MP3

abbreviation of MPEG-1, audio layer 3

Standard technology and format for the compression of audio signals into very small computer files. For example, sound data from a compact disc (CD) can be compressed to one-twelfth the original size without sacrificing sound quality. Because of small file size and ease of production from CD sources, the MP3 format is very popular for transmitting music files over the Internet. Although recording companies have sued many Web sites for facilitating the exchange of such copyrighted material, many now provide sample songs in MP3 format to promote CD sales, and some musicians bypass recording companies and issue their songs over the Internet in MP3 format only. See also data compression.

(MPEG Audio Layer 3) An audio compression technology that is part of the MPEG-1 and MPEG-2 specifications. MP3 compresses CD-quality sound (see CD-DA) by a factor of roughly 10, while retaining most of the original fidelity; for example, a 40MB CD track is turned into a 4MB MP3 file.

MP3 files are played via media player software in the computer, such as iTunes or Windows Media Player, as well as in countless iPods and other handheld players that use flash memory or hard disks for storage (see digital music player). MP3 sound quality cannot fully match the original CD, but millions of people consider it "good enough" especially because they can pack thousands of songs into a tiny pocket-sized player.

Ripping
Converting a digital audio track from a music CD to the MP3 format is called "ripping," and ripping software is available as a stand-alone program or a function in a software-based media player such as iTunes and Windows Media Player.

Bit Rates
While 128 Kbps (kilobits per second) is considered the norm for good quality MP3 files, MP3s can be ripped to bit rates from 8Kbps to 320 Kbps. The higher the bit rate, the better the sound and the larger the file. The sliding lever in the following dialog box, taken from Windows Media Player 10, is used to select four bit rates for encoding MP3s: 128, 192, 256 and 320 Kbps.

VBR and mp3PRO
MP3 VBR (variable bit rate) is an enhanced format that adjusts the compression based on the complexity of the music (see MP3 VBR). The mp3PRO format generates a file half the size of a comparable MP3 file, but maintains compatibility with many MP3 players (see mp3PRO).

MP3 Shook Up the Industry
By the end of the 1990s, music fans discovered that a CD song title converted to MP3 would still sound pretty good even though it was only 1/10th the size of the original CD track. Smaller files meant faster downloading. At an average of 4MB, it took less than 15 minutes to download a file over an analog modem. With a broadband connection on a college campus, it took seconds.

MP3 created a worldwide auditioning system for new musicians who could freely distribute their music to gain an audience. It also let people swap copyrighted titles with impunity. File sharing services such as the original Napster and Kazaa made it a global phenomenon, and the record industry went into a frenzy over violations of its copyrights (see Napster). Today, copyrighted MP3 files are still shared over the Internet. However, online music stores, including the resurrected Napster, sell tunes for a fee, legally and successfully. See peer-to-peer network and DRM.

Developed in Germany
MP3 was developed in the late 1980s by the Fraunhofer Institute in Germany. It uses perceptual audio coding to compress the data by eliminating frequencies that would not normally be heard because they overlap and cancel each other. See ID3 tag, audioblog, iPod, AAC, perceptual audio coding and cuckoo egg.

Proof of the Pudding

These iTunes examples from a Mac show the difference in file sizes from the original CD (top), which was ripped to MP3 at a recording rate of 160 Kbps (bottom). The album was reduced from an uncompressed 344MB (megabytes) to 39MB of compressed MP3s. When a music CD is inserted into a Mac, the files appear as Apple's AIFF format, which uses the same uncompressed, 16-bit PCM format as the CD (see AIFF file, CD-DA and PCM).

MP3 - MPEG-1 audio layer 3