:  The algorithm used for the signature.

28.36.  ContentSigHashAlgo Element

   type / id:  uinteger / 0x47E6
   path:  \Segment\Tracks\TrackEntry\ContentEncodings\ContentEncoding\Co
      ntentEncryption\ContentSigHashAlgo
   documentation:  The hash algorithm used for the signature.

28.37.  CueRefCluster Element

   type / id:  uinteger / 0x97
   path:  \Segment\Cues\CuePoint\CueTrackPositions\CueReference\CueRefCl
      uster
   documentation:  The Segment Position of the Cluster containing the
      referenced Block.

28.38.  CueRefNumber Element

   type / id:  uinteger / 0x535F
   path:  \Segment\Cues\CuePoint\CueTrackPositions\CueReference\CueRefNu
      mber
   documentation:  Number of the referenced Block of Track X in the
      specified Cluster.

28.39.  CueRefCodecState Element

   type / id:  uinteger / 0xEB

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   path:  \Segment\Cues\CuePoint\CueTrackPositions\CueReference\CueRefCo
      decState
   documentation:  The Segment Position of the Codec State corresponding
      to this referenced Element. 0 means that the data is taken from
      the initial Track Entry.

28.40.  FileReferral Element

   type / id:  binary / 0x4675
   path:  \Segment\Attachments\AttachedFile\FileReferral
   documentation:  A binary value that a track/codec can refer to when
      the attachment is needed.

28.41.  FileUsedStartTime Element

   type / id:  uinteger / 0x4661
   path:  \Segment\Attachments\AttachedFile\FileUsedStartTime
   documentation:  The timestamp at which this optimized font attachment
      comes into context, expressed in Segment Ticks which is based on
      TimestampScale.  See [DivXWorldFonts].

28.42.  FileUsedEndTime Element

   type / id:  uinteger / 0x4662
   path:  \Segment\Attachments\AttachedFile\FileUsedEndTime
   documentation:  The timestamp at which this optimized font attachment
      goes out of context, expressed in Segment Ticks which is based on
      TimestampScale.  See [DivXWorldFonts].

28.43.  TagDefaultBogus Element

   type / id:  uinteger / 0x44B4
   path:  \Segment\Tags\Tag\+SimpleTag\TagDefaultBogus
   documentation:  A variant of the TagDefault element with a bogus
      Element ID; see Section 5.1.8.1.2.4.

29.  Normative References

   [BCP47]    Phillips, A., Ed. and M. Davis, Ed., "Tags for Identifying
              Languages", BCP 47, RFC 5646, DOI 10.17487/RFC5646,
              September 2009, <https://www.rfc-editor.org/info/rfc5646>.

   [CIE-1931] Commission Internationale de l'Eclairage, "CIE 1931
              Standard Colorimetric System", 1931,
              <https://en.wikipedia.org/wiki/CIE_1931_color_space>.

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   [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>.

   [ISO9899]  International Organization for Standardization,
              "Information technology -- Programming languages -- C",
              ISO/IEC 9899:2011, 2011,
              <https://www.iso.org/standard/57853.html>.

   [ITU-H.273]
              International Telecommunication Union, "Coding-independent
              code points for video signal type identification",
              ITU H.273, 24 September 2021,
              <https://www.itu.int/rec/T-REC-H.273/en>.

   [RFC1950]  Deutsch, P. and J. 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>.

   [RFC4122]  Leach, P., Mealling, M., and R. Salz, "A Universally
              Unique IDentifier (UUID) URN Namespace", RFC 4122,
              DOI 10.17487/RFC4122, July 2005,
              <https://www.rfc-editor.org/info/rfc4122>.

   [RFC6838]  Freed, N., Klensin, J., and T. Hansen, "Media Type
              Specifications and Registration Procedures", BCP 13,
              RFC 6838, DOI 10.17487/RFC6838, January 2013,
              <https://www.rfc-editor.org/info/rfc6838>.

   [RFC8081]  Lilley, C., "The "font" Top-Level Media Type", RFC 8081,
              DOI 10.17487/RFC8081, February 2017,
              <https://www.rfc-editor.org/info/rfc8081>.

   [RFC8126]  Cotton, M., Leiba, B., and T. Narten, "Guidelines for
              Writing an IANA Considerations Section in RFCs", BCP 26,
              RFC 8126, DOI 10.17487/RFC8126, June 2017,
              <https://www.rfc-editor.org/info/rfc8126>.

   [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>.

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   [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>.

30.  Informative References

   [AVIFormat]
              Microsoft, "AVI RIFF File Reference", 31 May 2018,
              <https://docs.microsoft.com/en-
              us/windows/win32/directshow/avi-riff-file-reference>.

   [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/>.

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

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

   [DVD-Video]
              DVD Forum, "DVD-Books: Part 3 DVD-Video Book", 1 November
              1995, <http://www.dvdforum.org/>.

   [FIPS.197] US National Institute of Standards and Technology,
              "Advanced Encryption Standard (AES)", FIPS PUB 197,
              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>.

   [FourCC-RGB]
              Silicon.dk ApS, "RGB Pixel Format FourCCs",
              <https://web.archive.org/web/20160609214806/
              https://www.fourcc.org/rgb.php>.

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   [FourCC-YUV]
              Silicon.dk ApS, "YUV Pixel Format FourCCs",
              <https://web.archive.org/web/20160609214806/
              https://www.fourcc.org/yuv.php>.

   [JPEG]     International Telegraph and Telephone Consultative
              Committee, "Digital Compression and Coding of Continuous-
              Tone Still Images", ITU T.81, September 1992,
              <https://www.w3.org/Graphics/JPEG/itu-t81.pdf>.

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

   [MatroskaCodec]
              Lhomme, S., Bunkus, M., and D. Rice, "Media Container
              Codec Specifications", Work in Progress, Internet-Draft,
              draft-ietf-cellar-codec-10, 12 April 2021,
              <https://datatracker.ietf.org/doc/html/draft-ietf-cellar-
              codec-10>.

   [MatroskaTags]
              Lhomme, S., Bunkus, M., and D. Rice, "Matroska Media
              Container Tag Specifications", Work in Progress, Internet-
              Draft, draft-ietf-cellar-tags-10, 12 April 2021,
              <https://datatracker.ietf.org/doc/html/draft-ietf-cellar-
              tags-10>.

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

   [MSRGB]    Microsoft, "WMF Compression Enumeration",
              <https://learn.microsoft.com/en-
              us/openspecs/windows_protocols/ms-wmf/4e588f70-bd92-4a6f-
              b77f-35d0feaf7a57>.

   [MSYUV16]  Microsoft, "10-bit and 16-bit YUV Video Formats",
              <https://learn.microsoft.com/en-us/windows/win32/
              medfound/10-bit-and-16-bit-yuv-video-formats>.

   [MSYUV8]   Microsoft, "Recommended 8-Bit YUV Formats for Video
              Rendering", <https://learn.microsoft.com/en-
              us/windows/win32/medfound/recommended-8-bit-yuv-formats-
              for-video-rendering>.

   [RFC0959]  Postel, J. and J. Reynolds, "File Transfer Protocol",
              STD 9, RFC 959, DOI 10.17487/RFC0959, October 1985,
              <https://www.rfc-editor.org/info/rfc959>.

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   [RFC2083]  Boutell, T., "PNG (Portable Network Graphics)
              Specification Version 1.0", RFC 2083,
              DOI 10.17487/RFC2083, March 1997,
              <https://www.rfc-editor.org/info/rfc2083>.

   [RFC3533]  Pfeiffer, S., "The Ogg Encapsulation Format Version 0",
              RFC 3533, DOI 10.17487/RFC3533, May 2003,
              <https://www.rfc-editor.org/info/rfc3533>.

   [RFC9110]  Fielding, R., Ed., Nottingham, M., Ed., and J. Reschke,
              Ed., "HTTP Semantics", STD 97, RFC 9110,
              DOI 10.17487/RFC9110, June 2022,
              <https://www.rfc-editor.org/info/rfc9110>.

   [SMB-CIFS] Microsoft Corporation, "Common Internet File System (CIFS)
              Protocol", 1 October 2020,
              <https://winprotocoldoc.blob.core.windows.net/
              productionwindowsarchives/MS-CIFS/%5bMS-CIFS%5d.pdf>.

   [SP.800-38A]
              US National Institute of Standards and Technology,
              "Recommendation for Block Cipher Modes of Operation:
              Methods and Techniques", DOI 10.6028/NIST.SP.800-38A, 1
              December 2001,
              <https://csrc.nist.gov/publications/detail/fips/197/
              final>.

   [SP.800-67]
              US National Institute of Standards and Technology,
              "Recommendation for the Triple Data Encryption Algorithm
              (TDEA) Block Cipher",
              DOI 10.6028/10.6028/NIST.SP.800-67r2, 1 November 2017,
              <https://csrc.nist.gov/publications/detail/sp/800-67/rev-
              2/final>.

   [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/>.

   [WebM-Enc] Galligan, F., "WebM Encryption", 19 September 2016,
              <https://www.webmproject.org/docs/webm-encryption/>.

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

Authors' Addresses

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   Steve Lhomme
   Email: slhomme@matroska.org

   Moritz Bunkus
   Email: moritz@bunkus.org

   Dave Rice
   Email: dave@dericed.com

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