Vorbis comment

However, as the official Ogg Vorbis documentation notes, “[the comment header] is meant for short, text comments, not arbitrary metadata; arbitrary metadata belongs in a separate logical bitstream (usually an XML stream type) that provides greater structure and machine parseability.” Instead, the intended function of Vorbis comments is to approximate the kind of information that might be hand-inked onto a blank faced CD-R or CD-RW: a few lines of notes briefly detailing the content.

The number of fields and their length is restricted to 4,294,967,295 (the maximum value of an unsigned 32-bit integer), but most tag editing applications impose stricter limits.

It is encouraged to use this feature to support multiple values, for example two ARTIST=... fields to list both artists of a single composition.

Most applications also support common de facto standards, such as DISCNUMBER, RATING, and tags for ReplayGain information.

The exception to this, by popular request, is a proposal to incorporate cover art into a Vorbis comment.