MP3 (MPEG-1 Audio Layer 3),
more commonly referred to as MP3, is an audio encoding format.
It uses a lossy compression algorithm
that is designed to greatly reduce the amount of data required to
represent the audio recording, yet still sound like a faithful reproduction
of the original uncompressed audio to most listeners. It was invented
by a team of European engineers at Philips, CCETT (Centre commun
d'¨¦tudes de t¨¦l¨¦vision et t¨¦l¨¦communications),
IRT and Fraunhofer Society, who worked in the framework of the EUREKA
147 DAB digital radio research program, and it became an ISO/IEC
standard in 1991.
MP3 is an audio-specific
format. The compression removes certain parts of sound that are
outside the normal human hearing range so cannot be heard by the
listener. It provides a representation of pulse-code modulation
¡ª encoded audio in much less space than straightforward
methods, by using psychoacoustic models to discard components less
audible to human hearing, and recording the remaining information
in an efficient manner. Similar principles are used by JPEG, an
image compression format.
MP2 (MPEG-1 Audio
October 1993, MP2 (MPEG-1 Audio Layer 2) files appeared on the Internet
and were often played back using the Xing MPEG Audio Player, and
later in a program for Unix by Tobias Bading called MAPlay, which
was initially released on February 22, 1994 (MAPlay was also ported
to Microsoft Windows).
Initially the only encoder available
for MP2 production was the Xing Encoder, accompanied
by the program cdda2wav, a CD ripper used for extracting CD audio
tracks to Waveform Audio Files.
The Internet Underground Music
Archive (IUMA) is generally recognized as the start of the
on-line music revolution. IUMA was the Internet's first high-fidelity
music web site, hosting
thousands of authorized MP2 recordings before MP3 or the web was
Several bit rates are specified
in the MPEG-1 Layer 3 standard: 32, 40, 48, 56, 64, 80, 96, 112,
128, 160, 192, 224, 256 and 320 kbit/s, and the available sampling
frequencies are 32, 44.1 and 48 kHz. A sample rate of 44.1 kHz is
almost always used since this is also used for CD audio, the main
source used for creating MP3 files. A greater variety of bit rates
are used on the internet. 128 kbit/s is the most common since it
typically offers very good audio quality in a relatively small space.
192 kbit/s is often used by those who notice artifacts at lower
bit rates. By contrast, uncompressed audio as stored on a compact
disc has a bit rate of 1378.125 kbit/s (16 bits/sample ¡Á
44100 samples/second ¡Á 2 channels / 1024 bits/kilobit).
Some additional bit rates and sample rates were made
available in the MPEG-2 and the MPEG-2.5
standards: bit rates of 8, 16, 24, 32, 40, 48, 56, 64, 80, 96, 112,
128, 144, 160 kbit/s and sample rates of 8, 11.025, 12, 16, 22.05
and 24 kHz.
Non-standard bit rates up to 640 kbit/s can be achieved
with the LAME encoder and the freeformat option, but few MP3 players
can play those files. Gabriel Bouvigne, a principal developer of
the LAME project, says that the freeformat option is compliant with
the standard but, according to the standard, decoders are only required
to be able to decode streams up to 320 kbit/s.