Sustainability of Digital Formats
 Planning for Library of Congress Collections

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Identification and description

Full name	ID3 Metadata for MP3, Version 1
Description	Structured data chunk containing descriptive metadata about the file to which it is appended, virtually always an MP3_FF (MP3 sound file). Referred to by its creators as an "informal standard" for a "container format," the two versions of ID3 permit the identification of title, artist, date, genre, etc. and so on.
Production phase	Generally used for final-state, end-user delivery.
Relationship to other formats
Has subtype	ID3v1, ID3, Version 1
Has subtype	ID3v2, ID3, Version 2
May contain	Images, encrypted information, etc.
Used by	MP3_FF, MP3 file format

Local use

LC experience or existing holdings	ID3 is used extensively with American Memory MP3 service files. Although many are limited to version 1 tagging, examples like http://lcweb4.loc.gov/afc/afcreed/130/13033b03.mp3 include tagging in both versions 1 and 2.
LC preference	General preference for recorded sound is WAVE_LCPM. For compressed sound, high-bitrate MP3_ENC is acceptable. If examples are acquired, the Library prefers documentation to be as extensive as possible; an ID3 chunk, especially ID3v2, is very suitable for the delivery of such metadata.

Sustainability factors

Disclosure	Version 2 is fully documented; version 1 less so. Developed by Martin Nilsson and colleagues; see also Notes.
Documentation	See ID3v1 and ID3v2
Adoption	Very widely adopted for World Wide Web dissemination and playback on specialized devices.
Licensing and patent claims	None
Transparency	Easily parsed binary bitstream.
Self-documentation	Not applicable as it pertains to ID3 itself; ID3 contains descriptive ("bibliographic") metadata as its payload. ID3v2 (version 2) is much more extensive than ID3v1 (version 1).
External dependencies	None
Technical protection considerations	None

Quality and functionality factors

Normal rendering for sound	Not applicable
Fidelity (support for high audio resolution)	Not applicable
Support for multiple sound channels	Not applicable
Support for downloadable or user-defined sounds, samples, and patches	Not applicable
Functionality beyond normal rendering for sound	ID3v2 (version 2) appears to allow for synchronized texts, e.g., karaoke, and supports "addenda" for chapter markers, tables of contents, and accessibility support.

File type signifiers

Tag type	Value	Note
Filename Extension	Not applicable
Internet Media Type	Not applicable
Magic numbers	Not applicable	See 3DI marker information in Notes below.

Notes

General

ID3 binary content is structured as "frames" just like MP3_ENC (MP3 audio encoding). When ID3 metadata is placed in a MP3_FF file, established conventions call for the use of the ID3 marker which consists of the string "3DI". For ID3v1, the marker is positioned 10 bytes preceding the metadata. For ID3v2 data, the marker is positioned in the first 3 bytes of the file when the metadata is pre-pended and 10 bytes from the end of a file when it is post-pended.

History

According to Martin Nilsson's web site ID3.org, Erik Kemp was the first to append metadata to an MP3 file in 1996, with a program named Studio3. This idea was elaborated by Nilsson (a Swedish electrical engineer and antenna researcher), Michael Mutschler (a colleague from Germany), and others, and emerged first as ID3v1 and later, with richer expression, as ID3v2. Their account of their own work provides no dates, except to indicate that it postdates Kemp's contribution. Mutschler is also associated with MP3ext, described as a shell extension for the Windows Explorer that adds features for MP3 files.

Format specifications

URLs
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Useful references

URLs
• www.id3.org (http://www.id3.org)
• History page at www.id3.org (http://www.id3.org/history.html)
• ID3 article in Wikipedia, consulted February 2007 (http://en.wikipedia.org/wiki/ID3">ID3).
• American Memory MP3 file with tagging in both ID3v1 and ID3v2 (http://lcweb4.loc.gov/afc/afcreed/130/13033b03.mp3)
• MP3ext (http://www.mutschler.de/mp3ext/)

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