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cellar                                                         S. Lhomme
Internet-Draft
Intended status: Informational                                 M. Bunkus
Expires: 22 April 2021
                                                                 D. Rice
                                                         19 October 2020


              Matroska Media Container Tag Specifications
                       draft-ietf-cellar-tags-05

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 22 April 2021.

Copyright Notice

   Copyright (c) 2020 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 translations  . . . . . . . . . . . . . . . . . . . .   4
     6.3.  Tag Formatting  . . . . . . . . . . . . . . . . . . . . .   5
     6.4.  Target types  . . . . . . . . . . . . . . . . . . . . . .   5
     6.5.  Official tags . . . . . . . . . . . . . . . . . . . . . .   7
     6.6.  Nesting Information . . . . . . . . . . . . . . . . . . .   7
     6.7.  Organization Information  . . . . . . . . . . . . . . . .   8
     6.8.  Titles  . . . . . . . . . . . . . . . . . . . . . . . . .   8
     6.9.  Nested Information  . . . . . . . . . . . . . . . . . . .   9
     6.10. Entities  . . . . . . . . . . . . . . . . . . . . . . . .   9
     6.11. Search and Classification . . . . . . . . . . . . . . . .  11
     6.12. Temporal Information  . . . . . . . . . . . . . . . . . .  11
     6.13. Spacial Information . . . . . . . . . . . . . . . . . . .  12
     6.14. Personal  . . . . . . . . . . . . . . . . . . . . . . . .  13
     6.15. Technical Information . . . . . . . . . . . . . . . . . .  13
     6.16. Identifiers . . . . . . . . . . . . . . . . . . . . . . .  14
     6.17. Commercial  . . . . . . . . . . . . . . . . . . . . . . .  15
     6.18. Legal . . . . . . . . . . . . . . . . . . . . . . . . . .  15
     6.19. Notes . . . . . . . . . . . . . . . . . . . . . . . . . .  16
   7.  Normative References  . . . . . . . . . . . . . . . . . . . .  16
   8.  Informative References  . . . . . . . . . . . . . . . . . . .  16
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  16

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.

   For authoring Tags outside of EBML, the following XML syntax is
   proposed (https://www.matroska.org/files/tags/matroskatags.dtd) used
   in mkvmerge (https://mkvtoolnix.download/doc/
   mkvmerge.html#mkvmerge.tags).  Binary data SHOULD be stored using
   BASE64 encoding if it is being stored at authoring time.

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 translations

   To be able to save tags from other systems to Matroska we need to
   translate them to our system.  There is a translation table on our
   site (othertagsystems/comparetable.html).



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6.3.  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".

   *  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".

6.4.  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.

6.5.  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.

6.6.  Nesting Information

   Nesting Information tags are intended to contain other tags.

        +==========+======+=======================================+
        | Tag Name | Type | Description                           |
        +==========+======+=======================================+
        | ORIGINAL | -    | A special tag that is meant to have   |
        |          |      | other tags inside (using nested tags) |
        +----------+------+---------------------------------------+

                                  Table 2














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   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 ([biblio ISO-639-2](https://www.loc.gov/standards/
   iso639-2/php/English (https://www.loc.gov/standards/iso639-2/php/
   English)_list.php)) 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.

6.7.  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,              |
   +-------------+-------+---------------------------------------------+

                                  Table 3

   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)

6.8.  Titles

     +==========+=======+===========================================+
     | Tag Name | Type  | Description                               |
     +==========+=======+===========================================+
     | TITLE    | UTF-8 | The title of this item.  For example, for |
     |          |       | music you might label this "Canon in D",  |
     +----------+-------+-------------------------------------------+

                                 Table 4

   or for video's audio track you might use "English 5.1" This is akin
   to the TIT2 tag in ID3.  SUBTITLE | UTF-8 | Sub Title of the entity.






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6.9.  Nested Information

   Nested Information includes tags contained in other tags.

     +===========+=======+===========================================+
     | 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 |
     +-----------+-------+-------------------------------------------+

                                  Table 5

   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.

6.10.  Entities

       +==========+=======+=======================================+
       | Tag Name | Type  | Description                           |
       +==========+=======+=======================================+
       | ARTIST   | UTF-8 | A person or band/collective generally |
       |          |       | considered responsible for the work.  |
       +----------+-------+---------------------------------------+

                                 Table 6

   This is akin to the TPE1 tag in ID3 (http://id3.org/id3v2.3.0#TPE1).
   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 ID3 (http://id3.org/id3v2.3.0#TPE2).  COMPOSER | UTF-8 | The name
   of the composer of this item.  This is akin to the TCOM tag in ID3
   (http://id3.org/id3v2.3.0#TCOM).  ARRANGER | UTF-8 | The person who
   arranged the piece, e.g., Ravel.  LYRICS | UTF-8 | The lyrics



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   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 (http://id3.org/
   id3v2.3.0#TEXT) tag in ID3.  CONDUCTOR | UTF-8 | Conductor/performer
   refinement.  This is akin to the TPE3 (http://id3.org/
   id3v2.3.0#TPE3).  DIRECTOR | UTF-8 | This is akin to the [IART tag in
   RIFF][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 Extended RIFF.  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 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 Extended RIFF.  PRODUCER |
   UTF-8 | Produced by.  This is akin to the IPRO tag in Extended RIFF.
   COPRODUCER | UTF-8 | The name of a co-producer.  EXECUTIVE_PRODUCER |
   UTF-8 | The name of an executive producer.  DISTRIBUTED_BY | UTF-8 |
   This is akin to the IDST tag in Extended RIFF.  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 (http://id3.org/id3v2.3.0#TENC) in ID3.  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
   ID3 (http://id3.org/id3v2.3.0#TPE4).  PRODUCTION_STUDIO | UTF-8 |
   This is akin to the ISTD tag in Extended RIFF.  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 ID3
   (http://id3.org/id3v2.3.0#TPUB).  LABEL | UTF-8 | The record label or
   imprint on the disc.










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6.11.  Search and Classification

       +==========+=======+=======================================+
       | Tag Name | Type  | Description                           |
       +==========+=======+=======================================+
       | GENRE    | UTF-8 | The main genre (classical, ambient-   |
       |          |       | house, synthpop, sci-fi, drama, etc). |
       +----------+-------+---------------------------------------+

                                 Table 7

   The format follows the infamous TCON tag in ID3.  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 ID3.  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 ID3 (http://id3.org/id3v2.3.0#TMED).  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 ID3.  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).  ICRA | binary | The ICRA
   (http://www.icra.org/) content rating for parental control.
   (Previously RSACi)

6.12.  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 ID3.                           |
    +----------------+-------+---------------------------------------+
    | DATE_RECORDED  | UTF-8 | The time that the recording began.    |
    |                |       | This is akin to the TDRC tag in ID3.  |
    +----------------+-------+---------------------------------------+
    | DATE_ENCODED   | UTF-8 | The time that the encoding of this    |
    |                |       | item was completed began.  This is    |



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    |                |       | akin to the TDEN tag in ID3.          |
    +----------------+-------+---------------------------------------+
    | DATE_TAGGED    | UTF-8 | The time that the tags were done for  |
    |                |       | this item.  This is akin to the TDTG  |
    |                |       | tag in ID3.                           |
    +----------------+-------+---------------------------------------+
    | DATE_DIGITIZED | UTF-8 | The time that the item was            |
    |                |       | transferred to a digital medium.      |
    |                |       | This is akin to the IDIT tag in RIFF. |
    +----------------+-------+---------------------------------------+
    | 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 6.17 on   |
    |                |       | purchase tags.                        |
    +----------------+-------+---------------------------------------+

                                 Table 8

6.13.  Spacial Information

       +====================+=======+==============================+
       | Tag Name           | Type  | Description                  |
       +====================+=======+==============================+
       | RECORDING_LOCATION | UTF-8 | The location where the item  |
       |                    |       | was recorded.  The countries |
       |                    |       | corresponding to the string, |
       +--------------------+-------+------------------------------+

                                  Table 9

   same 2 octets as in Internet domains (https://www.iana.org/whois), or
   possibly ISO-3166 (https://www.iso.org/iso-3166-country-codes.html).
   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.  The
   countries corresponding to the string, same 2 octets as in Internet
   domains (https://www.iana.org/whois), or possibly ISO-3166
   (https://www.iso.org/iso-3166-country-codes.html).  This code is
   followed by a comma, then more detailed information such as state/
   province, another comma, and then city.  For example, "US, Texas,



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   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 as in Internet
   domains (https://www.iana.org/whois), or possibly ISO-3166
   (https://www.iso.org/iso-3166-country-codes.html).

6.14.  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 |
         +--------------+-------+-------------------------------+

                                 Table 10

   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.

6.15.  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,                   |



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

                                 Table 11

   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 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 Replay
   Gain standard (http://www.replaygain.org/).  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 Replay Gain standard
   (http://www.replaygain.org/).

6.16.  Identifiers

          +======+=======+======================================+
          | Tag  | Type  | Description                          |
          | Name |       |                                      |
          +======+=======+======================================+
          | ISRC | UTF-8 | The International Standard Recording |
          |      |       | Code (http://www.ifpi.org/isrc/      |
          |      |       | isrc_handbook.html#Heading198),      |
          +------+-------+--------------------------------------+

                                  Table 12

   excluding the "ISRC" prefix and including hyphens.  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 ID3.
   ISBN | UTF-8 | International Standard Book Number (https://www.isbn-
   international.org/) BARCODE | UTF-8 | EAN-13
   (https://www.gs1.org/standards/barcodes/ean-upc) (European Article
   Numbering) or UPC-A (http://www.uc-council.org/) (Universal Product
   Code) bar code identifier 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



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   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 (https://www.loc.gov/marc/lccn.html)
   IMDB | UTF-8 | Internet Movie Database (IMDb) (https://www.imdb.com/)
   identifier. "tt" followed by at least 7 digits for Movies, TV Shows,
   and Episodes.  TMDB | UTF-8 | The Movie Database (TMDb)
   (https://www.themoviedb.org/) identifier.  The variable length digits
   string MUST be prefixed with either "movie/" or "tv/".  TVDB |
   UTF-8 | The TV Database (TheTVDB) (https://www.thetvdb.com/)
   identifier.  Variable length all-digits string identifying a TV Show.

6.17.  Commercial

   +================+=======+=========================================+
   | Tag Name       | Type  | Description                             |
   +================+=======+=========================================+
   | PURCHASE_ITEM  | UTF-8 | URL to purchase this file.  This is     |
   |                |       | akin to the WPAY tag in ID3.            |
   +----------------+-------+-----------------------------------------+
   | PURCHASE_INFO  | UTF-8 | Information on where to purchase this   |
   |                |       | album.  This is akin to the WCOM tag in |
   |                |       | ID3.                                    |
   +----------------+-------+-----------------------------------------+
   | PURCHASE_OWNER | UTF-8 | Information on the person who purchased |
   |                |       | the file.  This is akin to the TOWN tag |
   |                |       | in ID3 (http://id3.org/id3v2.3.0#TOWN). |
   +----------------+-------+-----------------------------------------+
   | PURCHASE_PRICE | UTF-8 | The amount paid for entity.  There      |
   |                |       | SHOULD only be a numeric value in here. |
   |                |       | Only numbers,                           |
   +----------------+-------+-----------------------------------------+

                                 Table 13

   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 ISO-4217
   (https://www.xe.com/iso4217.php) for the 3 letter currency code.

6.18.  Legal

    +======================+=======+=================================+
    | Tag Name             | Type  | Description                     |
    +======================+=======+=================================+
    | COPYRIGHT            | UTF-8 | The copyright information as    |
    |                      |       | per the copyright holder.  This |
    |                      |       | is akin to the TCOP tag in ID3. |
    +----------------------+-------+---------------------------------+



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    | PRODUCTION_COPYRIGHT | UTF-8 | The copyright information as    |
    |                      |       | per the production copyright    |
    |                      |       | holder.  This is akin to the    |
    |                      |       | TPRO tag in ID3.                |
    +----------------------+-------+---------------------------------+
    | LICENSE              | UTF-8 | The license applied to the      |
    |                      |       | content (like Creative Commons  |
    |                      |       | variants).                      |
    +----------------------+-------+---------------------------------+
    | TERMS_OF_USE         | UTF-8 | The terms of use for this item. |
    |                      |       | This is akin to the USER tag in |
    |                      |       | ID3.                            |
    +----------------------+-------+---------------------------------+

                                 Table 14

6.19.  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

   [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>.

8.  Informative References

   [RIFF.tags]
              Exiftool, "RIFF Tags",
              <https://sno.phy.queensu.ca/~phil/exiftool/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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