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High-definition television (HDTV) refers to the broadcasting of television signals with a significantly higher resolution than traditional formats (NTSC, SECAM, PAL) allow. Except for early analog formats in Europe and Japan, HDTV is broadcast digitally, and therefore its introduction sometimes coincides with the introduction of digital television (DTV): this technology was first introduced in the USA during the 1990s, by the Digital HDTV Grand Alliance (grouping together AT&T, General Instrument, MIT, Philips, Sarnoff, Thomson, and Zenith)^[1].

While a number of high-definition television standards have been proposed or implemented on a limited basis, the current HDTV standards are defined as 1080 active interlaced or progressive lines, or 720 progressive lines, using a 16 : 9 aspect ratio in ITU-R BT.709. The term "high-definition" can refer to the resolution specifications themselves, or to media capable of similar sharpness such as movie film.

Contents 1 Notation 1.1 Changes in notation 1.2 Standard resolutions 1.3 Standard frame or field rates 2 Comparison to SDTV 2.1 Close-up view 3 Format considerations 4 Technical details 5 Advantages of HDTV expressed in non-engineering terms 6 Early systems 7 Contemporary systems 7.1 Asia 7.1.1 Hong Kong 7.1.2 Japan 7.1.3 Republic of Korea 7.1.4 Singapore 7.2 Australia 7.3 Europe 7.4 North America 7.4.1 Canada 7.4.2 Mexico 7.4.3 Guatemala 7.4.4 United States 7.5 South America 7.5.1 Argentina 7.5.2 Brazil 7.5.3 Uruguay 8 Recording and compression 9 Table of terrestrial HDTV transmission systems 10 References 11 See also 12 External links

Notation

In the context of HDTV, the formats of the broadcasts are referred to using a notation describing:

• The number of lines in the vertical display resolution.
• Whether progressive frames (p) or interlaced fields (i) are used.
• The number of frames or fields per second.

For example, the format 720p60 is 1280 × 720 pixels, progressive encoding with 60 frames per second (60 hertz known as Hz). The format 1080i50 is 1920 × 1080 pixels, interlaced encoding with 50 fields (25 frames) per second. Often the frame or field rate is left out, indicating only the resolution and type of the frames or fields. Sometimes the rate is then to be inferred from the context, in which case it can usually be assumed to be either 50 or 60, except for 1080p which is often used to denote either 1080p24, 1080p25 or 1080p30.

A frame or field rate can also be specified without a resolution. For example 24p means 24 progressive frames per second and 50i means 25 interlaced frames per second, consisting of 50 interlaced fields per second.

Most HDTV systems support some standard resolutions and frame or field rates. The most common are noted below.

Changes in notation

It should be noted that the terminology described above was invented for digital systems in the 1990s. Before that, analog TV had no true "pixels" to measure horizontal resolution, and vertical scan-line count included off-screen scan lines with no picture information while the CRT beam returned to the top of the screen to begin another field. Thus NTSC was considered to have "525 lines" even though only 480 of them had a picture (625/576 for PAL). Similarly the Japanese MUSE system was called "1125 line", but is only 1035i by today's measuring standards. This change was made because digital systems have no need of blank retrace lines unless the signal was converted to analog to drive a CRT.

Standard resolutions

Note: This diagram lists only a few common video resolutions based on specification. For real life video resolutions, subject to interlace artifacts, please view the diagram at the end of this article or the display resolution article.

• NTSC is 720 x 480 non-square pixels
• PAL is 720 x 576 non-square pixels (Note that the PAL resolution given in the image above is for square pixels.)

NTSC uses pixels that are narrower than square (0.912), PAL uses pixels that are wider than square (1.094). This is referred to as the CCIR 601 standard for digital video.

Standard frame or field rates

• 23.976p (allow easy conversion to NTSC)
• 24p (cinematic film)
• 25p
• 30p
• 50p
• 60p
• 50i (PAL/SECAM)
• 60i (NTSC)

Comparison to SDTV

HDTV has at least twice the resolution of SDTV, thus allowing much more detail to be shown compared to analog television or regular DVD. In addition, the technical standards for broadcasting HDTV are also able to handle 16:9 aspect ratio pictures without using letterboxing, thus further increasing the effective resolution for such content.

Close-up view

HDTV at four times the resolution of SDTV.

SDTV resolution.

Format considerations

The optimum format for a broadcast depends on the type of media used for the recording and the characteristics of the content. The field and frame rate should match the source, as should the resolution. On the other hand, a very high resolution source may require more bandwidth than is available in order to be transmitted without loss of fidelity. The lossy compression that is used in all digital HDTV storage/transmission systems will then cause the received picture to appear distorted when compared to the uncompressed source.

Photographic film destined for the theater typically has a high resolution and is photographed at 24 frame/s. Depending on the available bandwidth and the amount of detail and movement in the picture, the optimum format for video transfer is thus either 720p24 or 1080p24. When shown on television in countries using PAL, film must be converted to 25 frames per second by speeding it up by 4.1%. In countries using the NTSC standard, (60 fps) a technique called 3:2 pulldown is used. One film frame is held for three video fields, (1/20 of a second) and then the next is held for two video fields (1/30 of a second) and then the process repeats, thus achieving the correct film rate with two film frames shown in 1/12 of a second. (See also: Telecine)

Older (pre-HDTV) recordings on video tape such as Betacam SP are often either in the form 480i60 or 576i50. These may be upconverted to a higher resolution format (720i), but removing the interlace to match the common 720p format may distort the picture or require filtering which actually reduces the resolution of the final output. (See also: Deinterlacing)

Non-cinematic HDTV video recordings are recorded in either 720p or 1080i format. The format depends on the broadcast company if destined for television broadcast; however, in other scenarios the format choice will vary depending on a variety of factors. In general, 720p is more appropriate for fast action as it uses progressive fields, as opposed to 1080i which uses interlaced fields and thus can have a degradation of image quality with fast motion. In addition, 720p is used more often with Internet distribution of HD video, as all computer monitors are progressive, and most graphics cards do a poor job of de-interlacing video in real time. 720p Video also has lower storage and decoding requirements than 1080i or 1080p, and few people possess displays capable of displaying the 1920x1080 resolution without scaling. 720p appears at full resolution on a common 1280x1024 LCD, which can be found for under $250. An LCD capable of native 1080p resolution costs close to a thousand dollars.

In North America, Fox, ABC, and ESPN (ABC and ESPN are both owned by Disney) currently broadcast 720p content. NBC, Universal HD (both owned by General Electric), CBS, HBO-HD, INHD, HDNet and TNT currently broadcast 1080i content.

Technical details

MPEG-2 is most commonly used as the compression codec for digital HDTV broadcasts. Although MPEG-2 supports up to 4:2:2 YCbCr chroma subsampling and 10-bit quantization, HD broadcasts use 4:2:0 and 8-bit quantization to save bandwidth. Some broadcasters also plan to use MPEG-4 AVC. Some German broadcasters already use MPEG-4 together with DVB-S2 (ProSieben, Sat1 and Three Premiere Channels). Although MPEG-2 is more widely used at present, it seems likely that in the future all European HDTV may be MPEG-4, and Ireland and Norway, which have not yet started any Digital Television, are considering MPEG4 for SD Digital as well as HDTV on terrestrial broadcasts.

HDTV is capable of "theater-quality" audio because it uses the Dolby Digital (AC-3) format to support "5.1" surround sound.

The pixel aspect ratio of native HD signals is a "square" 1.0, or 1 pixel length = 1 pixel width. New HD compression and recording formats such as HDV use rectangular pixels for more efficient compression and to open HDTV acquisition for the consumer market.

For more technical details see the articles on HDV, ATSC, DVB, and ISDB, respectively.

Within television studios and other production and distribution facilities, HD-SDI SMPTE 292M interconnect standard (a nominally 1.485 Gbit/s, 75-ohm serial digital interface) is used to route uncompressed HDTV signals. The native bitrate of HDTV formats cannot be supported by 6-8MHz standard-definition television channels for over-the-air broadcast and consumer distribution media, hence the widespread use of compression in consumer applications. SMPTE 292M interconnects are generally unavailable in consumer equipment, partially due to the expense involved in supporting this format, and partially because consumer electronics manufacturers are required (typically by licensing agreements) to provide encrypted digital outputs on consumer video equipment, for fear that this would aggravate the issue of video piracy.

Newer dual-link HD-SDI signals are needed for the latest 4:4:4 camera systems (Sony HDC-F950 & Thomson Viper), where one link/coax cable contains the 4:2:2 YCbCr info and the other link/coax cable contains the additional 0:2:2 CbCr information.

Advantages of HDTV expressed in non-engineering terms

1. All commercial HD is digital, so the signal will either deliver an excellent picture, a picture with noticeable pixelation, a series of still pictures, or no picture at all. You would never get a snowy or washed out image from a weak signal, effects from signal interference, such as herringbone patterns, or vertical rolling.
2. Most HD programming and films will be presented in the 16:9 proportioned, semi-widescreen format (though some films created in even wider ratios will still display "letterbox" bars on the top and bottom of even 16:9 sets.) Older films and programming that retain their 4:3 ratio display will be presented in a version of letterbox commonly called "pillar box", displaying bars on the right and left of 16:9 sets (rendering the term "fullscreen" a misnomer). Or, one can usually choose to enlarge the image to fill the screen, however this option will display a distorted, stretched-out picture or one where the top and bottom have been clipped.
3. The colors will generally look more realistic, due to their greater bandwidth.
4. The visual information is about 2-5 times more detailed overall. The gaps between scanning lines are smaller or invisible. Legacy TV content that was shot and preserved on 35 mm film can now be viewed at nearly the same resolution as that at which it was originally photographed.
5. Two new pre-recorded disc formats support HDTV resolutions, namely HD DVD (supporting 720p and 1080i; future players will support 1080p) and Blu-ray (supporting up to 1080p). Players for both systems are expected to be backward-compatible with DVDs. However, the two formats are not compatible with each other.
6. The increased clarity and detail make larger screen sizes more comfortable and pleasing to watch.
7. Dolby Digital 5.1 sound is broadcast along with standard HDTV video signals, allowing full surround sound capabilities. (Standard broadcast television signals include basic stereo audio.)
8. Both designs make more efficient use of electricity than SDTV designs of equivalent size, which can mean lower operating costs.

Early systems

Main article: Analog high-definition television systems

The British 405-line black-and-white system, introduced in 1936, was the first to advertise itself as "high definition," although it was high definition only in comparison with previous mechanical and electronic television systems, and not in the sense of the term as it is used today. On the other hand, the 819-line French black-and-white television system introduced after World War II arguably was high definition in the modern sense, as it had a line count and theoretical maximum resolution considerably higher than those of the 625-line systems introduced across most of postwar Europe, and the later European 625-line color systems (PAL and SECAM).

Japan was the only country where commercial analog HDTV was launched and had some success. In other places, such as Europe, analog (HD-MAC) HDTV failed. Finally, although the United States experimented with analog HDTV (there were about 10 proposed formats), it soon moved towards a digital approach.

Contemporary systems

Asia

Hong Kong

Due to the city's cramped living conditions, flat panel widescreen TV monitors are very popular in Hong Kong. Many people enjoy widescreen DVD movies on their TVs despite the lack of HD broadcasts. While the local authorities have flagged end-2006 as the deadline for a decision to be made on which HDTV standard Hong Kong will adopt, there are political and business considerations. The mainland Chinese government will likely want to be able to jam TV signals from Hong Kong, so that Chinese citizens near the border cannot receive uncensored content from Hong Kong. Currently, analog TV signals from Hong Kong are delayed a few seconds before being relayed inland, such that content on banned topics such as Falun Gong and the Tiananmen Square Protests of 1989 can be blocked. By the same token, Hong Kong broadcasters are keen to use whichever standard China adopts, since doing so would allow them to transmit into the lucrative Southern China market and would lessen the need for costly format conversion.

Japan

Japan had pioneered HDTV for decades with an analog implementation. The old system is not compatible with the new digital standards. Japan terrestrial broadcast of HD via ISDB-T started in December 2003. It is reported that two million HD receivers have been sold in Japan already.

Republic of Korea

After a long controversy between the government and broadcasters, ATSC was chosen over DVB-T. From 2005, digital services are available across the entire country.

At least 10 hours of HD content are required to be broadcast on a weekly basis during the first year of commercial digital service.

Singapore

On Wednesday, May 31, 2006, Singapore kicked off the HDTV trials officially. Two Singaporean broadcasters were involved, Mediacorp (broadcasting HD in DVB-T) and Starhub CableVision (DVB-C). Both broadcast in 1080i, but at 50 Hz, inline with the traditional PAL frequency Singapore uses. Triallists were selected from applicants who had applied prior to May 31, 2006, and there are a total of 1,000 participants on the trial. These trials will end at the end of the year. Presumably then or before that, Starhub and Mediacorp will open it up to all subscribers to receive HD.

Australia

Main article: High definition television in Australia

Australia started HD broadcasting in January 2001, but only in August 2003 was HD content mandated. Most cities in Australia that have a population of 40,000 or greater have at least one terrestrial DTV channel available (for example, Albany, Western Australia, has had DTV available since May 2005). However, most Australian DTV broadcasters are still experimenting with HDTV transmission and DTV delivery. A HD capable set top box is required to view HDTV. 7 HD and SBS broadcasts in 576p, ABC in 720p and Nine, Ten broadcast in 1080i.

Europe

Main article: High-definition television in Europe

North America

Canada

In Canada, on November 22, 2003, CBC had their first broadcast in HD, in the form of the Heritage Classic outdoor NHL game between the Edmonton Oilers and the Montreal Canadiens. Bell ExpressVu, a Canadian satellite company, Rogers Cable and Videotron provide somewhat more than 21 HDTV channels to their subscribers including TSN HD, SportsNet HD, Discovery HD (Canadian Edition), The Movie Network HD, and several U.S. stations plus some PBS feeds and a couple of pay-TV movie channels. CTV Toronto broadcast in HD along with its western counterpart, BC CTV. They were also the first to broadcast a terrestrial HD digital ATSC signal in Canada. Global joined the crowd in late 2004. Other networks are continuing to announce availability of HD signals. CHUM Limited's Citytv in Toronto was the first HDTV broadcaster in Canada; however, now most cable and satellite subscribers across Canada can access multiple channels in HDTV with major American and Canadian affiliate stations broadcasting HDTV signals with no CANCON overlay for advertising. Typically these channels are NBC HD, ABC HD, CBS HD, FOX HD, TSN HD, Sportsnet HD, CBC HD etc. as of Summer 2006. CBC HD officially launched their HDTV programming on March 5, 2005. CBC HD broadcasts the first game of their Hockey Night In Canada Saturday double header in HDTV. The 2006 NHL Playoff games have seen an increased amount of HDTV coverage as well. StarChoice, another Canadian satellite provider, currently offers its subscribers 14 HDTV channels at no extra cost. Shaw Cable has found limited success with HDTV implementation since the cost of a HD PVR is near the $650 CAD mark. Monthly rentals for this equipment have helped HDTV adoption rates.

Mexico

Mexican television company Televisa made experimental HDTV broadcasts in the early-1990s, in collaboration with Japan's NHK. Some events now broadcast in high definition.

During the first half of 2005, at least one cable provider in Mexico City (Cablevision) has begun to offer 5 HDTV channels to subscribers purchasing a digital video recorder (DVR).

In 2005, TV Azteca signed a deal with Harris Corporation's broadcast communications division for digital TV transmitters and HDTV encoding equipment to bring high-definition TV to nine Mexican cities.

The launch will be carried out in two phases. By the third quarter of 2006, HDTV transmissions will be available in Mexico's largest markets: Mexico City, Guadalajara and Monterrey. Phase Two of the national rollout will bring HDTV services to six cities along the Mexico-U.S. border (Matamoros, Reynosa, Nuevo Laredo, Ciudad Juarez, Mexicali and Tijuana) through the first half of 2006. This rollout takes advantage of HDTV receivers already in place thanks to an earlier HDTV rollout by stations on the American side of the border.

Also, TV Azteca has planned to broadcast the Mexican football tournament in HDTV. And almost all retailers have started shipping televisions with HDTV tuners.

XETV in Tijuana, Baja California - across the border from San Diego, California - is on the air in HDTV using 720p format. This affiliate of the American Fox TV Network is on UHF channel 23 broadcasting from Mt. San Antonio in Tijuana, Mexico with 403,000 watts, directed primarily northward at San Diego. In January 2006, Televisa's XEFB-TV and Multimedios' XHAW-TV in Monterrey, Nuevo Leon began HDTV transmissions on UHF channels 48 and 50, respectively. In February 2006, Televisa's XHUAA in Tijuana began its HDTV transmissions on channel 20. Unfortunately they have no HDTV programs. Channel 20 broadcasts an upconverted version of the programs of XHUAA's analog signal on channel 57. In Guadalajara, Televisa channels 2 (XHGA HD),4 (XHG HD) and 9 (XEWO HD) are available in 1080i format, TV Azteca channels 31 and 33 broadcast in 480i format.

Guatemala

The broadcast started on 2006 World Cup on ATSC standard and channel 3 and 7, on HD on 17 & 19

United States

Main article: High-definition television in the United States

In the United States, HDTV specifications are defined by the ATSC. An HDTV-compatible TV usually uses a 16:9 aspect ratio display with an integrated ATSC tuner. Lower-resolution sources like regular DVDs may be upscaled to the native resolution of the TV. It is estimated that by the end of 2006, 10% of American TVs will be HDTVs, but in the same survey, 83% of Americans are not satisfied with the HDTV they are getting. The FCC has mandated that all broadcast must be in digital starting on February 17, 2009. The original deadline of January 1, 2006 was abolished when it was realized that TV stations and customers would not be able to meet the earlier deadline.

South America

Argentina

While HDTV-ready TVs sales are increasing in this country, no single HD feed is available right now. The government is still deciding which format will be used, but chances are American's ATSC will be chosen. DirecTV and local cable company "Cablevision" may also offer HDTV decoders and channel pack later this year.

Brazil

Since 2001 native 480p TVs have been sold in Brazil mainly for DVD video support. In 2003 the first 1080i models were introduced (capable of rescaling 720p) and native 720p LCD monitors in 2004 reached the market.

The Brazilian government took a while to ponder which standard to choose, but on June 29th 2006, President Luis Inácio Lula da Silva signed a decree choosing ISDB as a national standard, based on several criteria, such as better technical quality, robustness, and even a US$2 billion investment on construction of a semiconductor factory in the country financed by NEC, Sony, Panasonic and Toshiba (which would allow for the TV sets and decoders to be locally built).

The transition to ISDB will take 9 years, the manufacturers will adopt the new standard for the new TVs and will also make converters available so the people can continue using their ISDB-incompatible TV's with the new transmission system.

The Japanese government is studying the implementation of some improvements on the standard as suggested by Brazilian researchers. These new features are very unlikely to be adopted in Japan due to incompatibility problems, but are being considered for use in future implementations in other countries, including Brazil itself.^[2]

Uruguay

While HDTV-ready TV sets are available at the country, a few factors seem to constrain the development of the new technology in the near term:

• Prices for LCD, Plasma and DLP-based TV sets can be two times more expensive in Uruguay than in the region, or four times more expensive than in the US, while wages are also lower than in the region. Some DLP-based displays can cost up to US$7000 in Uruguay. There have been few examples, if any, of CRT-based HDTV sets. Taxes seem to play a huge factor in the high prices.
• The cable industry has, then, few incentives to provide other services beyond basic TV services: Internet-by-cable and cable telephony have been either strictly prohibited by law or thwarted by high taxes on equipment that make a business case for newer technologies unfeasible. Digital Cable has started rolling out, with an initial 100% increase of monthly cost for the SD digital service. High prices for HDTV sets do not help. Some of the cable companies for the largest markets are also owned by the largest local TV content providers, which as of 2006 have not started broadcasting any HDTV content.
• DirecTV might be in a better position to provide HDTV content, given that they have experience and content from the US and given that they serve the whole continent. But DirecTV's policy in Uruguay has been that of providing "leftover" equipment from Argentina to its customers in Uruguay (i.e., first-generation RCA receivers), which as of now do not support HDTV content or Dolby AC-3 Sound. Uruguayan DirecTV customers have no way of buying an alternative DirecTV set, other than that provided by DirecTV.
• Uruguay hoped for neighboring countries reaching an agreement on an HDTV standard, but so far that does not seem to be the case. Brazil has adopted the ISDB system, while Argentina and Uruguay have historically used TV systems based on a European standard (PAL-N 625/50Hz). Now Argentina seems to be settling on the ATSC standard, and Uruguayan URSEC authorities have provided no information on which road they will go. The TV sets being sold in Uruguay seem to be closer to ATSC HDTV-based standards (60Hz systems). If a 50 Hz standard is adopted, consumers who bought 60Hz might get hurt if there is a lack of compatibility with the sets being sold. Most of the DVD-based content in the country is NTSC/60Hz-based, while the TV standard in use is PAL/50Hz-based. Most of the analog TV sets sold are PAL-N, PAL-M and NTSC capable, while most DVD players are multiregion. Authorities are not asking retailers to identify which standard the HDTV sets sold adhere to, nor have they required retailers to warn consumers that Uruguay has not yet settled on a a given HDTV standard. Most tech-savvy consumers feel uneasy about buying for themselves or recommending to friends such high-priced TV sets while so much doubt surrounds HDTV standards in the country.

Recording and compression

Main article: High-definition pre-recorded media and compression

HDTV can be recorded to D-VHS (Digital-VHS), W-VHS (analog MUSE only), to an HDTV-capable digital video recorder such as DirecTV's high-definition TiVo or Dish Network's DVR 921, 942 or VIP622, or to a computer equipped with an HDTV capture card. In the U.S., the only current archival option is D-VHS. D-VHS digitally records a 28.2-Mbit stream onto a classic VHS tape, using a FireWire (IEEE 1394) digital transport to carry a compressed MPEG-2 Transport Stream from the tuning device to the recorder.

However, the massive amount of data storage required to archive uncompressed streams make it unlikely that an uncompressed storage option will appear in the consumer market soon. Realtime MPEG-2 compression of an uncompressed digital HDTV signal is also 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.

As part of the FCC's "plug and play" agreement, cable companies are required to provide customers that 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, boxes are not included in the FCC mandate. This content is protected by encryption known as 5C. ^[3]. This encryption can prevent someone from recording content at all or simply limit the number of copies.

Table of terrestrial HDTV transmission systems

Main characteristics of three DTTV systems

Systems	ATSC	DVB-T	ISDB-T
Source coding
Video	Main Profile syntax of ISO/IEC 13818-2 (MPEG-2 – Video)
Audio	ATSC Standard A/52 (Dolby AC-3)	ISO/IEC 13818-2 (MPEG-2 – Layer II Audio) and Dolby AC-3	ISO/IEC 13818-7 (MPEG-2 – AAC Audio)
Transmission system
Channel coding
Outer coding	R-S (207, 187, t = 10)	R-S (204, 188, t = 8)
Outer interleaver	52 R-S block	12 R-S block
Inner coding	rate 2/3 Trellis code	PCC: rate 1/2, 2/3, 3/4, 5/6, 7/8; constraint length = 7, Polynomials (octal) = 171, 133
Inner interleaver	12 to 1 Trellis code	bit-wise, frequency	bit-wise, frequency, selectable time
Data randomization	16-bit PRBS
Modulation	8-VSB and 16-VSB	COFDM QPSK, 16QAM and 64QAM Hierarchical modulation: multi-resolution constellation (16QAM and 64QAM) Guard interval: 1/32, 1/16, 1/8 & 1/4 of OFDM symbol Two modes: 2k and 8k FFT	BST-COFDM with 13 frequency segments DQPSK, QPSK, 16QAM and 64QAM Hierarchical modulation: choice of three different modulations on each segment Guard interval: 1/32, 1/16, 1/8 & 1/4 of OFDM symbol Three modes: 2k, 4k and 8k FFT

References

See also

• Advanced Television Systems Committee (ATSC)
• ATSC tuner
• Integrated Services Digital Broadcasting
• DVB (Digital Video Broadcasting)
• Digital television
• HDTV input and colorspace (YPbPr/YCbCr).
• HD ready
• SDTV (Standard Definition Television)
• Ultra-High Definition Video (UHDV)
• Middleware High Definition support: OpenTV HD
• Arun Netravali

External links

• High definition PAL NTSC SECAM FAQ High definition PAL-SECAM-NTSC FAQ
• DTV government Resource US Government HDTV and DTV official site
• HDTVExpert.co.uk UK based consumer guide to HDTV in Great Britain
• HDTV Magazine High Definition News, Articles, Programming, Forum, etc.
• HDTV Information Consumer information about HDTV
• ATSC
• CDTV Canadian Digital Television official website
• High Definition Forum
• Linowsat List of european HDTV channels DVB-S und DVB-S2 with videobitrates
• [1]HDTV (H.264 AVC DVB-T) Trial in Singapore
• [2]Blog on HDTV developments

Digital video resolutions

Designation	Usage examples	Definition (lines)	Rate (Hz)
			Interlaced (fields)	Progressive (frames)
Low; MP@LL	LDTV, VCD	240; 288 (SIF)		24, 30; 25
Standard; MP@ML	SDTV, SVCD, DVD, DV	480 (NTSC, PAL-M);	60;	24, 30;
		576 (PAL, SECAM)	50	25
Enhanced	EDTV	480; 576		60; 50
High; MP@HL	HDTV, HD DVD, BD, HDV	720		24, 25, 30, 50, 60
		1080	50, 60	24, 25, 30
This table illustrates total horizontal and vertical detail via box size. It does not accurately reflect the screen shape (aspect ratio) of these formats, which is always stretched or squeezed to 4:3 or 16:9. The table assumes an average vertical detail loss of .75x due to interlace. The actual loss is variable due to content, motion, opinion on acceptable levels of flicker, and possible success of deinterlacing. 1920 × 1080i is not included because all common use of 1080i is filtered to 1440 or less.