Data compression/MP3
MP3 (or more pedanticly, MPEG 1, audio coding layer 3) is an audio compression algorithm that is able to reduce the amount of data required to reproduce high quality audio about 10-12 times relative to the data stored on a conventional audio CD. It is generally accepted that 128 Kbit/second of MP3 data is nearly CD quality. In fact, listening tests show that some listeners can reliably distinguish 128Kbps MP3 from CD originals when using very high quality listening equipment.
Many other audio compression methods exist including MPEG layer 2 (aka MP2), AAC (used by LiquidAudio, but not many others), QDesign as used in the Quicktime high bit-rate audio encoding, WMA from Microsoft, RealAudio from Real Networks, MP3Pro and Vorbis. MP2, MP3, AAC and MP3Pro are all members of the same technological family and depend on roughly similar techniques. The Fraunhofer Gesellschaft owns much of the basic intellectual property underlying these codecs, with Dolby Labs, Sony, Thomson Consumer Electronics and AT&T holding other key patents.
It has been asserted that the latest WMA and RealAudio codecs can achieve CD quality at 64 Kbps. Listening tests have shown otherwise, although the quality of these codecs at 64Kbps is definitely better than MP3 at the same bandwidth. The more recent MP3Pro is also claimed to achieve CD quality at 64Kbps, but actually achieves it at about 80 Kbps.
The Vorbis format is claimed to exceed MP3 quality and to be free of entangling intellectual property problems. I know of no rigorous listening tests to back up the quality claims and the IP questions have not been litigated, so nobody really knows for show what the status is. Of course, until there is widespread acceptance, nobody will bother with litigation and without a clear-cut status, there is unlikely to be wide-spread acceptance.
Contrary to common opinion, MP3 as an audio format is neither illegal nor is it free. Instead, licensing for encoders and decoders is controlled by Thomson Consumer Electronics.
I think this article should be on its own page (under MP3, perhaps?). Surely, there are aspects of MP3 quite aside from the fact that it's a method of data compression; e.g., it's an audio compression algorithm; it's a file type used on the Internet; etc. --LMS Cf. this page.