Gadget speak

This week we pit two emerging 3D TV technologies against one another and we take a back-to-basics approach to picking the right flat screen.

Separated at birth

Competing 3D TV technologies

So, you have just upgraded your old cathode ray tube TV to a brand-spanking new high-definition flatscreen which you think will do you for the next five years before any new advance arrives on the horizon.

Unfortunately, display technologies appear to be taking a similar technology improvement curve to personal computers. In other words, as soon as you have shelled out your cash on a new TV, something else is already being advertised. The next big thing in displays appears to be three-dimensional TV.

Although 3D has been possible for many decades in the cinema and on TV, the technologies that were deployed proved not to be lastingly popular with audiences. The proponents of the technology promised an immersive cinematic experience. Viewers only experienced the sensation of things being poked and pointed in their general direction.

3D techniques

What's changed is a number of technologies being pushed by the likes of chip maker Intel, Industrial Light and Magic (George Lucas's special effects company) and Dolby, who have developed various techniques for turning existing movies and TV shows from 2D to 3D.

Clearly, this is a push for TV vendors to sell us new TVs and content providers to sell the same 'upgraded' content that they previously sold to us on VHS, DVD and currently Blu-ray.

Yet, as always with new technology, there is an old-fashioned format war as the vendors vie for dominance of this new standard. Two distinct technologies have emerged.

One technology uses shutter-controlled lenses. With this process, the images are placed into a single sequence with each alternating image using a different polarising frequency. The screen emits an RF (radio frequency) or IR (infra-red) signal to the viewer's lenses which is synchronised to the image on the screen. In other words, the left-eye image is only seen by the left lens and the same occurs for the right-eye.

Typically, the movie will run at 50 frames per second instead of the traditional 25 frames per second. The audience wears very specialised LCD shutter glasses which have lenses that can open and close in rapid succession. The glasses also contain special radio receivers.

The disadvantage of these systems is the complexity of the technology. This is likely to put up the cost of manufacture, which will inevitably be passed to the consumers.

The same method of alternating frames can be used to render modern 3D games into true 3D, although it has been used to give a 3D illusion on consoles as old as the Sega Master System and Nintendo Famicom.

Here, special software and hardware is used to generate two channels of images, offset from each other to create the stereoscopic effect. Again, LCD shutter glasses synchronised with the graphics card complete the effect. Samsung demonstrated this recently using NVidia processing technology.

The alternative polarised lens technology has been around for a while. The lenses in bins given out in cinemas when showing 3D movies such as the recent 'Beowulf' are polarised. With this system, each view is displayed on the screen simultaneously with different levels of polarisation.

The glasses allow only one of the images into each eye because they contain lenses with different polarisation.

Both technologies are only now available on TVs due to the introduction of higher-definition displays and faster refresh rates.

But, even without shelling out cash on new equipment, it is still possible to enjoy the 3D effect using the existing analglyphic - a combination of the traditional and well-known red/blue or red/green lenses.

Technology clinic

TV upgrading

My children received a Nintendo Wii for Christmas and I think it's now the right time for us to take the financial plunge and get a large high-definition flat screen television - most probably in the 40in-plus category. I am getting mixed messages from friends and the so-called experts who seem to split evenly between plasma technology and LCD?

P Fletcher (by email)

What is the difference between a 1080i and a 1080p signal?

By telephone

What do the manufacturers mean when they talk about the TV's contrast ratio? I've heard that plasmas are best at producing true black and LCDs are best at producing true white? Is this the case?

R Patel, India (by email)

Every month, we get one or two questions relating to technical specifications on new TVs. Considering that this technology is a constantly moving target, we cannot give you a definitive answer, but we can give you some very useful pointers on purchasing the best flat screen TV.

Reception is important as Freeview is migrating from the DVBT (digital video broadcast transmission) standard to the DVBT2 standard which will have better compression and thus more HD channels eventually. If this is important you might want to wait until the end of the year when TVs with DVBT2 come to market.

Response time, the time it takes for a pixel to change from active (black) to inactive (white) and back to active, is measured in milliseconds. The lower the response time the more effective the movement -- especially with large screens. Response times have been greatly reduced recently in LCDs and 4ms is a good benchmark for performance. Older LCDs suffer from motion-response lag where the pixels are slightly out of sync with the image on screen. This is most evident when trying to follow a football or a tennis ball. However, LCD technologies are rapidly improving.

Refresh rates, the number of times per second that an image is scanned, can also play a part. The standard PAL system uses 50Hz, but there are screens with 100Hz scanning and, later this year, we will see 200Hz.

Resolution of TVs is the most common question. With high-definition, you will often see it described as 1080i or 720p. The number stands for the amount of lines embedded within the signal. The letter describes the type of scan the television uses to display the picture. There are two types of scan - progressive and interlace - commonly abbreviated to 'p' and 'i'. Progressive is often seen as better because the lines of each frame are drawn in sequence. This is in contrast to interlacing where the odd and even lines of each frame are drawn alternately.

HDMI (high-definition multimedia interface) is the standard audio/video cable interface for transmitting uncompressed digital data between the receiving devices. It is important as it is rapidly replacing existing cable technologies such as coaxial cable, composite video, S-Video, SCART, component video, D-Terminal, and VGA. Generally, the more HDMI sockets the better. However, you will also have to consider some of these alternate legacy inputs and the cost of buying a separate HDMI cable (as they rarely come included with your new TV), which they can typically cost around £40 per cable.

5 Tips for reinstalling your computer

  1. Image the disk - The first stage before you reinstall your operating system and all your applications is to image the hard drive on a separate storage device. This is to ensure that, in the worst case scenario, you will still be able to restore your PC to the state it had before you started;
  2. Files and documents - Make a separate backup of all your individual media files, documents and favourites;
  3. List all your software - Make an inventory of all the installed software on your PC and the product keys. Make sure you have the original installation software to hand;
  4. Deactivate - Some software and media accounts, such as iTunes, will require you to deactivate and deauthorise your computer so that you can reinstall the applications and accounts with the same licence;
  5. Drivers - Make a note of all the installed devices, such as display, optical drives, and network controllers, and make sure you have copies of the drivers for reinstallation if need be.

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