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DVD FAQ

These may be some of the most simple, but commonly asked questions about the DVD medium.

  1. Why Are DVD's Gold?
    Most DVD's are gold because they contain two layers of disc surface. These DVD's (Dual Layer/Single Sided) are called DVD-9, they hold all the data on one side of the disc in two layers. The gold appearance is due to the first layers metal. Most DVD's first layer (closet to the centre) have a aluminum layer for the data, these DVD-9's have two layers, so the second layer is made with a semitransparent layer so the DVD player can focus to either layer.
  2. Why are some DVD's dual sided?
    Some DVDs which are double sided are of the earlier generation. These are DVD-10, DVD-14 or DVD-18, depending whether they are single sided, mixed layers, or dual layers on either side. Older DVD's such as new ones which first came out were single sided single layers, and didn't have a very good picture quality because of the lack of space.
  3. How Much Data can a DVD Hold?
    Standard DVD-9 discs which have two layers on one side are roughly 9.37Gb in size. The single layer discs (DVD-5) are only 4.7Gb. The reason the DVD-9 discs are slightly smaller than twice the DVD-5, is that at the end of the disc the DVD player must be able to realign to the other layer, that is, have enough space to get to it, in this way it eats up less than a mm on the disc but a whole 30Mb.
  4. How much video can you fit on a DVD?
    Well for the various discs it usually has around 2 hours of normal compression video for a single layer. That means a DVD-5 (Single Layer Single Side) has over two hours, a DVD-9 has twice that of approximately 4 hours. While the DVD-10s have 4.5 hours, and anything up to 8 hours if you have two layers and two sides on DVD-18.
  5. How Are DVD's Different To CD's?
    CD's use tracks of data which stretch for over 33 miles around the disc. DVD's have, quite simply, smaller tracks. No-one has published a length of the tracks as yet. These smaller tracks require a finer laser assembly, but the amount of data which can be taken at once is much higher.
  6. What are DVD-ROMs?
    DVD Roms are the equivalent of a CD-ROM to a CD. These DVD-ROMs are basically the same disc, in that you can have dual layer, single sided, single layer double sided etc, but they have much more complex things on them which a computer or games console can understand. Basically you can hold files and folders on them. The amount of data is the same.
  7. Are DVD's More Robust That CD's?
    Yes and no. You see DVD's are made from (usually) two layers, in that, they are glued together in the development process, this means if you bend them or something, they could separate, this could damage one of the layers. On the other hand if you scratched the top edge of the disc (label side) you will only be damaging the top layer, the other layer will probably be still usable.


 

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