APE tags comprise one extant convention used to store information (

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 ...

) about a given

digital audio Digital audio is a representation of sound recorded in, or converted into, digital signal (signal processing), digital form. In digital audio, the sound wave of the audio signal is typically encoded as numerical sampling (signal processing), ...

file. Each APE tag constitutes a discrete element that describes a single attribute of the file's contents. Each consists of a key/value pair; the key is simply a label that names the attribute, such as , , , or , etc.), and associated with it is a corresponding value, namely, some information descriptive of this file, in terms of the attribute in question (e.g., for ). APE tags can be used with .ape-formatted recordings, as well as with sound files of other

audio file format An audio file format is a file format for storing digital audio data on a computer system. The bit layout of the audio data (excluding metadata) is called the audio coding format and can be uncompressed, or audio compression (data), compressed t ...

Essence

A sound file, such as an .ape- or .mp3-formatted file, may, in addition to its payload audio data, also contain metadata that provide descriptive or statistical information about its audio content. When APE (v1) tags are used, they will appear at the end of the file, following the data; i.e., the digitized audio stream. Placing the tags at the end of the file, rather than at the beginning, can make expansion of the metadata simpler for programmers to code, but may add more wait time to the user experience for file loading and processing. APE field names ("keys") are character strings for which no rigid standard exists, nor is there a set list of keys nor of their allowable values.

Features

APE tags are more similar to Vorbis comments than ID3 tags. Like Vorbis comments, they are unstructured (key, value) pairs. However, unlike Vorbis comments, they do not allow for inter-key ordering. This is because they store a list of values for each key rather than one value per key. APE values can be flagged as ''text'', ''binary'', or ''external'' types. This allows tag editing software to avoid incorrectly displaying binary values, such as an image of album cover art, in the form of unreadable text to users. In comparison, Vorbis comments do not have a flagging feature, so binary data cannot be easily stored in them (though this is by design). APEv2 supports Unicode using

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 ...

for values. For keys, an ASCII subset (control characters from 0x00 to 0x1f are not allowed) must be used.

Versions

APEv1

The ''APEv1 tag'' was designed for the Monkey's Audio format.Monkey's Audio developer information.
/ref> In MP3 files, the APE tag is stored at the very end of the file, with no inline declaration in the body of the file. The software handles the writing and access to the tag and does not interfere with the contents of the MP3.

APEv2

The Musepack format developer, Frank Klemm, extended the original APE tag format to add a header, allowing APE tags to be at the beginning of files and allowing metadata values to be

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 ...

rather than simply ASCII. Because of its simplicity and flexibility, APEv2 was adopted by the WavPack and OptimFROG formats as their primary tag format. Version 3.99 of the official Monkey's Audio software switched from using APEv1 to APEv2. Media players such as Winamp, foobar2000, MusicBee support reading and writing of APEv2 tags in MP3 files. The tagging string ''APETAGEX'' signals the start of an APEv2 record, and the string ''TAG'' signals the start of an ID3v1 tag.

References

{{Reflist

External links

APEv2 standard tag field names (keys)
at Hydrogen Audio Wiki
APEv2 specifications
at Hydrogen Audio Wiki Sound production technology Metadata Computer file formats