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Audio Glossary

AAC

Advanced Audio Coding, or AAC, is a MPEG (Motion Pictures Experts Group) audio standard first adopted as part of the MPEG-2 family of standards. Like its predecessor, MP3, AAC is a Lossy Compression format capable of delivering relatively high quality at relatively low bitrates. There are actually two AAC specifications. In addition to the MPEG-2 version of AAC, there's a newer specification developed for MPEG-4. This version is normally found in the MP4 Container, either with or without accompanying video.

Related Guides: How to convert AAC to MP3

AIFF

Apple Computers developed this audio format to store very high quality audio. It stands for Audio Interchange File Format. The format can store mono, stereo and even multi-channel audio that is normally used in soundtracks. The format was developed in 1988 in accordance with Electronic Arts Interchange File Format (IFF) standards. All AIFF files will therefore have an .aif or .ief extension. Another feature that differentiates AIFF from other audio containers is that AIFF files are uncompressed, meaning the files hold the highest quality but are much larger in size, then say, an MP3 file.

M4A

Audio-only MPEG-4 files generally have a .m4a extension. This is especially true of non-protected content.

Related Guides: How to convert M4A to MP3

M4B

Audio book and podcast files, which also contain metadata including chapter markers, images, and hyperlinks, can use the extension .m4a, but more commonly use the .m4b extension. An .m4a audio file cannot "bookmark" (remember the last listening spot), whereas .m4b extension files can.

M4P

MPEG-4 files with audio streams encrypted by FairPlay Digital Rights Management as sold through the iTunes Store use the .m4p extension. iTunes Plus tracks are unencrypted and use .m4a accordingly.

Related Guides: How to convert M4P to MP3

M4R

The Apple iPhone uses MPEG-4 audio for its ringtones but uses the .m4r extension rather than the .m4a extension.

Related Guides: How to make free iPhone ringtones

WAV

WAV format is the standard Windows audio file format and it was originally jointly developed by Microsoft and IBM. Format itself doesn't specify any particular audio compression scheme, but actually supports several compression types. However, the most commonly used -- and the one people typically refer as ".wav file" -- is the one that uses IMA/ADPCM compression at 4:1 compression level for 16-bit sounds.

M3U

M3U was originally developed in late 1990s as a standard playlist format for MP3s, although its use has since then expanded beyond MP3s.

The .m3u files are basically just textfiles that list one MP3 or other media file on each line, normally with full path or URL to the file. If the .m3u file is loaded to an MP3 player, the player normally plays the list of media files in the order they are listed in the playlist (unless options such as "randomize" have been selected in the MP3 player).

MP2

MP2 stands for MPEG-1 Audio Layer II. MP2 is an audio codec, and is the dominant standard for audio broadcasting. It is similar to MP3, but MP3 has become the dominant standard for PC and Internet applications.

MP3

MP3 stands for MPEG-1 Audio Layer III. It is not a separate format, but a part of MPEG-1 video encoding format, developed by MPEG group in early 1990's. Too often people refer MP3 as MPEG-3, which is incorrect, because such format doesn't even exist. MPEG-1 Audio Layer III (MP3) is a method to store good quality audio into small files by using psychoacoustics in order to get rid of the data from the audio that most of the humans can't hear.

OGG

Ogg, developed by the Xiph.Org Foundation, is an open and patent-free container format for digital multimedia. Designed for efficient streaming and manipulation, it encapsulates raw compressed data (stores) and allows interleaving of audio and video data inside a convenient format.

WMA

Windows Media Audio (WMA) is an audio data compression technology developed by Microsoft. The name can be used to refer to its audio file format or its audio codecs. It is a proprietary technology that forms part of the Windows Media framework.

The WMA codecs are most often used with the ASF container format, which has an optional DRM facility. Windows Media DRM, which can be used in conjunction with WMA, supports time-limited music subscription services such as those offered by unlimited download services, including MTV's URGE, Napster, Rhapsody, Yahoo! Music Unlimited and Virgin Digital. Windows Media DRM, a component of PlaysForSure and Windows Media Connect, is supported on many modern portable audio devices and streaming media clients such as Roku, SoundBridge, Xbox 360 and Wii. Players that support the WMA format but not Windows Media DRM list protected titles as unplayable.

Related Guides: How to convert DRM WMA to MP3