A Vorbis comment is a

metadata Metadata (or metainformation) is "data that provides information about other data", but not the content of the data itself, such as the text of a message or the image itself. There are many distinct types of metadata, including: * Descriptive ...

container used in the Ogg file format (with Vorbis,

FLAC FLAC (; Free Lossless Audio Codec) is an audio coding format for lossless compression of digital audio, developed by the Xiph.Org Foundation, and is also the name of the free software project producing the FLAC tools, the reference software ...

Theora Theora is a free lossy video compression format. It was developed by the Xiph.Org Foundation and distributed without licensing fees alongside their other free and open media projects, including the Vorbis audio format and the Ogg contai ...

, Speex and Opus

codec A codec is a computer hardware or software component that encodes or decodes a data stream or signal. ''Codec'' is a portmanteau of coder/decoder. In electronic communications, an endec is a device that acts as both an encoder and a decoder o ...

s). It allows information such as the title, artist, album, track number or other information about the file to be added to the file itself. However, as the official Ogg Vorbis documentation notes, “ he comment headeris 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 CD-R (Compact disc-recordable) is a digital media, digital optical disc data storage device, storage format. A CD-R disc is a compact disc that can only be Write once read many, written once and read arbitrarily many times. CD-R discs (CD-Rs) ...

CD-RW RW (Compact Disc-Rewritable) is a digital media, digital optical disc data storage device, storage format introduced by Ricoh in 1997. A CD-RW compact disc (CD-RWs) can be written, read, erased, and re-written. CD-RWs, as opposed to CDs, r ...

: a few lines of notes briefly detailing the content.

Format

A Vorbis tag is a list of fields in the format FieldName=Data. The field name can be composed of printable

ASCII ASCII ( ), an acronym for American Standard Code for Information Interchange, is a character encoding standard for representing a particular set of 95 (English language focused) printable character, printable and 33 control character, control c ...

characters, 0x20 (''space'') through 0x7D (‘}’), with 0x3D (‘=’) and 0x7E (‘~’) excluded. It is case insensitive, so artist and ARTIST are the same field. The number of fields and their length is restricted to 4,294,967,295 (the maximum value of an unsigned 32- bit

integer An integer is the number zero (0), a positive natural number (1, 2, 3, ...), or the negation of a positive natural number (−1, −2, −3, ...). The negations or additive inverses of the positive natural numbers are referred to as negative in ...

), but most tag editing applications impose stricter limits.

has a smaller limit of 24- bit in a METADATA_BLOCK_VORBIS_COMMENT, because it stores thumbnails and cover art in binary

big-endian '' Jonathan_Swift.html" ;"title="Gulliver's Travels'' by Jonathan Swift">Gulliver's Travels'' by Jonathan Swift, the novel from which the term was coined In computing, endianness is the order in which bytes within a word (data type), word of d ...

METADATA_BLOCK_PICTUREs outside of the FLAC tags. The data is encoded in

UTF-8 UTF-8 is a character encoding standard used for electronic communication. Defined by the Unicode Standard, the name is derived from ''Unicode Transformation Format 8-bit''. Almost every webpage is transmitted as UTF-8. UTF-8 supports all 1,112,0 ...

, and so any conforming

Unicode Unicode or ''The Unicode Standard'' or TUS is a character encoding standard maintained by the Unicode Consortium designed to support the use of text in all of the world's writing systems that can be digitized. Version 16.0 defines 154,998 Char ...

string may be used as a value. Any field name is allowed, and there is no format that the data values must be in. This is in contrast to the ID3 format used for MP3s, which is highly structured. Field names are also permitted to be used more than once. It is encouraged to use this feature to support multiple values, for example two ARTIST=... fields to list both artists of a single composition. The specification gives several example tag names such as TITLE and TRACKNUMBER. Most applications also support common ''de facto'' standards, such as DISCNUMBER, RATING, and tags for ReplayGain information. Ratings are usually mapped as 1-5 stars with 20,40,60,80,100 as the actual string values. There are no provisions for storing binary data in Vorbis comments. This is by design; they are intended to be used as part of a container format such as Ogg, and any additional binary data should be encoded into the container as a stream. The exception to this, by popular request, is a proposal to incorporate cover art into a Vorbis comment.

References

{{Xiph.org Metadata Computer file formats Xiph.Org projects

Format

See also

References