Music consumers entered a new era in the 1980s, when they were first introduced to the digital medium of CDs. On the motion picture side, home consumers were glued to the VHS, i.e. video home system, tape until the 1980s. This was also non-digital but gradually the digital CDs replaced VHS in the late 1980s.
Movie companies were not happy with the CDs that were available and worked on various digital video formats to develop a product that would give improved visual and audio quality to the home consumers. The result was the development of the DVD. The DVD technology originated in the early 1990s and immediately entertainment giants like Time-Warner and Sony realized and agreed to promote the new high quality technology.
DVD stands for digital versatile disc although it is popularly referred to as Digital Video Disc due to popularity in the video industry. The main reason for the popularity and growth of DVDs is that DVD technology allows for the storage of a large amount of data using digital technology.
At present, a DVD offers about 480 lines of resolution, which is double the 20 lines of the VHS format. The 480 lines is best seen on a progressing DVD player which can convert the 40 interlaced video into a 480 line progressive format. The progressive display has a 31.5 kHz or higher scan rate. This eliminates all traces of scan delay and provides a more film-like picture.
DVD technology differs a lot from the CD, even though they are very similar in appearance. A DVD is made of a thin, circular wafer of clear plastic and metal measuring 4.75 inches in diameter with a small hole in the center. The thickness is 0.2 inches and two such discs are compressed together to create a double-sided disc 0.04 inch thick.
The digital data, which consists of the binary language of ones and zeros, is encoded onto a master disc and this master disc is then used to create self-copies. The coping is done by burning small holes, called pits, into a microscopic layer of metal, usually aluminum, with the help of a laser. These pits are the binary ones. Binary zeroes are the smooth surface of the layer of metal, which has not been touched by the metal binary zeros. After this, the metal is coated with a protective transparent layer.
Five physical formats used in DVD Technology
DVD-ROM
It stores general data as well as video and audio information needed for multimedia applications and computer games.
DVD
One of the reasons for the success of DVD technology is the DVD video format. The DVD video application is strongly dependent on data compression since at the bit rate of 167Mbps, the 4 GB capacity of a standard DVD would be enough to store roughly 4 minutes of digital video. This provides for the nominal 133 minutes of playing time for DVD 5.
The DVD 9, which uses dual layer technology, is ideal for longer movies. In this case, the data on the first layer starts at the inside of the disk and end at the outside. The data on the second layer starts on the outside and ends on the inside thus providing uninterrupted playback.
