Compact Discs or CDs, first came to market in 1982, and still remains the main media type on which to store music. CD technology was the first “optical disc” technology that reached widespread acceptance. Laser discs had come before it but had not been widely accepted. A standard CD is 120mm in diameter, can hold around 80 minutes of audio or 700mb of data, is 1.2mm thick, and weighs approximately 16 grams.
A CD consists of four layers:
1. A polycarbonate disc layer where the data is stored
2. A reflective layer which reflects the laser light back
3. A lacquer layer to prevent oxidation
4. An artwork layer, screen printed to the top of the CD
The data is transferred as a series of “pits” and “lands” on the polycarbonate layer of the disc. These pits and lands are a representation of binary data. A transition from a pit to a land or from a land to a pit translates as a one (true) whereas a continuation of a pit or land signifies a zero (false).
CD technology was updated with the release of the “Digital Versatile Disc”, or DVD. DVD is actually the conjoined efforts of two previous technologies, Super density (SD) disc and MultiMedia Compact Disc (MMCD). Rather than participating in a format war, the originators of these two technologies were brought together to agree upon one standard. DVD was the result.
DVD’s main advantage over CD technology is the amount of data the disks can hold. A single-layer, single-sided DVD holds approximately six times the amount of data that a CD holds. DVDs can be dual-layer, which gives them roughly double capacity as a single-layer disk. They can also be double-sided. DVDs used in commercial movie distribution are typically single-sided, dual layer disks. This allows for up to two hours of standard definition video/audio and extra features such as commentary and games.
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DVDs were great as a video medium for many years, but there came a need for higher definition video. Larger screens helped show the lack of quality in standard definition DVD videos. HDTVs started to become more popular, but HDTVs are not very useful unless one has high definition content to play on them. A new type of media was needed. DVD technology wasn’t sufficient enough to store the amount of data needed for standard length high definition audio/video. Two new technologies were developed to replace DVD, HD-DVD and Blu-Ray.
The result was a format war reminiscent of Betamax vs VHS or Laser Disc vs CD. This war delayed the adaptation of either of these technologies for some time. Few wanted to jump on either wagon in fear of the other technology winning. Eventually, however, most adapted the blu-ray format as their standard and on February 19, 2008 Toshiba announced that it would not be developing or manufacturing HD-DVD technology any longer. Since it was the main contributor to the technology, all others followed suit and started to support blu-ray. Blu-ray won the war and now is the standard for high definition audio/video.
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Past formats (CD and DVD) used a red laser to read the pits and lands. Blu-ray uses a blue laser. This is how it gets its name. The blue laser has a shorter wavelength, allowing it to have more precision. This allows for more data to be compacted into the same amount of space. So, while the physical size of the disk is the same as DVDs, it can hold much more data. More data storage is exactly what is needed to deliver high definition audio/video.
The storage capacity of a blu-ray disk also makes it attractive for data storage and gaming technology. One of the earliest adopters of the blu-ray format was Sony. Sony’s Playstation 3 was also one of the first blu-ray devices to reach the mainstream. Many people, especially gamers, bought PS3 game systems because they offered blu-ray playback out of the box.
The price of blu-ray players has dropped dramatically. These players can also play CD and DVD disks. In order to take full advantage of the HD provided by blu-ray disks, one needs an HDTV.
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