Sony MINIDISC - Manual (Page 7)

What it is and How it Works
A A D D C C D D
A U S T R I A
5
The ease of quick random access was made possi-
ble by the development of the Compact Disc (CD).
The CD instantaneously provides random access to
the beginning of any desired music selection. After
using a CD player, the time to reach the music sel-
ection of your choice with cassette tape players
seems extremely cumbersome.
The MiniDisc provides the same high-speed random
access for recordable discs as well as for premaste-
red discs. In addition, the recordable MiniDisc has a
circumferential microgroove or ”pre-groove”, which
is formed when the polycarbonate substrate is injec-
tion molded. This pre-groove is the basis for the
tracking servo and spindle servo operation during
recording or playback.
Address information is recorded at intervals of 13.3
milliseconds using a technology that places infinite-
simal zigzags on this pre-groove. Therefore, the
disc has all the addresses already notched along the
groove even with no recording. The result is a stable and quick random access, as well as a variety
of optional features, including programming of
the playback sequence e.g.: rearranging the
sequence of the titles recorded on the MD without
rerecording of the music information in a matter of
seconds.
This is possible because of the “User TOC Area”,
located around the inner edge of the microgroove,
which only contains the order of the music. This
system is similar to the “directory management
system” of floppy discs. In other words, starting
and ending addresses for all music tracks recorded
on the disc are stored in this area, enabling easy
programming just by rewriting the addresses. This
supports also other features: it is possible to erase
a track out of a sequence and during playback no
gap in the remaining music will be heard. The era-
sed segment is allocated to the free space – it is
possible to record a piece of music independent of
the number of segments used.
Quick Random Access
Lead in 1 2 3 4 Lead out
A B C D E F G H Inner Edge Outer Edge
Disc Signal
Lead in 1 2 3 Lead out
A: Before Rearranging
B: After Rearranging
Music Data and Order are Recorded Time-Wise
1. Ordinary Method:
Rearranged Area
Lead in UTOC Only Music Data is Recorded Lead out
1
2
3
4
UTOC Data TNO START STOP
A
C
E
G
B
D
F
H
Disc Signal
2. MiniDisc:
Music Data and Order are Recorded Area-Wise A: Before Rearranging
Lead in UTOC Only Music Data is Recorded Lead out
1
2
3
UTOC Data TNO START STOP
A
E
G
D
F
H
Rearranged Area
Connecting two Tracks:
B: After Rearranging (No Change of Music Data)
Additional Reprogramming the Order:
1
2
3
TNO START STOP
A
G
E
D
H
F
Reprogramming the
Order of Music