The Milestone of Portable Storage Media
In 70ís VHS (Video Home System) was developed by JVC (Victor Company of Japan Limited) that dominates the video recording market. VHS uses a half-inch wide and 430 meter long magnetic tape to record movies. When CD and VCD were invented VHS tapes lost a large part of its market. CD and VCD use laserdisc technology that makes it smaller and thinner than VHS. When DVD was introduced in 1997, VHS lost its market. DVDs gave consumers the home theater experience that is a major upgrade from magnetic tapes.
DVDs or a digital versatile disk is one of the innovations of the 20th century especially for the entertainment and portable storage industry. DVDs nowadays are everywhere they are used as software storage, high quality movie disc and even private information storage or better known as personal information back-up disk. It can store as much as 4.7 gigabytes of data, that is almost 6 times more than a regular CD and far better than a VHS tape. CDs and DVDs are almost the same on physical attributes and concepts, both are made up of injection-molded piece of clear polycarbonate plastic. The difference is that DVDs has larger data capacity that enables it to store high quality movies with extra features such as subtitles and 5.1 channel Dolby digital surround (almost the same sound in a movie theatre).
Storing data on DVDs is almost the same as storing data on a CD. They are both encoded in the form of small pits and bumps in the tracks of the disc. A DVD is composed of several layers of plastic. Each layer is created by injecting and molding polycarbonate plastic, it creates a microscopic bumps arrange as a continuous and very long spiral track of data (from center to the edge). After the formation of the clear pieces polycarbonate, a thin reflective layer is sputtered onto the disc to cover the bumps. Aluminum is used behind the inner layers and a reflective gold layer is used for the outer layer to allow the laser to focus through the outer and onto the inner layers. After all of the layers are made, each one is coated with lacquer, squeezed together and cured under infrared light.
Movies are encoded onto DVDs using the format that Moving Picture Experts Group established (MPEG). Movies are first encoded to MPEG-2 format and then stored onto the disc that is then decoded by the DVD player upon playing the movie. MPEG-2 encoded movies are capable to be decoded on two standards mainly NTSC (National Television Standards Committee) that shows 30 frames per second and PAL (phase-alternating line) that shows 625 lines per frame at a field rate of 50 fields per second.
Now a new technology is being developed that will replace DVD, the Blue-ray Disc (BD). The BD technology uses blue laser (405 nanometers) that has shorter wave length than red laser (650 nanometers). The shorter the wave length the smaller the beam, the smaller the beam the more precisely it can focus on pits that is twice smaller than the pits of DVD. Because of this, BD can store up to 27 GB of information that is 2 hours of high definition video or about 13 hours of standard video. BD not only has higher capacity but also offers a new level of interactivity. Some of its features is BD user can connect to the internet and download subtitles of their choice and can record one program while watching another on the disc. Blue-ray being a fresh technology cost a lot higher than DVD but manufacturers said that the price will drop to within 10 percent of the price of current DVDs when BD gains popularity. BD can only be played to a BD enable devices. Electronic Manufacturing companies are planning to build BD players that are compatible with both blue and red lasers.
The corporate war for storage media is a never ending research and innovations for humanities need of new innovations.
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