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Characteristics of different audio file formats (CD MP3 WMA WAV)

1998-04-24

There are a handful of audio file types you should be familiar withif you are planning to copy music off the Internet or even copy a CD. If youaren't sure what file types you are working with, you can distinguish any filetype on your computer by the extension in the file name. The extension is theset of letters that follows the dot, as is in: seashore.

Waveform Audio (.wav) Waveform Audio (.wav) is a common file format.Created by Microsoft and IBM, WAV was one of the first audio filetypes developed for the PC. WAV files are defined as lossless,meaning that files are large and complete; nothing has been lost.Professionally recorded CDs are also a lossless audio source.

MPEG-1 Audio Layer 3 (.mp3)MPEG-1 Audio Layer 3 (.mp3) is a common, compressed WAV file. MPEG-1 files are about one-twelfth the size of WAV files. This is why MP3 players can accommodate hundreds of songs on a tiny chunk of storage space.

Windows Media Audio (.wma)Windows Media Audio (.wma) was developed to compete with the MP3 format for Windows Media Player. Microsoft claims that the WMA files are compressed three times more than MP3s yet retain their original sound quality.

In contrast, the three audio formats listedbelow are lossy-redundant and non-auditory data is removed to allow for morecompact storage; in essence, some data has been lost. This process of removingdata to shrink the file size is called compression.

Ogg Vorbis (.ogg) Ogg Vorbis (.ogg) is another compressed source codesimilar to MP3, but like WMA, more compressed. Ogg Vorbis is also open source(free to all, unlicensed, no strings attached). While MP3 compresses data at aconstant bit rate, Ogg uses a variable bit rate. To illustrate-if you arecopying chunks of silence into MP3 format, the compression bit rate stays thesame as if you were compressing the sound of an entire orchestra. But if youare copying chunks of silence into Ogg, your compression rate will drop tonothing. The rate varies with the need.



Other Audio File Types

Musical Instrument Digital Interface (.midi)Musical Instrument Digital Interface (.midi) is commonly used for computer keyboards and other computer-based musical tools. MIDI files contain musical notes, rhythm notation and other information often needed by a composer.
Audio Interchange File (.aif, .aifc or .aiff.)Audio Interchange File (.aif, .aifc or aiff.) was developed for the Macintosh computer to store audio files.
Sun Audio (.au)Sun Audio (.au) or Audio/Basic was developed by Sun Microsystems for use on UNIX systems.
Emblaze Audio (.ea)Emblaze Audio (.ea) was created by Geo and offers compression similar to MP3 formats, but its purpose is to be played with a JAVA applet-a miniature Internet program. Online greeting cards often use JAVA applet programs for motion and .ea sound files to play music.

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