Sony RDR-GX7 - Manual (Page 6)

Different types of physical formats
The physical formats of all recordable DVD can be roughly
divided into two categories: the “wobble groove” type which
includes DVD-RW, DVD-R, DVD+RW and DVD+R; and
“wobble land groove” type of DVD-RAM. The disc surface can
be configured with the following types of features: lands
(protrusions), grooves, pits (the recorded points) and wobbles
(snake-like patterns). Lands and grooves are like guides which
enable correct tracking of the laser light beam during recording,
with wobbles used within the land grooves as markers to indicate
the circumference direction.
■ DVD-RW and DVD-R physical format
The physical format of DVD-RW and DVD-R discs uses
wobbled grooves, just like CD-RW and CD-R. Wobbles in the
grooves and breaks in the land areas called land pre-pits (LPP)
are used to perform addressing. Recording pits are only located
in the groove areas. Track pitch is 0.74 microns, the same as
DVD-ROM, with the light reflection ratio of DVD-R roughly the
same as that of DVD-ROM single layer, and the light reflection
ratio of DVD-RW roughly the same as that of DVD-ROM dual
layer. For both discs, physical construction is very close to that
of a playback-only DVD-Video disc.
■ DVD+RW and DVD+R physical format
The physical format of DVD+RW and DVD+R uses wobbled
grooves, just like DVD-RW and DVD-R. Track pitch is also the
same at 0.74 microns. The biggest difference between
DVD+RW/+R and DVD-RW/-R is that the wobbles of
DVD+RW/+R are much finer. This is called a “high frequency
wobble.” The fineness of the wobble is some 37.1 times that of
CD-RW/-R to enable addressing control with much higher
precision since the recording density of DVD is much higher
than that of CD-RW/-R. The use of this high frequency wobble
enables a form of additional data recording technology without
breaks called “loss-less linking.” For random writing common in
PC data recording, loss-less linking reduces the data error
generation ratio. While loss-less linking is specified as a
requirement for the DVD+RW format, it is an option on the
DVD-RW format.
■ DVD-RAM physical format
The physical format of DVD-RAM uses wobbled land and
grooves. Recorded pits are formed on both the land and groove
tracks, while track pitch is slightly smaller at 0.615 microns.
These features differentiate it from the other types of discs
explained in this section. In addition, DVD-RAM also employs
Zoned CLV (Constant Linear Velocity) and an address
information area in the breaks between recorded tracks, making
data distribution completely different from that of playback-only
DVD. Accordingly, special playback equipment is required for
DVD-RAM. For this reason, DVD-RAM is considered a format
in which priority is placed on having a higher number of re-write
cycles, rather than on playback compatibility.
Chapter 2
Features of Recordable
DVD Formats
RDR-GX7 Technical Notes
6
Wobble
Land Groove
Pit
Basic physical construction
of a recordable DVD disc
DVD-ROM DVD-RW/-R DVD+RW/+R
Wobbled Groove Wobbled Land Groove
DVD-RAM
Pit
Track pitch: 0.74
µ
m Track pitch: 0.74
µ
m Track pitch: 0.74
µ
m Track pitch: 0.615
µ
m
land pre-pits
(LPP)
Address
area
"Track pitch is the same, which means high compatibility with DVD players"
Differences in physical construction