cellar S. Lhomme Internet-Draft Intended status: Standards Track M. Bunkus Expires: 4 August 2026 D. Rice 31 January 2026 Matroska Media Container Tag Specifications draft-ietf-cellar-tags-21 Abstract Matroska is a multimedia container format defined in [RFC9559]. It can store timestamped multimedia data but also chapters and tags. The Tag elements add important metadata to identify and classify the information found in a Matroska Segment. This document defines the Matroska multimedia container tags, namely the tag names and their respective semantic meaning. Status of This Memo This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet- Drafts is at https://datatracker.ietf.org/drafts/current/. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." This Internet-Draft will expire on 4 August 2026. Copyright Notice Copyright (c) 2026 IETF Trust and the persons identified as the document authors. All rights reserved. This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (https://trustee.ietf.org/ license-info) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights Lhomme, et al. Expires 4 August 2026 [Page 1] Internet-Draft Matroska Tags January 2026 and restrictions with respect to this document. Code Components extracted from this document must include Revised BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Revised BSD License. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 2. Notation and Conventions . . . . . . . . . . . . . . . . . . 3 3. Tagging . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 3.1. Why Assigned Tags Matter . . . . . . . . . . . . . . . . 4 3.2. Tag Formatting . . . . . . . . . . . . . . . . . . . . . 5 3.2.1. TagName Formatting . . . . . . . . . . . . . . . . . 5 3.2.2. TagString Formatting . . . . . . . . . . . . . . . . 5 3.2.2.1. Date Tags Formatting . . . . . . . . . . . . . . 6 3.2.2.2. Number Tags Formatting . . . . . . . . . . . . . 7 3.2.2.3. Country Code Tags Formatting . . . . . . . . . . 8 3.3. Target Types . . . . . . . . . . . . . . . . . . . . . . 8 3.3.1. Target Types Parts . . . . . . . . . . . . . . . . . 11 3.4. Multiple Targets UID . . . . . . . . . . . . . . . . . . 15 4. Assigned Tags . . . . . . . . . . . . . . . . . . . . . . . . 19 4.1. Nesting Information . . . . . . . . . . . . . . . . . . . 19 4.2. Organization Information . . . . . . . . . . . . . . . . 20 4.3. Titles . . . . . . . . . . . . . . . . . . . . . . . . . 21 4.4. Nested Information . . . . . . . . . . . . . . . . . . . 21 4.5. Entities . . . . . . . . . . . . . . . . . . . . . . . . 23 4.6. Search and Classification . . . . . . . . . . . . . . . . 26 4.7. Temporal Information . . . . . . . . . . . . . . . . . . 28 4.8. Spatial Information . . . . . . . . . . . . . . . . . . . 29 4.9. User Information . . . . . . . . . . . . . . . . . . . . 30 4.10. Technical Information . . . . . . . . . . . . . . . . . . 31 4.11. External Identifiers . . . . . . . . . . . . . . . . . . 36 4.12. Commercial . . . . . . . . . . . . . . . . . . . . . . . 37 4.13. Legal . . . . . . . . . . . . . . . . . . . . . . . . . . 38 5. Security Considerations . . . . . . . . . . . . . . . . . . . 38 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 39 6.1. Matroska Tags Names Registry . . . . . . . . . . . . . . 39 6.2. Guidelines for the Designated Experts . . . . . . . . . . 47 7. References . . . . . . . . . . . . . . . . . . . . . . . . . 47 7.1. Normative References . . . . . . . . . . . . . . . . . . 47 7.2. Informative References . . . . . . . . . . . . . . . . . 50 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 50 1. Introduction The Tag elements can tag a whole Segment, separate Tracks elements, individual Chapter elements or Attachments elements. Lhomme, et al. Expires 4 August 2026 [Page 2] Internet-Draft Matroska Tags January 2026 Some details about tagging are already present in Section 24 of [RFC9559]. Readers of this document should be familiar with that section, the different high level parts of Matroska as defined in Section 4.5 of [RFC9559] and EBML Master Elements as defined in Section 7.7 of [RFC8794]. While the Matroska tagging framework allows anyone to create their own custom tags, it is important to have a common set of values for interoperability. 2. Notation and Conventions The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all capitals, as shown here. 3. Tagging When a SimpleTag is nested within another SimpleTag, the nested SimpleTag becomes an attribute of its parent SimpleTag. For instance, if one wanted to store the dates that a singer started being the lead performer, then your SimpleTag tree would look something like this: * Targets - TagTrackUID = {track UID of tagged content}. * ARTIST = "Band Name" - LEAD_PERFORMER = "John Doe" o DATE_STARTED = "1981-08" This corresponds to this layout of EBML elements: Lhomme, et al. Expires 4 August 2026 [Page 3] Internet-Draft Matroska Tags January 2026 {track UID of tagged content} ARTIST Band Name LEAD_PERFORMER John Doe DATE_STARTED 1981-08 In this way, it becomes possible to store any SimpleTag as an attribute of another SimpleTag. 3.1. Why Assigned Tags Matter There is a debate between people who think all tags should be free- form and those who think all tags should be limited to a set of names. The recommendations in this document are in between. An application intended for advanced users might permit the insertion of any tag in a file. While this provides maximum flexibility, custom or exotic tags generally limit interoperable use. Well-known tags improve the ability of others to read and reuse them; most applications will therefore use a small list of useful tags. So hopefully, when someone wants to put information in one's file, they will find an assigned one, i.e., found in the IANA Matroska Tags Names registry Section 6.1, that fits their need and hopefully use it. If it is not in the list, this person can try to add a new tag in the registry. This registry is not meant to have every possible information in a file. Matroska files are not meant to become a Lhomme, et al. Expires 4 August 2026 [Page 4] Internet-Draft Matroska Tags January 2026 whole database of people who made costumes for a film. A website would be better for that. It's hard to define what should be in and what ought not be in a file because it doesn't make sense; thus, each request needs to be evaluated to determine if it makes sense to be carried over in a file for storage and/or sharing or if it doesn't belong there. We also need an assigned list simply for developers to be able to display relevant information in their own design, if they choose to support a list of meta-information they should know which tag has the desired meaning so that other apps could understand the same meaning. 3.2. Tag Formatting 3.2.1. TagName Formatting Assigned TagName values MUST consist of latin capital letters, numbers and the underscore character '_'. Assigned TagName values MUST NOT contain any space. Assigned TagName values MUST NOT start with the underscore character '_'; see Section 3.1. It is RECOMMENDED that tag names start with the underscore character '_' for unassigned tags that are not meant to be added to the list of assigned tags. The syntax of assigned TagName values is defined using this Augmented Backus-Naur Form (ABNF) [RFC5234] notation: TagName = FirstCharacter [Character] FirstCharacter = CapitalLetter / DIGIT Character = CapitalLetter / DIGIT / Underscore CapitalLetter = %x41-5A ; "A" to "Z" Underscore = %x5F ; "_" 3.2.2. TagString Formatting Although tags are metadata mostly used for reading, there are cases where the string value could be used for sorting, categorization, etc. For this reason, when possible, strict formatting of the value should be used to improve interoperability. Lhomme, et al. Expires 4 August 2026 [Page 5] Internet-Draft Matroska Tags January 2026 Multiple items SHOULD NOT be stored as a list in a single TagString. If there is more than one tag value with the same name to be stored, it is RECOMMENDED to use separate SimpleTags with that name for each value. Preexisting files may have used multiple values in the same TagString but given there are no defined delimiters they cannot be easily split into multiple elements. INSTRUMENTS (Section 4.4) and KEYWORDS (Section 4.6) tags allow using a comma as a separator. However, it is RECOMMENDED to use separate SimpleTags with each containing a single instrument or keyword value, respectively. Due to the varied nature of tag sources it may also not always possible to know programmatically whether a value is a list that must be split or not. 3.2.2.1. Date Tags Formatting TagString fields defined in this document with dates MUST have the following format: "YYYY-MM-DD hh:mm:ss.mss" or a reduced version. The format is similar to the [ISO8601] date and time format defined in Appendix A of [RFC3339] without the "T" separator, without the time offset and with the addition of the milliseconds "mss". The date and times represented are in Coordinated Universal Time (UTC). Date and times are usually not precise to a particular millisecond. To store less accurate dates, parts of the date string are removed starting from the right. For instance, to store only the year, one would use "2004". To store a specific day such as May 1st, 2003, one would use "2003-05-01". The syntax of this tags-date-time is defined using this Augmented Backus-Naur Form (ABNF) [RFC5234]: Lhomme, et al. Expires 4 August 2026 [Page 6] Internet-Draft Matroska Tags January 2026 time-hour = 2DIGIT ; 00-24 time-minute = 2DIGIT ; 00-59 time-second = 2DIGIT ; 00-58, 00-59, 00-60 based on ; leap-second rules time-millisecond = 3DIGIT ; 000-999 timespec-hour = time-hour timespec-minute = timespec-hour ":" time-minute timespec-second = timespec-minute ":" time-second timespec-milli = timespec-second "." time-millisecond time = timespec-hour / timespec-minute / timespec-second / timespec-milli date-fullyear = 4DIGIT ; 0000-9999 date-month = 2DIGIT ; 01-12 date-mday = 2DIGIT ; 01-28, 01-29, 01-30, 01-31 based on ; month/year datespec-year = date-fullyear datespec-month = datespec-year "-" date-month datespec-full = datespec-month "-" date-mday datespec-time = datespec-full " " time tags-date-time = datespec-time / datespec-full / datespec-month / datespec-year 3.2.2.2. Number Tags Formatting TagString fields that require a floating-point number MUST use the "." mark instead of the "," mark. Only ASCII numbers "0" to "9" and the "." character MUST be used. The "." separator represents the boundary between the integer value and the decimal parts. If the string doesn't contain the "." separator, the value is an integer value. Digit grouping delimiters MUST NOT be used. The integer value and decimal parts are values in base 10. To display it differently for another locale, it is RECOMMENDED that applications support auto replacement on display. The thousand separator MAY be inserted for display purposes. The decimal separator "." MAY be replaced to match the user locale for display purposes. In legacy media containers, it is possible that the "," character might have been used as a separator or that digit grouping delimiters might have been used. A Matroska Reader SHOULD use the following character handling to parse such legacy formats: Lhomme, et al. Expires 4 August 2026 [Page 7] Internet-Draft Matroska Tags January 2026 * if multiple instances of the same non-number character are found, they are ignored, * if only one "." character is found and no other non-number character is found, the "." is the integer-decimal separator, * if only one "," character is found and no other non-number character is found, the "," is a digit grouping delimiter, * any other non-number character is ignored. 3.2.2.3. Country Code Tags Formatting TagString fields that use a Country Code MUST use the Matroska countries form defined in Section 13 of [RFC9559], i.e., [RFC5646] two-letter region subtags, without the UK exception. 3.3. Target Types The TargetTypeValue element allows tagging of different parts that are within or outside a given file. For example, in an audio file with one song you could have information about the CD set album it comes from, even if the whole CD set is not found in the file. For applications to know the kind of information (e.g., "TITLE") relates to a certain level (CD title or track title), we also need a set of official TargetTypeValue values and TargetType names. That also means the same tag name can have different meanings depending on its TargetTypeValue, otherwise we would end up with 7 "TITLE_" tag names. For human readability, a TargetType string can be added next to the corresponding TargetTypeValue. Audio and video have different TargetType values. The following table summarizes the TargetType values found in Section 5.1.8.1.1.2 of [RFC9559] for audio and video content: Lhomme, et al. Expires 4 August 2026 [Page 8] Internet-Draft Matroska Tags January 2026 +=================+=================+===============================+ | TargetTypeValue | Audio | Comment | | | TargetType | | +=================+=================+===============================+ | 70 | COLLECTION | the high hierarchy consisting | | | | of many different lower items | +-----------------+-----------------+-------------------------------+ | 60 | EDITION / | a list of lower levels | | | ISSUE / | grouped together | | | VOLUME / OPUS | | +-----------------+-----------------+-------------------------------+ | 50 | ALBUM / OPERA | the most common grouping | | | / CONCERT | level of music (e.g., an | | | | album) | +-----------------+-----------------+-------------------------------+ | 40 | PART / | when an album has different | | | SESSION | logical parts | +-----------------+-----------------+-------------------------------+ | 30 | TRACK / SONG | the common parts of an album | +-----------------+-----------------+-------------------------------+ | 20 | SUBTRACK / | corresponds to parts of a | | | PART / | track for audio (e.g., a | | | MOVEMENT | movement) | +-----------------+-----------------+-------------------------------+ | 10 | - | the lowest hierarchy found in | | | | music | +-----------------+-----------------+-------------------------------+ Table 1: TargetTypeValue Values Audio Semantic Description Lhomme, et al. Expires 4 August 2026 [Page 9] Internet-Draft Matroska Tags January 2026 +=================+=================+===============================+ | TargetTypeValue | Video | Comment | | | TargetType | | +=================+=================+===============================+ | 70 | COLLECTION | the high hierarchy consisting | | | | of many different lower items | +-----------------+-----------------+-------------------------------+ | 60 | SEASON / | a list of lower levels | | | SEQUEL / | grouped together | | | VOLUME | | +-----------------+-----------------+-------------------------------+ | 50 | MOVIE / | the most common grouping | | | EPISODE / | level of video (e.g., an | | | CONCERT | episode for TV series) | +-----------------+-----------------+-------------------------------+ | 40 | PART / | when an episode has different | | | SESSION | logical parts | +-----------------+-----------------+-------------------------------+ | 30 | CHAPTER | the common parts of a movie | | | | or episode | +-----------------+-----------------+-------------------------------+ | 20 | SCENE | a sequence of continuous | | | | action in a film or video | +-----------------+-----------------+-------------------------------+ | 10 | SHOT | the lowest hierarchy found in | | | | movies | +-----------------+-----------------+-------------------------------+ Table 2: TargetTypeValue Values Video Semantic Description A tag defined for a given TargetTypeValue also applies to all Targets with numerically smaller TargetTypeValues in the same hierarchy, that is, from higher-level groups to lower-level entities. This means that if a CD has the same artist for all tracks, you just need to set the "ARTIST" tag at TargetTypeValue 50 (ALBUM) and not to each TargetTypeValue 30 (TRACK), but you can also repeat the value for each track. If some tracks of that CD have no known "ARTIST", the value MUST be set to an empty string ("") as detailed in Section 24.2 of [RFC9559], so that the album "ARTIST" doesn't apply. If a tag with a given TagName is found at a TargetTypeValue, only values of that TagName are valid at that TargetTypeValue level. In other words, the TagName values from upper TargetTypeValue levels don't apply at that level. Multiple SimpleTags with the same TagName can be used at a given TargetTypeValue level when each SimpleTag contain a TagString. For example this can be useful to find a single "ARTIST" even when they Lhomme, et al. Expires 4 August 2026 [Page 10] Internet-Draft Matroska Tags January 2026 are found in a collaboration. The concatenation of each TagString represents the value for the TagName at this level. The presentation, for instance with a separator, is up to the application. 3.3.1. Target Types Parts There are three organizational tags defined in Section 4.2: * TOTAL_PARTS * PART_NUMBER * PART_OFFSET These tags allow specifying the ordering of some tags within another group of tags. For example if an album has 10 tracks, tag the second track from it, you set "TOTAL_PARTS" to "10" at TargetTypeValue 50 (ALBUM). It means the "ALBUM" contains 10 lower parts. The lower part in question is the first lower TargetTypeValue that is specified in the file. TargetTypeValue = 30 (TRACK) would mean the album contains 10 tracks. TargetTypeValue = 20 (MOVEMENT) would mean the album contains 10 movements, etc. And since it's the second track within the album, the "PART_NUMBER" at TargetTypeValue 30 (TRACK) is set to "2". If the parts are split into multiple logical entities, you can also use "PART_OFFSET". For example you are tagging the third track of the second CD of a double CD album with a total of 10 tracks the "TOTAL_PARTS" at TargetTypeValue 50 (ALBUM) is "10", the "PART_NUMBER" at TargetTypeValue 30 (TRACK) is "3", and the "PART_OFFSET" at TargetTypeValue 30 (TRACK) is "5", which is the number of tracks on the first CD. When a TargetTypeValue level doesn't exist, it MUST NOT be specified in the files, so that the "TOTAL_PARTS" and "PART_NUMBER" elements match the same levels. Here is an example of an audio record with 2 tracks in a single file. The name of the record is also the name of the first track "Main Title". There is one Tag element for the record, and one Tag element per track on the record. Each track is identified by a chapter via a TagChapterUID element which value corresponds to the UID of a ChapterUID as defined in Section 5.1.8.1.1.5 of [RFC9559]. The Tag for the record: Lhomme, et al. Expires 4 August 2026 [Page 11] Internet-Draft Matroska Tags January 2026 * Targets - TargetTypeValue = 50 * ARTIST = "Dummy Artist Name" * TITLE = "Main Title" * TOTAL_PARTS = "2" The Tag for the first track: * Targets - TargetTypeValue = 30 - TagChapterUID = 12345 * TITLE = "Main Title" * PART_NUMBER = "1" The Tag for the second track: * Targets - TargetTypeValue = 30 - TagChapterUID = 67890 * TITLE = "B-side Track Name" * PART_NUMBER = "2" This corresponds to this layout of EBML elements: 50 ARTIST Dummy Artist Name Lhomme, et al. Expires 4 August 2026 [Page 12] Internet-Draft Matroska Tags January 2026 TITLE Main Title TOTAL_PARTS 2 30 12345 TITLE Main Title PART_NUMBER 1 30 67890 TITLE B-side Track Name PART_NUMBER 2 Lhomme, et al. Expires 4 August 2026 [Page 13] Internet-Draft Matroska Tags January 2026 Here is an example using the "PART_OFFSET" tag. It corresponds to a file that contains the third track on the second CD of the 2-CD album: The Tag for the album: * Targets - TargetTypeValue = 50 * ARTIST = "The Album Artist" - SORT_WITH = "Album Artist, The" * TITLE = "Album Title" * TOTAL_PARTS = "10" The Tag for the third track of the second CD: * Targets - TargetTypeValue = 30 * TITLE = "Some Track Title" * PART_NUMBER = "3" * PART_OFFSET = "5" This corresponds to this layout of EBML elements: 50 ARTIST The Album Artist SORT_WITH Album Artist, The Lhomme, et al. Expires 4 August 2026 [Page 14] Internet-Draft Matroska Tags January 2026 TITLE Album Title TOTAL_PARTS 10 30 TITLE Some Track Title PART_NUMBER 3 PART_OFFSET 5 3.4. Multiple Targets UID A Tag element has a single Targets element with a single TargetTypeValue element. However, the Targets element can contain various TagTrackUID, TagEditionUID, TagChapterUID and TagAttachmentUID elements. Lhomme, et al. Expires 4 August 2026 [Page 15] Internet-Draft Matroska Tags January 2026 When multiple values are found using the same Tag UID element (e.g., TagTrackUID) a logical OR is applied on these elements. In other words, the tags apply to each entity defined by a UID. This is the list of UIDs the tags apply to (e.g., list of TagTrackUID). Such a list may contain a single UID element. When different lists of Tag UID elements are found (e.g., a list of TagTrackUID and a list of TagChapterUID) a logical AND is applied between those lists. In other words, the tags apply only to the entities matching a UID in each list of Tag UID elements. These operations allow factorizing tags that would otherwise need to be repeated multiple times. Here is an example of a Tag applying to 2 chapters, using the same example as in Section 3.3.1: * Targets - TargetTypeValue = 30 - TagChapterUID = 12345 - TagChapterUID = 67890 * WRITTEN_BY = "John Doe" * WRITTEN_BY = "Jane Smith" * PRODUCER = "John Doe" * PRODUCER = "Jane Smith" This corresponds to this layout of EBML elements: Lhomme, et al. Expires 4 August 2026 [Page 16] Internet-Draft Matroska Tags January 2026 30 12345 67890 WRITTEN_BY John Doe WRITTEN_BY Jane Smith PRODUCER John Doe PRODUCER Jane Smith Some combinations of different Tag UID elements are not possible. A TagChapterUID and TagAttachmentUID can't be mixed because there is no overlap with a Chapter and an Attachment that would make sense. An attachment applies to the whole segment and can be tied to tracks, via \Segment\Tracks\TrackEntry\AttachmentLink as defined in Section 5.1.4.1.24 of [RFC9559], but not chapters. Lhomme, et al. Expires 4 August 2026 [Page 17] Internet-Draft Matroska Tags January 2026 Mixing TagEditionUID and TagChapterUID elements is also not useful because each Chapter UID would need to be in one of the Chapter Edition UID. That would be the same as not using the list of TagEditionUID at all. The following table shows the allowed combinations between lists of Tag UID elements: +============+================+=========+=========+================+ | UID | Track | Edition | Chapter | Attachment | | elements | | | | | +============+================+=========+=========+================+ | Track | YES | YES | YES | with matching | | | | | | AttachmentLink | +------------+----------------+---------+---------+----------------+ | Edition | YES | YES | NO | YES | +------------+----------------+---------+---------+----------------+ | Chapter | YES | NO | YES | NO | +------------+----------------+---------+---------+----------------+ | Attachment | with matching | YES | NO | YES | | | AttachmentLink | | | | +------------+----------------+---------+---------+----------------+ Table 3: Tag UID elements allowed combinations Here is an example of a Tag applying to a single track and a single chapter. It represents the composer of the music in a part of a movie. The file may contain a second audio track with audio commentary not including that music, so we only tag the track with the music. * Targets - TargetTypeValue = 30 - TagTrackUID = 123 - TagChapterUID = 987654321 * COMPOSER = "Jane Smith" This corresponds to this layout of EBML elements: Lhomme, et al. Expires 4 August 2026 [Page 18] Internet-Draft Matroska Tags January 2026 30 123 67890 COMPOSER Jane Smith 4. Assigned Tags The following is the initial list of assigned Matroska Tags. As stated in Section 3.1 it is better to use assigned tags as much as possible, otherwise compatibility will be compromised. If you find that there is a Tag missing that you would like to use, then please contact the persons mentioned in the IANA Matroska Tags Registry for its inclusion; see Section 6.1. 4.1. Nesting Information Nesting Information tags are tags that usually contain any other tags. Lhomme, et al. Expires 4 August 2026 [Page 19] Internet-Draft Matroska Tags January 2026 +==========+========+=========================================+ | Tag Name | Type | Description | +==========+========+=========================================+ | ORIGINAL | nested | A special tag that is meant to have | | | | other tags inside (using nested tags) | | | | to describe the original work of art | | | | that this item is based on. | +----------+--------+-----------------------------------------+ | SAMPLE | nested | A tag that contains other tags to | | | | describe a sample used in the targeted | | | | item originally found in another work | | | | of art. | +----------+--------+-----------------------------------------+ | COUNTRY | UTF-8 | The name of the country that is meant | | | | to have other tags inside (using nested | | | | tags) with country specific information | | | | about the item, using the Country Code | | | | format defined in Section 3.2.2.3. | +----------+--------+-----------------------------------------+ Table 4: Nesting Information tags 4.2. Organization Information All tags in this section express hierarchy defined in Section 3.3.1. +=============+=======+=============================================+ | Tag Name | Type | Description | +=============+=======+=============================================+ | TOTAL_PARTS | UTF-8 | Total number of parts defined at the first | | | | lower level. (e.g., if TargetTypeValue is | | | | "50" (TargetType = "ALBUM"), the total | | | | number of tracks of an audio CD). | +-------------+-------+---------------------------------------------+ | PART_NUMBER | UTF-8 | Index of the current part relative to | | | | parts of the same level, starting at 1. | | | | (e.g., if TargetTypeValue is "30" | | | | (TargetType = "TRACK"), the track number | | | | of an audio CD). | +-------------+-------+---------------------------------------------+ | PART_OFFSET | UTF-8 | A number to add to "PART_NUMBER", when the | | | | parts at that level don't start at 1 | | | | (e.g., if TargetTypeValue is "30" | | | | (TargetType = "TRACK"), the track number | | | | of the second audio CD). | +-------------+-------+---------------------------------------------+ Table 5: Organization Information tags Lhomme, et al. Expires 4 August 2026 [Page 20] Internet-Draft Matroska Tags January 2026 4.3. Titles +==========+=======+=======================================+ | Tag Name | Type | Description | +==========+=======+=======================================+ | TITLE | UTF-8 | The title of this item. For example, | | | | for music you might label this "Canon | | | | in D", or for video's audio track you | | | | might use "English 5.1" This is akin | | | | to the "TIT2" tag in [ID3v2.3] when | | | | the TargetTypeValue is 30 (TRACK). | +----------+-------+---------------------------------------+ | SUBTITLE | UTF-8 | Sub Title of the entity. This is | | | | akin to the "TIT3" tag in [ID3v2.3] | | | | when the TargetTypeValue is 30 | | | | (TRACK). | +----------+-------+---------------------------------------+ Table 6: Titles tags 4.4. Nested Information Nested Information tags are tags providing information about their parent tags. Lhomme, et al. Expires 4 August 2026 [Page 21] Internet-Draft Matroska Tags January 2026 +=============+=======+=========================================+ | Tag Name | Type | Description | +=============+=======+=========================================+ | URL | UTF-8 | URL corresponding to the tag it is | | | | included in, using the format defined | | | | in [RFC3986]. | +-------------+-------+-----------------------------------------+ | SORT_WITH | UTF-8 | A child SimpleTag element to indicate | | | | what alternative value the parent | | | | SimpleTag element can have to be sorted | | | | -- for example, "Band" instead of "The | | | | Band". Or "Doe John" and "Doe John H." | | | | (no comma needed). | +-------------+-------+-----------------------------------------+ | INSTRUMENTS | UTF-8 | The instruments that are being used/ | | | | played, separated by a comma. It MUST | | | | be a child of another tag, including | | | | the following: "ARTIST", | | | | "LEAD_PERFORMER", or "ACCOMPANIMENT". | +-------------+-------+-----------------------------------------+ | EMAIL | UTF-8 | Email corresponding to the tag it is | | | | included in, using the "Addr-Spec" | | | | format defined in Section 3.4.1 of | | | | [RFC5322]. | +-------------+-------+-----------------------------------------+ | ADDRESS | UTF-8 | The physical address of the entity. | | | | The address MAY include a country code. | | | | If a country code is included, it is | | | | RECOMMENDED to use the Country Code | | | | format defined in Section 3.2.2.3. It | | | | can be useful for a recording label. | +-------------+-------+-----------------------------------------+ | FAX | UTF-8 | The fax number corresponding to the tag | | | | it is included in. It can be useful | | | | for a recording label. | +-------------+-------+-----------------------------------------+ | PHONE | UTF-8 | The phone number corresponding to the | | | | tag it is included in. It can be | | | | useful for a recording label. | +-------------+-------+-----------------------------------------+ Table 7: Nested Information tags Lhomme, et al. Expires 4 August 2026 [Page 22] Internet-Draft Matroska Tags January 2026 4.5. Entities +=========================+=======+===============================+ | Tag Name | Type | Description | +=========================+=======+===============================+ | ARTIST | UTF-8 | A person or band/collective | | | | generally considered | | | | responsible for the work. | | | | This is akin to the "TPE1" | | | | tag in [ID3v2.3] when the | | | | TargetTypeValue is 30 | | | | (TRACK). | +-------------------------+-------+-------------------------------+ | LEAD_PERFORMER | UTF-8 | Lead Performer/Soloist(s). | | | | This can sometimes be the | | | | same as "ARTIST". This is | | | | akin to the "TPE1" tag in | | | | [ID3v2.3] when the | | | | TargetTypeValue is 30 | | | | (TRACK). | +-------------------------+-------+-------------------------------+ | ACCOMPANIMENT | UTF-8 | Band/orchestra/accompaniment/ | | | | musician. This is akin to | | | | the "TPE2" tag in [ID3v2.3] | | | | when the TargetTypeValue is | | | | 30 (TRACK). | +-------------------------+-------+-------------------------------+ | COMPOSER | UTF-8 | The name of one composer of | | | | this item. This is akin to | | | | the "TCOM" tag in [ID3v2.3] | | | | when the TargetTypeValue is | | | | 30 (TRACK). | +-------------------------+-------+-------------------------------+ | ARRANGER | UTF-8 | The name of a person who | | | | arranged the piece (e.g., | | | | Ravel). | +-------------------------+-------+-------------------------------+ | LYRICS | UTF-8 | The lyrics corresponding to a | | | | song, in case audio | | | | synchronization is not known | | | | or as a duplicate of a | | | | subtitle track. Editing this | | | | value, when it is a duplicate | | | | of a subtitle track, SHOULD | | | | also result in editing the | | | | subtitle track for more | | | | consistency, and vice versa. | +-------------------------+-------+-------------------------------+ Lhomme, et al. Expires 4 August 2026 [Page 23] Internet-Draft Matroska Tags January 2026 | LYRICIST | UTF-8 | The name of a person who | | | | wrote the lyrics for a | | | | musical item. This is akin | | | | to the "TEXT" tag in | | | | [ID3v2.3] when the | | | | TargetTypeValue is 30 | | | | (TRACK). | +-------------------------+-------+-------------------------------+ | CONDUCTOR | UTF-8 | Conductor/performer | | | | refinement. This is akin to | | | | the "TPE3" tag in [ID3v2.3] | | | | when the TargetTypeValue is | | | | 30 (TRACK). | +-------------------------+-------+-------------------------------+ | DIRECTOR | UTF-8 | The name of a director of a | | | | movie. This is akin to the | | | | "IART" tag [RIFF.tags]. | +-------------------------+-------+-------------------------------+ | ASSISTANT_DIRECTOR | UTF-8 | The name of the assistant | | | | director. | +-------------------------+-------+-------------------------------+ | DIRECTOR_OF_PHOTOGRAPHY | UTF-8 | The name of the director of | | | | photography, also known as | | | | cinematographer. This is | | | | akin to the "ICNM" tag in | | | | [RIFF.tags]. | +-------------------------+-------+-------------------------------+ | SOUND_ENGINEER | UTF-8 | The name of the sound | | | | engineer or sound recordist. | +-------------------------+-------+-------------------------------+ | ART_DIRECTOR | UTF-8 | The person who oversees the | | | | artists and craftspeople who | | | | build the sets. | +-------------------------+-------+-------------------------------+ | PRODUCTION_DESIGNER | UTF-8 | Artist responsible for | | | | designing the overall visual | | | | appearance of a movie. | +-------------------------+-------+-------------------------------+ | CHOREGRAPHER | UTF-8 | The name of the | | | | choreographer. | +-------------------------+-------+-------------------------------+ | COSTUME_DESIGNER | UTF-8 | The name of the costume | | | | designer. | +-------------------------+-------+-------------------------------+ | ACTOR | UTF-8 | An actor or actress playing a | | | | role in this movie. This is | | | | the person's real name, not | | | | the character's name the | Lhomme, et al. Expires 4 August 2026 [Page 24] Internet-Draft Matroska Tags January 2026 | | | person is playing. | +-------------------------+-------+-------------------------------+ | CHARACTER | UTF-8 | The name of the character an | | | | actor or actress plays in | | | | this movie. This SHOULD be a | | | | sub-tag of an ACTOR tag in | | | | order to not cause | | | | ambiguities. | +-------------------------+-------+-------------------------------+ | WRITTEN_BY | UTF-8 | The author of the story or | | | | script (used for movies and | | | | TV shows). | +-------------------------+-------+-------------------------------+ | SCREENPLAY_BY | UTF-8 | The author of the screenplay | | | | or scenario (used for movies | | | | and TV shows). | +-------------------------+-------+-------------------------------+ | EDITED_BY | UTF-8 | The name of a film editor for | | | | a movie. This is akin to the | | | | "IEDT" tag in [RIFF.tags]. | +-------------------------+-------+-------------------------------+ | PRODUCER | UTF-8 | The name of a producer for a | | | | song/movie. This is akin to | | | | the "IPRO" tag in | | | | [RIFF.tags]. | +-------------------------+-------+-------------------------------+ | COPRODUCER | UTF-8 | The name of a co-producer. | +-------------------------+-------+-------------------------------+ | EXECUTIVE_PRODUCER | UTF-8 | The name of an executive | | | | producer. | +-------------------------+-------+-------------------------------+ | DISTRIBUTED_BY | UTF-8 | The name of a company | | | | distributing the content. | | | | This is akin to the "IDST" | | | | tag in [RIFF.tags]. | +-------------------------+-------+-------------------------------+ | MASTERED_BY | UTF-8 | The engineer who mastered the | | | | content for a physical medium | | | | or for digital distribution. | +-------------------------+-------+-------------------------------+ | ENCODED_BY | UTF-8 | This is akin to the "TENC" | | | | tag in [ID3v2.3]. | +-------------------------+-------+-------------------------------+ | MIXED_BY | UTF-8 | DJ mix by the artist | | | | specified. | +-------------------------+-------+-------------------------------+ | REMIXED_BY | UTF-8 | Interpreted, remixed, or | | | | otherwise modified by. This | Lhomme, et al. Expires 4 August 2026 [Page 25] Internet-Draft Matroska Tags January 2026 | | | is akin to the "TPE4" tag in | | | | [ID3v2.3] when the | | | | TargetTypeValue is 30 | | | | (TRACK). | +-------------------------+-------+-------------------------------+ | PRODUCTION_STUDIO | UTF-8 | The name of a physical studio | | | | where the content was | | | | recorded. This is akin to | | | | the "ISTD" tag in | | | | [RIFF.tags]. | +-------------------------+-------+-------------------------------+ | THANKS_TO | UTF-8 | A very general tag for | | | | everyone else that wants to | | | | be listed. | +-------------------------+-------+-------------------------------+ | PUBLISHER | UTF-8 | This is akin to the "TPUB" | | | | tag in [ID3v2.3] when the | | | | TargetTypeValue is 30 | | | | (TRACK). | +-------------------------+-------+-------------------------------+ | LABEL | UTF-8 | The record label or imprint | | | | on the disc. | +-------------------------+-------+-------------------------------+ Table 8: Entities tags 4.6. Search and Classification +=====================+=======+=====================================+ | Tag Name | Type | Description | +=====================+=======+=====================================+ | GENRE | UTF-8 | The main genre (classical, | | | | ambient-house, synthpop, sci- | | | | fi, drama, etc.). The format | | | | follows the "TCON" tag in | | | | [ID3v2.3] when the | | | | TargetTypeValue is 30 (TRACK). | +---------------------+-------+-------------------------------------+ | MOOD | UTF-8 | Intended to reflect the mood of | | | | the item with a few keywords | | | | (e.g., "Romantic", "Sad" or | | | | "Uplifting"). The format | | | | follows that of the "TMOO" tag | | | | in [ID3v2.4] when the | | | | TargetTypeValue is 30 (TRACK). | +---------------------+-------+-------------------------------------+ | ORIGINAL_MEDIA_TYPE | UTF-8 | Describes the original type of | | | | the media, such as, "DVD", | Lhomme, et al. Expires 4 August 2026 [Page 26] Internet-Draft Matroska Tags January 2026 | | | "CD", "computer image," | | | | "drawing," "lithograph," and so | | | | forth. This is akin to the | | | | "TMED" tag in [ID3v2.4]. | +---------------------+-------+-------------------------------------+ | CONTENT_TYPE | UTF-8 | The type of the item (e.g., | | | | Documentary, Feature Film, | | | | Cartoon, Music Video, Music, | | | | Sound FX). | +---------------------+-------+-------------------------------------+ | SUBJECT | UTF-8 | Describes the topic of the | | | | file, such as "Aerial view of | | | | Seattle." | +---------------------+-------+-------------------------------------+ | DESCRIPTION | UTF-8 | A short description of the | | | | content, such as "Two birds | | | | flying." | +---------------------+-------+-------------------------------------+ | KEYWORDS | UTF-8 | Keywords to the item separated | | | | by a comma, used for searching. | +---------------------+-------+-------------------------------------+ | SUMMARY | UTF-8 | A plot outline or a summary of | | | | the story. | +---------------------+-------+-------------------------------------+ | SYNOPSIS | UTF-8 | A description of the story line | | | | of the item. | +---------------------+-------+-------------------------------------+ | INITIAL_KEY | UTF-8 | The initial key that a musical | | | | track starts in. The format is | | | | identical to "TKEY" tag in | | | | [ID3v2.3] when the | | | | TargetTypeValue is 30 (TRACK). | +---------------------+-------+-------------------------------------+ | PERIOD | UTF-8 | Describes the period that the | | | | piece is from or about. For | | | | example, "Renaissance". | +---------------------+-------+-------------------------------------+ | LAW_RATING | UTF-8 | Depending on the "COUNTRY" it | | | | is the format of the rating of | | | | a movie (P, R, X in the USA, an | | | | age in other countries or a URI | | | | defining a logo). | +---------------------+-------+-------------------------------------+ Table 9: Search and Classification tags Lhomme, et al. Expires 4 August 2026 [Page 27] Internet-Draft Matroska Tags January 2026 4.7. Temporal Information All tags in this section use the Date format defined in Section 3.2.2.1. +================+=======+========================================+ | Tag Name | Type | Description | +================+=======+========================================+ | DATE_RELEASED | UTF-8 | The time that the item was originally | | | | released. This is akin to the "TDRL" | | | | tag in [ID3v2.4] when the | | | | TargetTypeValue is 30 (TRACK). | +----------------+-------+----------------------------------------+ | DATE_RECORDED | UTF-8 | The time that the recording began. | | | | This is akin to the "TDRC" tag in | | | | [ID3v2.4] when the TargetTypeValue is | | | | 30 (TRACK). | +----------------+-------+----------------------------------------+ | DATE_ENCODED | UTF-8 | The time that the encoding of this | | | | item was completed began. This is | | | | akin to the "TDEN" tag in [ID3v2.4] | | | | when the TargetTypeValue is 30 | | | | (TRACK). | +----------------+-------+----------------------------------------+ | DATE_TAGGED | UTF-8 | The time that the tags were done for | | | | this item. This is akin to the "TDTG" | | | | tag in [ID3v2.4] when the | | | | TargetTypeValue is 30 (TRACK). | +----------------+-------+----------------------------------------+ | DATE_DIGITIZED | UTF-8 | The time that the item was transferred | | | | to a digital medium. This is akin to | | | | the "IDIT" tag in [RIFF.tags]. | +----------------+-------+----------------------------------------+ | DATE_WRITTEN | UTF-8 | The time that the writing of the | | | | music/script began. | +----------------+-------+----------------------------------------+ | DATE_PURCHASED | UTF-8 | Information on when the file was | | | | purchased; see also Section 4.12 on | | | | purchase tags. | +----------------+-------+----------------------------------------+ | DATE_STARTED | UTF-8 | When the information of the parent | | | | SimpleTag element starts being valid. | | | | The information of the parent | | | | SimpleTag element is only valid | | | | between this date and the "DATE_ENDED" | | | | date of the same level. The | | | | "DATE_ENDED" is OPTIONAL. If empty or | | | | omitted the end date is unknown. | Lhomme, et al. Expires 4 August 2026 [Page 28] Internet-Draft Matroska Tags January 2026 +----------------+-------+----------------------------------------+ | DATE_ENDED | UTF-8 | When the information is not valid | | | | anymore. The information of the | | | | parent SimpleTag element is only valid | | | | between the "DATE_STARTED" date of the | | | | same level and this date. The | | | | "DATE_STARTED" is OPTIONAL. If empty | | | | or omitted the start date is unknown. | +----------------+-------+----------------------------------------+ Table 10: Temporal Information tags 4.8. Spatial Information +======================+=======+===================================+ | Tag Name | Type | Description | +======================+=======+===================================+ | RECORDING_LOCATION | UTF-8 | The location where the item was | | | | recorded, using the Country Code | | | | format defined in | | | | Section 3.2.2.3. This code is | | | | followed by a comma, then more | | | | detailed information such as | | | | state/province, another comma, | | | | and then city. For example, "US, | | | | Texas, Austin". This will allow | | | | for easy sorting. It is okay to | | | | only store the country, or the | | | | country and the state/province. | | | | More detailed information can be | | | | added after the city through the | | | | use of additional commas. In | | | | cases where the province/state is | | | | unknown, but you want to store | | | | the city, simply leave a space | | | | between the two commas. For | | | | example, "US, , Austin". | +----------------------+-------+-----------------------------------+ | COMPOSITION_LOCATION | UTF-8 | Location that the item was | | | | originally designed/written, | | | | using the Country Code format | | | | defined in Section 3.2.2.3. This | | | | code is followed by a comma, then | | | | more detailed information such as | | | | state/province, another comma, | | | | and then city. For example, "US, | | | | Texas, Austin". This will allow | | | | for easy sorting. It is okay to | Lhomme, et al. Expires 4 August 2026 [Page 29] Internet-Draft Matroska Tags January 2026 | | | only store the country, or the | | | | country and the state/province. | | | | More detailed information can be | | | | added after the city through the | | | | use of additional commas. In | | | | cases where the province/state is | | | | unknown, but you want to store | | | | the city, simply leave a space | | | | between the two commas. For | | | | example, "US, , Austin". | +----------------------+-------+-----------------------------------+ | COMPOSER_NATIONALITY | UTF-8 | Nationality of the main composer | | | | of the item, mostly for classical | | | | music, using the Country Code | | | | format defined in | | | | Section 3.2.2.3. | +----------------------+-------+-----------------------------------+ Table 11: Spatial Information tags 4.9. User Information All tags in this section are personal to the user of these files. +==============+=======+============================================+ | Tag Name | Type | Description | +==============+=======+============================================+ | COMMENT | UTF-8 | Any comment related to the content. | +--------------+-------+--------------------------------------------+ | PLAY_COUNTER | UTF-8 | The number of times the item has | | | | been played. | +--------------+-------+--------------------------------------------+ | RATING | UTF-8 | A numeric value defining how much a | | | | person likes the song/movie. The | | | | number is between 0 and 5, stored | | | | using the Float number defined in | | | | Section 3.2.2.2 (e.g., 2.7), 5(.0) | | | | being the highest possible rating. | | | | Other rating systems with different | | | | ranges will have to be scaled. | +--------------+-------+--------------------------------------------+ Table 12: User Information tags Lhomme, et al. Expires 4 August 2026 [Page 30] Internet-Draft Matroska Tags January 2026 4.10. Technical Information These tags represent values that could be parsed to handle the playback better. For historical reasons they are usually stored as strings but a stricter binary format is RECOMMENDED for new tags. +=================================+========+========================+ | Tag Name | Type | Description | +=================================+========+========================+ | ENCODER | UTF-8 | The software or | | | | hardware used to | | | | encode this item. | | | | ("LAME" or "XviD") | +---------------------------------+--------+------------------------+ | ENCODER_SETTINGS | UTF-8 | A list of the | | | | settings used for | | | | encoding this item. | | | | No specific format. | +---------------------------------+--------+------------------------+ | BPS | UTF-8 | The average bits per | | | | second of the | | | | specified item stored | | | | using the Float | | | | number defined in | | | | Section 3.2.2.2. | | | | This is only the data | | | | in the Block(s), and | | | | excludes headers and | | | | any container | | | | overhead. | +---------------------------------+--------+------------------------+ | FPS | UTF-8 | The average frames | | | | per second of the | | | | specified item. This | | | | is typically the | | | | average number of | | | | Blocks per second | | | | stored using the | | | | Float number defined | | | | in Section 3.2.2.2. | | | | In the event that | | | | lacing is used, each | | | | laced chunk is to be | | | | counted as a separate | | | | frame. | +---------------------------------+--------+------------------------+ | BPM | UTF-8 | Average number of | | | | beats per minute in | Lhomme, et al. Expires 4 August 2026 [Page 31] Internet-Draft Matroska Tags January 2026 | | | the complete target | | | | (e.g., a chapter) | | | | stored using the | | | | Float number defined | | | | in Section 3.2.2.2. | +---------------------------------+--------+------------------------+ | MEASURE | UTF-8 | In music, a measure | | | | is a unit of time in | | | | Western music like | | | | "4/4". It represents | | | | a regular grouping of | | | | beats, a meter, as | | | | indicated in musical | | | | notation by the time | | | | signature. The | | | | majority of the | | | | contemporary rock and | | | | pop music you hear on | | | | the radio these days | | | | is written in the 4/4 | | | | time signature. | +---------------------------------+--------+------------------------+ | TUNING | UTF-8 | It is saved as a | | | | frequency in hertz to | | | | allow near-perfect | | | | tuning of instruments | | | | to the same tone as | | | | the musical piece | | | | (e.g., "441.34" in | | | | Hertz). The value is | | | | stored using the | | | | Float number defined | | | | in Section 3.2.2.2. | +---------------------------------+--------+------------------------+ | REPLAYGAIN_GAIN | UTF-8 | The gain to apply to | | | | reach 89 dB SPL | | | | (Sound Pressure Level | | | | in decibels) on | | | | playback. The value | | | | is computed according | | | | to the [ReplayGain] | | | | standard. The value | | | | in decibels (dB) is | | | | stored as a string | | | | (e.g., "-0.42 dB"), | | | | using the Float | | | | number defined in | | | | Section 3.2.2.2. The | Lhomme, et al. Expires 4 August 2026 [Page 32] Internet-Draft Matroska Tags January 2026 | | | decibel unit is | | | | OPTIONAL. There MAY | | | | be a space between | | | | the number and the | | | | decibel unit. Note | | | | that ReplayGain | | | | information can be | | | | found at all | | | | TargetType levels | | | | (track, album, etc.). | +---------------------------------+--------+------------------------+ | REPLAYGAIN_PEAK | UTF-8 | The maximum absolute | | | | peak amplitude of the | | | | item. The value is | | | | computed according to | | | | the [ReplayGain] | | | | standard. The value | | | | is a normalized | | | | absolute sample value | | | | of the target audio, | | | | using the Float | | | | number defined in | | | | Section 3.2.2.2 | | | | (e.g., "1.0129"). | | | | Note that ReplayGain | | | | information can be | | | | found at all | | | | TargetType levels | | | | (track, album, etc.). | +---------------------------------+--------+------------------------+ | EBU_R128_LOUDNESS | binary | EBU R 128 Loudness. | | | | The value is the | | | | Loudness relative to | | | | nominal full scale in | | | | LUFS (Loudness Units | | | | Full Scale) | | | | normalized to a | | | | Target Level of -23.0 | | | | LUFS as defined in | | | | [EBU-R.128]. This | | | | value is stored as a | | | | floating-point number | | | | in the 32-bit and | | | | 64-bit binary | | | | interchange format, | | | | as defined in | | | | [IEEE.754]. It is | | | | similar to a EBML | Lhomme, et al. Expires 4 August 2026 [Page 33] Internet-Draft Matroska Tags January 2026 | | | floating number value | | | | Section 7.3 of | | | | [RFC8794]. | +---------------------------------+--------+------------------------+ | EBU_R128_MAX_TRUE_PEAK | binary | EBU R 128 Maximum | | | | True Peak Level. | | | | This corresponds to | | | | the maximum value of | | | | the audio signal | | | | waveform of a | | | | programme in the | | | | continuous time | | | | domain, measured in | | | | dB True Peak (dBTP), | | | | as defined in | | | | [EBU-R.128]. This | | | | value is stored as a | | | | floating-point number | | | | in the 32-bit and | | | | 64-bit binary | | | | interchange format, | | | | as defined in | | | | [IEEE.754]. It is | | | | similar to a EBML | | | | floating number value | | | | Section 7.3 of | | | | [RFC8794]. | +---------------------------------+--------+------------------------+ | EBU_R128_LOUDNESS_RANGE | binary | EBU R 128 Loudness | | | | Range, measures the | | | | variation in a time- | | | | varying loudness | | | | measurement, in LU | | | | (Loudness Units) as | | | | defined in | | | | [EBU-TECH.3342]. | | | | This value is stored | | | | as a floating-point | | | | number in the 32-bit | | | | and 64-bit binary | | | | interchange format, | | | | as defined in | | | | [IEEE.754]. It is | | | | similar to a EBML | | | | floating number value | | | | Section 7.3 of | | | | [RFC8794]. | +---------------------------------+--------+------------------------+ Lhomme, et al. Expires 4 August 2026 [Page 34] Internet-Draft Matroska Tags January 2026 | EBU_R128_MAX_MOMENTARY_LOUDNESS | binary | EBU R 128 Maximum | | | | Momentary Loudness, | | | | measures the | | | | variation of loudness | | | | on a 0.4 s sliding | | | | rectangular window, | | | | in LUFS (Loudness | | | | Units Full Scale) as | | | | defined in | | | | [EBU-TECH.3341]. | | | | This value is stored | | | | as a floating-point | | | | number in the 32-bit | | | | and 64-bit binary | | | | interchange format, | | | | as defined in | | | | [IEEE.754]. It is | | | | similar to a EBML | | | | floating number value | | | | Section 7.3 of | | | | [RFC8794]. | +---------------------------------+--------+------------------------+ | EBU_R128_MAX_SHORT_LOUDNESS | binary | EBU R 128 Maximum | | | | Short-Term Loudness, | | | | measures the | | | | variation of loudness | | | | on a 3 s sliding | | | | rectangular window, | | | | in LUFS (Loudness | | | | Units Full Scale) as | | | | defined in | | | | [EBU-TECH.3341]. | | | | This value is stored | | | | as a floating-point | | | | number in the 32-bit | | | | and 64-bit binary | | | | interchange format, | | | | as defined in | | | | [IEEE.754]. It is | | | | similar to a EBML | | | | floating number value | | | | Section 7.3 of | | | | [RFC8794]. | +---------------------------------+--------+------------------------+ Table 13: Technical Information tags Lhomme, et al. Expires 4 August 2026 [Page 35] Internet-Draft Matroska Tags January 2026 4.11. External Identifiers +================+========+=====================================+ | Tag Name | Type | Description | +================+========+=====================================+ | ISRC | UTF-8 | The International Standard | | | | Recording Code [ISRC], excluding | | | | the "ISRC" prefix and including | | | | hyphens. | +----------------+--------+-------------------------------------+ | MCDI | binary | This is a binary dump of the TOC of | | | | the CD-ROM that this item was taken | | | | from. This holds the same | | | | information as the "MCDI" in | | | | [ID3v2.3] when the TargetTypeValue | | | | is 50 (ALBUM). | +----------------+--------+-------------------------------------+ | ISBN | UTF-8 | International Standard Book Number | | | | [ISBN]. | +----------------+--------+-------------------------------------+ | BARCODE | UTF-8 | European Article Numbering EAN-13 | | | | barcode defined in [GS1] General | | | | Specifications. | +----------------+--------+-------------------------------------+ | CATALOG_NUMBER | UTF-8 | A label-specific string used to | | | | identify the release -- for | | | | example, TIC 01. | +----------------+--------+-------------------------------------+ | LABEL_CODE | UTF-8 | A 4-digit or 5-digit number to | | | | identify the record label, | | | | typically printed as (LC) xxxx or | | | | (LC) 0xxxx on CDs medias or covers | | | | (only the number is stored). | +----------------+--------+-------------------------------------+ | LCCN | UTF-8 | United States of America Library of | | | | Congress Control Number [LCCN]. | +----------------+--------+-------------------------------------+ | IMDB | UTF-8 | Internet Movie Database [IMDb] | | | | title identifier. "tt" followed by | | | | at least 7 digits for Movies, TV | | | | Shows, and Episodes. | +----------------+--------+-------------------------------------+ | TMDB | UTF-8 | The Movie DB "movie_id" or "tv_id" | | | | identifier for movies/TV shows | | | | [MovieDB]. The variable length | | | | digits string MUST be prefixed with | | | | either "movie/" or "tv/". | +----------------+--------+-------------------------------------+ Lhomme, et al. Expires 4 August 2026 [Page 36] Internet-Draft Matroska Tags January 2026 | TVDB | UTF-8 | The TV Database "Series ID" or | | | | "Episode ID" identifier for TV | | | | shows [TheTVDB]. Variable length | | | | all-digits string identifying a TV | | | | Show to use with the "series/{id}" | | | | API. | +----------------+--------+-------------------------------------+ | TVDB2 | UTF-8 | The TV Database [TheTVDB] tag which | | | | can include movies. The variable | | | | length digits string representing a | | | | "Series ID", "Episode ID" or "Movie | | | | ID" identifier MUST be prefixed | | | | with "series/", "episodes/", or | | | | "movies/", respectively. | +----------------+--------+-------------------------------------+ Table 14: External Identifiers tags 4.12. Commercial +===================+=======+=======================================+ | Tag Name | Type | Description | +===================+=======+=======================================+ | PURCHASE_ITEM | UTF-8 | URL to purchase this file using the | | | | URL format defined in [RFC3986]. | | | | This is akin to the "WPAY" tag in | | | | [ID3v2.3] when the TargetTypeValue | | | | is 30 (TRACK). | +-------------------+-------+---------------------------------------+ | PURCHASE_INFO | UTF-8 | Information on where to purchase | | | | this album using the URL format | | | | defined in [RFC3986]. This is akin | | | | to the "WCOM" tag in [ID3v2.3] when | | | | the TargetTypeValue is 30 (TRACK). | +-------------------+-------+---------------------------------------+ | PURCHASE_OWNER | UTF-8 | Information on the person who | | | | purchased the file. This is akin | | | | to the "TOWN" tag in [ID3v2.3] when | | | | the TargetTypeValue is 30 (TRACK). | +-------------------+-------+---------------------------------------+ | PURCHASE_PRICE | UTF-8 | The amount paid for entity, using | | | | the Float number defined in | | | | Section 3.2.2.2. The currency is | | | | not included. For instance, you | | | | would store "15.59" instead of | | | | "$15.59USD". | +-------------------+-------+---------------------------------------+ | PURCHASE_CURRENCY | UTF-8 | The currency type used to pay for | Lhomme, et al. Expires 4 August 2026 [Page 37] Internet-Draft Matroska Tags January 2026 | | | the entity. Use [ISO4217] for the | | | | 3 letter alphabetic code. | +-------------------+-------+---------------------------------------+ Table 15: Commercial tags 4.13. Legal +======================+=======+==================================+ | Tag Name | Type | Description | +======================+=======+==================================+ | COPYRIGHT | UTF-8 | The copyright information as per | | | | the copyright holder. This is | | | | akin to the "TCOP" tag in | | | | [ID3v2.3] when the | | | | TargetTypeValue is 30 (TRACK). | +----------------------+-------+----------------------------------+ | PRODUCTION_COPYRIGHT | UTF-8 | The copyright information as per | | | | the production copyright holder. | | | | This is akin to the "TPRO" tag | | | | in [ID3v2.4] when the | | | | TargetTypeValue is 30 (TRACK). | +----------------------+-------+----------------------------------+ | LICENSE | UTF-8 | The license applied to the | | | | content (e.g., Creative Commons | | | | variants). | +----------------------+-------+----------------------------------+ | TERMS_OF_USE | UTF-8 | The terms of use for this item. | | | | This is akin to the "USER" tag | | | | in [ID3v2.3]. | +----------------------+-------+----------------------------------+ Table 16: Legal tags 5. Security Considerations This document inherits security considerations from the EBML [RFC8794] and Matroska [RFC9559] documents. Tag values can be either TagString or TagBinary blobs. In both cases issues can happen if the parsing of the data fails. Most of the time strings are kept as-is and don't pose a security issue, apart from invalid UTF-8 values. Implementations MUST validate TagString inputs for UTF-8 correctness and reasonable length before use, in accordance with the security considerations in Section 10 of [RFC3629]. Lhomme, et al. Expires 4 August 2026 [Page 38] Internet-Draft Matroska Tags January 2026 String tags that are parsed (such as "REPLAYGAIN_GAIN" or "REPLAYGAIN_PEAK" defined in Section 4.10) or string tags following the rules from Section 3.2.2 or string tags following other strict formats like URLs may cause issues when the string is bogus or in an unexpected format. Binary tags that need to be parsed (such as "MCDI" defined in Section 4.11) may cause issues when the data is bogus or incomplete. Some tags like "URL" (Section 4.4) and "PURCHASE_URL" (Section 4.12) contain a URL. Bogus or altered URLs may direct the user to unwanted places. Due to the nature of nested SimpleTag, it is possible to exhaust the memory of the host app by using very deep nesting. A host app MAY add some limits to the amount of nesting possible to avoid such issues. Some elements found in Section 4.4 and Section 4.9 may contain physical addresses, email, etc. about a person. Care should be taken to ensure not to provide such files to people that ought not have this information when it's not public knowledge. This can be achieved by either removing personal information or by controlling the diffusion of files containing these pieces of information. 6. IANA Considerations 6.1. Matroska Tags Names Registry IANA has created a new registry called the "Matroska Tag Names" registry. To register a new Tag Name in this registry, one needs a Name, a Type, a Change Controller, and an optional Reference to a document describing the Element ID. The Name corresponds to the value stored in the TagName element. A Tag Name MUST only be found once in the IANA registry. Two Tag Names MUST NOT have the same semantic meaning. The Name is written in all latin capital letters, numbers and the underscore character '_' as defined in Section 3.2. The Name MUST NOT start with the underscore character '_'. The Type corresponds to which element will be stored the tag value. There can be 3 values for the Type: * UTF-8: the value of the Tag is stored in TagString, Lhomme, et al. Expires 4 August 2026 [Page 39] Internet-Draft Matroska Tags January 2026 Matroska Tag Names for UTF-8 data are to be allocated according to the "First Come First Served" policy [RFC8126]. * binary: the value of the Tag is stored in TagBinary, Matroska Tag Names for binary data are to be allocated according to the "Specification Required" policy [RFC8126]. The content of the binary data MUST NOT be a single UTF-8 string, in which case the type should be UTF-8. It is RECOMMENDED to not include the size of the binary data at the start of the data as the size is already handled by the element itself. * nested: the tag doesn't contain a value, i.e., neither a TagBinary nor a TagString child element, only SimpleTag child elements inside. Matroska Tag Names for nested tags are to be allocated according to the "Specification Required" policy [RFC8126]. Matroska Tag Names Values found in this document are assigned as initial values as follows: +=================================+==========+================+ | Tag Name | Tag Type | Reference | +=================================+==========+================+ | ORIGINAL | nested | This document, | | | | Section 4.1 | +---------------------------------+----------+----------------+ | SAMPLE | nested | This document, | | | | Section 4.1 | +---------------------------------+----------+----------------+ | COUNTRY | UTF-8 | This document, | | | | Section 4.1 | +---------------------------------+----------+----------------+ | TOTAL_PARTS | UTF-8 | This document, | | | | Section 4.2 | +---------------------------------+----------+----------------+ | PART_NUMBER | UTF-8 | This document, | | | | Section 4.2 | +---------------------------------+----------+----------------+ | PART_OFFSET | UTF-8 | This document, | | | | Section 4.2 | +---------------------------------+----------+----------------+ | TITLE | UTF-8 | This document, | | | | Section 4.3 | +---------------------------------+----------+----------------+ | SUBTITLE | UTF-8 | This document, | | | | Section 4.3 | Lhomme, et al. Expires 4 August 2026 [Page 40] Internet-Draft Matroska Tags January 2026 +---------------------------------+----------+----------------+ | URL | UTF-8 | This document, | | | | Section 4.4 | +---------------------------------+----------+----------------+ | SORT_WITH | UTF-8 | This document, | | | | Section 4.4 | +---------------------------------+----------+----------------+ | INSTRUMENTS | UTF-8 | This document, | | | | Section 4.4 | +---------------------------------+----------+----------------+ | EMAIL | UTF-8 | This document, | | | | Section 4.4 | +---------------------------------+----------+----------------+ | ADDRESS | UTF-8 | This document, | | | | Section 4.4 | +---------------------------------+----------+----------------+ | FAX | UTF-8 | This document, | | | | Section 4.4 | +---------------------------------+----------+----------------+ | PHONE | UTF-8 | This document, | | | | Section 4.4 | +---------------------------------+----------+----------------+ | ARTIST | UTF-8 | This document, | | | | Section 4.5 | +---------------------------------+----------+----------------+ | LEAD_PERFORMER | UTF-8 | This document, | | | | Section 4.5 | +---------------------------------+----------+----------------+ | ACCOMPANIMENT | UTF-8 | This document, | | | | Section 4.5 | +---------------------------------+----------+----------------+ | COMPOSER | UTF-8 | This document, | | | | Section 4.5 | +---------------------------------+----------+----------------+ | ARRANGER | UTF-8 | This document, | | | | Section 4.5 | +---------------------------------+----------+----------------+ | LYRICS | UTF-8 | This document, | | | | Section 4.5 | +---------------------------------+----------+----------------+ | LYRICIST | UTF-8 | This document, | | | | Section 4.5 | +---------------------------------+----------+----------------+ | CONDUCTOR | UTF-8 | This document, | | | | Section 4.5 | +---------------------------------+----------+----------------+ | DIRECTOR | UTF-8 | This document, | | | | Section 4.5 | Lhomme, et al. Expires 4 August 2026 [Page 41] Internet-Draft Matroska Tags January 2026 +---------------------------------+----------+----------------+ | ASSISTANT_DIRECTOR | UTF-8 | This document, | | | | Section 4.5 | +---------------------------------+----------+----------------+ | DIRECTOR_OF_PHOTOGRAPHY | UTF-8 | This document, | | | | Section 4.5 | +---------------------------------+----------+----------------+ | SOUND_ENGINEER | UTF-8 | This document, | | | | Section 4.5 | +---------------------------------+----------+----------------+ | ART_DIRECTOR | UTF-8 | This document, | | | | Section 4.5 | +---------------------------------+----------+----------------+ | PRODUCTION_DESIGNER | UTF-8 | This document, | | | | Section 4.5 | +---------------------------------+----------+----------------+ | CHOREGRAPHER | UTF-8 | This document, | | | | Section 4.5 | +---------------------------------+----------+----------------+ | COSTUME_DESIGNER | UTF-8 | This document, | | | | Section 4.5 | +---------------------------------+----------+----------------+ | ACTOR | UTF-8 | This document, | | | | Section 4.5 | +---------------------------------+----------+----------------+ | CHARACTER | UTF-8 | This document, | | | | Section 4.5 | +---------------------------------+----------+----------------+ | WRITTEN_BY | UTF-8 | This document, | | | | Section 4.5 | +---------------------------------+----------+----------------+ | SCREENPLAY_BY | UTF-8 | This document, | | | | Section 4.5 | +---------------------------------+----------+----------------+ | EDITED_BY | UTF-8 | This document, | | | | Section 4.5 | +---------------------------------+----------+----------------+ | PRODUCER | UTF-8 | This document, | | | | Section 4.5 | +---------------------------------+----------+----------------+ | COPRODUCER | UTF-8 | This document, | | | | Section 4.5 | +---------------------------------+----------+----------------+ | EXECUTIVE_PRODUCER | UTF-8 | This document, | | | | Section 4.5 | +---------------------------------+----------+----------------+ | DISTRIBUTED_BY | UTF-8 | This document, | | | | Section 4.5 | Lhomme, et al. Expires 4 August 2026 [Page 42] Internet-Draft Matroska Tags January 2026 +---------------------------------+----------+----------------+ | MASTERED_BY | UTF-8 | This document, | | | | Section 4.5 | +---------------------------------+----------+----------------+ | ENCODED_BY | UTF-8 | This document, | | | | Section 4.5 | +---------------------------------+----------+----------------+ | MIXED_BY | UTF-8 | This document, | | | | Section 4.5 | +---------------------------------+----------+----------------+ | REMIXED_BY | UTF-8 | This document, | | | | Section 4.5 | +---------------------------------+----------+----------------+ | PRODUCTION_STUDIO | UTF-8 | This document, | | | | Section 4.5 | +---------------------------------+----------+----------------+ | THANKS_TO | UTF-8 | This document, | | | | Section 4.5 | +---------------------------------+----------+----------------+ | PUBLISHER | UTF-8 | This document, | | | | Section 4.5 | +---------------------------------+----------+----------------+ | LABEL | UTF-8 | This document, | | | | Section 4.5 | +---------------------------------+----------+----------------+ | GENRE | UTF-8 | This document, | | | | Section 4.6 | +---------------------------------+----------+----------------+ | MOOD | UTF-8 | This document, | | | | Section 4.6 | +---------------------------------+----------+----------------+ | ORIGINAL_MEDIA_TYPE | UTF-8 | This document, | | | | Section 4.6 | +---------------------------------+----------+----------------+ | CONTENT_TYPE | UTF-8 | This document, | | | | Section 4.6 | +---------------------------------+----------+----------------+ | SUBJECT | UTF-8 | This document, | | | | Section 4.6 | +---------------------------------+----------+----------------+ | DESCRIPTION | UTF-8 | This document, | | | | Section 4.6 | +---------------------------------+----------+----------------+ | KEYWORDS | UTF-8 | This document, | | | | Section 4.6 | +---------------------------------+----------+----------------+ | SUMMARY | UTF-8 | This document, | | | | Section 4.6 | Lhomme, et al. Expires 4 August 2026 [Page 43] Internet-Draft Matroska Tags January 2026 +---------------------------------+----------+----------------+ | SYNOPSIS | UTF-8 | This document, | | | | Section 4.6 | +---------------------------------+----------+----------------+ | INITIAL_KEY | UTF-8 | This document, | | | | Section 4.6 | +---------------------------------+----------+----------------+ | PERIOD | UTF-8 | This document, | | | | Section 4.6 | +---------------------------------+----------+----------------+ | LAW_RATING | UTF-8 | This document, | | | | Section 4.6 | +---------------------------------+----------+----------------+ | DATE_RELEASED | UTF-8 | This document, | | | | Section 4.7 | +---------------------------------+----------+----------------+ | DATE_RECORDED | UTF-8 | This document, | | | | Section 4.7 | +---------------------------------+----------+----------------+ | DATE_ENCODED | UTF-8 | This document, | | | | Section 4.7 | +---------------------------------+----------+----------------+ | DATE_TAGGED | UTF-8 | This document, | | | | Section 4.7 | +---------------------------------+----------+----------------+ | DATE_DIGITIZED | UTF-8 | This document, | | | | Section 4.7 | +---------------------------------+----------+----------------+ | DATE_WRITTEN | UTF-8 | This document, | | | | Section 4.7 | +---------------------------------+----------+----------------+ | DATE_PURCHASED | UTF-8 | This document, | | | | Section 4.7 | +---------------------------------+----------+----------------+ | DATE_STARTED | UTF-8 | This document, | | | | Section 4.7 | +---------------------------------+----------+----------------+ | DATE_ENDED | UTF-8 | This document, | | | | Section 4.7 | +---------------------------------+----------+----------------+ | RECORDING_LOCATION | UTF-8 | This document, | | | | Section 4.8 | +---------------------------------+----------+----------------+ | COMPOSITION_LOCATION | UTF-8 | This document, | | | | Section 4.8 | +---------------------------------+----------+----------------+ | COMPOSER_NATIONALITY | UTF-8 | This document, | | | | Section 4.8 | Lhomme, et al. Expires 4 August 2026 [Page 44] Internet-Draft Matroska Tags January 2026 +---------------------------------+----------+----------------+ | COMMENT | UTF-8 | This document, | | | | Section 4.9 | +---------------------------------+----------+----------------+ | PLAY_COUNTER | UTF-8 | This document, | | | | Section 4.9 | +---------------------------------+----------+----------------+ | RATING | UTF-8 | This document, | | | | Section 4.9 | +---------------------------------+----------+----------------+ | ENCODER | UTF-8 | This document, | | | | Section 4.10 | +---------------------------------+----------+----------------+ | ENCODER_SETTINGS | UTF-8 | This document, | | | | Section 4.10 | +---------------------------------+----------+----------------+ | BPS | UTF-8 | This document, | | | | Section 4.10 | +---------------------------------+----------+----------------+ | FPS | UTF-8 | This document, | | | | Section 4.10 | +---------------------------------+----------+----------------+ | BPM | UTF-8 | This document, | | | | Section 4.10 | +---------------------------------+----------+----------------+ | MEASURE | UTF-8 | This document, | | | | Section 4.10 | +---------------------------------+----------+----------------+ | TUNING | UTF-8 | This document, | | | | Section 4.10 | +---------------------------------+----------+----------------+ | REPLAYGAIN_GAIN | UTF-8 | This document, | | | | Section 4.10 | +---------------------------------+----------+----------------+ | REPLAYGAIN_PEAK | UTF-8 | This document, | | | | Section 4.10 | +---------------------------------+----------+----------------+ | EBU_R128_LOUDNESS | binary | This document, | | | | Section 4.10 | +---------------------------------+----------+----------------+ | EBU_R128_MAX_TRUE_PEAK | binary | This document, | | | | Section 4.10 | +---------------------------------+----------+----------------+ | EBU_R128_LOUDNESS_RANGE | binary | This document, | | | | Section 4.10 | +---------------------------------+----------+----------------+ | EBU_R128_MAX_MOMENTARY_LOUDNESS | binary | This document, | | | | Section 4.10 | Lhomme, et al. Expires 4 August 2026 [Page 45] Internet-Draft Matroska Tags January 2026 +---------------------------------+----------+----------------+ | EBU_R128_MAX_SHORT_LOUDNESS | binary | This document, | | | | Section 4.10 | +---------------------------------+----------+----------------+ | ISRC | UTF-8 | This document, | | | | Section 4.11 | +---------------------------------+----------+----------------+ | MCDI | binary | This document, | | | | Section 4.11 | +---------------------------------+----------+----------------+ | ISBN | UTF-8 | This document, | | | | Section 4.11 | +---------------------------------+----------+----------------+ | BARCODE | UTF-8 | This document, | | | | Section 4.11 | +---------------------------------+----------+----------------+ | CATALOG_NUMBER | UTF-8 | This document, | | | | Section 4.11 | +---------------------------------+----------+----------------+ | LABEL_CODE | UTF-8 | This document, | | | | Section 4.11 | +---------------------------------+----------+----------------+ | LCCN | UTF-8 | This document, | | | | Section 4.11 | +---------------------------------+----------+----------------+ | IMDB | UTF-8 | This document, | | | | Section 4.11 | +---------------------------------+----------+----------------+ | TMDB | UTF-8 | This document, | | | | Section 4.11 | +---------------------------------+----------+----------------+ | TVDB | UTF-8 | This document, | | | | Section 4.11 | +---------------------------------+----------+----------------+ | TVDB2 | UTF-8 | This document, | | | | Section 4.11 | +---------------------------------+----------+----------------+ | PURCHASE_ITEM | UTF-8 | This document, | | | | Section 4.12 | +---------------------------------+----------+----------------+ | PURCHASE_INFO | UTF-8 | This document, | | | | Section 4.12 | +---------------------------------+----------+----------------+ | PURCHASE_OWNER | UTF-8 | This document, | | | | Section 4.12 | +---------------------------------+----------+----------------+ | PURCHASE_PRICE | UTF-8 | This document, | | | | Section 4.12 | Lhomme, et al. Expires 4 August 2026 [Page 46] Internet-Draft Matroska Tags January 2026 +---------------------------------+----------+----------------+ | PURCHASE_CURRENCY | UTF-8 | This document, | | | | Section 4.12 | +---------------------------------+----------+----------------+ | COPYRIGHT | UTF-8 | This document, | | | | Section 4.13 | +---------------------------------+----------+----------------+ | PRODUCTION_COPYRIGHT | UTF-8 | This document, | | | | Section 4.13 | +---------------------------------+----------+----------------+ | LICENSE | UTF-8 | This document, | | | | Section 4.13 | +---------------------------------+----------+----------------+ | TERMS_OF_USE | UTF-8 | This document, | | | | Section 4.13 | +---------------------------------+----------+----------------+ Table 17: Initial Contents of "Matroska Tag Names" Registry 6.2. Guidelines for the Designated Experts Criteria for binary tags include ensuring the data in the TagBinary element are defined in a specification. When possible, i.e., the binary format is not already in use elsewhere, the data should not start with the size of the data to follow, as this size is already part of the TagBinary element. Criteria for nested tags include ensuring that the tag consists of one or more child SimpleTag elements to describe the metadata corresponding to that tag. 7. References 7.1. Normative References [EBU-R.128] "LOUDNESS NORMALISATION AND PERMITTED MAXIMUM LEVEL OF AUDIO SIGNALS", November 2023, . [EBU-TECH.3341] "LOUDNESS METERING: 'EBU MODE' METERING TO SUPPLEMENT EBU R 128 LOUDNESS NORMALIZATION", November 2023, . Lhomme, et al. Expires 4 August 2026 [Page 47] Internet-Draft Matroska Tags January 2026 [EBU-TECH.3342] "LOUDNESS RANGE: A MEASURE TO SUPPLEMENT EBU R 128 LOUDNESS NORMALIZATION", November 2023, . [GS1] "GS1 General Specifications", GS1 20.0, January 2020, . [ID3v2.3] Nilsson, M., Mahoney, D., Ed., and J. Sundstrom, Ed., "ID3 tag version 2.3.0", 3 February 1999, . [ID3v2.4] Nilsson, M., "ID3 tag version 2.4.0 - Native Frames", 1 November 2000, . [IEEE.754] IEEE, "IEEE Standard for Binary Floating-Point Arithmetic", 13 June 2019, . [IMDb] Internet Movie Database, "IMDb data key concepts", . [ISBN] International ISBN Agency, "ISBN Users' Manual", December 2017, . [ISO4217] International Organization for Standardization, "ISO 4217 Currency codes", ISO 4217:2015, August 2015, . [ISRC] International ISRC Registration Authority, "International Standard Recording Code (ISRC) Handbook", IFPI 4th Edition, 2021, . [LCCN] United States Library Of Congress, "Library Of Congress Control Number", October 1999, . [MovieDB] The Movie Database, "The Movie Database API", . [ReplayGain] Robinson, D., "ReplayGain 1.0 specification", 10 July 2001, . Lhomme, et al. Expires 4 August 2026 [Page 48] Internet-Draft Matroska Tags January 2026 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997, . [RFC3629] Yergeau, F., "UTF-8, a transformation format of ISO 10646", STD 63, RFC 3629, DOI 10.17487/RFC3629, November 2003, . [RFC3986] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform Resource Identifier (URI): Generic Syntax", STD 66, RFC 3986, DOI 10.17487/RFC3986, January 2005, . [RFC5234] Crocker, D., Ed. and P. Overell, "Augmented BNF for Syntax Specifications: ABNF", STD 68, RFC 5234, DOI 10.17487/RFC5234, January 2008, . [RFC5322] Resnick, P., Ed., "Internet Message Format", RFC 5322, DOI 10.17487/RFC5322, October 2008, . [RFC5646] Phillips, A., Ed. and M. Davis, Ed., "Tags for Identifying Languages", BCP 47, RFC 5646, DOI 10.17487/RFC5646, September 2009, . [RFC8126] Cotton, M., Leiba, B., and T. Narten, "Guidelines for Writing an IANA Considerations Section in RFCs", BCP 26, RFC 8126, DOI 10.17487/RFC8126, June 2017, . [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, May 2017, . [RFC8794] Lhomme, S., Rice, D., and M. Bunkus, "Extensible Binary Meta Language", RFC 8794, DOI 10.17487/RFC8794, July 2020, . [RFC9559] Lhomme, S., Bunkus, M., and D. Rice, "Matroska Media Container Format Specification", RFC 9559, DOI 10.17487/RFC9559, October 2024, . [TheTVDB] The TVDB, "TVDB API V4", . Lhomme, et al. Expires 4 August 2026 [Page 49] Internet-Draft Matroska Tags January 2026 7.2. Informative References [ISO8601] International Organization for Standardization, "Date and time - Representations for information interchange - Part 1: Basic rules", ISO 8601-1:2019, February 2019, . [RFC3339] Klyne, G. and C. Newman, "Date and Time on the Internet: Timestamps", RFC 3339, DOI 10.17487/RFC3339, July 2002, . [RIFF.tags] Exiftool, "RIFF Tags", . Authors' Addresses Steve Lhomme Email: slhomme@matroska.org Moritz Bunkus Email: moritz@bunkus.org Dave Rice Email: dave@dericed.com Lhomme, et al. Expires 4 August 2026 [Page 50]