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location: id3v2.3.0

Informal Standard BRDocument: id3v2.3

M. Nilsson BR3rd February 199

ID3 tag version 2.3.0

Status of this document

This document is an informal standard and replaces the [:id3v2-00: id3v2.2.0] standard. The informal standard is released so that implementors could have a set standard before a formal standard is set. The formal standard will use another version or revision number if not identical to what is described in this document. The contents in this document may change for clarifications but never for added or altered functionallity.

Distribution of this document is unlimited.

Abstract

This document describes the ID3v2.3.0 standard, which is a more developed version of the ID3v2 informal standard (version [:id3v2-00: 2.2.0]), evolved from the ID3 tagging system. The ID3v2 offers a flexible way of storing information about an audio file within itself to determine its origin and contents. The information may be technical information, such as equalisation curves, as well as related meta information, such as title, performer, copyright etc.

TableOfContents([maxdepth])

Conventions in this document

In the examples, text within "" is a text string exactly as it appears in a file. Numbers preceded with $ are hexadecimal and numbers preceded with % are binary. $xx is used to indicate a byte with unknown content. %x is used to indicate a bit with unknown content. The most significant bit (MSB) of a byte is called 'bit 7' and the least significant bit (LSB) is called 'bit 0'.

A tag is the whole tag described in this document. A frame is a block of information in the tag. The tag consists of a header, frames and optional padding. A field is a piece of information; one value, a string etc. A numeric string is a string that consists of the characters 0-9 only.

ID3v2 overview

The two biggest design goals were to be able to implement ID3v2 without disturbing old software too much and that ID3v2 should be as flexible and expandable as possible.

The first criterion is met by the simple fact that the [#MPEG MPEG] decoding software uses a syncsignal, embedded in the audiostream, to 'lock on to' the audio. Since the ID3v2 tag doesn't contain a valid syncsignal, no software will attempt to play the tag. If, for any reason, coincidence make a syncsignal appear within the tag it will be taken care of by the 'unsynchronisation scheme' described in [#sec5 section 5].

The second criterion has made a more noticeable impact on the design of the ID3v2 tag. It is constructed as a container for several information blocks, called frames, whose format need not be known to the software that encounters them. At the start of every frame there is an identifier that explains the frames' format and content, and a size descriptor that allows software to skip unknown frames.

If a total revision of the ID3v2 tag should be needed, there is a version number and a size descriptor in the ID3v2 header.

The ID3 tag described in this document is mainly targeted at files encoded with [#MPEG MPEG]-1/2 layer I, [#MPEG MPEG]-1/2 layer II, [#MPEG MPEG]-1/2 layer III and [#MPEG MPEG]-2.5, but may work with other types of encoded audio.

The bitorder in ID3v2 is most significant bit first (MSB). The byteorder in multibyte numbers is most significant byte first (e.g. $12345678 would be encoded $12 34 56 78).

It is permitted to include padding after all the final frame (at the end of the ID3 tag), making the size of all the frames together smaller than the size given in the head of the tag. A possible purpose of this padding is to allow for adding a few additional frames or enlarge existing frames within the tag without having to rewrite the entire file. The value of the padding bytes must be $00.

ID3v2 header

The ID3v2 tag header, which should be the first information in the file, is 10 bytes as follows: {{{ID3v2/file identifier "ID3" ID3v2 version $03 00 ID3v2 flags %abc00000 ID3v2 size 4 * %0xxxxxxx }}} The first three bytes of the tag are always "ID3" to indicate that this is an ID3v2 tag, directly followed by the two version bytes. The first byte of ID3v2 version is it's major version, while the second byte is its revision number. In this case this is ID3v2.3.0. All revisions are backwards compatible while major versions are not. If software with ID3v2.2.0 and below support should encounter version three or higher it should simply ignore the whole tag. Version and revision will never be $FF.

The version is followed by one the ID3v2 flags field, of which currently only three flags are used.

a - Unsynchronisation
Bit 7 in the 'ID3v2 flags' indicates whether or not unsynchronisation is used (see section 5 for details); a set bit indicates usage.
b - Extended header
The second bit (bit 6) indicates whether or not the header is followed by an extended header. The extended header is described in [#sec3.2 section 3.2].
c - Experimental indicator
The third bit (bit 5) should be used as an 'experimental indicator'. This flag should always be set when the tag is in an experimental stage.

All the other flags should be cleared. If one of these undefined flags are set that might mean that the tag is not readable for a parser that does not know the flags function.

The ID3v2 tag size is encoded with four bytes where the most significant bit (bit 7) is set to zero in every byte, making a total of 28 bits. The zeroed bits are ignored, so a 257 bytes long tag is represented as $00 00 02 01.

The ID3v2 tag size is the size of the complete tag after unsychronisation, including padding, excluding the header but not excluding the extended header (total tag size - 10). Only 28 bits (representing up to 256MB) are used in the size description to avoid the introducuction of 'false syncsignals'.

An ID3v2 tag can be detected with the following pattern: {{{$49 44 33 yy yy xx zz zz zz zz }}} Where yy is less than $FF, xx is the 'flags' byte and zz is less than $80.

ID3v2 extended header

The extended header contains information that is not vital to the correct parsing of the tag information, hence the extended header is optional. {{{Extended header size $xx xx xx xx Extended Flags $xx xx Size of padding $xx xx xx xx }}} Where the 'Extended header size', currently 6 or 10 bytes, excludes itself. The 'Size of padding' is simply the total tag size excluding the frames and the headers, in other words the padding. The extended header is considered separate from the header proper, and as such is subject to unsynchronisation.

The extended flags are a secondary flag set which describes further attributes of the tag. These attributes are currently defined as follows {{{%x0000000 00000000 }}}

}}}

ID3v2 frame overview

As the tag consists of a tag header and a tag body with one or more frames, all the frames consists of a frame header followed by one or more fields containing the actual information. The layout of the frame header: {{{Frame ID $xx xx xx xx (four characters) Size $xx xx xx xx Flags $xx xx }}} The frame ID made out of the characters capital A-Z and 0-9. Identifiers beginning with "X", "Y" and "Z" are for experimental use and free for everyone to use, without the need to set the experimental bit in the tag header. Have in mind that someone else might have used the same identifier as you. All other identifiers are either used or reserved for future use.

The frame ID is followed by a size descriptor, making a total header size of ten bytes in every frame. The size is calculated as frame size excluding frame header (frame size - 10).

In the frame header the size descriptor is followed by two flags bytes. These flags are described in section 3.3.1.

There is no fixed order of the frames' appearance in the tag, although it is desired that the frames are arranged in order of significance concerning the recognition of the file. An example of such order: UFID, TIT2, MCDI, TRCK ...

A tag must contain at least one frame. A frame must be at least 1 byte big, excluding the header.

If nothing else is said a string is represented as ISO-8859-1 characters in the range $20 - $FF. Such strings are represented as <text string>, or <full text string> if newlines are allowed, in the frame descriptions. All Unicode strings use 16-bit unicode 2.0 (ISO/IEC 10646-1:1993, UCS-2). Unicode strings must begin with the Unicode BOM ($FF FE or $FE FF) to identify the byte order.

All numeric strings and URLs are always encoded as ISO-8859-1. Terminated strings are terminated with $00 if encoded with ISO-8859-1 and $00 00 if encoded as unicode. If nothing else is said newline character is forbidden. In ISO-8859-1 a new line is represented, when allowed, with $0A only. Frames that allow different types of text encoding have a text encoding description byte directly after the frame size. If ISO-8859-1 is used this byte should be $00, if Unicode is used it should be $01. Strings dependent on encoding is represented as <text string according to encoding>, or <full text string according to encoding> if newlines are allowed. Any empty Unicode strings which are NULL-terminated may have the Unicode BOM followed by a Unicode NULL ($FF FE 00 00 or $FE FF 00 00).

The three byte language field is used to describe the language of the frame's content, according to ISO-639-2.

All URLs may be relative, e.g. "picture.png", "../doc.txt".

If a frame is longer than it should be, e.g. having more fields than specified in this document, that indicates that additions to the frame have been made in a later version of the ID3v2 standard. This is reflected by the revision number in the header of the tag.

Frame header flags

In the frame header the size descriptor is followed by two flags bytes. All unused flags must be cleared. The first byte is for 'status messages' and the second byte is for encoding purposes. If an unknown flag is set in the first byte the frame may not be changed without the bit cleared. If an unknown flag is set in the second byte it is likely to not be readable. The flags field is defined as follows. {{{%abc00000 %ijk00000 }}}

a - Tag alter preservation
This flag tells the software what to do with this frame if it is unknown and the tag is altered in any way. This applies to all kinds of alterations, including adding more padding and reordering the frames. {{{0 Frame should be preserved.

1 Frame should be discarded. }}}

b - File alter preservation
This flag tells the software what to do with this frame if it is unknown and the file, excluding the tag, is altered. This does not apply when the audio is completely replaced with other audio data.
0    Frame should be preserved.
1    Frame should be discarded.
c - Read only
This flag, if set, tells the software that the contents of this frame is intended to be read only. Changing the contents might break something, e.g. a signature. If the contents are changed, without knowledge in why the frame was flagged read only and without taking the proper means to compensate, e.g. recalculating the signature, the bit should be cleared.
i - Compression
This flag indicates whether or not the frame is compressed. {{{0 Frame is not compressed.

1 Frame is compressed using zlib with 4 bytes for 'decompressed size' appended to the frame header. }}}

j - Encryption
This flag indicates wether or not the frame is enrypted. If set one byte indicating with which method it was encrypted will be appended to the frame header. See section 4.26. for more information about encryption method registration. {{{0 Frame is not encrypted.

1 Frame is encrypted. }}}

k - Grouping identity
This flag indicates whether or not this frame belongs in a group with other frames. If set a group identifier byte is added to the frame header. Every frame with the same group identifier belongs to the same group. {{{0 Frame does not contain group information

1 Frame contains group information }}}

Some flags indicates that the frame header is extended with additional information. This information will be added to the frame header in the same order as the flags indicating the additions. I.e. the four bytes of decompressed size will preceed the encryption method byte. These additions to the frame header, while not included in the frame header size but are included in the 'frame size' field, are not subject to encryption or compression.

Default flags

The default settings for the frames described in this document can be divided into the following classes. The flags may be set differently if found more suitable by the software.

  1. Discarded if tag is altered, discarded if file is altered.
    • None.
  2. Discarded if tag is altered, preserved if file is altered.
    • None.
  3. Preserved if tag is altered, discarded if file is altered.
    • ETCO, EQUA, MLLT, POSS, SYLT, SYTC, RVAD, TENC, TLEN, TSIZ
  4. Preserved if tag is altered, preserved if file is altered.
    • The rest of the frames.

Declared ID3v2 frames

The following frames are declared in this draft. {{{4.20 AENC Audio encryption 4.15 APIC Attached picture 4.11 COMM Comments 4.25 COMR Commercial frame 4.26 ENCR Encryption method registration 4.13 EQUA Equalization 4.6 ETCO Event timing codes 4.16 GEOB General encapsulated object 4.27 GRID Group identification registration 4.4 IPLS Involved people list 4.21 LINK Linked information 4.5 MCDI Music CD identifier 4.7 MLLT MPEG location lookup table 4.24 OWNE Ownership frame 4.28 PRIV Private frame 4.17 PCNT Play counter 4.18 POPM Popularimeter 4.22 POSS Position synchronisation frame 4.19 RBUF Recommended buffer size 4.12 RVAD Relative volume adjustment 4.14 RVRB Reverb 4.10 SYLT Synchronized lyric/text 4.8 SYTC Synchronized tempo codes 4.2.1 TALB Album/Movie/Show title 4.2.1 TBPM BPM (beats per minute) 4.2.1 TCOM Composer 4.2.1 TCON Content type 4.2.1 TCOP Copyright message 4.2.1 TDAT Date 4.2.1 TDLY Playlist delay 4.2.1 TENC Encoded by 4.2.1 TEXT Lyricist/Text writer 4.2.1 TFLT File type 4.2.1 TIME Time 4.2.1 TIT1 Content group description 4.2.1 TIT2 Title/songname/content description 4.2.1 TIT3 Subtitle/Description refinement 4.2.1 TKEY Initial key 4.2.1 TLAN Language(s) 4.2.1 TLEN Length 4.2.1 TMED Media type 4.2.1 TOAL Original album/movie/show title 4.2.1 TOFN Original filename 4.2.1 TOLY Original lyricist(s)/text writer(s) 4.2.1 TOPE Original artist(s)/performer(s) 4.2.1 TORY Original release year 4.2.1 TOWN File owner/licensee 4.2.1 TPE1 Lead performer(s)/Soloist(s) 4.2.1 TPE2 Band/orchestra/accompaniment 4.2.1 TPE3 Conductor/performer refinement 4.2.1 TPE4 Interpreted, remixed, or otherwise modified by 4.2.1 TPOS Part of a set 4.2.1 TPUB Publisher 4.2.1 TRCK Track number/Position in set 4.2.1 TRDA Recording dates 4.2.1 TRSN Internet radio station name 4.2.1 TRSO Internet radio station owner 4.2.1 TSIZ Size 4.2.1 TSRC ISRC (international standard recording code) 4.2.1 TSSE Software/Hardware and settings used for encoding 4.2.1 TYER Year 4.2.2 TXXX User defined text information frame 4.1 UFID Unique file identifier 4.23 USER Terms of use 4.9 USLT Unsychronized lyric/text transcription 4.3.1 WCOM Commercial information 4.3.1 WCOP Copyright/Legal information 4.3.1 WOAF Official audio file webpage 4.3.1 WOAR Official artist/performer webpage 4.3.1 WOAS Official audio source webpage 4.3.1 WORS Official internet radio station homepage 4.3.1 WPAY Payment 4.3.1 WPUB Publishers official webpage 4.3.2 WXXX User defined URL link frame }}}

Unique file identifier

This frame's purpose is to be able to identify the audio file in a database that may contain more information relevant to the content. Since standardisation of such a database is beyond this document, all frames begin with a null-terminated string with a URL containing an email address, or a link to a location where an email address can be found, that belongs to the organisation responsible for this specific database implementation. Questions regarding the database should be sent to the indicated email address. The URL should not be used for the actual database queries. The string "http://www.id3.org/dummy/ufid.html" should be used for tests. Software that isn't told otherwise may safely remove such frames. The 'Owner identifier' must be non-empty (more than just a termination). The 'Owner identifier' is then followed by the actual identifier, which may be up to 64 bytes. There may be more than one "UFID" frame in a tag, but only one with the same 'Owner identifier'.

Owner identifier <text string> $00 Identifier <up to 64 bytes binary data> }}}

Text information frames

The text information frames are the most important frames, containing information like artist, album and more. There may only be one text information frame of its kind in an tag. If the textstring is followed by a termination ($00 (00)) all the following information should be ignored and not be displayed. All text frame identifiers begin with "T". Only text frame identifiers begin with "T", with the exception of the "TXXX" frame. All the text information frames have the following format:

Text encoding $xx Information <text string according to encoding> }}}

Text information frames - details

TALB
The 'Album/Movie/Show title' frame is intended for the title of the recording(/source of sound) which the audio in the file is taken from.
TBPM
The 'BPM' frame contains the number of beats per minute in the mainpart of the audio. The BPM is an integer and represented as a numerical string.
TCOM
The 'Composer(s)' frame is intended for the name of the composer(s). They are seperated with the "/" character.
TCON
The 'Content type', which previously was stored as a one byte numeric value only, is now a numeric string. You may use one or several of the types as ID3v1.1 did or, since the category list would be impossible to maintain with accurate and up to date categories, define your own.

References to the ID3v1 genres can be made by, as first byte, enter "(" followed by a number from the genres list (appendix A) and ended with a ")" character. This is optionally followed by a refinement, e.g. "(21)" or "(4)Eurodisco". Several references can be made in the same frame, e.g. "(51)(39)". If the refinement should begin with a "(" character it should be replaced with "((", e.g. "((I can figure out any genre)" or "(55)((I think...)". The following new content types is defined in ID3v2 and is implemented in the same way as the numerig content types, e.g. "(RX)".

CR Cover }}}

TCOP
The 'Copyright message' frame, which must begin with a year and a space character (making five characters), is intended for the copyright holder of the original sound, not the audio file itself. The absence of this frame means only that the copyright information is unavailable or has been removed, and must not be interpreted to mean that the sound is public domain. Every time this field is displayed the field must be preceded with "Copyright © ".
TDAT
The 'Date' frame is a numeric string in the DDMM format containing the date for the recording. This field is always four characters long.
TDLY
The 'Playlist delay' defines the numbers of milliseconds of silence between every song in a playlist. The player should use the "ETC" frame, if present, to skip initial silence and silence at the end of the audio to match the 'Playlist delay' time. The time is represented as a numeric string.
TENC
The 'Encoded by' frame contains the name of the person or organisation that encoded the audio file. This field may contain a copyright message, if the audio file also is copyrighted by the encoder.
TEXT
The 'Lyricist(s)/Text writer(s)' frame is intended for the writer(s) of the text or lyrics in the recording. They are seperated with the "/" character.
TFLT
The 'File type' frame indicates which type of audio this tag defines. The following type and refinements are defined: {{{MPG MPEG Audio

/1 MPEG 1/2 layer I /2 MPEG 1/2 layer II /3 MPEG 1/2 layer III /2.5 MPEG 2.5

VQF Transform-domain Weighted Interleave Vector Quantization PCM Pulse Code Modulated audio }}} but other types may be used, not for these types though. This is used in a similar way to the predefined types in the "TMED" frame, but without parentheses. If this frame is not present audio type is assumed to be "MPG".

TIME
The 'Time' frame is a numeric string in the HHMM format containing the time for the recording. This field is always four characters long.
TIT1
The 'Content group description' frame is used if the sound belongs to a larger category of sounds/music. For example, classical music is often sorted in different musical sections (e.g. "Piano Concerto", "Weather - Hurricane").
TIT2
The 'Title/Songname/Content description' frame is the actual name of the piece (e.g. "Adagio", "Hurricane Donna").
TIT3
The 'Subtitle/Description refinement' frame is used for information directly related to the contents title (e.g. "Op. 16" or "Performed live at Wembley").
TKEY
The 'Initial key' frame contains the musical key in which the sound starts. It is represented as a string with a maximum length of three characters. The ground keys are represented with "A","B","C","D","E", "F" and "G" and halfkeys represented with "b" and "#". Minor is represented as "m". Example "Cbm". Off key is represented with an "o" only.
TLAN
The 'Language(s)' frame should contain the languages of the text or lyrics spoken or sung in the audio. The language is represented with three characters according to ISO-639-2. If more than one language is used in the text their language codes should follow according to their usage.
TLEN
The 'Length' frame contains the length of the audiofile in milliseconds, represented as a numeric string.
TMED
The 'Media type' frame describes from which media the sound originated. This may be a text string or a reference to the predefined media types found in the list below. References are made within "(" and ")" and are optionally followed by a text refinement, e.g. "(MC) with four channels". If a text refinement should begin with a "(" character it should be replaced with "((" in the same way as in the "TCO" frame. Predefined refinements is appended after the media type, e.g. "(CD/A)" or "(VID/PAL/VHS)".
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