The Compact Disc - a requirements engineering view

20 October 2007

The recent stories concerning the twenty-fifth anniversary of the compact disc made quite a stir in press and made interesting reading from a requirements engineering point of view.

The disc’s design approach was unusual for those days, being a joint venture between  by Philips and Sony. Both companies started collaboration on the specification of an open standard in 1979 and followed by the manufacture of the first discs in 1982.

The initial design was for a disc that held one hour of stereo music – a figure that subsequently was increased to seventy-four minutes. The reason for this is that the CD was initially targeted at classical music listeners, as this audience was felt to be affluent enough to afford the hefty initial price-tags of £1000 for a player and £15 for a disc. The figure of seventy-four minutes was chosen as this is the length of Beethoven’s Ninth Symphony – one of the most popular pieces in the classical repertoire. So, in engineering parlance, the marketing stakeholders imposed a requirement constraint on the design.

The engineers felt that the original design of an 11cm width was more suited to a compact format; however, this had to be relaxed to 12cm as the data compression demands were too onerous with the smaller format. In engineering terms, this was a trade-off between size and performance requirements.

The CD format was designed to last between twenty and twenty-five years – a requirement that has been well met indeed. Like all long-lasting, well-engineered products, people have found uses for the CD un-imagined by its designers - for example for data distribution and data storage.

Although CDs are starting to be superseded, first by DVD (although noting the same physical size for backwards compatibly – another sign of a successful initial product) downloads and USB memory sticks, it seems safe to assume that CDs will be around for many years yet – one of the most successful electronic products ever.

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