DVD Video (Or as it was known Digital Video/Versatile Disc) is a great invention that allows the Movie buying public to spend money buying films they already have on VHS.

A DVD disc itself is a flat piece of shiny silver plastic almost 5 inches across which looks remarkably like a CD.
The main thing it shares with the CD format, apart from the Size, is that you can scratch it without any effort whatsoever. The practical upshot of this is that instead of your Movie collection being chewed up and ruined by your video player, you can ruin it yourself.

However, unlike chewed Videos, scratched DVD's (and CD's too) make excellent
Frisbee's, or Ninja Shrunken.

The Video part of the DVD-Video name is normally dropped, so most of the time you see DVD on packaging, it really means DVD-Video.
This is to confuse consumers when they see other DVD discs with similar names.. Eg.

DVD-Rom (which allows new office "productivity" software (Games) to be distributed on less than 6 discs)
DVD-R (Recordable Once DVD-Rom, Similar to CD-R)
DVD-RAM (Rewritable DVD-Rom)
DVD-RW (Phase-Change erasable, i.e. Rewritable DVD-Rom)
DVD+RW (Phase-Change Rewritable, i.e. Rewritable DVD-Rom)
DVD-Audio (Replacement for Audio CD's)

To confuse matters, the 3 competing rewritable formats are not compatible with each other, or indeed with most current drives. This can be avoided by only using pre recorded discs.


However, to thoroughly confuse matters there are 4 common types of pre-recorded DVD-Video disc, named by the rough amount of data they hold.

DVD-5 Single Sided, Single Layer (About 4.5 Gig)
DVD-9 Single Sided, Double Layer (About 8.5 Gig)
DVD-10 Double Sided, Single Layer (About 9.5 Gig)
DVD-18 Double Sided, Double Layer (About 17 Gig)

Many Double layer discs use a technology called RSDL (Reverse Spiral, Dual Layer) where the second layer is below the first. When the Laser reaches the end of the first layer, it focuses to the inner layer, and scans back towards the centre of the disc.

Most Discs are regionally locked, mainly stop British viewers from having all of the extra features that the USA discs have (Like the film being on only one side of the disc, directors commentaries and other funky things), whilst still ensuring that there is a one to one exchange rate between dollars and pounds.


The regions are

0: No Region Lock
1: Canada, U.S., U.S. Territories
2: Japan, Europe, South Africa, Middle East, Egypt
3: Southeast Asia, East Asia, Hong Kong
4: Australia, New Zealand, Pacific Islands, Central America, Mexico, South America, Caribbean
5: Former Soviet Union, Indian Subcontinent, Africa, North Korea, Mongolia
6: China
7: Reserved (The moon perhaps?)
8: Special international venues (airplanes, cruise ships, etc.)

The paranoia of the Movie industry didn't stop with Region coding. They had to insist on multiple levels of copy protection, particularly to stop perfect digital copies being made. To this end CSS (Content Scrambling System) was put onto the discs which stops people from coping Movie files off the Disc.

The icing on the cake is the analogue copy protection system (Macrovision), which stops you making a VHS copy of a DVD. It works by putting colour bursts into the non picture parts of the TV signal, which confuses the automatic gain controls and synchronization circuits of 95% of video recorders. Unfortunately it can effect some older TV's as well, and also, in some cases, mess up the picture quality.

Manufactures of the DVD-Video machines have learned from past mistakes, and to stop Adults from getting frustrated attempting to program the VCR (Which takes about 5 minutes before they give up, and ask the nearest 5 year old) they just didn't include any recording ability.

Some of the information was found in the
DVD FAQ.