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High-definition television

(Redirected from HDTV)

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, the term high-definition television was also used to refer to television standards developed in the 1930s to replace the early experimental systems.

Table of contents

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 use interlacing at 50 or 60 fields/sec to reduce bandwidth demands, at 24, 25 and 30 frames/sec progressive scan is used. 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. 1080p, "true high-definition", is currently used for broadcasting with less than 50 field/sec. Progressive scan formats are also used with frame rates up to 60 per second. The 1280 × 720 format only supports progressive scan (with the entire frame refreshed each time) and is thus termed 720p. FOX, ABC, and ESPN currently broadcast 720p60 content.


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

Early Systems

MUSE

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.

MUSE in Operation

  • Typically three successive picture elements on a line were actually derived from three separate scans. Moving images were thus blurred in a manner similar to using 16mm movie film for HDTV projection.
  • Stationary images were transmitted at full resolution.
  • Whole camera pans would result in a loss of 50% of horizontal resolution.
  • Considering the technological limitations of the time, MUSE was a very cleverly designed analog system.
  • MUSE had a bit-reduced stereo audio transmission system that was very unique in its design as it was not phycoacoustical like Musicam.

Japan has since switched to a digital HDTV system based on ISDB.

HD-MAC

The European Commission established a European standard for uncompressed digital HDTV in a 1986 directive (MAC). However, it never became popular among broadcasters. It was required that all high-powered satellite broadcasters used MAC from that year. Owing to the advance of technology and the launch of middle powered satellites by SES Astra, broadcasters could avoid MAC, and lower transmission costs. HD-MAC (the high definition variant of MAC) was left for transcontinental satellite links, 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)). HD-MAC could only be used by cable and satellite providers, where there is a wider bandwidth available. Thus, analogue HDTV could not replace conventional SDTV(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.

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

Contemporary systems

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 extra broadcast spectrum during the transition period, it has become a topic of political controversy in the United States. Current stations have received a free channel, generally in the UHF range, on which to broadcast their digital signal, while still maintaining analog service. According to FCC rules, all full power stations on channels 2–51 must convert to digital by the beginning of 2007, with an escape clause that 85% of receivers in the service area must be "capable" of receiving digital signals. At the time of analog shutoff, one channel would then be returned to the government for sale to a new licensee, with the digital one remaining. Existing analog TV sets would still work with cable or satellite service or use a converter box that would convert digital over-the-air (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.

The FCC has not mandated HDTV signals; it only requires digital TV broadcasts. 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 did not have integrated digital receivers. Generally only the more expensive TVs have an ATSC (for OTA) or QAM (for cable or satellite) tuner built-in. Because about 80% percent of homes in the US receive television through cable or satellite, and because different cable and satellite systems use different encoding standards, most HDTVs only include analog NTSC tuners. This requires the user to purchase or rent a separate tuner to receive HDTV signals. An ATSC tuner for OTA broadcasts costs $200–350 USD (February 2005) locally. Alternately, one can purchase a satellite HD tuner, or rent a cable HD tuner. The situation is similar to early UHF tuners, which were an aftermarket accessory because NTSC was initially broadcast only in the VHF range.

To expedite the availability of HD receivers, 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. The requirement for smaller sets and digital VCRs will be phased in from 2005 to 2007. It should be noted that the FCC previously 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 subscribed as well as freely available OTA 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. It 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 $700 USD in the direct view CRT market. Standard resolution CRT TV sets are now unavailable 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 digital cable customers usually receive is not 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). 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 shortage 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 SD 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.

The FCC also instituted the broadcast flag rule through administrative rulemaking, which required that HDTV sets manufactured in July, 2005 or later include technology which would restrict internet retransmission 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. In May, 2005 however, the US Circuit Court of Appeals for the D.C. Circuit struck down the Broadcast Flag mandate in a unanimous ruling, holding that the FCC overstepped its statutory authority when it asserted control of any device capable of reciving an HDTV signal.

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 and Rogers Cable both provide somewhat more than 13 HDTV channels to their subscribers, typically for a non-trivial fee including TSN HD, Discovery HD (Canadian Edition) and several U.S. stations plus some PBS feeds and a couple of pay-TV movie channels. 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, however very few shows are shown in HDTV beyond the well known ones such as CSI, ER etc. as of early 2005. CBC officially launched HDTV programming on March 5th, 2005.

Europe

(See also Euro1080).

Many countries show limited interest in HDTV for now. EDTV using the DVB is common.

Although HDTV is still possible with DVB-T, most countries are following the "more channels on a single multiplex" approach, rather than the "one single channel in HDTV" more common in the USA, Canada, Japan and Australia. As a single HDTV channel would take up to four SDTV channels from any of the 3 to 8 multiplexes, MPEG2 based HDTV doesn't suit terrestrial broadcasting needs in Europe.

Additionally, some governments want to switch to digital in order to reassign VHF frequencies for other uses.

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 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 programmes in HD in the near future, although they are not available in the digital terrestrial television service that started in 2005.

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

Pay per view terrestrial chanels will use H.264 / MPEG-4 AVC from September 2005, to allow HDTV premium content.

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 programmes (mostly documentaries) in HD for foreign markets, such as the USA and Japan. The Corporation intends to produce all its programmes in HD by the year 2010. The BBC is believed to favour 720p because of its superior resistance to motion artifacts in live action.

There are no plans for HDTV versions of the Freeview and Top Up TV digital terrestrial television services, owing to the fact that there is no spare bandwidth available. This may change after the UK's analog television signals are switched off, but the date of the switchoff is still being hotly debated.

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. Sky has confirmed that both 720p and 1080i will be available for use. Some reports suggest that Sky's system will be capable of transmitting imported US HDTV programming in its native 30 or 60 Hz vertical scan rates, in addition to domestic programming in 25 or 50 Hz.

Recent reports suggest that Sky will make headline sporting events such as soccer matches 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. 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 for almost a year as of May, 2005). However, most Australian DTV broadcasters are still experimenting with HDTV transmission and DTV delivery.

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

The Mexican television company Televisa made experimental HDTV broadcasts in the early 1990s, in collaboration with Japan's NHK. Some events are now broadcast in high definition, but HDTV use is very limited.

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).

Recording and prerecorded media

HDTV can be recorded to D-VHS (Digital-VHS), W-VHS, or to an HDTV capable digital video recorder such as DirecTV's high-definition TiVo or DISH Network's DVR 921 or 942.

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.

Future media

HD programming may be recorded on optical disc using a Blu-ray recorder. This technology is currently available only in Japan with a Japanese satellite tuner, but is expected to be released in other world markets in 2005. Blu-ray uses a blue-laser optical disc with an MPEG2 codec.

In an attempt to provide a bitrate-compatible high-definition format for high-definition video on standard DVD-ROMs, Microsoft introduced their Windows Media 9 Series codec with the ability to compress a high-definition bitstream into the same space as a conventional NTSC bitstream (approximately 5 to 9 megabits per second for 720p and higher). Microsoft is marketing its high-definition Windows Media 9 Series codec as WMVHD. 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 (see 1). Since then, more titles have become available in this format, such as the acclaimed surf documentary Step Into Liquid. As of the start of 2005, Microsoft recomends a 3.0 GHz processor with 512 MB of RAM and a 128 MB video card for 1080p playback on Windows XP. The codec has been submitted to SMPTE and is in SMPTE's standardization process with an intent for it to become an official SMPTE standard known as VC-1 in the near future.

Other codecs are in contention such as AVC (approved by the ITU-T and MPEG standards bodies in early 2003) and the VP6 and now VP7 codecs from On2 Technologies. For further information about AVC (also known as H.264 and as MPEG-4 part 10), see the H.264 page.

VP6 was reported by On2 to have been chosen by China for use in the Enhanced Versatile Disc (EVD) format initiative. This was reportedly as a result of China's desire to avoid royalties on WM9 or AVC. As an advantage, VP6 would not require royalties on recorded media (although royalties would be charged for player devices at a similar cost as for other codecs). As China starts to dominate manufacturing of TV and DVD units, the country's choice of standards becomes more important for everyone. A low cost for 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. Very few titles were made available in any market for this format, although many would presumably be needed to 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. Soon after the announcement that VP6 would be used on EVD, negotiations between On2 and E-World (the consortium pushing EVD to become a standard) broke down. On2 filed multiple breach of contract claims for arbitration, but in March of 2005 the arbitrator ruled that E-World had not broken the contract and owed nothing to On2. It was unclear to On2 and the arbitrator whether the Chinese government ever approved the EVD proposal as a standard.

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.

Although they disagree about physical format technology, both the HD-DVD and Blu-ray factions have selected the same three video codecs to be mandatory in their designs: specifically, MPEG-2 Part 2, VC-1, and H.264.

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.

Recently, Sony launched their first consumer HD camera called the HDR-FX1, which can record the 1080i60 format (the PAL version records 1080i50) on a Mini-DV tape using the HDV format. The camera uses the MPEG-2 codec to record the video and the audio and a 3-CCD system to accurately acquire color. Therefore, the HDR-FX1 closly matches a professional HD camera. JVC also released a consumer HD camera that records in 720p30 but uses a single CCD with only DV quality video. Apple's iMovie HD, Final Cut Express HD and Final Cut Pro HD (with Lumiere HD installed) can edit MPEG-2 HD/HDV stably. An Apple Macintosh computer is required to run this software. The OSS Cinelerra also makes HDV editing possible in recent versions and runs on a variety of different computer architectures.

References

See also

External links








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