Digital terrestrial television in the United Kingdom
Digital terrestrial television in the United Kingdom encompasses over 100 television, radio and interactive services broadcast via the United Kingdom's terrestrial television network and receivable with a standard television set. The majority of digital terrestrial television (DTT) services, including the five former analogue channels, are broadcast free-to-air, and a further selection of encrypted pay TV services (such as Racing TV) are also available.
Freeview is the only DTT service since Top Up TV closed in 2013. BT TV services are carried via IPTV signals.
The digital broadcasting technology adopted in the UK is the DVB-T system (Digital Video Broadcasting – Terrestrial) carrying compressed digital audio, video and other data in a combined transport stream, using COFDM modulation. A total of eight national and one local 'multiplexes' are broadcast in the UK, guaranteed to reach over 90% of the country. Three of the multiplexes, carrying the free public service channels operated by the BBC, ITV, Channel 4, S4C and Channel 5, are guaranteed wider coverage still, reaching 98.5% of the country including areas dependent on low-power local relays.[1]
In the UK, the switchover from analogue to digital TV started on 17 October 2007 and was completed on 24 October 2012. Each group of regional transmitters had its analogue broadcasts switched off at a certain point between those dates.
Receiving and recording[edit]
Digital Terrestrial Television is commonly received by means of a compatible set-top box or integrated digital television (IDTV), connected to an appropriate receiving antenna. In most cases, reception is possible using aerials originally used for analogue television.
Transmissions may be recorded in many ways – such as via the connection of a set-top-box to an existing 'analogue' video or DVD recorder, or by the use of newer models of such recorders which have built-in digital tuners. However, the most common option is by the use of set-top-boxes which incorporate a hard disk drive, and allow the recording of the digital signal directly to disk, for later replay. Recording on such boxes, known as Personal Video Recorders or PVRs, is more convenient, as programmes may be easily selected for recording from an on-screen programme guide, with no need to specify explicit start and end times for recordings, and no need to program more than one piece of equipment.
Many television services which incorporate DTT channels in their service offering – e.g. Top Up TV, BT TV, and TalkTalk Plus TV, offer set top boxes with such a recording facility. Non-subscription DTT PVRs are also available and are often sold under the 'Freeview+' banner (formerly Freeview Playback.)
There also exist a variety of solutions to enable the viewing and recording of DTT programmes on personal computers, with various TV cards or USB tuners available for use with a variety of software packages, including MythTV and Windows Media Center. Most cards or tuners include their own software in the package also.
Features[edit]
Digital Terrestrial Television provides many more channels. For some viewers it offers much improved reception compared to analogue broadcasts (although these had been entirely discontinued in the UK by 2012), including 16:9 anamorphic widescreen. A number of interactive services are also offered.
An eight-day Electronic Programme Guide (EPG) is available and allows viewers to see programme descriptions and broadcast times well in advance. PVRs will make use of this facility allowing recording timers to be set. This Eight-Day EPG was not an original feature of the Digital Terrestrial system, therefore some early receivers, such as receivers originally made to operate with the ONdigital service, will only display details of 'now and next' programme information.
A fourteen-day Top Up TV EPG was an alternative which was available to TUTV-branded PVRs.
History[edit]
Development and launch[edit]
Digital terrestrial television launched in the UK on 15 November 1998, just after digital satellite television on 1 October 1998. The technology required that the UK government license the broadcast of channels in six groups, or multiplexes (abbreviated to 'mux') labelled 1, 2, A, B, C, and D.[2]
The Independent Television Commission (ITC) allocated each existing analogue terrestrial channel half the capacity of a multiplex each. This meant the BBC got a multiplex to themselves (Multiplex 1), ITV and Channel 4 shared Multiplex 2 (though 3%[3] of the capacity was given to Teletext Ltd.) and Channel 5 and S4C shared Multiplex A. The remaining spectrum (Multiplexes B, C and D) was then auctioned off. A consortium made up of Granada and Carlton (members of the ITV network, which have now merged to form ITV plc) and BSkyB successfully bid for these licences, and set-up the subscription ONdigital service, though BSkyB left the consortium prior to launch.
The BBC made some use of its multiplex for three of its then four new television services; BBC Choice (which had started on 23 September 1998 with four national variations), BBC News 24 and BBC Parliament (albeit in sound only). ITV initially used their space to house ITV2 (from 7 December 1998) in England and Wales, You2 (later UTV2) in Northern Ireland and S2 in Scotland (now both ITV2), as well as GMTV2 during the early mornings. Channel 4 used their space for subscription channels FilmFour and E4 which, although not part of ONdigital, would be paid for and were only available through an ONdigital subscription. Channel 4's nationwide coverage on 'mux' 2 enabled it to be received terrestrially throughout much of Wales for the first time in its history, where previously only S4C had been available. Consequently, S4C's digital service, 'S4C Digidol' carries only Welsh-language programming, in contrast to S4C analogue which also carries English-language programmes commissioned and transmitted by Channel 4 in other parts of the UK.
Channel 5 sold its half of Multiplex A to the owners of the other half of the multiplex, S4C, who set up a subsidiary called S4C Digital Networks (SDN) to manage the multiplex and rented most of it out to ONdigital as well as some space to the BBC who launched BBC Knowledge on 1 June 1999, at a time when technical capabilities limited the number of stations it could carry on its own multiplex. S4C chose not to carry S4C Digidol and its newly launched digital Welsh Assembly station, S4C2 outside Wales, preferring to sell the space instead. Consequently, some ONdigital services were not available on Welsh transmitters.
While the BBC was seemingly concerned with delivering a service of good technical quality, other broadcasters chose to deliver a larger number of channels rather than optimise service reliability and picture quality.[4]