• DVD (Digital Versatile Disc, or less commonly Digital Video Disc) is an "alternative" to the compact disc (CD) with six times as much storage space.
• The DVD is designed to make data addressable and accessible at random (non-sequentially). It has a complex structure which provides greater interactivity. DVD is plastic discs of 12 cm in diameter and 1.2 mm thick, which are read using a laser beam.
• DVD burners use a red laser with a wavelength of 635 nm or 650 nm. The main reason to use DVDs is their storage capacity, which makes them an excellent medium for video recording.
• A 4.7GB DVD can store more than 2 hours of compressed video in MPEG-2 (Motion Pictures Experts Group), a format used for compressing images while still keeping them high-quality.

Structure of DVD

1. Physical Structure:

• DVDs exist in both single layer and dual layer(DL) versions.
• (DL stands for Dual Layer), also called DVD-R9, is a derivative of the DVD-R format standard. DVD-R DL discs hold 8.5 GB by utilizing two recordable dye layers, each capable of storing a little less than the 4.7 gigabyte (GB) of a single layer disc, almost doubling the total disc capacity.
• The larger capacity formats are not supported by most standalone DVD players, but they can be used with many computer-based DVD drives.
• DVD-R format can be recorded only once, while DVD-RWs can be rewritten up to about 1000 times. Both the formats can store upto 4.7 GB on a disc.
• DVD discs are generally divided in to four families, each with different storage capacities depending on their physical characteristics:

2. Logical structure:

The DVD is essentially made up of three zones, which represent information area,

• Lead-in Area (or LIA for short) only contains data which describes the disc's contents (this information is stored in the Table of Contents). This area lets the DVD player/drive to synchronize itself with the data found in the program area.

• The Program Area is the area which contains the data.

• The Lead-Out Area (or LOA for short) containing null data, marks the end of the DVD.