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Category Archives: Information Technology

CD / DVD Terminology

CD / DVD Terminology

CD / DVD Terminology, (What are Different kinds of Disks and their technical specifications)

Below, you’ll find the most common terminology that

relates to CD duplications. Even if you are new to

duplication, the terms below may help you understand more.

BLER

Block Error Rate. This is the raw digital error rate

before any type of error correction.

CD

This the Compact Disc, a digital medium that’s formed

of a 12cm polycarbonate substrate, a reflective

metalized layer, and a protective lacquer coating.

CD-R

Compact Disc-Recordable. The term CD-R is used to

describe the technology of recordable CD along with

the equipment, software, and media that are used to

make the recordable disks.

Data layer

With CD-R media, this is the organic dye that is

sandwiched between the polycarbonate substrate and

the metalized reflective layer of the media. CD-R

disks don’t have any data on them at all until the

are recorded.

Injection Molding

This is a manufacturing method where the molten

material is forced into a mold, normally under

high pressure, then cooled so that the material

will take on the shape of a mirror image in the

mold.

Media or blanks

CD-R media are the disks that are used to record

digital information using a special recorder and

premastering software with a computer. These discs

are made of a polycarbonate substrate, a layer of

organic dye, a metalized reflective layer, and a

coating of lacquer for protection.

Organic dye

The data layer of CD-R media is made from a dye

that is melted during the process of recording.

Where the dye is melted, becomes opaque or

refractive, scattering the reading laser so that

it isn’t reflected back into the reading sensors.

Reflective layer

This is the metal later that sits on top of the

dye that reflects the laser beam back to the

reading assembly. This is normally 24k gold in

CD-R disks, although it can be silver as well.

 

Differences Between CD DVD

Differences Between CD DVD Media

Differences Between CD DVD

Even though both CD and DVD disks have the same

media size and shape, the things they have in

common ends there. There are many different

things between the two, such as what they hold

and how much they hold.

Data pits and lasers

A disc has microscopic grooves that will move

along in a spiral around the disc. CDs and

DVDs both have these grooves, with laser breams

applied to scan these very grooves.

As you may know, digital information is represented

in ones and zeroes. Inside of these discs, very

tiny reflective bumps known as lands and non

reflective holes known as pits, which can be

found beside the grooves, reflect both the ones

and the zeroes of digital information.

By reducing the wave length of the laser to 625mm

or more infrared light, DVD technology has

managed to write in smaller pits when compared

to the standard technology of CD. This will

allow for a greater amount of data per track

on the DVD. The minimum length allowed for a

pit in a single layer DVD-R is .4 micron, which

is obviously more than the .0834 micron that a

CD offers.

The tracks of a DVD are narrower as well, which

allows for more tracks per disc, which also

translates into more capacity than a CD. The

avaerage single layer DVD holds 4.5 GB of data,

while a CD holds a mere 700 MB.

Layers

As stated above, a DVD has smaller pits and the

lasers need to focus on them. This is actually

achieved by using a thinner plastic substrate

than in a CD, which means that the laser needs

to pass through a thinner layer, with less

depth to reach the pits. It’s this reduction in

thickness that’s responsible for the discs

that were only 0.6mm thickness – which is half

that of a CD.

Data access speed

DVDs will access data at a much faster rate than

a CD can. The average 32X CD-ROM drive reads

data at 4MB a second, while a 1X DVD drive reads

at 1.38MB a second. This is even faster than

an 8X CD drive.

Universal data format

The recording formats of CDs and DVDs are quite

different, as DVDs use UDF, or the Universal

Data Format. This format allows data, video,

audio, or even a combination of all three to

be stored in a single file structure. The

advantage to this is any file can be accessed

by any drive, computer, or even consumer video.

CDs on the other hand aren’t compatible with

this format.

 

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