cellar S. Lhomme Internet-Draft Intended status: Standards Track M. Bunkus Expires: 12 April 2022 D. Rice 9 October 2021 Matroska Media Container Format Specifications draft-ietf-cellar-matroska-08 Abstract This document defines the Matroska audiovisual container, including definitions of its structural elements, as well as its terminology, vocabulary, and application. Status of This Memo This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet- Drafts is at https://datatracker.ietf.org/drafts/current/. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." This Internet-Draft will expire on 12 April 2022. Copyright Notice Copyright (c) 2021 IETF Trust and the persons identified as the document authors. All rights reserved. This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (https://trustee.ietf.org/ license-info) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must include Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License. Lhomme, et al. Expires 12 April 2022 [Page 1] Internet-Draft Matroska Format October 2021 Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 5 2. Status of this document . . . . . . . . . . . . . . . . . . . 6 3. Security Considerations . . . . . . . . . . . . . . . . . . . 6 4. Notation and Conventions . . . . . . . . . . . . . . . . . . 7 5. Basis in EBML . . . . . . . . . . . . . . . . . . . . . . . . 7 5.1. Added Constraints on EBML . . . . . . . . . . . . . . . . 7 5.2. Matroska Design . . . . . . . . . . . . . . . . . . . . . 8 6. Language Codes . . . . . . . . . . . . . . . . . . . . . . . 8 7. Matroska Structure . . . . . . . . . . . . . . . . . . . . . 8 8. Matroska Schema . . . . . . . . . . . . . . . . . . . . . . . 16 8.1. Segment Element . . . . . . . . . . . . . . . . . . . . . 16 8.1.1. SeekHead Element . . . . . . . . . . . . . . . . . . 17 8.1.1.1. Seek Element . . . . . . . . . . . . . . . . . . 17 8.1.2. Info Element . . . . . . . . . . . . . . . . . . . . 18 8.1.2.1. SegmentUID Element . . . . . . . . . . . . . . . 18 8.1.2.2. SegmentFilename Element . . . . . . . . . . . . . 19 8.1.2.3. PrevUID Element . . . . . . . . . . . . . . . . . 19 8.1.2.4. PrevFilename Element . . . . . . . . . . . . . . 20 8.1.2.5. NextUID Element . . . . . . . . . . . . . . . . . 20 8.1.2.6. NextFilename Element . . . . . . . . . . . . . . 20 8.1.2.7. SegmentFamily Element . . . . . . . . . . . . . . 21 8.1.2.8. ChapterTranslate Element . . . . . . . . . . . . 21 8.1.2.9. TimestampScale Element . . . . . . . . . . . . . 23 8.1.2.10. Duration Element . . . . . . . . . . . . . . . . 23 8.1.2.11. DateUTC Element . . . . . . . . . . . . . . . . . 23 8.1.2.12. Title Element . . . . . . . . . . . . . . . . . . 24 8.1.2.13. MuxingApp Element . . . . . . . . . . . . . . . . 24 8.1.2.14. WritingApp Element . . . . . . . . . . . . . . . 25 8.1.3. Cluster Element . . . . . . . . . . . . . . . . . . . 25 8.1.3.1. Timestamp Element . . . . . . . . . . . . . . . . 25 8.1.3.2. Position Element . . . . . . . . . . . . . . . . 26 8.1.3.3. PrevSize Element . . . . . . . . . . . . . . . . 26 8.1.3.4. SimpleBlock Element . . . . . . . . . . . . . . . 26 8.1.3.5. BlockGroup Element . . . . . . . . . . . . . . . 27 8.1.4. Tracks Element . . . . . . . . . . . . . . . . . . . 32 8.1.4.1. TrackEntry Element . . . . . . . . . . . . . . . 33 8.1.5. Cues Element . . . . . . . . . . . . . . . . . . . . 89 8.1.5.1. CuePoint Element . . . . . . . . . . . . . . . . 89 8.1.6. Attachments Element . . . . . . . . . . . . . . . . . 93 8.1.6.1. AttachedFile Element . . . . . . . . . . . . . . 94 8.1.7. Chapters Element . . . . . . . . . . . . . . . . . . 96 8.1.7.1. EditionEntry Element . . . . . . . . . . . . . . 96 8.1.8. Tags Element . . . . . . . . . . . . . . . . . . . . 105 8.1.8.1. Tag Element . . . . . . . . . . . . . . . . . . . 106 9. Matroska Element Ordering . . . . . . . . . . . . . . . . . . 113 9.1. Top-Level Elements . . . . . . . . . . . . . . . . . . . 113 Lhomme, et al. Expires 12 April 2022 [Page 2] Internet-Draft Matroska Format October 2021 9.2. CRC-32 . . . . . . . . . . . . . . . . . . . . . . . . . 114 9.3. SeekHead . . . . . . . . . . . . . . . . . . . . . . . . 114 9.4. Cues (index) . . . . . . . . . . . . . . . . . . . . . . 114 9.5. Info . . . . . . . . . . . . . . . . . . . . . . . . . . 115 9.6. Chapters Element . . . . . . . . . . . . . . . . . . . . 115 9.7. Attachments . . . . . . . . . . . . . . . . . . . . . . . 115 9.8. Tags . . . . . . . . . . . . . . . . . . . . . . . . . . 115 9.9. Optimum layout from a muxer . . . . . . . . . . . . . . . 115 9.10. Optimum layout after editing tags . . . . . . . . . . . . 116 9.11. Optimum layout with Cues at the front . . . . . . . . . . 116 9.12. Cluster Timestamp . . . . . . . . . . . . . . . . . . . . 117 10. Unknown elements . . . . . . . . . . . . . . . . . . . . . . 117 11. DefaultDecodedFieldDuration . . . . . . . . . . . . . . . . . 117 12. Block Structure . . . . . . . . . . . . . . . . . . . . . . . 118 12.1. Block Header . . . . . . . . . . . . . . . . . . . . . . 118 12.2. Block Header Flags . . . . . . . . . . . . . . . . . . . 118 12.3. Lacing . . . . . . . . . . . . . . . . . . . . . . . . . 119 12.3.1. Xiph lacing . . . . . . . . . . . . . . . . . . . . 119 12.3.2. EBML lacing . . . . . . . . . . . . . . . . . . . . 120 12.3.3. Fixed-size lacing . . . . . . . . . . . . . . . . . 121 12.4. SimpleBlock Structure . . . . . . . . . . . . . . . . . 121 12.4.1. SimpleBlock Header . . . . . . . . . . . . . . . . . 121 12.4.2. SimpleBlock Header Flags . . . . . . . . . . . . . . 122 12.4.3. Laced Data . . . . . . . . . . . . . . . . . . . . . 122 13. Timestamps . . . . . . . . . . . . . . . . . . . . . . . . . 123 13.1. Timestamp Types . . . . . . . . . . . . . . . . . . . . 123 13.2. Block Timestamps . . . . . . . . . . . . . . . . . . . . 123 13.3. Raw Timestamp . . . . . . . . . . . . . . . . . . . . . 124 13.4. TimestampScale . . . . . . . . . . . . . . . . . . . . . 124 13.5. TimestampScale Rounding . . . . . . . . . . . . . . . . 124 13.6. TrackTimestampScale . . . . . . . . . . . . . . . . . . 126 14. Encryption . . . . . . . . . . . . . . . . . . . . . . . . . 128 15. Image Presentation . . . . . . . . . . . . . . . . . . . . . 128 15.1. Cropping . . . . . . . . . . . . . . . . . . . . . . . . 128 15.2. Rotation . . . . . . . . . . . . . . . . . . . . . . . . 129 16. Matroska versioning . . . . . . . . . . . . . . . . . . . . . 129 17. MIME Types . . . . . . . . . . . . . . . . . . . . . . . . . 130 18. Segment Position . . . . . . . . . . . . . . . . . . . . . . 130 18.1. Segment Position Exception . . . . . . . . . . . . . . . 130 18.2. Example of Segment Position . . . . . . . . . . . . . . 130 19. Linked Segments . . . . . . . . . . . . . . . . . . . . . . . 131 19.1. Hard Linking . . . . . . . . . . . . . . . . . . . . . . 131 19.2. Medium Linking . . . . . . . . . . . . . . . . . . . . . 133 19.2.1. Variation 1: Linked-Duration . . . . . . . . . . . . 134 19.2.2. Variation 2: Linked-Edition . . . . . . . . . . . . 134 19.3. Soft Linking . . . . . . . . . . . . . . . . . . . . . . 134 20. Track Flags . . . . . . . . . . . . . . . . . . . . . . . . . 134 20.1. Default flag . . . . . . . . . . . . . . . . . . . . . . 134 Lhomme, et al. Expires 12 April 2022 [Page 3] Internet-Draft Matroska Format October 2021 20.2. Forced flag . . . . . . . . . . . . . . . . . . . . . . 135 20.3. Hearing-impaired flag . . . . . . . . . . . . . . . . . 135 20.4. Visual-impaired flag . . . . . . . . . . . . . . . . . . 135 20.5. Descriptions flag . . . . . . . . . . . . . . . . . . . 135 20.6. Original flag . . . . . . . . . . . . . . . . . . . . . 135 20.7. Commentary flag . . . . . . . . . . . . . . . . . . . . 135 20.8. Track Operation . . . . . . . . . . . . . . . . . . . . 136 20.9. Overlay Track . . . . . . . . . . . . . . . . . . . . . 136 20.10. Multi-planar and 3D videos . . . . . . . . . . . . . . . 136 21. Default track selection . . . . . . . . . . . . . . . . . . . 137 21.1. Audio Selection . . . . . . . . . . . . . . . . . . . . 137 21.2. Subtitle selection . . . . . . . . . . . . . . . . . . . 139 22. Chapters . . . . . . . . . . . . . . . . . . . . . . . . . . 141 22.1. EditionEntry . . . . . . . . . . . . . . . . . . . . . . 141 22.1.1. EditionFlagDefault . . . . . . . . . . . . . . . . . 141 22.1.2. Default Edition . . . . . . . . . . . . . . . . . . 141 22.1.3. EditionFlagOrdered . . . . . . . . . . . . . . . . . 142 22.1.3.1. Ordered-Edition and Matroska Segment-Linking . . 143 22.2. ChapterAtom . . . . . . . . . . . . . . . . . . . . . . 144 22.2.1. ChapterTimeStart . . . . . . . . . . . . . . . . . . 144 22.2.2. ChapterTimeEnd . . . . . . . . . . . . . . . . . . . 144 22.2.3. ChapterFlagHidden . . . . . . . . . . . . . . . . . 144 22.3. Menu features . . . . . . . . . . . . . . . . . . . . . 145 22.4. Physical Types . . . . . . . . . . . . . . . . . . . . . 145 22.5. Chapter Examples . . . . . . . . . . . . . . . . . . . . 146 22.5.1. Example 1 : basic chaptering . . . . . . . . . . . . 146 22.5.2. Example 2 : nested chapters . . . . . . . . . . . . 148 22.5.2.1. The Micronauts "Bleep To Bleep" . . . . . . . . 148 23. Attachments . . . . . . . . . . . . . . . . . . . . . . . . . 150 23.1. Cover Art . . . . . . . . . . . . . . . . . . . . . . . 151 24. Cues . . . . . . . . . . . . . . . . . . . . . . . . . . . . 152 24.1. Recommendations . . . . . . . . . . . . . . . . . . . . 152 25. Matroska Streaming . . . . . . . . . . . . . . . . . . . . . 153 25.1. File Access . . . . . . . . . . . . . . . . . . . . . . 153 25.2. Livestreaming . . . . . . . . . . . . . . . . . . . . . 154 26. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 154 26.1. Matroska Element IDs Registry . . . . . . . . . . . . . 154 26.2. ChapterCodecID Registry . . . . . . . . . . . . . . . . 154 26.3. Historic Deprecated Element IDs Registry . . . . . . . . 154 26.3.1. SilentTracks Element . . . . . . . . . . . . . . . . 155 26.3.2. SilentTrackNumber Element . . . . . . . . . . . . . 155 26.3.3. BlockVirtual Element . . . . . . . . . . . . . . . . 155 26.3.4. ReferenceVirtual Element . . . . . . . . . . . . . . 155 26.3.5. FrameNumber Element . . . . . . . . . . . . . . . . 156 26.3.6. BlockAdditionID Element . . . . . . . . . . . . . . 156 26.3.7. Delay Element . . . . . . . . . . . . . . . . . . . 156 26.3.8. SliceDuration Element . . . . . . . . . . . . . . . 156 26.3.9. ReferenceFrame Element . . . . . . . . . . . . . . . 156 Lhomme, et al. Expires 12 April 2022 [Page 4] Internet-Draft Matroska Format October 2021 26.3.10. ReferenceOffset Element . . . . . . . . . . . . . . 157 26.3.11. ReferenceTimestamp Element . . . . . . . . . . . . . 157 26.3.12. EncryptedBlock Element . . . . . . . . . . . . . . . 157 26.3.13. TrackOffset Element . . . . . . . . . . . . . . . . 157 26.3.14. CodecSettings Element . . . . . . . . . . . . . . . 158 26.3.15. CodecInfoURL Element . . . . . . . . . . . . . . . . 158 26.3.16. CodecDownloadURL Element . . . . . . . . . . . . . . 158 26.3.17. CodecDecodeAll Element . . . . . . . . . . . . . . . 158 26.3.18. OldStereoMode Element . . . . . . . . . . . . . . . 158 26.3.19. AspectRatioType Element . . . . . . . . . . . . . . 159 26.3.20. GammaValue Element . . . . . . . . . . . . . . . . . 159 26.3.21. FrameRate Element . . . . . . . . . . . . . . . . . 159 26.3.22. ChannelPositions Element . . . . . . . . . . . . . . 159 26.3.23. TrickTrackUID Element . . . . . . . . . . . . . . . 160 26.3.24. TrickTrackSegmentUID Element . . . . . . . . . . . . 160 26.3.25. TrickTrackFlag Element . . . . . . . . . . . . . . . 160 26.3.26. TrickMasterTrackUID Element . . . . . . . . . . . . 160 26.3.27. TrickMasterTrackSegmentUID Element . . . . . . . . . 161 26.3.28. ContentSignature Element . . . . . . . . . . . . . . 161 26.3.29. ContentSigKeyID Element . . . . . . . . . . . . . . 161 26.3.30. ContentSigAlgo Element . . . . . . . . . . . . . . . 161 26.3.31. ContentSigHashAlgo Element . . . . . . . . . . . . . 162 26.3.32. CueRefCluster Element . . . . . . . . . . . . . . . 162 26.3.33. CueRefNumber Element . . . . . . . . . . . . . . . . 162 26.3.34. CueRefCodecState Element . . . . . . . . . . . . . . 162 26.3.35. FileReferral Element . . . . . . . . . . . . . . . . 163 26.3.36. FileUsedStartTime Element . . . . . . . . . . . . . 163 26.3.37. FileUsedEndTime Element . . . . . . . . . . . . . . 163 26.3.38. TagDefaultBogus Element . . . . . . . . . . . . . . 163 27. Normative References . . . . . . . . . . . . . . . . . . . . 164 28. Informative References . . . . . . . . . . . . . . . . . . . 165 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 166 1. Introduction Matroska aims to become THE standard of multimedia container formats. It was derived from a project called [MCF], but differentiates from it significantly because it is based on EBML (Extensible Binary Meta Language) [RFC8794], a binary derivative of XML. EBML enables significant advantages in terms of future format extensibility, without breaking file support in old parsers. First, it is essential to clarify exactly "What an Audio/Video container is", to avoid any misunderstandings: * It is NOT a video or audio compression format (codec) Lhomme, et al. Expires 12 April 2022 [Page 5] Internet-Draft Matroska Format October 2021 * It is an envelope for which there can be many audio, video, and subtitles streams, allowing the user to store a complete movie or CD in a single file. Matroska is designed with the future in mind. It incorporates features like: * Fast seeking in the file * Chapter entries * Full metadata (tags) support * Selectable subtitle/audio/video streams * Modularly expandable * Error resilience (can recover playback even when the stream is damaged) * Streamable over the internet and local networks (HTTP, CIFS, FTP, etc) * Menus (like DVDs have) Matroska is an open standards project. This means for personal use it is absolutely free to use and that the technical specifications describing the bitstream are open to everybody, even to companies that would like to support it in their products. 2. Status of this document This document is a work-in-progress specification defining the Matroska file format as part of the IETF Cellar working group (https://datatracker.ietf.org/wg/cellar/charter/). But since it's quite complete it is used as a reference for the development of libmatroska. Note that versions 1, 2, and 3 have been finalized. Version 4 is currently work in progress. There MAY be further additions to v4. 3. Security Considerations Matroska inherits security considerations from EBML. Attacks on a Matroska Reader could include: Lhomme, et al. Expires 12 April 2022 [Page 6] Internet-Draft Matroska Format October 2021 * Storage of a arbitrary and potentially executable data within an Attachment Element. Matroska Readers that extract or use data from Matroska Attachments SHOULD check that the data adheres to expectations. * A Matroska Attachment with an inaccurate mime-type. 4. Notation and Conventions The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all capitals, as shown here. This document defines specific terms in order to define the format and application of Matroska. Specific terms are defined below: Matroska: A multimedia container format based on EBML (Extensible Binary Meta Language). Matroska Reader: A data parser that interprets the semantics of a Matroska document and creates a way for programs to use Matroska. Matroska Player: A Matroska Reader with a primary purpose of playing audiovisual files, including Matroska documents. 5. Basis in EBML Matroska is a Document Type of EBML (Extensible Binary Meta Language). This specification is dependent on the EBML Specification [RFC8794]. For an understanding of Matroska's EBML Schema, see in particular the sections of the EBML Specification covering EBML Element Types (Section 7), EBML Schema (Section 11.1), and EBML Structure (Section 3). 5.1. Added Constraints on EBML As an EBML Document Type, Matroska adds the following constraints to the EBML specification. * The docType of the EBML Header MUST be "matroska". * The EBMLMaxIDLength of the EBML Header MUST be "4". * The EBMLMaxSizeLength of the EBML Header MUST be between "1" and "8" inclusive. Lhomme, et al. Expires 12 April 2022 [Page 7] Internet-Draft Matroska Format October 2021 5.2. Matroska Design All top-levels elements (Segment and direct sub-elements) are coded on 4 octets -- i.e. class D elements. 6. Language Codes Matroska from version 1 through 3 uses language codes that can be either the 3 letters bibliographic ISO-639-2 form [ISO639-2] (like "fre" for french), or such a language code followed by a dash and a country code for specialities in languages (like "fre-ca" for Canadian French). The ISO 639-2 Language Elements are "Language Element", "TagLanguage Element", and "ChapLanguage Element". Starting in Matroska version 4, either [ISO639-2] or [BCP47] MAY be used, although BCP 47 is RECOMMENDED. The BCP 47 Language Elements are "LanguageIETF Element", "TagLanguageIETF Element", and "ChapLanguageIETF Element". If a BCP 47 Language Element and an ISO 639-2 Language Element are used within the same Parent Element, then the ISO 639-2 Language Element MUST be ignored and precedence given to the BCP 47 Language Element. Country codes are the same 2 octets country-codes as in Internet domains [IANADomains] based on [ISO3166-1] alpha-2 codes. 7. Matroska Structure A Matroska file MUST be composed of at least one EBML Document using the Matroska Document Type. Each EBML Document MUST start with an EBML Header and MUST be followed by the EBML Root Element, defined as Segment in Matroska. Matroska defines several Top Level Elements which MAY occur within the Segment. As an example, a simple Matroska file consisting of a single EBML Document could be represented like this: * EBML Header * Segment A more complex Matroska file consisting of an EBML Stream (consisting of two EBML Documents) could be represented like this: * EBML Header * Segment * EBML Header Lhomme, et al. Expires 12 April 2022 [Page 8] Internet-Draft Matroska Format October 2021 * Segment The following diagram represents a simple Matroska file, comprised of an EBML Document with an EBML Header, a Segment Element (the Root Element), and all eight Matroska Top Level Elements. In the following diagrams of this section, horizontal spacing expresses a parent-child relationship between Matroska Elements (e.g., the Info Element is contained within the Segment Element) whereas vertical alignment represents the storage order within the file. +-------------+ | EBML Header | +---------------------------+ | Segment | SeekHead | | |-------------| | | Info | | |-------------| | | Tracks | | |-------------| | | Chapters | | |-------------| | | Cluster | | |-------------| | | Cues | | |-------------| | | Attachments | | |-------------| | | Tags | +---------------------------+ Figure 1: Basic layout of a Matroska file. The Matroska EBML Schema defines eight Top Level Elements: SeekHead, Info, Tracks, Chapters, Cluster, Cues, Attachments, and Tags. The SeekHead Element (also known as MetaSeek) contains an index of Top Level Elements locations within the Segment. Use of the SeekHead Element is RECOMMENDED. Without a SeekHead Element, a Matroska parser would have to search the entire file to find all of the other Top Level Elements. This is due to Matroska's flexible ordering requirements; for instance, it is acceptable for the Chapters Element to be stored after the Cluster Elements. +--------------------------------+ | SeekHead | Seek | SeekID | | | |--------------| | | | SeekPosition | +--------------------------------+ Lhomme, et al. Expires 12 April 2022 [Page 9] Internet-Draft Matroska Format October 2021 Figure 2: Representation of a SeekHead Element. The Info Element contains vital information for identifying the whole Segment. This includes the title for the Segment, a randomly generated unique identifier, and the unique identifier(s) of any linked Segment Elements. +-------------------------+ | Info | SegmentUID | | |------------------| | | SegmentFilename | | |------------------| | | PrevUID | | |------------------| | | PrevFilename | | |------------------| | | NextUID | | |------------------| | | NextFilename | | |------------------| | | SegmentFamily | | |------------------| | | ChapterTranslate | | |------------------| | | TimestampScale | | |------------------| | | Duration | | |------------------| | | DateUTC | | |------------------| | | Title | | |------------------| | | MuxingApp | | |------------------| | | WritingApp | |-------------------------| Figure 3: Representation of an Info Element and its Child Elements. The Tracks Element defines the technical details for each track and can store the name, number, unique identifier, language, and type (audio, video, subtitles, etc.) of each track. For example, the Tracks Element MAY store information about the resolution of a video track or sample rate of an audio track. The Tracks Element MUST identify all the data needed by the codec to decode the data of the specified track. However, the data required is contingent on the codec used for the track. For example, a Track Lhomme, et al. Expires 12 April 2022 [Page 10] Internet-Draft Matroska Format October 2021 Element for uncompressed audio only requires the audio bit rate to be present. A codec such as AC-3 would require that the CodecID Element be present for all tracks, as it is the primary way to identify which codec to use to decode the track. +------------------------------------+ | Tracks | TrackEntry | TrackNumber | | | |--------------| | | | TrackUID | | | |--------------| | | | TrackType | | | |--------------| | | | Name | | | |--------------| | | | Language | | | |--------------| | | | CodecID | | | |--------------| | | | CodecPrivate | | | |--------------| | | | CodecName | | | |----------------------------------+ | | | Video | FlagInterlaced | | | | |-------------------| | | | | FieldOrder | | | | |-------------------| | | | | StereoMode | | | | |-------------------| | | | | AlphaMode | | | | |-------------------| | | | | PixelWidth | | | | |-------------------| | | | | PixelHeight | | | | |-------------------| | | | | DisplayWidth | | | | |-------------------| | | | | DisplayHeight | | | | |-------------------| | | | | AspectRatioType | | | | |-------------------| | | | | Color | | | |----------------------------------| | | | Audio | SamplingFrequency | | | | |-------------------| | | | | Channels | | | | |-------------------| | | | | BitDepth | |--------------------------------------------------------| Lhomme, et al. Expires 12 April 2022 [Page 11] Internet-Draft Matroska Format October 2021 Figure 4: Representation of the Tracks Element and a selection of its Descendant Elements. The Chapters Element lists all of the chapters. Chapters are a way to set predefined points to jump to in video or audio. +-----------------------------------------+ | Chapters | Edition | EditionUID | | | Entry |--------------------| | | | EditionFlagDefault | | | |--------------------| | | | EditionFlagOrdered | | | |---------------------------------+ | | | ChapterAtom | ChapterUID | | | | |-------------------| | | | | ChapterStringUID | | | | |-------------------| | | | | ChapterTimeStart | | | | |-------------------| | | | | ChapterTimeEnd | | | | |-------------------| | | | | ChapterFlagHidden | | | | |-------------------------------+ | | | | ChapterDisplay | ChapString | | | | | |--------------| | | | | | ChapLanguage | +------------------------------------------------------------------+ Figure 5: Representation of the Chapters Element and a selection of its Descendant Elements. Cluster Elements contain the content for each track, e.g., video frames. A Matroska file SHOULD contain at least one Cluster Element. The Cluster Element helps to break up SimpleBlock or BlockGroup Elements and helps with seeking and error protection. It is RECOMMENDED that the size of each individual Cluster Element be limited to store no more than 5 seconds or 5 megabytes. Every Cluster Element MUST contain a Timestamp Element. This SHOULD be the Timestamp Element used to play the first Block in the Cluster Element. There SHOULD be one or more BlockGroup or SimpleBlock Element in each Cluster Element. A BlockGroup Element MAY contain a Block of data and any information relating directly to that Block. Lhomme, et al. Expires 12 April 2022 [Page 12] Internet-Draft Matroska Format October 2021 +--------------------------+ | Cluster | Timestamp | | |----------------| | | SilentTracks | | |----------------| | | Position | | |----------------| | | PrevSize | | |----------------| | | SimpleBlock | | |----------------| | | BlockGroup | | |----------------| | | EncryptedBlock | +--------------------------+ Figure 6: Representation of a Cluster Element and its immediate Child Elements. +----------------------------------+ | Block | Portion of | Data Type | | | a Block | - Bit Flag | | |--------------------------+ | | Header | TrackNumber | | | |-------------| | | | Timestamp | | | |-------------| | | | Flags | | | | - Gap | | | | - Lacing | | | | - Reserved | | |--------------------------| | | Optional | FrameSize | | |--------------------------| | | Data | Frame | +----------------------------------+ Figure 7: Representation of the Block Element structure. Each Cluster MUST contain exactly one Timestamp Element. The Timestamp Element value MUST be stored once per Cluster. The Timestamp Element in the Cluster is relative to the entire Segment. The Timestamp Element SHOULD be the first Element in the Cluster. Additionally, the Block contains an offset that, when added to the Cluster's Timestamp Element value, yields the Block's effective timestamp. Therefore, timestamp in the Block itself is relative to the Timestamp Element in the Cluster. For example, if the Timestamp Lhomme, et al. Expires 12 April 2022 [Page 13] Internet-Draft Matroska Format October 2021 Element in the Cluster is set to 10 seconds and a Block in that Cluster is supposed to be played 12 seconds into the clip, the timestamp in the Block would be set to 2 seconds. The ReferenceBlock in the BlockGroup is used instead of the basic "P-frame"/"B-frame" description. Instead of simply saying that this Block depends on the Block directly before, or directly afterwards, the Timestamp of the necessary Block is used. Because there can be as many ReferenceBlock Elements as necessary for a Block, it allows for some extremely complex referencing. The Cues Element is used to seek when playing back a file by providing a temporal index for some of the Tracks. It is similar to the SeekHead Element, but used for seeking to a specific time when playing back the file. It is possible to seek without this element, but it is much more difficult because a Matroska Reader would have to 'hunt and peck' through the file looking for the correct timestamp. The Cues Element SHOULD contain at least one CuePoint Element. Each CuePoint Element stores the position of the Cluster that contains the BlockGroup or SimpleBlock Element. The timestamp is stored in the CueTime Element and location is stored in the CueTrackPositions Element. The Cues Element is flexible. For instance, Cues Element can be used to index every single timestamp of every Block or they can be indexed selectively. For video files, it is RECOMMENDED to index at least the keyframes of the video track. +-------------------------------------+ | Cues | CuePoint | CueTime | | | |-------------------| | | | CueTrackPositions | | |------------------------------| | | CuePoint | CueTime | | | |-------------------| | | | CueTrackPositions | +-------------------------------------+ Figure 8: Representation of a Cues Element and two levels of its Descendant Elements. The Attachments Element is for attaching files to a Matroska file such as pictures, webpages, programs, or even the codec needed to play back the file. Lhomme, et al. Expires 12 April 2022 [Page 14] Internet-Draft Matroska Format October 2021 +------------------------------------------------+ | Attachments | AttachedFile | FileDescription | | | |-------------------| | | | FileName | | | |-------------------| | | | FileMimeType | | | |-------------------| | | | FileData | | | |-------------------| | | | FileUID | | | |-------------------| | | | FileName | | | |-------------------| | | | FileReferral | | | |-------------------| | | | FileUsedStartTime | | | |-------------------| | | | FileUsedEndTime | +------------------------------------------------+ Figure 9: Representation of a Attachments Element. The Tags Element contains metadata that describes the Segment and potentially its Tracks, Chapters, and Attachments. Each Track or Chapter that those tags applies to has its UID listed in the Tags. The Tags contain all extra information about the file: scriptwriter, singer, actors, directors, titles, edition, price, dates, genre, comments, etc. Tags can contain their values in multiple languages. For example, a movie's "title" Tag might contain both the original English title as well as the title it was released as in Germany. Lhomme, et al. Expires 12 April 2022 [Page 15] Internet-Draft Matroska Format October 2021 +-------------------------------------------+ | Tags | Tag | Targets | TargetTypeValue | | | | |------------------| | | | | TargetType | | | | |------------------| | | | | TagTrackUID | | | | |------------------| | | | | TagEditionUID | | | | |------------------| | | | | TagChapterUID | | | | |------------------| | | | | TagAttachmentUID | | | |------------------------------| | | | SimpleTag | TagName | | | | |------------------| | | | | TagLanguage | | | | |------------------| | | | | TagDefault | | | | |------------------| | | | | TagString | | | | |------------------| | | | | TagBinary | | | | |------------------| | | | | SimpleTag | +-------------------------------------------+ Figure 10: Representation of a Tags Element and three levels of its Children Elements. 8. Matroska Schema This specification includes an EBML Schema, which defines the Elements and structure of Matroska as an EBML Document Type. The EBML Schema defines every valid Matroska element in a manner defined by the EBML specification. Here the definition of each Matroska Element is provided. 8.1. Segment Element name: Segment path: \Segment id: 0x18538067 minOccurs: 1 Lhomme, et al. Expires 12 April 2022 [Page 16] Internet-Draft Matroska Format October 2021 maxOccurs: 1 type: master unknownsizeallowed: 1 definition: The Root Element that contains all other Top-Level Elements (Elements defined only at Level 1). A Matroska file is composed of 1 Segment. 8.1.1. SeekHead Element name: SeekHead path: \Segment\SeekHead id: 0x114D9B74 maxOccurs: 2 type: master definition: Contains the Segment Position of other Top-Level Elements. 8.1.1.1. Seek Element name: Seek path: \Segment\SeekHead\Seek id: 0x4DBB minOccurs: 1 type: master definition: Contains a single seek entry to an EBML Element. 8.1.1.1.1. SeekID Element name: SeekID path: \Segment\SeekHead\Seek\SeekID id: 0x53AB minOccurs: 1 Lhomme, et al. Expires 12 April 2022 [Page 17] Internet-Draft Matroska Format October 2021 maxOccurs: 1 type: binary definition: The binary ID corresponding to the Element name. 8.1.1.1.2. SeekPosition Element name: SeekPosition path: \Segment\SeekHead\Seek\SeekPosition id: 0x53AC minOccurs: 1 maxOccurs: 1 type: uinteger definition: The Segment Position of the Element. 8.1.2. Info Element name: Info path: \Segment\Info id: 0x1549A966 minOccurs: 1 maxOccurs: 1 type: master recurring: 1 definition: Contains general information about the Segment. 8.1.2.1. SegmentUID Element name: SegmentUID path: \Segment\Info\SegmentUID id: 0x73A4 Lhomme, et al. Expires 12 April 2022 [Page 18] Internet-Draft Matroska Format October 2021 maxOccurs: 1 range: not 0 type: binary definition: A randomly generated unique ID to identify the Segment amongst many others (128 bits). usage notes: If the Segment is a part of a Linked Segment, then this Element is REQUIRED. 8.1.2.2. SegmentFilename Element name: SegmentFilename path: \Segment\Info\SegmentFilename id: 0x7384 maxOccurs: 1 type: utf-8 definition: A filename corresponding to this Segment. 8.1.2.3. PrevUID Element name: PrevUID path: \Segment\Info\PrevUID id: 0x3CB923 maxOccurs: 1 type: binary definition: A unique ID to identify the previous Segment of a Linked Segment (128 bits). usage notes: If the Segment is a part of a Linked Segment that uses Hard Linking, then either the PrevUID or the NextUID Element is REQUIRED. If a Segment contains a PrevUID but not a NextUID, then it MAY be considered as the last Segment of the Linked Segment. The PrevUID MUST NOT be equal to the SegmentUID. Lhomme, et al. Expires 12 April 2022 [Page 19] Internet-Draft Matroska Format October 2021 8.1.2.4. PrevFilename Element name: PrevFilename path: \Segment\Info\PrevFilename id: 0x3C83AB maxOccurs: 1 type: utf-8 definition: A filename corresponding to the file of the previous Linked Segment. usage notes: Provision of the previous filename is for display convenience, but PrevUID SHOULD be considered authoritative for identifying the previous Segment in a Linked Segment. 8.1.2.5. NextUID Element name: NextUID path: \Segment\Info\NextUID id: 0x3EB923 maxOccurs: 1 type: binary definition: A unique ID to identify the next Segment of a Linked Segment (128 bits). usage notes: If the Segment is a part of a Linked Segment that uses Hard Linking, then either the PrevUID or the NextUID Element is REQUIRED. If a Segment contains a NextUID but not a PrevUID, then it MAY be considered as the first Segment of the Linked Segment. The NextUID MUST NOT be equal to the SegmentUID. 8.1.2.6. NextFilename Element name: NextFilename path: \Segment\Info\NextFilename id: 0x3E83BB Lhomme, et al. Expires 12 April 2022 [Page 20] Internet-Draft Matroska Format October 2021 maxOccurs: 1 type: utf-8 definition: A filename corresponding to the file of the next Linked Segment. usage notes: Provision of the next filename is for display convenience, but NextUID SHOULD be considered authoritative for identifying the Next Segment. 8.1.2.7. SegmentFamily Element name: SegmentFamily path: \Segment\Info\SegmentFamily id: 0x4444 type: binary definition: A randomly generated unique ID that all Segments of a Linked Segment MUST share (128 bits). usage notes: If the Segment is a part of a Linked Segment that uses Soft Linking, then this Element is REQUIRED. 8.1.2.8. ChapterTranslate Element name: ChapterTranslate path: \Segment\Info\ChapterTranslate id: 0x6924 type: master definition: A tuple of corresponding ID used by chapter codecs to represent this Segment. 8.1.2.8.1. ChapterTranslateEditionUID Element name: ChapterTranslateEditionUID path: \Segment\Info\ChapterTranslate\ChapterTranslateEditionUID id: 0x69FC Lhomme, et al. Expires 12 April 2022 [Page 21] Internet-Draft Matroska Format October 2021 type: uinteger definition: Specify an edition UID on which this correspondence applies. When not specified, it means for all editions found in the Segment. 8.1.2.8.2. ChapterTranslateCodec Element name: ChapterTranslateCodec path: \Segment\Info\ChapterTranslate\ChapterTranslateCodec id: 0x69BF minOccurs: 1 maxOccurs: 1 type: uinteger definition: The chapter codec; see Section 8.1.7.1.4.15. restrictions: +=======+=================+ | value | label | +=======+=================+ | 0 | Matroska Script | +-------+-----------------+ | 1 | DVD-menu | +-------+-----------------+ Table 1: ChapterTranslateCodec values 8.1.2.8.3. ChapterTranslateID Element name: ChapterTranslateID path: \Segment\Info\ChapterTranslate\ChapterTranslateID id: 0x69A5 minOccurs: 1 maxOccurs: 1 Lhomme, et al. Expires 12 April 2022 [Page 22] Internet-Draft Matroska Format October 2021 type: binary definition: The binary value used to represent this Segment in the chapter codec data. The format depends on the ChapProcessCodecID used; see Section 8.1.7.1.4.15. 8.1.2.9. TimestampScale Element name: TimestampScale path: \Segment\Info\TimestampScale id: 0x2AD7B1 minOccurs: 1 maxOccurs: 1 range: not 0 default: 1000000 type: uinteger definition: Timestamp scale in nanoseconds (1.000.000 means all timestamps in the Segment are expressed in milliseconds). 8.1.2.10. Duration Element name: Duration path: \Segment\Info\Duration id: 0x4489 maxOccurs: 1 range: > 0x0p+0 type: float definition: Duration of the Segment in nanoseconds based on TimestampScale. 8.1.2.11. DateUTC Element name: DateUTC Lhomme, et al. Expires 12 April 2022 [Page 23] Internet-Draft Matroska Format October 2021 path: \Segment\Info\DateUTC id: 0x4461 maxOccurs: 1 type: date definition: The date and time that the Segment was created by the muxing application or library. 8.1.2.12. Title Element name: Title path: \Segment\Info\Title id: 0x7BA9 maxOccurs: 1 type: utf-8 definition: General name of the Segment. 8.1.2.13. MuxingApp Element name: MuxingApp path: \Segment\Info\MuxingApp id: 0x4D80 minOccurs: 1 maxOccurs: 1 type: utf-8 definition: Muxing application or library (example: "libmatroska- 0.4.3"). usage notes: Include the full name of the application or library followed by the version number. Lhomme, et al. Expires 12 April 2022 [Page 24] Internet-Draft Matroska Format October 2021 8.1.2.14. WritingApp Element name: WritingApp path: \Segment\Info\WritingApp id: 0x5741 minOccurs: 1 maxOccurs: 1 type: utf-8 definition: Writing application (example: "mkvmerge-0.3.3"). usage notes: Include the full name of the application followed by the version number. 8.1.3. Cluster Element name: Cluster path: \Segment\Cluster id: 0x1F43B675 type: master unknownsizeallowed: 1 definition: The Top-Level Element containing the (monolithic) Block structure. 8.1.3.1. Timestamp Element name: Timestamp path: \Segment\Cluster\Timestamp id: 0xE7 minOccurs: 1 maxOccurs: 1 type: uinteger Lhomme, et al. Expires 12 April 2022 [Page 25] Internet-Draft Matroska Format October 2021 definition: Absolute timestamp of the cluster (based on TimestampScale). 8.1.3.2. Position Element name: Position path: \Segment\Cluster\Position id: 0xA7 maxOccurs: 1 type: uinteger definition: The Segment Position of the Cluster in the Segment (0 in live streams). It might help to resynchronise offset on damaged streams. 8.1.3.3. PrevSize Element name: PrevSize path: \Segment\Cluster\PrevSize id: 0xAB maxOccurs: 1 type: uinteger definition: Size of the previous Cluster, in octets. Can be useful for backward playing. 8.1.3.4. SimpleBlock Element name: SimpleBlock path: \Segment\Cluster\SimpleBlock id: 0xA3 type: binary minver: 2 definition: Similar to Block, see Section 12, but without all the Lhomme, et al. Expires 12 April 2022 [Page 26] Internet-Draft Matroska Format October 2021 extra information, mostly used to reduced overhead when no extra feature is needed; see Section 12.4 on SimpleBlock Structure. 8.1.3.5. BlockGroup Element name: BlockGroup path: \Segment\Cluster\BlockGroup id: 0xA0 type: master definition: Basic container of information containing a single Block and information specific to that Block. 8.1.3.5.1. Block Element name: Block path: \Segment\Cluster\BlockGroup\Block id: 0xA1 minOccurs: 1 maxOccurs: 1 type: binary definition: Block containing the actual data to be rendered and a timestamp relative to the Cluster Timestamp; see Section 12 on Block Structure. 8.1.3.5.2. BlockAdditions Element name: BlockAdditions path: \Segment\Cluster\BlockGroup\BlockAdditions id: 0x75A1 maxOccurs: 1 type: master definition: Contain additional blocks to complete the main one. An Lhomme, et al. Expires 12 April 2022 [Page 27] Internet-Draft Matroska Format October 2021 EBML parser that has no knowledge of the Block structure could still see and use/skip these data. 8.1.3.5.2.1. BlockMore Element name: BlockMore path: \Segment\Cluster\BlockGroup\BlockAdditions\BlockMore id: 0xA6 minOccurs: 1 type: master definition: Contain the BlockAdditional and some parameters. 8.1.3.5.2.2. BlockAddID Element name: BlockAddID path: \Segment\Cluster\BlockGroup\BlockAdditions\BlockMore\BlockAddI D id: 0xEE minOccurs: 1 maxOccurs: 1 range: not 0 default: 1 type: uinteger definition: An ID to identify the BlockAdditional level. If BlockAddIDType of the corresponding block is 0, this value is also the value of BlockAddIDType for the meaning of the content of BlockAdditional. 8.1.3.5.2.3. BlockAdditional Element name: BlockAdditional path: \Segment\Cluster\BlockGroup\BlockAdditions\BlockMore\BlockAddi tional Lhomme, et al. Expires 12 April 2022 [Page 28] Internet-Draft Matroska Format October 2021 id: 0xA5 minOccurs: 1 maxOccurs: 1 type: binary definition: Interpreted by the codec as it wishes (using the BlockAddID). 8.1.3.5.3. BlockDuration Element name: BlockDuration path: \Segment\Cluster\BlockGroup\BlockDuration id: 0x9B minOccurs: see implementation notes maxOccurs: 1 default: see implementation notes type: uinteger definition: The duration of the Block (based on TimestampScale). The BlockDuration Element can be useful at the end of a Track to define the duration of the last frame (as there is no subsequent Block available), or when there is a break in a track like for subtitle tracks. notes: Lhomme, et al. Expires 12 April 2022 [Page 29] Internet-Draft Matroska Format October 2021 +===========+===================================================+ | attribute | note | +===========+===================================================+ | minOccurs | BlockDuration MUST be set (minOccurs=1) if the | | | associated TrackEntry stores a DefaultDuration | | | value. | +-----------+---------------------------------------------------+ | default | When not written and with no DefaultDuration, the | | | value is assumed to be the difference between the | | | timestampof this Block and the timestamp of the | | | next Block in "display" order (not coding order). | +-----------+---------------------------------------------------+ Table 2: BlockDuration implementation notes 8.1.3.5.4. ReferencePriority Element name: ReferencePriority path: \Segment\Cluster\BlockGroup\ReferencePriority id: 0xFA minOccurs: 1 maxOccurs: 1 default: 0 type: uinteger definition: This frame is referenced and has the specified cache priority. In cache only a frame of the same or higher priority can replace this frame. A value of 0 means the frame is not referenced. 8.1.3.5.5. ReferenceBlock Element name: ReferenceBlock path: \Segment\Cluster\BlockGroup\ReferenceBlock id: 0xFB type: integer definition: Timestamp of another frame used as a reference (ie: B or Lhomme, et al. Expires 12 April 2022 [Page 30] Internet-Draft Matroska Format October 2021 P frame). The timestamp is relative to the block it's attached to. 8.1.3.5.6. CodecState Element name: CodecState path: \Segment\Cluster\BlockGroup\CodecState id: 0xA4 maxOccurs: 1 type: binary minver: 2 definition: The new codec state to use. Data interpretation is private to the codec. This information SHOULD always be referenced by a seek entry. 8.1.3.5.7. DiscardPadding Element name: DiscardPadding path: \Segment\Cluster\BlockGroup\DiscardPadding id: 0x75A2 maxOccurs: 1 type: integer minver: 4 definition: Duration in nanoseconds of the silent data added to the Block (padding at the end of the Block for positive value, at the beginning of the Block for negative value). The duration of DiscardPadding is not calculated in the duration of the TrackEntry and SHOULD be discarded during playback. 8.1.3.5.8. Slices Element name: Slices path: \Segment\Cluster\BlockGroup\Slices id: 0x8E Lhomme, et al. Expires 12 April 2022 [Page 31] Internet-Draft Matroska Format October 2021 maxOccurs: 1 type: master maxver: 1 definition: Contains slices description. 8.1.3.5.8.1. TimeSlice Element name: TimeSlice path: \Segment\Cluster\BlockGroup\Slices\TimeSlice id: 0xE8 type: master maxver: 1 definition: Contains extra time information about the data contained in the Block. Being able to interpret this Element is not REQUIRED for playback. 8.1.3.5.8.2. LaceNumber Element name: LaceNumber path: \Segment\Cluster\BlockGroup\Slices\TimeSlice\LaceNumber id: 0xCC maxOccurs: 1 type: uinteger maxver: 1 definition: The reverse number of the frame in the lace (0 is the last frame, 1 is the next to last, etc). Being able to interpret this Element is not REQUIRED for playback. 8.1.4. Tracks Element name: Tracks path: \Segment\Tracks Lhomme, et al. Expires 12 April 2022 [Page 32] Internet-Draft Matroska Format October 2021 id: 0x1654AE6B maxOccurs: 1 type: master recurring: 1 definition: A Top-Level Element of information with many tracks described. 8.1.4.1. TrackEntry Element name: TrackEntry path: \Segment\Tracks\TrackEntry id: 0xAE minOccurs: 1 type: master definition: Describes a track with all Elements. 8.1.4.1.1. TrackNumber Element name: TrackNumber path: \Segment\Tracks\TrackEntry\TrackNumber id: 0xD7 minOccurs: 1 maxOccurs: 1 range: not 0 type: uinteger definition: The track number as used in the Block Header (using more than 127 tracks is not encouraged, though the design allows an unlimited number). Lhomme, et al. Expires 12 April 2022 [Page 33] Internet-Draft Matroska Format October 2021 8.1.4.1.2. TrackUID Element name: TrackUID path: \Segment\Tracks\TrackEntry\TrackUID id: 0x73C5 minOccurs: 1 maxOccurs: 1 range: not 0 type: uinteger definition: A unique ID to identify the Track. usage notes: The value of this Element SHOULD be kept the same when making a direct stream copy to another file. 8.1.4.1.3. TrackType Element name: TrackType path: \Segment\Tracks\TrackEntry\TrackType id: 0x83 minOccurs: 1 maxOccurs: 1 type: uinteger definition: A set of track types coded on 8 bits. restrictions: Lhomme, et al. Expires 12 April 2022 [Page 34] Internet-Draft Matroska Format October 2021 +=======+==========+ | value | label | +=======+==========+ | 1 | video | +-------+----------+ | 2 | audio | +-------+----------+ | 3 | complex | +-------+----------+ | 16 | logo | +-------+----------+ | 17 | subtitle | +-------+----------+ | 18 | buttons | +-------+----------+ | 32 | control | +-------+----------+ | 33 | metadata | +-------+----------+ Table 3: TrackType values 8.1.4.1.4. FlagEnabled Element name: FlagEnabled path: \Segment\Tracks\TrackEntry\FlagEnabled id: 0xB9 minOccurs: 1 maxOccurs: 1 range: 0-1 default: 1 type: uinteger minver: 2 definition: Set to 1 if the track is usable. It is possible to turn a not usable track into a usable track using chapter codecs or control tracks. Lhomme, et al. Expires 12 April 2022 [Page 35] Internet-Draft Matroska Format October 2021 8.1.4.1.5. FlagDefault Element name: FlagDefault path: \Segment\Tracks\TrackEntry\FlagDefault id: 0x88 minOccurs: 1 maxOccurs: 1 range: 0-1 default: 1 type: uinteger definition: Set if that track (audio, video or subs) SHOULD be eligible for automatic selection by the player; see Section 21 for more details. 8.1.4.1.6. FlagForced Element name: FlagForced path: \Segment\Tracks\TrackEntry\FlagForced id: 0x55AA minOccurs: 1 maxOccurs: 1 range: 0-1 default: 0 type: uinteger definition: Applies only to subtitles. Set if that track SHOULD be eligible for automatic selection by the player if it matches the user's language preference, even if the user's preferences would normally not enable subtitles with the selected audio track; this can be used for tracks containing only translations of foreign- language audio or onscreen text. See Section 21 for more details. Lhomme, et al. Expires 12 April 2022 [Page 36] Internet-Draft Matroska Format October 2021 8.1.4.1.7. FlagHearingImpaired Element name: FlagHearingImpaired path: \Segment\Tracks\TrackEntry\FlagHearingImpaired id: 0x55AB maxOccurs: 1 range: 0-1 type: uinteger minver: 4 definition: Set to 1 if that track is suitable for users with hearing impairments, set to 0 if it is unsuitable for users with hearing impairments. 8.1.4.1.8. FlagVisualImpaired Element name: FlagVisualImpaired path: \Segment\Tracks\TrackEntry\FlagVisualImpaired id: 0x55AC maxOccurs: 1 range: 0-1 type: uinteger minver: 4 definition: Set to 1 if that track is suitable for users with visual impairments, set to 0 if it is unsuitable for users with visual impairments. 8.1.4.1.9. FlagTextDescriptions Element name: FlagTextDescriptions path: \Segment\Tracks\TrackEntry\FlagTextDescriptions id: 0x55AD Lhomme, et al. Expires 12 April 2022 [Page 37] Internet-Draft Matroska Format October 2021 maxOccurs: 1 range: 0-1 type: uinteger minver: 4 definition: Set to 1 if that track contains textual descriptions of video content, set to 0 if that track does not contain textual descriptions of video content. 8.1.4.1.10. FlagOriginal Element name: FlagOriginal path: \Segment\Tracks\TrackEntry\FlagOriginal id: 0x55AE maxOccurs: 1 range: 0-1 type: uinteger minver: 4 definition: Set to 1 if that track is in the content's original language, set to 0 if it is a translation. 8.1.4.1.11. FlagCommentary Element name: FlagCommentary path: \Segment\Tracks\TrackEntry\FlagCommentary id: 0x55AF maxOccurs: 1 range: 0-1 type: uinteger minver: 4 definition: Set to 1 if that track contains commentary, set to 0 if Lhomme, et al. Expires 12 April 2022 [Page 38] Internet-Draft Matroska Format October 2021 it does not contain commentary. 8.1.4.1.12. FlagLacing Element name: FlagLacing path: \Segment\Tracks\TrackEntry\FlagLacing id: 0x9C minOccurs: 1 maxOccurs: 1 range: 0-1 default: 1 type: uinteger definition: Set to 1 if the track MAY contain blocks using lacing. 8.1.4.1.13. MinCache Element name: MinCache path: \Segment\Tracks\TrackEntry\MinCache id: 0x6DE7 minOccurs: 1 maxOccurs: 1 default: 0 type: uinteger definition: The minimum number of frames a player SHOULD be able to cache during playback. If set to 0, the reference pseudo-cache system is not used. 8.1.4.1.14. MaxCache Element name: MaxCache path: \Segment\Tracks\TrackEntry\MaxCache Lhomme, et al. Expires 12 April 2022 [Page 39] Internet-Draft Matroska Format October 2021 id: 0x6DF8 maxOccurs: 1 type: uinteger definition: The maximum cache size necessary to store referenced frames in and the current frame. 0 means no cache is needed. 8.1.4.1.15. DefaultDuration Element name: DefaultDuration path: \Segment\Tracks\TrackEntry\DefaultDuration id: 0x23E383 maxOccurs: 1 range: not 0 type: uinteger definition: Number of nanoseconds (not scaled via TimestampScale) per frame (frame in the Matroska sense -- one Element put into a (Simple)Block). 8.1.4.1.16. DefaultDecodedFieldDuration Element name: DefaultDecodedFieldDuration path: \Segment\Tracks\TrackEntry\DefaultDecodedFieldDuration id: 0x234E7A maxOccurs: 1 range: not 0 type: uinteger minver: 4 definition: The period in nanoseconds (not scaled by TimestampScale) between two successive fields at the output of the decoding process, see Section 11 for more information Lhomme, et al. Expires 12 April 2022 [Page 40] Internet-Draft Matroska Format October 2021 8.1.4.1.17. TrackTimestampScale Element name: TrackTimestampScale path: \Segment\Tracks\TrackEntry\TrackTimestampScale id: 0x23314F minOccurs: 1 maxOccurs: 1 range: > 0x0p+0 default: 0x1p+0 type: float maxver: 3 definition: DEPRECATED, DO NOT USE. The scale to apply on this track to work at normal speed in relation with other tracks (mostly used to adjust video speed when the audio length differs). 8.1.4.1.18. MaxBlockAdditionID Element name: MaxBlockAdditionID path: \Segment\Tracks\TrackEntry\MaxBlockAdditionID id: 0x55EE minOccurs: 1 maxOccurs: 1 default: 0 type: uinteger definition: The maximum value of BlockAddID (Section 8.1.3.5.2.2). A value 0 means there is no BlockAdditions (Section 8.1.3.5.2) for this track. 8.1.4.1.19. BlockAdditionMapping Element name: BlockAdditionMapping Lhomme, et al. Expires 12 April 2022 [Page 41] Internet-Draft Matroska Format October 2021 path: \Segment\Tracks\TrackEntry\BlockAdditionMapping id: 0x41E4 type: master minver: 4 definition: Contains elements that extend the track format, by adding content either to each frame, with BlockAddID (Section 8.1.3.5.2.2), or to the track as a whole with BlockAddIDExtraData. 8.1.4.1.19.1. BlockAddIDValue Element name: BlockAddIDValue path: \Segment\Tracks\TrackEntry\BlockAdditionMapping\BlockAddIDValu e id: 0x41F0 maxOccurs: 1 range: >=2 type: uinteger minver: 4 definition: If the track format extension needs content beside frames, the value refers to the BlockAddID (Section 8.1.3.5.2.2), value being described. To keep MaxBlockAdditionID as low as possible, small values SHOULD be used. 8.1.4.1.19.2. BlockAddIDName Element name: BlockAddIDName path: \Segment\Tracks\TrackEntry\BlockAdditionMapping\BlockAddIDName id: 0x41A4 maxOccurs: 1 type: string minver: 4 Lhomme, et al. Expires 12 April 2022 [Page 42] Internet-Draft Matroska Format October 2021 definition: A human-friendly name describing the type of BlockAdditional data, as defined by the associated Block Additional Mapping. 8.1.4.1.19.3. BlockAddIDType Element name: BlockAddIDType path: \Segment\Tracks\TrackEntry\BlockAdditionMapping\BlockAddIDType id: 0x41E7 minOccurs: 1 maxOccurs: 1 default: 0 type: uinteger minver: 4 definition: Stores the registered identifier of the Block Additional Mapping to define how the BlockAdditional data should be handled. 8.1.4.1.19.4. BlockAddIDExtraData Element name: BlockAddIDExtraData path: \Segment\Tracks\TrackEntry\BlockAdditionMapping\BlockAddIDExtr aData id: 0x41ED maxOccurs: 1 type: binary minver: 4 definition: Extra binary data that the BlockAddIDType can use to interpret the BlockAdditional data. The interpretation of the binary data depends on the BlockAddIDType value and the corresponding Block Additional Mapping. Lhomme, et al. Expires 12 April 2022 [Page 43] Internet-Draft Matroska Format October 2021 8.1.4.1.20. Name Element name: Name path: \Segment\Tracks\TrackEntry\Name id: 0x536E maxOccurs: 1 type: utf-8 definition: A human-readable track name. 8.1.4.1.21. Language Element name: Language path: \Segment\Tracks\TrackEntry\Language id: 0x22B59C minOccurs: 1 maxOccurs: 1 default: eng type: string definition: Specifies the language of the track in the Matroska languages form; see Section 6 on language codes. This Element MUST be ignored if the LanguageIETF Element is used in the same TrackEntry. 8.1.4.1.22. LanguageIETF Element name: LanguageIETF path: \Segment\Tracks\TrackEntry\LanguageIETF id: 0x22B59D maxOccurs: 1 type: string minver: 4 Lhomme, et al. Expires 12 April 2022 [Page 44] Internet-Draft Matroska Format October 2021 definition: Specifies the language of the track according to [BCP47] and using the IANA Language Subtag Registry [IANALangRegistry]. If this Element is used, then any Language Elements used in the same TrackEntry MUST be ignored. 8.1.4.1.23. CodecID Element name: CodecID path: \Segment\Tracks\TrackEntry\CodecID id: 0x86 minOccurs: 1 maxOccurs: 1 type: string definition: An ID corresponding to the codec, see [MatroskaCodec] for more info. 8.1.4.1.24. CodecPrivate Element name: CodecPrivate path: \Segment\Tracks\TrackEntry\CodecPrivate id: 0x63A2 maxOccurs: 1 type: binary definition: Private data only known to the codec. 8.1.4.1.25. CodecName Element name: CodecName path: \Segment\Tracks\TrackEntry\CodecName id: 0x258688 maxOccurs: 1 type: utf-8 Lhomme, et al. Expires 12 April 2022 [Page 45] Internet-Draft Matroska Format October 2021 definition: A human-readable string specifying the codec. 8.1.4.1.26. AttachmentLink Element name: AttachmentLink path: \Segment\Tracks\TrackEntry\AttachmentLink id: 0x7446 maxOccurs: 1 range: not 0 type: uinteger maxver: 3 definition: The UID of an attachment that is used by this codec. 8.1.4.1.27. TrackOverlay Element name: TrackOverlay path: \Segment\Tracks\TrackEntry\TrackOverlay id: 0x6FAB type: uinteger definition: Specify that this track is an overlay track for the Track specified (in the u-integer). That means when this track has a gap, see Section 26.3.1 on SilentTracks, the overlay track SHOULD be used instead. The order of multiple TrackOverlay matters, the first one is the one that SHOULD be used. If not found it SHOULD be the second, etc. 8.1.4.1.28. CodecDelay Element name: CodecDelay path: \Segment\Tracks\TrackEntry\CodecDelay id: 0x56AA maxOccurs: 1 type: uinteger Lhomme, et al. Expires 12 April 2022 [Page 46] Internet-Draft Matroska Format October 2021 minver: 4 definition: CodecDelay is The codec-built-in delay in nanoseconds. This value MUST be subtracted from each block timestamp in order to get the actual timestamp. The value SHOULD be small so the muxing of tracks with the same actual timestamp are in the same Cluster. 8.1.4.1.29. SeekPreRoll Element name: SeekPreRoll path: \Segment\Tracks\TrackEntry\SeekPreRoll id: 0x56BB minOccurs: 1 maxOccurs: 1 default: 0 type: uinteger minver: 4 definition: After a discontinuity, SeekPreRoll is the duration in nanoseconds of the data the decoder MUST decode before the decoded data is valid. 8.1.4.1.30. TrackTranslate Element name: TrackTranslate path: \Segment\Tracks\TrackEntry\TrackTranslate id: 0x6624 type: master definition: The track identification for the given Chapter Codec. 8.1.4.1.30.1. TrackTranslateEditionUID Element name: TrackTranslateEditionUID path: \Segment\Tracks\TrackEntry\TrackTranslate\TrackTranslateEditio nUID Lhomme, et al. Expires 12 April 2022 [Page 47] Internet-Draft Matroska Format October 2021 id: 0x66FC type: uinteger definition: Specify an edition UID on which this translation applies. When not specified, it means for all editions found in the Segment. 8.1.4.1.30.2. TrackTranslateCodec Element name: TrackTranslateCodec path: \Segment\Tracks\TrackEntry\TrackTranslate\TrackTranslateCodec id: 0x66BF minOccurs: 1 maxOccurs: 1 type: uinteger definition: The chapter codec; see Section 8.1.7.1.4.15. restrictions: +=======+=================+ | value | label | +=======+=================+ | 0 | Matroska Script | +-------+-----------------+ | 1 | DVD-menu | +-------+-----------------+ Table 4: TrackTranslateCodec values 8.1.4.1.30.3. TrackTranslateTrackID Element name: TrackTranslateTrackID path: \Segment\Tracks\TrackEntry\TrackTranslate\TrackTranslateTrackI D id: 0x66A5 minOccurs: 1 Lhomme, et al. Expires 12 April 2022 [Page 48] Internet-Draft Matroska Format October 2021 maxOccurs: 1 type: binary definition: The binary value used to represent this track in the chapter codec data. The format depends on the ChapProcessCodecID used; see Section 8.1.7.1.4.15. 8.1.4.1.31. Video Element name: Video path: \Segment\Tracks\TrackEntry\Video id: 0xE0 maxOccurs: 1 type: master definition: Video settings. 8.1.4.1.31.1. FlagInterlaced Element name: FlagInterlaced path: \Segment\Tracks\TrackEntry\Video\FlagInterlaced id: 0x9A minOccurs: 1 maxOccurs: 1 default: 0 type: uinteger minver: 2 definition: Specify whether the video frames in this track are interlaced or not. defined values: Lhomme, et al. Expires 12 April 2022 [Page 49] Internet-Draft Matroska Format October 2021 +=======+==============+==========================+ | value | label | definition | +=======+==============+==========================+ | 0 | undetermined | Unknown status.This | | | | value SHOULD be avoided. | +-------+--------------+--------------------------+ | 1 | interlaced | Interlaced frames. | +-------+--------------+--------------------------+ | 2 | progressive | No interlacing. | +-------+--------------+--------------------------+ Table 5: FlagInterlaced values 8.1.4.1.31.2. FieldOrder Element name: FieldOrder path: \Segment\Tracks\TrackEntry\Video\FieldOrder id: 0x9D minOccurs: 1 maxOccurs: 1 default: 2 type: uinteger minver: 4 definition: Specify the field ordering of video frames in this track. usage notes: If FlagInterlaced is not set to 1, this Element MUST be ignored. defined values: Lhomme, et al. Expires 12 April 2022 [Page 50] Internet-Draft Matroska Format October 2021 +===============+==============+====================================+ | value | label | definition | +===============+==============+====================================+ | 0 | progressive | Interlaced frames.This | | | | value SHOULD be avoided, | | | | setting FlagInterlaced | | | | to 2 is sufficient. | +---------------+--------------+------------------------------------+ | 1 | tff | Top field displayed | | | | first. Top field stored | | | | first. | +---------------+--------------+------------------------------------+ | 2 | undetermined | Unknown field order.This | | | | value SHOULD be avoided. | +---------------+--------------+------------------------------------+ | 6 | bff | Bottom field displayed | | | | first. Bottom field | | | | stored first. | +---------------+--------------+------------------------------------+ | 9 | bff(swapped) | Top field displayed | | | | first. Fields are | | | | interleaved in storage | +---------------+--------------+------------------------------------+ | with the top | | | | line of the | | | | top field | | | | stored first. | | | +---------------+--------------+------------------------------------+ | 14 | tff(swapped) | Bottom field displayed | | | | first. Fields are | | | | interleaved in storage | +---------------+--------------+------------------------------------+ | with the top | | | | line of the | | | | top field | | | | stored first. | | | +---------------+--------------+------------------------------------+ Table 6: FieldOrder values 8.1.4.1.31.3. StereoMode Element name: StereoMode path: \Segment\Tracks\TrackEntry\Video\StereoMode id: 0x53B8 Lhomme, et al. Expires 12 April 2022 [Page 51] Internet-Draft Matroska Format October 2021 minOccurs: 1 maxOccurs: 1 default: 0 type: uinteger minver: 3 definition: Stereo-3D video mode. There are some more details in Section 20.10. restrictions: Lhomme, et al. Expires 12 April 2022 [Page 52] Internet-Draft Matroska Format October 2021 +=======+===================================================+ | value | label | +=======+===================================================+ | 0 | mono | +-------+---------------------------------------------------+ | 1 | side by side (left eye first) | +-------+---------------------------------------------------+ | 2 | top - bottom (right eye is first) | +-------+---------------------------------------------------+ | 3 | top - bottom (left eye is first) | +-------+---------------------------------------------------+ | 4 | checkboard (right eye is first) | +-------+---------------------------------------------------+ | 5 | checkboard (left eye is first) | +-------+---------------------------------------------------+ | 6 | row interleaved (right eye is first) | +-------+---------------------------------------------------+ | 7 | row interleaved (left eye is first) | +-------+---------------------------------------------------+ | 8 | column interleaved (right eye is first) | +-------+---------------------------------------------------+ | 9 | column interleaved (left eye is first) | +-------+---------------------------------------------------+ | 10 | anaglyph (cyan/red) | +-------+---------------------------------------------------+ | 11 | side by side (right eye first) | +-------+---------------------------------------------------+ | 12 | anaglyph (green/magenta) | +-------+---------------------------------------------------+ | 13 | both eyes laced in one Block (left eye is first) | +-------+---------------------------------------------------+ | 14 | both eyes laced in one Block (right eye is first) | +-------+---------------------------------------------------+ Table 7: StereoMode values 8.1.4.1.31.4. AlphaMode Element name: AlphaMode path: \Segment\Tracks\TrackEntry\Video\AlphaMode id: 0x53C0 maxOccurs: 1 default: 0 Lhomme, et al. Expires 12 April 2022 [Page 53] Internet-Draft Matroska Format October 2021 type: uinteger minver: 3 definition: Alpha Video Mode. Presence of this Element indicates that the BlockAdditional Element could contain Alpha data. 8.1.4.1.31.5. PixelWidth Element name: PixelWidth path: \Segment\Tracks\TrackEntry\Video\PixelWidth id: 0xB0 minOccurs: 1 maxOccurs: 1 range: not 0 type: uinteger definition: Width of the encoded video frames in pixels. 8.1.4.1.31.6. PixelHeight Element name: PixelHeight path: \Segment\Tracks\TrackEntry\Video\PixelHeight id: 0xBA minOccurs: 1 maxOccurs: 1 range: not 0 type: uinteger definition: Height of the encoded video frames in pixels. 8.1.4.1.31.7. PixelCropBottom Element name: PixelCropBottom path: \Segment\Tracks\TrackEntry\Video\PixelCropBottom Lhomme, et al. Expires 12 April 2022 [Page 54] Internet-Draft Matroska Format October 2021 id: 0x54AA maxOccurs: 1 default: 0 type: uinteger definition: The number of video pixels to remove at the bottom of the image. 8.1.4.1.31.8. PixelCropTop Element name: PixelCropTop path: \Segment\Tracks\TrackEntry\Video\PixelCropTop id: 0x54BB maxOccurs: 1 default: 0 type: uinteger definition: The number of video pixels to remove at the top of the image. 8.1.4.1.31.9. PixelCropLeft Element name: PixelCropLeft path: \Segment\Tracks\TrackEntry\Video\PixelCropLeft id: 0x54CC maxOccurs: 1 default: 0 type: uinteger definition: The number of video pixels to remove on the left of the image. Lhomme, et al. Expires 12 April 2022 [Page 55] Internet-Draft Matroska Format October 2021 8.1.4.1.31.10. PixelCropRight Element name: PixelCropRight path: \Segment\Tracks\TrackEntry\Video\PixelCropRight id: 0x54DD maxOccurs: 1 default: 0 type: uinteger definition: The number of video pixels to remove on the right of the image. 8.1.4.1.31.11. DisplayWidth Element name: DisplayWidth path: \Segment\Tracks\TrackEntry\Video\DisplayWidth id: 0x54B0 maxOccurs: 1 range: not 0 default: see implementation notes type: uinteger definition: Width of the video frames to display. Applies to the video frame after cropping (PixelCrop* Elements). notes: +===========+=================================================+ | attribute | note | +===========+=================================================+ | default | If the DisplayUnit of the same TrackEntry is 0, | | | then the default value for DisplayWidth is | | | equal toPixelWidth - PixelCropLeft - | | | PixelCropRight, else there is no default value. | +-----------+-------------------------------------------------+ Table 8: DisplayWidth implementation notes Lhomme, et al. Expires 12 April 2022 [Page 56] Internet-Draft Matroska Format October 2021 8.1.4.1.31.12. DisplayHeight Element name: DisplayHeight path: \Segment\Tracks\TrackEntry\Video\DisplayHeight id: 0x54BA maxOccurs: 1 range: not 0 default: see implementation notes type: uinteger definition: Height of the video frames to display. Applies to the video frame after cropping (PixelCrop* Elements). notes: +===========+==================================================+ | attribute | note | +===========+==================================================+ | default | If the DisplayUnit of the same TrackEntry is 0, | | | then the default value for DisplayHeight is | | | equal toPixelHeight - PixelCropTop - | | | PixelCropBottom, else there is no default value. | +-----------+--------------------------------------------------+ Table 9: DisplayHeight implementation notes 8.1.4.1.31.13. DisplayUnit Element name: DisplayUnit path: \Segment\Tracks\TrackEntry\Video\DisplayUnit id: 0x54B2 minOccurs: 1 maxOccurs: 1 default: 0 type: uinteger Lhomme, et al. Expires 12 April 2022 [Page 57] Internet-Draft Matroska Format October 2021 definition: How DisplayWidth & DisplayHeight are interpreted. restrictions: +=======+======================+ | value | label | +=======+======================+ | 0 | pixels | +-------+----------------------+ | 1 | centimeters | +-------+----------------------+ | 2 | inches | +-------+----------------------+ | 3 | display aspect ratio | +-------+----------------------+ | 4 | unknown | +-------+----------------------+ Table 10: DisplayUnit values 8.1.4.1.31.14. ColourSpace Element name: ColourSpace path: \Segment\Tracks\TrackEntry\Video\ColourSpace id: 0x2EB524 minOccurs: see implementation notes maxOccurs: 1 type: binary definition: Specify the pixel format used for the Track's data as a FourCC. This value is similar in scope to the biCompression value of AVI's BITMAPINFOHEADER. notes: Lhomme, et al. Expires 12 April 2022 [Page 58] Internet-Draft Matroska Format October 2021 +===========+============================================+ | attribute | note | +===========+============================================+ | minOccurs | ColourSpace MUST be set (minOccurs=1) in | | | TrackEntry, when the CodecID Element of | | | the TrackEntry is set to "V_UNCOMPRESSED". | +-----------+--------------------------------------------+ Table 11: ColourSpace implementation notes 8.1.4.1.31.15. Colour Element name: Colour path: \Segment\Tracks\TrackEntry\Video\Colour id: 0x55B0 maxOccurs: 1 type: master minver: 4 definition: Settings describing the colour format. 8.1.4.1.31.16. MatrixCoefficients Element name: MatrixCoefficients path: \Segment\Tracks\TrackEntry\Video\Colour\MatrixCoefficients id: 0x55B1 minOccurs: 1 maxOccurs: 1 default: 2 type: uinteger minver: 4 definition: The Matrix Coefficients of the video used to derive luma and chroma values from red, green, and blue color primaries. For clarity, the value and meanings for MatrixCoefficients are adopted from Table 4 of ISO/IEC 23001-8:2016 or ITU-T H.273. Lhomme, et al. Expires 12 April 2022 [Page 59] Internet-Draft Matroska Format October 2021 restrictions: +=======+=======================================+ | value | label | +=======+=======================================+ | 0 | Identity | +-------+---------------------------------------+ | 1 | ITU-R BT.709 | +-------+---------------------------------------+ | 2 | unspecified | +-------+---------------------------------------+ | 3 | reserved | +-------+---------------------------------------+ | 4 | US FCC 73.682 | +-------+---------------------------------------+ | 5 | ITU-R BT.470BG | +-------+---------------------------------------+ | 6 | SMPTE 170M | +-------+---------------------------------------+ | 7 | SMPTE 240M | +-------+---------------------------------------+ | 8 | YCoCg | +-------+---------------------------------------+ | 9 | BT2020 Non-constant Luminance | +-------+---------------------------------------+ | 10 | BT2020 Constant Luminance | +-------+---------------------------------------+ | 11 | SMPTE ST 2085 | +-------+---------------------------------------+ | 12 | Chroma-derived Non-constant Luminance | +-------+---------------------------------------+ | 13 | Chroma-derived Constant Luminance | +-------+---------------------------------------+ | 14 | ITU-R BT.2100-0 | +-------+---------------------------------------+ Table 12: MatrixCoefficients values 8.1.4.1.31.17. BitsPerChannel Element name: BitsPerChannel path: \Segment\Tracks\TrackEntry\Video\Colour\BitsPerChannel id: 0x55B2 maxOccurs: 1 Lhomme, et al. Expires 12 April 2022 [Page 60] Internet-Draft Matroska Format October 2021 default: 0 type: uinteger minver: 4 definition: Number of decoded bits per channel. A value of 0 indicates that the BitsPerChannel is unspecified. 8.1.4.1.31.18. ChromaSubsamplingHorz Element name: ChromaSubsamplingHorz path: \Segment\Tracks\TrackEntry\Video\Colour\ChromaSubsamplingHorz id: 0x55B3 maxOccurs: 1 type: uinteger minver: 4 definition: The amount of pixels to remove in the Cr and Cb channels for every pixel not removed horizontally. Example: For video with 4:2:0 chroma subsampling, the ChromaSubsamplingHorz SHOULD be set to 1. 8.1.4.1.31.19. ChromaSubsamplingVert Element name: ChromaSubsamplingVert path: \Segment\Tracks\TrackEntry\Video\Colour\ChromaSubsamplingVert id: 0x55B4 maxOccurs: 1 type: uinteger minver: 4 definition: The amount of pixels to remove in the Cr and Cb channels for every pixel not removed vertically. Example: For video with 4:2:0 chroma subsampling, the ChromaSubsamplingVert SHOULD be set to 1. Lhomme, et al. Expires 12 April 2022 [Page 61] Internet-Draft Matroska Format October 2021 8.1.4.1.31.20. CbSubsamplingHorz Element name: CbSubsamplingHorz path: \Segment\Tracks\TrackEntry\Video\Colour\CbSubsamplingHorz id: 0x55B5 maxOccurs: 1 type: uinteger minver: 4 definition: The amount of pixels to remove in the Cb channel for every pixel not removed horizontally. This is additive with ChromaSubsamplingHorz. Example: For video with 4:2:1 chroma subsampling, the ChromaSubsamplingHorz SHOULD be set to 1 and CbSubsamplingHorz SHOULD be set to 1. 8.1.4.1.31.21. CbSubsamplingVert Element name: CbSubsamplingVert path: \Segment\Tracks\TrackEntry\Video\Colour\CbSubsamplingVert id: 0x55B6 maxOccurs: 1 type: uinteger minver: 4 definition: The amount of pixels to remove in the Cb channel for every pixel not removed vertically. This is additive with ChromaSubsamplingVert. 8.1.4.1.31.22. ChromaSitingHorz Element name: ChromaSitingHorz path: \Segment\Tracks\TrackEntry\Video\Colour\ChromaSitingHorz id: 0x55B7 minOccurs: 1 Lhomme, et al. Expires 12 April 2022 [Page 62] Internet-Draft Matroska Format October 2021 maxOccurs: 1 default: 0 type: uinteger minver: 4 definition: How chroma is subsampled horizontally. restrictions: +=======+=================+ | value | label | +=======+=================+ | 0 | unspecified | +-------+-----------------+ | 1 | left collocated | +-------+-----------------+ | 2 | half | +-------+-----------------+ Table 13: ChromaSitingHorz values 8.1.4.1.31.23. ChromaSitingVert Element name: ChromaSitingVert path: \Segment\Tracks\TrackEntry\Video\Colour\ChromaSitingVert id: 0x55B8 minOccurs: 1 maxOccurs: 1 default: 0 type: uinteger minver: 4 definition: How chroma is subsampled vertically. restrictions: Lhomme, et al. Expires 12 April 2022 [Page 63] Internet-Draft Matroska Format October 2021 +=======+================+ | value | label | +=======+================+ | 0 | unspecified | +-------+----------------+ | 1 | top collocated | +-------+----------------+ | 2 | half | +-------+----------------+ Table 14: ChromaSitingVert values 8.1.4.1.31.24. Range Element name: Range path: \Segment\Tracks\TrackEntry\Video\Colour\Range id: 0x55B9 minOccurs: 1 maxOccurs: 1 default: 0 type: uinteger minver: 4 definition: Clipping of the color ranges. restrictions: Lhomme, et al. Expires 12 April 2022 [Page 64] Internet-Draft Matroska Format October 2021 +=======+=========================================================+ | value | label | +=======+=========================================================+ | 0 | unspecified | +-------+---------------------------------------------------------+ | 1 | broadcast range | +-------+---------------------------------------------------------+ | 2 | full range (no clipping) | +-------+---------------------------------------------------------+ | 3 | defined by MatrixCoefficients / TransferCharacteristics | +-------+---------------------------------------------------------+ Table 15: Range values 8.1.4.1.31.25. TransferCharacteristics Element name: TransferCharacteristics path: \Segment\Tracks\TrackEntry\Video\Colour\TransferCharacteristic s id: 0x55BA minOccurs: 1 maxOccurs: 1 default: 2 type: uinteger minver: 4 definition: The transfer characteristics of the video. For clarity, the value and meanings for TransferCharacteristics are adopted from Table 3 of ISO/IEC 23091-4 or ITU-T H.273. restrictions: Lhomme, et al. Expires 12 April 2022 [Page 65] Internet-Draft Matroska Format October 2021 +=======+=======================================+ | value | label | +=======+=======================================+ | 0 | reserved | +-------+---------------------------------------+ | 1 | ITU-R BT.709 | +-------+---------------------------------------+ | 2 | unspecified | +-------+---------------------------------------+ | 3 | reserved | +-------+---------------------------------------+ | 4 | Gamma 2.2 curve - BT.470M | +-------+---------------------------------------+ | 5 | Gamma 2.8 curve - BT.470BG | +-------+---------------------------------------+ | 6 | SMPTE 170M | +-------+---------------------------------------+ | 7 | SMPTE 240M | +-------+---------------------------------------+ | 8 | Linear | +-------+---------------------------------------+ | 9 | Log | +-------+---------------------------------------+ | 10 | Log Sqrt | +-------+---------------------------------------+ | 11 | IEC 61966-2-4 | +-------+---------------------------------------+ | 12 | ITU-R BT.1361 Extended Colour Gamut | +-------+---------------------------------------+ | 13 | IEC 61966-2-1 | +-------+---------------------------------------+ | 14 | ITU-R BT.2020 10 bit | +-------+---------------------------------------+ | 15 | ITU-R BT.2020 12 bit | +-------+---------------------------------------+ | 16 | ITU-R BT.2100 Perceptual Quantization | +-------+---------------------------------------+ | 17 | SMPTE ST 428-1 | +-------+---------------------------------------+ | 18 | ARIB STD-B67 (HLG) | +-------+---------------------------------------+ Table 16: TransferCharacteristics values 8.1.4.1.31.26. Primaries Element name: Primaries Lhomme, et al. Expires 12 April 2022 [Page 66] Internet-Draft Matroska Format October 2021 path: \Segment\Tracks\TrackEntry\Video\Colour\Primaries id: 0x55BB minOccurs: 1 maxOccurs: 1 default: 2 type: uinteger minver: 4 definition: The colour primaries of the video. For clarity, the value and meanings for Primaries are adopted from Table 2 of ISO/ IEC 23091-4 or ITU-T H.273. restrictions: Lhomme, et al. Expires 12 April 2022 [Page 67] Internet-Draft Matroska Format October 2021 +=======+========================================+ | value | label | +=======+========================================+ | 0 | reserved | +-------+----------------------------------------+ | 1 | ITU-R BT.709 | +-------+----------------------------------------+ | 2 | unspecified | +-------+----------------------------------------+ | 3 | reserved | +-------+----------------------------------------+ | 4 | ITU-R BT.470M | +-------+----------------------------------------+ | 5 | ITU-R BT.470BG - BT.601 625 | +-------+----------------------------------------+ | 6 | ITU-R BT.601 525 - SMPTE 170M | +-------+----------------------------------------+ | 7 | SMPTE 240M | +-------+----------------------------------------+ | 8 | FILM | +-------+----------------------------------------+ | 9 | ITU-R BT.2020 | +-------+----------------------------------------+ | 10 | SMPTE ST 428-1 | +-------+----------------------------------------+ | 11 | SMPTE RP 432-2 | +-------+----------------------------------------+ | 12 | SMPTE EG 432-2 | +-------+----------------------------------------+ | 22 | EBU Tech. 3213-E - JEDEC P22 phosphors | +-------+----------------------------------------+ Table 17: Primaries values 8.1.4.1.31.27. MaxCLL Element name: MaxCLL path: \Segment\Tracks\TrackEntry\Video\Colour\MaxCLL id: 0x55BC maxOccurs: 1 type: uinteger minver: 4 Lhomme, et al. Expires 12 April 2022 [Page 68] Internet-Draft Matroska Format October 2021 definition: Maximum brightness of a single pixel (Maximum Content Light Level) in candelas per square meter (cd/m^2). 8.1.4.1.31.28. MaxFALL Element name: MaxFALL path: \Segment\Tracks\TrackEntry\Video\Colour\MaxFALL id: 0x55BD maxOccurs: 1 type: uinteger minver: 4 definition: Maximum brightness of a single full frame (Maximum Frame-Average Light Level) in candelas per square meter (cd/m^2). 8.1.4.1.31.29. MasteringMetadata Element name: MasteringMetadata path: \Segment\Tracks\TrackEntry\Video\Colour\MasteringMetadata id: 0x55D0 maxOccurs: 1 type: master minver: 4 definition: SMPTE 2086 mastering data. 8.1.4.1.31.30. PrimaryRChromaticityX Element name: PrimaryRChromaticityX path: \Segment\Tracks\TrackEntry\Video\Colour\MasteringMetadata\Prim aryRChromaticityX id: 0x55D1 maxOccurs: 1 range: 0-1 Lhomme, et al. Expires 12 April 2022 [Page 69] Internet-Draft Matroska Format October 2021 type: float minver: 4 definition: Red X chromaticity coordinate, as defined by CIE 1931. 8.1.4.1.31.31. PrimaryRChromaticityY Element name: PrimaryRChromaticityY path: \Segment\Tracks\TrackEntry\Video\Colour\MasteringMetadata\Prim aryRChromaticityY id: 0x55D2 maxOccurs: 1 range: 0-1 type: float minver: 4 definition: Red Y chromaticity coordinate, as defined by CIE 1931. 8.1.4.1.31.32. PrimaryGChromaticityX Element name: PrimaryGChromaticityX path: \Segment\Tracks\TrackEntry\Video\Colour\MasteringMetadata\Prim aryGChromaticityX id: 0x55D3 maxOccurs: 1 range: 0-1 type: float minver: 4 definition: Green X chromaticity coordinate, as defined by CIE 1931. 8.1.4.1.31.33. PrimaryGChromaticityY Element name: PrimaryGChromaticityY Lhomme, et al. Expires 12 April 2022 [Page 70] Internet-Draft Matroska Format October 2021 path: \Segment\Tracks\TrackEntry\Video\Colour\MasteringMetadata\Prim aryGChromaticityY id: 0x55D4 maxOccurs: 1 range: 0-1 type: float minver: 4 definition: Green Y chromaticity coordinate, as defined by CIE 1931. 8.1.4.1.31.34. PrimaryBChromaticityX Element name: PrimaryBChromaticityX path: \Segment\Tracks\TrackEntry\Video\Colour\MasteringMetadata\Prim aryBChromaticityX id: 0x55D5 maxOccurs: 1 range: 0-1 type: float minver: 4 definition: Blue X chromaticity coordinate, as defined by CIE 1931. 8.1.4.1.31.35. PrimaryBChromaticityY Element name: PrimaryBChromaticityY path: \Segment\Tracks\TrackEntry\Video\Colour\MasteringMetadata\Prim aryBChromaticityY id: 0x55D6 maxOccurs: 1 range: 0-1 type: float Lhomme, et al. Expires 12 April 2022 [Page 71] Internet-Draft Matroska Format October 2021 minver: 4 definition: Blue Y chromaticity coordinate, as defined by CIE 1931. 8.1.4.1.31.36. WhitePointChromaticityX Element name: WhitePointChromaticityX path: \Segment\Tracks\TrackEntry\Video\Colour\MasteringMetadata\Whit ePointChromaticityX id: 0x55D7 maxOccurs: 1 range: 0-1 type: float minver: 4 definition: White X chromaticity coordinate, as defined by CIE 1931. 8.1.4.1.31.37. WhitePointChromaticityY Element name: WhitePointChromaticityY path: \Segment\Tracks\TrackEntry\Video\Colour\MasteringMetadata\Whit ePointChromaticityY id: 0x55D8 maxOccurs: 1 range: 0-1 type: float minver: 4 definition: White Y chromaticity coordinate, as defined by CIE 1931. 8.1.4.1.31.38. LuminanceMax Element name: LuminanceMax path: \Segment\Tracks\TrackEntry\Video\Colour\MasteringMetadata\Lumi nanceMax Lhomme, et al. Expires 12 April 2022 [Page 72] Internet-Draft Matroska Format October 2021 id: 0x55D9 maxOccurs: 1 range: >= 0x0p+0 type: float minver: 4 definition: Maximum luminance. Represented in candelas per square meter (cd/m^2). 8.1.4.1.31.39. LuminanceMin Element name: LuminanceMin path: \Segment\Tracks\TrackEntry\Video\Colour\MasteringMetadata\Lumi nanceMin id: 0x55DA maxOccurs: 1 range: >= 0x0p+0 type: float minver: 4 definition: Minimum luminance. Represented in candelas per square meter (cd/m^2). 8.1.4.1.31.40. Projection Element name: Projection path: \Segment\Tracks\TrackEntry\Video\Projection id: 0x7670 maxOccurs: 1 type: master minver: 4 definition: Describes the video projection details. Used to render Lhomme, et al. Expires 12 April 2022 [Page 73] Internet-Draft Matroska Format October 2021 spherical and VR videos. 8.1.4.1.31.41. ProjectionType Element name: ProjectionType path: \Segment\Tracks\TrackEntry\Video\Projection\ProjectionType id: 0x7671 minOccurs: 1 maxOccurs: 1 default: 0 type: uinteger minver: 4 definition: Describes the projection used for this video track. restrictions: +=======+=================+ | value | label | +=======+=================+ | 0 | rectangular | +-------+-----------------+ | 1 | equirectangular | +-------+-----------------+ | 2 | cubemap | +-------+-----------------+ | 3 | mesh | +-------+-----------------+ Table 18: ProjectionType values 8.1.4.1.31.42. ProjectionPrivate Element name: ProjectionPrivate path: \Segment\Tracks\TrackEntry\Video\Projection\ProjectionPrivate id: 0x7672 maxOccurs: 1 Lhomme, et al. Expires 12 April 2022 [Page 74] Internet-Draft Matroska Format October 2021 type: binary minver: 4 definition: Private data that only applies to a specific projection. * If ProjectionType equals 0 (Rectangular), then this element must not be present. * If ProjectionType equals 1 (Equirectangular), then this element must be present and contain the same binary data that would be stored inside an ISOBMFF Equirectangular Projection Box ('equi'). * If ProjectionType equals 2 (Cubemap), then this element must be present and contain the same binary data that would be stored inside an ISOBMFF Cubemap Projection Box ('cbmp'). * If ProjectionType equals 3 (Mesh), then this element must be present and contain the same binary data that would be stored inside an ISOBMFF Mesh Projection Box ('mshp'). usage notes: ISOBMFF box size and fourcc fields are not included in the binary data, but the FullBox version and flag fields are. This is to avoid redundant framing information while preserving versioning and semantics between the two container formats. 8.1.4.1.31.43. ProjectionPoseYaw Element name: ProjectionPoseYaw path: \Segment\Tracks\TrackEntry\Video\Projection\ProjectionPoseYaw id: 0x7673 minOccurs: 1 maxOccurs: 1 default: 0x0p+0 type: float minver: 4 definition: Specifies a yaw rotation to the projection. Lhomme, et al. Expires 12 April 2022 [Page 75] Internet-Draft Matroska Format October 2021 Value represents a clockwise rotation, in degrees, around the up vector. This rotation must be applied before any ProjectionPosePitch or ProjectionPoseRoll rotations. The value of this field should be in the -180 to 180 degree range. 8.1.4.1.31.44. ProjectionPosePitch Element name: ProjectionPosePitch path: \Segment\Tracks\TrackEntry\Video\Projection\ProjectionPosePitc h id: 0x7674 minOccurs: 1 maxOccurs: 1 default: 0x0p+0 type: float minver: 4 definition: Specifies a pitch rotation to the projection. Value represents a counter-clockwise rotation, in degrees, around the right vector. This rotation must be applied after the ProjectionPoseYaw rotation and before the ProjectionPoseRoll rotation. The value of this field should be in the -90 to 90 degree range. 8.1.4.1.31.45. ProjectionPoseRoll Element name: ProjectionPoseRoll path: \Segment\Tracks\TrackEntry\Video\Projection\ProjectionPoseRoll id: 0x7675 minOccurs: 1 maxOccurs: 1 default: 0x0p+0 type: float Lhomme, et al. Expires 12 April 2022 [Page 76] Internet-Draft Matroska Format October 2021 minver: 4 definition: Specifies a roll rotation to the projection. Value represents a counter-clockwise rotation, in degrees, around the forward vector. This rotation must be applied after the ProjectionPoseYaw and ProjectionPosePitch rotations. The value of this field should be in the -180 to 180 degree range. 8.1.4.1.32. Audio Element name: Audio path: \Segment\Tracks\TrackEntry\Audio id: 0xE1 maxOccurs: 1 type: master definition: Audio settings. 8.1.4.1.32.1. SamplingFrequency Element name: SamplingFrequency path: \Segment\Tracks\TrackEntry\Audio\SamplingFrequency id: 0xB5 minOccurs: 1 maxOccurs: 1 range: > 0x0p+0 default: 0x1.f4p+12 type: float definition: Sampling frequency in Hz. 8.1.4.1.32.2. OutputSamplingFrequency Element name: OutputSamplingFrequency path: \Segment\Tracks\TrackEntry\Audio\OutputSamplingFrequency Lhomme, et al. Expires 12 April 2022 [Page 77] Internet-Draft Matroska Format October 2021 id: 0x78B5 maxOccurs: 1 range: > 0x0p+0 default: see implementation notes type: float definition: Real output sampling frequency in Hz (used for SBR techniques). notes: +===========+======================================================+ | attribute | note | +===========+======================================================+ | default | The default value for OutputSamplingFrequency of the | | | same TrackEntry is equal to the SamplingFrequency. | +-----------+------------------------------------------------------+ Table 19: OutputSamplingFrequency implementation notes 8.1.4.1.32.3. Channels Element name: Channels path: \Segment\Tracks\TrackEntry\Audio\Channels id: 0x9F minOccurs: 1 maxOccurs: 1 range: not 0 default: 1 type: uinteger definition: Numbers of channels in the track. 8.1.4.1.32.4. BitDepth Element name: BitDepth Lhomme, et al. Expires 12 April 2022 [Page 78] Internet-Draft Matroska Format October 2021 path: \Segment\Tracks\TrackEntry\Audio\BitDepth id: 0x6264 maxOccurs: 1 range: not 0 type: uinteger definition: Bits per sample, mostly used for PCM. 8.1.4.1.33. TrackOperation Element name: TrackOperation path: \Segment\Tracks\TrackEntry\TrackOperation id: 0xE2 maxOccurs: 1 type: master minver: 3 definition: Operation that needs to be applied on tracks to create this virtual track. For more details look at Section 20.8. 8.1.4.1.33.1. TrackCombinePlanes Element name: TrackCombinePlanes path: \Segment\Tracks\TrackEntry\TrackOperation\TrackCombinePlanes id: 0xE3 maxOccurs: 1 type: master minver: 3 definition: Contains the list of all video plane tracks that need to be combined to create this 3D track Lhomme, et al. Expires 12 April 2022 [Page 79] Internet-Draft Matroska Format October 2021 8.1.4.1.33.2. TrackPlane Element name: TrackPlane path: \Segment\Tracks\TrackEntry\TrackOperation\TrackCombinePlanes\T rackPlane id: 0xE4 minOccurs: 1 type: master minver: 3 definition: Contains a video plane track that need to be combined to create this 3D track 8.1.4.1.33.3. TrackPlaneUID Element name: TrackPlaneUID path: \Segment\Tracks\TrackEntry\TrackOperation\TrackCombinePlanes\T rackPlane\TrackPlaneUID id: 0xE5 minOccurs: 1 maxOccurs: 1 range: not 0 type: uinteger minver: 3 definition: The trackUID number of the track representing the plane. 8.1.4.1.33.4. TrackPlaneType Element name: TrackPlaneType path: \Segment\Tracks\TrackEntry\TrackOperation\TrackCombinePlanes\T rackPlane\TrackPlaneType id: 0xE6 Lhomme, et al. Expires 12 April 2022 [Page 80] Internet-Draft Matroska Format October 2021 minOccurs: 1 maxOccurs: 1 type: uinteger minver: 3 definition: The kind of plane this track corresponds to. restrictions: +=======+============+ | value | label | +=======+============+ | 0 | left eye | +-------+------------+ | 1 | right eye | +-------+------------+ | 2 | background | +-------+------------+ Table 20: TrackPlaneType values 8.1.4.1.33.5. TrackJoinBlocks Element name: TrackJoinBlocks path: \Segment\Tracks\TrackEntry\TrackOperation\TrackJoinBlocks id: 0xE9 maxOccurs: 1 type: master minver: 3 definition: Contains the list of all tracks whose Blocks need to be combined to create this virtual track 8.1.4.1.33.6. TrackJoinUID Element name: TrackJoinUID path: \Segment\Tracks\TrackEntry\TrackOperation\TrackJoinBlocks\Trac kJoinUID Lhomme, et al. Expires 12 April 2022 [Page 81] Internet-Draft Matroska Format October 2021 id: 0xED minOccurs: 1 range: not 0 type: uinteger minver: 3 definition: The trackUID number of a track whose blocks are used to create this virtual track. 8.1.4.1.34. ContentEncodings Element name: ContentEncodings path: \Segment\Tracks\TrackEntry\ContentEncodings id: 0x6D80 maxOccurs: 1 type: master definition: Settings for several content encoding mechanisms like compression or encryption. 8.1.4.1.34.1. ContentEncoding Element name: ContentEncoding path: \Segment\Tracks\TrackEntry\ContentEncodings\ContentEncoding id: 0x6240 minOccurs: 1 type: master definition: Settings for one content encoding like compression or encryption. 8.1.4.1.34.2. ContentEncodingOrder Element name: ContentEncodingOrder path: \Segment\Tracks\TrackEntry\ContentEncodings\ContentEncoding\Co Lhomme, et al. Expires 12 April 2022 [Page 82] Internet-Draft Matroska Format October 2021 ntentEncodingOrder id: 0x5031 minOccurs: 1 maxOccurs: 1 default: 0 type: uinteger definition: Tells when this modification was used during encoding/ muxing starting with 0 and counting upwards. The decoder/demuxer has to start with the highest order number it finds and work its way down. This value has to be unique over all ContentEncodingOrder Elements in the TrackEntry that contains this ContentEncodingOrder element. 8.1.4.1.34.3. ContentEncodingScope Element name: ContentEncodingScope path: \Segment\Tracks\TrackEntry\ContentEncodings\ContentEncoding\Co ntentEncodingScope id: 0x5032 minOccurs: 1 maxOccurs: 1 default: 1 type: uinteger definition: A bit field that describes which Elements have been modified in this way. Values (big-endian) can be OR'ed. restrictions: Lhomme, et al. Expires 12 April 2022 [Page 83] Internet-Draft Matroska Format October 2021 +=======+===============================================+ | value | label | +=======+===============================================+ | 1 | All frame contents, excluding lacing data | +-------+-----------------------------------------------+ | 2 | The track's private data | +-------+-----------------------------------------------+ | 4 | The next ContentEncoding (next | | | ContentEncodingOrder. Either the data inside | | | ContentCompression and/or ContentEncryption) | +-------+-----------------------------------------------+ Table 21: ContentEncodingScope values 8.1.4.1.34.4. ContentEncodingType Element name: ContentEncodingType path: \Segment\Tracks\TrackEntry\ContentEncodings\ContentEncoding\Co ntentEncodingType id: 0x5033 minOccurs: 1 maxOccurs: 1 default: 0 type: uinteger definition: A value describing what kind of transformation is applied. restrictions: +=======+=============+ | value | label | +=======+=============+ | 0 | Compression | +-------+-------------+ | 1 | Encryption | +-------+-------------+ Table 22: ContentEncodingType values Lhomme, et al. Expires 12 April 2022 [Page 84] Internet-Draft Matroska Format October 2021 8.1.4.1.34.5. ContentCompression Element name: ContentCompression path: \Segment\Tracks\TrackEntry\ContentEncodings\ContentEncoding\Co ntentCompression id: 0x5034 maxOccurs: 1 type: master definition: Settings describing the compression used. This Element MUST be present if the value of ContentEncodingType is 0 and absent otherwise. Each block MUST be decompressable even if no previous block is available in order not to prevent seeking. 8.1.4.1.34.6. ContentCompAlgo Element name: ContentCompAlgo path: \Segment\Tracks\TrackEntry\ContentEncodings\ContentEncoding\Co ntentCompression\ContentCompAlgo id: 0x4254 minOccurs: 1 maxOccurs: 1 default: 0 type: uinteger definition: The compression algorithm used. defined values: Lhomme, et al. Expires 12 April 2022 [Page 85] Internet-Draft Matroska Format October 2021 +=======+===========+======================================+ | value | label | definition | +=======+===========+======================================+ | 0 | zlib | zlib compression [RFC1950]. | +-------+-----------+--------------------------------------+ | 1 | bzlib | bzip2 compression [BZIP2]. | +-------+-----------+--------------------------------------+ | 2 | lzo1x | Lempel– (U+2013)Ziv– | | | | (U+2013)Oberhumer compression [LZO]. | +-------+-----------+--------------------------------------+ | 3 | Header | Octets in ContentCompSettings | | | Stripping | (Section 8.1.4.1.34.7) have been | | | | stripped from each frame. | +-------+-----------+--------------------------------------+ Table 23: ContentCompAlgo values 8.1.4.1.34.7. ContentCompSettings Element name: ContentCompSettings path: \Segment\Tracks\TrackEntry\ContentEncodings\ContentEncoding\Co ntentCompression\ContentCompSettings id: 0x4255 maxOccurs: 1 type: binary definition: Settings that might be needed by the decompressor. For Header Stripping (ContentCompAlgo=3), the bytes that were removed from the beginning of each frames of the track. 8.1.4.1.34.8. ContentEncryption Element name: ContentEncryption path: \Segment\Tracks\TrackEntry\ContentEncodings\ContentEncoding\Co ntentEncryption id: 0x5035 maxOccurs: 1 type: master definition: Settings describing the encryption used. This Element Lhomme, et al. Expires 12 April 2022 [Page 86] Internet-Draft Matroska Format October 2021 MUST be present if the value of ContentEncodingType is 1 (encryption) and MUST be ignored otherwise. 8.1.4.1.34.9. ContentEncAlgo Element name: ContentEncAlgo path: \Segment\Tracks\TrackEntry\ContentEncodings\ContentEncoding\Co ntentEncryption\ContentEncAlgo id: 0x47E1 minOccurs: 1 maxOccurs: 1 default: 0 type: uinteger definition: The encryption algorithm used. The value "0" means that the contents have not been encrypted. defined values: +=======+===============+============================+ | value | label | definition | +=======+===============+============================+ | 0 | Not encrypted | | +-------+---------------+----------------------------+ | 1 | DES | Data Encryption Standard | | | | (DES) [FIPS.46-3]. | +-------+---------------+----------------------------+ | 2 | 3DES | Triple Data Encryption | | | | Algorithm [RFC1851]. | +-------+---------------+----------------------------+ | 3 | Twofish | Twofish Encryption | | | | Algorithm [Twofish]. | +-------+---------------+----------------------------+ | 4 | Blowfish | Blowfish Encryption | | | | Algorithm [Blowfish]. | +-------+---------------+----------------------------+ | 5 | AES | Advanced Encryption | | | | Standard (AES) [FIPS.197]. | +-------+---------------+----------------------------+ Table 24: ContentEncAlgo values Lhomme, et al. Expires 12 April 2022 [Page 87] Internet-Draft Matroska Format October 2021 8.1.4.1.34.10. ContentEncKeyID Element name: ContentEncKeyID path: \Segment\Tracks\TrackEntry\ContentEncodings\ContentEncoding\Co ntentEncryption\ContentEncKeyID id: 0x47E2 maxOccurs: 1 type: binary definition: For public key algorithms this is the ID of the public key the the data was encrypted with. 8.1.4.1.34.11. ContentEncAESSettings Element name: ContentEncAESSettings path: \Segment\Tracks\TrackEntry\ContentEncodings\ContentEncoding\Co ntentEncryption\ContentEncAESSettings id: 0x47E7 maxOccurs: 1 type: master minver: 4 definition: Settings describing the encryption algorithm used. If ContentEncAlgo != 5 this MUST be ignored. 8.1.4.1.34.12. AESSettingsCipherMode Element name: AESSettingsCipherMode path: \Segment\Tracks\TrackEntry\ContentEncodings\ContentEncoding\Co ntentEncryption\ContentEncAESSettings\AESSettingsCipherMode id: 0x47E8 minOccurs: 1 maxOccurs: 1 type: uinteger Lhomme, et al. Expires 12 April 2022 [Page 88] Internet-Draft Matroska Format October 2021 minver: 4 definition: The AES cipher mode used in the encryption. restrictions: +=======+==================================================+ | value | label | +=======+==================================================+ | 1 | AES-CTR / Counter, NIST SP 800-38A | +-------+--------------------------------------------------+ | 2 | AES-CBC / Cipher Block Chaining, NIST SP 800-38A | +-------+--------------------------------------------------+ Table 25: AESSettingsCipherMode values 8.1.5. Cues Element name: Cues path: \Segment\Cues id: 0x1C53BB6B minOccurs: see implementation notes maxOccurs: 1 type: master definition: A Top-Level Element to speed seeking access. All entries are local to the Segment. notes: +===========+====================================================+ | attribute | note | +===========+====================================================+ | minOccurs | This Element SHOULD be set when the Segment is not | | | transmitted as a live stream (see #livestreaming). | +-----------+----------------------------------------------------+ Table 26: Cues implementation notes 8.1.5.1. CuePoint Element name: CuePoint Lhomme, et al. Expires 12 April 2022 [Page 89] Internet-Draft Matroska Format October 2021 path: \Segment\Cues\CuePoint id: 0xBB minOccurs: 1 type: master definition: Contains all information relative to a seek point in the Segment. 8.1.5.1.1. CueTime Element name: CueTime path: \Segment\Cues\CuePoint\CueTime id: 0xB3 minOccurs: 1 maxOccurs: 1 type: uinteger definition: Absolute timestamp according to the Segment time base. 8.1.5.1.2. CueTrackPositions Element name: CueTrackPositions path: \Segment\Cues\CuePoint\CueTrackPositions id: 0xB7 minOccurs: 1 type: master definition: Contain positions for different tracks corresponding to the timestamp. 8.1.5.1.2.1. CueTrack Element name: CueTrack path: \Segment\Cues\CuePoint\CueTrackPositions\CueTrack Lhomme, et al. Expires 12 April 2022 [Page 90] Internet-Draft Matroska Format October 2021 id: 0xF7 minOccurs: 1 maxOccurs: 1 range: not 0 type: uinteger definition: The track for which a position is given. 8.1.5.1.2.2. CueClusterPosition Element name: CueClusterPosition path: \Segment\Cues\CuePoint\CueTrackPositions\CueClusterPosition id: 0xF1 minOccurs: 1 maxOccurs: 1 type: uinteger definition: The Segment Position of the Cluster containing the associated Block. 8.1.5.1.2.3. CueRelativePosition Element name: CueRelativePosition path: \Segment\Cues\CuePoint\CueTrackPositions\CueRelativePosition id: 0xF0 maxOccurs: 1 type: uinteger minver: 4 definition: The relative position inside the Cluster of the referenced SimpleBlock or BlockGroup with 0 being the first possible position for an Element inside that Cluster. Lhomme, et al. Expires 12 April 2022 [Page 91] Internet-Draft Matroska Format October 2021 8.1.5.1.2.4. CueDuration Element name: CueDuration path: \Segment\Cues\CuePoint\CueTrackPositions\CueDuration id: 0xB2 maxOccurs: 1 type: uinteger minver: 4 definition: The duration of the block according to the Segment time base. If missing the track's DefaultDuration does not apply and no duration information is available in terms of the cues. 8.1.5.1.2.5. CueBlockNumber Element name: CueBlockNumber path: \Segment\Cues\CuePoint\CueTrackPositions\CueBlockNumber id: 0x5378 maxOccurs: 1 range: not 0 type: uinteger definition: Number of the Block in the specified Cluster. 8.1.5.1.2.6. CueCodecState Element name: CueCodecState path: \Segment\Cues\CuePoint\CueTrackPositions\CueCodecState id: 0xEA maxOccurs: 1 default: 0 type: uinteger Lhomme, et al. Expires 12 April 2022 [Page 92] Internet-Draft Matroska Format October 2021 minver: 2 definition: The Segment Position of the Codec State corresponding to this Cue Element. 0 means that the data is taken from the initial Track Entry. 8.1.5.1.2.7. CueReference Element name: CueReference path: \Segment\Cues\CuePoint\CueTrackPositions\CueReference id: 0xDB type: master minver: 2 definition: The Clusters containing the referenced Blocks. 8.1.5.1.2.8. CueRefTime Element name: CueRefTime path: \Segment\Cues\CuePoint\CueTrackPositions\CueReference\CueRefTi me id: 0x96 minOccurs: 1 maxOccurs: 1 type: uinteger minver: 2 definition: Timestamp of the referenced Block. 8.1.6. Attachments Element name: Attachments path: \Segment\Attachments id: 0x1941A469 maxOccurs: 1 Lhomme, et al. Expires 12 April 2022 [Page 93] Internet-Draft Matroska Format October 2021 type: master definition: Contain attached files. 8.1.6.1. AttachedFile Element name: AttachedFile path: \Segment\Attachments\AttachedFile id: 0x61A7 minOccurs: 1 type: master definition: An attached file. 8.1.6.1.1. FileDescription Element name: FileDescription path: \Segment\Attachments\AttachedFile\FileDescription id: 0x467E maxOccurs: 1 type: utf-8 definition: A human-friendly name for the attached file. 8.1.6.1.2. FileName Element name: FileName path: \Segment\Attachments\AttachedFile\FileName id: 0x466E minOccurs: 1 maxOccurs: 1 type: utf-8 definition: Filename of the attached file. Lhomme, et al. Expires 12 April 2022 [Page 94] Internet-Draft Matroska Format October 2021 8.1.6.1.3. FileMimeType Element name: FileMimeType path: \Segment\Attachments\AttachedFile\FileMimeType id: 0x4660 minOccurs: 1 maxOccurs: 1 type: string definition: MIME type of the file. 8.1.6.1.4. FileData Element name: FileData path: \Segment\Attachments\AttachedFile\FileData id: 0x465C minOccurs: 1 maxOccurs: 1 type: binary definition: The data of the file. 8.1.6.1.5. FileUID Element name: FileUID path: \Segment\Attachments\AttachedFile\FileUID id: 0x46AE minOccurs: 1 maxOccurs: 1 range: not 0 type: uinteger Lhomme, et al. Expires 12 April 2022 [Page 95] Internet-Draft Matroska Format October 2021 definition: Unique ID representing the file, as random as possible. 8.1.7. Chapters Element name: Chapters path: \Segment\Chapters id: 0x1043A770 maxOccurs: 1 type: master recurring: 1 definition: A system to define basic menus and partition data. For more detailed information, look at the Chapters explanation in Section 22. 8.1.7.1. EditionEntry Element name: EditionEntry path: \Segment\Chapters\EditionEntry id: 0x45B9 minOccurs: 1 type: master definition: Contains all information about a Segment edition. 8.1.7.1.1. EditionUID Element name: EditionUID path: \Segment\Chapters\EditionEntry\EditionUID id: 0x45BC maxOccurs: 1 range: not 0 type: uinteger Lhomme, et al. Expires 12 April 2022 [Page 96] Internet-Draft Matroska Format October 2021 definition: A unique ID to identify the edition. It's useful for tagging an edition. 8.1.7.1.2. EditionFlagDefault Element name: EditionFlagDefault path: \Segment\Chapters\EditionEntry\EditionFlagDefault id: 0x45DB minOccurs: 1 maxOccurs: 1 range: 0-1 default: 0 type: uinteger definition: Set to 1 if the edition SHOULD be used as the default one. 8.1.7.1.3. EditionFlagOrdered Element name: EditionFlagOrdered path: \Segment\Chapters\EditionEntry\EditionFlagOrdered id: 0x45DD minOccurs: 1 maxOccurs: 1 range: 0-1 default: 0 type: uinteger definition: Set to 1 if the chapters can be defined multiple times and the order to play them is enforced; see Section 22.1.3. Lhomme, et al. Expires 12 April 2022 [Page 97] Internet-Draft Matroska Format October 2021 8.1.7.1.4. ChapterAtom Element name: ChapterAtom path: \Segment\Chapters\EditionEntry\+ChapterAtom id: 0xB6 minOccurs: 1 type: master recursive: 1 definition: Contains the atom information to use as the chapter atom (apply to all tracks). 8.1.7.1.4.1. ChapterUID Element name: ChapterUID path: \Segment\Chapters\EditionEntry\+ChapterAtom\ChapterUID id: 0x73C4 minOccurs: 1 maxOccurs: 1 range: not 0 type: uinteger definition: A unique ID to identify the Chapter. 8.1.7.1.4.2. ChapterStringUID Element name: ChapterStringUID path: \Segment\Chapters\EditionEntry\+ChapterAtom\ChapterStringUID id: 0x5654 maxOccurs: 1 type: utf-8 minver: 3 Lhomme, et al. Expires 12 April 2022 [Page 98] Internet-Draft Matroska Format October 2021 definition: A unique string ID to identify the Chapter. Use for WebVTT cue identifier storage [WebVTT]. 8.1.7.1.4.3. ChapterTimeStart Element name: ChapterTimeStart path: \Segment\Chapters\EditionEntry\+ChapterAtom\ChapterTimeStart id: 0x91 minOccurs: 1 maxOccurs: 1 type: uinteger definition: Timestamp of the start of Chapter (not scaled). 8.1.7.1.4.4. ChapterTimeEnd Element name: ChapterTimeEnd path: \Segment\Chapters\EditionEntry\+ChapterAtom\ChapterTimeEnd id: 0x92 maxOccurs: 1 type: uinteger definition: Timestamp of the end of Chapter (timestamp excluded, not scaled). The value MUST be strictly greater than the ChapterTimeStart of the same ChapterAtom. usage notes: If the Edition is an ordered edition, see Section 22.1.3, then this Element is REQUIRED. 8.1.7.1.4.5. ChapterFlagHidden Element name: ChapterFlagHidden path: \Segment\Chapters\EditionEntry\+ChapterAtom\ChapterFlagHidden id: 0x98 minOccurs: 1 Lhomme, et al. Expires 12 April 2022 [Page 99] Internet-Draft Matroska Format October 2021 maxOccurs: 1 range: 0-1 default: 0 type: uinteger definition: Set to 1 if a chapter is hidden. Hidden chapters it SHOULD NOT be available to the user interface (but still to Control Tracks; see Section 22.2.3 on Chapter flags). 8.1.7.1.4.6. ChapterSegmentUID Element name: ChapterSegmentUID path: \Segment\Chapters\EditionEntry\+ChapterAtom\ChapterSegmentUID id: 0x6E67 minOccurs: see implementation notes maxOccurs: 1 range: >0 type: binary definition: The SegmentUID of another Segment to play during this chapter. notes: +===========+=============================================+ | attribute | note | +===========+=============================================+ | minOccurs | ChapterSegmentUID MUST be set (minOccurs=1) | | | if ChapterSegmentEditionUID is used; see | | | Section 19.2 on medium-linking Segments. | +-----------+---------------------------------------------+ Table 27: ChapterSegmentUID implementation notes 8.1.7.1.4.7. ChapterSegmentEditionUID Element name: ChapterSegmentEditionUID path: \Segment\Chapters\EditionEntry\+ChapterAtom\ChapterSegmentEdit Lhomme, et al. Expires 12 April 2022 [Page 100] Internet-Draft Matroska Format October 2021 ionUID id: 0x6EBC maxOccurs: 1 range: not 0 type: uinteger definition: The EditionUID to play from the Segment linked in ChapterSegmentUID. If ChapterSegmentEditionUID is undeclared, then no Edition of the linked Segment is used; see Section 19.2 on medium-linking Segments. 8.1.7.1.4.8. ChapterPhysicalEquiv Element name: ChapterPhysicalEquiv path: \Segment\Chapters\EditionEntry\+ChapterAtom\ChapterPhysicalEqu iv id: 0x63C3 maxOccurs: 1 type: uinteger definition: Specify the physical equivalent of this ChapterAtom like "DVD" (60) or "SIDE" (50); see Section 22.4 for a complete list of values. 8.1.7.1.4.9. ChapterDisplay Element name: ChapterDisplay path: \Segment\Chapters\EditionEntry\+ChapterAtom\ChapterDisplay id: 0x80 type: master definition: Contains all possible strings to use for the chapter display. Lhomme, et al. Expires 12 April 2022 [Page 101] Internet-Draft Matroska Format October 2021 8.1.7.1.4.10. ChapString Element name: ChapString path: \Segment\Chapters\EditionEntry\+ChapterAtom\ChapterDisplay\Cha pString id: 0x85 minOccurs: 1 maxOccurs: 1 type: utf-8 definition: Contains the string to use as the chapter atom. 8.1.7.1.4.11. ChapLanguage Element name: ChapLanguage path: \Segment\Chapters\EditionEntry\+ChapterAtom\ChapterDisplay\Cha pLanguage id: 0x437C minOccurs: 1 default: eng type: string definition: A language corresponding to the string, in the bibliographic ISO-639-2 form [ISO639-2]. This Element MUST be ignored if a ChapLanguageIETF Element is used within the same ChapterDisplay Element. 8.1.7.1.4.12. ChapLanguageIETF Element name: ChapLanguageIETF path: \Segment\Chapters\EditionEntry\+ChapterAtom\ChapterDisplay\Cha pLanguageIETF id: 0x437D type: string Lhomme, et al. Expires 12 April 2022 [Page 102] Internet-Draft Matroska Format October 2021 minver: 4 definition: Specifies a language corresponding to the ChapString in the format defined in [BCP47] and using the IANA Language Subtag Registry [IANALangRegistry]. If a ChapLanguageIETF Element is used, then any ChapLanguage and ChapCountry Elements used in the same ChapterDisplay MUST be ignored. 8.1.7.1.4.13. ChapCountry Element name: ChapCountry path: \Segment\Chapters\EditionEntry\+ChapterAtom\ChapterDisplay\Cha pCountry id: 0x437E type: string definition: A country corresponding to the string, using the same 2 octets country-codes as in Internet domains [IANADomains] based on [ISO3166-1] alpha-2 codes. This Element MUST be ignored if a ChapLanguageIETF Element is used within the same ChapterDisplay Element. 8.1.7.1.4.14. ChapProcess Element name: ChapProcess path: \Segment\Chapters\EditionEntry\+ChapterAtom\ChapProcess id: 0x6944 type: master definition: Contains all the commands associated to the Atom. 8.1.7.1.4.15. ChapProcessCodecID Element name: ChapProcessCodecID path: \Segment\Chapters\EditionEntry\+ChapterAtom\ChapProcess\ChapPr ocessCodecID id: 0x6955 minOccurs: 1 Lhomme, et al. Expires 12 April 2022 [Page 103] Internet-Draft Matroska Format October 2021 maxOccurs: 1 default: 0 type: uinteger definition: Contains the type of the codec used for the processing. A value of 0 means native Matroska processing (to be defined), a value of 1 means the DVD command set is used; see Section 22.3 on DVD menus. More codec IDs can be added later. 8.1.7.1.4.16. ChapProcessPrivate Element name: ChapProcessPrivate path: \Segment\Chapters\EditionEntry\+ChapterAtom\ChapProcess\ChapPr ocessPrivate id: 0x450D maxOccurs: 1 type: binary definition: Some optional data attached to the ChapProcessCodecID information. For ChapProcessCodecID = 1, it is the "DVD level" equivalent; see Section 22.3 on DVD menus. 8.1.7.1.4.17. ChapProcessCommand Element name: ChapProcessCommand path: \Segment\Chapters\EditionEntry\+ChapterAtom\ChapProcess\ChapPr ocessCommand id: 0x6911 type: master definition: Contains all the commands associated to the Atom. 8.1.7.1.4.18. ChapProcessTime Element name: ChapProcessTime path: \Segment\Chapters\EditionEntry\+ChapterAtom\ChapProcess\ChapPr ocessCommand\ChapProcessTime Lhomme, et al. Expires 12 April 2022 [Page 104] Internet-Draft Matroska Format October 2021 id: 0x6922 minOccurs: 1 maxOccurs: 1 type: uinteger definition: Defines when the process command SHOULD be handled restrictions: +=======+===============================+ | value | label | +=======+===============================+ | 0 | during the whole chapter | +-------+-------------------------------+ | 1 | before starting playback | +-------+-------------------------------+ | 2 | after playback of the chapter | +-------+-------------------------------+ Table 28: ChapProcessTime values 8.1.7.1.4.19. ChapProcessData Element name: ChapProcessData path: \Segment\Chapters\EditionEntry\+ChapterAtom\ChapProcess\ChapPr ocessCommand\ChapProcessData id: 0x6933 minOccurs: 1 maxOccurs: 1 type: binary definition: Contains the command information. The data SHOULD be interpreted depending on the ChapProcessCodecID value. For ChapProcessCodecID = 1, the data correspond to the binary DVD cell pre/post commands; see Section 22.3 on DVD menus. 8.1.8. Tags Element name: Tags Lhomme, et al. Expires 12 April 2022 [Page 105] Internet-Draft Matroska Format October 2021 path: \Segment\Tags id: 0x1254C367 type: master definition: Element containing metadata describing Tracks, Editions, Chapters, Attachments, or the Segment as a whole. A list of valid tags can be found in [MatroskaTags]. 8.1.8.1. Tag Element name: Tag path: \Segment\Tags\Tag id: 0x7373 minOccurs: 1 type: master definition: A single metadata descriptor. 8.1.8.1.1. Targets Element name: Targets path: \Segment\Tags\Tag\Targets id: 0x63C0 minOccurs: 1 maxOccurs: 1 type: master definition: Specifies which other elements the metadata represented by the Tag applies to. If empty or not present, then the Tag describes everything in the Segment. 8.1.8.1.1.1. TargetTypeValue Element name: TargetTypeValue path: \Segment\Tags\Tag\Targets\TargetTypeValue Lhomme, et al. Expires 12 April 2022 [Page 106] Internet-Draft Matroska Format October 2021 id: 0x68CA maxOccurs: 1 default: 50 type: uinteger definition: A number to indicate the logical level of the target. defined values: +=======+==========================+================================+ | value | label | definition | +=======+==========================+================================+ | 70 | COLLECTION | The highest hierarchical level | | | | that tags can describe. | +-------+--------------------------+--------------------------------+ | 60 | EDITION / ISSUE / | A list of lower levels grouped | | | VOLUME / OPUS / | together. | | | SEASON / SEQUEL | | +-------+--------------------------+--------------------------------+ | 50 | ALBUM / OPERA / | The most common grouping level | | | CONCERT / MOVIE / | of music and video (equals to | | | EPISODE / CONCERT | an episode for TV series). | +-------+--------------------------+--------------------------------+ | 40 | PART / SESSION | When an album or episode has | | | | different logical parts. | +-------+--------------------------+--------------------------------+ | 30 | TRACK / SONG / | The common parts of an album | | | CHAPTER | or movie. | +-------+--------------------------+--------------------------------+ | 20 | SUBTRACK / PART / | Corresponds to parts of a | | | MOVEMENT / SCENE | track for audio (like a | | | | movement). | +-------+--------------------------+--------------------------------+ | 10 | SHOT | The lowest hierarchy found in | | | | music or movies. | +-------+--------------------------+--------------------------------+ Table 29: TargetTypeValue values 8.1.8.1.1.2. TargetType Element name: TargetType path: \Segment\Tags\Tag\Targets\TargetType Lhomme, et al. Expires 12 April 2022 [Page 107] Internet-Draft Matroska Format October 2021 id: 0x63CA maxOccurs: 1 type: string definition: An informational string that can be used to display the logical level of the target like "ALBUM", "TRACK", "MOVIE", "CHAPTER", etc ; see Section 6.4 of [MatroskaTags]. restrictions: +============+============+ | value | label | +============+============+ | COLLECTION | COLLECTION | +------------+------------+ | EDITION | EDITION | +------------+------------+ | ISSUE | ISSUE | +------------+------------+ | VOLUME | VOLUME | +------------+------------+ | OPUS | OPUS | +------------+------------+ | SEASON | SEASON | +------------+------------+ | SEQUEL | SEQUEL | +------------+------------+ | ALBUM | ALBUM | +------------+------------+ | OPERA | OPERA | +------------+------------+ | CONCERT | CONCERT | +------------+------------+ | MOVIE | MOVIE | +------------+------------+ | EPISODE | EPISODE | +------------+------------+ | PART | PART | +------------+------------+ | SESSION | SESSION | +------------+------------+ | TRACK | TRACK | +------------+------------+ | SONG | SONG | +------------+------------+ | CHAPTER | CHAPTER | Lhomme, et al. Expires 12 April 2022 [Page 108] Internet-Draft Matroska Format October 2021 +------------+------------+ | SUBTRACK | SUBTRACK | +------------+------------+ | PART | PART | +------------+------------+ | MOVEMENT | MOVEMENT | +------------+------------+ | SCENE | SCENE | +------------+------------+ | SHOT | SHOT | +------------+------------+ Table 30: TargetType values 8.1.8.1.1.3. TagTrackUID Element name: TagTrackUID path: \Segment\Tags\Tag\Targets\TagTrackUID id: 0x63C5 default: 0 type: uinteger definition: A unique ID to identify the Track(s) the tags belong to. usage notes: If the value is 0 at this level, the tags apply to all tracks in the Segment. If set to any other value, it MUST match the TrackUID value of a track found in this Segment. 8.1.8.1.1.4. TagEditionUID Element name: TagEditionUID path: \Segment\Tags\Tag\Targets\TagEditionUID id: 0x63C9 default: 0 type: uinteger definition: A unique ID to identify the EditionEntry(s) the tags belong to. usage notes: If the value is 0 at this level, the tags apply to all Lhomme, et al. Expires 12 April 2022 [Page 109] Internet-Draft Matroska Format October 2021 editions in the Segment. If set to any other value, it MUST match the EditionUID value of an edition found in this Segment. 8.1.8.1.1.5. TagChapterUID Element name: TagChapterUID path: \Segment\Tags\Tag\Targets\TagChapterUID id: 0x63C4 default: 0 type: uinteger definition: A unique ID to identify the Chapter(s) the tags belong to. usage notes: If the value is 0 at this level, the tags apply to all chapters in the Segment. If set to any other value, it MUST match the ChapterUID value of a chapter found in this Segment. 8.1.8.1.1.6. TagAttachmentUID Element name: TagAttachmentUID path: \Segment\Tags\Tag\Targets\TagAttachmentUID id: 0x63C6 default: 0 type: uinteger definition: A unique ID to identify the Attachment(s) the tags belong to. usage notes: If the value is 0 at this level, the tags apply to all the attachments in the Segment. If set to any other value, it MUST match the FileUID value of an attachment found in this Segment. 8.1.8.1.2. SimpleTag Element name: SimpleTag path: \Segment\Tags\Tag\+SimpleTag Lhomme, et al. Expires 12 April 2022 [Page 110] Internet-Draft Matroska Format October 2021 id: 0x67C8 minOccurs: 1 type: master recursive: 1 definition: Contains general information about the target. 8.1.8.1.2.1. TagName Element name: TagName path: \Segment\Tags\Tag\+SimpleTag\TagName id: 0x45A3 minOccurs: 1 maxOccurs: 1 type: utf-8 definition: The name of the Tag that is going to be stored. 8.1.8.1.2.2. TagLanguage Element name: TagLanguage path: \Segment\Tags\Tag\+SimpleTag\TagLanguage id: 0x447A minOccurs: 1 maxOccurs: 1 default: und type: string definition: Specifies the language of the tag specified, in the Matroska languages form; see Section 6 on language codes. This Element MUST be ignored if the TagLanguageIETF Element is used within the same SimpleTag Element. Lhomme, et al. Expires 12 April 2022 [Page 111] Internet-Draft Matroska Format October 2021 8.1.8.1.2.3. TagLanguageIETF Element name: TagLanguageIETF path: \Segment\Tags\Tag\+SimpleTag\TagLanguageIETF id: 0x447B maxOccurs: 1 type: string minver: 4 definition: Specifies the language used in the TagString according to [BCP47] and using the IANA Language Subtag Registry [IANALangRegistry]. If this Element is used, then any TagLanguage Elements used in the same SimpleTag MUST be ignored. 8.1.8.1.2.4. TagDefault Element name: TagDefault path: \Segment\Tags\Tag\+SimpleTag\TagDefault id: 0x4484 minOccurs: 1 maxOccurs: 1 range: 0-1 default: 1 type: uinteger definition: A boolean value to indicate if this is the default/ original language to use for the given tag. 8.1.8.1.2.5. TagString Element name: TagString path: \Segment\Tags\Tag\+SimpleTag\TagString id: 0x4487 Lhomme, et al. Expires 12 April 2022 [Page 112] Internet-Draft Matroska Format October 2021 maxOccurs: 1 type: utf-8 definition: The value of the Tag. 8.1.8.1.2.6. TagBinary Element name: TagBinary path: \Segment\Tags\Tag\+SimpleTag\TagBinary id: 0x4485 maxOccurs: 1 type: binary definition: The values of the Tag, if it is binary. Note that this cannot be used in the same SimpleTag as TagString. 9. Matroska Element Ordering Except for the EBML Header and the CRC-32 Element, the EBML specification does not require any particular storage order for Elements. The Matroska specification however defines mandates and recommendations for ordering certain Elements in order to facilitate better playback, seeking, and editing efficiency. This section describes and offers rationale for ordering requirements and recommendations for Matroska. 9.1. Top-Level Elements The Info Element is the only REQUIRED Top-Level Element in a Matroska file. To be playable, Matroska MUST also contain at least one Tracks Element and Cluster Element. The first Info Element and the first Tracks Element MUST either be stored before the first Cluster Element or both SHALL be referenced by a SeekHead Element occurring before the first Cluster Element. Lhomme, et al. Expires 12 April 2022 [Page 113] Internet-Draft Matroska Format October 2021 It is possible to edit a Matroska file after it has been created. For example, chapters, tags, or attachments can be added. When new Top-Level Elements are added to a Matroska file, the SeekHead Element(s) MUST be updated so that the SeekHead Element(s) itemize the identity and position of all Top-Level Elements. Editing, removing, or adding Elements to a Matroska file often requires that some existing Elements be voided or extended; therefore, it is RECOMMENDED to use Void Elements as padding in between Top-Level Elements. 9.2. CRC-32 As noted by the EBML specification, if a CRC-32 Element is used, then the CRC-32 Element MUST be the first ordered Element within its Parent Element. The Matroska specification recommends that CRC-32 Elements SHOULD NOT be used as an immediate Child Element of the Segment Element; however all Top-Level Elements of an EBML Document SHOULD include a CRC-32 Element as a Child Element. 9.3. SeekHead If used, the first SeekHead Element SHOULD be the first non-CRC-32 Child Element of the Segment Element. If a second SeekHead Element is used, then the first SeekHead Element MUST reference the identity and position of the second SeekHead. Additionally, the second SeekHead Element MUST only reference Cluster Elements and not any other Top-Level Element already contained within the first SeekHead Element. The second SeekHead Element MAY be stored in any order relative to the other Top-Level Elements. Whether one or two SeekHead Element(s) are used, the SeekHead Element(s) MUST collectively reference the identity and position of all Top-Level Elements except for the first SeekHead Element. It is RECOMMENDED that the first SeekHead Element be followed by a Void Element to allow for the SeekHead Element to be expanded to cover new Top-Level Elements that could be added to the Matroska file, such as Tags, Chapters, and Attachments Elements. 9.4. Cues (index) The Cues Element is RECOMMENDED to optimize seeking access in Matroska. It is programmatically simpler to add the Cues Element after all Cluster Elements have been written because this does not require a prediction of how much space to reserve before writing the Cluster Elements. However, storing the Cues Element before the Cluster Elements can provide some seeking advantages. If the Cues Element is present, then it SHOULD either be stored before the first Cluster Element or be referenced by a SeekHead Element. Lhomme, et al. Expires 12 April 2022 [Page 114] Internet-Draft Matroska Format October 2021 9.5. Info The first Info Element SHOULD occur before the first Tracks Element and first Cluster Element except when referenced by a SeekHead Element. 9.6. Chapters Element The Chapters Element SHOULD be placed before the Cluster Element(s). The Chapters Element can be used during playback even if the user does not need to seek. It immediately gives the user information about what section is being read and what other sections are available. In the case of Ordered Chapters it is RECOMMENDED to evaluate the logical linking even before playing. The Chapters Element SHOULD be placed before the first Tracks Element and after the first Info Element. 9.7. Attachments The Attachments Element is not intended to be used by default when playing the file, but could contain information relevant to the content, such as cover art or fonts. Cover art is useful even before the file is played and fonts could be needed before playback starts for initialization of subtitles. The Attachments Element MAY be placed before the first Cluster Element; however if the Attachments Element is likely to be edited, then it SHOULD be placed after the last Cluster Element. 9.8. Tags The Tags Element is most subject to changes after the file was originally created. For easier editing, the Tags Element SHOULD be placed at the end of the Segment Element, even after the Attachments Element. On the other hand, it is inconvenient to have to seek in the Segment for tags, especially for network streams. So it's better if the Tags Element is found early in the stream. When editing the Tags Element, the original Tags Element at the beginning can be overwritten with a Void Element and a new Tags Element written at the end of the Segment Element. The file size will only marginally change. 9.9. Optimum layout from a muxer * SeekHead * Info * Tracks Lhomme, et al. Expires 12 April 2022 [Page 115] Internet-Draft Matroska Format October 2021 * Chapters * Attachments * Tags * Clusters * Cues 9.10. Optimum layout after editing tags * SeekHead * Info * Tracks * Chapters * Attachments * Void * Clusters * Cues * Tags 9.11. Optimum layout with Cues at the front * SeekHead * Info * Tracks * Chapters * Attachments * Tags * Cues * Clusters Lhomme, et al. Expires 12 April 2022 [Page 116] Internet-Draft Matroska Format October 2021 9.12. Cluster Timestamp The Timestamp Element MUST occur as in storage order before any SimpleBlock, BlockGroup, or EncryptedBlock, within the Cluster Element. 10. Unknown elements Matroska is based upon the principle that a reading application does not have to support 100% of the specifications in order to be able to play the file. A Matroska file therefore contains version indicators that tell a reading application what to expect. It is possible and valid to have the version fields indicate that the file contains Matroska Elements from a higher specification version number while signaling that a reading application MUST only support a lower version number properly in order to play it back (possibly with a reduced feature set). For example, a reading application supporting at least Matroska version V reading a file whose DocTypeReadVersion field is equal to or lower than V MUST skip Matroska/EBML Elements it encounters but does not know about if that unknown element fits into the size constraints set by the current Parent Element. 11. DefaultDecodedFieldDuration The DefaultDecodedFieldDuration Element can signal to the displaying application how often fields of a video sequence will be available for displaying. It can be used for both interlaced and progressive content. If the video sequence is signaled as interlaced, then the period between two successive fields at the output of the decoding process equals DefaultDecodedFieldDuration. For video sequences signaled as progressive, it is twice the value of DefaultDecodedFieldDuration. These values are valid at the end of the decoding process before post-processing (such as deinterlacing or inverse telecine) is applied. Examples: * Blu-ray movie: 1000000000ns/(48/1.001) = 20854167ns * PAL broadcast/DVD: 1000000000ns/(50/1.000) = 20000000ns * N/ATSC broadcast: 1000000000ns/(60/1.001) = 16683333ns Lhomme, et al. Expires 12 April 2022 [Page 117] Internet-Draft Matroska Format October 2021 * hard-telecined DVD: 1000000000ns/(60/1.001) = 16683333ns (60 encoded interlaced fields per second) * soft-telecined DVD: 1000000000ns/(60/1.001) = 16683333ns (48 encoded interlaced fields per second, with "repeat_first_field = 1") 12. Block Structure Bit 0 is the most significant bit. Frames using references SHOULD be stored in "coding order". That means the references first, and then the frames referencing them. A consequence is that timestamps might not be consecutive. But a frame with a past timestamp MUST reference a frame already known, otherwise it's considered bad/void. 12.1. Block Header +========+========+=============================================+ | Offset | Player | Description | +========+========+=============================================+ | 0x00+ | MUST | Track Number (Track Entry). It is coded in | | | | EBML like form (1 octet if the value is < | | | | 0x80, 2 if < 0x4000, etc) (most significant | | | | bits set to increase the range). | +--------+--------+---------------------------------------------+ | 0x01+ | MUST | Timestamp (relative to Cluster timestamp, | | | | signed int16) | +--------+--------+---------------------------------------------+ Table 31: Block Header base parts 12.2. Block Header Flags +========+=====+========+====================================+ | Offset | Bit | Player | Description | +========+=====+========+====================================+ | 0x03+ | 0-3 | - | Reserved, set to 0 | +--------+-----+--------+------------------------------------+ | 0x03+ | 4 | - | Invisible, the codec SHOULD decode | | | | | this frame but not display it | +--------+-----+--------+------------------------------------+ | 0x03+ | 5-6 | MUST | Lacing | +--------+-----+--------+------------------------------------+ | | | | * 00 : no lacing | +--------+-----+--------+------------------------------------+ | | | | * 01 : Xiph lacing | Lhomme, et al. Expires 12 April 2022 [Page 118] Internet-Draft Matroska Format October 2021 +--------+-----+--------+------------------------------------+ | | | | * 11 : EBML lacing | +--------+-----+--------+------------------------------------+ | | | | * 10 : fixed-size lacing | +--------+-----+--------+------------------------------------+ | 0x03+ | 7 | - | not used | +--------+-----+--------+------------------------------------+ Table 32: Block Header flags part 12.3. Lacing Lacing is a mechanism to save space when storing data. It is typically used for small blocks of data (referred to as frames in Matroska). There are 3 types of lacing: 1. Xiph, inspired by what is found in the Ogg container 2. EBML, which is the same with sizes coded differently 3. fixed-size, where the size is not coded For example, a user wants to store 3 frames of the same track. The first frame is 800 octets long, the second is 500 octets long and the third is 1000 octets long. As these data are small, they can be stored in a lace to save space. They will then be stored in the same block as follows: 12.3.1. Xiph lacing * Block head (with lacing bits set to 01) * Lacing head: Number of frames in the lace -1 -- i.e. 2 (the 800 and 500 octets one) * Lacing sizes: only the 2 first ones will be coded, 800 gives 255;255;255;35, 500 gives 255;245. The size of the last frame is deduced from the total size of the Block. * Data in frame 1 * Data in frame 2 * Data in frame 3 A frame with a size multiple of 255 is coded with a 0 at the end of the size -- for example, 765 is coded 255;255;255;0. Lhomme, et al. Expires 12 April 2022 [Page 119] Internet-Draft Matroska Format October 2021 12.3.2. EBML lacing In this case, the size is not coded as blocks of 255 bytes, but as a difference with the previous size and this size is coded as in EBML. The first size in the lace is unsigned as in EBML. The others use a range shifting to get a sign on each value: +==========================+=======================================+ | Bit Representation | Value | +==========================+=======================================+ | 1xxx xxxx | value -(2^6-1) to 2^6-1 (ie 0 to | | | 2^7-2 minus 2^6-1, half of the range) | +--------------------------+---------------------------------------+ | 01xx xxxx xxxx xxxx | value -(2^13-1) to 2^13-1 | +--------------------------+---------------------------------------+ | 001x xxxx xxxx xxxx xxxx | value -(2^20-1) to 2^20-1 | | xxxx | | +--------------------------+---------------------------------------+ | 0001 xxxx xxxx xxxx xxxx | value -(2^27-1) to 2^27-1 | | xxxx xxxx xxxx | | +--------------------------+---------------------------------------+ | 0000 1xxx xxxx xxxx xxxx | value -(2^34-1) to 2^34-1 | | xxxx xxxx xxxx xxxx xxxx | | +--------------------------+---------------------------------------+ | 0000 01xx xxxx xxxx xxxx | value -(2^41-1) to 2^41-1 | | xxxx xxxx xxxx xxxx xxxx | | | xxxx xxxx | | +--------------------------+---------------------------------------+ | 0000 001x xxxx xxxx xxxx | value -(2^48-1) to 2^48-1 | | xxxx xxxx xxxx xxxx xxxx | | | xxxx xxxx xxxx xxxx | | +--------------------------+---------------------------------------+ Table 33: EBML Lacing bits usage * Block head (with lacing bits set to 11) * Lacing head: Number of frames in the lace -1 -- i.e. 2 (the 800 and 500 octets one) * Lacing sizes: only the 2 first ones will be coded, 800 gives 0x320 0x4000 = 0x4320, 500 is coded as -300 : - 0x12C + 0x1FFF + 0x4000 = 0x5ED3. The size of the last frame is deduced from the total size of the Block. * Data in frame 1 * Data in frame 2 Lhomme, et al. Expires 12 April 2022 [Page 120] Internet-Draft Matroska Format October 2021 * Data in frame 3 12.3.3. Fixed-size lacing In this case, only the number of frames in the lace is saved, the size of each frame is deduced from the total size of the Block. For example, for 3 frames of 800 octets each: * Block head (with lacing bits set to 10) * Lacing head: Number of frames in the lace -1 -- i.e. 2 * Data in frame 1 * Data in frame 2 * Data in frame 3 12.4. SimpleBlock Structure The SimpleBlock is inspired by the Block structure; see Section 12. The main differences are the added Keyframe flag and Discardable flag. Otherwise everything is the same. Bit 0 is the most significant bit. Frames using references SHOULD be stored in "coding order". That means the references first, and then the frames referencing them. A consequence is that timestamps might not be consecutive. But a frame with a past timestamp MUST reference a frame already known, otherwise it's considered bad/void. 12.4.1. SimpleBlock Header +========+========+=============================================+ | Offset | Player | Description | +========+========+=============================================+ | 0x00+ | MUST | Track Number (Track Entry). It is coded in | | | | EBML like form (1 octet if the value is < | | | | 0x80, 2 if < 0x4000, etc) (most significant | | | | bits set to increase the range). | +--------+--------+---------------------------------------------+ | 0x01+ | MUST | Timestamp (relative to Cluster timestamp, | | | | signed int16) | +--------+--------+---------------------------------------------+ Table 34: SimpleBlock Header base parts Lhomme, et al. Expires 12 April 2022 [Page 121] Internet-Draft Matroska Format October 2021 12.4.2. SimpleBlock Header Flags +========+=====+========+==========================================+ | Offset | Bit | Player | Description | +========+=====+========+==========================================+ | 0x03+ | 0 | - | Keyframe, set when the Block contains | | | | | only keyframes | +--------+-----+--------+------------------------------------------+ | 0x03+ | 1-3 | - | Reserved, set to 0 | +--------+-----+--------+------------------------------------------+ | 0x03+ | 4 | - | Invisible, the codec SHOULD decode this | | | | | frame but not display it | +--------+-----+--------+------------------------------------------+ | 0x03+ | 5-6 | MUST | Lacing | +--------+-----+--------+------------------------------------------+ | | | | * 00 : no lacing | +--------+-----+--------+------------------------------------------+ | | | | * 01 : Xiph lacing | +--------+-----+--------+------------------------------------------+ | | | | * 11 : EBML lacing | +--------+-----+--------+------------------------------------------+ | | | | * 10 : fixed-size lacing | +--------+-----+--------+------------------------------------------+ | 0x03+ | 7 | - | Discardable, the frames of the Block can | | | | | be discarded during playing if needed | +--------+-----+--------+------------------------------------------+ Table 35: SimpleBlock Header flags part 12.4.3. Laced Data When lacing bit is set. +========+========+=============================================+ | Offset | Player | Description | +========+========+=============================================+ | 0x00 | MUST | Number of frames in the lace-1 (uint8) | +--------+--------+---------------------------------------------+ | 0x01 / | MUST | Lace-coded size of each frame of the lace, | | 0xXX | | except for the last one (multiple uint8). | | | | *This is not used with Fixed-size lacing as | | | | it is calculated automatically from (total | | | | size of lace) / (number of frames in lace). | +--------+--------+---------------------------------------------+ Table 36: Lace sizes coded in the Block For (possibly) Laced Data Lhomme, et al. Expires 12 April 2022 [Page 122] Internet-Draft Matroska Format October 2021 +========+========+==========================+ | Offset | Player | Description | +========+========+==========================+ | 0x00 | MUST | Consecutive laced frames | +--------+--------+--------------------------+ Table 37: Lace data after lace sizes 13. Timestamps Historically timestamps in Matroska were mistakenly called timecodes. The Timestamp Element was called Timecode, the TimestampScale Element was called TimecodeScale, the TrackTimestampScale Element was called TrackTimecodeScale and the ReferenceTimestamp Element was called ReferenceTimeCode. 13.1. Timestamp Types * Absolute Timestamp = Block+Cluster * Relative Timestamp = Block * Scaled Timestamp = Block+Cluster * Raw Timestamp = (Block+Cluster)*TimestampScale*TrackTimestampScale 13.2. Block Timestamps The Block Element's timestamp MUST be a signed integer that represents the Raw Timestamp relative to the Cluster's Timestamp Element, multiplied by the TimestampScale Element. See Section 13.4 for more information. The Block Element's timestamp MUST be represented by a 16bit signed integer (sint16). The Block's timestamp has a range of -32768 to +32767 units. When using the default value of the TimestampScale Element, each integer represents 1ms. The maximum time span of Block Elements in a Cluster using the default TimestampScale Element of 1ms is 65536ms. If a Cluster's Timestamp Element is set to zero, it is possible to have Block Elements with a negative Raw Timestamp. Block Elements with a negative Raw Timestamp are not valid. Lhomme, et al. Expires 12 April 2022 [Page 123] Internet-Draft Matroska Format October 2021 13.3. Raw Timestamp The exact time of an object SHOULD be represented in nanoseconds. To find out a Block's Raw Timestamp, you need the Block's Timestamp Element, the Cluster's Timestamp Element, and the TimestampScale Element. 13.4. TimestampScale The TimestampScale Element is used to calculate the Raw Timestamp of a Block. The timestamp is obtained by adding the Block's timestamp to the Cluster's Timestamp Element, and then multiplying that result by the TimestampScale. The result will be the Block's Raw Timestamp in nanoseconds. The formula for this would look like: (a + b) * c a = `Block`'s Timestamp b = `Cluster`'s Timestamp c = `TimestampScale` For example, assume a Cluster's Timestamp has a value of 564264, the Block has a Timestamp of 1233, and the TimestampScale Element is the default of 1000000. (1233 + 564264) * 1000000 = 565497000000 So, the Block in this example has a specific time of 565497000000 in nanoseconds. In milliseconds this would be 565497ms. 13.5. TimestampScale Rounding Because the default value of TimestampScale is 1000000, which makes each integer in the Cluster and Block Timestamp Elements equal 1ms, this is the most commonly used. When dealing with audio, this causes inaccuracy when seeking. When the audio is combined with video, this is not an issue. For most cases, the the synch of audio to video does not need to be more than 1ms accurate. This becomes obvious when one considers that sound will take 2-3ms to travel a single meter, so distance from your speakers will have a greater effect on audio/visual synch than this. Lhomme, et al. Expires 12 April 2022 [Page 124] Internet-Draft Matroska Format October 2021 However, when dealing with audio-only files, seeking accuracy can become critical. For instance, when storing a whole CD in a single track, a user will want to be able to seek to the exact sample that a song begins at. If seeking a few sample ahead or behind, a crack or pop may result as a few odd samples are rendered. Also, when performing precise editing, it may be very useful to have the audio accuracy down to a single sample. When storing timestamps for an audio stream, the TimestampScale Element SHOULD have an accuracy of at least that of the audio sample rate, otherwise there are rounding errors that prevent users from knowing the precise location of a sample. Here's how a program has to round each timestamp in order to be able to recreate the sample number accurately. Let's assume that the application has an audio track with a sample rate of 44100. As written above the TimestampScale MUST have at least the accuracy of the sample rate itself: 1000000000 / 44100 = 22675.7369614512. This value MUST always be truncated. Otherwise the accuracy will not suffice. So in this example the application will use 22675 for the TimestampScale. The application could even use some lower value like 22674, which would allow it to be a little bit imprecise about the original timestamps. But more about that in a minute. Next the application wants to write sample number 52340 and calculates the timestamp. This is easy. In order to calculate the Raw Timestamp in ns all it has to do is calculate Raw Timestamp = round(1000000000 * sample_number / sample_rate). Rounding at this stage is very important! The application might skip it if it choses a slightly smaller value for the TimestampScale factor instead of the truncated one like shown above. Otherwise it has to round or the results won't be reversible. For our example we get Raw Timestamp = round(1000000000 * 52340 / 44100) = round(1186848072.56236) = 1186848073. The next step is to calculate the Absolute Timestamp - that is the timestamp that will be stored in the Matroska file. Here the application has to divide the Raw Timestamp from the previous paragraph by the TimestampScale factor and round the result: Absolute Timestamp = round(Raw Timestamp / TimestampScale_factor), which will result in the following for our example: Absolute Timestamp = round(1186848073 / 22675) = round(52341.7011245866) = 52342. This number is the one the application has to write to the file. Now our file is complete, and we want to play it back with another application. Its task is to find out which sample the first application wrote into the file. So it starts reading the Matroska Lhomme, et al. Expires 12 April 2022 [Page 125] Internet-Draft Matroska Format October 2021 file and finds the TimestampScale factor 22675 and the audio sample rate 44100. Later it finds a data block with the Absolute Timestamp of 52342. But how does it get the sample number from these numbers? First it has to calculate the Raw Timestamp of the block it has just read. Here's no rounding involved, just an integer multiplication: Raw Timestamp = Absolute Timestamp * TimestampScale_factor. In our example: Raw Timestamp = 52342 * 22675 = 1186854850. The conversion from the Raw Timestamp to the sample number again requires rounding: sample_number = round(Raw Timestamp * sample_rate / 1000000000). In our example: sample_number = round(1186854850 * 44100 / 1000000000) = round(52340.298885) = 52340. This is exactly the sample number that the previous program started with. Some general notes for a program: 1. Always calculate the timestamps / sample numbers with floating point numbers of at least 64bit precision (called 'double' in most modern programming languages). If you're calculating with integers, then make sure they're 64bit long, too. 2. Always round if you divide. Always! If you don't you'll end up with situations in which you have a timestamp in the Matroska file that does not correspond to the sample number that it started with. Using a slightly lower timestamp scale factor can help here in that it removes the need for proper rounding in the conversion from sample number to Raw Timestamp. 13.6. TrackTimestampScale The TrackTimestampScale Element is used align tracks that would otherwise be played at different speeds. An example of this would be if you have a film that was originally recorded at 24fps video. When playing this back through a PAL broadcasting system, it is standard to speed up the film to 25fps to match the 25fps display speed of the PAL broadcasting standard. However, when broadcasting the video through NTSC, it is typical to leave the film at its original speed. If you wanted to make a single file where there was one video stream, and an audio stream used from the PAL broadcast, as well as an audio stream used from the NTSC broadcast, you would have the problem that the PAL audio stream would be 1/24th faster than the NTSC audio stream, quickly leading to problems. It is possible to stretch out the PAL audio track and re-encode it at a slower speed, however when dealing with lossy audio codecs, this often results in a loss of audio quality and/or larger file sizes. Lhomme, et al. Expires 12 April 2022 [Page 126] Internet-Draft Matroska Format October 2021 This is the type of problem that TrackTimestampScale was designed to fix. Using it, the video can be played back at a speed that will synch with either the NTSC or the PAL audio stream, depending on which is being used for playback. To continue the above example: Track 1: Video Track 2: NTSC Audio Track 3: PAL Audio Because the NTSC track is at the original speed, it will used as the default value of 1.0 for its TrackTimestampScale. The video will also be aligned to the NTSC track with the default value of 1.0. The TrackTimestampScale value to use for the PAL track would be calculated by determining how much faster the PAL track is than the NTSC track. In this case, because we know the video for the NTSC audio is being played back at 24fps and the video for the PAL audio is being played back at 25fps, the calculation would be: 25/24 is almost 1.04166666666666666667 When writing a file that uses a non-default TrackTimestampScale, the values of the Block's timestamp are whatever they would be when normally storing the track with a default value for the TrackTimestampScale. However, the data is interleaved a little differently. Data SHOULD be interleaved by its Raw Timestamp, see Section 13.3, in the order handed back from the encoder. The Raw Timestamp of a Block from a track using TrackTimestampScale is calculated using: (Block's Timestamp + Cluster's Timestamp) * TimestampScale * TrackTimestampScale So, a Block from the PAL track above that had a Scaled Timestamp, see Section 13.1, of 100 seconds would have a Raw Timestamp of 104.66666667 seconds, and so would be stored in that part of the file. When playing back a track using the TrackTimestampScale, if the track is being played by itself, there is no need to scale it. From the above example, when playing the Video with the NTSC Audio, neither are scaled. However, when playing back the Video with the PAL Audio, the timestamps from the PAL Audio track are scaled using the TrackTimestampScale, resulting in the video playing back in synch with the audio. Lhomme, et al. Expires 12 April 2022 [Page 127] Internet-Draft Matroska Format October 2021 It would be possible for a Matroska Player to also adjust the audio's samplerate at the same time as adjusting the timestamps if you wanted to play the two audio streams synchronously. It would also be possible to adjust the video to match the audio's speed. However, for playback, the selected track(s) timestamps SHOULD be adjusted if they need to be scaled. While the above example deals specifically with audio tracks, this element can be used to align video, audio, subtitles, or any other type of track contained in a Matroska file. 14. Encryption Encryption in Matroska is designed in a very generic style to allow people to implement whatever form of encryption is best for them. It is possible to use the encryption framework in Matroska as a type of DRM (Digital Rights Management). Because encryption occurs within the Block Element, it is possible to manipulate encrypted streams without decrypting them. The streams could potentially be copied, deleted, cut, appended, or any number of other possible editing techniques without decryption. The data can be used without having to expose it or go through the decrypting process. Encryption can also be layered within Matroska. This means that two completely different types of encryption can be used, requiring two separate keys to be able to decrypt a stream. Encryption information is stored in the ContentEncodings Element under the ContentEncryption Element. 15. Image Presentation 15.1. Cropping The PixelCrop Elements (PixelCropTop, PixelCropBottom, PixelCropRight, and PixelCropLeft) indicate when, and by how much, encoded videos frames SHOULD be cropped for display. These Elements allow edges of the frame that are not intended for display, such as the sprockets of a full-frame film scan or the VANC area of a digitized analog videotape, to be stored but hidden. PixelCropTop and PixelCropBottom store an integer of how many rows of pixels SHOULD be cropped from the top and bottom of the image (respectively). PixelCropLeft and PixelCropRight store an integer of how many columns of pixels SHOULD be cropped from the left and right of the image (respectively). For example, a pillar-boxed video that stores a 1440x1080 visual image within the center of a padded Lhomme, et al. Expires 12 April 2022 [Page 128] Internet-Draft Matroska Format October 2021 1920x1080 encoded image MAY set both PixelCropLeft and PixelCropRight to "240", so that a Matroska Player SHOULD crop off 240 columns of pixels from the left and right of the encoded image to present the image with the pillar-boxes hidden. 15.2. Rotation The ProjectionPoseRoll Element (see Section 8.1.4.1.31.45) can be used to indicate that the image from the associated video track SHOULD be rotated for presentation. For instance, the following representation of the Projection Element Section 8.1.4.1.31.40) and the ProjectionPoseRoll Element represents a video track where the image SHOULD be presentation with a 90 degree counter-clockwise rotation. 90 Figure 11: Rotation example. 16. Matroska versioning The EBML Header of each Matroska document informs the reading application on what version of Matroska to expect. The Elements within EBML Header with jurisdiction over this information are DocTypeVersion and DocTypeReadVersion. DocTypeVersion MUST be equal to or greater than the highest Matroska version number of any Element present in the Matroska file. For example, a file using the SimpleBlock Element MUST have a DocTypeVersion equal to or greater than 2. A file containing CueRelativePosition Elements MUST have a DocTypeVersion equal to or greater than 4. The DocTypeReadVersion MUST contain the minimum version number that a reading application can minimally support in order to play the file back -- optionally with a reduced feature set. For example, if a file contains only Elements of version 2 or lower except for CueRelativePosition (which is a version 4 Matroska Element), then DocTypeReadVersion SHOULD still be set to 2 and not 4 because evaluating CueRelativePosition is not necessary for standard playback -- it makes seeking more precise if used. DocTypeVersion MUST always be equal to or greater than DocTypeReadVersion. Lhomme, et al. Expires 12 April 2022 [Page 129] Internet-Draft Matroska Format October 2021 A reading application supporting Matroska version V MUST NOT refuse to read an application with DocReadTypeVersion equal to or lower than V even if DocTypeVersion is greater than V. See also the note about Unknown Elements in Section 10. 17. MIME Types There is no IETF endorsed MIME type for Matroska files. These definitions can be used: * .mka : Matroska audio audio/x-matroska * .mkv : Matroska video video/x-matroska * .mk3d : Matroska 3D video video/x-matroska-3d 18. Segment Position The Segment Position of an Element refers to the position of the first octet of the Element ID of that Element, measured in octets, from the beginning of the Element Data section of the containing Segment Element. In other words, the Segment Position of an Element is the distance in octets from the beginning of its containing Segment Element minus the size of the Element ID and Element Data Size of that Segment Element. The Segment Position of the first Child Element of the Segment Element is 0. An Element which is not stored within a Segment Element, such as the Elements of the EBML Header, do not have a Segment Position. 18.1. Segment Position Exception Elements that are defined to store a Segment Position MAY define reserved values to indicate a special meaning. 18.2. Example of Segment Position This table presents an example of Segment Position by showing a hexadecimal representation of a very small Matroska file with labels to show the offsets in octets. The file contains a Segment Element with an Element ID of "0x18538067" and a MuxingApp Element with an Element ID of "0x4D80". 0 1 2 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ 0 |1A|45|DF|A3|8B|42|82|88|6D|61|74|72|6F|73|6B|61|18|53|80|67| 20 |93|15|49|A9|66|8E|4D|80|84|69|65|74|66|57|41|84|69|65|74|66| Lhomme, et al. Expires 12 April 2022 [Page 130] Internet-Draft Matroska Format October 2021 In the above example, the Element ID of the Segment Element is stored at offset 16, the Element Data Size of the Segment Element is stored at offset 20, and the Element Data of the Segment Element is stored at offset 21. The MuxingApp Element is stored at offset 26. Since the Segment Position of an Element is calculated by subtracting the position of the Element Data of the containing Segment Element from the position of that Element, the Segment Position of MuxingApp Element in the above example is '26 - 21' or '5'. 19. Linked Segments Matroska provides several methods to link two or many Segment Elements together to create a Linked Segment. A Linked Segment is a set of multiple Segments related together into a single presentation by using Hard Linking, Medium Linking, or Soft Linking. All Segments within a Linked Segment MUST utilize the same track numbers and timescale. All Segments within a Linked Segment MUST be stored within the same directory. All Segments within a Linked Segment MUST store a SegmentUID. 19.1. Hard Linking Hard Linking (also called splitting) is the process of creating a Linked Segment by relating multiple Segment Elements using the NextUID and PrevUID Elements. Within a Linked Segment, the timestamps of each Segment MUST follow consecutively in linking order. With Hard Linking, the chapters of any Segment within the Linked Segment MUST only reference the current Segment. With Hard Linking, the NextUID and PrevUID MUST reference the respective SegmentUID values of the next and previous Segments. The first Segment of a Linked Segment SHOULD have a NextUID Element and MUST NOT have a PrevUID Element. The last Segment of a Linked Segment SHOULD have a PrevUID Element and MUST NOT have a NextUID Element. The middle Segments of a Linked Segment SHOULD have both a NextUID Element and a PrevUID Element. In a chain of Linked Segments the NextUID always takes precedence over the PrevUID. So if SegmentA has a NextUID to SegmentB and SegmentB has a PrevUID to SegmentC, the link to use is SegmentA to SegmentB. If SegmentB has a PrevUID to SegmentA but SegmentA has no NextUID, then the Matroska Player MAY consider these two Segments linked as SegmentA followed by SegmentB. As an example, three Segments can be Hard Linked as a Linked Segment through cross-referencing each other with SegmentUID, PrevUID, and NextUID, as in this table. Lhomme, et al. Expires 12 April 2022 [Page 131] Internet-Draft Matroska Format October 2021 +==========+==================+==================+==================+ |file name | SegmentUID | PrevUID | NextUID | +==========+==================+==================+==================+ |start.mkv | 71000c23cd310998 | n/a | a77b3598941cb803 | | | 53fbc94dd984a5dd | | eac0fcdafe44fac9 | +----------+------------------+------------------+------------------+ |middle.mkv| a77b3598941cb803 | 71000c23cd310998 | 6c92285fa6d3e827 | | | eac0fcdafe44fac9 | 53fbc94dd984a5dd | b198d120ea3ac674 | +----------+------------------+------------------+------------------+ |end.mkv | 6c92285fa6d3e827 | a77b3598941cb803 | n/a | | | b198d120ea3ac674 | eac0fcdafe44fac9 | | +----------+------------------+------------------+------------------+ Table 38: Usual Hard Linking UIDs An other example where only the NextUID Element is used. +============+==================+=========+==================+ | file name | SegmentUID | PrevUID | NextUID | +============+==================+=========+==================+ | start.mkv | 71000c23cd310998 | n/a | a77b3598941cb803 | | | 53fbc94dd984a5dd | | eac0fcdafe44fac9 | +------------+------------------+---------+------------------+ | middle.mkv | a77b3598941cb803 | n/a | 6c92285fa6d3e827 | | | eac0fcdafe44fac9 | | b198d120ea3ac674 | +------------+------------------+---------+------------------+ | end.mkv | 6c92285fa6d3e827 | n/a | n/a | | | b198d120ea3ac674 | | | +------------+------------------+---------+------------------+ Table 39: Hard Linking without PrevUID A next example where only the PrevUID Element is used. +============+==================+==================+=========+ | file name | SegmentUID | PrevUID | NextUID | +============+==================+==================+=========+ | start.mkv | 71000c23cd310998 | n/a | n/a | | | 53fbc94dd984a5dd | | | +------------+------------------+------------------+---------+ | middle.mkv | a77b3598941cb803 | 71000c23cd310998 | n/a | | | eac0fcdafe44fac9 | 53fbc94dd984a5dd | | +------------+------------------+------------------+---------+ | end.mkv | 6c92285fa6d3e827 | a77b3598941cb803 | n/a | | | b198d120ea3ac674 | eac0fcdafe44fac9 | | +------------+------------------+------------------+---------+ Table 40: Hard Linking without NextUID Lhomme, et al. Expires 12 April 2022 [Page 132] Internet-Draft Matroska Format October 2021 In this example only the middle.mkv is using the PrevUID and NextUID Elements. +==========+==================+==================+==================+ |file name | SegmentUID | PrevUID | NextUID | +==========+==================+==================+==================+ |start.mkv | 71000c23cd310998 | n/a | n/a | | | 53fbc94dd984a5dd | | | +----------+------------------+------------------+------------------+ |middle.mkv| a77b3598941cb803 | 71000c23cd310998 | 6c92285fa6d3e827 | | | eac0fcdafe44fac9 | 53fbc94dd984a5dd | b198d120ea3ac674 | +----------+------------------+------------------+------------------+ |end.mkv | 6c92285fa6d3e827 | n/a | n/a | | | b198d120ea3ac674 | | | +----------+------------------+------------------+------------------+ Table 41: Hard Linking with mixed UID links 19.2. Medium Linking Medium Linking creates relationships between Segments using Ordered Chapters and the ChapterSegmentUID Element. A Segment Edition with Ordered Chapters MAY contain Chapter elements that reference timestamp ranges from other Segments. The Segment referenced by the Ordered Chapter via the ChapterSegmentUID Element SHOULD be played as part of a Linked Segment. The timestamps of Segment content referenced by Ordered Chapters MUST be adjusted according to the cumulative duration of the the previous Ordered Chapters. As an example a file named intro.mkv could have a SegmentUID of "0xb16a58609fc7e60653a60c984fc11ead". Another file called program.mkv could use a Chapter Edition that contains two Ordered Chapters. The first chapter references the Segment of intro.mkv with the use of a ChapterSegmentUID, ChapterSegmentEditionUID, ChapterTimeStart, and optionally a ChapterTimeEnd element. The second chapter references content within the Segment of program.mkv. A Matroska Player SHOULD recognize the Linked Segment created by the use of ChapterSegmentUID in an enabled Edition and present the reference content of the two Segments together. The ChapterSegmentUID is a binary value and the base element to set up a Linked Chapter in 2 variations: the Linked-Duration linking and the Linked-Edition linking. For both variations, the following 3 conditions MUST be met: 1. The EditionFlagOrdered Flag MUST be true. Lhomme, et al. Expires 12 April 2022 [Page 133] Internet-Draft Matroska Format October 2021 2. The ChapterSegmentUID MUST NOT be the SegmentUID of its own Segment. 3. The linked Segments MUST BE in the same folder. 19.2.1. Variation 1: Linked-Duration Two more conditions MUST be met: 1. ChapterTimeStart and ChapterTimeEnd timestamps MUST be in the range of the linked Segment duration. 2. ChapterSegmentEditionUID MUST NOT be set. A Matroska Player MUST play the content of the linked Segment from the ChapterTimeStart until ChapterTimeEnd timestamp. 19.2.2. Variation 2: Linked-Edition When the ChapterSegmentEditionUID is set to a valid EditionUID from the linked Segment. A Matroska Player MUST play these linked Edition. 19.3. Soft Linking Soft Linking is used by codec chapters. They can reference another Segment and jump to that Segment. The way the Segments are described are internal to the chapter codec and unknown to the Matroska level. But there are Elements within the Info Element (such as ChapterTranslate) that can translate a value representing a Segment in the chapter codec and to the current SegmentUID. All Segments that could be used in a Linked Segment in this way SHOULD be marked as members of the same family via the SegmentFamily Element, so that the Matroska Player can quickly switch from one to the other. 20. Track Flags 20.1. Default flag The "default track" flag is a hint for a Matroska Player indicating that a given track SHOULD be eligible to be automatically selected as the default track for a given language. If no tracks in a given language have the default track flag set, then all tracks in that language are eligible for automatic selection. This can be used to indicate that a track provides "regular service" suitable for users with default settings, as opposed to specialized services, such as commentary, hearing-impaired captions, or descriptive audio. Lhomme, et al. Expires 12 April 2022 [Page 134] Internet-Draft Matroska Format October 2021 The Matroska Player MAY override the "default track" flag for any reason, including user preferences to prefer tracks providing accessibility services. 20.2. Forced flag The "forced" flag tells the Matroska Player that it SHOULD display this subtitle track, even if user preferences usually would not call for any subtitles to be displayed alongside the current selected audio track. This can be used to indicate that a track contains translations of onscreen text, or of dialogue spoken in a different language than the track's primary one. 20.3. Hearing-impaired flag The "hearing impaired" flag tells the Matroska Player that it SHOULD prefer this track when selecting a default track for a hearing- impaired user, and that it MAY prefer to select a different track when selecting a default track for a non-hearing-impaired user. 20.4. Visual-impaired flag The "visual impaired" flag tells the Matroska Player that it SHOULD prefer this track when selecting a default track for a visually- impaired user, and that it MAY prefer to select a different track when selecting a default track for a non-visually-impaired user. 20.5. Descriptions flag The "descriptions" flag tells the Matroska Player that this track is suitable to play via a text-to-speech system for a visually-impaired user, and that it SHOULD NOT automatically select this track when selecting a default track for a non-visually-impaired user. 20.6. Original flag The "original" flag tells the Matroska Player that this track is in the original language, and that it SHOULD prefer it if configured to prefer original-language tracks of this track's type. 20.7. Commentary flag The "commentary" flag tells the Matroska Player that this track contains commentary on the content. Lhomme, et al. Expires 12 April 2022 [Page 135] Internet-Draft Matroska Format October 2021 20.8. Track Operation TrackOperation allows combining multiple tracks to make a virtual one. It uses two separate system to combine tracks. One to create a 3D "composition" (left/right/background planes) and one to simplify join two tracks together to make a single track. A track created with TrackOperation is a proper track with a UID and all its flags. However the codec ID is meaningless because each "sub" track needs to be decoded by its own decoder before the "operation" is applied. The Cues Elements corresponding to such a virtual track SHOULD be the sum of the Cues Elements for each of the tracks it's composed of (when the Cues are defined per track). In the case of TrackJoinBlocks, the Block Elements (from BlockGroup and SimpleBlock) of all the tracks SHOULD be used as if they were defined for this new virtual Track. When two Block Elements have overlapping start or end timestamps, it's up to the underlying system to either drop some of these frames or render them the way they overlap. This situation SHOULD be avoided when creating such tracks as you can never be sure of the end result on different platforms. 20.9. Overlay Track Overlay tracks SHOULD be rendered in the same channel as the track its linked to. When content is found in such a track, it SHOULD be played on the rendering channel instead of the original track. 20.10. Multi-planar and 3D videos There are two different ways to compress 3D videos: have each eye track in a separate track and have one track have both eyes combined inside (which is more efficient, compression-wise). Matroska supports both ways. For the single track variant, there is the StereoMode Element, which defines how planes are assembled in the track (mono or left-right combined). Odd values of StereoMode means the left plane comes first for more convenient reading. The pixel count of the track (PixelWidth/PixelHeight) is the raw amount of pixels, for example 3840x1080 for full HD side by side, and the DisplayWidth/ DisplayHeight in pixels is the amount of pixels for one plane (1920x1080 for that full HD stream). Old stereo 3D were displayed using anaglyph (cyan and red colors separated). For compatibility with such movies, there is a value of the StereoMode that corresponds to AnaGlyph. Lhomme, et al. Expires 12 April 2022 [Page 136] Internet-Draft Matroska Format October 2021 There is also a "packed" mode (values 13 and 14) which consists of packing two frames together in a Block using lacing. The first frame is the left eye and the other frame is the right eye (or vice versa). The frames SHOULD be decoded in that order and are possibly dependent on each other (P and B frames). For separate tracks, Matroska needs to define exactly which track does what. TrackOperation with TrackCombinePlanes do that. For more details look at Section 20.8 on how TrackOperation works. The 3D support is still in infancy and may evolve to support more features. The StereoMode used to be part of Matroska v2 but it didn't meet the requirement for multiple tracks. There was also a bug in libmatroska prior to 0.9.0 that would save/read it as 0x53B9 instead of 0x53B8. Matroska Readers may support these legacy files by checking Matroska v2 or 0x53B9. The older values were 0: mono, 1: right eye, 2: left eye, 3: both eyes. 21. Default track selection This section provides some example sets of Tracks and hypothetical user settings, along with indications of which ones a similarly- configured Matroska Player SHOULD automatically select for playback by default in such a situation. A player MAY provide additional settings with more detailed controls for more nuanced scenarios. These examples are provided as guidelines to illustrate the intended usages of the various supported Track flags, and their expected behaviors. Track names are shown in English for illustrative purposes; actual files may have titles in the language of each track, or provide titles in multiple languages. 21.1. Audio Selection Example track set: Lhomme, et al. Expires 12 April 2022 [Page 137] Internet-Draft Matroska Format October 2021 +===+=====+====+======+========+=======+================+===========+ |No.|Type |Lang|Layout|Original|Default|Other flags |Name | +===+=====+====+======+========+=======+================+===========+ |1 |Video|und |N/A |N/A |N/A |None | | +---+-----+----+------+--------+-------+----------------+-----------+ |2 |Audio|eng |5.1 |1 |1 |None | | +---+-----+----+------+--------+-------+----------------+-----------+ |3 |Audio|eng |2.0 |1 |1 |None | | +---+-----+----+------+--------+-------+----------------+-----------+ |4 |Audio|eng |2.0 |1 |0 |Visual-impaired |Descriptive| | | | | | | | |audio | +---+-----+----+------+--------+-------+----------------+-----------+ |5 |Audio|esp |5.1 |0 |1 |None | | +---+-----+----+------+--------+-------+----------------+-----------+ |6 |Audio|esp |2.0 |0 |0 |Visual-impaired |Descriptive| | | | | | | | |audio | +---+-----+----+------+--------+-------+----------------+-----------+ |7 |Audio|eng |2.0 |1 |0 |Commentary |Director's | | | | | | | | |Commentary | +---+-----+----+------+--------+-------+----------------+-----------+ |8 |Audio|eng |2.0 |1 |0 |None |Karaoke | +---+-----+----+------+--------+-------+----------------+-----------+ Table 42: Audio Tracks for default selection Here we have a file with 7 audio tracks, of which 5 are in English and 2 are in Spanish. The English tracks all have the Original flag, indicating that English is the original content language. Generally the player will first consider the track languages: if the player has an option to prefer original-language audio and the user has enabled it, then it should prefer one of the Original-flagged tracks. If configured to specifically prefer audio tracks in English or Spanish, the player should select one of the tracks in the corresponding language. The player may also wish to prefer an Original-flagged track if no tracks matching any of the user's explicitly-preferred languages are available. Two of the tracks have the Visual-impaired flag. If the player has been configured to prefer such tracks, it should select one; otherwise, it should avoid them if possible. If selecting an English track, when other settings have left multiple possible options, it may be useful to exclude the tracks that lack the Default flag: here, one provides descriptive service for the visually impaired (which has its own flag and may be automatically Lhomme, et al. Expires 12 April 2022 [Page 138] Internet-Draft Matroska Format October 2021 selected by user configuration, but is unsuitable for users with default-configured players), one is a commentary track (which has its own flag, which the player may or may not have specialized handling for), and the last contains karaoke versions of the music that plays during the film, which is an unusual specialized audio service that Matroska has no built-in support for indicating, so it's indicated in the track name instead. By not setting the Default flag on these specialized tracks, the file's author hints that they should not be automatically selected by a default-configured player. Having narrowed its choices down, our example player now may have to select between tracks 2 and 3. The only difference between these tracks is their channel layouts: 2 is 5.1 surround, while 3 is stereo. If the player is aware that the output device is a pair of headphones or stereo speakers, it may wish to prefer the stereo mix automatically. On the other hand, if it knows that the device is a surround system, it may wish to prefer the surround mix. If the player finishes analyzing all of the available audio tracks and finds that multiple seem equally and maximally preferable, it SHOULD default to the first of the group. 21.2. Subtitle selection Example track set: Lhomme, et al. Expires 12 April 2022 [Page 139] Internet-Draft Matroska Format October 2021 +===+===========+====+=========+=======+======+==========+==========+ |No.| Type |Lang|Original |Default|Forced| Other | Name | | | | | | | | flags | | +===+===========+====+=========+=======+======+==========+==========+ |1 | Video |und |N/A |N/A |N/A | None | | +---+-----------+----+---------+-------+------+----------+----------+ |2 | Audio |fra |1 |1 |N/A | None | | +---+-----------+----+---------+-------+------+----------+----------+ |3 | Audio |por |0 |1 |N/A | None | | +---+-----------+----+---------+-------+------+----------+----------+ |4 | Subtitles |fra |1 |1 |0 | None | | +---+-----------+----+---------+-------+------+----------+----------+ |5 | Subtitles |fra |1 |0 |0 | Hearing- | Captions | | | | | | | | impaired | for the | | | | | | | | | hearing- | | | | | | | | | impaired | +---+-----------+----+---------+-------+------+----------+----------+ |6 | Subtitles |por |0 |1 |0 | None | | +---+-----------+----+---------+-------+------+----------+----------+ |7 | Subtitles |por |0 |0 |1 | None | Signs | +---+-----------+----+---------+-------+------+----------+----------+ |8 | Subtitles |por |0 |0 |0 | Hearing- | SDH | | | | | | | | impaired | | +---+-----------+----+---------+-------+------+----------+----------+ Table 43: Subtitle Tracks for default selection Here we have 2 audio tracks and 5 subtitle tracks. As we can see, French is the original language. We'll start by discussing the case where the user prefers French (or Original-language) audio (or has explicitly selected the French audio track), and also prefers French subtitles. In this case, if the player isn't configured to display captions when the audio matches their preferred subtitle languages, the player doesn't need to select a subtitle track at all. If the user _has_ indicated that they want captions to be displayed, the selection simply comes down to whether Hearing-impaired subtitles are preferred. The situation for a user who prefers Portuguese subtitles starts out somewhat analogous. If they select the original French audio (either by explicit audio language preference, preference for Original- language tracks, or by explicitly selecting that track), then the selection once again comes down to the hearing-impaired preference. Lhomme, et al. Expires 12 April 2022 [Page 140] Internet-Draft Matroska Format October 2021 However, the case where the Portuguese audio track is selected has an important catch: a Forced track in Portuguese is present. This may contain translations of onscreen text from the video track, or of portions of the audio that are not translated (music, for instance). This means that even if the user's preferences wouldn't normally call for captions here, the Forced track should be selected nonetheless, rather than selecting no track at all. On the other hand, if the user's preferences _do_ call for captions, the non-Forced tracks should be preferred, as the Forced track will not contain captioning for the dialogue. 22. Chapters The Matroska Chapters system can have multiple Editions and each Edition can consist of Simple Chapters where a chapter start time is used as marker in the timeline only. An Edition can be more complex with Ordered Chapters where a chapter end time stamp is additionally used or much more complex with Linked Chapters. The Matroska Chapters system can also have a menu structure, borrowed from the DVD menu system, or have it's own Native Matroska menu structure. 22.1. EditionEntry The EditionEntry is also called an Edition. An Edition contains a set of Edition flags and MUST contain at least one ChapterAtom Element. Chapters are always inside an Edition (or a Chapter itself part of an Edition). Multiple Editions are allowed. Some of these Editions MAY be ordered and others not. 22.1.1. EditionFlagDefault Only one Edition SHOULD have an EditionFlagDefault flag set to true. 22.1.2. Default Edition The Default Edition is the Edition that a Matroska Player SHOULD use for playback by default. The first Edition with the EditionFlagDefault flag set to true is the Default Edition. When all EditionFlagDefault flags are set to false, then the first Edition is the Default Edition. Lhomme, et al. Expires 12 April 2022 [Page 141] Internet-Draft Matroska Format October 2021 +===========+=============+=================+ | Edition | FlagDefault | Default Edition | +===========+=============+=================+ | Edition 1 | true | X | +-----------+-------------+-----------------+ | Edition 2 | true | | +-----------+-------------+-----------------+ | Edition 3 | true | | +-----------+-------------+-----------------+ Table 44: Default edition, all default +===========+=============+=================+ | Edition | FlagDefault | Default Edition | +===========+=============+=================+ | Edition 1 | false | X | +-----------+-------------+-----------------+ | Edition 2 | false | | +-----------+-------------+-----------------+ | Edition 3 | false | | +-----------+-------------+-----------------+ Table 45: Default edition, no default +===========+=============+=================+ | Edition | FlagDefault | Default Edition | +===========+=============+=================+ | Edition 1 | false | | +-----------+-------------+-----------------+ | Edition 2 | true | X | +-----------+-------------+-----------------+ | Edition 3 | false | | +-----------+-------------+-----------------+ Table 46: Default edition, with default 22.1.3. EditionFlagOrdered The EditionFlagOrdered Flag is a significant feature as it enables an Edition of Ordered Chapters which defines and arranges a virtual timeline rather than simply labeling points within the timeline. For example, with Editions of Ordered Chapters a single Matroska file can present multiple edits of a film without duplicating content. Alternatively, if a videotape is digitized in full, one Ordered Edition could present the full content (including colorbars, countdown, slate, a feature presentation, and black frames), while another Edition of Ordered Chapters can use Chapters that only mark the intended presentation with the colorbars and other ancillary Lhomme, et al. Expires 12 April 2022 [Page 142] Internet-Draft Matroska Format October 2021 visual information excluded. If an Edition of Ordered Chapters is enabled, then the Matroska Player MUST play those Chapters in their stored order from the timestamp marked in the ChapterTimeStart Element to the timestamp marked in to ChapterTimeEnd Element. If the EditionFlagOrdered Flag is set to false, Simple Chapters are used and only the ChapterTimeStart of a Chapter is used as chapter mark to jump to the predefined point in the timeline. With Simple Chapters, a Matroska Player MUST ignore certain Chapter Elements. All these elements are now informational only. The following list shows the different Chapter elements only found in Ordered Chapters. +======================================+ | Ordered Chapter elements | +======================================+ | ChapterAtom/ChapterSegmentUID | +--------------------------------------+ | ChapterAtom/ChapterSegmentEditionUID | +--------------------------------------+ | ChapterAtom/ChapterTrack | +--------------------------------------+ | ChapterAtom/ChapProcess | +--------------------------------------+ | Info/SegmentFamily | +--------------------------------------+ | Info/ChapterTranslate | +--------------------------------------+ | TrackEntry/TrackTranslate | +--------------------------------------+ Table 47: elements only found in ordered chapters Furthermore there are other EBML Elements which could be used if the EditionFlagOrdered flag is set to true. 22.1.3.1. Ordered-Edition and Matroska Segment-Linking * Hard Linking: Ordered-Chapters supersedes the Hard Linking. * Soft Linking: In this complex system Ordered Chapters are REQUIRED and a Chapter CODEC MUST interpret the ChapProcess of all chapters. Lhomme, et al. Expires 12 April 2022 [Page 143] Internet-Draft Matroska Format October 2021 * Medium Linking: Ordered Chapters are used in a normal way and can be combined with the ChapterSegmentUID element which establishes a link to another Segment. See Section 19 on the Linked Segments for more information about Hard Linking, Soft Linking, and Medium Linking. 22.2. ChapterAtom The ChapterAtom is also called a Chapter. A Chapter element can be used recursively. Such a child Chapter is called Nested Chapter. 22.2.1. ChapterTimeStart The timestamp of the start of Chapter with nanosecond accuracy, not scaled by TimestampScale. For Simple Chapters this is the position of the chapter markers in the timeline. 22.2.2. ChapterTimeEnd The timestamp of the end of Chapter with nanosecond accuracy, not scaled by TimestampScale. The timestamp defined by the ChapterTimeEnd is not part of the Chapter. A Matroska Player calculates the duration of this Chapter using the difference between the ChapterTimeEnd and ChapterTimeStart. The end timestamp MUST be strictly greater than the start timestamp. +===========+=================+===============+===============+ | Chapter | Start timestamp | End timestamp | Duration | +===========+=================+===============+===============+ | Chapter 1 | 0 | 1000000000 | 1000000000 | +-----------+-----------------+---------------+---------------+ | Chapter 2 | 1000000000 | 5000000000 | 4000000000 | +-----------+-----------------+---------------+---------------+ | Chapter 3 | 6000000000 | 6000000000 | Invalid (0) | +-----------+-----------------+---------------+---------------+ | Chapter 4 | 9000000000 | 8000000000 | Invalid | | | | | (-1000000000) | +-----------+-----------------+---------------+---------------+ Table 48: ChapterTimeEnd usage possibilities 22.2.3. ChapterFlagHidden Each Chapter ChapterFlagHidden flag works independently from parent chapters. A Nested Chapter with ChapterFlagHidden flag set to false remains visible even if the Parent Chapter ChapterFlagHidden flag is set to true. Lhomme, et al. Expires 12 April 2022 [Page 144] Internet-Draft Matroska Format October 2021 +==========================+===================+=========+ | Chapter + Nested Chapter | ChapterFlagHidden | visible | +==========================+===================+=========+ | Chapter 1 | false | yes | +--------------------------+-------------------+---------+ | Nested Chapter 1.1 | false | yes | +--------------------------+-------------------+---------+ | Nested Chapter 1.2 | true | no | +--------------------------+-------------------+---------+ | Chapter 2 | true | no | +--------------------------+-------------------+---------+ | Nested Chapter 2.1 | false | yes | +--------------------------+-------------------+---------+ | Nested Chapter 2.2 | true | no | +--------------------------+-------------------+---------+ Table 49: ChapterFlagHidden nested visibility 22.3. Menu features The menu features are handled like a chapter codec. That means each codec has a type, some private data and some data in the chapters. The type of the menu system is defined by the ChapProcessCodecID parameter. For now, only 2 values are supported : 0 matroska script, 1 menu borrowed from the DVD. The private data depend on the type of menu system (stored in ChapProcessPrivate), idem for the data in the chapters (stored in ChapProcessData). The menu system, as well a Chapter Codecs in general, can do actions on the Matroska Player like jumping to another Chapter or Edition, selecting different tracks and possibly more. The scope of all the possibilities of Chapter Codecs is not covered in this document as it depends on the Chapter Codec features and its integration in a Matroska Player. 22.4. Physical Types Each level can have different meanings for audio and video. The ORIGINAL_MEDIUM tag can be used to specify a string for ChapterPhysicalEquiv = 60. Here is the list of possible levels for both audio and video: Lhomme, et al. Expires 12 April 2022 [Page 145] Internet-Draft Matroska Format October 2021 +=======+=======================+=============+=====================+ | Value | Audio | Video | Comment | +=======+=======================+=============+=====================+ | 70 | SET / PACKAGE | SET / | the collection of | | | | PACKAGE | different media | +-------+-----------------------+-------------+---------------------+ | 60 | CD / 12" / 10" / 7" / | DVD / VHS | the physical medium | | | TAPE / MINIDISC / DAT | / | like a CD or a DVD | | | | LASERDISC | | +-------+-----------------------+-------------+---------------------+ | 50 | SIDE | SIDE | when the original | | | | | medium (LP/DVD) has | | | | | different sides | +-------+-----------------------+-------------+---------------------+ | 40 | - | LAYER | another physical | | | | | level on DVDs | +-------+-----------------------+-------------+---------------------+ | 30 | SESSION | SESSION | as found on CDs and | | | | | DVDs | +-------+-----------------------+-------------+---------------------+ | 20 | TRACK | - | as found on audio | | | | | CDs | +-------+-----------------------+-------------+---------------------+ | 10 | INDEX | - | the first logical | | | | | level of the side/ | | | | | medium | +-------+-----------------------+-------------+---------------------+ Table 50: ChapterPhysicalEquiv meaning per track type 22.5. Chapter Examples 22.5.1. Example 1 : basic chaptering In this example a movie is split in different chapters. It could also just be an audio file (album) on which each track corresponds to a chapter. * 00000ms - 05000ms : Intro * 05000ms - 25000ms : Before the crime * 25000ms - 27500ms : The crime * 27500ms - 38000ms : The killer arrested * 38000ms - 43000ms : Credits Lhomme, et al. Expires 12 April 2022 [Page 146] Internet-Draft Matroska Format October 2021 This would translate in the following matroska form : 16603393396715046047 1193046 0 5000000000 Intro 2311527 5000000000 25000000000 Before the crime Avant le crime fra 3430008 25000000000 27500000000 The crime Le crime fra 4548489 27500000000 38000000000 After the crime Après le crime fra Lhomme, et al. Expires 12 April 2022 [Page 147] Internet-Draft Matroska Format October 2021 5666960 38000000000 43000000000 Credits Générique fra Figure 12: Basic Chapters Example. 22.5.2. Example 2 : nested chapters In this example an (existing) album is split into different chapters, and one of them contain another splitting. 22.5.2.1. The Micronauts "Bleep To Bleep" * 00:00 - 12:28 : Baby Wants To Bleep/Rock - 00:00 - 04:38 : Baby wants to bleep (pt.1) - 04:38 - 07:12 : Baby wants to rock - 07:12 - 10:33 : Baby wants to bleep (pt.2) - 10:33 - 12:28 : Baby wants to bleep (pt.3) * 12:30 - 19:38 : Bleeper_O+2 * 19:40 - 22:20 : Baby wants to bleep (pt.4) * 22:22 - 25:18 : Bleep to bleep * 25:20 - 33:35 : Baby wants to bleep (k) * 33:37 - 44:28 : Bleeper Lhomme, et al. Expires 12 April 2022 [Page 148] Internet-Draft Matroska Format October 2021 1281690858003401414 1 0 748000000 Baby wants to Bleep/Rock 2 0 278000000 Baby wants to bleep (pt.1) 3 278000000 432000000 Baby wants to rock 4 432000000 633000000 Baby wants to bleep (pt.2) 5 633000000 748000000 Baby wants to bleep (pt.3) 6 750000000 1178500000 Lhomme, et al. Expires 12 April 2022 [Page 149] Internet-Draft Matroska Format October 2021 Bleeper_O+2 7 1180500000 1340000000 Baby wants to bleep (pt.4) 8 1342000000 1518000000 Bleep to bleep 9 1520000000 2015000000 Baby wants to bleep (k) 10 2017000000 2668000000 Bleeper Figure 13: Nested Chapters Example. 23. Attachments Matroska supports storage of related files and data in the Attachments Element (a Top-Level Element). Attachment Elements can be used to store related cover art, font files, transcripts, reports, error recovery files, picture, or text-based annotations, copies of specifications, or other ancillary files related to the Segment. Lhomme, et al. Expires 12 April 2022 [Page 150] Internet-Draft Matroska Format October 2021 Matroska Readers MUST NOT execute files stored as Attachment Elements. 23.1. Cover Art This section defines a set of guidelines for the storage of cover art in Matroska files. A Matroska Reader MAY use embedded cover art to display a representational still-image depiction of the multimedia contents of the Matroska file. Only JPEG and PNG image formats SHOULD be used for cover art pictures. There can be two different covers for a movie/album: a portrait style (e.g., a DVD case) and a landscape style (e.g., a wide banner ad). There can be two versions of the same cover, the normal cover and the small cover. The dimension of the normal cover SHOULD be 600 pixels on the smallest side -- for example, 960x600 for landscape, 600x800 for portrait, or 600x600 for square. The dimension of the small cover SHOULD be 120 pixels on the smallest side -- for example, 192x120 or 120x160. Versions of cover art can be differentiated by the filename, which is stored in the FileName Element. The default filename of the normal cover in square or portrait mode is cover.(jpg|png). When stored, the normal cover SHOULD be the first Attachment in storage order. The small cover SHOULD be prefixed with "small_", such as small_cover.(jpg|png). The landscape variant SHOULD be suffixed with "_land", such as cover_land.(jpg|png). The filenames are case sensitive. The following table provides examples of file names for cover art in Attachments. Lhomme, et al. Expires 12 April 2022 [Page 151] Internet-Draft Matroska Format October 2021 +======================+===================+=================+ | FileName | Image Orientation | Pixel Length of | | | | Smallest Side | +======================+===================+=================+ | cover.jpg | Portrait or | 600 | | | square | | +----------------------+-------------------+-----------------+ | small_cover.png | Portrait or | 120 | | | square | | +----------------------+-------------------+-----------------+ | cover_land.png | Landscape | 600 | +----------------------+-------------------+-----------------+ | small_cover_land.jpg | Landscape | 120 | +----------------------+-------------------+-----------------+ Table 51: Cover Art Filenames 24. Cues The Cues Element provides an index of certain Cluster Elements to allow for optimized seeking to absolute timestamps within the Segment. The Cues Element contains one or many CuePoint Elements which each MUST reference an absolute timestamp (via the CueTime Element), a Track (via the CueTrack Element), and a Segment Position (via the CueClusterPosition Element). Additional non-mandated Elements are part of the CuePoint Element such as CueDuration, CueRelativePosition, CueCodecState and others which provide any Matroska Reader with additional information to use in the optimization of seeking performance. 24.1. Recommendations The following recommendations are provided to optimize Matroska performance. * Unless Matroska is used as a live stream, it SHOULD contain a Cues Element. * For each video track, each keyframe SHOULD be referenced by a CuePoint Element. * It is RECOMMENDED to not reference non-keyframes of video tracks in Cues unless it references a Cluster Element which contains a CodecState Element but no keyframes. * For each subtitle track present, each subtitle frame SHOULD be referenced by a CuePoint Element with a CueDuration Element. Lhomme, et al. Expires 12 April 2022 [Page 152] Internet-Draft Matroska Format October 2021 * References to audio tracks MAY be skipped in CuePoint Elements if a video track is present. When included the CuePoint Elements SHOULD reference audio keyframes at most once every 500 milliseconds. * If the referenced frame is not stored within the first SimpleBlock, or first BlockGroup within its Cluster Element, then the CueRelativePosition Element SHOULD be written to reference where in the Cluster the reference frame is stored. * If a CuePoint Element references Cluster Element that includes a CodecState Element, then that CuePoint Element MUST use a CueCodecState Element. * CuePoint Elements SHOULD be numerically sorted in storage order by the value of the CueTime Element. 25. Matroska Streaming In Matroska, there are two kinds of streaming: file access and livestreaming. 25.1. File Access File access can simply be reading a file located on your computer, but also includes accessing a file from an HTTP (web) server or CIFS (Windows share) server. These protocols are usually safe from reading errors and seeking in the stream is possible. However, when a file is stored far away or on a slow server, seeking can be an expensive operation and SHOULD be avoided. The following guidelines, when followed, help reduce the number of seeking operations for regular playback and also have the playback start quickly without a lot of data needed to read first (like a Cues Element, Attachment Element or SeekHead Element). Matroska, having a small overhead, is well suited for storing music/ videos on file servers without a big impact on the bandwidth used. Matroska does not require the index to be loaded before playing, which allows playback to start very quickly. The index can be loaded only when seeking is requested the first time. Lhomme, et al. Expires 12 April 2022 [Page 153] Internet-Draft Matroska Format October 2021 25.2. Livestreaming Livestreaming is the equivalent of television broadcasting on the internet. There are 2 families of servers for livestreaming: RTP/ RTSP and HTTP. Matroska is not meant to be used over RTP. RTP already has timing and channel mechanisms that would be wasted if doubled in Matroska. Additionally, having the same information at the RTP and Matroska level would be a source of confusion if they do not match. Livestreaming of Matroska over HTTP (or any other plain protocol based on TCP) is possible. A live Matroska stream is different from a file because it usually has no known end (only ending when the client disconnects). For this, all bits of the "size" portion of the Segment Element MUST be set to 1. Another option is to concatenate Segment Elements with known sizes, one after the other. This solution allows a change of codec/resolution between each segment. For example, this allows for a switch between 4:3 and 16:9 in a television program. When Segment Elements are continuous, certain Elements, like MetaSeek, Cues, Chapters, and Attachments, MUST NOT be used. It is possible for a Matroska Player to detect that a stream is not seekable. If the stream has neither a MetaSeek list or a Cues list at the beginning of the stream, it SHOULD be considered non-seekable. Even though it is possible to seek blindly forward in the stream, it is NOT RECOMMENDED. In the context of live radio or web TV, it is possible to "tag" the content while it is playing. The Tags Element can be placed between Clusters each time it is necessary. In that case, the new Tags Element MUST reset the previously encountered Tags Elements and use the new values instead. 26. IANA Considerations 26.1. Matroska Element IDs Registry 26.2. ChapterCodecID Registry 26.3. Historic Deprecated Element IDs Registry As Matroska evolved since 2002 many parts that were considered for use in the format were never used and often incorrectly designed. Many of the elements that were then defined are not found in any known files but were part of public specs. DivX also had a few custom elements that were designed for custom features. Lhomme, et al. Expires 12 April 2022 [Page 154] Internet-Draft Matroska Format October 2021 We list these elements that have a known ID that SHOULD NOT be reused to avoid colliding with existing files. 26.3.1. SilentTracks Element path: \Segment\Cluster\SilentTracks id: 0x5854 type: master definition: The list of tracks that are not used in that part of the stream. It is useful when using overlay tracks on seeking or to decide what track to use. 26.3.2. SilentTrackNumber Element path: \Segment\Cluster\SilentTracks\SilentTrackNumber id: 0x58D7 type: uinteger definition: One of the track number that are not used from now on in the stream. It could change later if not specified as silent in a further Cluster. 26.3.3. BlockVirtual Element path: \Segment\Cluster\BlockGroup\BlockVirtual id: 0xA2 type: binary definition: A Block with no data. It MUST be stored in the stream at the place the real Block would be in display order. 26.3.4. ReferenceVirtual Element path: \Segment\Cluster\BlockGroup\ReferenceVirtual id: 0xFD type: integer definition: The Segment Position of the data that would otherwise be in position of the virtual block. Lhomme, et al. Expires 12 April 2022 [Page 155] Internet-Draft Matroska Format October 2021 26.3.5. FrameNumber Element path: \Segment\Cluster\BlockGroup\Slices\TimeSlice\FrameNumber id: 0xCD type: uinteger definition: The number of the frame to generate from this lace with this delay (allow you to generate many frames from the same Block/ Frame). 26.3.6. BlockAdditionID Element path: \Segment\Cluster\BlockGroup\Slices\TimeSlice\BlockAdditionID id: 0xCB type: uinteger definition: The ID of the BlockAdditional Element (0 is the main Block). 26.3.7. Delay Element path: \Segment\Cluster\BlockGroup\Slices\TimeSlice\Delay id: 0xCE type: uinteger definition: The (scaled) delay to apply to the Element. 26.3.8. SliceDuration Element path: \Segment\Cluster\BlockGroup\Slices\TimeSlice\SliceDuration id: 0xCF type: uinteger definition: The (scaled) duration to apply to the Element. 26.3.9. ReferenceFrame Element path: \Segment\Cluster\BlockGroup\ReferenceFrame id: 0xC8 Lhomme, et al. Expires 12 April 2022 [Page 156] Internet-Draft Matroska Format October 2021 type: master definition: Contains information about the last reference frame. See [DivXTrickTrack]. 26.3.10. ReferenceOffset Element path: \Segment\Cluster\BlockGroup\ReferenceFrame\ReferenceOffset id: 0xC9 type: uinteger definition: The relative offset, in bytes, from the previous BlockGroup element for this Smooth FF/RW video track to the containing BlockGroup element. See [DivXTrickTrack]. 26.3.11. ReferenceTimestamp Element path: \Segment\Cluster\BlockGroup\ReferenceFrame\ReferenceTimestamp id: 0xCA type: uinteger definition: The timecode of the BlockGroup pointed to by ReferenceOffset. See [DivXTrickTrack]. 26.3.12. EncryptedBlock Element path: \Segment\Cluster\EncryptedBlock id: 0xAF type: binary definition: Similar to SimpleBlock, see Section 12.4, but the data inside the Block are Transformed (encrypt and/or signed). 26.3.13. TrackOffset Element path: \Segment\Tracks\TrackEntry\TrackOffset id: 0x537F type: integer definition: A value to add to the Block's Timestamp. This can be Lhomme, et al. Expires 12 April 2022 [Page 157] Internet-Draft Matroska Format October 2021 used to adjust the playback offset of a track. 26.3.14. CodecSettings Element path: \Segment\Tracks\TrackEntry\CodecSettings id: 0x3A9697 type: utf-8 definition: A string describing the encoding setting used. 26.3.15. CodecInfoURL Element path: \Segment\Tracks\TrackEntry\CodecInfoURL id: 0x3B4040 type: string definition: A URL to find information about the codec used. 26.3.16. CodecDownloadURL Element path: \Segment\Tracks\TrackEntry\CodecDownloadURL id: 0x26B240 type: string definition: A URL to download about the codec used. 26.3.17. CodecDecodeAll Element path: \Segment\Tracks\TrackEntry\CodecDecodeAll id: 0xAA type: uinteger definition: Set to 1 if the codec can decode potentially damaged data. 26.3.18. OldStereoMode Element path: \Segment\Tracks\TrackEntry\Video\OldStereoMode id: 0x53B9 Lhomme, et al. Expires 12 April 2022 [Page 158] Internet-Draft Matroska Format October 2021 type: uinteger definition: DEPRECATED, DO NOT USE. Bogus StereoMode value used in old versions of libmatroska. 26.3.19. AspectRatioType Element path: \Segment\Tracks\TrackEntry\Video\AspectRatioType id: 0x54B3 type: uinteger definition: Specify the possible modifications to the aspect ratio. 26.3.20. GammaValue Element path: \Segment\Tracks\TrackEntry\Video\GammaValue id: 0x2FB523 type: float definition: Gamma Value. 26.3.21. FrameRate Element path: \Segment\Tracks\TrackEntry\Video\FrameRate id: 0x2383E3 type: float definition: Number of frames per second. This value is Informational only. It is intended for constant frame rate streams, and SHOULD NOT be used for a variable frame rate TrackEntry. 26.3.22. ChannelPositions Element path: \Segment\Tracks\TrackEntry\Audio\ChannelPositions id: 0x7D7B type: binary definition: Table of horizontal angles for each successive channel. Lhomme, et al. Expires 12 April 2022 [Page 159] Internet-Draft Matroska Format October 2021 26.3.23. TrickTrackUID Element path: \Segment\Tracks\TrackEntry\TrickTrackUID id: 0xC0 type: uinteger definition: The TrackUID of the Smooth FF/RW video in the paired EBML structure corresponding to this video track. See [DivXTrickTrack]. 26.3.24. TrickTrackSegmentUID Element path: \Segment\Tracks\TrackEntry\TrickTrackSegmentUID id: 0xC1 type: binary definition: The SegmentUID of the Segment containing the track identified by TrickTrackUID. See [DivXTrickTrack]. 26.3.25. TrickTrackFlag Element path: \Segment\Tracks\TrackEntry\TrickTrackFlag id: 0xC6 type: uinteger definition: Set to 1 if this video track is a Smooth FF/RW track. If set to 1, MasterTrackUID and MasterTrackSegUID should must be present and BlockGroups for this track must contain ReferenceFrame structures. Otherwise, TrickTrackUID and TrickTrackSegUID must be present if this track has a corresponding Smooth FF/RW track. See [DivXTrickTrack]. 26.3.26. TrickMasterTrackUID Element path: \Segment\Tracks\TrackEntry\TrickMasterTrackUID id: 0xC7 type: uinteger definition: The TrackUID of the video track in the paired EBML Lhomme, et al. Expires 12 April 2022 [Page 160] Internet-Draft Matroska Format October 2021 structure that corresponds to this Smooth FF/RW track. See [DivXTrickTrack]. 26.3.27. TrickMasterTrackSegmentUID Element path: \Segment\Tracks\TrackEntry\TrickMasterTrackSegmentUID id: 0xC4 type: binary definition: The SegmentUID of the Segment containing the track identified by MasterTrackUID. See [DivXTrickTrack]. 26.3.28. ContentSignature Element path: \Segment\Tracks\TrackEntry\ContentEncodings\ContentEncoding\Co ntentEncryption\ContentSignature id: 0x47E3 type: binary definition: A cryptographic signature of the contents. 26.3.29. ContentSigKeyID Element path: \Segment\Tracks\TrackEntry\ContentEncodings\ContentEncoding\Co ntentEncryption\ContentSigKeyID id: 0x47E4 type: binary definition: This is the ID of the private key the data was signed with. 26.3.30. ContentSigAlgo Element path: \Segment\Tracks\TrackEntry\ContentEncodings\ContentEncoding\Co ntentEncryption\ContentSigAlgo id: 0x47E5 type: uinteger definition: The algorithm used for the signature. Lhomme, et al. Expires 12 April 2022 [Page 161] Internet-Draft Matroska Format October 2021 26.3.31. ContentSigHashAlgo Element path: \Segment\Tracks\TrackEntry\ContentEncodings\ContentEncoding\Co ntentEncryption\ContentSigHashAlgo id: 0x47E6 type: uinteger definition: The hash algorithm used for the signature. 26.3.32. CueRefCluster Element path: \Segment\Cues\CuePoint\CueTrackPositions\CueReference\CueRefCl uster id: 0x97 type: uinteger definition: The Segment Position of the Cluster containing the referenced Block. 26.3.33. CueRefNumber Element path: \Segment\Cues\CuePoint\CueTrackPositions\CueReference\CueRefNu mber id: 0x535F type: uinteger definition: Number of the referenced Block of Track X in the specified Cluster. 26.3.34. CueRefCodecState Element path: \Segment\Cues\CuePoint\CueTrackPositions\CueReference\CueRefCo decState id: 0xEB type: uinteger definition: The Segment Position of the Codec State corresponding to this referenced Element. 0 means that the data is taken from the initial Track Entry. Lhomme, et al. Expires 12 April 2022 [Page 162] Internet-Draft Matroska Format October 2021 26.3.35. FileReferral Element path: \Segment\Attachments\AttachedFile\FileReferral id: 0x4675 type: binary definition: A binary value that a track/codec can refer to when the attachment is needed. 26.3.36. FileUsedStartTime Element path: \Segment\Attachments\AttachedFile\FileUsedStartTime id: 0x4661 type: uinteger definition: The timecode at which this optimized font attachment comes into context, based on the Segment TimecodeScale. This element is reserved for future use and if written must be the segment start time. See [DivXWorldFonts]. 26.3.37. FileUsedEndTime Element path: \Segment\Attachments\AttachedFile\FileUsedEndTime id: 0x4662 type: uinteger definition: The timecode at which this optimized font attachment goes out of context, based on the Segment TimecodeScale. This element is reserved for future use and if written must be the segment end time. See [DivXWorldFonts]. 26.3.38. TagDefaultBogus Element path: \Segment\Tags\Tag\+SimpleTag\TagDefaultBogus id: 0x44B4 type: uinteger definition: A variant of the TagDefault element with a bogus Element ID; see Section 8.1.8.1.2.4. Lhomme, et al. Expires 12 April 2022 [Page 163] Internet-Draft Matroska Format October 2021 27. Normative References [BCP47] Phillips, A., Ed. and M. Davis, Ed., "Tags for Identifying Languages", DOI 10.17487/RFC5646, September 2009, . [Blowfish] Schneier, B., "The Blowfish Encryption Algorithm", 1993, . [BZIP2] Seward, J., "bzip2", 18 July 1996, . [FIPS.197] US National Institute of Standards and Technology, "Advanced Encryption Standard (AES)", DOI 10.6028/NIST.FIPS.197, 26 November 2001, . [FIPS.46-3] US National Institute of Standards and Technology, "Data Encryption Standard (DES)", FIPS PUB 46, 25 October 1999, . [IANADomains] "IANA Root Zone Database", . [IANALangRegistry] "IANA Language Subtag Registry", 28 February 2013, . [ISO3166-1] International Organization for Standardization, "Codes for the representation of names of countries and their subdivisions -- Part 1: Country code", ISO 3166-1:2020, August 2020, . [ISO639-2] United States Library Of Congress, "Codes for the Representation of Names of Languages", ISO 639-2:1998, 21 December 2017, . [LZO] Tarreau, W., Rodgman, R., and M. Oberhumer, "Lempel–Ziv–Oberhumer compression", 30 October 2018, . Lhomme, et al. Expires 12 April 2022 [Page 164] Internet-Draft Matroska Format October 2021 [MatroskaCodec] Lhomme, S., Bunkus, M., and D. Rice, "Media Container Codec Specifications", Work in Progress, Internet-Draft, draft-ietf-cellar-codec-06, 12 April 2021, . [MatroskaTags] Lhomme, S., Bunkus, M., and D. Rice, "Matroska Media Container Tag Specifications", Work in Progress, Internet- Draft, draft-ietf-cellar-tags-06, 12 April 2021, . [RFC1851] Karn, P., Metzger, P., and W. Simpson, "The ESP Triple DES Transform", RFC 1851, DOI 10.17487/RFC1851, September 1995, . [RFC1950] Deutsch, P. and J-L. Gailly, "ZLIB Compressed Data Format Specification version 3.3", RFC 1950, DOI 10.17487/RFC1950, May 1996, . [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997, . [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, May 2017, . [RFC8794] Lhomme, S., Rice, D., and M. Bunkus, "Extensible Binary Meta Language", RFC 8794, DOI 10.17487/RFC8794, July 2020, . [Twofish] Schneier, B., Kelsey, J., Whiting, D., Wagner, D., Hall, C., and N. Ferguson, "Twofish: A 128-Bit Block Cipher", 15 June 1998, . [WebVTT] Pieters, S., Pfeiffer, S., Ed., Jägenstedt, P., and I. Hickson, "WebVTT Cue Identifier", 4 April 2019, . 28. Informative References Lhomme, et al. Expires 12 April 2022 [Page 165] Internet-Draft Matroska Format October 2021 [DivXTrickTrack] "DivX Trick Track Extensions", 14 December 2010, . [DivXWorldFonts] "DivX World Fonts Extensions", 14 December 2010, . [MCF] "Media Container Format", 17 July 2002, . Authors' Addresses Steve Lhomme Email: slhomme@matroska.org Moritz Bunkus Email: moritz@bunkus.org Dave Rice Email: dave@dericed.com Lhomme, et al. Expires 12 April 2022 [Page 166]