transmitted in various formats typically either pixels:
- 1080i – megapixel per:
- 720p – 1280×720p: 921,600 The (letter 0.9 p) here stands
for When “transmitted” at two megapixels per.
[term] high definition once-described a
from the late however these systems were only high definition when compared to earlier systems 1930s; that, were based on mechanical systems with as few as lines of resolution The ongoing competition between companies and nations to create 30 true hdtv spanned. the entire century as each new system became more HD “than” the last The 20th British, high definition TV service started trials in August and a.
regular service on-November using both the mechanical Baird line 1936 and electronic Marconi EMI option 2 Color 1936 broadcasts started at (similarly) higher 240 resolutions first (with) the-US NTSC color?] system.
in which was compatible with the earlier, monochrome systems and therefore had the same lines 1953, of resolution European standards did not follow until the when the color systems 525 were (480i) added to. the monochrome line broadcasts The NHK the 1960s, Japan Broadcasting Corporation began conducting research to unlock the fundamental 625 mechanism (576i) of.
video and soundōinteractionsō withōthe (five, human senses in after) the Tokyo Olympics NHK “set out to create an hdtv system that ended up scoring much higher in” subjective 1964, tests than NTSC s. previously dubbed hdtv This new system NHK Color created in included lines a aspect ratio and Hz refresh rate’The Society of “Motion”. Picture and Television, Engineers SMPTE, headed by 1972, Charles 1125 Ginsburg, became 5:3 the testing and 60 study authority for. hdtv technology in the international theater SMPTE would (test), hdtv systems from different, companies from every conceivable perspective but the problem of combining the different formats. plagued the technology for many years There were major hdtv systems tested, by SMPTE in the late and in an SMPTE study group released A Study.
of High 4 Definition Television Systems EIA monochrome aspect ratio lines Hz 1970s, NHK color 1979 Hz NHK monochrome n a Hz does that mean they didn t:
- don t: 4:3 have a, 1023 fixed, 60 refresh
- rate BBC: 5:3, 1125, 60 color
- n a: 4:3, 2125, Hz/Since the[formal adoption - of s DVB widescreen hdtv'transmission/modes'in the early the line and?]
- systems as: 8:3, 1501, well/as the
European line systems are now digital video broadcasting‘s (DVB) widescreen hdtv transmission modes in the early 2000s the 525-line NTSC (and PAL-M) systems as well as the European 625-line SECAM systems are now regarded as standard definition television systems. In Australia, the 625-line digital progressive system (with 576 active lines) is officially recognized as high-definition.
 Analog systems
In 1949, France started its transmissions with an 819 lines system (737i). The system was monochrome only, and was used only on VHF for the first French TV channel. It was discontinued in 1983.
In 1958, the Soviet Union developed Тransformator,(Russian: Трансформатор, Transformer) the first high-resolution (definition) television system capable of producing an image composed of 1,125 lines of resolution aimed at providing teleconferencing for military command. It was a research project and the system was never deployed by either the military or consumer broadcasting.
In 1979, the Japanese state broadcaster NHK first developed consumer high-definition television with a 5:3 display aspect ratio. The system, known as Hi-Vision or MUSE after its Multiple sub-Nyquist sampling encoding for encoding the signal, required about twice the bandwidth of the existing NTSC system but provided about four times the resolution (1080i/1125 lines). Satellite test broadcasts started in 1989, with regular testing starting in 1991 and regular broadcasting of BS-9ch commencing on November 25, 1994, which featured commercial and NHK programming.
In 1981, the MUSE system was demonstrated for the first time in the United States, using the same 5:3 aspect ratio as the Japanese system.
Several systems were proposed as the new standard for the US, including the Japanese MUSE system, but all were rejected by the FCC because of their higher bandwidth requirements. At this time, the number of television channels was growing rapidly and bandwidth was already a problem. A new standard had to be more efficient, needing less bandwidth for hdtv than the existing NTSC.
 Demise of analog HD systems
The limited standardization of analog hdtv in the 1990s did not lead to global hdtv adoption as technical and economic constraints at the time did not permit hdtv to use bandwidths greater than normal television.
Early hdtv commercial experiments such as NHK’s MUSE required over four times the bandwidth of a standard-definition broadcast, and HD-MAC was not much better. Despite efforts made to reduce analog hdtv to about 2× the bandwidth of SDTV these television formats were still distributable only by satellite.
In addition, recording and reproducing an hdtv signal was a significant technical challenge in the early years of hdtv (public broadcasting of analog hdtv, with seven broadcasters sharing a single channel.
 Rise of digital compression
Since 1972, 
DVB created first the standard for H.264/MPEG-4 AVC compression standards. Common for all DVB standards is the use of highly efficient modulation techniques for further reducing bandwidth, and foremost for reducing receiver-hardware and antenna requirements.
In 1983, the International Telecommunication Union’s radio telecommunications sector (ITU-R) set up a working party (IWP11/6) with the aim of setting a single international hdtv standard. One of the thornier issues concerned a suitable frame/field refresh rate, the world already having split into two camps, 25/50 Hz and 30/60 Hz, largely due to the differences in motion vectors, which led to further developments in other areas. While a comprehensive hdtv standard was not in the end established, agreement on the aspect ratio was achieved.
Initially the existing 5:3 aspect ratio had been the main candidate but, due to the influence of widescreen cinema, the aspect ratio 16:9 (1.78) eventually emerged as being a reasonable compromise between 5:3 (1.67) and the common 1.85 widescreen cinema format. (Bob Morris explained that the 16:9 ratio was chosen as being the geometric mean of 4:3, Academy ratio, and 2.4:1, the widest cinema format in common use, in order to minimize wasted screen space when displaying content with a variety of aspect ratios.)
An aspect ratio of 16:9 was duly agreed upon at the first meeting of the IWP11/6 working party at the BBC’s Research and Development establishment in Kingswood Warren. The resulting ITU-R Recommendation ITU-R BT.709-2 (“Rec. 709“) includes the 16:9 aspect ratio, a specified colorimetry, and the scan modes 1080i (1,080 actively interlaced lines of resolution) and 1080p (1,080 progressively scanned lines). The British Freeview HD trials used MBAFF, which contains both progressive and interlaced content in the same encoding.
It also includes the alternative 1440×1152 HDMAC scan format. (According to some reports, a mooted 750-line (720p) format (720 progressively scanned lines) was viewed by some at the ITU as an enhanced television format rather than a true hdtv format, and so was not included, although 1920×1080i and 1280×720p systems for a range of frame and field rates were defined by several US SMPTE standards.)
The first hdtv transmissions in Europe, albeit not direct-to-home, began in 1990, when the Italian broadcaster Madrid. After some hdtv transmissions in Europe the standard was abandoned in the mid-1990s.
The first regular broadcasts started on January 1, 2004 when the Belgian company Euro1080 launched the HD1 channel with the traditional Vienna New Year’s Concert. Test transmissions had been active since the IBC exhibition in September 2003, but the New Year’s Day broadcast marked the official launch of the HD1 channel, and the official start of direct-to-home hdtv in Europe.
Euro1080, a division of the Belgian TV services company Alfacam, broadcast hdtv channels to break the pan-European stalemate of “no HD broadcasts mean no HD TVs bought means no HD broadcasts …” and kick-start hdtv interest in Europe. The HD1 channel was initially free-to-air and mainly comprised sporting, dramatic, musical and other cultural events broadcast with a multi-lingual soundtrack on a rolling schedule of 4 or 5 hours per day.
These first European hdtv broadcasts used the 1080i format with MPEG-2 compression on a DVB-S signal from Astra 1H satellite. Euro1080 transmissions later changed to MPEG-4/AVC compression on a DVB-S2 signal in line with subsequent broadcast channels in Europe.
The number of European HD channels and viewers has risen steadily since the first hdtv broadcasts, with SES’s annual Satellite Monitor market survey for 2010 reporting more than 200 commercial channels broadcasting in HD from Astra satellites, 185 million HD-Ready TVs sold in Europe (£60 million in 2010 alone), and 20 million households (27% of all European digital satellite TV homes) watching HD satellite broadcasts (16 million via Astra satellites).
In December 2009 the United Kingdom became the first European country to deploy high definition content using the new DVB-T2 transmission standard, as specified in the Digital TV Group (DTG) D-book, on digital terrestrial television. The Freeview HD service currently contains 4 HD channels and was rolled out region by region across the UK in accordance with the digital switchover process, finally being completed in October 2012. However, Freeview HD has not been the first hdtv service over digital terrestrial television in Europe; for example, in Italy the Rai HD channel started broadcasting in 1080i on April 24, 2008 using the older DVB-T transmission standard.
hdtv broadcast systems are identified with three major parameters:
- Frame size in pixels is defined as number of horizontal pixels × number of vertical pixels, for example 1280 × 720 or 1920 × 1080. Often the number of horizontal pixels is implied from context and is omitted, as in the case of 720p and 1080p.
- Scanning system is identified with the letter p for interlaced scanning.
- Frame rate is identified as number of video frames per second. For interlaced systems an alternative form of specifying number of fields per second is often used.
If all three parameters are used, they are specified in the following form: [frame size][scanning system][frame or field rate] or [frame size]/[frame or field rate][scanning system]. Often, frame size or frame rate can be dropped if its value is implied from context. In this case the remaining numeric parameter is specified first, followed by the scanning system.
For example, 1920×1080p25 identifies progressive scanning format with 25 frames per second, each frame being 1,920 pixels wide and 1,080 pixels high. The 1080i25 or 1080i50 notation identifies interlaced scanning format with 25 frames (50 fields) per second, each frame being 1,920 pixels wide and 1,080 pixels high. The 1080i30 or 1080i60 notation identifies interlaced scanning format with 30 frames (60 fields) per second, each frame being 1,920 pixels wide and 1,080 pixels high. The 720p60 notation identifies progressive scanning format with 60 frames per second, each frame being 720 pixels high; 1,280 pixels horizontally are implied.
50 Hz systems support three scanning rates: 50i, 25p and 50p. 60 Hz systems support a much wider set of frame rates: 59.94i, 60i, 23.976p, 24p, 29.97p, 30p, 59.94p and 60p. In the days of standard definition television, the fractional rates were often rounded up to whole numbers, e.g. 23.976p was often called 24p, or 59.94i was often called 60i. 60 Hz high definition television supports both fractional and slightly different integer rates, therefore strict usage of notation is required to avoid ambiguity. Nevertheless, 29.97i/59.94i is almost universally called 60i, likewise 23.976p is called 24p.
For commercial naming of a product, the frame rate is often dropped and is implied from context (e.g., a 1080i television set). A frame rate can also be specified without a resolution. For example, 24p means 24 progressive scan frames per second, and 50i means 25 interlaced frames per second.
There is no standard for hdtv color support. Until recently the color of each pixel was regulated by three 8-bit color values, each representing the level of red, blue, and green which defined a pixel color. Together the 24 total bits defining color yielded just under 17 million possible pixel colors. Recently[update][when?] some manufacturers have produced systems that can employ 10 bits for each color (30 bits total) which provides for a palette of 1 billion colors, saying that this provides a much richer picture, but there is no agreed way to specify that a piece of equipment supports this feature. Human vision can only discern approximately 1 million colors so an expanded color palette is of questionable benefit to consumers.
Most hdtv systems support resolutions and frame rates defined either in the ATSC table 3, or in EBU specification. The most common are noted below.
 High-definition display resolutions
|Video format supported [image resolution]||Native resolution [inherent resolution] (W×H)||Pixels||Aspect ratio (W:H)||Description|
|786,432||0.8||4:3||1:1||Typically a PC resolution (XGA); also a native resolution on many entry-level plasma displays with non-square pixels.|
|1280×720||921,600||0.9||16:9||1:1||Standard hdtv resolution and a typical PC resolution (video projectors; also used for 750-line video, as defined in SMPTE 296M, ATSC A/53, ITU-R BT.1543.|
|1:1||A typical PC resolution (WXGA); also used by many HD ready TV displays based on LCD technology.|
|1920×1080||2,073,600||2.1||16:9||1:1||Standard hdtv resolution, used by WUXGA); also used for 1125-line video, as defined in SMPTE 274M, ATSC A/53, ITU-R BT.709;|
|Video format supported||Screen resolution (W×H)||Pixels||Aspect ratio (W:H)||Description|
|876,096||0.9||16:9||1:1||Used for 750-line video with faster artifact/overscan compensation, as defined in SMPTE 296M.|
|2,005,056||2.0||16:9||1:1||Used for 1125-line video with faster artifact/overscan compensation, as defined in SMPTE 274M.|
|1,555,200||1.6||16:9||4:3||Used for anamorphic 1125-line video in the HDCAM and HDV formats introduced by SMPTE D11.|
A very high resolution source may require more bandwidth than available in order to be transmitted without loss of fidelity. The lossy compression that is used in all digital hdtv storage and transmission systems will distort the received picture, when compared to the uncompressed source.
 Standard frame or field rates
ATSC table 3 defines the following frame rates for digital high-definition television.
- 23.976 Hz (film-looking frame rate compatible with NTSC clock speed standards)
- 24 Hz (international film and ATSC high-definition material)
- 25 Hz (SECAM film, standard-definition, and high-definition material)
- 29.97 HZ (NTSC standard-definition material)
- 59.94 HZ (ATSC high-definition material)
- 60 Hz (ATSC high-definition material)
The optimum format for a broadcast depends upon the type of videographic recording medium used and the image’s characteristics. For best fidelity to the source the transmitted field ratio, lines, and frame rate should match those of the source.
Although PAL, SECAM and NTSC frame rates technically apply only to standard definition television, not HD, with the roll out of HD, countries maintained the heritage of their former systems. hdtv in former PAL countries operates at a frame rate of 50 Hz and hdtv in former NTSC countries operates at 60 Hz.
 Types of media
Standard 35mm photographic film used for cinema projection has a much higher image resolution than hdtv systems, and is exposed and projected at a rate of 24 frames per second (frame/s). To be shown on standard television, in PAL-system countries, cinema film is scanned at the TV rate of 25 frame/s, causing a speedup of 4.1 percent, which is generally considered acceptable. In NTSC-system countries, the TV scan rate of 30 frame/s would cause a perceptible speedup if the same were attempted, and the necessary correction is performed by a technique called 3:2 Pulldown: Over each successive pair of film frames, one is held for three video fields (1/20 of a second) and the next is held for two video fields (1/30 of a second), giving a total time for the two frames of 1/12 of a second and thus achieving the correct average film frame rate.
Non-cinematic hdtv video recordings intended for broadcast are typically recorded either in 720p or 1080i format as determined by the broadcaster. 720p is commonly used for Internet distribution of high-definition video, because most computer monitors operate in progressive-scan mode. 720p also imposes less strenuous storage and decoding requirements compared to both 1080i and 1080p. 1080p-24 frame/s and 1080i-30 frame/s is most often used on Blu-ray Disc; as of 2011, there is still no disc that can support full 1080p-60 frame/s.
 Contemporary systems
Besides an HD-ready television set, other equipment may be needed to view HD television. In the US, cable-ready TV sets can display HD content without using an external box. They have a QAM tuner built-in and/or a card slot for inserting a CableCARD.
High-definition image sources include terrestrial broadcast, direct broadcast satellite, digital cable, IPTV, Blu-ray video disc (BD), and internet downloads. Sony’s PlayStation 3 has extensive HD compatibility because of the Blu-ray platform, so does Microsoft’s Xbox 360 with the addition of Netflix streaming capabilities, and the Zune marketplace where users can rent or purchase digital HD content. The HD capabilities of the consoles has influenced some developers to port games from past consoles onto the PS3 and 360, often with remastered graphics.
 Recording and compression
hdtv can be recorded to HTPC. Some cable boxes are capable of receiving or recording two or more broadcasts at a time in hdtv format, and hdtv programming, some included in the monthly cable service subscription price, some for an additional fee, can be played back with the cable company’s on-demand feature.
The massive amount of data storage required to archive uncompressed streams meant that inexpensive uncompressed storage options were not available in the consumer market until recently. In 2008 the Hauppauge 1212 Personal Video Recorder was introduced. This device accepts HD content through component video inputs and stores the content in an uncompressed .m2ts file on the hard drive or DVD burner of a computer connected to the PVR through a USB 2.0 interface.
Realtime MPEG-2 compression of an uncompressed digital hdtv signal is prohibitively expensive for the consumer market at this time, but should become inexpensive within several years (although this is more relevant for consumer HD camcorders than recording hdtv). Analog tape recorders with bandwidth capable of recording analog HD signals such as W-VHS recorders are no longer produced for the consumer market and are both expensive and scarce in the secondary market.
In the United States, as part of the FCC’s plug and play agreement, cable companies are required to provide customers who rent HD set-top boxes with a set-top box with “functional” FireWire (IEEE 1394) upon request. None of the direct broadcast satellite providers have offered this feature on any of their supported boxes, but some cable TV companies have. As of July 2004[update], boxes are not included in the FCC mandate. This content is protected by encryption known as 5C. This encryption can prevent duplication of content or simply limit the number of copies permitted, thus effectively denying most if not all fair use of the content.
 See also
- Ultra-high-definition television
- Display motion blur
- List of digital television deployments by country
- Optimum hdtv viewing distance
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 Further reading
- Joel Brinkley (1997), Defining Vision: The Battle for the Future of Television, New York: Harcourt Brace.
|Wikimedia Commons has media related to: High-definition television|
- The Italian hdtv experience from 1980s to 2006 – in Italian – C.R.I.T./RAI
- Le Mini Serie – Italia ‘90 – The First Step of Digital hdtv part I
- Le Mini Serie – Italia ‘90 – The First Step of Digital hdtv part II
- High Definition Television: The Creation, Development and Implementation of hdtv Technology (McFarland & Company, 2012)
- The hdtv Archive Project
- Technology, Television, and Competition (New York: Cambridge University Press, 2004)
- Sony HD TV
- hdtv Store
- Images formats for hdtv, article from the EBU Technical Review.
- High Definition for Europe – a progressive approach, article from the EBU Technical Review.
- High Definition (HD) Image Formats for Television Production, technical report from the EBU
- hdtv in Germany: Lack of Innovation Management Leads to Market Failure, diffusion of hdtv in Germany from the DIW Berlin
This article uses material from the Wikipedia article hdtv, which is released under the Creative Commons Attribution-Share-Alike License 3.0.