CD makes milestone in history:

The shiny disc that changed the world

By Pramod DE SILVA

Last night, I decided to wind down with a movie after a hard day’s work. All I had to do was take out a shiny disc that is 12 cm in diameter and pop it in to a player. In just one minute, I was watching Martin Scorsese’s homage to celluloid – Hugo – in gorgeous 3D. As the disc was being read by a laser, I only had to sit back and relax.

Just imagine having over two hours of high definition pictures and 7.1 channels of high definition sound on one small disc. If that is not a marvel of technology, I do not know what is. The first step towards such technological wizardry was taken exactly 30 years ago, when the Compact Disc (CD) was born.

The ubiquitous CD is 30 years this month. Every other disc format that came in the intervening three decades (CD-RW, Video CD, DVD and blu-ray)owes its existence to the humble CD.

The revolutionary idea of an optical disc format read by a laser beam was championed by Dutch electronics giant Philips, which had actually developed a laser-read video system by 1978 (which eventually evolved to LaserDisc) before going the audio-only route. However, that platter was almost the size of a 12-inch vinyl record (LP) and it was felt that such a size would be cost-prohibitive and impractical for musical purposes.

With the advent of digital recording in the late 1970s, a need arose to invent a consumer-oriented medium which could preserve those recordings in the digital format itself, but a smaller, more portable disc was a sine quo non.

Sony of Japan was also developing an optical disc system and before long, both camps realised that two separate, incompatible systems would spell doom for the concept. So they joined forces – Philips already had a viable system by 1980 and Sony worked on an error correction system. Today, the two companies are recognised as the founders of the format that came to be known as the Compact Disc. The name alludes to the size of the disc (12 cm), which can easily be handled with one hand.

A 3D blu-ray disc

A DVD

The first album to be released on CD was Billy Joel’s 52nd Street that reached the market alongside Sony’s first CD player on October 1, 1982 in Japan. It took some months before the format was introduced elsewhere, but by 1985 Dire Straits became the first band to sell a million copies of a CD album. In the past 30 years, billions of audio, data (CD-ROM) and rewritable blank CDs (and millions of CD players) have been sold around the world.

Series of indentations

How does a compact disc work? CD audio or data is stored as a series of tiny indentations known as “pits”, encoded in a spiral track moulded into the top of a polycarbonate layer on the disc. The areas between pits are known as “lands”. Each pit is 100 nm deep by 500 nm wide, and varies from 850 nm to 3.5 nm in length. The distance between the tracks, the pitch, is 1.6 nm.

A CD is read by focusing a 780 nm near infrared semi-conductor laser through the bottom of the polycarbonate layer. The change in height between pits and lands results in a difference in the way the light is reflected. By measuring the intensity change with a photodiode, the data can be read from the disc. It sounds complex, because it is. This is the basis for all other formats based on the Audio CD, though in video variants the pits are much more tightly etched.

An Audio CD can store 80 minutes of stereo (two-channel) music or 700 MB of data. That can look miniscule considering that the tiny SDHC card inserted into my PC can store 32 GB, but the CD has also come a long way in the past 30 years. A blu-ray disc can hold 50 GB of data – enough for (generally) more than four hours of HD video. A blu-ray disc can theoretically carry 32 sound tracks and 250 subtitle tracks. Not bad for a small disc, then.

Though blu-ray is the pinnacle of CD development (for the moment), the CD format saw many breakthroughs in between. One of the most significant was the advent of the once-only recordable CD, followed by the re-recordable CD. Today, you can find dirt-cheap CD recording drives as well as recordable CDs everywhere. To their eternal credit, Sony and Philips refused to let copy protection systems creep into the ‘Red Book’ CD standard and any CD can be copied to another CD or USB device.

The other major advance was digital data compression. This is how engineers first managed to squeeze in one hour of video and audio into a CD, to make it a Video CD (VCD).

The format, although still surviving in our part of the world, was succeeded by Sony’s Digital Versatile Disc (DVD), which is easily the most successful home entertainment format ever (blu-ray is catching up).

A DVD can hold more than three hours of Standard Definition (SD) video, along with up to eight sound tracks and 32 subtitle tracks. DVDs could also contain Dolby and/or DTS surround sound tracks. This was made possible by a ‘dual-layer’ arrangement whereby pits were recorded in two layers.

Sony developed another CD-sized format called Super Audio CD that can contain multichannel surround sound to ‘replace’ the CD, but that never happened. While popular in the audiophile market, most people seem to be happy with the sound of the normal CD. Advances in compression have also led to many video and sound formats such as MP3, AAC, WMA, AVCHD and DiVX being ‘burned’ to CDs (these cannot be played by many older CD players).

True CD quality

However, the humble CD is facing a threat – from the Internet. It is now very easy to download MP3 music tracks legally and illegally from the Web. Why go to the record store and buy a physical disc when you can buy and store it online? In fact, physical sales of CDs are falling.

Although MP3 quality is nowhere near that of true CD quality, many people seem to be having no ear for such refinement. The same argument goes for video, but video requires higher bandwidth and downloading a movie can be a frustrating experience unless you have a very, very fast Net connection.

Although there are many who predict the end of physical media, there will always be a place in consumers’ hearts for them. It will be a long, long way before online equals higher specification audio and blu-ray quality and capacity (additional sound format and language tracks, features, commentaries, subtitles and picture in picture materials).

Besides, engineers have even bigger things in store for the discs, such as 1,000 year durability, 4,000 line resolution video and 11.3 channel sound. I, for one, prefer to hold a CD in my hand and call it my own. Do we own anything in cyberspace? The CD and its descendents will live on for decades to come in our shelves – and in our hearts.