Digital television: Difference between revisions

{{More citations needed|date=May 2010}}

'''Digital television''' ('''DTV''') is the transmission of [[television]] signals using [[Digital signal|digital]] encoding, in contrast to the earlier [[analog television]] technology which used [[analog signal]]s. In the 2000s<ref>{{Cite web |date=2008-12-22 |title=The Origins and Future Prospects of Digital Television |url=https://www.benton.org/initiatives/obligations/charting_the_digital_broadcasting_future/sec1 |access-date=2025-07-06 |website=Benton Foundation |language=en}}</ref> it was represented as the first significant evolution in television technology since [[color television]] in the 1950s.<ref>{{cite book |last=Kruger |first=Lennard G. |year=2002 |title=Digital Television: An Overview |location=New York |publisher=Nova Publishers |isbn=1-59033-502-3 |url=https://books.google.com/books?id=BIAfWq2V3wgC}}</ref> Modern digital television is transmitted in [[high-definition television]] (HDTV) with greater resolution than analog TV. It typically uses a [[widescreen]] aspect ratio (commonly [[16:9]]) in contrast to the narrower format ([[4:3]]) of analog TV. It makes more economical use of scarce [[radio spectrum]] space; it can transmit up to seven channels in the same [[Bandwidth (signal processing)|bandwidth]] as a single analog channel,<ref>{{cite web |url=http://www.disabled-world.com/artman/publish/digital-hdtv.shtml |title=HDTV Set Top Boxes and Digital TV Broadcast Information |access-date=28 June 2014 |archive-url=http://arquivo.pt/wayback/20160522191336/http://www.disabled%2Dworld.com/artman/publish/digital%2Dhdtv.shtml |archive-date=22 May 2016 |url-status=dead}}</ref> and provides many new features that analog television cannot. A [[digital television transition|transition from analog to digital broadcasting]] began around 2000. Different digital television broadcasting standards have been adopted in different parts of the world; below are the more widely used standards:

* [[Digital Video Broadcasting]] (DVB) uses coded [[orthogonal frequency-division multiplexing]] (OFDM) modulation and supports hierarchical transmission. This standard has been adopted in Europe, Africa, Asia and Australia, for a total of approximately 60 countries.

Digital television's roots in the 1990s are tied to the availability of inexpensive, high-performance [[computer]]s that can compress video.<ref name="benton">{{cite web |url= http://www.benton.org/initiatives/obligations/charting_the_digital_broadcasting_future/sec1 |title= The Origins and Future Prospects of Digital Television |publisher= [[Benton Foundation]] |date= 2008-12-23 }}</ref> Digital television was previously impractical due to high [[Bandwidth (computing)|bandwidth]] requirements of [[uncompressed video]],<ref name="Lea">{{cite book |last1=Lea |first1=William |title=Video on demand: Research Paper 94/68 |date=1994 |publisher=[[House of Commons Library]] |url=https://researchbriefings.parliament.uk/ResearchBriefing/Summary/RP94-68 |access-date=20 September 2019}}</ref><ref name="Barbero">{{cite journal |last1=Barbero |first1=M. |last2=Hofmann |first2=H. |last3=Wells |first3=N. D. |title=DCT source coding and current implementations for HDTV |journal=EBU Technical Review |date=14 November 1991 |issue=251 |pages=22–33 |publisher=[[European Broadcasting Union]] |url=https://tech.ebu.ch/publications/trev_251-barbero |access-date=4 November 2019}}</ref> requiring around {{val|200|ul=Mbit/s}} for a [[standard-definition television]] (SDTV) signal,<ref name="Lea"/> and over {{val|1|ul=Gbit/s}} for [[high-definition television]] (HDTV).<ref name="Barbero"/>

In the mid-1980s, [[Toshiba]] commercially released one of the first [[television set|television sets]] with digital capabilities, using [[integrated circuit]] chips such as a [[microprocessor]] to convert analog television broadcast signals to [[digital video]] signals, enabling features such as freezing pictures and [[Picture-in-picture|showing two channels at once]]. Following in 1986, [[Sony]] and [[NEC Home Electronics]] announced their own similar TV sets with digital video capabilities. However, these television sets still relied on analog TV broadcast signals, with true digital TV broadcasts not yet being available at the time.<ref>{{cite magazine |last1=Meigs |first1=James B. |title=Home Video: Get set for digital |magazine=[[Popular Mechanics]] |date=June 1986 |volume=163 |issue=6 |page=52 |url=https://books.google.com/books?id=H-MDAAAAMBAJ |publisher=[[Hearst Magazines]] |issn=0032-4558}}</ref><ref>{{cite magazine |last1=Bateman |first1=Selby |title=New Technologies: The Converging Digital Universe |magazine=[[Compute!]] |date=April 1986 |issue=71 |pages=21-29 (26-8) |url=https://archive.org/details/1986-04-compute-magazine/page/n27}}</ref>

Simultaneously, between 1988 and 1991, European organizations: CMMT, ETSI, etc. were working on [[Discrete cosine transform|DCT]]-based digital [[video coding standards]] for both SDTV and HDTV. The EU 256 project by the CMTT and [[ETSI]], along with research by Italian broadcaster [[RAI]], developed a DCT [[video codec]] that broadcast SDTV at {{val|34|u=Mbit/s}} and near-studio-quality HDTV at about {{nowrap|70{{ndash}}140 Mbit/s}}. RAI demonstrated this with a [[1990 FIFA World Cup]] broadcast in March 1990.<ref name="Barbero"/><ref>{{cite journal |last1=Barbero |first1=M. |last2=Stroppiana |first2=M. |title=Data compression for HDTV transmission and distribution |journal=IEE Colloquium on Applications of Video Compression in Broadcasting |date=October 1992 |pages=10/1–10/5 |url=https://ieeexplore.ieee.org/document/193745}}</ref>  

Simultaneously, in March 1990, American company [[General Instrument]] demonstrated the feasibility of a digital television signal; persuading the FCC to delay its decision on an advanced television (ATV) standard until a digitally based standard could be developed; resulting in several actions. First, the FCC declared that the new TV standard must be more than an enhanced [[analog signal]], capable of providing a genuine HDTV signal with at least twice the resolution of existing television images. Second, to ensure that viewers who did not wish to buy a new digital television set could continue to receive conventional television broadcasts, it dictated that the new ATV standard must be capable of being [[simulcast]] with [[NTSC]] on different channels. The new ATV standard also allowed the new DTV signal to be based on entirely new design principles incorporating many improvements over existing analog television.<ref name="benton" />

[[DirecTV]] in the US launched the first commercial digital [[satellite television|satellite]] platform in May 1994, using the [[Digital Satellite System]] (DSS) standard.<ref>{{cite web|url=http://www.fundinguniverse.com/company-histories/u-s-satellite-broadcasting-company-inc-history/|title=History of U.S. Satellite Broadcasting Company, Inc. – FundingUniverse|website=www.fundinguniverse.com|access-date=9 August 2018}}</ref><ref>{{cite web|url=https://eu.indystar.com/story/money/2015/09/04/business-insider-digital-satellite-tv-indy-roots/71611606/|title=Business Insider: Digital satellite TV has Indy roots|access-date=9 August 2018}}</ref> [[Digital cable]] broadcasts were tested and launched in the US in 1996 by [[Tele-Communications Inc.|TCI]] and [[Time Warner]].<ref>{{cite web|url=https://money.cnn.com/1997/12/17/technology/nextlevel/|title=NextLevel signs cable deal - Dec. 17, 1997|website=money.cnn.com|access-date=9 August 2018}}</ref><ref>{{cite web|url=https://money.cnn.com/1996/08/15/companies/tci_pkg/|title=TCI faces big challenges - Aug. 15, 1996|website=money.cnn.com|access-date=9 August 2018}}</ref> The first [[digital terrestrial]] platform was launched in November 1998 as [[ONdigital]] in the UK, using the [[DVB-T]] standard.<ref>{{cite web|url=http://www.onhistory.co.uk/timeline/1998/11/10/canal-technologies-and-worlds-first-digital-terres|title=CANAL+ TECHNOLOGIES and the world's first digital terrestrial television service in the United Kingdom|access-date=9 August 2018}}</ref>