The massive digital switchover programme being co-ordinated across the UK right now is nowhere near the last word in digital TV. After all, it only just includes hi-def, and doesn't make any allowances for mobile TV, or moving Freeview onto broadcast standards that make the most of its very limited bandwidth.
In fact, the UK doesn't even have a plan for digital TV beyond 2012. Media regulator Ofcom's plans stop abruptly at this arbitrary date and, officially, it's not even working on a long-term plan. Fortunately, members of the Digital TV Group and the European Broadcasting Union have gazed into the next decade to what they call Digital TV 4.0.
So how does the map look – from the roots of digital TV to the future?
Digital TV 1.0: the experimental years
Compression: MPEG-2 SD
The ups: First generation digital satellite TV systems took off in Europe. Standard-definition video offered a huge leap ahead, allowing five or six channels on a single transponder compared with just one analogue signal.
This quickly led to an explosion of new channels from the Continent, although the UK was slow off the mark. A few extremely tech- savvy enthusiasts soon realised you could do interesting things with these new digital receivers – like Nokia's groundbreaking D-Box – leading to the fondly remembered Dr Overflow project.
The newly established DVB standard brought some major advantages like electronic programme guides more dynamic than old-fashioned teletext. The common interface standard also enabled a receiver to handle multiple encryption formats with a cheap plug-in module. The pirates were close behind, seeing new weaknesses to exploit in the new digital encryption systems.
The downs: Like a trip back to the early days of analogue satellite, there weren't many channels, although you could use your analogue Sky dish to watch the first digital channels on Astra 1. But it was a great excuse to go out and buy a new receiver.
Look and sound: Most of the early signals weren't heavily compressed, so they looked very sharp and clear. CD-quality stereo had been demonstrated before on Astra Digital Radio, but never with pictures. Sparklies were a thing of the past, but the 'cliff effect' meant that you couldn't tune to poor signals in the hope of a grainy picture. A few dB separated a perfect picture from picture artefacts and choppy sound, then nothing at all.
Digital TV 2.0: the explosion
Compression: MPEG-2 HD & SD; MPEG-4 SD
Broadcast: DVB-S, DVB-T (2K & 8K)
Platforms: Satellite, terrestrial, cable, broadband
The ups: Digital TV for everyone. Well, you have to pay at first but Sky goes from strength to strength. Eventually everyone gets to enjoy the benefits when Freeview is born from the ashes of ITV Digital, and it's enormously popular.
Across Europe an explosion of free TV channels offered even more ways to peek into the cultural life of our neighbours. Outside the UK, though, most subscription services suffered terribly at the hands of highly industrious TV pirates. Still, it's good news for expats and football fans, with the parallel revolution of internet access making it easy for anyone to update a pirate card.
There were almost too many new ways to enjoy TV. The BBC and Sky competed with experiments in interactive TV – multi-screen, alternative soundtracks, shopping, banking, email, digital text. A lot of them fell by the wayside and most had to be rebuilt until they worked the way people wanted, but the red button was here to stay.
Personal video recorders brought the possibility of capturing digital streams with no loss of quality, and having more than one tuner in a box, but it took Sky to make it popular with Sky+. Freeview eventually cottoned on and created Freeview Playback with the help of the BBC and DTG.
The downs: ONdigital/ITV Digital is a lame duck from the start, showing off all the bad points of digital TV – over-compressed images and unreliable cheapo receivers. It's crushed by a combination of Sky's ruthless marketing, rampant piracy, and a poor reputation. It's pretty obvious that government, regulators, and ITV Digital's management don't get digital TV.
Broadband TV-by-phone suffers from the high price of using BT's network for consumer services. Once again, regulators are slow to deal with BT's monopoly. Kingston's TV service is ultimately closed down, while Homechoice barely struggles along.
Feedhunters have a harder time as broadcasters move onto MPEG 4:2:2, MPEG-4 and HD in search of improved quality – for brief periods these are effectively encrypted until commercially available receivers catch up. It's almost a relief when the military transmits its UAV downlinks in the clear!
Look and sound: Sky's picture quality is initially very impressive, with the first widescreen movie channel. However, it's not long before channels squeeze into too little space and we start to see compression artefacts frequently. Compression technology improves in leaps and bounds, but demand to for bandwidth is always ahead. MPEG-4 on-demand services start off poorly but soon show hugely improved picture quality.
Dolby Digital surround audio arrives on Sky, showing that the full home cinema experience isn't exclusive to DVD. We get a first look at big-screen, high- definition video demonstrations and go looking for our socks, which have been blown off.
Digital TV 3.0: digital switchover
Compression: MPEG-2 HD & SD; MPEG-4 HD/SD
Broadcast: DVB-S & S2; DVB-T (8K); DVB-H (mobile)
Platforms: Satellite, terrestrial, cable, broadband, mobile
The ups: The runaway success of Freeview and Sky opens a window of opportunity to switch from analogue TV systems to digital. A once-in-a-lifetime release of valuable UHF spectrum becomes possible – the Digital Dividend. The question is, what to do with it?
Governments catch the heady whiff of cash from a spectrum auction; public service broadcasters want to launch high-definition channels; commercial broadcasters are keen for subscription services and mobile TV; other industries see the chance for faster wireless broadband; and community groups want local TV.
Meanwhile, consumers are enjoying more choice than ever, with two free digital services and five subscription services – plus more to come. There are channels to fit every taste (and if not, there's always the internet), equipment to suit every home and prices for every pocket.
Hi-def gets a good reception, and TV services are quickly divided between the HD haves and have-nots. The cutting edge, though, is in mobile TV. Do people want to watch live TV channels on a phone or portable player, or are they happy to download at home to play back at leisure? The first streaming trials are inconclusive; sport is the only thing people are really willing to pay for live – but downloading to watch on the move is a hit.
The downs: As one observer puts it: "Spectrum auctions are the crack cocaine of public policy for politicians." Neither Ofcom nor the government can be convinced to leave any of the Digital Dividend in the public domain, to the disappointment of public service broadcasters and community groups.
The choice of digital TV providers doesn't result in a price war. Instead, we're offered confusing bundles that tease us with 'added value' from free phone calls, broadband or TV channels.
Broadcasters aren't all happy about the rush to HD: it's too expensive and there's no extra advertising money to be won. Yet it's soon obvious they'll lose eyeballs without HD, so ITV and Channel 4 begin a slow transition to HD anyway, with Five somewhere behind.
Look and sound: Hi-def in 720p or 1080i is a major step forward from standard definition. Even better, Dolby Digital surround sound becomes the standard audio format for HD.
However, for every hi-def channel there are a dozen barely watchable ultra-compressed standard-definition channels. Bandwidth on Freeview becomes so expensive that even major broadcasters transmit at surprisingly low quality.
Digital TV 4.0: screens everywhere
Time: 2011 and beyond
Compression: MPEG-2 HD & SD; MPEG-4 HD & SD
Broadcast: DVB-S2; DVB-T2; DVB-H2
Platforms: Satellite, terrestrial, cable, broadband, mobile
The ups: By digital switchover, there should be a national Freeview multiplex using DVB-T2 and MPEG-4 to carry four hi-def channels to most of the UK, plus free HD on Freesat, and maybe 50 HD channels on Sky. Even cable and broadband should have some hi-def – probably via on-demand.
The years after switch-off will see a set of mature digital TV technologies designed to last into the 2020s and approaching the Shannon Limit, a mathematical ceiling on signal compression. Some countries will also add MIMO, where you use both horizontal and negative polarity signals on the same frequency to double the capacity.
In particular, DVB-T2 is designed to allow Single Frequency Networks (SFNs), which use a single frequency to cover the whole country. Today, Freeview uses Multi-Frequency Networks, which use around five frequencies across different parts of the country, but moving to SFNs would release even more space for Ofcom to auction.
The question is, what do we do with the opportunity?
Britain's TV and spectrum regulator, Ofcom, doesn't have any official plans beyond the digital switchover in 2012, other than auctioning the Digital Dividend. Fortunately, a group of leading broadcast engineers – The Independent Expert Industry Group – have turned their eyes to the future and come up with a few ideas.
IEIG member Ian Childs, who also sits on the British Digital TV Group's Technical Council, told the DTG's 2008 summit: "The debate was HDTV or mobile. We don't want to pick winners ahead of things happening, we'd like a way of allowing both to establish a toe-hold, and defer the decision until we've got a bit more input from the marketplace.
"The Ofcom HD proposal makes quite a simple prospect for the consumers that want to upgrade, but how do we look at being able to migrate the whole platform to HDTV? We came up with a possible way ahead, to use single frequency networks to improve the spectrum efficiency and the number of HD services on offer. That would probably give us up to about 40 HDTV programmes."
To start with, the IEIG's plan would hold back some Digital Dividend frequencies to launch two national frequency networks after 2012, covering roughly 70 per cent of the UK and carrying eight hi-def channels in DVB-T2/MPEG-4. Gradually, the UK would switch to a more efficient Freeview network entirely based on DVB-T2 and MPEG-4, with perhaps three conventional multi-frequency networks and single-frequency networks. These would be so efficient that Freeview would be using less capacity than it now occupies, so the government could run another spectrum auction.
The group is also proposing a national pilot project for portable TV in 2012, so the London Olympics could be broadcast to anyone over a new single frequency network.
"If that proved successful, mobile TV could be one contender for some of the spectrum we'll be releasing at the time we make the transition to HDTV," adds Childs.
The downs: With Freesat now offering hi-def channels and several HD pay-TV options, it's easy to think there's no need to advance Freeview beyond a token set of HD channels.
Childs said: "If you look at the richness of the offerings from satellite and cable by the time we get to 2012, will four HD programmes be a sufficiently compelling prospect for the consumer to buy into terrestrial and keep it competitive?"
Perhaps more succinctly, as Professor David Youlton, DTG chairman, said: "DSO isn't digital switchover, it's Digital Spectrum Optimisation. Leave government out of it because they tend to screw it up big-time and 'short-term' the issues."
Even if Ofcom forges a long-term plan, the biggest problem is how to pay for it. Phil Laven of the European Broadcasting Union estimates that the current digital switch will have cost consumers €15billion in new equipment and TV licence fees, and we won't want to pay again. Broadcasters, multiplex operators and winners of the spectrum auctions are the most likely targets.
"We all need to think about new methods of funding switchover. Do not expect the public to pay for all this in future. Free-to-air digital terrestrial is important. Market- based mechanisms for spectrum optimisation do not give optimum results," says Laven.
Look and sound: In the short term we can look forward to 1080p hi-def broadcasts. Phil Laven adds: '1080p is very attractive, that would be a really good standard to start with for production, but today none of the set-top boxes out there will handle 1080p. I hope the next generation of set-top boxes will solve that problem.'
TV for mobile viewing is a completely different question. Do you shoot and crop it for small screens, or will people use 'eye-phones' that give them a full screen experience anywhere? It's not a sci-fi question; specs with standard-def wearable displays are already on sale.
Beyond Full HD comes Ultra High Definition – 4,000 lines and 22.2 three-dimensional surround sound. Designed by NHK in Japan, it goes to the physical and mental limits of human vision so you wouldn't need anything better. But it is a complete generation of broadcast, production and display technology away, even if NHK is hoping to start trial broadcasts in Japan as soon as 2012.
Top five tips for surviving digital transition
1: Buy the biggest and best screen you can
A good TV is always worth the cash, so go for the biggest screen with the best picture you can afford.
2. You can always add tuners
Set-top boxes are always cheaper than integrated tuners, so save pain and only upgrade the tuner when the technology improves.
3. Get a dish
Satellite TV moves faster and equipment is generally cheaper than terrestrial because standards are pretty much global.
4. Support the BBC
No one fights harder for free TV, and the research it does into new technology is worth the Licence Fee on its own.
5. Surf behind the curve
In other words, buy the second generation, not the first. You'll be ahead of the pack and the big bugs will be fixed.