Digital Versatile Disk

DVD is high-capacity optical media technology. Its physical size is the same of regular CDs. It can be used for video, audio and data storage.

Its higher storage capacity over a regular CD comes from a higher number of tracks, the use of more than one layer and more than one recording side.

DVD disc types and capacities are summarized below:

• DVD5: 4.7 GB, 133 minutes of video (one layer, one side)
• DVD9: 8.5 GB, 240 minutes of video (two layers, one side)
• DVD10: 9.4 GB, 266 minutes of video (one layer, two sides)
• DVD18: 17 GB, 480 minutes of video (two layers, two sides)

In order to read the second layer, DVD players optical unit changes its laser beam focus. When playing videos you may see a small pause when the optical unit changes from one layer to the other. In order to read both sides of the disc, the DVD player must have two optical units. Otherwise you need to manually flip the disc.

DVDs are coded into six regional areas for market reasons. In theory a title released for one area cannot be played by a DVD player from another area (you can easily break this limitation by entering a manufacturer code). These areas are:

• Area 1: USA and Canada.
• Area 2: Japan, Europe, South Africa, Middle East and Egypt.
• Area 3: East and Southwest of Asia.
• Area 4: Oceania, Central America, South America, Mexico and Caribbean.
• Area 5: Countries from the former Soviet Union, Africa, North Korea and Mongolia.
• Area 6: China.
• Area 7: Reserved.
• Area 8: Airplanes on international flights.

Movies are recorded on DVD using a data-loss compression algorithm called MPEG-2. Since it is a data-loss algorithm, this means that its quality in not the same as if the video was recorded uncompressed.