Feeds

HD TV in the UK

Everything you need to know... fully revised and updated

  • alert
  • submit to reddit

5 things you didn’t know about cloud backup

Aspect ratio

A decent SD or HD TV can handle a change in aspect ratio with minimal fuss, which is useful as some content, such as the news, is still broadcast in old-style 4:3 (width:height), while movies and much of the current crop of TV are transmitted in a widescreen, 16:9 format, but you'll notice that the news, for instance, tends to be 4:3 so if your TV is a bit stubborn, Jon Snow's face will look slightly stretched.

sony bravia v series lcd tv

The situation is going to get worse when we add HD content to the mix as your TV will have to be flexible enough to chop and change aspect ratio and resolution. Satellite broadcaster Sky once said it had chosen to broadcast in both 720p and 1080i resolutions, but earlier this year it announced it will broadcast everything in 1080i. Other broadcasters have yet to decide which they favour, but are likely to use both, for different programmes, depending on factors such as how much movement the show contains, for example.

Interestingly, recent BBC trials of HD broadcasts, which used both 720p and 1080i, both encoded at high and low bit-rates, found that while the differences in picture quality were clear in the lab, ordinary viewers were generally impressed with all the pictures and didn't detect much of a difference between them.

Crucially, any 'HD Ready' HD TV has to be capable of displaying both 720p and 1080i content, either by expanding the image or shrinking it, depending on the screen's native resolution and sometimes its physical size. More and more screens are also supporting 1080p. While 1080p may never become a broadcast format, it'll be used by the next-generation optical disc formats, HD DVD and Blu-ray Disc, and by Microsoft's Xbox 360 and, soon, Sony's PlayStation 3.

HD Resolutions

For a TV picture to be HD it has to be one of three resolutions: 720p, 1080i or 1080p. There are other resolutions, but they're essentially standard definition (SD) sizes. The resolution's number is the number of horizontal lines that make up the image, analogous to its height in pixels. The letter, p or i, stands for 'progressive' or 'interlaced'.

Progressive images are displayed like a movie, one frame at a time, in rapid succession. Interlacing is the same technique used in regular TV: send half the picture at a time but do so twice as quickly. It's a bandwidth-saving technique. Each 'half' of the image comprises alternate sets of lines, so first you send lines 1,3,5,7... etc. then you send 2,4,6,8... and so on. The first set is drawn on the TV screen, then the second lot, but the speed is such that they eye doesn't notice.

Well, almost. In practice, this approach can create visible artefacts when the image is moving rapidly and there's a slight downgrade in the image's effective resolution. This isn't an issue with progressive pictures, which is why many US HD broadcasters show programmes in 720p not 1080i, even though the latter has more pixels and therefore should be more detailed.

The essential guide to IT transformation

More from The Register

next story
So, Apple won't sell cheap kit? Prepare the iOS garden wall WRECKING BALL
It can throw the low cost race if it looks to the cloud
Samsung Gear S: Quick, LAUNCH IT – before Apple straps on iWatch
Full specs for wrist-mounted device here ... but who'll buy it?
Apple promises to lift Curse of the Drained iPhone 5 Battery
Have you tried turning it off and...? Never mind, here's a replacement
Now that's FIRE WIRE: HP recalls 6 MILLION burn-risk laptop cables
Right in the middle of Burning Mains Man week
HUGE iPAD? Maybe. HUGE ADVERTS? That's for SURE
Noo! Hand not big enough! Don't look at meee!
AMD unveils 'single purpose' graphics card for PC gamers and NO ONE else
Chip maker claims the Radeon R9 285 is 'best in its class'
Chumps stump up $1 MEELLLION for watch that doesn't exist
By the way, I have a really nice bridge you might like...
prev story

Whitepapers

Endpoint data privacy in the cloud is easier than you think
Innovations in encryption and storage resolve issues of data privacy and key requirements for companies to look for in a solution.
Implementing global e-invoicing with guaranteed legal certainty
Explaining the role local tax compliance plays in successful supply chain management and e-business and how leading global brands are addressing this.
Advanced data protection for your virtualized environments
Find a natural fit for optimizing protection for the often resource-constrained data protection process found in virtual environments.
Boost IT visibility and business value
How building a great service catalog relieves pressure points and demonstrates the value of IT service management.
Next gen security for virtualised datacentres
Legacy security solutions are inefficient due to the architectural differences between physical and virtual environments.