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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.
This offers the possibility of discs with up to two sides and up to two
layers offering four possible
read-only formats:
| Name
|
Capacity (GB) |
Layers |
Sides |
Comments |
| DVD-5 |
4.7 |
1 |
1 |
Single side/layer |
| DVD-9 |
8.54 |
2 |
1 |
Dual layer |
| DVD-10 |
9.4 |
1 |
2 |
Double sided |
| DVD-18* |
17.08 |
2 |
2 |
Dual layer/side |
*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.
Note that 1 GB = 1,000,000,000 bytes.
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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"each DVD comprises two substrates each 0.6mm thick
and bonded together"
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