MP3 is a format of audio encoding. Note that MP3 is different than MPEG3
which is a video/audio format (a superset). MPEG Audio Layer 3, more commonly
referred to as MP3, is a popular digital audio encoding and lossy compression
format invented and standardized in 1991 by a team of engineers directed by the
italian engineer Leonardo Chiariglione. It was designed to greatly reduce the
amount of data required to represent audio, yet still sound like a faithful
reproduction of the original uncompressed audio to most listeners. In popular
usage, MP3 also refers to files of sound or music recordings stored in the MP3
format on computers.
A few good sites:
1 Mp3.com An essential first stop for MP3 newbies, and everything's legal.
Because of its strict policy of posting only those songs authorized by the
copyright holders, you won't find Barenaked Ladies or the Austin Powers sound
track. But there are an extensive library of songs by independent artists in all
genres and the occasional treat from some better-known ones. The FAQ is a good
primer. The software section rates dozens of players and related apps and
provides links to each download site. The hardware section gives the scoop on
portable players, sound cards and speakers.
2 Mp3.lycos.com digs up digital songs posted all over the Net, including those
hard-to-reach FTP sites, and handicaps the returns using its own "reliability
guide" (links are listed in order of how likely you are to access them). Keyword
searches are tough to fine-tune: Search for "Hole" and you get Courtney Love's
band as well as the Butthole Surfers -- an embarrassment of riches you may not
want.
3 Bigredh.com is a terrific tool for navigating the cyberworld beyond the Web.
Download the free Hotline software and head into a parallel universe, where MP3s
roam free. The search engine tracker-tracker.com delivers IP addresses and other
data you need to connect. But be warned: search results might turn up porn sites
that happen to be hosting MP3s.
MP3 is a compression format. It provides a representation of pulse-code
modulation-encoded (PCM) audio data in a much smaller size by discarding
portions that are considered less important to human hearing (similar to JPEG, a
lossy compression for images).
A number of techniques are employed in MP3 to determine which portions of the
audio can be discarded, including psychoacoustics. MP3 audio can be compressed
with different bit rates, providing a range of tradeoffs between data size and
sound quality.
The MP3 format uses, at its heart, a hybrid transformation to transform a time
domain signal into a frequency domain signal:
32-band polyphase quadrature filter
36 or 12 tap MDCT; size can be selected independent for sub-band 0...1 and
2...31
Aliasing reduction postprocessing
MP3 Surround, a version of the format supporting 5.1 channels for surround
sound, was introduced in December 2004. MP3 Surround is backward compatible with
standard stereo MP3, and file sizes are similar.
In terms of the MPEG specifications, AAC (Advanced audio coding) from MPEG-4 is
to be the successor of the MP3 format, although there has been a significant
movement to create and popularize other audio formats. Nevertheless, any
succession is not likely to happen for a significant amount of time due to MP3's
overwhelming popularity (MP3 enjoys extremely wide popularity and support, not
just by end-users and software but by hardware such as DVD and CD players).
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