Editing Optical disc (section)

===First-generation===
From the start optical discs were used to store broadcast-quality analog video, and later digital media such as music or computer software. The [[LaserDisc]] format stored [[analog video]] signals for the distribution of [[home video]], but commercially lost to the [[VHS]] [[Videocassette#Cassette formats|videocassette]] format, due mainly to its high cost and non-re-recordability; other first-generation disc formats were designed only to store digital data and were not initially capable of use as a [[digital video]] medium.

Most first-generation disc devices had an infrared laser reading head. The minimum size of the laser spot is proportional to the [[wavelength]] of the laser, so wavelength is a limiting factor upon the amount of information that can be stored in a given physical area on the disc. The infrared range is beyond the long-wavelength end of the visible light spectrum, so it supports less density than shorter-wavelength visible light. One example of high-density data storage capacity, achieved with an infrared laser, is 700&nbsp;MB of net user data for a 12&nbsp;cm compact disc.

Other factors that affect data storage density include: the existence of multiple layers of data on the disc, the method of rotation ([[Constant linear velocity]] (CLV), [[Constant angular velocity]] (CAV), or zoned-CAV), the composition of lands and pits, and how much margin is unused is at the center and the edge of the disc.

Types of Optical Discs:
* [[Compact disc]] (CD) and derivatives
** [[Compact Disc Digital Audio|Audio CD]]
** [[Video CD]] (VCD)
** [[Super Video CD]]
** [[CD Video]]
** [[CD-Interactive]]
* [[LaserDisc]]
* [[GD-ROM]]
* [[Phase-change Dual]]
* [[Double Density Compact Disc]] (DDCD)
* [[Magneto-optical disc]]
* [[MiniDisc]] (MD)
** [[MD Data]]
* [[Write Once Read Many]] (WORM)

====Laserdisc====
In the [[Netherlands]] in 1969, [[Philips]] Research [[physicist]], Pieter Kramer invented an optical [[videodisc]] in reflective mode with a protective layer read by a focused [[laser]] beam {{US Patent|5,068,846}}, filed 1972, issued 1991. Kramer's physical format is used in all optical discs. 

In 1975, Philips and MCA began to work together, and in 1978, commercially much too late, they presented their long-awaited [[Laserdisc]] in [[Atlanta]]. MCA delivered the discs and Philips the players. However, the presentation was a commercial failure, and the cooperation ended.

In Japan and the U.S., [[Pioneer Corporation|Pioneer]] succeeded with the Laserdisc until the advent of the DVD. In 1979, Philips and [[Sony]], in consortium, successfully developed the [[audio compact disc]].

====WORM drive====

In 1979, Exxon STAR Systems in Pasadena, CA built a computer controlled WORM drive that utilized thin film coatings of Tellurium and Selenium on a 12" diameter glass disk. The recording system utilized blue light at 457&nbsp;nm to record and red light at 632.8&nbsp;nm to read. STAR Systems was bought by Storage Technology Corporation (STC) in 1981 and moved to Boulder, CO. Development of the WORM technology was continued using 14" diameter aluminum substrates. Beta testing of the disk drives, originally labeled the Laser Storage Drive 2000 (LSD-2000), was only moderately successful. Many of the disks were shipped to RCA Laboratories (now David Sarnoff Research Center) to be used in the Library of Congress archiving efforts. The STC disks utilized a sealed cartridge with an optical window for protection {{US Patent|4,542,495}}.

====CD-ROM====

The [[CD-ROM]] format was developed by Sony and [[Philips]], introduced in 1984, as an extension of [[Compact Disc Digital Audio]] and adapted to hold any form of digital data. The same year, Sony demonstrated a [[LaserDisc]] data storage format, with a larger data capacity of 3.28&nbsp;GB.<ref>[https://www.youtube.com/watch?v=rbh1XP4kCT4 Japanese PCs (1984)] {{Webarchive|url=https://web.archive.org/web/20170707091011/https://www.youtube.com/watch?v=rbh1XP4kCT4 |date=2017-07-07 }} (14:24), ''[[Computer Chronicles]]''</ref>

In the late 1980s and early 1990s, Optex, Inc. of Rockville, MD, built an erasable optical digital video disc system {{US Patent|5,113,387}} using Electron Trapping Optical Media (ETOM){{US Patent|5,128,849}}. Although this technology was written up in Video Pro Magazine's December 1994 issue promising "the death of the tape", it was never marketed.

Magnetic disks found limited applications in storing the data in large amount. So, there was the need of finding some more data storing techniques. As a result, it was found that by using optical means large data storing devices can be made that in turn gave rise to the optical discs. The very first application of this kind was the compact disc (CD), which was used in audio systems.

Sony and Philips developed the first generation of the CDs in the mid-1980s with the complete specifications for these devices. With the help of this kind of technology the possibility of representing the analog signal into digital signal was exploited to a great level. For this purpose, the 16-bit samples of the analog signal were taken at the rate of [[44,100 Hz|44,100 samples per second]]. This sample rate was based on the [[Nyquist rate]] of 40,000 samples per second required to capture the audible frequency range to 20&nbsp;kHz without aliasing, with an additional tolerance to allow the use of less-than-perfect analog audio pre-filters to remove any higher frequencies.<ref>Hass, J. ''Introduction to Computer Music'', Indiana University CECM (retrieved 8 October 2014), Volume One, Chapter Five: Digital Audio.{{cite web|title=Chapter Five: Principles of Digital Audio|url=http://www.indiana.edu/~emusic/etext/digital_audio/chapter5_rate.shtml|url-status=dead|archive-url=https://web.archive.org/web/20140608134439/http://www.indiana.edu/%7Eemusic/etext/digital_audio/chapter5_rate.shtml|archive-date=2014-06-08|access-date=2014-10-08}}</ref> The first version of the standard allowed up to 74 minutes of music or 650&nbsp;MB of data storage.