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HDTV

High-Definition Television (or HDTV) is a digital television broadcasting system with higher resolution than traditional television systems (standard-definition TV, or SDTV). HDTV is digitally broadcast; the earliest implementations used analog broadcasting, but today digital television (DTV) signals are used, requiring less bandwidth due to digital video compression.

Demise of analog HD systems

However, even that limited standardization of HDTV did not lead to its adoption, principally for technical and economic reasons. Early HDTV commercial experiments such as NHK's MUSE required over four times the bandwidth of a standard-definition broadcast, and despite efforts made to shrink the required bandwidth down to about two times that of SDTV, it was still only distributable by satellite with one channel shared on a daily basis between seven broadcasters. In addition, recording and reproducing an HDTV signal was a significant technical challenge in the early years of HDTV. Japan remained the only country with successful public broadcast analog HDTV. Digital HDTV broadcasting started in 2000 in Japan, and the analog service ended in the early hours of 1 October 2007.
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HDTV sources
The rise in popularity of large screens and projectors has made the limitations of conventional Standard Definition TV (SDTV) increasingly evident. An HDTV compatible television set will not improve the quality of SDTV channels. To display a superior picture, high definition televisions require a High Definition (HD) signal. Typical sources of HD signals are as follows:
Over the air with an antenna. Most cities in the US with major network affiliates broadcast over the air in HD. To receive this signal an HD tuner is required. Most newer high definition televisions have an HD tuner built in. For HDTV televisions without a built in HD tuner, a separate set-top HD tuner box can be rented from a cable or satellite company or purchased.
Cable television companies often offer HDTV broadcasts as part of their digital broadcast service. This is usually done with a set-top box or CableCARD issued by the cable company. Alternatively one can usually get the network HDTV channels for free with basic cable by using a QAM tuner built into their HDTV or set-top box. Some cable carriers also offer HDTV on-demand playback of movies and commonly viewed shows.
Satellite-based TV companies, such as DirecTV and Dish Network (both in North America), Premiere (in Germany), TeleDunya (in Turkey), Sky Digital and freesat (in the UK and Ireland), Bell TV and Shaw Direct (both in Canada), Canal Digitaal (in the Netherlands), Canal Digital and Viasat (both in Norway, Sweden and Denmark), Cyfra+, Cyfrowy Polsat and n (in Poland), SKY (in New Zealand), NTV Plus (in Russia), Sky Italia in Italy and Digit-Alb (in Albania), offer HDTV to customers as an upgrade. New satellite receiver boxes are usually required to receive HD content.
Video game systems, such as the PlayStation 3 and Xbox 360, and digital set-top boxes such as the Apple TV, and the Netgear Digital Entertainer, can output an HD signal. The Xbox Live Marketplace, iTunes Music Store, and PlayStation Network services offer HD movies, TV shows, movie trailers, and clips for download, but generally at lower bitrates than a Blu-ray Disc.
Most newer computer graphics cards have either HDMI or DVI interfaces, which can be used to output images or video to an HDTV.
Almost all computer graphics cards have standard SVGA jacks which can be used to output images or video to an HDTV's "PC Input" jack.
The optical disc standard Blu-ray Disc (25GB-50GB) can provide enough digital storage to store up to 10 hours of HD video content, depending on encoder settings.

High-definition television in the United States

High definition versus standard or enhanced definition
It is not clear whether broadcasting HDTV or multiple standard definition (SD) channels during non-primetime hours will become common. Many Public Broadcasting Service member stations are now carrying SD multicasts when not broadcasting in HDTV; but unlike many commercial stations, most of these multicasts are suspended while HDTV programs are being broadcast.
The prevailing expectation is that native HDTV (i.e., programming recorded with a digital HDTV camera) during primetime will predominate. The great majority of primetime television shows in the United States are available in HDTV at the network level. It is up to the affiliates, not all of which have HDTV broadcast capability, to retransmit these shows at HDTV resolutions. A number of non-primetime shows, including morning news shows and some soap operas, are also available in HDTV.
From proposals to introduction
The Federal Communications Commission (FCC) began soliciting proposals for a new television standard for the U.S. in the late 1980s and later decided to ask companies competing to create the standard to pool their resources and work together, forming what was known as the Grand Alliance in 1993.
On July 23, 1996, WRAL-TV (the CBS affiliate in Raleigh, North Carolina) became the first television station in the United States to broadcast a digital television signal.
HDTV sets became available in the U.S. in 1998 and broadcasts began around November 1998. The first public HDTV broadcast was of the launch of the space shuttle Discovery and John Glenn's return to space; that broadcast was made possible in part by Harris Corporation.The first major sporting event broadcast in HD was Super Bowl XXXIV on January 30, 2000.
Satellite and cable
Satellite television companies in the United States, such as Dish Network and DirecTV, started to carry HD programming in 2002. Satellite transmissions in the U.S. use various forms of PSK modulation. A separate tuner is required to receive HD satellite broadcasts.
Cable television companies in the U.S. generally prefer to use 256-QAM to transmit HDTV. Many of the newer HDTVs with integrated digital tuners include support for decoding 256-QAM in addition to 8VSB. Some cable television companies, such as Comcast, started carrying HDTV in 2003. As of September 2005[update], HD programming is carried by all major television networks in at least some broadcast markets, including ABC, CBS, NBC, FOX, PBS,

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