Sony? designed and developed MD in 1986 and launched in 1992. The MD
looks like a small compact disc, the diameter of a CD is 5.25 while that of
an MD is a mere 2.5". Following CD technology, MD technology uses a laser
beam to read the information, but that is where the similarities end.
MDs are magnetically encoded whereas CDs use physical grooves and pits to
indicate the code. Also, MDs are considerably more shock resistant, the 40
second digital buffer system utilized by MD players is far superior to most
portable CD players shock resistant technology.
Sony? emphasizes that MD technology has the best of both audio cassettes and
CDs. Recording mixes on MD is greatly improved over cassettes because MDs
treat music as data computer files that can be manipulated, moved, and
erased. MDs have a Table of Contents (TOC) that indicates which sectors
contain important data, similar to computer hard drives.
Sony? utilized a compression system called ATRAC (Adaptive Transform
Acoustic Coding), which saves space by recording only audible sounds. As a
result, ATRAC has a 5 to 1 compression rate and all the data is able to fit
on the MD. It is said that a substantial amount of clarity is lost with the
ATRAC system. But, outdoors or in a car you'd be hard pressed to tell the
difference.
