Monkey's Audio is a file format for audio data compression. Being a lossless format, Monkey's Audio does not discard data during the process of encoding, unlike lossy compression methods such as AAC, MP3, Vorbis and Musepack.
Data file compression is employed in order to reduce bandwidth, file transfer time, and/or storage requirements. A digital recording (such as a CD) encoded to the Monkey's Audio format can be decompressed into an identical copy of the original audio data. As with the FLAC and Apple Lossless format, files encoded to Monkey's Audio are typically reduced to about half of the original size, with data transfer rates and bandwidth requirements being reduced accordingly.
Monkey's Audio's advantages are slightly better compression rates compared to FLAC and WavPack, as well as multithreading/multicore support. Monkey's Audio main drawbacks are the fact that it employs a symmetric algorithm, meaning the decoding takes comparable resources to encoding, which makes it unsuitable for all but the fastest portable players (via Rockbox firmware), and that it has limited support on software platforms other than Windows; on other platforms only decoding is officially supported by third-party programs. Although the original source code is freely available, the license is not considered to be an open source one. A GPL version of the decoder has been independently written for rockbox and then included in ffmpeg.
Monkey's Audio files use the filename extension .ape for audio, and .apl for track metadata.
Comparisons
Like any lossless compression scheme, Monkey's Audio format takes up several times as much space as lossy compression formats like AAC, MP3 and Vorbis. A Monkey's Audio file is 3–5 times larger than a 192 kbit/s bitrate MP3.
The latest version of Monkey's Audio, Version 4.06, was released on 2009-03-17. The Shorten format, popular with live taping enthusiasts for years, is no longer in development, but is still in use on some sites such as etree. FLAC has an active development community that continues to refine the format.
Although Monkey's Audio is distributed as freeware, the source code includes license terms that prevent most Linux distributions and other free software projects from including it. In contrast, FLAC has only open source licenses, so it comes pre-installed with most Linux distributions, is preferred by Linux users, and enjoys broad support in applications.
Support Platforms
Officially, Monkey's Audio is available only for the Microsoft Windows platform, though discussion on the Monkey's Audio website has hinted at future support for Linux and Mac OS. A developer using the moniker SuperMMX released an unofficial port in early 2005, which also includes plugins to allow playback using Beep Media Player and the XMMS audio player. This port was originally developed for Linux but, since version 3.99 update 4 build 4, it has included support for Mac OS X as well as Linux on the PowerPC and SPARC architectures. The port has not been updated since late 2006.
The multi-platform ffmpeg supports decoding Monkey's Audio files since version 0.5. A GStreamer plug-in is also available, but only for the older 0.8.x version. A number of OS X players and rippers support the format as well.
While the license text claims to permit using the official Monkey's Audio codec in GPL projects, several Linux distribution maintainers have found the license to be contradictory. It does not permit redistribution or modification, and thus is not considered open source or free software.
Monkey's Audio files can be encoded and decoded on any platform which has a J2SE implementation, by the means of the unofficial JMAC library, which is Free software licensed under the GNU LGPL.
On hardware platforms, the open source jukebox firmware project Rockbox supports playback of Monkey's Audio-encoded files on most of its supported targets, but many lack sufficient processing power to play the files back in real time on any but the lowest compression settings. In addition, there are a few MP3 players that natively support Monkey's Audio, including the Cowon D2 and the Iriver Spinn. As of version 4.02 (19 January 2009) a directshow filter is distributed with the installer, allowing for compatibility with most mp3 players.
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