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DVD
Disc Layout
& Formats
DVD discs come in a range of different physical
formats with capacities from 4.7 GB to 17.1 GB |
DVD discs have the same physical dimensions as CDs, but each DVD
comprises two substrates each 0.6mm thick and bonded together like a sandwich.
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This offers the possibility of discs with up to two sides and up to two
layers offering four possible
read-only formats plus recordable and rewritable formats:
|
Name
|
Capacity (GB) |
Layers |
Sides |
Comments |
| DVD-5 |
4.7 |
1 |
1 |
Read from one side only |
| DVD-9 |
8.54 |
2 |
1 |
Read from one side only |
| DVD-10 |
9.4 |
1 |
2 |
Read from both sides |
| DVD-18* |
17.08 |
2 |
2 |
4 layers, read from both sides |
| DVD-R |
4.7/9.4 |
1 |
1 or 2 |
Recordable DVD |
| DVD-RAM |
2.6/5.2 |
1 |
1 or 2 |
Rewritable DVD |
| DVD-RW |
4.7 |
1 |
1 or 2 |
Re-Recordable DVD |
*DVD-18 is difficult to manufacture
and, as it is a double-sided format, there is little room for a label and
the disc needs to be turned over to play both sides.
- DVD Disc Layout
- Each layer of a DVD disc contains lead-in, data area and lead-out
like a CD. For dual layer (DVD-9) discs
the two layers comprise a single volume, but can be organised in two
different ways depending on the application:
- Parallel Track Path PTP), where the two layers both start
at the inside diameter (ID) and end at the OD with the
lead-out. This is suitable for DVD-ROM.
- Opposite Track Path (OTP), where layer 0 starts at the ID
and layer 1 starts where layer 0 ends. For such discs there is one
lead-in (on layer 0), one lead-out (on layer 1) and two middle
areas. This is suitable for DVD-Video where a single movie can
occupy both layers with a layer break in the middle. Using OTP
allows a near seamless jump from layer 0 to layer 1.
These layouts for single and dual layer discs are illustrated below.
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DVD-5 (4.7GB)
Single Sided/Single Layer
![DVD 5 Construction]()
This is the simplest of the family of DVD discs, comprising
a single layer with a capacity of 4.7GB. Only one of the two 0.6mm substrates contains
data, the other being a blank disc. The two substrates are bonded together to form a 1.2mm
thick disc.
Single sided discs can be printed on by any conventional
method eg screen printing. Alternatively, the blank substrate can be moulded with an image
in its surface and then metalised to make it visible.
DVD-9 (8.5GB)
Single Sided/Dual Layer
![DVD 9 Construction]()
This dual-layer, single sided version has a capacity of
8.5GB which is slightly less than twice the single layer version, to make it easier for
the second layer to be read. Pits on both layers are 10 per cent longer than on a DVD-5 or
DVD-10 disc.
Each layer is moulded in one substrate, the two substrates
being joined with an optically transparent bonding layer. These discs can be printed after
bonding in the conventional way.
DVD-10 (9.4GB)
Double Sided/Single Layer
![DVD 10 Construction]()
This disc comprises two sides each single layer. It differs
from the DVD-5 version in that both substrates contain data. To read both sides the disc
will need to be turned over for most DVD players/readers. The capacity is 9.4GB, twice the
single side/single layer version.
Double sided discs cannot be printed except on the hub
inside the lead-in area. Labelling is therefore a problem with such discs.
DVD-18
(17.1GB) Double Sided/Dual Layer
![DVD 17 Construction]()
This version comprises two sides each with a dual layer
format. Both layers of each side must be manufactured on a single polycarbonate substrate. It has the largest capacity of the family but is the
most difficult and complex to manufacture. Four stampers are needed to
create the four layers.
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