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DVD Physical Specifications
Find out here how DVD discs differ from CDs and how
they contain much more data for a wide range of
applications. |
Please note that the descriptions below represent brief summaries of
the DVD specifications which can be obtained from the DVD Forum.
The DVD technical specifications are contained in five books A to E
published by the DVD Forum.
Book |
Name |
Part 1
Physical |
Part 2 File
System |
Part 3 Appli-
cation |
Ver |
A |
DVD-ROM
|
Read-only |
ISO 9660 + UDF |
undefined |
ver 1.01 |
B |
DVD-Video
|
Read-only |
UDF |
MPEG-2 video |
ver 1.1 |
C |
DVD-Audio
|
Read-only |
UDF |
high quality audio |
ver 1.2 |
D |
DVD-R
|
Write once |
UDF |
not defined |
ver 2.0 |
E |
DVD-RAM
& DVD-RW
|
Rewritable |
UDF |
not defined |
ver
2.0 |
Physical
Parameters
The table below summarises the physical parameters of DVD and compares
them with those of CD and CD-ROM.
Parameter |
CD |
DVD |
Comments |
# layers |
1 |
single |
dual |
see Disc
Formats |
Thickness (mm) |
1.2 |
0.6 |
2 x 0.6 mm |
# sides |
1 |
2 |
DVD substrates bonded |
Track pitch |
1.6 |
0.74 |
microns |
Min pit length |
0.83 |
0.4 |
0.44 |
microns |
Scan velocity |
1.3 |
3.49 |
3.84 |
m/sec |
Wavelength (nm) |
780 |
635/650 |
red laser for DVD |
Numerical aperture |
0.45 |
0.6 |
|
Modulation |
EFM |
8 to 16 |
EFM is 8 to 17 |
Error protection |
CIRC |
RSPC |
Block protection for DVD |
3rd layer ECC |
CD-ROM |
No |
Not needed for DVD |
Subcode/Tracks |
Yes |
No |
Not needed for
DVD |
DVD Sector Structure
The data on a DVD disc are organised as sectors of 2048 bytes plus 12
bytes of header data (see below). Blocks of 16 sectors are error
protected using RSPC RS PC (Reed Solomon Product Code), which is block
oriented and is more suitable for re-writable discs (with packet writing)
than CIRC which does not use a block format. The PI and PO data are parity
bytes calculated horizontally and vertically over the data bytes.

In addition DVD uses an 8 to 16 modulation scheme giving pit lengths of
3 to 14 (minimum to maximum length) compared with CD's 3 to 11 with EFM
modulation. This is only a small difference but does make the jitter
specification slightly tighter.
Burst Cutting Area
The Burst Cutting Area (BCA) is an annular area within the disc hub
where a bar code can be written for additional information such as serial
numbers. The BCA can be written during mastering and will be common for
all discs from that master or, more usually, will be written using a YAG
laser to 'cut' the barcode into the aluminium reflective layer of the
finished disc. The data stored in the BCA can be from 12 bytes to 188
bytes in steps of 16 bytes. The ill-fated Divx format used BCA to uniquely
identify every disc. New uses of this or similar technologies are being
developed to use the BCA as a unique, tamper-proof means of identifying
individual discs.

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