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Digital Audio Essentials by Bruce Fries, Marty Fries

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Embedded Data

MPEG Audio can include metadata for information such as lyrics, album artwork, and even links to web sites. Most jukebox programs use metadata to allow you to sort, browse, and search your music collection in many different ways (see Chapter 4). The part of an encoded file where metadata is stored is commonly referred to as a tag.

ID3 tags

The standard for MP3 does not cover metadata, so developers took matters into their own hands and created a specification called ID3 for storing non-audio information inside MP3 files. Most programs and portable players that support MP3 also support ID3 tags.

ID3 Version 1.1

ID3 Version 1 is limited to 128 bytes of data and contains fixed-length fields for title, artist, album, year, comments, track number, and genre. Most audio CDs do not contain this information, so you must enter it manually or obtain it from a database such as the CDDB (see Chapter 12). The identification field must contain the characters “TAG” to indicate ID3 compliance. In Version 1.1, the ID3 tag is placed at the end of the MP3 file.

Table 10-2 shows the structure used for ID3 Version 1.1 tags. The tags are limited to 128 bytes of data and 30 characters per field. Table 10-3 shows the standard codes for the genre field. Numeric codes are used to save space. Some genres—e.g., Rock, Classic Rock, and Hard Rock—overlap. Others, such as Space and Darkwave, are open to interpretation.

Table 10-2. ID3v1.1 tags

Position

Length (in bytes)

Field

0–2

3

Identification ...

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