Have you ever wondered how a full length feature movie plus bonus material fits onto a single DVD Disc? The answer is dual layer DVD technology and you may be surprised to know that this is not new technology we are talking about. Hollywood has been producing major motions pictures on stamped dual layer DVD Discs for years.
We are now witnessing the rise of recordable dual layer DVD technology on the consumer market. A look at the technology could explain this progression.
Dual layer or double layer DVD, also referred to as a DVD-9 disc, appears to be a natural progression of single layer 4.7GB recordable technology. For starters a DVD-9 disc offers up to four hours of high quality MPEG-2 video, or up to 8.5GB of data on a single-sided disc. This mean you can pack up to 12 CD’s worth of information on to one disc. Thanks to the additional layer of recordable space you can store approximately 2,000 songs in MP3 format or up to 17,000 high quality JPEG images.

In a dual layer DVD-9 disc, two individual recordable layers, like the one found on a standard single/ DVD-5 disc, are joined together with a transparent spacer and a thin metal reflector between the two.  The bottom layer is written and read in exactly the same manner as a standard DVD-5.  The difference with a DVD-9 is that the laser now focuses a fraction of a millimetre beyond the first recording layer, giving access to the second recordable layer.  A downside to this is that the layer change can display a noticeable pause in some DVD players, up to several seconds.
Certainly business users will appreciate the increased storage capacity of a dual layer DVD recordable disc especially when distributing a large amount of data on a single disc is needed. It can even be used for desktop system backup and single server backup with time and cost savings over older traditional technologies. IT managers can even create their system “images” for configuring client PCs on a single disc for rapid deployment of new computers on corporate networks.
Independent filmmakers and studios alike will appreciate the ability to author a dual layer DVD video disc and try it out without resorting to expensive and time consuming replication. This set of users can now fine tune their works on cost effective dual layer DVD recordable discs before creating the master for replication.
Dual layer discs are not as common, as the single layer format as the 4.7GB capacity of the single layer discs is usually sufficient for most business uses and dual layer discs are also a lot more expensive.  Also the question of compatible software arises. Typically only newer DVD recorder drives will be able to write to dual layer or double layer discs. Many current DVD recorders support dual-layer technology, and the price is now comparable to that of single-layer drives, though the discs remain more expensive.  However, the recording speeds reached by dual-layer media are still well below those of single-layer media.

BDs - the basics!

So the Blu-Ray disc is here and it seems, with growing sales, that it could well be here to stay! But what are the basics facts you need to know about this disc to stop confusion and to make sure you’re not getting ripped off?
To start with, a basic outline of the disc itself: It’s a disc designed to hold high definition media in particular, best displayed on HDTV screens, but it can also be used for storing computer data. Having been in the works since 2002, the average Blu-Ray disc, or BD, can hold 25GB of information – more than enough for a feature length film! There are also dual layer discs on the market which can hold 50GB but they are rarer and much more expensive. The Blu-Ray disc is called this because, unlike a DVD or a CD, the laser beam which reads the disc is blue-violet and not infrared.
The same as with DVDs, there are different formats of BD for different uses the user may require. Bear in mind that all these formats can be made in either the 25 or 50GB sizes.

BD-ROM: This is the average Blu-Ray that you buy with a film on it. It’s not re-recordable and needs to be manufactured by a professional company.

BD-R: This is a one-time recordable disc which can hold all sorts of different data. You can also burn video onto this at home or professionally.

BD-RE: The same as a BD-R, only this one can be re-recorded onto many times.

BDAV: This is read-only format, the Blu-Ray equivalent of the DVD-Video format. Ot allows for enormous (in fact unnecessarily large) pixel formats: Either 1920×1080 or 1280×720 and uses a progressive scan functioning at 50 or 60 Hz rather than DVD-Video’s 25 or 30Hz. What do all these numbers mean? Basically, it has a killer image – so good that for most households with average sized TVs, it’s quality overkill. Still, it’s worth it for the occasions where massive screens are around and the video just looks perfect!

Manufacturers of BD-ROMs, BD-Rs and BD-REs claim that the discs have a 10-15 year life span and have the strongest content protection which includes strict licensing procedures. (Unfortunately these licensing procedures can seem quite complicated at first – so complex, in fact, that they merit an article all of their own which will be coming shortly!) BDs also ensure the highest HD quality and memory capacity of any disc available. They also use a tough coating which makes the disc slightly resilient against scratches and fingerprints.
So that’s a basic guide to Blu-Ray discs – enjoy watching you’re BDs with their excellent quality and great interactive features!