Sony MZ-R30 Operating Instructions Manual page 35

How the MiniDisc got so small
The 2.5-inch MiniDisc, encased in a
plastic cartridge that looks like a 3.5-inch
diskette (see illustration below), uses a
new digital audio compression
technology called ATRAC (Adaptive
TRansform Acoustic Coding). To store
more sound in less space, ATRAC extracts
and encodes only those frequency
components actually audible to the
human ear.
Quick Random Access
Like CDs, MDs offer instantaneous
random access to the beginning of any
music track. Premastered MDs are
recorded with location addresses
corresponding to each music selection.
Recordable MDs are manufactured with a
"User TOC Area" to contain the order of
the music. The TOC system is similar to
the "directory management system" of
floppy disks. In other words, starting and
ending addresses for all music tracks
recorded on the disc are stored in this
area. This lets you randomly access the
beginning of any track as soon as you
enter the track number (AMS), as well as
label the location with a track name as
you would a file on a diskette.
User TOC Area
Contains the order and start/end
points of the music.
Music Data
Shock-Resistant Memory
One major drawback of optical read
systems is that they can skip or mute
when subjected to vibration. The MD
system resolves this problem by using a
buffer memory that stores audio data.
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