DIGITAL TELEVISION

Digital Television

What is Digital Television (DTV)?

Most DTV services around the world are based on the Digital Video Broadcasting (DVB) set of standards, which define digital broadcasting using existing satellite, cable, and terrestrial infrastructures. Consumers wishing to switch to digital must choose between these three digital TV broadcasting systems: satellite, cable and terrestrial DTV .

At present, many consumers' choices are limited because no DTV services are currently universally available throughout the UK. The coverage of the three platforms also varies. None offers total UK coverage. A satellite dish, rather than a conventional TV aerial, is necessary to receive digital TV broadcasts transmitted via satellite.

Digital satellite broadcasts cover the largest geographic area of any of the three platforms; some viewers, however, are unable to install a satellite dish (e.g. people living in flats or listed buildings, where dishes are not permitted).

20% of households are unable to receive digital terrestrial broadcasts because they are situated in areas of poor current signal strength. NTL and Telewest, which account for almost all of the UK cable market, operate in different geographical regions, focusing mainly on densely populated urban areas. Although their networks are expanding, many regions are not covered by cable services.

Digital terrestrial broadcasting employs a terrestrial broadcast infrastructure and can be received via a conventional TV aerial, although some older aerials may need to be upgraded. Terrestrial DTV services have lower acquisition costs than satellite or cable services, in that they employ existing TV aerials. Currently, digital tuners most commonly take the form of set-top boxes, which are often provided to subscribers free or at very low cost.

Installation costs for satellite dishes and cable network connections are similarly subsidised.

Cable DTV services are transmitted via an operator's fibre optic cable network and a physical connection to such a network is necessary to receive DTV broadcasts. Cable DTV services are commonly packaged with other services such as telephony and internet access.

Digital TV services are also beginning to be made available over broadband telecommunications connections, particularly via digital subscriber line (DSL) technologies.

Consumer pay-DTV receiving equipment also incorporates conditional access systems. These restrict access to pay-DTV services to authorised users (subscribers) by encrypting the transmitted programming.

A subscriber's conditional access details are normally contained on a smart card. This must be inserted into the set-top box to decrypt and thus provide access to the subscription services the viewer has elected to receive. There are numerous DVB-compliant conditional access systems currently in use.

Some interactive services require a return path, a piece of technology which carries requests from the viewer of an interactive service (such as purchase requests and transaction information in the case of interactive TV shopping services). The nature of the return path varies across DTV services.

Many DTV-enabled households receive these free-to-air digital services via a subscription to a multi-channel cable or satellite pay-TV package. This subscription is additional to the annual TV licence fee.

Questions & Answers

Can I get digital TV in my area?

For cable and satellite you need to ask your local TV shop. For terrestrial, Freeview asks for your postcode then tells you if Digital Terrestrial Television (DTT) is receivable in your area. The government has now confirmed that analogue TV signals will be turned off in the UK by 2012 on a regional basis beginning in 2008.

Do I need a new television set to receive digital television?

Conventional analogue TV sets cannot receive digital TV broadcasts without a digital tuner of some kind. A digital tuner decodes the digital broadcast signal (whether received via satellite, terrestrial or cable) for display on a TV set.

The Freeview service, launched in October 2002, allows viewers to receive free-to-air digital terrestrial broadcasts via the purchase of a low-cost set-top box, retailing for around £99, with no additional subscription. The service includes digital versions of the five analogue channels as well as a number of additional digital-only channels.

Any TV that is to continue to receive broadcasts after switchover will need to be converted for digital. There are various means of doing this, including adding an individual set top box/ adapter. However, routing signals from one digital receiver to other TVs is also possible, for viewing the same digital channel simultaneously on all of the TVs. In addition new digital products are coming onto the market that can enable individual digital channels to be viewed on different TVs at the same time. Visit your preferred local retailer for more details.

How will I know which new television sets can receive digital services?

Television sets with a built-in digital tuner are called Integrated Digital Televisions (iDTVs) Look for the Digital Video Broadcasting mark (DVB) as carried by the majority of integrated digital TVs either through a screen sticker on badge imprinted on the TV fascia surround.

Do I need a different TV licence for digital?

No. The Freeview (DTT) service is paid for out of current licence revenue. In fact, if you do NOT view DTT you are paying for a service that you are not using! Cable and Satellite have their own contracts with you if you subscribe.

Digital vs Analogue

DVB employs MPEG-2 compression, one of a series of MPEG (Moving Picture Experts Group) standards for compression of audio and video signals. MPEG-2 broadcasts can be transmitted using existing cable, satellite, and terrestrial systems. The use of this kind of compression technology allows a greater number of digital channels to be transmitted in the same bandwidth required by an analogue channel.

Digital technology provides a more efficient way to deliver television than analogue transmissions.

Common benefits offered on all DTV platforms (Satellite, Cable & DTT) include:

In addition, true two-way interactive services can be accessed on satellite when the box is connected to a telephone line or via the built in return path on cable. Gaming, betting, shopping and banking services amongst others can all be accessed for the cost of a telephone call.

Digital Terrestrial Television (DTT) does not support two-way interactive services although a fixed or mobile phone service can be used to engage with interactive services.

Choice: DTV offers a greater range and variety of channels both free-to-air and through subscription. Existing digital packages offer more than a hundred different channels dedicated to everything from sport and film to current affairs, cartoons and education.

Quality: DTV offers a higher quality in sound and pictures as well as a greater consistency of reception over long distances.

New services: DTV provides enhanced and interactive services allowing consumers to shop, send email and text messages, surf the internet and book holidays, all through the familiar medium of the television.

Efficiency: DTV makes much more efficient use of the broadcasting spectrum than conventional analogue TV broadcasting.

LCD Screens

Conventional cathode-ray tube (CRT) TV sets are now becoming obsolete, with plasma and LCD (liquid crystal display) screens taking their place. As High Definition (HD) TV services become available, LCD screens capable of displaying HD broadcasts are are likely to become even more popular.

There are several HD TV standards, which refer to the level of detail in the broadcast signal. The two most common standards are 720p and 1080i. A 720p image consists of 720 horizontal lines, and an LCD screen designed to display 720p images should have a resolution of at least 1,280 x 720 pixels. A 1080i broadcast utilises 1080 horizontal lines that are interlaced. To display a 1080i signal, a screen resolution of at least 1,910 x 1,080 pixels. Only the most expensive LCD screens are capable of displaying such a high resolution, though lower-resolution screens can display a 1080 broadcast by interpolating (down-sampling) the image.

Large LCD 37-inch screens can now be purchased for under £1,000 -- the most expensive models, capable of displaying true 1,080-line broadcasts are likely to cost more in the region of £2,2000. However, a 37-inch screen is best viewed at a distance and is likely to be overwhelming in a small lounge or living room. Good quality 32-, 27-, or 26-inch screens can be purchased for well under £1,000.

Cheaper LCD screens may suffer from poor viewing angles, causing the image to appear dark or too reflective to anyone not sitting in front of the display. Cheaper screens may also be unable to display the full range of colours. As the quality of a screen cannot be determined by its specification, it is important to read specialist reviews and to view the screen yourself before committing to a purchase.

Most LCD screens include a built-in tuner, either analogue or digital. Digital tuners invariably produce a better quality picture and come with over 30 Freeview channels, digital Teletext and an electronic programme guide.

Depending on your requirements, you should check for the following TV connections:

Aerial: an aerial is needed to receive either analogue or digital Freeview broadcasts.

Audio: audio outputs allow you to connect to an external amplifier and speakers. A digital S/PDIF output allows a connection to an external surround-sound decoder and speakers.

Component Video: input for DVD players that can produce progressive scan video.

Composite/S Video: can be used for analogue camcorders, video recorders and games consoles. Separate audio inputs are provided.

D-Sub VGA: allows you to connect your computer; some TVs have a DVI input instead.

HDMI: used for high definition sound and video devices, such as Blu-ray disc players.

SCART/RGB SCART: a SCART input allows you to connect a DVD player or set top box.

Resources

UKorbit's Digital TV page

The Digital TV Group (tv in your area?)

Free-to-View Digital TV

Visit UKOrbit's Consumer & Advice Centre for further help and information.