Chapter 4: Metadata Magic 105 name, artist, album, and genre), and Exchangeable Image File Format (EXIF) metadata for still images. Since music and images also are the most common content types GEMSed by the general public, we will now discuss these metadata formats in more detail. 4.6.4 ID3v2 Augmenting music fi les with metadata is often referred to as tagging, and the most important and best-known format is ID3; the latest 35 version towards the end of 2006 being ID3v2.4.0. The term was originally coined by Eric Kemp in 1996, where the acronym comes from the words “IDentify an MP3”. Other widely used audio tagging formats are those used by Microsoft’s Windows Media Audio (WMA) fi les, and AAC (Advanced Audio Codec) fi les. AAC fi les are most often 36 encountered with Apple’s online store iTunes, where a rights- protected version of the codec is used. ID3v2 metadata is stored physically in the same fi les with the actual content, which ensures that metadata travels with the content with no extra effort when the fi les are copied or moved. This is in many cases considered a plus, as information related to the song itself is not lost. However, since the tags may also contain personal or device- dependent information, such as ratings and play counts, it is not always appropriate to transfer all metadata with the content. For instance, when transferring a song from a desktop computer to a portable music player, it may or may not be desirable that the play count indicator is retained. As a result, some rules are required to keep the record straight. ID3v2 is a container format, in practice a block of data added before the binary audio data (Figure 4-7). Each ID3v2 tag holds one or more smaller chunks of information, called frames. These frames can contain any kind of information and data, such as title, album, performer, Web site, lyrics, equalizer presets, and images. The block scheme above is an example of how the layout of a typical ID3v2-tagged audio fi le looks. ID3v2 metadata format is extensible, which allows new metadata tags to be included when required. Each tag is encoded in frames with predefi ned identifi ers, and new ones can be defi ned as needed. ID3 tags have arguably brought metadata fi elds to the mainstream public. Practically all music management software makes extensive use of these tags, which have now reached an industry standard status. 35 http://www.id3.org/ 36 http://www.apple.com/iTunes