By Torin Douglas
BBC media correspondent
As TV producers and executives gather for the annual Edinburgh Television Festival, British TV lies on the threshold of the biggest change since the arrival of Sky's multi-channel pay-TV service some 15 years ago.
BBC comedy Little Britain made its debut on digital
Some would go further, comparing its impact with that of the launch of commercial television, which broke the staid BBC's monopoly 50 years ago.
The digital revolution has been speeding up in the past year and is affecting everyone in television - the programme-makers, and the viewers.
It's changing what we watch, and how we watch it.
Digital TV is in 60% of homes, offering dozens - sometimes hundreds - of channels. That number is growing at the rate of more than 250,000 a month.
Within the next few months, the order is expected to be given for everyone in Britain to switch over to digital - region by region, starting in around two years' time.
Millions of people can also watch TV on their computers, through high-speed broadband connections.
Soon they will be able to download missed programmes. And thousands are watching on their mobile phones.
The digital revolution is changing viewers' habits
All this competition means channels must fight harder for ratings. At the same time, they are finding it harder to give programmes the time they need to develop.
For most viewers the choice is greater than before, provided they can be bothered to seek out the programmes they enjoy and value.
There are more opportunities to watch the best programmes from the past, as well as high quality new ones, from the US as well as the UK.
But that is causing problems for the once-dominant terrestrial channels. Their audiences are steadily going down, as competition grows and more time is spent watching digital channels.
Not a month goes by without another newspaper headline proclaiming the "worst-ever" day or week for BBC One or ITV1.
For ITV, about to celebrate its 50th birthday, this is particularly dangerous because its income is almost entirely dependent on the audience it can offer advertisers.
ITV1 has become more reliant on soaps such as Coronation Street and Emmerdale, peaktime dramas and 'event' programmes such as I'm A Celebrity... Get Me Out of Here.
It now looks a very different channel from its heyday, when there were only two or three channels to compete with.
But it has found one answer to the digital conundrum, by launching a family of ITV channels and promoting them on its own airwaves.
ITV2 and ITV3 are growing fast, and will soon be joined by channels for men and children.
Channel 4, also dependent on advertising, is about to do the same by launching More4, alongside FilmFour and E4.
But it is faring better than ITV in the new world, with a firm grip on the young and high-spending audience beloved of advertisers.
It has the knack of picking the best US shows, like Desperate Housewives and Lost, and has managed to refresh the Big Brother franchise.
The BBC has a different problem in the digital age.
Channel 4 has cherrypicked the best US shows such as Lost
Its income is guaranteed, but it needs to maintain wide public support to justify the continuation of the licence fee.
The debate over its next Royal Charter continues, although the government has made it clear the licence fee will continue for another 10 years after 2007.
But what sort of BBC should it be? While having to provide value to all licence-payers, it has said it will concentrate more on its public-service output.
That includes comedy, including popular series such as Little Britain, Nighty Night, The Office and Extras.
It has promised more local TV stations and greater interactivity, giving audiences more control over what they receive, and when they receive them.
For the BBC, like all broadcasters, the next few years could be even more challenging than the last.