Matroska Media Container Format Specifications

Introduction Matroska aims to become THE standard of multimedia container formats. It was derived from a project called , but differentiates from it significantly because it is based on EBML (Extensible Binary Meta Language) , 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)
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.

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. But since it's quite complete it is used as a reference for the development of libmatroska. A legacy version of the specification can be found here (PDF doc by Alexander Noé -- outdated). For a simplified diagram of the layout of a Matroska file, see the Diagram page. The table found below is now generated from the "source" of the Matroska specification. This XML file is also used to generate the semantic data used in libmatroska and libmatroska2. We encourage anyone to use and monitor its changes so your code is spec-proof and always up to date. Note that versions 1, 2, and 3 have been finalized. Version 4 is currently work in progress. There MAY be further additions to v4.

Security Considerations Matroska inherits security considerations from EBML. Attacks on a Matroska Reader could include:

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.

IANA Considerations To be determined.

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 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.

Basis in EBML Matroska is a Document Type of EBML (Extensible Binary Meta Language). This specification is dependent on the EBML Specification . 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).

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.

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

Language Codes Matroska from version 1 through 3 uses language codes that can be either the 3 letters bibliographic ISO-639-2 form (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 ISO 639-2 or BCP 47 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 as used for internet domains.

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:

ChapterPhysicalEquiv	Audio	Video	Comment
70	SET / PACKAGE	SET / PACKAGE	the collection of different media
60	CD / 12" / 10" / 7" / TAPE / MINIDISC / DAT	DVD / VHS / LASERDISC	the physical medium like a CD or a DVD
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

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.

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)

Block Header Flags

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

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:

Xiph, inspired by what is found in the Ogg container
EBML, which is the same with sizes coded differently
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:

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.

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 -(2⁶-1) to 2⁶-1 (ie 0 to 2⁷-2 minus 2⁶-1, half of the range)
01xx xxxx xxxx xxxx	value -(2¹³-1) to 2¹³-1
001x xxxx xxxx xxxx xxxx xxxx	value -(2²⁰-1) to 2²⁰-1
0001 xxxx xxxx xxxx xxxx xxxx xxxx xxxx	value -(2²⁷-1) to 2²⁷-1
0000 1xxx xxxx xxxx xxxx xxxx xxxx xxxx xxxx xxxx	value -(2³⁴-1) to 2³⁴-1
0000 01xx xxxx xxxx xxxx xxxx xxxx xxxx xxxx xxxx xxxx xxxx	value -(2⁴¹-1) to 2⁴¹-1
0000 001x xxxx xxxx xxxx xxxx xxxx xxxx xxxx xxxx xxxx xxxx xxxx xxxx	value -(2⁴⁸-1) to 2⁴⁸-1

Block head (with lacing bits set to 11)
Lacing head: Number of frames in the lace -1 -- i.e. 2 (the 800 and 500 octets one)
Lacing sizes: only the 2 first ones will be coded, 800 gives 0x320 0x4000 = 0x4320, 500 is coded as -300 : - 0x12C + 0x1FFF + 0x4000 = 0x5ED3. The size of the last frame is deduced from the total size of the Block.
Data in frame 1
Data in frame 2
Data in frame 3

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

SimpleBlock Structure The SimpleBlock is inspired by the Block structure; see . 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.

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)

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

Laced Data When lacing bit is set.

Offset	Player	Description
0x00	MUST	Number of frames in the lace-1 (uint8)
0x01 / 0xXX	MUST*	Lace-coded size of each frame of the lace, 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).

For (possibly) Laced Data

Offset	Player	Description
0x00	MUST	Consecutive laced frames

Matroska Structure A Matroska file MUST be composed of at least one EBML Document using the Matroska Document Type. Each EBML Document MUST start with an EBML Header and MUST be followed by the EBML Root Element, defined as Segment in Matroska. Matroska defines several Top Level Elements which MAY occur within the Segment. As an example, a simple Matroska file consisting of a single EBML Document could be represented like this:

EBML Header
Segment

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

EBML Header
Segment
EBML Header
Segment

The following diagram represents a simple Matroska file, comprised of an EBML Document with an EBML Header, a Segment Element (the Root Element), and all eight Matroska Top Level Elements. In the following diagrams of this section, horizontal spacing expresses a parent-child relationship between Matroska Elements (e.g., the Info Element is contained within the Segment Element) whereas vertical alignment represents the storage order within the file. +-------------+ | EBML Header | +---------------------------+ | Segment | SeekHead | | |-------------| | | Info | | |-------------| | | Tracks | | |-------------| | | Chapters | | |-------------| | | Cluster | | |-------------| | | Cues | | |-------------| | | Attachments | | |-------------| | | Tags | +---------------------------+ The Matroska EBML Schema defines eight Top Level Elements: SeekHead, Info, Tracks, Chapters, Cluster, Cues, Attachments, and Tags. The SeekHead Element (also known as MetaSeek) contains an index of Top Level Elements locations within the Segment. Use of the SeekHead Element is RECOMMENDED. Without a SeekHead Element, a Matroska parser would have to search the entire file to find all of the other Top Level Elements. This is due to Matroska's flexible ordering requirements; for instance, it is acceptable for the Chapters Element to be stored after the Cluster Elements.

Representation of a SeekHead Element. +--------------------------------+ | SeekHead | Seek | SeekID | | | |--------------| | | | SeekPosition | +--------------------------------+ 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.

Representation of an Info Element and its Child Elements. +-------------------------+ | Info | SegmentUID | | |------------------| | | SegmentFilename | | |------------------| | | PrevUID | | |------------------| | | PrevFilename | | |------------------| | | NextUID | | |------------------| | | NextFilename | | |------------------| | | SegmentFamily | | |------------------| | | ChapterTranslate | | |------------------| | | TimestampScale | | |------------------| | | Duration | | |------------------| | | DateUTC | | |------------------| | | Title | | |------------------| | | MuxingApp | | |------------------| | | WritingApp | |-------------------------| The Tracks Element defines the technical details for each track and can store the name, number, unique identifier, language, and type (audio, video, subtitles, etc.) of each track. For example, the Tracks Element MAY store information about the resolution of a video track or sample rate of an audio track. The Tracks Element MUST identify all the data needed by the codec to decode the data of the specified track. However, the data required is contingent on the codec used for the track. For example, a Track Element for uncompressed audio only requires the audio bit rate to be present. A codec such as AC-3 would require that the CodecID Element be present for all tracks, as it is the primary way to identify which codec to use to decode the track.

Representation of the Tracks Element and a selection of its Descendant Elements. +------------------------------------+ | 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 | |--------------------------------------------------------| The Chapters Element lists all of the chapters. Chapters are a way to set predefined points to jump to in video or audio.

Representation of the Chapters Element and a selection of its Descendant Elements. +-----------------------------------------+ | Chapters | Edition | EditionUID | | | Entry |--------------------| | | | EditionFlagHidden | | | |--------------------| | | | EditionFlagDefault | | | |--------------------| | | | EditionFlagOrdered | | | |---------------------------------+ | | | ChapterAtom | ChapterUID | | | | |-------------------| | | | | ChapterStringUID | | | | |-------------------| | | | | ChapterTimeStart | | | | |-------------------| | | | | ChapterTimeEnd | | | | |-------------------| | | | | ChapterFlagHidden | | | | |-------------------------------+ | | | | ChapterDisplay | ChapString | | | | | |--------------| | | | | | ChapLanguage | +------------------------------------------------------------------+ 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.

Representation of a Cluster Element and its immediate Child Elements. +--------------------------+ | Cluster | Timestamp | | |----------------| | | SilentTracks | | |----------------| | | Position | | |----------------| | | PrevSize | | |----------------| | | SimpleBlock | | |----------------| | | BlockGroup | | |----------------| | | EncryptedBlock | +--------------------------+

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

Representation of a Cues Element and two levels of its Descendant Elements. +-------------------------------------+ | Cues | CuePoint | CueTime | | | |-------------------| | | | CueTrackPositions | | |------------------------------| | | CuePoint | CueTime | | | |-------------------| | | | CueTrackPositions | +-------------------------------------+ 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.

Representation of a Attachments Element. +------------------------------------------------+ | Attachments | AttachedFile | FileDescription | | | |-------------------| | | | FileName | | | |-------------------| | | | FileMimeType | | | |-------------------| | | | FileData | | | |-------------------| | | | FileUID | | | |-------------------| | | | FileName | | | |-------------------| | | | FileReferral | | | |-------------------| | | | FileUsedStartTime | | | |-------------------| | | | FileUsedEndTime | +------------------------------------------------+ 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.

Representation of a Tags Element and three levels of its Children Elements. +-------------------------------------------+ | Tags | Tag | Targets | TargetTypeValue | | | | |------------------| | | | | TargetType | | | | |------------------| | | | | TagTrackUID | | | | |------------------| | | | | TagEditionUID | | | | |------------------| | | | | TagChapterUID | | | | |------------------| | | | | TagAttachmentUID | | | |------------------------------| | | | SimpleTag | TagName | | | | |------------------| | | | | TagLanguage | | | | |------------------| | | | | TagDefault | | | | |------------------| | | | | TagString | | | | |------------------| | | | | TagBinary | | | | |------------------| | | | | SimpleTag | +-------------------------------------------+

Matroska Additions to Schema Element Attributes In addition to the EBML Schema definition provided by the EBML Specification, Matroska adds the following additional attributes:

attribute name	required	definition
webm	No	A boolean to express if the Matroska Element is also supported within version 2 of the `webm` specification. Please consider the webm specification as the authoritative on `webm`.

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.

EBMLMaxIDLength Element

name:: EBMLMaxIDLength
path:: \EBML\EBMLMaxIDLength
id:: 0x42F2
minOccurs:: 1
maxOccurs:: 1
range:: 4
default:: 4
type:: uinteger

EBMLMaxSizeLength Element

name:: EBMLMaxSizeLength
path:: \EBML\EBMLMaxSizeLength
id:: 0x42F3
minOccurs:: 1
maxOccurs:: 1
range:: 1-8
default:: 8
type:: uinteger

Segment Element

name:: Segment
path:: \Segment
id:: 0x18538067
minOccurs:: 1
maxOccurs:: 1
type:: master
unknownsizeallowed:: 1
definition:: The Root Element that contains all other Top-Level Elements (Elements defined only at Level 1). A Matroska file is composed of 1 Segment.

SeekHead Element

name:: SeekHead
path:: \Segment\SeekHead
id:: 0x114D9B74
maxOccurs:: 2
type:: master
definition:: Contains the Segment Position of other Top-Level Elements.

Seek Element

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

SeekID Element

name:: SeekID
path:: \Segment\SeekHead\Seek\SeekID
id:: 0x53AB
minOccurs:: 1
maxOccurs:: 1
type:: binary
definition:: The binary ID corresponding to the Element name.

SeekPosition Element

name:: SeekPosition
path:: \Segment\SeekHead\Seek\SeekPosition
id:: 0x53AC
minOccurs:: 1
maxOccurs:: 1
type:: uinteger
definition:: The Segment Position of the Element.

Info Element

name:: Info
path:: \Segment\Info
id:: 0x1549A966
minOccurs:: 1
type:: master
recurring:: 1
definition:: Contains general information about the Segment.

SegmentUID Element

name:: SegmentUID
path:: \Segment\Info\SegmentUID
id:: 0x73A4
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.

SegmentFilename Element

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

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.

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.

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.

NextFilename Element

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

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.

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.

ChapterTranslateEditionUID Element

name:: ChapterTranslateEditionUID
path:: \Segment\Info\ChapterTranslate\ChapterTranslateEditionUID
id:: 0x69FC
type:: uinteger
definition:: Specify an edition UID on which this correspondence applies. When not specified, it means for all editions found in the Segment.

ChapterTranslateCodec Element

name:: ChapterTranslateCodec
path:: \Segment\Info\ChapterTranslate\ChapterTranslateCodec
id:: 0x69BF
minOccurs:: 1
maxOccurs:: 1
type:: uinteger
definition:: The chapter codec; see .

restrictions:

value	label
`0`	Matroska Script
`1`	DVD-menu

ChapterTranslateID Element

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

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).

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.

DateUTC Element

name:: DateUTC
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.

Title Element

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

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.

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.

Cluster Element

name:: Cluster
path:: \Segment\Cluster
id:: 0x1F43B675
type:: master
unknownsizeallowed:: 1
definition:: The Top-Level Element containing the (monolithic) Block structure.

Timestamp Element

name:: Timestamp
path:: \Segment\Cluster\Timestamp
id:: 0xE7
minOccurs:: 1
maxOccurs:: 1
type:: uinteger
definition:: Absolute timestamp of the cluster (based on TimestampScale).

SilentTracks Element

name:: SilentTracks
path:: \Segment\Cluster\SilentTracks
id:: 0x5854
maxOccurs:: 1
type:: master
definition:: The list of tracks that are not used in that part of the stream. It is useful when using overlay tracks on seeking or to decide what track to use.

SilentTrackNumber Element

name:: SilentTrackNumber
path:: \Segment\Cluster\SilentTracks\SilentTrackNumber
id:: 0x58D7
type:: uinteger
definition:: One of the track number that are not used from now on in the stream. It could change later if not specified as silent in a further Cluster.

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.

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.

SimpleBlock Element

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

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.

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 on Block Structure.

BlockVirtual Element

name:: BlockVirtual
path:: \Segment\Cluster\BlockGroup\BlockVirtual
id:: 0xA2
maxOccurs:: 1
type:: binary
minver:: 0
maxver:: 0
definition:: A Block with no data. It MUST be stored in the stream at the place the real Block would be in display order.

BlockAdditions Element

name:: BlockAdditions
path:: \Segment\Cluster\BlockGroup\BlockAdditions
id:: 0x75A1
maxOccurs:: 1
type:: master
definition:: Contain additional blocks to complete the main one. An EBML parser that has no knowledge of the Block structure could still see and use/skip these data.

BlockMore Element

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

BlockAddID Element

name:: BlockAddID
path:: \Segment\Cluster\BlockGroup\BlockAdditions\BlockMore\BlockAddID
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.

BlockAdditional Element

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

BlockDuration Element

name:: BlockDuration
path:: \Segment\Cluster\BlockGroup\BlockDuration
id:: 0x9B

minOccurs: see implementation notes

maxOccurs:: 1

default: see implementation notes

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

implementation notes:

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

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.

ReferenceBlock Element

name:: ReferenceBlock
path:: \Segment\Cluster\BlockGroup\ReferenceBlock
id:: 0xFB
type:: integer
definition:: Timestamp of another frame used as a reference (ie: B or P frame). The timestamp is relative to the block it's attached to.

ReferenceVirtual Element

name:: ReferenceVirtual
path:: \Segment\Cluster\BlockGroup\ReferenceVirtual
id:: 0xFD
maxOccurs:: 1
type:: integer
minver:: 0
maxver:: 0
definition:: The Segment Position of the data that would otherwise be in position of the virtual block.

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.

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.

Slices Element

name:: Slices
path:: \Segment\Cluster\BlockGroup\Slices
id:: 0x8E
maxOccurs:: 1
type:: master
definition:: Contains slices description.

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.

LaceNumber Element

name:: LaceNumber
path:: \Segment\Cluster\BlockGroup\Slices\TimeSlice\LaceNumber
id:: 0xCC
maxOccurs:: 1
default:: 0
type:: uinteger
maxver:: 1
definition:: The reverse number of the frame in the lace (0 is the last frame, 1 is the next to last, etc). Being able to interpret this Element is not REQUIRED for playback.

FrameNumber Element

name:: FrameNumber
path:: \Segment\Cluster\BlockGroup\Slices\TimeSlice\FrameNumber
id:: 0xCD
maxOccurs:: 1
default:: 0
type:: uinteger
minver:: 0
maxver:: 0
definition:: The number of the frame to generate from this lace with this delay (allow you to generate many frames from the same Block/Frame).

BlockAdditionID Element

name:: BlockAdditionID
path:: \Segment\Cluster\BlockGroup\Slices\TimeSlice\BlockAdditionID
id:: 0xCB
maxOccurs:: 1
default:: 0
type:: uinteger
minver:: 0
maxver:: 0
definition:: The ID of the BlockAdditional Element (0 is the main Block).

Delay Element

name:: Delay
path:: \Segment\Cluster\BlockGroup\Slices\TimeSlice\Delay
id:: 0xCE
maxOccurs:: 1
default:: 0
type:: uinteger
minver:: 0
maxver:: 0
definition:: The (scaled) delay to apply to the Element.

SliceDuration Element

name:: SliceDuration
path:: \Segment\Cluster\BlockGroup\Slices\TimeSlice\SliceDuration
id:: 0xCF
maxOccurs:: 1
default:: 0
type:: uinteger
minver:: 0
maxver:: 0
definition:: The (scaled) duration to apply to the Element.

ReferenceFrame Element

name:: ReferenceFrame
path:: \Segment\Cluster\BlockGroup\ReferenceFrame
id:: 0xC8
maxOccurs:: 1
type:: master
minver:: 0
maxver:: 0
definition:: DivX trick track extensions

ReferenceOffset Element

name:: ReferenceOffset
path:: \Segment\Cluster\BlockGroup\ReferenceFrame\ReferenceOffset
id:: 0xC9
minOccurs:: 1
maxOccurs:: 1
type:: uinteger
minver:: 0
maxver:: 0
definition:: DivX trick track extensions

ReferenceTimestamp Element

name:: ReferenceTimestamp
path:: \Segment\Cluster\BlockGroup\ReferenceFrame\ReferenceTimestamp
id:: 0xCA
minOccurs:: 1
maxOccurs:: 1
type:: uinteger
minver:: 0
maxver:: 0
definition:: DivX trick track extensions

EncryptedBlock Element

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

Tracks Element

name:: Tracks
path:: \Segment\Tracks
id:: 0x1654AE6B
type:: master
recurring:: 1
definition:: A Top-Level Element of information with many tracks described.

TrackEntry Element

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

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).

TrackUID Element

name:: TrackUID
path:: \Segment\Tracks\TrackEntry\TrackUID
id:: 0x73C5
minOccurs:: 1
maxOccurs:: 1
range:: not 0
type:: uinteger
definition:: A unique ID to identify the Track. This SHOULD be kept the same when making a direct stream copy of the Track to another file.

TrackType Element

name:: TrackType
path:: \Segment\Tracks\TrackEntry\TrackType
id:: 0x83
minOccurs:: 1
maxOccurs:: 1
range:: 1-254
type:: uinteger
definition:: A set of track types coded on 8 bits.

restrictions:

value	label
`1`	video
`2`	audio
`3`	complex
`16`	logo
`17`	subtitle
`18`	buttons
`32`	control
`33`	metadata

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 if the track is usable. (1 bit)

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 active if no language found matches the user preference. (1 bit)

FlagForced Element

name:: FlagForced
path:: \Segment\Tracks\TrackEntry\FlagForced
id:: 0x55AA
minOccurs:: 1
maxOccurs:: 1
range:: 0-1
default:: 0
type:: uinteger
definition:: Set if that track MUST be active during playback. There can be many forced track for a kind (audio, video or subs), the player SHOULD select the one which language matches the user preference or the default + forced track. Overlay MAY happen between a forced and non-forced track of the same kind. (1 bit)

FlagLacing Element

name:: FlagLacing
path:: \Segment\Tracks\TrackEntry\FlagLacing
id:: 0x9C
minOccurs:: 1
maxOccurs:: 1
range:: 0-1
default:: 1
type:: uinteger
definition:: Set if the track MAY contain blocks using lacing. (1 bit)

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.

MaxCache Element

name:: MaxCache
path:: \Segment\Tracks\TrackEntry\MaxCache
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.

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).

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 for more information

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).

TrackOffset Element

name:: TrackOffset
path:: \Segment\Tracks\TrackEntry\TrackOffset
id:: 0x537F
maxOccurs:: 1
default:: 0
type:: integer
minver:: 0
maxver:: 0
definition:: A value to add to the Block's Timestamp. This can be used to adjust the playback offset of a track.

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 (). A value 0 means there is no BlockAdditions () for this track.

BlockAdditionMapping Element

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

BlockAddIDValue Element

name:: BlockAddIDValue
path:: \Segment\Tracks\TrackEntry\BlockAdditionMapping\BlockAddIDValue
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 (), value being described. To keep MaxBlockAdditionID as low as possible, small values SHOULD be used.

BlockAddIDName Element

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

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 identifer of the Block Additional Mapping to define how the BlockAdditional data should be handled.

BlockAddIDExtraData Element

name:: BlockAddIDExtraData
path:: \Segment\Tracks\TrackEntry\BlockAdditionMapping\BlockAddIDExtraData
id:: 0x41ED
maxOccurs:: 1
type:: binary
minver:: 4
definition:: Extra binary data that the BlockAddIDType can use to interpret the BlockAdditional data. The intepretation of the binary data depends on the BlockAddIDType value and the corresponding Block Additional Mapping.

Name Element

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

Language Element

name:: Language
path:: \Segment\Tracks\TrackEntry\Language
id:: 0x22B59C
maxOccurs:: 1
default:: eng
type:: string
definition:: Specifies the language of the track in the Matroska languages form; see on language codes. This Element MUST be ignored if the LanguageIETF Element is used in the same TrackEntry.

LanguageIETF Element

name:: LanguageIETF
path:: \Segment\Tracks\TrackEntry\LanguageIETF
id:: 0x22B59D
maxOccurs:: 1
type:: string
minver:: 4
definition:: Specifies the language of the track according to BCP 47 and using the IANA Language Subtag Registry. If this Element is used, then any Language Elements used in the same TrackEntry MUST be ignored.

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 for more info.

CodecPrivate Element

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

CodecName Element

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

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.

CodecSettings Element

name:: CodecSettings
path:: \Segment\Tracks\TrackEntry\CodecSettings
id:: 0x3A9697
maxOccurs:: 1
type:: utf-8
minver:: 0
maxver:: 0
definition:: A string describing the encoding setting used.

CodecInfoURL Element

name:: CodecInfoURL
path:: \Segment\Tracks\TrackEntry\CodecInfoURL
id:: 0x3B4040
type:: string
minver:: 0
maxver:: 0
definition:: A URL to find information about the codec used.

CodecDownloadURL Element

name:: CodecDownloadURL
path:: \Segment\Tracks\TrackEntry\CodecDownloadURL
id:: 0x26B240
type:: string
minver:: 0
maxver:: 0
definition:: A URL to download about the codec used.

CodecDecodeAll Element

name:: CodecDecodeAll
path:: \Segment\Tracks\TrackEntry\CodecDecodeAll
id:: 0xAA
minOccurs:: 1
maxOccurs:: 1
range:: 0-1
default:: 1
type:: uinteger
minver:: 2
definition:: The codec can decode potentially damaged data (1 bit).

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 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.

CodecDelay Element

name:: CodecDelay
path:: \Segment\Tracks\TrackEntry\CodecDelay
id:: 0x56AA
maxOccurs:: 1
default:: 0
type:: uinteger
minver:: 4
definition:: CodecDelay is The codec-built-in delay in nanoseconds. This value MUST be subtracted from each block timestamp in order to get the actual timestamp. The value SHOULD be small so the muxing of tracks with the same actual timestamp are in the same Cluster.

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.

TrackTranslate Element

name:: TrackTranslate
path:: \Segment\Tracks\TrackEntry\TrackTranslate
id:: 0x6624
type:: master
definition:: The track identification for the given Chapter Codec.

TrackTranslateEditionUID Element

name:: TrackTranslateEditionUID
path:: \Segment\Tracks\TrackEntry\TrackTranslate\TrackTranslateEditionUID
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.

TrackTranslateCodec Element

name:: TrackTranslateCodec
path:: \Segment\Tracks\TrackEntry\TrackTranslate\TrackTranslateCodec
id:: 0x66BF
minOccurs:: 1
maxOccurs:: 1
type:: uinteger
definition:: The chapter codec; see .

restrictions:

value	label
`0`	Matroska Script
`1`	DVD-menu

TrackTranslateTrackID Element

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

Video Element

name:: Video
path:: \Segment\Tracks\TrackEntry\Video
id:: 0xE0
maxOccurs:: 1
type:: master
definition:: Video settings.

FlagInterlaced Element

name:: FlagInterlaced
path:: \Segment\Tracks\TrackEntry\Video\FlagInterlaced
id:: 0x9A
minOccurs:: 1
maxOccurs:: 1
range:: 0-2
default:: 0
type:: uinteger
minver:: 2
definition:: A flag to declare if the video is known to be progressive, or interlaced, and if applicable to declare details about the interlacement.

restrictions:

value	label
`0`	undetermined
`1`	interlaced
`2`	progressive

FieldOrder Element

name:: FieldOrder
path:: \Segment\Tracks\TrackEntry\Video\FieldOrder
id:: 0x9D
minOccurs:: 1
maxOccurs:: 1
range:: 0-14
default:: 2
type:: uinteger
minver:: 4
definition:: Declare the field ordering of the video. If FlagInterlaced is not set to 1, this Element MUST be ignored.

restrictions:

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

StereoMode Element

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

restrictions:

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

AlphaMode Element

name:: AlphaMode
path:: \Segment\Tracks\TrackEntry\Video\AlphaMode
id:: 0x53C0
maxOccurs:: 1
default:: 0
type:: uinteger
minver:: 3
definition:: Alpha Video Mode. Presence of this Element indicates that the BlockAdditional Element could contain Alpha data.

OldStereoMode Element

name:: OldStereoMode
path:: \Segment\Tracks\TrackEntry\Video\OldStereoMode
id:: 0x53B9
maxOccurs:: 1
type:: uinteger
maxver:: 0
definition:: DEPRECATED, DO NOT USE. Bogus StereoMode value used in old versions of libmatroska.

restrictions:

value	label
`0`	mono
`1`	right eye
`2`	left eye
`3`	both eyes

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.

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.

PixelCropBottom Element

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

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.

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.

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.

DisplayWidth Element

name:: DisplayWidth
path:: \Segment\Tracks\TrackEntry\Video\DisplayWidth
id:: 0x54B0
maxOccurs:: 1
range:: not 0

default: see implementation notes

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

implementation notes:

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

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).

implementation notes:

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

DisplayUnit Element

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

restrictions:

value	label
`0`	pixels
`1`	centimeters
`2`	inches
`3`	display aspect ratio
`4`	unknown

AspectRatioType Element

name:: AspectRatioType
path:: \Segment\Tracks\TrackEntry\Video\AspectRatioType
id:: 0x54B3
maxOccurs:: 1
default:: 0
type:: uinteger
definition:: Specify the possible modifications to the aspect ratio.

restrictions:

value	label
`0`	free resizing
`1`	keep aspect ratio
`2`	fixed

ColourSpace Element

name:: ColourSpace
path:: \Segment\Tracks\TrackEntry\Video\ColourSpace
id:: 0x2EB524

minOccurs: see implementation notes

maxOccurs:: 1
type:: binary
definition:: Specify the pixel format used for the Track's data as a FourCC. This value is similar in scope to the biCompression value of AVI's BITMAPINFOHEADER.

implementation notes:

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

GammaValue Element

name:: GammaValue
path:: \Segment\Tracks\TrackEntry\Video\GammaValue
id:: 0x2FB523
maxOccurs:: 1
range:: > 0x0p+0
type:: float
minver:: 0
maxver:: 0
definition:: Gamma Value.

FrameRate Element

name:: FrameRate
path:: \Segment\Tracks\TrackEntry\Video\FrameRate
id:: 0x2383E3
maxOccurs:: 1
range:: > 0x0p+0
type:: float
minver:: 0
maxver:: 0
definition:: Number of frames per second. Informational only.

Colour Element

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

MatrixCoefficients Element

name:: MatrixCoefficients
path:: \Segment\Tracks\TrackEntry\Video\Colour\MatrixCoefficients
id:: 0x55B1
maxOccurs:: 1
default:: 2
type:: uinteger
minver:: 4
definition:: The Matrix Coefficients of the video used to derive luma and chroma values from red, green, and blue color primaries. For clarity, the value and meanings for MatrixCoefficients are adopted from Table 4 of ISO/IEC 23001-8:2016 or ITU-T H.273.

restrictions:

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

BitsPerChannel Element

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

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.

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.

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.

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.

ChromaSitingHorz Element

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

restrictions:

value	label
`0`	unspecified
`1`	left collocated
`2`	half

ChromaSitingVert Element

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

restrictions:

value	label
`0`	unspecified
`1`	top collocated
`2`	half

Range Element

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

restrictions:

value	label
`0`	unspecified
`1`	broadcast range
`2`	full range (no clipping)
`3`	defined by MatrixCoefficients / TransferCharacteristics

TransferCharacteristics Element

name:: TransferCharacteristics
path:: \Segment\Tracks\TrackEntry\Video\Colour\TransferCharacteristics
id:: 0x55BA
maxOccurs:: 1
default:: 2
type:: uinteger
minver:: 4
definition:: The transfer characteristics of the video. For clarity, the value and meanings for TransferCharacteristics are adopted from Table 3 of ISO/IEC 23091-4 or ITU-T H.273.

restrictions:

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)

Primaries Element

name:: Primaries
path:: \Segment\Tracks\TrackEntry\Video\Colour\Primaries
id:: 0x55BB
maxOccurs:: 1
default:: 2
type:: uinteger
minver:: 4
definition:: The colour primaries of the video. For clarity, the value and meanings for Primaries are adopted from Table 2 of ISO/IEC 23091-4 or ITU-T H.273.

restrictions:

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

MaxCLL Element

name:: MaxCLL
path:: \Segment\Tracks\TrackEntry\Video\Colour\MaxCLL
id:: 0x55BC
maxOccurs:: 1
type:: uinteger
minver:: 4
definition:: Maximum brightness of a single pixel (Maximum Content Light Level) in candelas per square meter (cd/m²).

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/m²).

MasteringMetadata Element

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

PrimaryRChromaticityX Element

name:: PrimaryRChromaticityX
path:: \Segment\Tracks\TrackEntry\Video\Colour\MasteringMetadata\PrimaryRChromaticityX
id:: 0x55D1
maxOccurs:: 1
range:: 0-1
type:: float
minver:: 4
definition:: Red X chromaticity coordinate, as defined by CIE 1931.

PrimaryRChromaticityY Element

name:: PrimaryRChromaticityY
path:: \Segment\Tracks\TrackEntry\Video\Colour\MasteringMetadata\PrimaryRChromaticityY
id:: 0x55D2
maxOccurs:: 1
range:: 0-1
type:: float
minver:: 4
definition:: Red Y chromaticity coordinate, as defined by CIE 1931.

PrimaryGChromaticityX Element

name:: PrimaryGChromaticityX
path:: \Segment\Tracks\TrackEntry\Video\Colour\MasteringMetadata\PrimaryGChromaticityX
id:: 0x55D3
maxOccurs:: 1
range:: 0-1
type:: float
minver:: 4
definition:: Green X chromaticity coordinate, as defined by CIE 1931.

PrimaryGChromaticityY Element

name:: PrimaryGChromaticityY
path:: \Segment\Tracks\TrackEntry\Video\Colour\MasteringMetadata\PrimaryGChromaticityY
id:: 0x55D4
maxOccurs:: 1
range:: 0-1
type:: float
minver:: 4
definition:: Green Y chromaticity coordinate, as defined by CIE 1931.

PrimaryBChromaticityX Element

name:: PrimaryBChromaticityX
path:: \Segment\Tracks\TrackEntry\Video\Colour\MasteringMetadata\PrimaryBChromaticityX
id:: 0x55D5
maxOccurs:: 1
range:: 0-1
type:: float
minver:: 4
definition:: Blue X chromaticity coordinate, as defined by CIE 1931.

PrimaryBChromaticityY Element

name:: PrimaryBChromaticityY
path:: \Segment\Tracks\TrackEntry\Video\Colour\MasteringMetadata\PrimaryBChromaticityY
id:: 0x55D6
maxOccurs:: 1
range:: 0-1
type:: float
minver:: 4
definition:: Blue Y chromaticity coordinate, as defined by CIE 1931.

WhitePointChromaticityX Element

name:: WhitePointChromaticityX
path:: \Segment\Tracks\TrackEntry\Video\Colour\MasteringMetadata\WhitePointChromaticityX
id:: 0x55D7
maxOccurs:: 1
range:: 0-1
type:: float
minver:: 4
definition:: White X chromaticity coordinate, as defined by CIE 1931.

WhitePointChromaticityY Element

name:: WhitePointChromaticityY
path:: \Segment\Tracks\TrackEntry\Video\Colour\MasteringMetadata\WhitePointChromaticityY
id:: 0x55D8
maxOccurs:: 1
range:: 0-1
type:: float
minver:: 4
definition:: White Y chromaticity coordinate, as defined by CIE 1931.

LuminanceMax Element

name:: LuminanceMax
path:: \Segment\Tracks\TrackEntry\Video\Colour\MasteringMetadata\LuminanceMax
id:: 0x55D9
maxOccurs:: 1
range:: >= 0x0p+0
type:: float
minver:: 4
definition:: Maximum luminance. Represented in candelas per square meter (cd/m²).

LuminanceMin Element

name:: LuminanceMin
path:: \Segment\Tracks\TrackEntry\Video\Colour\MasteringMetadata\LuminanceMin
id:: 0x55DA
maxOccurs:: 1
range:: >= 0x0p+0
type:: float
minver:: 4
definition:: Minimum luminance. Represented in candelas per square meter (cd/m²).

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 spherical and VR videos.

ProjectionType Element

name:: ProjectionType
path:: \Segment\Tracks\TrackEntry\Video\Projection\ProjectionType
id:: 0x7671
minOccurs:: 1
maxOccurs:: 1
range:: 0-3
default:: 0
type:: uinteger
minver:: 4
definition:: Describes the projection used for this video track.

restrictions:

value	label
`0`	rectangular
`1`	equirectangular
`2`	cubemap
`3`	mesh

ProjectionPrivate Element

name:: ProjectionPrivate
path:: \Segment\Tracks\TrackEntry\Video\Projection\ProjectionPrivate
id:: 0x7672
maxOccurs:: 1
type:: binary
minver:: 4
definition:: Private data that only applies to a specific projection.

If ProjectionType equals 0 (Rectangular), then this element must not be present.
If ProjectionType equals 1 (Equirectangular), then this element must be present and contain the same binary data that would be stored inside an ISOBMFF Equirectangular Projection Box ('equi').
If ProjectionType equals 2 (Cubemap), then this element must be present and contain the same binary data that would be stored inside an ISOBMFF Cubemap Projection Box ('cbmp').
If ProjectionType equals 3 (Mesh), then this element must be present and contain the same binary data that would be stored inside an ISOBMFF Mesh Projection Box ('mshp').

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

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.

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.

ProjectionPosePitch Element

name:: ProjectionPosePitch
path:: \Segment\Tracks\TrackEntry\Video\Projection\ProjectionPosePitch
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.

ProjectionPoseRoll Element

name:: ProjectionPoseRoll
path:: \Segment\Tracks\TrackEntry\Video\Projection\ProjectionPoseRoll
id:: 0x7675
minOccurs:: 1
maxOccurs:: 1
default:: 0x0p+0
type:: float
minver:: 4
definition:: Specifies a roll rotation to the projection.

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

Audio Element

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

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.

OutputSamplingFrequency Element

name:: OutputSamplingFrequency
path:: \Segment\Tracks\TrackEntry\Audio\OutputSamplingFrequency
id:: 0x78B5
maxOccurs:: 1
range:: > 0x0p+0

default: see implementation notes

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

implementation notes:

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

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.

ChannelPositions Element

name:: ChannelPositions
path:: \Segment\Tracks\TrackEntry\Audio\ChannelPositions
id:: 0x7D7B
maxOccurs:: 1
type:: binary
minver:: 0
maxver:: 0
definition:: Table of horizontal angles for each successive channel.

BitDepth Element

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

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 .

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

TrackPlane Element

name:: TrackPlane
path:: \Segment\Tracks\TrackEntry\TrackOperation\TrackCombinePlanes\TrackPlane
id:: 0xE4
minOccurs:: 1
type:: master
minver:: 3
definition:: Contains a video plane track that need to be combined to create this 3D track

TrackPlaneUID Element

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

TrackPlaneType Element

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

restrictions:

value	label
`0`	left eye
`1`	right eye
`2`	background

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

TrackJoinUID Element

name:: TrackJoinUID
path:: \Segment\Tracks\TrackEntry\TrackOperation\TrackJoinBlocks\TrackJoinUID
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.

TrickTrackUID Element

name:: TrickTrackUID
path:: \Segment\Tracks\TrackEntry\TrickTrackUID
id:: 0xC0
maxOccurs:: 1
type:: uinteger
minver:: 0
maxver:: 0
definition:: DivX trick track extensions

TrickTrackSegmentUID Element

name:: TrickTrackSegmentUID
path:: \Segment\Tracks\TrackEntry\TrickTrackSegmentUID
id:: 0xC1
maxOccurs:: 1
type:: binary
minver:: 0
maxver:: 0
definition:: DivX trick track extensions

TrickTrackFlag Element

name:: TrickTrackFlag
path:: \Segment\Tracks\TrackEntry\TrickTrackFlag
id:: 0xC6
maxOccurs:: 1
default:: 0
type:: uinteger
minver:: 0
maxver:: 0
definition:: DivX trick track extensions

TrickMasterTrackUID Element

name:: TrickMasterTrackUID
path:: \Segment\Tracks\TrackEntry\TrickMasterTrackUID
id:: 0xC7
maxOccurs:: 1
type:: uinteger
minver:: 0
maxver:: 0
definition:: DivX trick track extensions

TrickMasterTrackSegmentUID Element

name:: TrickMasterTrackSegmentUID
path:: \Segment\Tracks\TrackEntry\TrickMasterTrackSegmentUID
id:: 0xC4
maxOccurs:: 1
type:: binary
minver:: 0
maxver:: 0
definition:: DivX trick track extensions

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.

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.

ContentEncodingOrder Element

name:: ContentEncodingOrder
path:: \Segment\Tracks\TrackEntry\ContentEncodings\ContentEncoding\ContentEncodingOrder
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.

ContentEncodingScope Element

name:: ContentEncodingScope
path:: \Segment\Tracks\TrackEntry\ContentEncodings\ContentEncoding\ContentEncodingScope
id:: 0x5032
minOccurs:: 1
maxOccurs:: 1
range:: not 0
default:: 1
type:: uinteger
definition:: A bit field that describes which Elements have been modified in this way. Values (big-endian) can be OR'ed.

restrictions:

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

ContentEncodingType Element

name:: ContentEncodingType
path:: \Segment\Tracks\TrackEntry\ContentEncodings\ContentEncoding\ContentEncodingType
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

ContentCompression Element

name:: ContentCompression
path:: \Segment\Tracks\TrackEntry\ContentEncodings\ContentEncoding\ContentCompression
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.

ContentCompAlgo Element

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

restrictions:

value	label
`0`	zlib
`1`	bzlib
`2`	lzo1x
`3`	Header Stripping

ContentCompSettings Element

name:: ContentCompSettings
path:: \Segment\Tracks\TrackEntry\ContentEncodings\ContentEncoding\ContentCompression\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.

ContentEncryption Element

name:: ContentEncryption
path:: \Segment\Tracks\TrackEntry\ContentEncodings\ContentEncoding\ContentEncryption
id:: 0x5035
maxOccurs:: 1
type:: master
definition:: Settings describing the encryption used. This Element MUST be present if the value of ContentEncodingType is 1 (encryption) and MUST be ignored otherwise.

ContentEncAlgo Element

name:: ContentEncAlgo
path:: \Segment\Tracks\TrackEntry\ContentEncodings\ContentEncoding\ContentEncryption\ContentEncAlgo
id:: 0x47E1
minOccurs:: 1
maxOccurs:: 1
default:: 0
type:: uinteger
definition:: The encryption algorithm used. The value "0" means that the contents have not been encrypted but only signed.

restrictions:

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

ContentEncKeyID Element

name:: ContentEncKeyID
path:: \Segment\Tracks\TrackEntry\ContentEncodings\ContentEncoding\ContentEncryption\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.

ContentEncAESSettings Element

name:: ContentEncAESSettings
path:: \Segment\Tracks\TrackEntry\ContentEncodings\ContentEncoding\ContentEncryption\ContentEncAESSettings
id:: 0x47E7
maxOccurs:: 1
type:: master
minver:: 4
definition:: Settings describing the encryption algorithm used. If ContentEncAlgo != 5 this MUST be ignored.

AESSettingsCipherMode Element

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

restrictions:

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

ContentSignature Element

name:: ContentSignature
path:: \Segment\Tracks\TrackEntry\ContentEncodings\ContentEncoding\ContentEncryption\ContentSignature
id:: 0x47E3
maxOccurs:: 1
type:: binary
definition:: A cryptographic signature of the contents.

ContentSigKeyID Element

name:: ContentSigKeyID
path:: \Segment\Tracks\TrackEntry\ContentEncodings\ContentEncoding\ContentEncryption\ContentSigKeyID
id:: 0x47E4
maxOccurs:: 1
type:: binary
definition:: This is the ID of the private key the data was signed with.

ContentSigAlgo Element

name:: ContentSigAlgo
path:: \Segment\Tracks\TrackEntry\ContentEncodings\ContentEncoding\ContentEncryption\ContentSigAlgo
id:: 0x47E5
maxOccurs:: 1
default:: 0
type:: uinteger
definition:: The algorithm used for the signature.

restrictions:

value	label
`0`	Not signed
`1`	RSA

ContentSigHashAlgo Element

name:: ContentSigHashAlgo
path:: \Segment\Tracks\TrackEntry\ContentEncodings\ContentEncoding\ContentEncryption\ContentSigHashAlgo
id:: 0x47E6
maxOccurs:: 1
default:: 0
type:: uinteger
definition:: The hash algorithm used for the signature.

restrictions:

value	label
`0`	Not signed
`1`	SHA1-160
`2`	MD5

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.

implementation notes:

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

CuePoint Element

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

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.

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.

CueTrack Element

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

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.

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.

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.

CueBlockNumber Element

name:: CueBlockNumber
path:: \Segment\Cues\CuePoint\CueTrackPositions\CueBlockNumber
id:: 0x5378
maxOccurs:: 1
range:: not 0
default:: 1
type:: uinteger
definition:: Number of the Block in the specified Cluster.

CueCodecState Element

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

CueReference Element

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

CueRefTime Element

name:: CueRefTime
path:: \Segment\Cues\CuePoint\CueTrackPositions\CueReference\CueRefTime
id:: 0x96
minOccurs:: 1
maxOccurs:: 1
type:: uinteger
minver:: 2
definition:: Timestamp of the referenced Block.

CueRefCluster Element

name:: CueRefCluster
path:: \Segment\Cues\CuePoint\CueTrackPositions\CueReference\CueRefCluster
id:: 0x97
minOccurs:: 1
maxOccurs:: 1
type:: uinteger
minver:: 0
maxver:: 0
definition:: The Segment Position of the Cluster containing the referenced Block.

CueRefNumber Element

name:: CueRefNumber
path:: \Segment\Cues\CuePoint\CueTrackPositions\CueReference\CueRefNumber
id:: 0x535F
maxOccurs:: 1
range:: not 0
default:: 1
type:: uinteger
minver:: 0
maxver:: 0
definition:: Number of the referenced Block of Track X in the specified Cluster.

CueRefCodecState Element

name:: CueRefCodecState
path:: \Segment\Cues\CuePoint\CueTrackPositions\CueReference\CueRefCodecState
id:: 0xEB
maxOccurs:: 1
default:: 0
type:: uinteger
minver:: 0
maxver:: 0
definition:: The Segment Position of the Codec State corresponding to this referenced Element. 0 means that the data is taken from the initial Track Entry.

Attachments Element

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

AttachedFile Element

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

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.

FileName Element

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

FileMimeType Element

name:: FileMimeType
path:: \Segment\Attachments\AttachedFile\FileMimeType
id:: 0x4660
minOccurs:: 1
maxOccurs:: 1
type:: string
definition:: MIME type of the file.

FileData Element

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

FileUID Element

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

FileReferral Element

name:: FileReferral
path:: \Segment\Attachments\AttachedFile\FileReferral
id:: 0x4675
maxOccurs:: 1
type:: binary
minver:: 0
maxver:: 0
definition:: A binary value that a track/codec can refer to when the attachment is needed.

FileUsedStartTime Element

name:: FileUsedStartTime
path:: \Segment\Attachments\AttachedFile\FileUsedStartTime
id:: 0x4661
maxOccurs:: 1
type:: uinteger
minver:: 0
maxver:: 0
definition:: DivX font extension

FileUsedEndTime Element

name:: FileUsedEndTime
path:: \Segment\Attachments\AttachedFile\FileUsedEndTime
id:: 0x4662
maxOccurs:: 1
type:: uinteger
minver:: 0
maxver:: 0
definition:: DivX font extension

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 .

EditionEntry Element

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

EditionUID Element

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

EditionFlagHidden Element

name:: EditionFlagHidden
path:: \Segment\Chapters\EditionEntry\EditionFlagHidden
id:: 0x45BD
minOccurs:: 1
maxOccurs:: 1
range:: 0-1
default:: 0
type:: uinteger
definition:: If an edition is hidden (1), it SHOULD NOT be available to the user interface (but still to Control Tracks; see on Chapter flags). (1 bit)

EditionFlagDefault Element

name:: EditionFlagDefault
path:: \Segment\Chapters\EditionEntry\EditionFlagDefault
id:: 0x45DB
minOccurs:: 1
maxOccurs:: 1
range:: 0-1
default:: 0
type:: uinteger
definition:: If a flag is set (1) the edition SHOULD be used as the default one. (1 bit)

EditionFlagOrdered Element

name:: EditionFlagOrdered
path:: \Segment\Chapters\EditionEntry\EditionFlagOrdered
id:: 0x45DD
maxOccurs:: 1
range:: 0-1
default:: 0
type:: uinteger
definition:: Specify if the chapters can be defined multiple times and the order to play them is enforced. (1 bit)

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).

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.

ChapterStringUID Element

name:: ChapterStringUID
path:: \Segment\Chapters\EditionEntry\+ChapterAtom\ChapterStringUID
id:: 0x5654
maxOccurs:: 1
type:: utf-8
minver:: 3
definition:: A unique string ID to identify the Chapter. Use for WebVTT cue identifier storage.

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).

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).

ChapterFlagHidden Element

name:: ChapterFlagHidden
path:: \Segment\Chapters\EditionEntry\+ChapterAtom\ChapterFlagHidden
id:: 0x98
minOccurs:: 1
maxOccurs:: 1
range:: 0-1
default:: 0
type:: uinteger
definition:: If a chapter is hidden (1), it SHOULD NOT be available to the user interface (but still to Control Tracks; see on Chapter flags). (1 bit)

ChapterFlagEnabled Element

name:: ChapterFlagEnabled
path:: \Segment\Chapters\EditionEntry\+ChapterAtom\ChapterFlagEnabled
id:: 0x4598
minOccurs:: 1
maxOccurs:: 1
range:: 0-1
default:: 1
type:: uinteger
definition:: Specify whether the chapter is enabled. It can be enabled/disabled by a Control Track. When disabled, the movie SHOULD skip all the content between the TimeStart and TimeEnd of this chapter; see on Chapter flags. (1 bit)

ChapterSegmentUID Element

name:: ChapterSegmentUID
path:: \Segment\Chapters\EditionEntry\+ChapterAtom\ChapterSegmentUID
id:: 0x6E67

minOccurs: see implementation notes

maxOccurs:: 1
range:: >0
type:: binary
definition:: The SegmentUID of another Segment to play during this chapter.

implementation notes:

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

ChapterSegmentEditionUID Element

name:: ChapterSegmentEditionUID
path:: \Segment\Chapters\EditionEntry\+ChapterAtom\ChapterSegmentEditionUID
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.

ChapterPhysicalEquiv Element

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

ChapterTrack Element

name:: ChapterTrack
path:: \Segment\Chapters\EditionEntry\+ChapterAtom\ChapterTrack
id:: 0x8F
maxOccurs:: 1
type:: master
definition:: List of tracks on which the chapter applies. If this Element is not present, all tracks apply

ChapterTrackUID Element

name:: ChapterTrackUID
path:: \Segment\Chapters\EditionEntry\+ChapterAtom\ChapterTrack\ChapterTrackUID
id:: 0x89
minOccurs:: 1
range:: not 0
type:: uinteger
definition:: UID of the Track to apply this chapter to. In the absence of a control track, choosing this chapter will select the listed Tracks and deselect unlisted tracks. Absence of this Element indicates that the Chapter SHOULD be applied to any currently used Tracks.

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.

ChapString Element

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

ChapLanguage Element

name:: ChapLanguage
path:: \Segment\Chapters\EditionEntry\+ChapterAtom\ChapterDisplay\ChapLanguage
id:: 0x437C
minOccurs:: 1
default:: eng
type:: string
definition:: The languages corresponding to the string, in the bibliographic ISO-639-2 form. This Element MUST be ignored if the ChapLanguageIETF Element is used within the same ChapterDisplay Element.

ChapLanguageIETF Element

name:: ChapLanguageIETF
path:: \Segment\Chapters\EditionEntry\+ChapterAtom\ChapterDisplay\ChapLanguageIETF
id:: 0x437D
type:: string
minver:: 4
definition:: Specifies the language used in the ChapString according to BCP 47 and using the IANA Language Subtag Registry. If this Element is used, then any ChapLanguage Elements used in the same ChapterDisplay MUST be ignored.

ChapCountry Element

name:: ChapCountry
path:: \Segment\Chapters\EditionEntry\+ChapterAtom\ChapterDisplay\ChapCountry
id:: 0x437E
type:: string
definition:: The countries corresponding to the string, same 2 octets as in Internet domains. This Element MUST be ignored if the ChapLanguageIETF Element is used within the same ChapterDisplay Element.

ChapProcess Element

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

ChapProcessCodecID Element

name:: ChapProcessCodecID
path:: \Segment\Chapters\EditionEntry\+ChapterAtom\ChapProcess\ChapProcessCodecID
id:: 0x6955
minOccurs:: 1
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 on DVD menus. More codec IDs can be added later.

ChapProcessPrivate Element

name:: ChapProcessPrivate
path:: \Segment\Chapters\EditionEntry\+ChapterAtom\ChapProcess\ChapProcessPrivate
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 on DVD menus.

ChapProcessCommand Element

name:: ChapProcessCommand
path:: \Segment\Chapters\EditionEntry\+ChapterAtom\ChapProcess\ChapProcessCommand
id:: 0x6911
type:: master
definition:: Contains all the commands associated to the Atom.

ChapProcessTime Element

name:: ChapProcessTime
path:: \Segment\Chapters\EditionEntry\+ChapterAtom\ChapProcess\ChapProcessCommand\ChapProcessTime
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

ChapProcessData Element

name:: ChapProcessData
path:: \Segment\Chapters\EditionEntry\+ChapterAtom\ChapProcess\ChapProcessCommand\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 on DVD menus.

Tags Element

name:: Tags
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 .

Tag Element

name:: Tag
path:: \Segment\Tags\Tag
id:: 0x7373
minOccurs:: 1
type:: master
definition:: A single metadata descriptor.

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.

TargetTypeValue Element

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

restrictions:

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

TargetType Element

name:: TargetType
path:: \Segment\Tags\Tag\Targets\TargetType
id:: 0x63CA
maxOccurs:: 1
type:: string
definition:: An informational string that can be used to display the logical level of the target like "ALBUM", "TRACK", "MOVIE", "CHAPTER", etc ; see Section 6.4 of .

restrictions:

value	label
`COLLECTION`	COLLECTION
`EDITION`	EDITION
`ISSUE`	ISSUE
`VOLUME`	VOLUME
`OPUS`	OPUS
`SEASON`	SEASON
`SEQUEL`	SEQUEL
`ALBUM`	ALBUM
`OPERA`	OPERA
`CONCERT`	CONCERT
`MOVIE`	MOVIE
`EPISODE`	EPISODE
`PART`	PART
`SESSION`	SESSION
`TRACK`	TRACK
`SONG`	SONG
`CHAPTER`	CHAPTER
`SUBTRACK`	SUBTRACK
`PART`	PART
`MOVEMENT`	MOVEMENT
`SCENE`	SCENE
`SHOT`	SHOT

TagTrackUID Element

name:: TagTrackUID
path:: \Segment\Tags\Tag\Targets\TagTrackUID
id:: 0x63C5
default:: 0
type:: uinteger
definition:: A unique ID to identify the Track(s) the tags belong to. If the value is 0 at this level, the tags apply to all tracks in the Segment.

TagEditionUID Element

name:: TagEditionUID
path:: \Segment\Tags\Tag\Targets\TagEditionUID
id:: 0x63C9
default:: 0
type:: uinteger
definition:: A unique ID to identify the EditionEntry(s) the tags belong to. If the value is 0 at this level, the tags apply to all editions in the Segment.

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. If the value is 0 at this level, the tags apply to all chapters in the Segment.

TagAttachmentUID Element

name:: TagAttachmentUID
path:: \Segment\Tags\Tag\Targets\TagAttachmentUID
id:: 0x63C6
default:: 0
type:: uinteger
definition:: A unique ID to identify the Attachment(s) the tags belong to. If the value is 0 at this level, the tags apply to all the attachments in the Segment.

SimpleTag Element

name:: SimpleTag
path:: \Segment\Tags\Tag\+SimpleTag
id:: 0x67C8
minOccurs:: 1
type:: master
recursive:: 1
definition:: Contains general information about the target.

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.

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

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 BCP 47 and using the IANA Language Subtag Registry. If this Element is used, then any TagLanguage Elements used in the same SimpleTag MUST be ignored.

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.

TagString Element

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

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.

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.

Top-Level Elements The Info Element is the only REQUIRED Top-Level Element in a Matroska file. To be playable, Matroska MUST also contain at least one Tracks Element and Cluster Element. The first Info Element and the first Tracks Element MUST either be stored before the first Cluster Element or both SHALL be referenced by a SeekHead Element occurring before the first Cluster Element. It is possible to edit a Matroska file after it has been created. For example, chapters, tags, or attachments can be added. When new Top-Level Elements are added to a Matroska file, the SeekHead Element(s) MUST be updated so that the SeekHead Element(s) itemize the identity and position of all Top-Level Elements. Editing, removing, or adding Elements to a Matroska file often requires that some existing Elements be voided or extended; therefore, it is RECOMMENDED to use Void Elements as padding in between Top-Level Elements.

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.

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.

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.

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

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.

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.

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.

Optimum layout from a muxer

SeekHead
Info
Tracks
Chapters
Attachments
Tags
Clusters
Cues

Optimum layout after editing tags

SeekHead
Info
Tracks
Chapters
Attachments
Void
Clusters
Cues
Tags

Optimum layout with Cues at the front

SeekHead
Info
Tracks
Chapters
Attachments
Tags
Cues
Clusters

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

Chapters

Edition and Chapter Flags

Chapter Flags Two Chapter Flags are defined to describe the behavior of the ChapterAtom Element: ChapterFlagHidden and ChapterFlagEnabled. If a ChapterAtom Element is the Child Element of another ChapterAtom Element with a Chapter Flag set to true, then the Child ChapterAtom Element MUST be interpreted as having its same Chapter Flag set to true. If a ChapterAtom Element is the Child Element of another ChapterAtom Element with a Chapter Flag set to false, or if the ChapterAtom Element does not have a ChapterAtom Element as its Parent Element, then it MUST be interpreted according to its own Chapter Flag. As an example, consider a Parent ChapterAtom Element that has its ChapterFlagHidden set to true and also contains two child ChapterAtoms, the first with ChapterFlagHidden set to true and the second with ChapterFlagHidden either set to false or not present at all (in which case the default value of the Element applies, which is false). Since the parent ChapterAtom has its ChapterFlagHidden set to true, all of its children ChapterAtoms MUST also be interpreted as if their ChapterFlagHidden is also set to true. However, if a Control Track toggles the parent's ChapterFlagHidden flag to false, then only the parent ChapterAtom and its second child ChapterAtom MUST be interpreted as if ChapterFlagHidden is set to false. The first child ChapterAtom, which has the ChapterFlagHidden flag set to true, retains its value until its value is toggled to false by a Control Track.

Edition Flags Three Edition Flags are defined to describe the behavior of the EditionEntry Element: EditionFlagHidden, EditionFlagDefault, and EditionFlagOrdered.

EditionFlagHidden The EditionFlagHidden Flag behaves similarly to the ChapterFlagHidden Flag: if EditionFlagHidden is set to true, its Child ChapterAtoms Elements MUST also be interpreted as if their ChapterFlagHidden is also set to true, regardless of their own ChapterFlagHidden Flags. If EditionFlagHidden is toggled by a Control Track to false, the ChapterFlagHidden Flags of the Child ChapterAtoms Elements SHALL determine whether the ChapterAtom is hidden or not.

EditionFlagDefault It is RECOMMENDED that no more than one Edition have an EditionFlagDefault Flag set to true. The first Edition with both the EditionFlagDefault Flag set to true and the EditionFlagHidden Flag set to false is the Default Edition. When all EditionFlagDefault Flags are set to false, then the first Edition with the EditionFlagHidden Flag set to false is the Default Edition. The Default Edition is the edition that should be used for playback by default.

EditionFlagOrdered The EditionFlagOrdered Flag is a significant feature as it enables an Edition of Ordered Chapters which defines and arranges a virtual timeline rather than simply labeling points within the timeline. For example, with Editions of Ordered Chapters a single Matroska file can present multiple edits of a film without duplicating content. Alternatively, if a videotape is digitized in full, one Ordered Edition could present the full content (including colorbars, countdown, slate, a feature presentation, and black frames), while another Edition of Ordered Chapters can use Chapters that only mark the intended presentation with the colorbars and other ancillary visual information excluded. If an Edition of Ordered Chapters is enabled, then the Matroska Player MUST play those Chapters in their stored order from the timestamp marked in the ChapterTimeStart Element to the timestamp marked in to ChapterTimeEnd Element. If the EditionFlagOrdered Flag is set to false, Simple Chapters are used and only the ChapterTimeStart of a Chapter is used as chapter mark to jump to the predefined point in the timeline. With Simple Chapters, a Matroska Player MUST ignore certain Chapter Elements. All these elements are now informational only. The following list shows the different usage of Chapter Elements between an ordered and non-ordered Edition.

Chapter elements / ordered Edition	False	True
ChapterUID	X	X
ChapterStringUID	X	X
ChapterTimeStart	X	X
ChapterTimeEnd	-	X
ChapterFlagHidden	X	X
ChapterFlagEnabled	X	X
ChapterSegmentUID	-	X
ChapterSegmentEditionUID	-	X
ChapterPhysicalEquiv	X	X
ChapterTrack	-	X
ChapterDisplay	X	X
ChapProcess	-	X

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

Other elements / ordered Edition	False	True
Info/SegmentFamily	-	X
Info/ChapterTranslate	-	X
Track/TrackTranslate	-	X

These other Elements belong to the Matroska DVD menu system and are only used when the ChapProcessCodecID Element is set to 1.

Ordered-Edition and Matroska Segment-Linking

Hard Linking: Ordered-Chapters supersedes the Hard Linking.
Soft Linking: In this complex system Ordered Chapters are REQUIRED and a Chapter CODEC MUST interpret the ChapProcess of all chapters.
Medium Linking: Ordered Chapters are used in a normal way and can be combined with the ChapterSegmentUID element which establishes a link to another Segment.

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

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

The EditionFlagOrdered Flag MUST be true.
The ChapterSegmentUID MUST NOT be the SegmentUID of its own Segment.
The linked Segments MUST BE in the same folder.

Variation 1: Linked-Duration Two more conditions MUST be met:

ChapterTimeStart and ChapterTimeEnd timestamps MUST be in the range of the linked Segment duration.
ChapterSegmentEditionUID MUST be not set.

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

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.

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. he private data depend on the type of menu system (stored in ChapProcessPrivate), idem for the data in the chapters (stored in ChapProcessData).

Matroska Script (0) This is the case when ChapProcessCodecID = 0. This is a script language build for Matroska purposes. The inspiration comes from ActionScript, javascript and other similar scripting languages. The commands are stored as text commands, in UTF-8. The syntax is C like, with commands spanned on many lines, each terminating with a ";". You can also include comments at the end of lines with "//" or comment many lines using "/* */". The scripts are stored in ChapProcessData. For the moment ChapProcessPrivate is not used. The one and only command existing for the moment is GotoAndPlay( ChapterUID );. As the same suggests, it means that, when this command is encountered, the Matroska Player SHOULD jump to the Chapter specified by the UID and play it.

DVD menu (1) This is the case when ChapProcessCodecID = 1. Each level of a chapter corresponds to a logical level in the DVD system that is stored in the first octet of the ChapProcessPrivate. This DVD hierarchy is as follows:

ChapProcessPrivate	DVD Name	Hierarchy	Commands Possible	Comment
0x30	SS	DVD domain	-	First Play, Video Manager, Video Title
0x2A	LU	Language Unit	-	Contains only PGCs
0x28	TT	Title	-	Contains only PGCs
0x20	PGC	Program Group Chain (PGC)	*
0x18	PG	Program 1 / Program 2 / Program 3	-
0x10	PTT	Part Of Title 1 / Part Of Title 2	-	Equivalent to the chapters on the sleeve.
0x08	CN	Cell 1 / Cell 2 / Cell 3 / Cell 4 / Cell 5 / Cell 6	-

You can also recover wether a Segment is a Video Manager (VMG), Video Title Set (VTS) or Video Title Set Menu (VTSM) from the ChapterTranslateID element found in the Segment Info. This field uses 2 octets as follows:

Domain Type: 0 for VMG, the domain number for VTS and VTSM
Domain Value: 0 for VMG and VTSM, 1 for the VTS source.

For instance, the menu part from VTS010.VOB would be coded [1,0] and the content part from VTS023.VOB would be [2,1]. The VMG is always [0,0] The following octets of ChapProcessPrivate are as follows:

Octet 1	DVD Name	Following Octets
0x30	SS	Domain name code (1: 0x00= First play, 0xC0= VMG, 0x40= VTSM, 0x80= VTS) + VTS(M) number (2)
0x2A	LU	Language code (2) + Language extension (1)
0x28	TT	global Title number (2) + corresponding TTN of the VTS (1)
0x20	PGC	PGC number (2) + Playback Type (1) + Disabled User Operations (4)
0x18	PG	Program number (2)
0x10	PTT	PTT-chapter number (1)
0x08	CN	Cell number [VOB ID(2)][Cell ID(1)][Angle Num(1)]

If the level specified in ChapProcessPrivate is a PGC (0x20), there is an octet called the Playback Type, specifying the kind of PGC defined:

0x00: entry only/basic PGC
0x82: Title+Entry Menu (only found in the Video Manager domain)
0x83: Root Menu (only found in the VTSM domain)
0x84: Subpicture Menu (only found in the VTSM domain)
0x85: Audio Menu (only found in the VTSM domain)
0x86: Angle Menu (only found in the VTSM domain)
0x87: Chapter Menu (only found in the VTSM domain)

The next 4 following octets correspond to the User Operation flags in the standard PGC. When a bit is set, the command SHOULD be disabled. ChapProcessData contains the pre/post/cell commands in binary format as there are stored on a DVD. There is just an octet preceding these data to specify the number of commands in the element. As follows: [# of commands(1)][command 1 (8)][command 2 (8)][command 3 (8)]. More information on the DVD commands and format on DVD-replica, where we got most of the info about it. You can also get information on DVD from the DVDinfo project.

Example 1 : basic chaptering In this example a movie is split in different chapters. It could also just be an audio file (album) on which each track corresponds to a chapter.

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

This would translate in the following matroska form : <Chapters> <EditionEntry> <EditionUID>16603393396715046047</EditionUID> <ChapterAtom> <ChapterUID>1193046</ChapterUID> <ChapterTimeStart>0</ChapterTimeStart> <ChapterTimeEnd>5000000000</ChapterTimeEnd> <ChapterDisplay> <ChapString>Intro</ChapString> <ChapLanguage>eng</ChapLanguage> </ChapterDisplay> <ChapterFlagHidden>0</ChapterFlagHidden> <ChapterFlagEnabled>1</ChapterFlagEnabled> </ChapterAtom> <ChapterAtom> <ChapterUID>2311527</ChapterUID> <ChapterTimeStart>5000000000</ChapterTimeStart> <ChapterTimeEnd>25000000000</ChapterTimeEnd> <ChapterDisplay> <ChapString>Before the crime</ChapString> <ChapLanguage>eng</ChapLanguage> </ChapterDisplay> <ChapterDisplay> <ChapString>Avant le crime</ChapString> <ChapLanguage>fra</ChapLanguage> </ChapterDisplay> <ChapterFlagHidden>0</ChapterFlagHidden> <ChapterFlagEnabled>1</ChapterFlagEnabled> </ChapterAtom> <ChapterAtom> <ChapterUID>3430008</ChapterUID> <ChapterTimeStart>25000000000</ChapterTimeStart> <ChapterTimeEnd>27500000000</ChapterTimeEnd> <ChapterDisplay> <ChapString>The crime</ChapString> <ChapLanguage>eng</ChapLanguage> </ChapterDisplay> <ChapterDisplay> <ChapString>Le crime</ChapString> <ChapLanguage>fra</ChapLanguage> </ChapterDisplay> <ChapterFlagHidden>0</ChapterFlagHidden> <ChapterFlagEnabled>1</ChapterFlagEnabled> </ChapterAtom> <ChapterAtom> <ChapterUID>4548489</ChapterUID> <ChapterTimeStart>27500000000</ChapterTimeStart> <ChapterTimeEnd>38000000000</ChapterTimeEnd> <ChapterDisplay> <ChapString>After the crime</ChapString> <ChapLanguage>eng</ChapLanguage> </ChapterDisplay> <ChapterDisplay> <ChapString>Après le crime</ChapString> <ChapLanguage>fra</ChapLanguage> </ChapterDisplay> <ChapterFlagHidden>0</ChapterFlagHidden> <ChapterFlagEnabled>1</ChapterFlagEnabled> </ChapterAtom> <ChapterAtom> <ChapterUID>5666960</ChapterUID> <ChapterTimeStart>38000000000</ChapterTimeStart> <ChapterTimeEnd>43000000000</ChapterTimeEnd> <ChapterDisplay> <ChapString>Credits</ChapString> <ChapLanguage>eng</ChapLanguage> </ChapterDisplay> <ChapterDisplay> <ChapString>Générique</ChapString> <ChapLanguage>fra</ChapLanguage> </ChapterDisplay> <ChapterFlagHidden>0</ChapterFlagHidden> <ChapterFlagEnabled>1</ChapterFlagEnabled> </ChapterAtom> <EditionFlagDefault>0</EditionFlagDefault> <EditionFlagHidden>0</EditionFlagHidden> </EditionEntry> </Chapters>

Example 2 : nested chapters In this example an (existing) album is split into different chapters, and one of them contain another splitting.

The Micronauts "Bleep To Bleep"

00:00 - 12:28 : Baby Wants To Bleep/Rock
- 00:00 - 04:38 : Baby wants to bleep (pt.1)
- 04:38 - 07:12 : Baby wants to rock
- 07:12 - 10:33 : Baby wants to bleep (pt.2)
- 10:33 - 12:28 : Baby wants to bleep (pt.3)
12:30 - 19:38 : Bleeper_O+2
19:40 - 22:20 : Baby wants to bleep (pt.4)
22:22 - 25:18 : Bleep to bleep
25:20 - 33:35 : Baby wants to bleep (k)
33:37 - 44:28 : Bleeper

<Chapters> <EditionEntry> <EditionUID>1281690858003401414</EditionUID> <ChapterAtom> <ChapterUID>1</ChapterUID> <ChapterTimeStart>0</ChapterTimeStart> <ChapterTimeEnd>748000000</ChapterTimeEnd> <ChapterDisplay> <ChapString>Baby wants to Bleep/Rock</ChapString> <ChapLanguage>eng</ChapLanguage> </ChapterDisplay> <ChapterAtom> <ChapterUID>2</ChapterUID> <ChapterTimeStart>0</ChapterTimeStart> <ChapterTimeEnd>278000000</ChapterTimeEnd> <ChapterDisplay> <ChapString>Baby wants to bleep (pt.1)</ChapString> <ChapLanguage>eng</ChapLanguage> </ChapterDisplay> <ChapterFlagHidden>0</ChapterFlagHidden> <ChapterFlagEnabled>1</ChapterFlagEnabled> </ChapterAtom> <ChapterAtom> <ChapterUID>3</ChapterUID> <ChapterTimeStart>278000000</ChapterTimeStart> <ChapterTimeEnd>432000000</ChapterTimeEnd> <ChapterDisplay> <ChapString>Baby wants to rock</ChapString> <ChapLanguage>eng</ChapLanguage> </ChapterDisplay> <ChapterFlagHidden>0</ChapterFlagHidden> <ChapterFlagEnabled>1</ChapterFlagEnabled> </ChapterAtom> <ChapterAtom> <ChapterUID>4</ChapterUID> <ChapterTimeStart>432000000</ChapterTimeStart> <ChapterTimeEnd>633000000</ChapterTimeEnd> <ChapterDisplay> <ChapString>Baby wants to bleep (pt.2)</ChapString> <ChapLanguage>eng</ChapLanguage> </ChapterDisplay> <ChapterFlagHidden>0</ChapterFlagHidden> <ChapterFlagEnabled>1</ChapterFlagEnabled> </ChapterAtom> <ChapterAtom> <ChapterUID>5</ChapterUID> <ChapterTimeStart>633000000</ChapterTimeStart> <ChapterTimeEnd>748000000</ChapterTimeEnd> <ChapterDisplay> <ChapString>Baby wants to bleep (pt.3)</ChapString> <ChapLanguage>eng</ChapLanguage> </ChapterDisplay> <ChapterFlagHidden>0</ChapterFlagHidden> <ChapterFlagEnabled>1</ChapterFlagEnabled> </ChapterAtom> <ChapterFlagHidden>0</ChapterFlagHidden> <ChapterFlagEnabled>1</ChapterFlagEnabled> </ChapterAtom> <ChapterAtom> <ChapterUID>6</ChapterUID> <ChapterTimeStart>750000000</ChapterTimeStart> <ChapterTimeEnd>1178500000</ChapterTimeEnd> <ChapterDisplay> <ChapString>Bleeper_O+2</ChapString> <ChapLanguage>eng</ChapLanguage> </ChapterDisplay> <ChapterFlagHidden>0</ChapterFlagHidden> <ChapterFlagEnabled>1</ChapterFlagEnabled> </ChapterAtom> <ChapterAtom> <ChapterUID>7</ChapterUID> <ChapterTimeStart>1180500000</ChapterTimeStart> <ChapterTimeEnd>1340000000</ChapterTimeEnd> <ChapterDisplay> <ChapString>Baby wants to bleep (pt.4)</ChapString> <ChapLanguage>eng</ChapLanguage> </ChapterDisplay> <ChapterFlagHidden>0</ChapterFlagHidden> <ChapterFlagEnabled>1</ChapterFlagEnabled> </ChapterAtom> <ChapterAtom> <ChapterUID>8</ChapterUID> <ChapterTimeStart>1342000000</ChapterTimeStart> <ChapterTimeEnd>1518000000</ChapterTimeEnd> <ChapterDisplay> <ChapString>Bleep to bleep</ChapString> <ChapLanguage>eng</ChapLanguage> </ChapterDisplay> <ChapterFlagHidden>0</ChapterFlagHidden> <ChapterFlagEnabled>1</ChapterFlagEnabled> </ChapterAtom> <ChapterAtom> <ChapterUID>9</ChapterUID> <ChapterTimeStart>1520000000</ChapterTimeStart> <ChapterTimeEnd>2015000000</ChapterTimeEnd> <ChapterDisplay> <ChapString>Baby wants to bleep (k)</ChapString> <ChapLanguage>eng</ChapLanguage> </ChapterDisplay> <ChapterFlagHidden>0</ChapterFlagHidden> <ChapterFlagEnabled>1</ChapterFlagEnabled> </ChapterAtom> <ChapterAtom> <ChapterUID>10</ChapterUID> <ChapterTimeStart>2017000000</ChapterTimeStart> <ChapterTimeEnd>2668000000</ChapterTimeEnd> <ChapterDisplay> <ChapString>Bleeper</ChapString> <ChapLanguage>eng</ChapLanguage> </ChapterDisplay> <ChapterFlagHidden>0</ChapterFlagHidden> <ChapterFlagEnabled>1</ChapterFlagEnabled> </ChapterAtom> <EditionFlagDefault>0</EditionFlagDefault> <EditionFlagHidden>0</EditionFlagHidden> </EditionEntry> </Chapters>

Attachments Matroska supports storage of related files and data in the Attachments Element (a Top-Level Element). Attachment Elements can be used to store related cover art, font files, transcripts, reports, error recovery files, picture, or text-based annotations, copies of specifications, or other ancillary files related to the Segment. Matroska Readers MUST NOT execute files stored as Attachment Elements.

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.

FileName	Image Orientation	Pixel Length of Smallest Side
cover.jpg	Portrait or square	600
small_cover.png	Portrait or square	120
cover_land.png	Landscape	600
smallcoverland.jpg	Landscape	120

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.

Recommendations The following recommendations are provided to optimize Matroska performance.

Unless Matroska is used as a live stream, it SHOULD contain a Cues Element.
For each video track, each keyframe SHOULD be referenced by a CuePoint Element.
It is RECOMMENDED to not reference non-keyframes of video tracks in Cues unless it references a Cluster Element which contains a CodecState Element but no keyframes.
For each subtitle track present, each subtitle frame SHOULD be referenced by a CuePoint Element with a CueDuration Element.
References to audio tracks MAY be skipped in CuePoint Elements if a video track is present. When included the CuePoint Elements SHOULD reference audio keyframes at most once every 500 milliseconds.
If the referenced frame is not stored within the first SimpleBlock, or first BlockGroup within its Cluster Element, then the CueRelativePosition Element SHOULD be written to reference where in the Cluster the reference frame is stored.
If a CuePoint Element references Cluster Element that includes a CodecState Element, then that CuePoint Element MUST use a CueCodecState Element.
CuePoint Elements SHOULD be numerically sorted in storage order by the value of the CueTime Element.

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

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.

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.

Menu Specifications This document is a draft of the Menu system that will be the default one in Matroska. As it will just be composed of a Control Track, it will be seen as a "codec" and could be replaced later by something else if needed. A menu is like what you see on DVDs, when you have some screens to select the audio format, subtitles or scene selection.

Requirements What we'll try to have is a system that can do almost everything done on a DVD, or more, or better, or drop the unused features if necessary. As the name suggests, a Control Track is a track that can control the playback of the file and/or all the playback features. To make it as simple as possible for Matroska Players, the Control Track will just give orders to the Matroska Player and get the actions associated with the highlights/hotspots.

Highlights/Hotspots A highlight is basically a rectangle/key associated with an action UID. When that rectangle/key is activated, the Matroska Player send the UID of the action to the Control Track handler (codec). The fact that it can also be a key means that even for audio only files, a keyboard shortcut or button panel could be used for menus. But in that case, the hotspot will have to be associated with a name to display. This highlight is sent from the Control Track to the Matroska Player. Then the Matroska Player has to handle that highlight until it's deactivated; see . The highlight contains a UID of the action, a displayable name (UTF-8), an associated key (list of keys to be defined, probably up/down/left/right/select), a screen position/range and an image to display. The image will be displayed either when the user place the mouse over the rectangle (or any other shape), or when an option of the screen is selected (not activated). There could be a second image used when the option is activated. And there could be a third image that can serve as background. This way you could have a still image (like in some DVDs) for the menu and behind that image blank video (small bitrate). When a highlight is activated by the user, the Matroska Player has to send the UID of the action to the Control Track. Then the Control Track codec will handle the action and possibly give new orders to the Matroska Player. The format used for storing images SHOULD be extensible. For the moment we'll use PNG and BMP, both with alpha channel.

Playback features All the following features will be sent from the Control Track to the Matroska Player :

Jump to chapter (UID, prev, next, number)
Disable all tracks of a kind (audio, video, subtitle)
Enable track UID (the kind doesn't matter)
Define/Disable a highlight
Enable/Disable jumping
Enable/Disable track selection of a kind
Select Edition ID (see chapters)
Pause playback
Stop playback
Enable/Disable a Chapter UID
Hide/Unhide a Chapter UID

All the actions will be written in a normal Matroska track, with a timestamp. A "Menu Frame" SHOULD be able to contain more that one action/highlight for a given timestamp. (to be determined, EBML format structure)

Player requirements Some Matroska Players might not support the control track. That mean they will play the active/looped parts as part of the data. So I suggest putting the active/looped parts of a movie at the end of a movie. When a Menu-aware Matroska Player encounter the default Control Track of a Matroska file, the first order SHOULD be to jump at the start of the active/looped part of the movie.

Working Graph Matroska Source file -> Control Track <-> Player. -> other tracks -> rendered

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.

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

DefaultDecodedFieldDuration The DefaultDecodedFieldDuration Element can signal to the displaying application how often fields of a video sequence will be available for displaying. It can be used for both interlaced and progressive content. If the video sequence is signaled as interlaced, then the period between two successive fields at the output of the decoding process equals DefaultDecodedFieldDuration. For video sequences signaled as progressive, it is twice the value of DefaultDecodedFieldDuration. These values are valid at the end of the decoding process before post-processing (such as deinterlacing or inverse telecine) is applied. Examples:

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

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.

Image Presentation

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

Rotation The ProjectionPoseRoll Element (see ) 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 ) and the ProjectionPoseRoll Element represents a video track where the image SHOULD be presentation with a 90 degree counter-clockwise rotation. <Projection> <ProjectionPoseRoll>90</ProjectionPoseRoll> </Projection>

Matroska versioning The EBML Header of each Matroska document informs the reading application on what version of Matroska to expect. The Elements within EBML Header with jurisdiction over this information are DocTypeVersion and DocTypeReadVersion. DocTypeVersion MUST be equal to or greater than the highest Matroska version number of any Element present in the Matroska file. For example, a file using the SimpleBlock Element MUST have a DocTypeVersion equal to or greater than 2. A file containing CueRelativePosition Elements MUST have a DocTypeVersion equal to or greater than 4. The DocTypeReadVersion MUST contain the minimum version number that a reading application can minimally support in order to play the file back -- optionally with a reduced feature set. For example, if a file contains only Elements of version 2 or lower except for CueRelativePosition (which is a version 4 Matroska Element), then DocTypeReadVersion SHOULD still be set to 2 and not 4 because evaluating CueRelativePosition is not necessary for standard playback -- it makes seeking more precise if used. DocTypeVersion MUST always be equal to or greater than DocTypeReadVersion. A reading application supporting Matroska version V MUST NOT refuse to read an application with DocReadTypeVersion equal to or lower than V even if DocTypeVersion is greater than V. See also the note about Unknown Elements in .

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

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.

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

Example of Segment Position This table presents an example of Segment Position by showing a hexadecimal representation of a very small Matroska file with labels to show the offsets in octets. The file contains a Segment Element with an Element ID of "0x18538067" and a MuxingApp Element with an Element ID of "0x4D80". 0 1 2 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ 0 |1A|45|DF|A3|8B|42|82|88|6D|61|74|72|6F|73|6B|61|18|53|80|67| 20 |93|15|49|A9|66|8E|4D|80|84|69|65|74|66|57|41|84|69|65|74|66| In the above example, the Element ID of the Segment Element is stored at offset 16, the Element Data Size of the Segment Element is stored at offset 20, and the Element Data of the Segment Element is stored at offset 21. 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'.

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.

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.

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

An other example where only the NextUID Element is used.

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

A next example where only the PrevUID Element is used.

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

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

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

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.

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.

Track Flags

Default flag The "default track" flag is a hint for a Matroska Player and SHOULD always be changeable by the user. If the user wants to see or hear a track of a certain kind (audio, video, subtitles) and hasn't chosen a specific track, the Matroska Player SHOULD use the first track of that kind whose "default track" flag is set to "1". If no such track is found, then the first track of this kind SHOULD be chosen. Only one track of a kind MAY have its "default track" flag set in a segment. If a track entry does not contain the "default track" flag element, then its default value "1" is to be used.

Forced flag The "forced" flag tells the Matroska Player that it MUST display/play this track or another track of the same kind that also has its "forced" flag set. When there are multiple "forced" tracks, the Matroska Player SHOULD determine the track based upon the language of the forced flag or use the default flag if no track matches the use languages. Another track of the same kind without the "forced" flag may be use simultaneously with the "forced" track, like DVD subtitles.

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.

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.

Multi-planar and 3D videos There are two different ways to compress 3D videos: have each eye track in a separate track and have one track have both eyes combined inside (which is more efficient, compression-wise). Matroska supports both ways. For the single track variant, there is the StereoMode Element, which defines how planes are assembled in the track (mono or left-right combined). Odd values of StereoMode means the left plane comes first for more convenient reading. The pixel count of the track (PixelWidth/PixelHeight) is the raw amount of pixels, for example 3840x1080 for full HD side by side, and the DisplayWidth/DisplayHeight in pixels is the amount of pixels for one plane (1920x1080 for that full HD stream). Old stereo 3D were displayed using anaglyph (cyan and red colours separated). For compatibility with such movies, there is a value of the StereoMode that corresponds to AnaGlyph. There is also a "packed" mode (values 13 and 14) which consists of packing two frames together in a Block using lacing. The first frame is the left eye and the other frame is the right eye (or vice versa). The frames SHOULD be decoded in that order and are possibly dependent on each other (P and B frames). For separate tracks, Matroska needs to define exactly which track does what. TrackOperation with TrackCombinePlanes do that. For more details look at 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.

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.

Timestamp Types

Absolute Timestamp = Block+Cluster
Relative Timestamp = Block
Scaled Timestamp = Block+Cluster
Raw Timestamp = (Block+Cluster)*TimestampScale*TrackTimestampScale

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 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.

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.

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.

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. 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 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:

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.
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.

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. 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 , 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 , 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. 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.