Audio, technically wise, comprises three parameters: the media, the media recorder and the media player. In the past the fabrication of media involved a huge capital investment, so the media had to be fabricated for many years for the investment to pay back its money. So we stayed with the far-from-ideal vinyl for many decades. During that time, great talent and resources were invested in producing instruments that played this media from reasonably well to outstanding.
The advent of compact disc introduced enormous reductions in the economy of scale of both media and media player fabrication. You only have to keep in mind the reduction in size and weight of both media and player to understand it. Yet the compact disc, even from its conception, was suffering from many limitations.
The most important limitation as far as the sound quality is concerned had to do with the sampling rate of digitalization of the sound. What all electrical engineers learn at college is the sampling theorem (by Shannon) which states the following:
A real-valued band-limited signal having no spectral components above a frequency of B Hz is determined uniquely by its values at uniform intervals spaced no greater than 1/(2B) seconds apart.
Translating the above rule to a form that non-engineers audio enthousiasts understand, it means since the human ear can listen from 0-22 kHz we have to sample each analogue recording with at least 44 KHz. For the rule to be valid imagine that we are talking here about a 44-kHz sampler made from perfect components. Well, the compact disc by design was sampling at 44.1 kHz (that is 100 Hz tolerance). But this safe limit was very small. One had to make an ideal conversion from analogue to digital and vice versa, and had to employ extremely sophisticated techniques - packed in equally extremely expensive media players/recorders.
As the time going by is also reduced, and the data in our digital systems increases at an exponential rate, the relative storage capacity of the CD player is reduced by an exponential rate also.
Shall we also add the limitation of the CD to be re-writable?
All the above considerations produced the DVD. A brand new media, DVD combines the strengths of the CD while resolving almost all of its weaknesses.
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