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Artículo principal: Televisión digital terrestre

La televisión digital terrestre en el Reino Unido comprende más de 100 servicios de televisión, radio e interactivos que se transmiten a través de la red de televisión terrestre del Reino Unido y se pueden recibir con un televisor estándar. La mayoría de los servicios de televisión digital terrestre (TDT), incluidos los cinco antiguos canales analógicos , se emiten en forma gratuita y también está disponible una selección adicional de servicios de televisión de pago codificados (como Racing TV ).

Freeview es el único servicio de TDT desde que Top Up TV cerró en 2013. Los servicios de BT TV se transmiten a través de señales de IPTV .

La tecnología de transmisión digital adoptada en el Reino Unido es el sistema DVB-T (Digital Video Broadcasting - Terrestrial) que transporta audio, video y otros datos digitales comprimidos en un flujo de transporte combinado, utilizando modulación COFDM . En el Reino Unido se emiten un total de ocho 'múltiplex' nacionales y uno local, garantizados para llegar a más del 90% del país. Tres de los múltiplex, que llevan los canales de servicio público gratuito operados por la BBC , ITV , Canal 4 , S4C y Canal 5 , tienen garantizada una cobertura aún más amplia, llegando al 98,5% del país, incluidas las áreas dependientes de relés locales de baja potencia. [1]

En el Reino Unido, la transición de la televisión analógica a la digital comenzó el 17 de octubre de 2007 y se completó el 24 de octubre de 2012. Cada grupo de transmisores regionales tuvo sus transmisiones analógicas apagadas en un momento determinado entre esas fechas.

Recepción y grabación [ editar ]

La televisión digital terrestre se recibe comúnmente por medio de un decodificador compatible o televisión digital integrada (IDTV), conectado a una antena receptora adecuada. En la mayoría de los casos, la recepción es posible utilizando antenas originalmente utilizadas para televisión analógica.

Las transmisiones pueden grabarse de muchas formas, como mediante la conexión de un decodificador a una grabadora de vídeo o DVD "analógica" existente , o mediante el uso de modelos más nuevos de tales grabadoras que tienen sintonizadores digitales incorporados. Sin embargo, la opción más común es mediante el uso de decodificadores que incorporan una unidad de disco duro y permiten la grabación de la señal digital directamente en el disco, para su posterior reproducción. La grabación en tales cajas, conocidas como grabadoras de video personales o PVR, es más conveniente, ya que los programas se pueden seleccionar fácilmente para grabar desde una guía de programas en pantalla, sin necesidad de especificar horas de inicio y finalización explícitas para las grabaciones, y sin necesidad de programar más de un equipo.

Muchos servicios de televisión que incorporan canales de TDT en su oferta de servicios, por ejemplo, Top Up TV, BT TV y TalkTalk Plus TV , ofrecen decodificadores con tal facilidad de grabación. Los PVR de TDT sin suscripción también están disponibles y, a menudo, se venden bajo el banner 'Freeview +' (anteriormente Freeview Playback).

También existe una variedad de soluciones para permitir la visualización y grabación de programas de TDT en computadoras personales, con varias tarjetas de TV o sintonizadores USB disponibles para su uso con una variedad de paquetes de software, incluidos MythTV y Windows Media Center . La mayoría de las tarjetas o sintonizadores también incluyen su propio software en el paquete.

Funciones [ editar ]

La televisión digital terrestre ofrece muchos más canales. Para algunos espectadores, ofrece una recepción mucho mejor en comparación con las transmisiones analógicas (aunque estas se habían descontinuado por completo en el Reino Unido en 2012), incluida la pantalla ancha anamórfica 16: 9 . También se ofrecen varios servicios interactivos.

Se encuentra disponible una Guía electrónica de programas (EPG) de ocho días que permite a los espectadores ver las descripciones de los programas y los horarios de transmisión con mucha anticipación. Los PVR utilizarán esta función, lo que permitirá configurar los temporizadores de grabación. Esta EPG de ocho días no era una característica original del sistema Digital Terrestrial, por lo tanto, algunos de los primeros receptores, como los receptores fabricados originalmente para operar con el servicio ONdigital , solo mostrarán detalles de la información del programa "ahora y el próximo".

Una EPG de TV con recarga de catorce días era una alternativa que estaba disponible para los PVR de la marca TUTV.

Historia [ editar ]

Desarrollo y lanzamiento [ editar ]

La televisión digital terrestre se lanzó en el Reino Unido el 15 de noviembre de 1998, justo después de la televisión digital por satélite el 1 de octubre de 1998. La tecnología requería que el gobierno del Reino Unido autorizara la transmisión de canales en seis grupos, o múltiplex (abreviado como 'mux') etiquetados como 1, 2, A, B, C y D. [2]

La Comisión de Televisión Independiente (ITC) asignó a cada canal terrestre analógico existente la mitad de la capacidad de un múltiplex a cada uno. Esto significó que la BBC consiguió un multiplex para ellos mismos (Multiplex 1), ITV y Channel 4 compartieron Multiplex 2 (aunque el 3% [3] de la capacidad se le dio a Teletext Ltd. ) y Channel 5 y S4C compartieron Multiplex A. El espectro restante (Multiplex B, C y D) luego fue subastado. Un consorcio formado por Granada y Carlton (miembros de la red ITV, que ahora se han fusionado para formar ITV plc ) y BSkyB ofertaron con éxito por estas licencias y establecieron el servicio de suscripción ONdigital, aunque BSkyB abandonó el consorcio antes de su lanzamiento.

La BBC hizo algún uso de su múltiplex para tres de sus cuatro nuevos servicios de televisión; BBC Choice (que había comenzado el 23 de septiembre de 1998 con cuatro variaciones nacionales), BBC News 24 y BBC Parliament (aunque solo en sonido). ITV utilizó inicialmente su espacio para albergar ITV2 (desde el 7 de diciembre de 1998) en Inglaterra y Gales, You2 (más tarde UTV2) en Irlanda del Norte y S2 en Escocia (ahora ambos ITV2), así como GMTV2 durante las primeras horas de la mañana. Channel 4 utilizó su espacio para los canales de suscripción FilmFour y E4los cuales, aunque no forman parte de ONdigital, serían de pago y solo estaban disponibles a través de una suscripción a ONdigital. La cobertura nacional de Channel 4 en 'mux' 2 permitió que se recibiera terrestre en gran parte de Gales por primera vez en su historia, donde anteriormente solo había estado disponible S4C. En consecuencia, el servicio digital de S4C, 'S4C Digidol' solo transmite programación en galés, en contraste con S4C analógico, que también transmite programas en idioma inglés encargados y transmitidos por Channel 4 en otras partes del Reino Unido.

Channel 5 vendió su mitad del Multiplex A a los propietarios de la otra mitad del multiplex, S4C, quienes establecieron una subsidiaria llamada S4C Digital Networks (SDN) para administrar el multiplex y alquilaron la mayor parte a ONdigital, así como algo de espacio. a la BBC, que lanzó BBC Knowledge el 1 de junio de 1999, en un momento en que las capacidades técnicas limitaban el número de estaciones que podía transmitir en su propio multiplex. S4C optó por no llevar S4C Digidol y su recién lanzada estación de ensamblaje galés digital, S4C2 fuera de Gales, prefiriendo vender el espacio en su lugar. En consecuencia, algunos servicios ONdigital no estaban disponibles en transmisores galeses.

Si bien la BBC aparentemente estaba preocupada por brindar un servicio de buena calidad técnica, otras emisoras optaron por brindar una mayor cantidad de canales en lugar de optimizar la confiabilidad del servicio y la calidad de la imagen. [4]

ITV Digital [ editar ]

Artículo principal: ITV Digital

ONdigital tuvo problemas desde el principio, y el cambio de nombre del servicio ITV Digital el 11 de julio de 2001 no ayudó en el asunto. Todos los servicios de suscripción, excepto E4 y FilmFour, salieron del aire el 1 de mayo de 2002 después de que el consorcio colapsara, explicado como debido al pago excesivo de los derechos de televisión de The Football League . Sin embargo, la elección del modo de transmisión 64QAM, el hecho de que al menos el 40% de los hogares necesitarían nuevas antenas para recibirlo, una alta tasa de abandono , un sistema de cifrado inseguro que se puede piratear , el costo de tener que proporcionar decodificadores gratuitos y La agresiva competencia de BSkyB contribuyó a los crecientes costos de ITV Digital, antes de que los accionistas Granada y Carlton detuvieran la empresa.

Freeview [ editar ]

Artículo principal: Freeview (Reino Unido)

Cuando ITV Digital se derrumbó, los derechos volvieron al regulador y la ITC invitó a licitar por el espacio en los Multiplexes B, C y D. El consorcio Freeview fue formado por la BBC, la empresa transmisora National Grid Wireless (conocida en ese momento como Crown Castle Reino Unido) y BSkyB. Este consorcio (nombre legal DTV Services Ltd y que opera bajo la marca "Freeview") ganó y lanzó un nuevo servicio. Abandonando el fallido modelo de negocio de ITV Digital, Freeview se lanzó el 30 de octubre de 2002 con canales de televisión gratuitos únicamente, e hizo que las estaciones de radio digitales estuvieran disponibles en los receptores de televisión por primera vez. La BBC controlaba un Multiplex (B) para sus propios servicios, y Crown Castle / National Grid los otros dos (C & D) para servicios comerciales, aunque el Community Channel también operaba en Multiplex B. El segundo multiplex de la BBC le ha permitido televisar El Parlamento de la BBC, donde anteriormente solo había estado disponible en sonido, permitió que BBC Knowledge y su sucesora, BBC4, dejaran de alquilar espacio de SDN para cobertura, y permitió pantallas de video especiales en su servicio interactivo BBCi.para usar durante eventos deportivos comoWimbledon and carrying loops of news headlines and weather, (services already provided on digital satellite)

On 11 October 2005, ITV plc and Channel 4 joined the Freeview consortium and in the same year ITV plc also bought SDN and as such they gained control of Multiplex A.

Top Up TV[edit]

Main article: Top Up TV

The space ITV Digital had rented on other multiplexes initially became empty again, but some were rented out to allow new channels to launch. In May 2004 Top Up TV was launched to provide subscription content in hitherto unused space on multiplex A, rented from Channel 5[5] and additional services transmitted by Channel 4 on their own capacity on Multiplex 2.

TCM purchased its own slot throughout England, Scotland and Northern Ireland from the multiplex owner, SDN, but rents from Sit-up Ltd in Wales, timesharing with bid tv. Multiplex A is ultimately owned by ITV Plc via its SDN acquisition, but ITV only has involvement with Top Up TV channels via Channel 5.[5] In September of the same year, Top Up TV began operating solely on Multiplex A, as Channel 4 reclaimed the bandwidth on Multiplex 2 for its own services More 4, E4, and most recently Film4.

En octubre de 2006, Channel 5 lanzó dos nuevos canales digitales gratuitos, Five Life y Five US , utilizando la capacidad anteriormente alquilada a Top Up TV. [6] Esto dejó a Top Up TV con un número reducido de transmisiones de video. En noviembre de 2006, la compañía lanzó Top Up TV Anytime , un servicio que transmite "descargas" nocturnas que son grabadas por una grabadora de video personal (PVR) patentada de Top Up TV Anytime . Al mismo tiempo, comenzaron a reducir el servicio lineal.

On 19 April 2006, Ofcom ruled that, on request of each multiplex operator, the 'free-to-air channels only' requirement put in place at the launch of Freeview in 2002 may be lifted on Multiplex B, C and D. The effect of this ruling is that if a Mux operator requests the restriction to be lifted, their multiplex may carry pay TV services. Ofcom says that the digital television market has changed significantly since 2002. Consequently, it believes that this restriction is no longer required.

During the consultation, 9 of the 12 responses from broadcasters were in favour of removing the restriction. These included the BBC. The BBC agreed that the digital television market had changed substantially since 2002, and that Top Up TV probably couldn't afford the current cost of DTT slots anyway. The BBC suggested that the deregulation should be conditional on a number of further changes to regulation. These included that Ofcom changes the transmission mode of broadcast on all multiplexes from 16QAM to 64QAM so more services could be squeezed onto the digital terrestrial platform. However, Ofcom rejected these suggestions, saying they were outside the scope of the consultation.

Out of the three that opposed, one was Channel 4, which has been putting in place a portfolio of free-to-air channels, among them Film4 which was made free-to-air across all platforms on 23 July 2006. Channel 4 argued that the number of free channels available has been the major driving force behind the massive success of the platform – there are now more than 10 million Freeview boxes in use.

A number of broadcasters requested that their replies were kept confidential. These include ITV and BSkyB. However, it is believed that ITV opposed the plan and BSkyB supported it.[7] In addition to replies from broadcasters, there were 21 replies from individuals. Of these, 20 opposed the change.

The channels on Multiplexes B, C and D are those owned by the Freeview consortium and include the three Sky channels on the platform and the UKTV channels. However, Ofcom believes that in the short to medium term, it is unlikely existing free-to-air channels will convert to pay TV. This is because, firstly, Multiplex B is run by the BBC, which is not expected to request the removal of the free-to-air requirement. Secondly, due to the nature of the contracts the channel broadcasters hold with multiplex operators and content providers, it is unlikely a channel will be able to change to pay TV.

It was announced on 8 February 2007 that BSkyB intended to withdraw Sky Three, Sky News and Sky Sports News from the platform in the summer of 2007. BSkyB had said that it intended to replace them with 4 of its subscription channels. It also said that it would use an alternative (MPEG4) codec, which would enable a greater number of channels to be broadcast, but would require the purchase of new equipment for those who wished to receive the new service.[8] On 6 October 2007 Ofcom said that the plans for a new subscription service raised competition concerns and may have to be scrapped.[9]

2008 update issues[edit]

During 2008, a rolling programme of transmitter updates caused approximately 250,000 set-top boxes to stop working. Freeview had warned consumers in advance of the update, which was phased over a three-month period.[10] The problem affected a specific range of older units, and was caused by an increased Network Information Table (channel list) exceeding the memory available in some set-top boxes. This had been part of the specification that was available and implemented in the very early OnDigital boxes, but not in those using the SetPal chip set.[11] Affected consumers were advised to buy new set-top boxes.

Digital switchover[edit]

  Switchover complete
For full list of dates, see digital switchover dates in the United Kingdom.

Summary[edit]

The UK Government's intention was that digital terrestrial television would completely replace analogue terrestrial television in the United Kingdom by 24 October 2012. This process was known as "Digital Switchover", or DSO. The industry association for digital television in the UK, Digital TV Group, was responsible for co-ordination between Freeview and other digital services. DTG licensed suitable equipment to bear the Digital Tick and Freeview Playback Logos[12] to identify PVRs and other devices designed to work through switchover, and to raise awareness of DTT product quality and standards. Digital terrestrial television is broadcast using the DVB-T international standard for standard definition content and DVB-T2 for high definition content.

The digital switchover process involved discontinuing analogue terrestrial TV broadcasts, which in some areas allowed for greater signal strength and/or better coverage of digital multiplexes. The process concluded on 24 October 2012, when digital switchover completed in Northern Ireland (the same day as the Republic of Ireland also completed its digital switchover[13]).

In areas where analogue signals had terminated, older receiving equipment was likely to require replacement or upgrade. This process was subsidised by the UK Government for those on low incomes. Contracts for this operation were awarded to BSkyB in the Border Television region. Upgrading of analogue receiving equipment required a Freeview set-top box (or other DVB-T capable digital receiver). Where an analogue TV recording device was in use this ideally would require a separate Freeview set-top box, to replicate the previous functionality of recording and watching different programme sources.

History[edit]

The progress towards digital switchover in the UK was long. The then Secretary of State for Culture, Media and Sport, Chris Smith, announced in 1999 that the Government's intention was to achieve switchover "between 2006 and 2010". Work started in earnest with the setting up of the Digital Action Plan, a body working across industry, government and consumer groups to advise on the best way to meet the switchover target date.

By 2003, however, it was becoming clear that switchover could not start by 2006. In particular, the decision taken by the International Telecommunication Union to call a Regional Radiocommunication Conference to establish a frequency plan for digital broadcasting meant that in practice, substantive steps towards switchover would need to wait until after the conference's second session, due to be held in May and June 2006.

On 15 September 2005, addressing the Royal Television Society in Cambridge, Smith's successor at the DCMS, Tessa Jowell, announced the go-ahead for switchover in the UK, coupled with support measures to ensure the disadvantaged are not left behind.[14]

On the day after Jowell's speech, an independent not-for-profit company, Digital UK, was established to co-ordinate the switchover process. Set up by the broadcasters and the commercial multiplex operators, Digital UK was required to co-ordinate the project and ensure that the public are kept informed about progress.

Local television broadcasters, including the BBC and ITV, actively encouraged viewers to upgrade to digital television. UK broadcasters were also under additional pressure to complete migration before the Olympic Games.

Digital rollout[edit]

The British Government gave Ofcom and Digital UK jointly the task of discontinuing analogue television broadcasting. The switch-off occurred on an ITV sub-region basis.[15] In March 2005, a technical trial in Ferryside, Wales, resulted in viewers losing three out of the four available analogue channels in favour of going digital, leaving only analogue BBC Two Wales until switchover at Preseli in August 2009 (at the time, BBC 2W on digital offered a different schedule to BBC Two Wales on analogue).

In October 2007, following a 15-month publicity and information campaign, and an early digital launch in August by Channel 5,[16] the Whitehaven, Eskdale Green and Gosforth transmitters switched off analogue signals on the BBC Two frequency, and began broadcasting a temporary digital service for the main channels. On 14 November, all analogue signals were switched off, and the permanent three-multiplex digital service began (albeit with Channel 5 only on the Whitehaven transmitter, until 2009). Unfortunately, as had been feared, a small number of homes among the hills, which had received "fuzzy" analogue signals, particularly in Eskdale, were unable to receive a decodable Freeview signal.[17] The only other serious problem resulted from the "rescan" command in some models of set-top box defaulting to frequencies used by the nearest main transmitter, instead of the strongest digital signals; this could be overcome by using the "add channel" option to select channels one-by-one, and in the long term by corrections to the boxes' software.[18]

In November 2008, the full rolling programme started in the ITV Border region at the Selkirk transmitter, with the Caldbeck transmitter switching a year later (Caldbeck was rebuilt, and broadcasts Scottish multiplexes as well as English ones to improve service to viewers north of the border; the nearby Sandale transmitter ceased to broadcast TV). The programme continued across the rest of the country, with the Westcountry region, Wales and the Granada region switching over in 2009. The West, STV North, STV Central regions and the Channel Islands followed in 2010; the Central, Yorkshire and Anglia regions in 2011; and finally the Meridian, London, Tyne Tees & UTV regions in 2012.

Many decisions had to be made, including what to do about people who may find the new technology confusing, or who have no desire to receive more than the four or five channels they originally had, and who may have been reluctant to buy a digital box to view the free channels. The government arranged for the BBC to administer a Digital Switchover Help Scheme to ensure that groups such as the over-75s and recipients of disability benefits did not lose their television services when analogue transmissions were switched off.

Another issue was that the "98.5 per cent of the population" availability target could only be achieved "via rooftop aerials",[19] while Section 134 of the Communications Act 2003 sets out the principle "that no person should unreasonably be denied access to an electronic communications network or to electronic communications services".[20] This is taken to mean that everyone has the right to mount a television aerial on their roof.[21] Ofcom allocated frequencies for groups of households to provide "self-help" relay transmitters at their own expense (for analogue broadcasts there were some 200 of these, serving around 13,000 households), but suggested that in such cases, terrestrial TV may no longer be the most cost-effective solution.[22]

The switchover process[edit]

Digital Switchover banner in Porthmadog, Wales, as seen in September 2009

After several months of press publicity, leaflet drops, public meetings etc., captions started appearing on analogue broadcasts from the affected transmitters, warning viewers that the analogue service would shortly be switched off and that they would need to take action (for Whitehaven, the first large area to switch over, the captions started appearing some 5 months before the BBC Two analogue service was switched off[23]). At about the same time, details of the Switchover Help Scheme were distributed. Although viewers who lived outside existing Freeview reception areas were unable to test any digital receiving equipment they had bought at this early stage, test-screens on Ceefax (BBC One & Two) and Teletext (ITV & C4/S4C) page 284 made it possible to determine whether they were likely to need a new aerial or a signal amplifier to receive digital transmissions.

Next, detailed information booklets were delivered to all households in the area (including many on the fringe who may have been receiving their TV from other transmitters- hence the importance of the on-screen warning captions). Two or three months later, the first stage of the switchover began with the analogue BBC Two replaced with the new BBC A multiplex.[24] At some locations, during the period between stage one and stage two, BBC One, ITV or Channel 4 moved to the analogue BBC Two frequency where that channel's frequency was required for the digital transmission of Multiplex 1. At the same time, captions appeared on the remaining analogue channels reminding viewers of the impending switchover. Finally, the second stage saw the remaining analogue transmissions switched off and the other high power multiplexes switched on. Initially, this occurred four weeks after stage one, but starting with the switchover at Mendip in April 2010 onwards, this gap was reduced to two weeks.

Three multiplexes (BBC A, D3&4, BBC B) are for public service broadcasting and are broadcast from all transmitter sites. They contain around 25 TV channels, half a dozen radio stations and half a dozen text/interactive services. These include all the television channels from the BBC, some from ITV and Channel 4, Channel 5 and S4C (in Wales only). The other three multiplexes (SDN, Arqiva A, Arqiva B) are broadcast from main transmitter sites only and are operated by their respective commercial licence-holders. To reflect the slightly changed roles, the multiplex names were also changed:[25]

Old multiplex nameNew multiplex nameOwning company
1BBC ABBC
2D3&4Digital 3&4
ASDNS4C Digital Networks (ITV plc)
BBBC BBBC
CArqiva AArqiva
DArqiva BArqiva

Post-switchover[edit]

The adoption of the technically superior DVB-T format occurred in each region at the date of switchover. This resulted in no reception for viewers with older '2k' only equipment, such as former ONdigital/ITV Digital boxes, and other incompatible IDTVs and set top boxes.[26]

In the Meridian and Anglia regions, transmitters formed a single-frequency network when they were converted to all-digital operation.[27]

Alternative post-switchover multiplex designations were used on internal documentation by the BBC switchover contractor Arqiva,[28] but changing the designations of the multiplexes requires changes to legislation[2] and to the multiplex licences issued by Ofcom and is not in the current draft.[29]

When digital switchover was complete, two new sub-bands of the UHF spectrum were clear (frequencies corresponding to channel ranges 31–40 and 63–69), leaving only channels 21–30 and 41–62 for digital television multiplexes. This "digital dividend"[30] required millions of homes to upgrade their aerials to the wideband type to receive some or all of the Freeview multiplexes.[31] This spectrum is useful because of its trade-off between bandwidth and range. Following a consultation, in September 2011 Ofcom stated that an auction for the 600 MHz band will most likely lead to channels 31–37 being used for three new TV multiplexes; a reference transmission plan assumes two frequencies would be multiple-frequency networks, and channel 36 would be used as a national single-frequency network.[32] The remaining reallocated frequencies can be re-used for other services, for example the provision of:

  • Mobile Television services
  • wireless (mobile) broadband services
  • wider coverage for advanced services in remote and rural areas
  • more multiplexes carrying more channels
  • high definition (HD) services

The clearing and re-allocation of these channels of the spectrum for other services caused some controversy within technical industries, such as wireless microphones, as Ofcom decided to clear channel 69 (854–862 MHz) to match the rest of Europe and make the facilitation of future services easier.[33]

Further re-allocations of the other freed analogue television channels have not yet occurred, but when implemented will require legislation changes. It is likely that if they are sold commercially, they will not only attract interest, but may be bought for millions of pounds due to the high demand for spectrum throughout most of Europe. Ofcom have published further information about the auctioned channel in an announcement on their website.

OFCOM released their consultation of the future of the 600 MHz and 700 MHz UHF bands beyond 2018 on 16 November 2012.[34] This document recommends that the 600 MHz UHF band is allocated to DVB-T2 MPEG-4 Freeview HD services and Whitespace services, allowing a future migration of the existing 700 MHz Freeview allocation to 700 MHz mobile data services (synchronising the bandwidth usage with many other markets in Europe and globally).

Digit Al[edit]

Digit Al is a robot character created for Digital UK in 2005, by Abbott Mead Vickers BBDO and voiced by the English comedy actor Matt Lucas, used in material publicising the digital switchover. It appeared in the public information programme run by Digital UK until 2012. The character was first transmitted simultaneously on about 100 television channels and on regional BBC television on 5 May 2006.[35]

Digital Self-Help Relays[edit]

Terrestrial analogue relay stations have been repeating TV signals to areas not covered by broadcaster-owned transmitters since the Independent Broadcasting Authority started licensing them in 1980. Recently self-help groups have had to look into upgrading their old analogue transmitters to digital ones. The first digital self-help relay was installed at Ladram Bay, Devon by Stuart Harse and Liam Kelly (broadcast engineers from Bristol). The system was designed by Mike Rea of Taylor Transmitters, Oldham UK. The Ladram Bay TV repeater broadcasts all six mux signals from the Stockland Hill transmitter.

Post-switchover reorganisation and HD[edit]

In March 2006, the development of a new second generation digital terrestrial broadcasting standard, DVB-T2, was agreed by the DVB Group.

The BBC, ITV, Channel 4, S4C and Channel 5 agreed with the regulator Ofcom to convert one UK multiplex (B, or PSB3) to DVB-T2 to increase capacity for HDTV (High Definition Television) via DTT.[36] The first TV region to use the new standard was Granada in November 2009 (with existing switched over regions being changed at the same time). It is expected that over time there will be enough DVB-T2 receivers sold to switch all DTT transmissions to DVB-T2, and MPEG-4 Part 10.[citation needed]

From 27 October 2009, Multiplex B (PSB3) was cleared of SD channels in post DSO areas, which were moved to Multiplex 1 (PSB1). In pre DSO areas, Multiplex B continued to carry BBC Four, BBC Parliament, CBeebies, BBC Radio Stations and 301 until DSO. Former streams of 302 and News Multiscreen on Multiplex B were sublet to broadcasters other than the BBC for pre DSO areas only, and were not available at all in post DSO areas because of the new DVB-T2 HD multiplex as replacement.

On 3 April 2008, Ofcom published its final decision for the HDTV transmission format: DVB-T2 and MPEG-4.[37] Initially there were to be three HD services available: BBC HD, ITV HD/STV HD and Channel 4 HD/S4C Clirlun.[38] Channel 5 HD was due to launch during 2010 but was unable to reach 'key criteria' to keep its slot.[39][40] Spare allocation on multiplex B was handed over to the BBC, two years to the date when it was anticipated that further capacity on multiplex B would revert to the control of the BBC Trust. On 3 November 2010, BBC One HD launched on Freeview HD.[41] It is available in addition to the existing BBC HD channel. During 2011, Ofcom gave the Commercial Public Service Broadcasters another opportunity to apply to provide an additional HD service from 2012.[42]

List of digital terrestrial channels[edit]

Main article: List of DTT channels in the United Kingdom

Multiplexing[edit]

The multiplexes[edit]

Current multiplexes
Mux nameOperatorBroadcast modeBit-rateNotesNon-exhaustive list of channels[43]
pre-switchoverpost-switchover license namepost-switchover operating namepre-switchoverpost-switchoverpre-switchoverpost-switchover
Multiplex 1PSB1BBC ABBC16-QAM64-QAM18 Mbit/s24 Mbit/sCarries all non-HD BBC channelsBBC1, BBC2, BBC4, BBC News
Multiplex 2PSB2D3&4Digital 3&4
(an ITV / Channel 4 consortium)		64-QAM64-QAM24 Mbit/s24 Mbit/sITV, Channel 4, Channel 5, ITV2, E4, Film4
Multiplex ACOM4SDNSDN
(owned by ITV plc)		64-QAM64-QAM24 Mbit/s24 Mbit/sQuest, QVC, Drama, 5USA, Horror Channel
Multiplex BPSB3BBC BBBC16-QAM256-QAM18 Mbit/s40 Mbit/sHD services.
Transmits MPEG4 data using DVB-T2 (rather than MPEG2/DVB-T as used on other multiplexes).		BBC1 HD, BBC2 HD, ITV HD, Channel 4 HD, Channel 5 HD
Multiplex CCOM5ARQ AArqiva16-QAM64-QAM18 Mbit/s27 Mbit/sPick, Really, Sky News
Multiplex DCOM6ARQ BArqiva16-QAM64-QAM18 Mbit/s27 Mbit/sIdeal World, Yesterday, RT, Aljaazera
N/ACOM7ARQ CArqivaN/A256-QAMN/A40 Mbit/sHD services.
Transmits MPEG4 data using DVB-T2 (rather than MPEG2/DVB-T as used on other multiplexes).		FreeSports, BBC4 HD, BBC News HD, RT HD
Former multiplexes
Mux nameOperatorBroadcast modeBit-rateNotesCeased
License nameOperating name
COM8ARQ DArqiva256-QAM40 Mbit/sHD services, MPEG422 June 2020

In 2014, Ofcom decided to reallocate the frequency band used by COM7 and COM8 to make it available for mobile communications. This project, known as "700Mhz clearance", was intended to be complete by the second quarter of 2020;[44] as of June 2020 the switch-off is largely complete but the remaining transmitter changes are postponed due to the COVID-19 pandemic.[45] Channels broadcast on the COM8 multiplex were cleared by Arqiva on 22 June 2020, with some services moving to broadcast from COM7 or PSB3.[46]

Use of multiplexing technology[edit]

Each multiplex is an error-protected bitstream of 24, 27 or 40 megabits per second, which can be used for almost any combination of digitally-encoded video, audio and data. The DVB-T standard provides a multiplex service that can make trade-offs between the number of services and the picture and audio quality.

  • a number of services use the same bandwidth at different times. For example, CBeebies and BBC Four currently use the same space in their multiplex, with CBeebies broadcasting from 6 am until 7 pm and BBC Four from 7 pm.
  • some multiplexes allocate more bandwidth to services, providing a smaller number of higher-quality services.
  • The modulation of the multiplexes can be varied to squeeze higher digital bitrates out of the same portion of the electromagnetic spectrum, but require a stronger signal for good reception. The modulation schemes used in the UK are, in order of bandwidth efficiency, each with a progressively higher bitrate, at the cost of progressively higher likelihood of signal degradation:
    • QPSK (only used for tests in the Oxford and London areas)
    • 16-QAM (no longer used as of digital switchover)
    • 64-QAM (only used on the DVB-T multiplex)
    • 256-QAM (only used on the DVB-T2 multiplex)
    • 1024-QAM
    • 2048-QAM (currently in development)
By late 2009, multiplexes 2 and A used 64-QAM and were consequently more prone to poor reception, while the other multiplexes used 16-QAM. At switchover the transmission mode was changed from 16-QAM to 64-QAM on Multiplex 1 (PSB1),[25] increasing the effective bandwidth of the multiplex. The switch to 64-QAM mode also provided extra bandwidth on Multiplexes C (COM5) and D (COM6).
By late 2012, the digital switchover was complete, with all DVB-T multiplexes using 64-QAM. The switchover allowed the transmitters to broadcast at a higher power level, reducing the likelihood of reception errors when receiving 64-QAM encoded broadcasts.
  • Multiplexes can make use of statistical multiplexing at the MPEG video coder whereby the bitrate allocated to a channel within the multiplex can vary dynamically depending on how difficult it is to code the picture content at that precise time, and how much demand there is for bandwidth from other channels. In this way, complex pictures with much detail may demand a higher bitrate at one instant and this can result in the bitrate allocated to another channel in the same multiplex being reduced if the second channel is currently transmitting pictures which are easier to encode, with less fine detail.

Improvements in compression technology[edit]

Developments in statistical multiplexing, improved compression technology, and, in some cases, an acceptance of lower quality or lower resolution broadcasts, allowed gradual increases in the number of services carried on digital terrestrial television multiplexes.

As the number of homes receiving digital terrestrial grew, the interest in new channel capacity increased. In 2005, the auction for two new slots on National Grid Wireless multiplex D resulted in broadcasters bidding high prices to gain bandwidth. ITV won the bidding for the first slot (on which it launched Men & Motors on 2 May 2005, replaced by ITV Play and later ITV2+1), and Channel 4 the second. Channel 4 launched E4 +1 (not its new channel More4) on the multiplex when the slot became available on 1 June (E4 launched on Freeview on 27 May 2005). National Grid Wireless made an additional new slot available on Multiplex D using the new compression techniques. The 18-hour channel, running from 6 am to midnight[citation needed], became available on 1 December 2005. Companies interested had until 1 November to submit their bids, with bids said to have reached £10 million, from an entry level of £5.5 million, with 12 separate bidders covering all sectors of broadcasting. This slot was won by Channel 4; it was occupied by More4+1 until live coverage of Big Brother replaced it on 18 May 2006. Film4 took over the slot 23 July 2006.

Later compression technology, implemented in codecs like MPEG4, H.264 or VC-1, can enable a substantial increase in either quality or capacity due to their increased efficiency, but use of such technologies would again require most viewers to purchase new reception equipment, since the vast majority of standard set-top boxes support only the older MPEG2 encoding. BSkyB were the first to suggest such a move to increase the number of channels available within their own share of space using MPEG4 on a subscription service.[47] However, BSkyB's proposals were ultimately shelved following regulatory delays.[48]

The BBC, which ultimately broadcast high-definition television on Freeview in the DVB-T2 format adopted in 2009, initially considered an alternative method utilising spare capacity at night to allow the download of high definition programmes for later replay. In addition the BBC's Research and Development team invented a transmission method that doubles the effective bandwidth that could currently be delivered by each multiplex using "spatial multiplexing". While conventional analogue and digital terrestrial television signals are transmitted either vertically or horizontally polarised (providing protection against interference from other distant signals which may be transmitted on the same frequency, but will usually be planned to use the opposite polarisation), the proposed technique would have involved using the same frequency to transmit two different signals at once, one vertically and one horizontally polarised. A special receiving aerial, containing both vertically and horizontally polarised elements, could receive both signals simultaneously and feed these to a suitable set top box, but would require new transmitters and receiving equipment and aerials; the technique was ultimately not adopted.[citation needed]

See also[edit]

  • Digital television in the United Kingdom
  • Top Up TV
  • BT TV
  • Freesat
  • High-definition television in the United Kingdom
  • List of British television channels

References[edit]

  1. ^ http://stakeholders.ofcom.org.uk/binaries/research/tv-research/no3factsheet.pdf
  2. ^ a b "Broadcasting Act 1996". Office of Public Sector Information. Archived from the original on 13 February 2007. Retrieved 3 April 2007.
  3. ^ "Digital 3 and 4 Ltd Response document (page 4)" (DOC). Ofcom. Retrieved 26 April 2007.
  4. ^ "A comprehensive guide to Digital Broadcasting". Published Papers. BBC Research. Retrieved 3 April 2007.
  5. ^ a b "ITV plc acquires SDN Limited" (Press release). ITV plc. 27 April 2005. Archived from the original on 29 September 2007. Retrieved 3 April 2007.
  6. ^ "five unveils two new channels" (Press release). five.tv. 5 June 2006. Archived from the original on 14 March 2007. Retrieved 3 April 2007.
  7. ^ Chris Tryhorn (19 April 2006). "Broadcasters get green light for more pay-TV". Guardian Unlimited. London. Retrieved 3 April 2007.
  8. ^ "Sky's top shows to go terrestrial". BBC News. 8 February 2007. Retrieved 3 April 2007.
  9. ^ Richard Wray (5 October 2007). "Fresh rebuff for BSkyB over Freeview pay-TV". Guardian Unlimited. London. Retrieved 18 October 2007.
  10. ^ Sweney, Mark (14 August 2008). "Freeview upgrade leaves set-top boxes obsolete". The Guardian. London. Retrieved 25 August 2008.
  11. ^ "Freeview boxes destined for landfill". FrequencyCast. Retrieved 25 August 2008.
  12. ^ "Archived copy" (PDF). Archived from the original (PDF) on 9 September 2008. Retrieved 9 July 2008.CS1 maint: archived copy as title (link)
  13. ^ "Archived copy". Archived from the original on 25 April 2012. Retrieved 1 October 2012.CS1 maint: archived copy as title (link)
  14. ^ UK government press release
  15. ^ https://web.archive.org/web/20080226220658/http://www.digitaluk.co.uk/en/news-media/pressReleases/019/file/DigitalUK161006.pdf
  16. ^ Whitehaven News article on Five digital launch, 6 September 2007
  17. ^ North-West Evening Mail article on Eskdale reception problems, 14 November 2007 Barrow in furness, barrow news sport
  18. ^ Whitehaven area experiences of switchover problems
  19. ^ "BBC and Arqiva take major step towards Digital Switch Over" (Press release). BBC. 18 September 2006. Retrieved 3 April 2007.
  20. ^ "Communications Act 2003". Office of Public Sector Information. Archived from the original on 1 May 2007. Retrieved 3 April 2007.
  21. ^ "Digital switchover: an audit of viewers' priorities, §6.31" (PDF). Ofcom. 12 July 2006. Archived from the original (PDF) on 27 September 2007. Retrieved 18 October 2007.
  22. ^ Self help TV relays and digital switchover Archived 27 November 2007 at the Wayback Machine Ofcom consultation document
  23. ^ "Countdown to UK's first switch begins" (PDF) (Press release). Digital UK. 15 March 2007. Archived from the original (PDF) on 22 April 2007. Retrieved 25 April 2007.
  24. ^ "BBC Two first to go fully digital". BBC News. 9 November 2005. Retrieved 3 April 2007.
  25. ^ a b "Digital Switchover Transmitter Details: Border Region" (PDF). Ofcom. Archived from the original (PDF) on 5 June 2007. Retrieved 6 April 2007.
  26. ^ "Equipment issues: 2k equipment" (PDF). digitaluk.co.uk. March 2011. Archived from the original (PDF) on 17 February 2012.
  27. ^ "Planning Options for Digital Switchover : Statement". Ofcom. Archived from the original on 14 October 2007. Retrieved 18 October 2007.
  28. ^ http://www.arqiva.com/news/
  29. ^ "Switchover related Changes to DTT Licences". Ofcom. Archived from the original on 30 September 2007. Retrieved 3 April 2007.
  30. ^ "The Ofcom Digital Dividend Review (DDR)". Ofcom. Archived from the original on 30 September 2007. Retrieved 3 April 2007.
  31. ^ "House of Lords – BBC Charter Review – Second Report". Retrieved 3 April 2007.
  32. ^ "Ofcom 600 MHz band and geographic interleaved spectrum". Retrieved 23 September 2011.
  33. ^ "Information on the 2012 DSO and how it affects Radio Microphone users". shure.co.uk. Shure. Retrieved 8 October 2011.
  34. ^ "Securing long term benefits from scarce low frequency spectrum" (PDF). Ofcom. Retrieved 19 November 2012.
  35. ^ "Little Britain star goes digital". BBC News. 4 May 2006. Retrieved 4 May 2006.
  36. ^ "3 Freeview HD channels will start 2009 – ukfree.tv – independent digital television and switchover advice, since 2002". Retrieved 25 November 2007.
  37. ^ "Ofcom Statement on DTT future, announced on April 3, 2008". Retrieved 7 April 2012.
  38. ^ "Broadcasters awarded licences for HD programmes on Digital Terrestrial TV". Ofcom. 7 April 2012. Archived from the original on 18 September 2012.
  39. ^ "Channel 5 set for licence for high definition programmes on digital terrestrial television". Ofcom. 11 June 2009. Archived from the original on 14 June 2009.
  40. ^ "Ofcom hands Five's Freeview HD slot back to BBC". Tech Radar. 15 May 2010.
  41. ^ "BBC One HD Channel to launch 3 November and EastEnders to go HD on Christmas Day". BBC. 21 October 2010.
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  43. ^ "Freeview multiplex listings". ukfree.tv. Retrieved 12 August 2020.
  44. ^ "700 MHz clearance programme timescale review" (PDF). Ofcom. 12 October 2017. Retrieved 26 June 2020.
  45. ^ "What is 700MHz clearance?". freeview.co.uk. Retrieved 26 June 2020.
  46. ^ "DTT Changes 20th June 2020". www.cai.org.uk. Retrieved 28 June 2020.
  47. ^ Osborne, Alistair (9 February 2007). "Freeview to lose Sky channels". London: Telegraph.co.uk. Retrieved 18 October 2007.
  48. ^ Sweney, Mark (12 September 2008). "BSkyB job losses expected as Picnic is shelved". The Guardian. London. Retrieved 1 May 2010.

External links[edit]

Official sites[edit]

  • Digital Switchover UK
  • BBC – Digital – Homepage
  • BBC – Digital – Switchover
  • Freeview official site
  • Top Up TV
  • DigitalUK
  • Ofcom's list of the current licensed digital television services
  • Digital TV Consumer test reports UK Government-funded website to support Digital Switchover

Other sites[edit]

  • Details of all UK digital transmitters
  • Simon Blackham's DTT Page
  • Switchover guide and podcast
  • UK transmitters: history and plans
  • How to Find Your Local UK Transmitter