What is ID3

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What is ID3?

An audio file has additional information that describes it. Usually that is at least an artist and a title. But there could be more: recording date, track number on a CD, the CD or collection that particular piece belongs to. Maybe even an image file that shows the cover or some additional information about how to play the file. That kind of information is often called metadata as well.

With plain .wav files you have the option of storing that information in an external file. So whenever the Wave file is copied, the additional information is lost.

To avoid that, the ID3 standard was created. It defines a way of adding the information directly to the MP3 file. Almost every hardware or software player is aware of the ID3 information and knows how to use it.

LibriVox's software will automatically add ID3 tags to files during cataloging, overwriting any information which was previously entered in the ID3 tag fields. The tags used by LibriVox are:

  • Artist
  • Title
  • Album

Why does LibriVox add ID3 tags to cataloged files?

  • Simple answer: Using MP3 files with ID3 tags is a lot easier than using files without it.
  • Longer answer: Assuming only a few of the possible fields are set (say, Artist, Title, Album and Track Number), then a player will use that information to:
a. Sort files according to the information in the tags, so the parts of an audio book will be played in order :)
b. Display what you are listening to right now, and help you find other tracks
c. Group files belonging together (since they are on the same album or are part of the same audio book)

Further possible uses would be: automatic database creation (since the information is already present in the file); search for specific information like artist, title, year recorded, author and so on.

ID3v1, ID3v2, ID3v2 2.2 2.3 2.4 etc - What's that all about?

When the MP3 file format was still young, computers were slow and storage space scarce, a very simple way of storing metadata was developed - this was the ID3v1 standard. Within that scheme, the size of the tag as well as the number, names and sizes of the possible fields were fixed. The maximum length for an entry in the Title, Artist of Album fields for example was 32 characters. For some uses, that is too short (e.g. "The portrait of the artist as a young man" already has 41 characters).

Therefore ID3v2 was developed, which is more flexible and allows for more or less arbitrary lengths of fields (there is a limit, but it is very high). The "new" ID3v2 has been around for quite some time as well, therefore most players handle it very well. The additional version numbers to the ID3v2 (2.2,2.3) are of less importance. They mainly add specified fields. However, ID3v2.4 tags are not recognized by many media players/taggers/encoders and Windows media applications.