ID3 tag
ID3 ( English id entify an MP 3 “identify an MP3”) is a format for additional information ( metadata ) that can be contained in audio files of the MP3 format. The individual information units are called ID3 tags ( "label" tag ).
purpose
Before ID3 tags existed for information such as the name of the album, the artist or the music style, the file or directory name had to contain this information. The result was very long file names and therefore confusing directories. Furthermore, file systems are often not suitable for all the special characters that are required for certain titles, artists or album names, as well as for the length of the file names required; The character encodings also often differ, for example ISO 8859 and Unicode , special characters were misinterpreted between the various code pages of ISO 8859 or the file names are falsified during transmission over a network (more precisely through the protocols or their implementations).
So it was decided to put this metadata in a reserved part of the audio files.
Based on ID3, a similar process was developed for image files in JPEG format, which contain the date and similar information, the Exif information.
How it works and history
Meta information is not provided by default in the MP3 file format. Even in the latest version ID3v2.4, ID3 is only an informal standard that has not yet found its way into the MP3 standard. In contrast to newer formats or container formats, there is no distinction between audio and metadata, which is why pattern recognition must be used to find out whether one of the following formats is suitable.
The two main variants of the ID3 tag format, ID3v1 and ID3v2, are described in more detail below.
Versions
ID3v1
The first version, ID3v1, was introduced in 1996 by Eric Kemp with the “Studio3” program. To prevent a playback program or device from attempting to interpret the ID3v1 data as audio information, they are added to the end of the file.
ID3v1 is kept simple and consists only of a 128- byte block with a fixed structure:
| Offset | length | meaning |
|---|---|---|
| 0 | 3 | "TAG" identifier for identifying an ID3v1 block |
| 3 | 30th | Title of the piece of music |
| 33 | 30th | Artist / performer |
| 63 | 30th | album |
| 93 | 4th | Publishing year |
| 97 | 30th | Any comment |
| 127 | 1 | genre |
The character set for the text fields is not specified; ASCII , ISO 8859-1 and Unicode , encoded as UTF-8, are common . This can lead to misinterpretations of umlauts , characters in non-Latin alphabets (e.g. the Cyrillic alphabet ) and special characters .
Although ID3v1 had numerous weaknesses, it spread very quickly. The main disadvantages are:
- no expandability for further information
- Fixed length of the existing data fields: title, artist and album can only be coded with a maximum of 30 characters.
- missing information about the character encoding of the character strings
- Data is at the end: No problem for files, but impractical for streaming , since the meta information is only transferred at the end of the title.
genre
The genre is encoded as a single byte. The genre definitions 0–79 follow the ID3 tag specification from 1999. Other genres were gradually introduced in later Winamp versions and then quickly established themselves, e. B. 80-110 in December 1997, 111-115 in January 1998 with Winamp 1.7, 116-141 in April 1998 with Winamp 1.90, 142 to 147 in June 1998 with Winamp 1.91, later 148-191 with Winamp 5.6.
ID3v1.1
A further development of the ID3v1 standard turned out to be difficult because the existing fields were already rigidly specified. Michael Mutschler succeeded in expanding ID3v1.1. For this, the comment field was shortened from 30 to 28 bytes . This is followed by a zero byte which ensures that all ID3 readers finish evaluating the character strings . The released byte at position 126 was assigned the meaning of the title number .
ID3v2
Because of the weaknesses of ID3v1, Martin Nilsson and others designed a new format in 1998 that was named ID3v2. The additional information is inserted into the file in a block before or, since ID3v2.4, also after the audio data (the MPEG stream ). The current version is 4.0 (also ID3v2.4.0) from 2000.
An ID3v2 block can be recognized by the header, the first five bytes of which consist of the character string "ID3" and the ID3v2 version (e.g. $04 00for ID3v2.4). ID3v2 tags are encoded in such a way that devices or programs that do not understand ID3v2 but simply skip invalid information can play the audio files without errors.
A lot of additional information is specified in the current version 2.4, but there is hardly an implementation that supports the full range of functions . A special feature are, for example, title pictures ("cover") or entire picture series ("slide shows", collectively also known as album art ), which can be stored in the ID3 tag and identified by the PIC flag. A maximum of 256 MiB PNG or JPEG images are specified, but normally between 32 × 32 and 600 × 600 pixels are stored, which are also displayed sharply on modern smartphones.
ID3v2.2, v2.3 and v2.4
Some versions of ID3 tags are incompatible with each other. The main differences are:
- v1 to v2.2 are considered obsolete; only a few programs still write this tag version in the standard setting. Even the reason that it can be easily implemented in playback devices or programs no longer speaks for it.
- As of version 2.3, certain character encodings to be used are specified. v2.3 supports the encodings ISO 8859-1 and UTF-16 , v2.4 also supports UTF-8 .
- Usually v2 tags are at the beginning of a file, but v2.4 also allows them at the end. So far, however, there are only a few tagging programs or software or hardware players that support this variant.
- As of version 2.4, text attributes such as genre or artist can have multiple values. For example, a song can be assigned to two genres or a duet to both singers, instead of manually combining the names into a character string “Artist A, Artist B” or “Jazz-Pop”.
The most widespread version v2.3 is supported by almost all newer programs and devices; however, some have problems reading Unicode tags, even though the standard specifies this encoding.
UTF-8 encoded version 2.4 tags form the latest and most flexible version of the v2 standard. Despite significant progress recently, the new features of v2.4 are often only partially supported. In the case of text attributes with multiple values, only the first is displayed, or the values are linked so that the two genres “Pop” and “Jazz” then become, for example, “PopJazz” or “JazzPop”.
Common ID3v2 tags (selection)
Most playback programs and devices are designed primarily for pop music, while the standard does not provide for this restriction. Nevertheless, Apple introduced proprietary tags (both for mp3 and mp4) in version 12.5 of iTunes in order to better manage works outside of popular music. The following table provides information for popular music (marked with a “P”), other music (marked with a “K”), and common (without a mark).
| code | P: Pop K: otherwise |
meaning |
|---|---|---|
| TALB | Name of the album | |
| TPE1 | Interpreter ("artist") | |
| TPE2 | Album artist ("Album Artist") | |
| TPE3 | K | conductor |
| TIT1 | K | Name of the work, such as "Symphony No. 5" or "My Fair Lady" |
| TIT2 | P K |
Name of the piece of music Movement name or title, for example "I. Allegro "or" It's so green " |
| TIT3 | K | Title addition, for example “op. 42 " |
| TCOM | K | Composer ("composer") |
| TRCK | Track number / number of pieces ("Track Number") | |
| TPOS | CD number / number of CDs ("Disk Number") | |
| TCON | Genre (free text or numeric) | |
| COMM | Comment ("comment") | |
| TORY | "original year" | |
| TDRC | "year" | |
| APIC | Pictures are included here, as .jpg or .png | |
| MVNM | K | Sentence name (Apple proprietary) |
| MVIN | K | Record number / number of records (Apple proprietary) |
| GRP1 | K | Grouping (Apple proprietary) |
Note: The metadata for classical music ("movement name" and "movement index") introduced by Apple in iTunes do not comply with the standard. If “work and sentence” is used, the information is in TIT1 (instead of, for example, WORK), MVNM and MVIN, otherwise GRP1 is used (instead of TIT1). As a result, iTunes is proprietary in both modes. All common tag editors take this into account. By the way, Apple didn't make this mistake with mp4 files, so it may be an oversight.
View ID3 tags
Most mobile MP3 players can display ID3 tags. In addition, many modern operating systems and desktop environments have implemented ID3 support. In addition to the command line tools id3 (for ID3v1 tags) and id3v2 (for ID3v2 tags), Linux also offers graphic display and editing options, for example the kfile plug- in in KDE - see the Konqueror image above. Under Windows, the Explorer allows viewing and editing ID3 tags. Apart from these possibilities, most audio players also offer this function.
Editing of ID3 tags
A so-called tag editor is required to edit ID3 tags . This is already integrated in many playback programs and operating systems. There are also a number of specialized editors ( standalone tag editors) with an extended range of functions.
See also
Web links
- ID3 standard documentation (English)
- Comparison of tag names of various formats (English)
Individual evidence
- ↑ d3v2.3.0 - ID3.org. (List of genres).
- ↑ Archived copy ( memento of the original from October 7, 2013 in the web archive archive.today ) Info: The archive link has been inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. - 404
- ↑ Martin Nilsson: ID3 tag version 2.4.0 - Main Structure. Retrieved March 7, 2015 .
- ↑ ID3.org Home. Retrieved March 7, 2015 (English): “While there are legacy and future standards for ID3 tags, the most popular version implemented today is ID3 version 2.3. A follow on version, 2.4, is documented on this website but has not achieved popular status due to some disagreements on some of the revisions and the tremendous inertia present in the software and hardware marketplace. "
- ^ Richard Farrar: Embedding Album Art in MP3 Files. June 18, 2008, accessed September 7, 2011 .
