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High-definition television (HDTV) means broadcast of television signals with a higher resolution than traditional formats (NTSC, SECAM, PAL) allow. Except for an early analog format in Japan, HDTV is broadcast digitally, and therefore its introduction sometimes coincides with the introduction of digital television (DTV).
Historically, high-density television referred to television standards developed in the 1930s to replace the early experimental systems.
Technical details
An HDTV-compatible TV usually 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 currently used as the compression codec. Like NTSC and PAL, 1920 × 1080 broadcasts generally use interlacing to reduce bandwidth demands. Alternating scan lines are broadcast 50 or 60 times a second, similar to PAL's 50 Hz and 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 720p60 content. A mix of interlaced and progressive scan is also encountered, where the 1080i60 (or 50) signal can be deinterlaced by simple weaving of fields to frames, giving in effect a 1080p30 (or 25) image.
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Visual comparison of common TV display resolutions.
For more technical details see the articles on ATSC, DVB and ISDB respectively.
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, developed by NHK Science and Technical Research Laboratories (STRL) in the 1980s, 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 based on ISDB.
Europe
The EEC (later, the EU) established a European standard for uncompressed digital 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 SES Astra allowed broadcaster to avoid using MAC at all. It was much 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 is 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 to 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 (http://www.agcom.it/eng/92_38_EEC.htm), 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 2010–2015 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 under the All Channels Act 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 (the technical term for CableCARD is point-of-deployment module, or POD, which refers to plug-in access cards compliant with ANSI/SCTE 28). CableCARD is a feature of "Digital Cable Ready" and will enable cable TV customers to access protected content by receiving an access card from their cable company much like a PCCard (formerly known as PCMCIA) 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. Current CableCARD products only support unidirectional communication with the cable network, which means that interactive services such as video on demand and pay-per-view are not available. This also means that the cable operator's interactive program guide that most digital cable customers receive will not be available. Television manufacturers may provide an alternate program guide. Most cable operators, in most cable systems, were required by US Federal regulation to support CableCARD products beginning July 1st 2004 (see, e.g., FCC 03-225 (http://hraunfoss.fcc.gov/edocs_public/attachmatch/FCC-03-225A1.pdf)). Most major television manufacturers have announced plans for producing CableCARD products, many of which are now available (November 2004). Negotiations for a bidirectional agreement (which would include access to video-on-demand and other interactive services) is currently underway.
Satellite television companies in the USA, such as DISH Network and DirecTV, started to carry HD programming in 2002. Some cable television companies, such as Comcast, started to do the same in 2003. As of September 2004, HD programming is carried by all major television networks in at least some broadcast markets, including ABC, CBS, NBC, FOX, 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 satellite company called VOOM is currently the largest HD provider offering upwards of 40 high-definition channels.
The latest addition is the broadcast flag rule, which is an FCC mandate that requires that high-definition television sets include copy prevention equipment that disables the unauthorized high-definition recording of broadcasts that the provider has flagged with a special signal, the broadcast flag. The mandate has been highly controversial, with consumer and civil liberties advocates arguing that it strips consumers of rights they have enjoyed in the past.
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. Citytv's CITY TV in Toronto was the first HDTV broadcaster in Canada.
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.
In January 2005, EICTA announced plans for an "HD ready" label for equipment that meets certain requirements, including supporting 720p and 1080i at 50 and 60Hz. Displays must include YUV and DVI or HDMI interfaces and have a native vertical resolution of 720 lines or more.
European Union
The European Commission analysed 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 (http://europa.eu.int/information_society/topics/ecomm/shortcuts/digital_broadcasting/wide_screen_high_def/index_en.htm) 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 chance 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 commissions 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 TF1 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 Numérique 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. The BBC is believed to favour 720p because of its progressive scan technology.
There are no plans for HDTV versions of the Freeview and Top Up TV digital terrestrial television services.
Sky's pay platform plans to launch its premium HD services on satellite in 2006. It will be limited to some channels and special events. Recent reports suggest that headline sporting events will be made available in HD to pubs before the launch of the domestic HD service.
It is almost certain that cable providers will upgrade to HD as and when channels become available.
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 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. 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.
Mexico
Mexican television company Televisa started making experimental HDTV broadcasts in early 1990's, in collaboration with Japan's NHK. Some events have already been broadcasted, but HDTV use is very limited.
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 (http://www.dtcp.com/). 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 (http://www.manifest-tech.com/media_dvd/hd_dvd.htm)
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 Pictures 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
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