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High definition television

(Redirected from High Definition TV)

High Definition Television (HDTV) means broadcast of television signals with a higher resolution than traditional formats (NTSC, SECAM, PAL) allow. Its introduction coincides with that of digital television (DTV).

Contents

Technical details (U.S.)

The HDTV screen uses a 16:9 aspect ratio. The high resolution images (1920 pixels × 1080 lines or 1280 pixels × 720 lines) allow much more detail to be shown compared to analog television or regular DVDs. MPEG-2 is used as the compression codec. The images are expected to be at least 6 times as sharp as standard definition television or analog television. Like NTSC and PAL, most 1920 × 1080 broadcasts use interlacing to reduce bandwidth demands. Alternating scan lines are broadcast 60 times a second, similar to NTSC's 60 Hz interlacing. This format is entitled 1080i, or 1080i60. In areas traditionally using PAL 50 Hz (1080i50) is also used. Progressive scan formats are also used with frame rates up to 60 per second. The 1280 × 720 format in practice is always progressive scan (with the entire frame refreshed each time) and is thus termed 720p. Several US broadcasters currently broadcast 720p/60 content.

The US digital television system also allows lower, non HD resolutions to be encoded, such as Enhanced Digital Television (EDTV), which is a standard size of 720 × 480 (PAL: 720 × 576) TV picture, only in progressive format, allowing 60 (PAL: 50) full frames per second. Also included is a system for broadcasting Standard Definition Television (SDTV) with the interlacing.

Dolby Digital AC-3 is used as the audio codec, allowing the transport of up to 5 channels of sound with a 6th channel for low frequency effects (the so-called "5.1" configuration). Japanese HDTV broadcasts use MPEG's Advanced Audio Coding (AAC) as the audio codec, which also allows 5.1 audio output. DVB allows both.

Digital HDTV transmission is designed to occupy the same 6 MHz terrestrial band now used in the US for analog NTSC broadcasts. A single NTSC 6 MHz channel can carry 19.2 Mbit/s of information using ATSC's standard 8-VSB (8-level Vestigial Side Band) modulation method. This is sufficient to carry up to 6 standard definition TV channels, or a single HDTV channel. As a side note, the standard for HD signal transmission over digital cable television systems in the US is now fixed as QAM 256 (Quadrature Amplitude Modulation), which is technically part of the DVB standard (but not ATSC) and is a de facto cable industry standard. This method has higher bandwidth than 8-VSB, allowing two 19.2 Mbit/s channels in a 6 MHz bandwidth, due to its lower tolerance for errors which are generally less of a concern in a wired environment. The ATSC standards included a provision for 16-VSB transmission over cable at 38.4 Mbit/s, but the encoding never gained wide acceptance.

Due to technical reasons having to do with the video equipment, recording technologies, and the 19.2 Mbit/s-limited ATSC channel, some HDTV signals will not reach their nominal resolution. Most notably, 1080i60 is impossible to broadcast without artifacts at this bandwidth using ATSC. Most 1080i broadcast signals actually are filtered to 1440 horizontal samples to allow adequate compression, and most current consumer HDTVs based on CRTs cannot resolve even 1440 horizontal samples (most rear-projection CRTs will resolve 1200-1300 at best, unless based on 9" guns). Despite this, HDTV viewed even on existing sets is still far superior to PAL or NTSC in resolution, and future sets are likely to offer superior resolution at the same or lower prices.

History outside the US

It has been technically possible to create higher-resolution televisions for many years—for instance, computer monitors have been able to display high-resolution images with superior color and refresh rates since the 1980s. Theoretically, one need only spend the money to scale up the relatively feeble light output of computer monitors to that of a consumer TV and one has the physical basis for an HDTV.

Japan

Japan had the earliest working HDTV system, with design efforts going back to 1979. Japan began broadcasting analog HDTV signals in the early 1990s using an interlaced resolution of 1035 lines (1035i). The Japanese MUSE system employed filtering tricks to reduce the original source signal to decrease bandwidth utilization. For example, three successive picture elements on a line were actually derived from three separate scans. Whole camera pans would result in a loss of 50% of horizontal resolution. Japan has since switched to a digital HDTV system.

Europe, HD-MAC, DVB

The EEC (later, the EU) established a European standard for HDTV in a 1986 directive (MAC). The standard didn't prove to be popular among broadcasters. It was required that all high powered satellite broadcasters used MAC from that year. However, the advance of technology and the launch of middle powered satellite provider Astra allowed broadcaster to avoid using MAC at all. It was used in transcontinental satellite transmissions, though.

Another reason for HD-MAC's failure was that it was not realistic to use 36 MHz for a high definition signal in terrestrial broadcasting (SDTV uses 6, 7 (VHF) or 8 MHz (UHF) ). That way, HD-MAC could only be used by cable and satellite providers, where there was a wider bandwidth. Thus, HDTV could not replace conventional analog television (terrestrial) PAL/SECAM , making HD-MAC sets unattractive to potential consumers.

The HD-MAC standard was abandoned in 1993, and since then all EU and EBU efforts have focused on the DVB system (Digital Video Broadcasting), which allows both SDTV and HDTV.

One must notice that, although HDTV is still possible with DVB-T, most EU countries are taking the "more channels on a single multiplex" approach, rather than the "one single channel in HDTV" followed in the USA, Canada, Japan and Australia. Some European governments aim to switch to digital in order free the VHF spectrum for other uses. HDTV is thus left to satellite (DVB-S) and cable (DVB-C) distribution for the moment.

A single HDTV channel would take up to four SDTV channels from any of the 3 to 8 multiplexes, so HDTV doesn't seem suitable for terrestrial broadcasting in Europe. Also, many broadcasters and producers assume that the average European consumer does not demand HDTV at the moment, nor will he benefit from HDTV with current TV sets.

See also: COUNCIL DIRECTIVE 92/38/EEC of 11 May 1992, HD-MAC.

Adoption

United States

One of the current reasons for the US government's push for digital transmission is the desire to auction off part of the UHF spectrum, channels #52 through #69, for other two way and one way fixed and mobile services. This could include digital mobile TV broadcasting. Additionally, in the 1980s there was a fear among many in the US that Japanese advances in HDTV would contribute to the further erosion of US leadership in electronics and other high-tech industries, not to mention the defense industry implications of having a high resolution television system. The Federal Communications Commission (FCC) began soliciting proposals for a new television standard for the US 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. HDTV sets became available in the US in 1998 and broadcasts began around November 1998.

Because HDTV requires more broadcast spectrum for the transition period, it has been the topic of great political controversy in the United States. Stations currently receive a free channel, generally in the UHF range, over which they are to broadcast their digital signal, while still providing analog service. According to FCC rules, all television broadcasting in the United States by current full power broadcasters on channels 2-51 will by the beginning of 2007 be digital, with an escape clause that 85% of the serviced area must be "capable" of receiving digital signals. At the time of analog shutoff, one channel would then be returned to the government for transfer to the new private owner, while the other would have only the digital signal. Current analog TV sets would still work with cable or satellite service or with a converter box that would convert digital OTA signals to analog. As of January 2004, indications from industry and FCC officials including its chairman are that the cutoff date for digital-only broadcasts will not meet the intended 2007 and the actual timeline for analog shutoff in the US will realistically be in the 20102015 timeframe.

Of importance is that the FCC has not mandated HDTV signals; it has only mandated that digital TV signals be broadcast. The prevailing expectation, however, is that HDTV during primetime will be the rule. It is not clear whether broadcasting HDTV or multiple standard definition channels during non primetime hours will become common.

As of February 2004, most HDTV sets in the US had the capability to display HDTV signals but not to decode the broadcast. Generally only the more expensive TVs will have an 8-VSB (and often QAM) tuner built-in. Because a large percentage of people in the US receive their television through cable or satellite (particularly those who have the money to spend on an HDTV), and because different cable and satellite systems use different encoding standards, most HDTVs only include analog NTSC tuners. This allows the user to purchase or rent a separate tuner to receive HDTV signals. An ATSC receiver for over-the-air broadcasting can currently be purchased for around $350 in the US, although this is expected to drop sharply as demand increases. Alternately, in the US one can purchase a satellite tuner to receive satellite HDTV signals, or rent a cable HD tuner to receive cable HDTV signals. The situation is similar to UHF tuners, which initially were an aftermarket accessory in the early days when NTSC was initially broadcast only in the VHF range.

To expedite the availability of HD reception, the FCC has ruled that 50% of TV sets with screens of at least 36 inches must have 8-VSB/QAM tuners by July 2004, with complete tuner coverage in that size class by July 2005 , while the requirement for smaller sets and digital VCRs would be phased in from 2005 to 2007. It is anticipated that the price of tuner hardware will fall as the market enlarges. It should be noted that the FCC also mandated the inclusion of UHF tuners in all NTSC TVs which eventually lead to their being integrated at no marginal cost.

The transition to HDTV in the US has not yet reached critical mass but there is increasing availability of premium as well as freely available terrestrial broadcast HD content. As equipment for HDTV production becomes cheaper and more widespread, this will only accelerate. For example, the US President's State-of-the-Union speech in January 2004 was broadcast using a mixture of HD and a few SD camera signals, which was the first major US news event to see any significant use of HD. On the equipment side, TVs capable of displaying HDTV signals are available as of July 2004 for approximately $400 USD in the direct view CRT market. Standard resolution CRT TV sets are completely extinct in the larger rear-projection CRT units.

Many of the new HDTV's with integrated digital tuners will include CableCard support. CableCard which has also been named "Digital Cable Ready" will enable cable TV customers to access protected content by receiving a Card from their cable company much like a PCCard for a pc, once this card is installed in the TV the customer will have some of the features of the Cable companies supplied Set Top Box. Unfortunately CableCard only supports One Way communications which means that Video On Demand and Pay Per View will not be available. This also means that the Interactive Program Guide that most Digital Cable Customers are used to will have to be supplied by the TV manufacturer. Cable Companies started supporting CableCard on July 1st 2004 per the FCC "Plug and Play" agreement. Most major manufacturers have announced CableCard products to be released late 2004. A Two Way CableCard standard is currently being developed.

Satellite television companies in the USA, such as Dish Network, started to carry HD programming in 2002. Some cable television companies, such as Comcast, started to do the same in 2003. As of July 2003, HD programming is carried by all major television networks (except Fox which started their first 720p HD broadcast on Sept 12, 2004) including ABC, CBS, NBC, PBS and The WB as well as other cable/satellite channels including Discovery HD Theater , HBO, HDNet , Showtime HDTV and INHD. Cable and satellite providers typically also offer HDTV pay-per-view movies. The production of HDTV programming is very time consuming. According to PBS, it took 1000 hours to produce a three hour program. As of July 2003, PBS only produces about 10 hours of HD programming per month, while ABC provides the most hours of HD programming per day among other non-cable networks. Due to the lack of HD source material, many HD channels only run a few hours of HD programming each day, the rest of the day is filled with regular programs, however, a few HD channels that run HD program 24 hours a day do so by repeating the same set of material over and over again. In September of 2004, the INHD channels ran commercials and claimed that the channels offered more than 100 hours of new HD programming each month.

A cable company called Voom is currently the largest HD provider offering upwards of 40 High Definition channels.

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 has TSN HD and Discovery HD (Canadian Edition). The Canadian Discovery HD Channel has commercials and is currently sponsored by Future Shop. CTV Toronto announced they're going to broadcast HD along with its western counterpart, BC CTV. Other networks are continuing to announce availability of HD signals.

Europe

Many countries show limited interest in HDTV. Most of Europe has instead gone to widescreen EDTV using the DVB standard for now, though satellite delivery of HD started in Europe on January 1, 2004 with the start of Euro1080. Recently this channel was split in two: HD1 (mostly HDTV showcasing for regular users) and HDe (live and recorded HDTV broadcasts of special events for selected theatres). Euro1080 currently broadcasts its channels on the Astra satellite, and a few selected cable operators. Another HD channel is available on the Astra for testing: Astra HD test.

A newer version of DVB-S (DVB-S2), combined with the H.264/AVC codec (a.k.a. MPEG-4 Part 10) might be the key for future HDTV success in Europe.

European Union

The European Commission anaylised the state of 16:9 broadcasting, as well as HDTV in "The contribution of wide-screen and high definition to the global roll-out of digital television staff working paper.

This paper states that previous plans objectives for a europe-wide HDTV introduction by 1999 (HD-MAC in 1992) were not met because market players focused on digital technologies and easier to implement service options. Thus, european consumers never had a change to test HDTV.

It also points out some causes for HDTV's poor performance in the EU:

  • European market players feel that HDTV failed in Europe.
  • Broadcasters prefer to focus in cheaper multi-channel SDTV.
  • A SDTV widescreen resolution is more cost effective than a HDTV equivalent.

Later, the comissions suggests that some coordination in the EU is required in order for HDTV services to be consistently available in all member states.

France

M6 and TVF1 have expressed intention to broadcast some programes in HD in the near future, although they will not be available in the digital terrestrial television service that will start in 2005.

TPS, competitor of Canal Satellite Numerique also intends to begin its HD broadcasting in 2005

Germany

Premiere pay platform will start broadcasting 3 HD channels in November 2005 . These channels will feature different contents (movies, sports and documentaries . Unlike HD1 and HDe , they will use MPEG4 instead of MPEG2.

United Kingdom

The BBC already produces some programs (mostly documentaries) in HD for foreign markets, such as the USA and Japan. The corporation intends to produce all its programes in HD by the year 2010.

There are no plans for a HDTV version of Freeview.

Sky pay platform plans to launch its premium HD services in 2006. It will be limited to some channels and special events.

Japan

Japan had pioneered HDTV for decades with an analog implementation. Their 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 one million HD receivers have been sold in Japan already.

Republic of Korea

After a long controversy between the goverment and broadcasters, ATSC was choosed over DVB-T. In 2005, digital services will be available in all the country.

It is required that at least 10 hours of HD content to be broadcasted on a weekly basis during the first year of commercial digital service.

Australia

Australia started HD broadcasting in January 2002 but only in August 2003 was HD content mandated. Since August sales of DTV receivers in Australia have picked up.

Brazil

Brazilian universities, research and government institutions are discussing the best policies for a Digital television system for use in Brazil.

A complete testbed is expected for 2005.

Recording and prerecorded media

HDTV can be recorded to D-VHS (Digital-VHS) or to an HDTV capable Digital Video Recorder such as DirecTV's high-definition TiVo.

D-VHS recording is done in the US utilizing a digital transport such as Firewire (IEEE 1394) to carry the MPEG-2 Transport Stream from the tuning device to the recorder. Recording the uncompressed HDTV stream will be impractical in the consumer market for many years. 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, though 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 neither widely available nor inexpensive.

As part of the FCC's "Plug and Play" agreement cable companies are to provide customers that rent HD Set Top Boxes with a Set Top Box with "Functional" Firewire (IEEE 1394) upon request. None of the DBS providers have offered this feature on any of their supported Boxes as of July 2004 as they are not included in the FCC mandate. This content is protected by encryption known as 5C. This encryption can prevent someone from recording content at all or simply limit the number of copies.

The only widely available prerecorded HD media, aside from scarce Japanese analog MUSE-encoded laserdiscs, is D-Theater, a format available on D-VHS. D-Theater is an encrypted format and only D-Theater capable D-VHS players can play back these tapes. D-Theater utilizes a 28 Mbit/s MPEG2 stream at 720p or 1080i. This format is superior to broadcast HDTV due to its higher bandwidth and, of course, the ability to do non-realtime optimization of the encoding which is not possible with broadcast HDTV. This format is currently a niche market even in the HDTV US consumer market and its overall future is not certain.

It is possible to record HD media to optical disc using a Sony Blu-ray DVD recorder, currently available only in Japan with a Japanese satellite tuner. This uses a blue-laser optical disc system with MPEG2 as the codec.

In an attempt to provide a bitrate-compatible high-definition format for high-definition video on standard DVDs, Microsoft introduced into their Windows Media 9 Series codec the ability to compress a high-definition bitstream into the same space as a conventional NTSC bitstream (approximately 5 to 9 megabits per second). It remains to be seen if the codec will be adopted for widespread use, if only as a Wi-Fi industry standard. As of November 2003, this format required a significant amount of processing power to encode and decode and the only commercially available movie that used the codec was the Terminator 2: Extreme Edition DVD. Since then, more titles have become available in this format. 1

Other similar codecs are in contention such as AVC and VP6 from ON2. VP6 has been chosen by China for both digital TV and DVD production. This is as a result of China's desire to avoid royalties on WM9 or AVC. As an advantage, VP6 requires only a per-device royalty of $2 and no royalties on recorded media. As China starts to dominate manufacturing of TV and DVD units, the country's choice of standards becomes more central for everyone. VP6 is considered to be a superior codec by many people. It is likely this codec will appear quickly in low-end US players, given their dependence on low-cost Asian chipsets. The low cost of the codec itself is not a significant advantage over DVD, however, as the standalone hardware players will be incompatible with standard DVD-Video unless the manufacturer pays the royalties for the technologies necessary to make the player DVD-compatible. There are currently very few titles in any market available for this format that would drive purchase of incompatible players. It is unlikely any major US studio will commit to movies in this format without some form of copy-protection, which is not yet specified.

Recently, the DVD Forum and the Blu-ray group failed to agree on standards for high definition 12 cm discs. A format war is now very likely between the DVD Forum's HD-DVD (formerly Advanced Optical Disc) standard and Sony's Blu-ray disc standard. To complicate things further, Sony also makes movies via its Columbia-Tristar subsidiary. As a result, this will likely lead to certain films becoming available only on one format. Both sides of the HD disc camp are likely to leverage studio partners against each other through exclusive arrangements. A possible outcome of a messy format war could be the emergence of combo players, as the physical disc sizes are identical, H.264 would be the likely codec for HD-DVD.

There are now some DVD players that will output enhanced or high-definition signals from standard-definition DVDs. These players, however, are not considered to be true HD-DVD players since they only include an integrated scaler to upconvert the standard-definition DVD video to high-definition video. This upconversion process generally can improve the perceived picture quality of standard-definition video.

References

See also

External links


Last updated: 10-24-2004 05:10:45