MPEG is the famous four-letter
word which stands for the "Moving Pictures Experts Groups.
To the real
word, MPEG is a generic means of compactly representing digital video and audio
signals for consumer distributionThe essence of MPEG is its syntax: the little
tokens that make up the bitstream. MPEG's semantics then tell you (if you happen
to be a decoder, that is) how to inverse represent the compact tokens back into
something resembling the original stream of samples.
semantics are merely a collection of rules (which people like to called algorithms,
but that would imply there is a mathematical coherency to a scheme cooked up by
trial and error
.). These rules are highly reactive to combinations of bitstream
elements set in headers and so forth.
is an institution unto itself as seen from within its own universe. When (unadvisedly)
placed in the same room, its inhabitants a blood-letting debate can spontaneously
erupt among, triggered by mere anxiety over the most subtle juxtaposition of words
buried in the most obscure documents. Such stimulus comes readily from transparencies
flashed on an overhead projector. Yet at the same time, this gestalt will appear
to remain totally indifferent to critical issues set before them for many months.
It should therefore be no surprise that MPEG's
dualistic chemistry reflects the extreme contrasts of its two founding fathers:
the fiery Leonardo Chairiglione (CSELT, Italy) and the peaceful Hiroshi Yasuda
(JVC, Japan). The excellent byproduct of the successful MPEG Processes became
an International Standards document safely administered to the public in three
parts: Systems (Part), Video (Part 2), and Audio (Part 3).
Before providence gave us MPEG, there was the looming threat of world
domination by proprietary standards cloaked in syntactic mystery. With lossy compression
being such an inexact science (which always boils down to visual tweaking and
implementation tradeoffs), you never know what's really behind any such scheme
(other than a lot of the marketing hype).
Seeing this threat
need for world interoperability, the Fathers of MPEG sought help of their colleagues
to form a committee to standardize a common means of representing video and audio
(a la DVI) onto compact discs
. and maybe it would be useful for other things
MPEG borrowed a significantly from JPEG
and, more directly, H.261. By the end of the third year (1990), a syntax emerged,
which when applied to represent SIF-rate video and compact disc-rate audio at
a combined bitrate of 1.5 Mbit/sec, approximated the pleasure-filled viewing experience
offered by the standard VHS format.
demonstrations proved that the syntax was generic enough to be applied to bit
rates and sample rates far higher than the original primary target application
("Hey, it actually works!"), a second phase (MPEG-2) was initiated within
the committee to define a syntax for efficient representation of broadcast video,
or SDTV as it is now known (Standard Definition Television), not to mention the
side benefits: frequent flier miles
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