contains the information layer 0.6 Millimeter (mm) from the surface DVD DVD’s are constructed of two half-thickness discs bonded together, even when only one surface contains information. Each half disc contains the information layer 0.6 Millimeter (mm) from the surface DVD DVD’s are constructed of two half-thickness discs bonded together, even when only one surface contains information. Each half disc contains the information layer 0.6 Millimeter (mm) from the surface
Reading
Starts From Center
Inside Out---
Outside to Inward
Types
CD-R
The dye layer can be written to once.
■ CD-ROM
The reflector has the information manufactured into it and
there is no dye layer.
■ CD-RW
The dye is replaced with multiple layers of different metallic alloys. The alloy is bi-stable and can be changed many times between
different states.
DVD DVD’s are constructed of two half-thickness discs bonded
together, even when only one surface contains information. Each half
disc contains the information layer 0.6 Millimeter (mm) from the surface
of the disc.
--------------------------
The bottom of a CD is made of a relatively thick piece of polycarbonate
plastic. Alternatively, the top is protected by a thin coat of lacquer. Scratches
on the polycarbonate are out of focus when the disc is read, and minor
scratches are ignored completely
A DVD has polycarbonate on both sides; therefore, it is difficult to scratch
the reflector.
Sensitive to
Heat
Light
Speed RPM
---5000
---5000
Dye
CD
The first CD-R manufacturer,
Taiyo Yuden, met this requirement by developing and patenting a cyanine
organic dye
Dye
Patent
Color
Reflector Colour
Cyanine
Taiyo Yuden
Blue
Green
Phthalo-Cyanine
Mitsui Toatsu
Transparent
Gold
Metalized AZO
Mitsubishi
Blue
Dark Blue
Advanced Phthalo-Cyanine
Mitsui Toatsu
Transparent
Gold
Formazan
Kodak Japan
Light Green
Green/ Gold
Recommendations
· If the data has value after six months, using rewritable media is not recommended.
· Transferring data from one computer to another or short-term
· backups are ideal uses for rewritable media.
For DvD
the dye formulations are not usually disclosed by the manufacturers.
While CD-R technology was jointly shared between Sony, Philips, and Taiyo Yuden in the early 1990s, the recordable media market has become far more competitive. Today, a small change in dye formulation can make a difference in writing speed or other performance characteristics, and therefore are of significant benefit to media manufacturers.
The result is that there is less sharing of information about DVD dyes than there is for CD-R dyes.
Recommad
DVD R and RW
DVD-R discs are often the best choice for compatibility if the disc being
produced contains data files. Early DVD-ROM drives can generally read
DVD-R discs but are incapable of reading DVD+R discs. DVD writers that
only write DVD+R/RW discs will read DVD-R discs.
History
CD
· COLOUR
When CD-R discs originally appeared, the reflector was always gold and
the dye added a greenish cast to the data side (or bottom) of the disc.
However, today CD-R discs can be found with silver or gold reflectors and various dye colors that give the data side of the CD-R disc anything from a green tint to a yellow tint to a blue tint and various other shades of these colors.
The specific colors are dependent on the dye formulation being used. There are a number of different dyes and many possible changes in exact formulation that give rise to the number of different colors
---CD-RW discs generally have a silver reflector and a dull silver data side
· Development
The first CD-R manufacturer is Taiyo Yuden, met this requirement by developing and patenting a cyanine organic dye
CD-R technology began in the early
1990s and Sony released the first CD recorder in 1993.
History
DvD
· Colour
DVD-R discs originally had a silver reflector and a purplish tint on the
data side.Today, DVD-R and DVD+R discs come in a wide variety of colors with different dye formulations. Nearly all of the reflectors for DVD-R and DVD+R are silver.
DVD-RW discs appear similar to CD-RW discs, with a silver reflector and a dull silver data side.
www.syngress.
Recording
Technology
· Data
Recordable media replaces physical pits with organic dye that can be made to be opaque (or less transparent) by the application of heat.
When a disc is read, the transitions between lands and pits and pits to
lands are represented as binary. The spacing between these transitions serves to fill in binary zeros between the 1s and is represented by the length of a pit.
Border Zone is the area on a DVD that contains the real content of the disc,
whether it is data files, music, or videos. It is roughly equivalent to a track on
a CD.
www.syngress.com
A manufactured DVD is always composed of a single border zone; however,
recordable discs can have multiple border zones. In some documentation,
a border zone is also called a RZone.
· Writing
Lead In
The lead in serves as a container for the TOC for a session on a CD. Sonystyle
CD Text information is also recorded in this area. Originally, this was
used to help calibrate the laser and mechanical components of the drive for reading the disc.
The first (or only) session on a disc has 7,500 sectors (14.65MB) reserved
for the lead in; subsequent sessions have 4,500 sectors (9 MB) reserved for the lead in. Using “Disc At Once” recording the TOC and other lead-in information is written first in this area, whereas using “Track At Once” recording in this area is reserved and written after the session is closed.
For multi-session recording, a pointer is placed in the lead-in area to indicate the next writable location on the disc. If and when the disc is finalized or closed, this pointer is recorded as either 0 or 24 bits of binary 1s. Both formats have the same effect of preventing further information from being added to the disc.
Lead Out
The lead out of the disc indicates the end of the CD disc or the end of a session on the disc. One use of the lead-out area is to tell an audio player to stop Playing the disc.
This area is made up of a group of sectors written at the end of the disc.
The lead out for the first session is 6,750 sectors (13.5 MB) and all subsequent sessions have a lead-out of 2,250 sectors (4MB).
Share This Post
