Matroska Media Container Tag Specifications
draft-ietf-cellar-tags-06

Document Type Active Internet-Draft (cellar WG)
Authors Steve Lhomme , Moritz Bunkus , Dave Rice 
Last updated 2021-04-12
Stream Internet Engineering Task Force (IETF)
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cellar                                                         S. Lhomme
Internet-Draft                                                          
Intended status: Informational                                 M. Bunkus
Expires: 14 October 2021                                                
                                                                 D. Rice
                                                           12 April 2021

              Matroska Media Container Tag Specifications
                       draft-ietf-cellar-tags-06

Abstract

   This document defines the Matroska 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 14 October 2021.

Copyright Notice

   Copyright (c) 2021 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents (https://trustee.ietf.org/
   license-info) in effect on the date of publication of this document.
   Please review these documents carefully, as they describe your rights
   and restrictions with respect to this document.  Code Components
   extracted from this document must include Simplified BSD License text
   as described in Section 4.e of the Trust Legal Provisions and are
   provided without warranty as described in the Simplified BSD License.

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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Status of this document . . . . . . . . . . . . . . . . . . .   3
   3.  Security Considerations . . . . . . . . . . . . . . . . . . .   3
   4.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   3
   5.  Notation and Conventions  . . . . . . . . . . . . . . . . . .   3
   6.  Tagging . . . . . . . . . . . . . . . . . . . . . . . . . . .   3
     6.1.  Why official tags matter  . . . . . . . . . . . . . . . .   4
     6.2.  Tag Formatting  . . . . . . . . . . . . . . . . . . . . .   4
     6.3.  Target types  . . . . . . . . . . . . . . . . . . . . . .   5
     6.4.  Official tags . . . . . . . . . . . . . . . . . . . . . .   7
     6.5.  Nesting Information . . . . . . . . . . . . . . . . . . .   7
     6.6.  Organization Information  . . . . . . . . . . . . . . . .   8
     6.7.  Titles  . . . . . . . . . . . . . . . . . . . . . . . . .   9
     6.8.  Nested Information  . . . . . . . . . . . . . . . . . . .   9
     6.9.  Entities  . . . . . . . . . . . . . . . . . . . . . . . .  10
     6.10. Search and Classification . . . . . . . . . . . . . . . .  13
     6.11. Temporal Information  . . . . . . . . . . . . . . . . . .  15
     6.12. Spatial Information . . . . . . . . . . . . . . . . . . .  15
     6.13. Personal  . . . . . . . . . . . . . . . . . . . . . . . .  17
     6.14. Technical Information . . . . . . . . . . . . . . . . . .  17
     6.15. Identifiers . . . . . . . . . . . . . . . . . . . . . . .  18
     6.16. Commercial  . . . . . . . . . . . . . . . . . . . . . . .  20
     6.17. Legal . . . . . . . . . . . . . . . . . . . . . . . . . .  20
     6.18. Notes . . . . . . . . . . . . . . . . . . . . . . . . . .  21
   7.  Normative References  . . . . . . . . . . . . . . . . . . . .  21
   8.  Informative References  . . . . . . . . . . . . . . . . . . .  22
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  22

1.  Introduction

   Matroska aims to become THE standard of multimedia container formats.
   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".  It can tag a whole
   "Segment", separate "Track Elements", individual Chapter elements or
   "Attachment Elements".

   While the Matroska tagging framework allows anyone to create their
   own custom tags, it's important to have a common set of values for
   interoperability.  This document intends to define a set of common
   tag names used in Matroska.

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2.  Status of this document

   This document is a work-in-progress specification defining the
   Matroska file format as part of the IETF Cellar working group
   (https://datatracker.ietf.org/wg/cellar/charter/).  It uses basic
   elements and concepts already defined in the Matroska specifications
   defined by this workgroup.

3.  Security Considerations

   "Tag" values can be either strings or binary blobs.  This document
   inherits security considerations from the EBML and Matroska
   documents.

4.  IANA Considerations

   To be determined.

5.  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.

6.  Tagging

   When a Tag is nested within another Tag, the nested Tag becomes an
   attribute of the base tag.  For instance, if you wanted to store the
   dates that a singer used certain addresses for, that singer being the
   lead singer for a track that included multiple bands simultaneously,
   then your tag tree would look something like this:

   *  Targets

      -  TrackUID

   *  BAND

      -  LEADPERFORMER

      -  ADDRESS

         o  DATE

         o  DATEEND

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      -  ADDRESS

         o  DATE

   In this way, it becomes possible to store any Tag as attributes of
   another tag.

   Multiple items SHOULD never be stored as a list in a single
   TagString.  If there is more than one tag of a certain type to be
   stored, then more than one SimpleTag SHOULD be used.

6.1.  Why official tags matter

   There is a debate between people who think all tags SHOULD be free
   and those who think all tags SHOULD be strict.  If you look at this
   page you will realize we are in between.

   Advanced-users application might let you put any tag in your file.
   But for the rest of the applications, they usually give you a basic
   list of tags you can use.  Both have their needs.  But it's usually a
   bad idea to use custom/exotic tags because you will probably be the
   only person to use this information even though everyone else could
   benefit from it.  So hopefully, when someone wants to put information
   in one's file, they will find an official one that fit them and
   hopefully use it ! If it's not in the list, this person can contact
   us any time for addition of such a missing tag.  But it doesn't mean
   it will be accepted... Matroska files are not meant the become a
   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 doesn't make sense in a file.  So we'll treat each request
   carefully.

   We also need an official 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
   wanted meaning so that other apps could understand the same meaning).

6.2.  Tag Formatting

   *  The TagName SHOULD always be written in all capital letters and
      contain no space.

   *  The fields with dates SHOULD have the following format: YYYY-MM-DD
      hh:mm:ss.mss YYYY = Year, MM = Month, DD = Days, HH = Hours, mm =
      Minutes, ss = Seconds, mss = Milliseconds.  To store less
      accuracy, you remove items starting from the right.  To store only
      the year, you would use, "2004".  To store a specific day such as
      May 1st, 2003, you would use "2003-05-01".

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   *  Fields that require a Float SHOULD use the "." mark instead of the
      "," mark.  To display it differently for another local,
      applications SHOULD support auto replacement on display.  Also, a
      thousandths separator SHOULD NOT be used.

   *  For currency amounts, there SHOULD only be a numeric value in the
      Tag. Only numbers, no letters or symbols other than ".".  For
      instance, you would store "15.59" instead of "$15.59USD".

6.3.  Target types

   The TargetType element allows tagging of different parts that are
   inside or outside a given file.  For example, in an audio file with
   one song you could have information about the album it comes from and
   even the CD set even if it's not found in the file.

   For application to know what kind of information (like TITLE) relates
   to a certain level (CD title or track title), we also need a set of
   official TargetType names.  For now audio and video will have
   different values & names.  That also means the same tag name can have
   different meanings depending on where it is (otherwise we would end
   up with 15 TITLE_ tags).

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   +=================+============+============+=======================+
   | TargetTypeValue | Audio      | Video      | Comment               |
   |                 | strings    | strings    |                       |
   +=================+============+============+=======================+
   | 70              | COLLECTION | COLLECTION | the high              |
   |                 |            |            | hierarchy             |
   |                 |            |            | consisting of         |
   |                 |            |            | many different        |
   |                 |            |            | lower items           |
   +-----------------+------------+------------+-----------------------+
   | 60              | EDITION /  | SEASON /   | a list of lower       |
   |                 | ISSUE /    | SEQUEL /   | levels grouped        |
   |                 | VOLUME /   | VOLUME     | together              |
   |                 | OPUS       |            |                       |
   +-----------------+------------+------------+-----------------------+
   | 50              | ALBUM /    | MOVIE /    | the most common       |
   |                 | OPERA /    | EPISODE /  | grouping level        |
   |                 | CONCERT    | CONCERT    | of music and          |
   |                 |            |            | video (equals         |
   |                 |            |            | to an episode         |
   |                 |            |            | for TV series)        |
   +-----------------+------------+------------+-----------------------+
   | 40              | PART /     | PART /     | when an album         |
   |                 | SESSION    | SESSION    | or episode has        |
   |                 |            |            | different             |
   |                 |            |            | logical parts         |
   +-----------------+------------+------------+-----------------------+
   | 30              | TRACK /    | CHAPTER    | the common            |
   |                 | SONG       |            | parts of an           |
   |                 |            |            | album or a            |
   |                 |            |            | movie                 |
   +-----------------+------------+------------+-----------------------+
   | 20              | SUBTRACK / | SCENE      | corresponds to        |
   |                 | PART /     |            | parts of a            |
   |                 | MOVEMENT   |            | track for audio       |
   |                 |            |            | (like a               |
   |                 |            |            | movement)             |
   +-----------------+------------+------------+-----------------------+
   | 10              | -          | SHOT       | the lowest            |
   |                 |            |            | hierarchy found       |
   |                 |            |            | in music or           |
   |                 |            |            | movies                |
   +-----------------+------------+------------+-----------------------+

                                  Table 1

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   An upper level value tag applies to the lower level.  That means if a
   CD has the same artist for all tracks, you just need to set the
   ARTIST tag at level 50 (ALBUM) and not to each TRACK (but you can).
   That also means that, if some parts of the CD have no known ARTIST,
   the value MUST be set to nothing (a void string "").

   When a 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 how these "organizational" tags work: If you
   set 10 TOTAL_PARTS to the ALBUM level (40) it means the album
   contains 10 lower parts.  The lower part in question is the first
   lower level that is specified in the file.  So, if it's TRACK (30),
   then that means it contains 10 tracks.  If it's MOVEMENT (20), that
   means it's 10 movements, etc.

6.4.  Official tags

   The following is a complete list of the supported Matroska Tags.
   While it is possible to use Tag names that are not listed below, this
   is not recommended as compatibility will be compromised.  If you find
   that there is a Tag missing that you would like to use, then please
   contact the Matroska team for its inclusion in the specifications
   before the format reaches 1.0.

6.5.  Nesting Information

   Nesting Information tags are intended to contain other tags.

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      +==========+=======+==========================================+
      | Tag Name | Type  | Description                              |
      +==========+=======+==========================================+
      | ORIGINAL | -     | 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.  All tags in this |
      |          |       | list can be used "under" the ORIGINAL    |
      |          |       | tag like LYRICIST, PERFORMER, etc.       |
      +----------+-------+------------------------------------------+
      | SAMPLE   | -     | A tag that contains other tags to        |
      |          |       | describe a sample used in the targeted   |
      |          |       | item taken from another work of art.     |
      |          |       | All tags in this list can be used        |
      |          |       | "under" the SAMPLE tag like TITLE,       |
      |          |       | ARTIST, DATE_RELEASED, etc.              |
      +----------+-------+------------------------------------------+
      | COUNTRY  | UTF-8 | The name of the country (bibliographic   |
      |          |       | ISO-639-2 form [ISO639-2]) that is meant |
      |          |       | to have other tags inside (using nested  |
      |          |       | tags) to country specific information    |
      |          |       | about the item.  All tags in this list   |
      |          |       | can be used "under" the COUNTRY_SPECIFIC |
      |          |       | tag like LABEL, PUBLISH_RATING, etc.     |
      +----------+-------+------------------------------------------+

                                  Table 2

6.6.  Organization Information

   +=============+=======+=============================================+
   | Tag Name    | Type  | Description                                 |
   +=============+=======+=============================================+
   | TOTAL_PARTS | UTF-8 | Total number of parts defined at the        |
   |             |       | first lower level. (e.g., if                |
   |             |       | TargetType is ALBUM, the total number       |
   |             |       | of tracks of an audio CD)                   |
   +-------------+-------+---------------------------------------------+
   | PART_NUMBER | UTF-8 | Number of the current part of the           |
   |             |       | current level. (e.g., if TargetType is      |
   |             |       | 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 TargetType is TRACK, the       |
   |             |       | track number of the second audio CD)        |
   +-------------+-------+---------------------------------------------+

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                                  Table 3

6.7.  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].         |
       +----------+-------+---------------------------------------+
       | SUBTITLE | UTF-8 | Sub Title of the entity.              |
       +----------+-------+---------------------------------------+

                                 Table 4

6.8.  Nested Information

   Nested Information includes tags contained in other tags.

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      +=============+=======+======================================+
      | Tag Name    | Type  | Description                          |
      +=============+=======+======================================+
      | URL         | UTF-8 | URL corresponding to the tag it's    |
      |             |       | included in.                         |
      +-------------+-------+--------------------------------------+
      | SORT_WITH   | UTF-8 | A child element to indicate what     |
      |             |       | alternative value the parent tag can |
      |             |       | have to be sorted -- for example,    |
      |             |       | "Pet Shop Boys" instead of "The Pet  |
      |             |       | Shop Boys".  Or "Marley Bob" and     |
      |             |       | "Marley Ziggy" (no comma needed).    |
      +-------------+-------+--------------------------------------+
      | INSTRUMENTS | UTF-8 | The instruments that are being used/ |
      |             |       | played, separated by a comma.  It    |
      |             |       | SHOULD be a child of the following   |
      |             |       | tags: ARTIST, LEAD_PERFORMER, or     |
      |             |       | ACCOMPANIMENT.                       |
      +-------------+-------+--------------------------------------+
      | EMAIL       | UTF-8 | Email corresponding to the tag it's  |
      |             |       | included in.                         |
      +-------------+-------+--------------------------------------+
      | ADDRESS     | UTF-8 | The physical address of the entity.  |
      |             |       | The address SHOULD include a country |
      |             |       | code.  It can be useful for a        |
      |             |       | recording label.                     |
      +-------------+-------+--------------------------------------+
      | FAX         | UTF-8 | The fax number corresponding to the  |
      |             |       | tag it's included in.  It can be     |
      |             |       | useful for a recording label.        |
      +-------------+-------+--------------------------------------+
      | PHONE       | UTF-8 | The phone number corresponding to    |
      |             |       | the tag it's included in.  It can be |
      |             |       | useful for a recording label.        |
      +-------------+-------+--------------------------------------+

                                 Table 5

6.9.  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].               |

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    +-------------------------+-------+-------------------------------+
    | LEAD_PERFORMER          | UTF-8 | Lead Performer/Soloist(s).    |
    |                         |       | This can sometimes be the     |
    |                         |       | same as ARTIST.               |
    +-------------------------+-------+-------------------------------+
    | ACCOMPANIMENT           | UTF-8 | Band/orchestra/accompaniment/ |
    |                         |       | musician.  This is akin to    |
    |                         |       | the "TPE2" tag in [ID3v2].    |
    +-------------------------+-------+-------------------------------+
    | COMPOSER                | UTF-8 | The name of the composer of   |
    |                         |       | this item.  This is akin to   |
    |                         |       | the "TCOM" tag in [ID3v2].    |
    +-------------------------+-------+-------------------------------+
    | ARRANGER                | UTF-8 | The 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 doublon to a subtitle |
    |                         |       | track).  Editing this value,  |
    |                         |       | when subtitles are found,     |
    |                         |       | SHOULD also result in editing |
    |                         |       | the subtitle track for more   |
    |                         |       | consistency.                  |
    +-------------------------+-------+-------------------------------+
    | LYRICIST                | UTF-8 | The person who wrote the      |
    |                         |       | lyrics for a musical item.    |
    |                         |       | This is akin to the "TEXT"    |
    |                         |       | tag in [ID3v2].               |
    +-------------------------+-------+-------------------------------+
    | CONDUCTOR               | UTF-8 | Conductor/performer           |
    |                         |       | refinement.  This is akin to  |
    |                         |       | the "TPE3" tag in [ID3v2].    |
    +-------------------------+-------+-------------------------------+
    | DIRECTOR                | UTF-8 | 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         |

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    |                         |       | 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 choregrapher  |
    +-------------------------+-------+-------------------------------+
    | 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      |
    |                         |       | 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 not to 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 | This is akin to the "IEDT"    |
    |                         |       | tag in [RIFF.tags].           |
    +-------------------------+-------+-------------------------------+
    | PRODUCER                | UTF-8 | Produced by.  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.                     |
    +-------------------------+-------+-------------------------------+

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    | DISTRIBUTED_BY          | UTF-8 | 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].               |
    +-------------------------+-------+-------------------------------+
    | MIXED_BY                | UTF-8 | DJ mix by the artist          |
    |                         |       | specified                     |
    +-------------------------+-------+-------------------------------+
    | REMIXED_BY              | UTF-8 | Interpreted, remixed, or      |
    |                         |       | otherwise modified by.  This  |
    |                         |       | is akin to the "TPE4" tag in  |
    |                         |       | [ID3v2].                      |
    +-------------------------+-------+-------------------------------+
    | PRODUCTION_STUDIO       | UTF-8 | 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].               |
    +-------------------------+-------+-------------------------------+
    | LABEL                   | UTF-8 | The record label or imprint   |
    |                         |       | on the disc.                  |
    +-------------------------+-------+-------------------------------+

                                  Table 6

6.10.  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 infamous "TCON" tag in         |
   |                     |       | [ID3v2].                           |
   +---------------------+-------+------------------------------------+
   | MOOD                | UTF-8 | Intended to reflect the mood of    |
   |                     |       | the item with a few keywords,      |
   |                     |       | e.g., "Romantic", "Sad" or         |

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   |                     |       | "Uplifting".  The format follows   |
   |                     |       | that of the "TMOO" tag in [ID3v2]. |
   +---------------------+-------+------------------------------------+
   | ORIGINAL_MEDIA_TYPE | UTF-8 | Describes the original type of the |
   |                     |       | media, such as, "DVD", "CD",       |
   |                     |       | "computer image," "drawing,"       |
   |                     |       | "lithograph," and so forth.  This  |
   |                     |       | is akin to the "TMED" tag in       |
   |                     |       | [ID3v2].                           |
   +---------------------+-------+------------------------------------+
   | 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].                           |
   +---------------------+-------+------------------------------------+
   | 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's    |
   |                     |       | 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 7

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6.11.  Temporal Information

    +================+=======+========================================+
    | 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].                        |
    +----------------+-------+----------------------------------------+
    | DATE_RECORDED  | UTF-8 | The time that the recording began.     |
    |                |       | This is akin to the "TDRC" tag in      |
    |                |       | [ID3v2].                               |
    +----------------+-------+----------------------------------------+
    | DATE_ENCODED   | UTF-8 | The time that the encoding of this     |
    |                |       | item was completed began.  This is     |
    |                |       | akin to the "TDEN" tag in [ID3v2].     |
    +----------------+-------+----------------------------------------+
    | DATE_TAGGED    | UTF-8 | The time that the tags were done for   |
    |                |       | this item.  This is akin to the "TDTG" |
    |                |       | tag in [ID3v2].                        |
    +----------------+-------+----------------------------------------+
    | 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 6.16 on    |
    |                |       | purchase tags.                         |
    +----------------+-------+----------------------------------------+

                                  Table 8

6.12.  Spatial Information

   +======================+=======+===================================+
   | Tag Name             | Type  | Description                       |
   +======================+=======+===================================+
   | RECORDING_LOCATION   | UTF-8 | The location where the item was   |
   |                      |       | recorded.  The countries          |
   |                      |       | corresponding to the string, same |
   |                      |       | 2 octets country-codes as in      |
   |                      |       | Internet domains [IANADomains]    |
   |                      |       | based on [ISO3166-1] alpha-2      |
   |                      |       | codes.  This code is followed by  |
   |                      |       | a comma, then more detailed       |

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   |                      |       | 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.  The |
   |                      |       | countries corresponding to the    |
   |                      |       | string, same 2 octets country-    |
   |                      |       | codes as in Internet domains      |
   |                      |       | [IANADomains] based on            |
   |                      |       | [ISO3166-1] alpha-2 codes.  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".          |
   +----------------------+-------+-----------------------------------+
   | COMPOSER_NATIONALITY | UTF-8 | Nationality of the main composer  |
   |                      |       | of the item, mostly for classical |
   |                      |       | music.  The countries             |
   |                      |       | corresponding to the string, same |
   |                      |       | 2 octets country-codes as in      |
   |                      |       | Internet domains [IANADomains]    |
   |                      |       | based on [ISO3166-1] alpha-2      |
   |                      |       | codes.                            |

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   +----------------------+-------+-----------------------------------+

                                 Table 9

6.13.  Personal

     +==============+=======+========================================+
     | Tag Name     | Type  | Description                            |
     +==============+=======+========================================+
     | COMMENT      | UTF-8 | Any comment related to the content.    |
     +--------------+-------+----------------------------------------+
     | PLAY_COUNTER | UTF-8 | The number of time 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 with decimal |
     |              |       | values possible (e.g., 2.7), 5(.0)     |
     |              |       | being the highest possible rating.     |
     |              |       | Other rating systems with different    |
     |              |       | ranges will have to be scaled.         |
     +--------------+-------+----------------------------------------+

                                  Table 10

6.14.  Technical Information

    +==================+========+=====================================+
    | 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.  This is only the   |
    |                  |        | data in the Blocks, 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.  In the event    |
    |                  |        | that lacing is used, each laced     |

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    |                  |        | chunk is to be counted as a         |
    |                  |        | separate frame.                     |
    +------------------+--------+-------------------------------------+
    | BPM              | UTF-8  | Average number of beats per minute  |
    |                  |        | in the complete target (e.g., a     |
    |                  |        | chapter).  Usually a decimal        |
    |                  |        | number.                             |
    +------------------+--------+-------------------------------------+
    | 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 default value is 440.0 |
    |                  |        | Hz.                                 |
    +------------------+--------+-------------------------------------+
    | REPLAYGAIN_GAIN  | binary | The gain to apply to reach 89dB SPL |
    |                  |        | on playback.  This is based on the  |
    |                  |        | [ReplayGain] standard.  Note that   |
    |                  |        | ReplayGain information can be found |
    |                  |        | at all TargetType levels (track,    |
    |                  |        | album, etc).                        |
    +------------------+--------+-------------------------------------+
    | REPLAYGAIN_PEAK  | binary | The maximum absolute peak value of  |
    |                  |        | the item.  This is based on the     |
    |                  |        | [ReplayGain] standard.              |
    +------------------+--------+-------------------------------------+

                                  Table 11

6.15.  Identifiers

   +================+========+=========================================+
   | Tag Name       | Type   | Description                             |
   +================+========+=========================================+
   | ISRC           | UTF-8  | The International Standard Recording    |
   |                |        | Code [ISRC], excluding the "ISRC"       |
   |                |        | prefix and including hyphens.           |
   +----------------+--------+-----------------------------------------+

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   | MCDI           | binary | This is a binary dump of the TOC of     |
   |                |        | the CDROM that this item was taken      |
   |                |        | from.  This holds the same              |
   |                |        | information as the "MCDI" in [ID3v2].   |
   +----------------+--------+-----------------------------------------+
   | 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  | Library of Congress Control Number      |
   |                |        | [LCCN].                                 |
   +----------------+--------+-----------------------------------------+
   | IMDB           | UTF-8  | Internet Movie Database [IMDb]          |
   |                |        | 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/".               |
   +----------------+--------+-----------------------------------------+
   | 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.    |
   +----------------+--------+-----------------------------------------+

                                  Table 12

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6.16.  Commercial

    +===================+=======+====================================+
    | Tag Name          | Type  | Description                        |
    +===================+=======+====================================+
    | PURCHASE_ITEM     | UTF-8 | URL to purchase this file.  This   |
    |                   |       | is akin to the "WPAY" tag in       |
    |                   |       | [ID3v2].                           |
    +-------------------+-------+------------------------------------+
    | PURCHASE_INFO     | UTF-8 | Information on where to purchase   |
    |                   |       | this album.  This is akin to the   |
    |                   |       | "WCOM" tag in [ID3v2].             |
    +-------------------+-------+------------------------------------+
    | PURCHASE_OWNER    | UTF-8 | Information on the person who      |
    |                   |       | purchased the file.  This is akin  |
    |                   |       | to the "TOWN" tag in [ID3v2].      |
    +-------------------+-------+------------------------------------+
    | PURCHASE_PRICE    | UTF-8 | The amount paid for entity.  There |
    |                   |       | SHOULD only be a numeric value in  |
    |                   |       | here.  Only numbers, no letters or |
    |                   |       | symbols other than ".".  For       |
    |                   |       | instance, you would store "15.59"  |
    |                   |       | instead of "$15.59USD".            |
    +-------------------+-------+------------------------------------+
    | PURCHASE_CURRENCY | UTF-8 | The currency type used to pay for  |
    |                   |       | the entity.  Use [ISO4217] for the |
    |                   |       | 3 letter alphabetic code.          |
    +-------------------+-------+------------------------------------+

                                 Table 13

6.17.  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].                    |
   +----------------------+-------+------------------------------------+
   | PRODUCTION_COPYRIGHT | UTF-8 | The copyright information as       |
   |                      |       | per the production copyright       |
   |                      |       | holder.  This is akin to the       |
   |                      |       | "TPRO" tag in [ID3v2].             |
   +----------------------+-------+------------------------------------+
   | LICENSE              | UTF-8 | The license applied to the         |
   |                      |       | content (like Creative             |

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   |                      |       | Commons variants).                 |
   +----------------------+-------+------------------------------------+
   | TERMS_OF_USE         | UTF-8 | The terms of use for this          |
   |                      |       | item.  This is akin to the         |
   |                      |       | "USER" tag in [ID3v2].             |
   +----------------------+-------+------------------------------------+

                                  Table 14

6.18.  Notes

   *  In the Target list, a logical OR is applied on all tracks, a
      logical OR is applied on all chapters.  Then a logical AND is
      applied between the Tracks list and the Chapters list to know if
      an element belongs to this Target.

7.  Normative References

   [GS1]      "GS1 General Specifications", GS1 20.0, January 2020,
              <https://www.gs1.org/standards/barcodes-epcrfid-id-keys/
              gs1-general-specifications>.

   [IANADomains]
              "IANA Root Zone Database",
              <https://www.iana.org/domains/root/db>.

   [ID3v2]    Nilsson, M., Mahoney, D., Ed., and J. Sundstrom, Ed., "ID3
              tag version 2.3.0", 3 February 1999,
              <https://id3.org/id3v2.3.0>.

   [IMDb]     Internet Movie Database, "IMDb API Documentation",
              <https://imdb-api.com/api>.

   [ISBN]     International ISBN Agency, "ISBN Users' Manual", December
              2017, <https://www.isbn-international.org/content/isbn-
              users-manual>.

   [ISO3166-1]
              International Organization for Standardization, "Codes for
              the representation of names of countries and their
              subdivisions -- Part 1: Country code", ISO 3166-1:2020,
              August 2020, <https://www.iso.org/standard/72482.html>.

   [ISO4217]  International Organization for Standardization, "ISO 4217
              Currency codes", ISO 4217:2015, August 2015,
              <https://www.iso.org/iso-4217-currency-codes.html>.

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   [ISO639-2] United States Library Of Congress, "Codes for the
              Representation of Names of Languages", ISO 639-2:1998, 21
              December 2017, <https://www.loc.gov/standards/iso639-
              2/php/code_list.php>.

   [ISRC]     IFPI Secretariat, "International Standard Recording Code
              (ISRC) Handbook", IFPI 3rd Edition, 2009,
              <https://www.ifpi.org/wp-content/uploads/2020/08/
              ISRC_Handbook.pdf>.

   [LCCN]     United States Library Of Congress, "Library Of Congress
              Control Number", October 1999,
              <https://www.loc.gov/marc/lccn.html>.

   [MovieDB]  The Movie Database, "The Movie Database API",
              <https://developers.themoviedb.org/3/movies/get-movie-
              details>.

   [ReplayGain]
              Robinson, D., "ReplayGain 1.0 specification", 10 July
              2001, <http://wiki.hydrogenaud.io/
              index.php?title=Replay_Gain_specification>.

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,
              <https://www.rfc-editor.org/info/rfc2119>.

   [RFC8174]  Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
              2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
              May 2017, <https://www.rfc-editor.org/info/rfc8174>.

   [TheTVDB]  The TVDB, "API documentation",
              <https://www.thetvdb.com/api-information>.

8.  Informative References

   [RIFF.tags]
              Exiftool, "RIFF Tags",
              <https://exiftool.org/TagNames/RIFF.html>.

Authors' Addresses

   Steve Lhomme

   Email: slhomme@matroska.org

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   Moritz Bunkus

   Email: moritz@bunkus.org

   Dave Rice

   Email: dave@dericed.com

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