Vorbis comment
Encyclopedia
A Vorbis comment is a metadata
container used in the Vorbis
, FLAC
, Theora
and Speex
file format
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:
characters, 0x20 (space) through 0x7D ('}'), with 0x3D ('=') and 0x7E ('~') excluded. It is case insensitive, so
integer), but most tag editing applications impose stricter limits.
The data are encoded in UTF-8
, and so any Unicode
string may be used as a value.
Any tag 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 MP3
s, 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
The specification gives several example tag names such as
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.
Metadata
The term metadata is an ambiguous term which is used for two fundamentally different concepts . Although the expression "data about data" is often used, it does not apply to both in the same way. Structural metadata, the design and specification of data structures, cannot be about data, because at...
container used in the Vorbis
Vorbis
Vorbis is a free software / open source project headed by the Xiph.Org Foundation . The project produces an audio format specification and software implementation for lossy audio compression...
, FLAC
FLAC
FLAC is a codec which allows digital audio to be losslessly compressed such that file size is reduced without any information being lost...
, Theora
Theora
Theora is a free lossy video compression format. It is 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 container....
and Speex
Speex
Speex is a patent-free audio compression format designed for speech and also a free software speech codec that may be used on VoIP applications and podcasts. It is based on the CELP speech coding algorithm. Speex claims to be free of any patent restrictions and is licensed under the revised BSD...
file format
File format
A file format is a particular way that information is encoded for storage in a computer file.Since a disk drive, or indeed any computer storage, can store only bits, the computer must have some way of converting information to 0s and 1s and vice-versa. There are different kinds of formats for...
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:
Format
A Vorbis tag is a list of fields in the formatFieldName=Data. The field name can be composed of printable ASCIIASCII
The American Standard Code for Information Interchange is a character-encoding scheme based on the ordering of the English alphabet. ASCII codes represent text in computers, communications equipment, and other devices that use text...
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 a 32-bitBit
A bit is the basic unit of information in computing and telecommunications; it is the amount of information stored by a digital device or other physical system that exists in one of two possible distinct states...
integer), but most tag editing applications impose stricter limits.
The data are encoded in UTF-8
UTF-8
UTF-8 is a multibyte character encoding for Unicode. Like UTF-16 and UTF-32, UTF-8 can represent every character in the Unicode character set. Unlike them, it is backward-compatible with ASCII and avoids the complications of endianness and byte order marks...
, and so any Unicode
Unicode
Unicode is a computing industry standard for the consistent encoding, representation and handling of text expressed in most of the world's writing systems...
string may be used as a value.
Any tag name is allowed, and there is no format that the data values must be in. This is in contrast to the ID3
ID3
ID3 is a metadata container most often used in conjunction with the MP3 audio file format. It allows information such as the title, artist, album, track number, and other information about the file to be stored in the file itself....
format used for MP3
MP3
MPEG-1 or MPEG-2 Audio Layer III, more commonly referred to as MP3, is a patented digital audio encoding format using a form of lossy data compression...
s, 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 and tags for ReplayGain information.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
Container format
A container or wrapper format is a meta-file format whose specification describes how different data elements and metadata coexist in a computer file....
such as Ogg
Ogg
Ogg is a free, open container format maintained by the Xiph.Org Foundation. The creators of the Ogg format state that it is unrestricted by software patents and is designed to provide for efficient streaming and manipulation of high quality digital multimedia.The Ogg container format can multiplex...
, 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.