APE tags comprise one extant convention used to store information (

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

) about a given

digital audio Digital audio is a representation of sound recorded in, or converted into, digital form. In digital audio, the sound wave of the audio signal is typically encoded as numerical samples in a continuous sequence. For example, in CD audio, samp ...

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 Monkey's Audio is an algorithm and file format for lossless audio data compression. Lossless data compression does not discard data during the process of encoding, unlike lossy compression methods such as Advanced Audio Coding, MP3, Vorbis, a ...

-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 compressed to reduce the file size, ofte ...

Essence

sound file 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 compressed to reduce the file size, oft ...

, such as an .ape- or

.mp3 MP3 (formally MPEG-1 Audio Layer III or MPEG-2 Audio Layer III) is a coding format for digital audio developed largely by the Fraunhofer Society in Germany, with support from other digital scientists in the United States and elsewhere. Orig ...

-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 comment A Vorbis comment is a metadata container used in the Vorbis, FLAC, Theora, Speex and Opus file formats. It allows information such as the title, artist, album, track number or other information about the file to be added to the file itself. Howeve ...

s 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 variable-length character encoding used for electronic communication. Defined by the Unicode Standard, the name is derived from ''Unicode'' (or ''Universal Coded Character Set'') ''Transformation Format 8-bit''. UTF-8 is capable of e ...

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 Monkey's Audio is an algorithm and file format for lossless audio data compression. Lossless data compression does not discard data during the process of encoding, unlike lossy compression methods such as Advanced Audio Coding, MP3, Vorbis, a ...

format.Monkey's Audio developer information.
/ref> In

MP3 MP3 (formally MPEG-1 Audio Layer III or MPEG-2 Audio Layer III) is a coding format for digital audio developed largely by the Fraunhofer Society in Germany, with support from other digital scientists in the United States and elsewhere. Origin ...

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 Musepack or MPC is an open source lossy audio codec, specifically optimized for transparent compression of stereo audio at bitrates of 160–180 (manual set allows bitrates up to 320) kbit/s. It was formerly known as MPEGplus, MPEG+ or MP+ ...

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, formally The Unicode Standard,The formal version reference is is an information technology standard for the consistent encoding, representation, and handling of text expressed in most of the world's writing systems. The standard, ...

rather than simply ASCII. Because of its simplicity and flexibility, APEv2 was adopted by the

WavPack WavPack is a free and open-source lossless audio compression format and application implementing the format. It is unique in the way that it supports hybrid audio compression alongside normal compression which is similar to how FLAC works. It ...

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 Winamp is a media player for Microsoft Windows originally developed by Justin Frankel and Dmitry Boldyrev by their company Nullsoft, which they later sold to AOL in 1999 for $80 million. It was then acquired by Radionomy in 2014. Since ve ...

foobar2000 foobar2000 (often abbreviated as fb2k or f2k) is a freeware audio player for Microsoft Windows, iOS and Android developed by Peter Pawłowski. It has a modular design, which provides user flexibility in configuration and customization. Stan ...

MusicBee MusicBee is a freeware media player for playback and organization of audio files on Microsoft Windows, built using the audio library. Features * Audio playback: MP3, AAC, M4A, MPC, OGG, FLAC, ALAC, APE, Opus, , WavPack, WMA, WAV, MI ...

support reading and writing of APEv2 tags in

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