To anyone but the most militant Luddite, the digital onslaught should come as no surprise.

Where once we had vinyl records, now we enjoy (digital) compact discs; supermarkets used to stick a price on every tin of beans, now they use (digital) bar codes; far-flung friends who used to write letters now exchange (digital) e-mails.

	Exactly what do you get? Digital Q&A Freeing up the bandwidth The technology: pros/cons

Digital television, and its lesser-known cousin, digital radio, are simply the latest technological innovations in a top-down push towards a seemingly better future.

But what makes digital TV better than the loveable "gogglebox" that has come to grace almost every living room in the western world?

In terms of television, "digital" relates to the way programmes are processed and transmitted.

Until recently, television was based solely on analogue technology, which converts sound and pictures into waves.

The waves are transmitted through the air and picked up by a viewer's rooftop or indoor aerial.

Noughts and ones

Digital television converts the pictures and sound into a string of binary digits (ones and noughts) which are transmitted through modified transmitters and again received by an aerial or satellite dish, or just sent down a cable.

This has a number of effects:

Digital signals are more efficient than analogue, so six channels can be broadcast on the same frequency that would carry just one analogue channel.

Each frequency is called a multiplex. There are six terrestrial multiplexes available, which makes for a possible 36 separate channels.

At the viewer's end, a decoder is needed to breakdown the binary transmission and build it into a television picture with sound.

Broadcasters and service providers stress that digital television not only means more programmes, but also a better quality picture. There is no "ghosting" but, contrary to some reports, digital does not mean trouble-free viewing in the future.

A report earlier this year by the consumer magazine Which? highlighted several problems with digital picture quality.

The root of the problem is compression, the process of squeezing transmission information so it travels faster and can be decoded quicker.

Taking out information

Compressing a picture means taking out any bit of the transmission that remains the same from one "frame" to another. For example, the static court in a tennis rally - all that moves are the players and the ball.

However, says Martin Cook of the Digital TV Group, a highly complicated picture, such as when a camera pans, at distance and high speed, across the faces of a football crowd, could be more troublesome.

The result for the viewer is a jerky motion or a blocky picture. Sometimes the picture can just black out.

Compressing too much information into one multiplex - broadcasting several "complicated" programmes at the same time, can also be a recipe for poor picture quality.

Some service providers use a technique called statistical multiplexing, to get round this. It means "complicated" pictures muscling in on the bandwidth of less complex transmissions.

"Inevitably there could be times when there's so much data going through, [the decoder] is struggling," said Mr Cook.

Improved sound is not necessarily a given, either, since existing terrestrial Nicam sound is already digital.

And while widescreen televisions deliver a superior picture quality to the standard 4:3 format, they are still the exception.

"Digital TV uses the same picture quality as a current TV set - it's just the receiver that will be different," said Which? in its April report.

Difference only subtle

"So the picture quality will still be limited by the number of lines on the screen (currently 625) and the number of times the screen is updated."

Overall, Mr Cook says the difference to the viewer is subtle, but digital comes out better.

Which? researchers were more circumspect, concluding that unless viewers live in an area with poor analogue reception, they are unlikely to notice any difference in picture quality.

So while digital television is certainly here to stay, it's not to everyone's satisfaction. Does anyone remember the phenomenon of the digital watch?