MP3 (MPEG-1 Audio Layer-3) is a standard technology and format for compressing a sound sequence into a very small file (about one-twelfth the size of the original file) while preserving the original level of sound quality when it is played. MP3 files (identified with the file name suffix of ".mp3") are available for downloading from a number of Web sites. Many Windows users will find that they have a player built into their operating system. Otherwise, you can download a player from one of several popular MP3 sites. MP3 files are usually download-and-play files rather than streaming sound files that you link-and-listen-to with RealPlayer and similar products (However, streaming MP3 is possible.) Winamp (PC), iTunes(Mac), and mpeg123 (UNIX) are popular MP3 players, but there are many others. To create an MP3 file, you use a program called a ripper to get a selection from a CD onto your hard disk and another program called an encoder to convert the selection to an MP3 file. Most people, however, simply download MP3s from someone else and play them.
digital audio is typically created by taking 16 binary digit samples a second of the analog signal. Since this signal is typically spread out over a spectrum of 44.1 thousand cycles per second (kHz), this means that one second of CD quality sound requires 1.4 million bits of data. Using their knowledge of how people actually perceive sound, the developers of MP3 devised a compression algorithm that reduces data about sound that most listeners can not perceive. MP3 is currently the most powerful algorithm in a series of audio encoding standards developed under the sponsorship of the Motion Picture Experts Group (MPEG) and formalized by the International Organization for Standardization (ISO).
Since it is relatively easy to create MP3 files from CD selections and make them available on Web sites for downloading, companies and sites that promote the MP3 format are sometimes accused of encouraging copyright violations. (It is illegal to copy music from a CD and redistribute it unless you have the copyright owner's permission.) On the other hand, MP3 enthusiasts claim that what CD publishers are afraid of is any kind of non-CD distribution. While there are several proposals for how to discourage such piracy, there is currently no secure distribution and copyright management standard that publishers and other parties agree upon.
Several Web sites are promoting MP3 as both a high-quality audio format and as a way in which self-publishers can gain ready access to an audience. While Napster drove adoption of the format in the late 1990s through P2P file sharing, the iTunes Music Store (from Apple Computer) has created a online venue for consumers to legally download MP3s from a catalog of more than a million songs, paying anywhere from $0.99 for one song to $9.99 for an entire album.