(MPEG-1 Audio Layer III) The audio compression technology that revolutionized digital music (see "MP3 Shook Up the Industry" below). Derived from the audio sections of the MPEG-1 and MPEG-2 video specifications, MP3 compresses CD-quality sound by a factor of roughly 10, while retaining most of the original fidelity. For example, a 40MB CD track is turned into approximately a 4MB MP3 file. See CD-DA.
MP3 files are played on the computer via media player software, such as Apple's iTunes and Microsoft's Windows Media Player, as well as in countless iPods and other handheld players (see digital music player). MP3 sound quality cannot fully match the original CD, and true audiophiles complain bitterly, but millions of people consider it "good enough" because they can pack thousands of songs into a tiny pocket-sized player.
Converting a digital audio track from a music CD to the MP3 format (or other audio format) is called "ripping" or "importing," and this conversion function is built into iTunes, Windows Media Player and other jukebox software. Stand-alone rippers are also available.
Bit Rates Are Important
While 128 Kbps (kilobits per second) is considered the norm for 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. Many audiophiles rip CDs at a much higher rate for improved audio quality. In the following dialog box from Windows Media Player 10, the "Audio quality" slider is used to select four bit rates for MP3 encoding: 128, 192, 256 and 320 Kbps. There are additional variations of MP3 as well as other widely used audio formats (see MP3 VBR, mp3PRO and codec examples).
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 dial-up 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 songs legally and successfully. See peer-to-peer network
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
, codec examples
, perceptual audio coding
and cuckoo egg
Proof of the Pudding
These Mac examples show the file sizes of the original CD (top), which was ripped in iTunes to MP3 (bottom) at a recording rate of 160 Kbps. The album was reduced from 344MB to 39MB. When a music CD is inserted into a Mac, the CD's files appear in Apple's AIFF format, which is the same uncompressed, 16-bit PCM format as the CD (see AIFF