Compact Disc
May 5, 2007 – 9:15 pm
Compact Disc – We can’t do without it
Compact Disc – We can’t do without it
It’s unimaginable and unthinkable, the present digital age without a compact disc or CD. Whether we want to listen to music, watch a video, store our memories in a digital photo album, we always turn to this ubiquitous utility tool for all our digital needs. The compact disc hit the commercial market in late 1982; since then it has become an integral part of our lives.
Initially, the concept that compact discs could be used for storing data was not conceived. It was thought of as a gramophone record that was smaller in size. Solely used as a music format in the beginning, it gradually encompassed a huge array of applications. Sony and Philips introduced the newer version of the compact disc known as CD-ROM (Read-Only Memory) in June 1985 and the CD-R (Recordable) in 1990.
The development of CD technology began in 1979 when Philips and Sony set up a task force consisting of their engineers to design a digital audio disc. After intensive research and experimentation for almost a year, the team came up with the standard for compact discs known as the Red Book. Philips played a major role in the manufacturing process by adopting the video laser disc technology and extending the duration and resilience of the disc by using the Eight-to-Fourteen Modulation (EFM) method. Sony, on the other hand, contributed in developing the error correction method in the compact disc.
Ironically, the success of developing the compact disc by Philips and Sony was partly due to the failure of Laservision launched by Philips in 1975. In 1969, Klaas Compaan, a researcher in Philips had suggested the idea of developing optical media for storing pictures. Six years later, the Laservision disc was born. The product became a huge flop and was returned by buyers because it could not record programmes. Within two years Laservision was withdrawn from the market.
The Compact Disc was released in Asian markets in the later part of 1982. In early 1983 it reached other parts of the world including the United States. The first compact disc comprised of 16 Japanese songs released by CBS/Sony. From the initial stage itself, classical music fans and audiophile communities received CD enthusiastically. With the decrease in price of CD players it gained immense popularity worldwide and soon it was used for storing all form of music, videos and data. The personal computer industry is the largest user of CD-ROMs, CD-Rs and CD-RWs (Re-writable) in the world. A mind-boggling 30 billion discs were sold worldwide in the year 2004 alone.
Let’s get into some technical stuff about the compact disc.A compact disc is a digital optical device used for storing digital data. A standard compact disc is made of polycarbonate plastic disc that is 1.2 mm thick and is coated with aluminium to lend it reflective properties. Over the aluminium layer, a thin film of lacquer is added for data protection. Compact discs are of different types like audio CD, video CD, application CD and blank CD. An audio CD is comprised of stereo tracks where audio is stored using the 16-bit PCM coding with a sampling rate of 44.1 kilohertz. A standard audio disc can hold up to 80 minutes of recording. To ensure adaptation to different size formats the digital date in a compact disc proceeds outwards from the center of the disc. CDs are commonly of two sizes, the popular 120mm diameter and the smaller CD known as mini CDs are 80mm in diameter. The 120mm can hold 700 megabytes of data or 80 minutes of audio, while the mini CD can store approximately 180 MB of data or 21 minutes of audio.
According to the compact disc specification issued on September 1983, the main technical parameters of the compact disc were as follows:
• A compact disc should have a scanning velocity of 1.2 – 1.4 m/s. The scanning velocity is the speed at which the disc revolves inside the disk drive. The speed mentioned above is equivalent to 500 rpm or revolution per minute. A compact disc playback or revolution slows down at it played from the beginning to the end.
• It must have a diameter of 120mm
• Thickness should be 1.2mm
• Track pitch should be 1.6 ?m
• Inner radius of the data area in the disc should be 25mm
• Outer radius should be 58mm
• Centre spindle or hole diameter should be 15mm
With the menace of digital piracy rearing its ugly head in recent year, the issue of copy protection has become a critical issue for all digital content providers, manufactures, software companies and all stakeholders involved. Earlier, the Red Book audio specification had no serious mechanism to secure copy protection, but in 2002 some record companies attempted to market copy-protected but non-standard CDs. However, Philips opposed this move and stated that these discs could not be permitted to bear the Compact Disc Digital Audio logo as they violated the Red Book specifications. Consumer too offered their fair share of discontent over copy-protected disc stating that it was a threat to the ideals of fair use. Even though, a variety of copy-protection systems has been adopted, it has not encountered much success. Primarily because, there are many software available to override the protection.
Copy protected or unprotected we cannot survive in the digital age without the friendly, convenient and omnipresent tool known as the compact disc.