Dual Layer Double Sided DVDs Explained
Some people may get confused when DVDs are described as dual layer, double layer, and double sided. Let's clear up what these terms mean.
Dual Layer and Double Layer (DL) DVDs
Like the name implies, dual layer DVDs and double layer DVDs have digital information on two layers. Dual layer and double layer DVDs are essentially the same thing, and frequently the terms are used interchangeably. However, in a technically accurate sense, the term “dual layer” is associated with DVD -R DL blank DVDs while “double layer” is used for the more common DVD +R DL blank DVDs. For convenience and clarity we will refer to them as double layer DVDs, but the information applies to both double layer and dual layer DVDs.
As described, double layer DVDs have two layers of data. The second layer is optically transparent so the lower (or first) layer can still be seen by the reading/writing laser. Double layers provide almost twice the storage capability of regular DVDs. Standard DVDs have a capacity of about 4.7 Gbytes (known as DVD-5) but double layer DVDs have about 8.5 Gbytes of storage. (Although these numbers are not technically accurate, they are the standard numbers used in reference to DVDs.) In terms of video, that is two hours of standard video versus four hours of standard video.
Blank double layer DVDs always have “DL” after the format designation on the label (i.e. DVD +R DL).
Playing Double Layer DVDs
Most purchased movie DVDs, for example, are double layer DVDs, as are games, software applications, etc. Any movie more than two hours long wouldn't fit on a regular DVD - even in standard video format. Imagine having to put in a new DVD halfway through the movie. Plus, a movie producer or a software company being able to deliver one disc instead of two is a benefit to everyone.
Accordingly, virtually every DVD drive and player is capable of playing or reading double layer DVDs. Only the very earliest generation of DVD players might not be able to play double layer DVDs.
Burning Blank Double Layer DVDs
Burning or duplicating double layer DVDs is another matter. Currently, most computer DVD drives or component DVD recorders are not capable of burning or recording on double layers. This is true for duplicators as well. However, double layer capable drives and duplicators are available.
If you are unsure if your computer has a double layer (or dual layer) burning capable drive, first check the drive to see what the labels say. If it has a label with a DL, then it is probably double layer capable. (Be sure to use the right blank media format!) If it doesn’t have DL on the labels then it can probably only burn standard DVDs. If you are still unsure, right click the DVD Drive icon in the Start -> Computer window. Then select Properties and you will see the manufacturer and model number. Now you should easily be able to find if your drive is DL capable by looking for specifications for it on-line.
Double Sided DVDs
Once again, the name is a give away. Double sided DVDs have digital information recorded on both sides of the disc. These are a bit more uncommon than double layer DVDs. Double sided DVDs are just like standard or double layer DVDS, but both sides of the disc are used instead of one. A common use of double sided DVDs is to include two different formats of a movie on one disc: letter box on one side and pan & scan on the other. Some really long movies might use a double side DVD instead of using 2 discs.
You may encounter double sided DVDs in other instances as well - like when installing large applications. It doesn't take a special player to read double sided DVDs. It just requires turning the DVD over. As described, both sides are like a normal DVD.
The biggest issue with double sided DVDs is that, with both sides of the disc employed, handling and storage becomes an even larger concern. It is hard enough to keep discs in pristine condition with an unrecorded side to handle it by. Now you have to try not to touch, scratch, or scrape either side.
That covers the basic information about double layer (or dual layer) and double sided (or dual sided) DVDs. Now when someone uses one of these terms when discussing digital discs, you will know exactly what they are talking about.
Updated 6/3 2011 by SuperMediaStore Staff