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HD TV

High-definition television (or HDTV, or just HD) refers to video having resolution substantially higher than traditional television systems (standard-definition TV, or SDTV, or SD). HD has one or two million pixels per frame, roughly five times that of SD. Early HDTV broadcasting used analog techniques, but today HDTV is digitally broadcast using video compression. Historically the term was also applied to television standards developed in the 1930 to replace test models. Also applied to earlier models of HD, particularly in Europe, called D2 Mac, and Mac HD, but could not be implemented widely. The terms HD ready (ready for HD) and HD compatible are being used for marketing purposes. These terms indicate that the electronic device has it may be a television or an overhead projector is capable of playing high-definition signals, but the fact that it is compatible with HD content does not imply that the device is high definition or have the necessary resolution, as happens with some plasma televisions with less vertical definition televisions for decades (833x480 instead of 720x576 pixels, equivalent to 940x576 anamorphic-), which are compatible with high definition signals because they reduce the resolution of the image to fit the actual screen resolution.

HDTV uses a 16:9 aspect ratio. High resolution images (1920 x 1080 pixels or 1280 x 720 pixels) can display much more detail compared to analog TV or standard definition (< em> Standard Definition , 720x576 pixels according to the standard PAL or 720x480 pixels for NTSC standard).

 

 

Comparación entre los distintos sistemas

 

 

 

 

 

 

 

n this case, comparing the total pixels offered an image of defining "standard" vs. a high definition we have:

 

SDTV 720x480 pixels: 345,600 total pixels

 

HDTV 1280x720 pixels: total pixels 921,600 (2.6 times more than SDTV)

 

1920x1080 pixels: total pixels 2073600 (6 times SDTV)

 

In PAL, HDTV is about 5 times better than standard definition, compared with the highest definition HDTV. It should be mentioned that the format of analog TV or standard NTSC, 480i (720x480 pixels), really are 240 interlaced lines which, when scanned one and the other alternatively at 60 frames per second, forming a picture of 480 lines. Formats like "high definition" intertwined (eg 1080i) are not high-resolution true, since in this case are actually 1080i interlaced 540 lines displayed at 60 frames per second, similar to 60 Hz interlaced NTSC , which together form an image of 1080 lines, although the comparison with analogue TV picture quality, is much higher. In areas where you use the PAL standard is used scans at 50Hz (50 frames per second) in the case of serious 1080i 1080i50. The 1920x1080 resolution is usually interlaced mode (1080i) to reduce bandwidth demands, this mainly in HDTV broadcasts, but recently many broadcasters are choosing to transmit in 720p, mainly in the U.S. (720p60). The true high definition is considered in this case the progressive formats. The true high definition is considered in this case the progressive formats. 1080 presented the 1080 lines all the time, 60 frames per second, cooling the whole picture every time. 720p 720 lines would present all the time, at 60 frames per second, cooling the whole picture every time. The codec used for compression may be MPEG-2, H.264 or VC-1 (Standard to be implemented in Windows Media Video 9), although the MPEG-2 is running out of date now due to its low compression efficiency compared to other codecs such as MPEG-4 or more popularly known as MP4. A televison multiplexed accepts a maximum of 24Mbps. Using MPEG2 only could put a HD channel, so that would be an inefficient use of the multiplex. Using MPEG4AVC could accommodate up to 3 HD channels or two HD and two SD. However MPEG4AVC requires processors to 8 times more powerful due to complicated compression algorithms.

 

Formato	SD	1280x720p (4:3)@24	1280x720p (16:9)@50 @60	1920x1080p (16:10)@30
MPEG2	4,2 Mbps	9 Mbps	13,6 Mbps	16,2 Mbps
Advanced Encoding	2,5 Mbps	5,6 Mbps	8 Mbps	10 Mbps

 

HDTV has at least twice the resolution of SDTV, why can show much more detail compared to analog television or regular DVD. In addition, technical standards for HDTV broadcast can be projected using a 16:9 aspect ratio without the use of black bars and therefore can increase the resolution of the content.

 

First systems:

 

MUSE. The HD technology has over 25 years. The pioneers were the Japanese, who have continued in HD transmissions for over 15 years. The country of the rising sun began with a system of 1035 lines of resolution called MUSE, NHK developed by the company in 1979. The main problem with this system was the excessive use of drive belts, as required up to 5 times more space than a standard channel.

 

HD-MAC. The European Commission established a European standard for uncompressed digital HDTV using a directive in 1986 (MAC). However, it was never popular with broadcasters. Required all issuers of high-powered satellite will use MAC from that year. Due to technological advancement and the introduction of medium-power satellites for SES Astra, the stations could work well without MAC to lower transmission costs. MAC HD (high definition variant of MAC) was left for transcontinental satellite links.

The Barcelona '92 Olympics were recorded in this analog format (4:3 aspect ratio, with a resolution of 1152 vertical lines). To store magnetic tapes were used phonic giant size of a suitcase each. These tapes incorporating a handle on its housing for easier transport and handling.

But besides the problem of storage, another cause of the failure of HD-MAC 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), while still more exaggerated the difference in bandwidth in Japan. HD-MAC could only be used by cable and satellite companies, where there is more bandwidth available. Thus, analog HDTV failed to replace the traditional SDTV (terrestrial) PAL / SECAM, making HD-MAC teams unattractive to potential consumers.

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

 

 

 

 

 

 

 

Current Systems:

There are three standards defined: the U.S. (ATSC), the European (DVB-T) and Japan (ISDB-T).

 

ATSC: Designed to add a digital transmitter to each transmitter without interference from NTSC signals. Used in Mexico, South Korea, Canada, the United States and some Latin American countries with the capacity to transmit in HD is expected to be ready in late 2008 the portable transmission standard (for laptops, mobile phones) as reported ATSC standard spokesman at a conference in New Granada Military University in Bogota, Colombia.

 

DVB-T: It is portable and has been successfully tested at speeds of up to 170 mbps. Used in Europe, Colombia, Argentina, Uruguay, India, China, South Africa, Australia and some Asian countries. To improve their skills and correct some of its weaknesses and limitations currently in test development and implementation of the new system will require new DVBT2 'Set Top Box "STB decoders because it plans to coexist with the old DVB-T-from 1997 - but no firm expected to start until after the 'analogue switch' which will release much of the electromagnetic spectrum already crowded in Europe.

 

ISDB-T: It is flexible and can be used in 6, 7 and 8 MHz adapting easily to anywhere in the world is compatible with NTSC and PAL, you can send audio signals and high-quality image (FULL HDTV and CD quality audio sound or 5.1) or you can multiplex up to 8 channels of standard definition and optimize the radio spectrum. It also has multimedia services and interactive feedback from homes. Has the ability to broadcast to mobile devices free of charge and with the same existing infrastructure in the TV channel, with low power is capable of covering large areas of rugged terrain such as Japan and Chile and much of the mountainous and border Pacific. Is the official digital TV standard in Japan and Brazil and much of Latin America want to incorporate it as official policy.

 

Europe. For now, many countries have shown a limited interest in HDTV. The most common is using DVB EDTV.

While HDTV is still possible with DVB-T2, most countries prefer "more channels in one multiplex" instead of "a single HDTV channel, most common in the U.S.. UU., Canada, Japan and Australia. As a single HDTV channel occupies the bandwidth of up to four channels of SDTV (* at 8 MHz), HDTV is not appropriate for the needs of terrestrial broadcast in Europe.

In addition, some governments want to go digital instead of VHF frequencies reallocated for other uses.

A new version of DVB-S (DVB-S2), combined with the H.264/AVC codec (MPEG-4 Part 10) may be the key to future success of HDTV in Europe.

In January 2005, EICTA announced plans for a label "HD ready" (suitable for HD) for equipment that meets certain requirements, including support for 720p and 1080i at 50 and 60Hz. The screens should include interfaces and DVI or HDMI YUV and have a native vertical resolution of 720 lines or more.

Currently there is a unique platform to broadcast in HD across Europe. It Euro1080 satellite platform which broadcasts in 1080i (currently MPEG-2, in the future under the rules MPEG-4/H.264).

 

UNITED STATES.High-definition television in the United States was introduced in 1998 and has since become increasingly popular. Dozens of HD channels are available in millions of homes and businesses both terrestrially and via subscription services such as satellite, cable and IPTV. A November 2009 survey by Home Media Magazine found that between 33 and 50 percent of Americans have at least one HDTV in their home. Also, 66 percent said they subscribe to HDTV services.

High definition versus standard or enhanced definition: It is not clear whether broadcasting HDTV or multiple standard definition (SD) channels during non-primetime hours will become common. Many Public Broadcasting Service member stations are now carrying SD multicasts when not broadcasting in HDTV; but unlike many commercial stations, most of these multicasts are suspended while HDTV programs are being broadcast. The prevailing expectation is that native HDTV (i.e., programming recorded with a digital HDTV camera) during primetime will predominate. The great majority of primetime television shows in the United States are available in HDTV at the network level. It is up to the affiliates, not all of which have HDTV broadcast capability, to retransmit these shows at HDTV resolutions. A number of non-primetime shows, including morning news shows and some soap operas, are also available in HDTV.

From proposals to introduction: The Federal Communications Commission (FCC) began soliciting proposals for a new television standard for the U.S. 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. On July 23, 1996, WRAL-TV (the CBS affiliate in Raleigh, North Carolina) became the first television station in the United States to broadcast a digital television signal.[2] HDTV sets became available in the U.S. in 1998 and broadcasts began around November 1998. The first public HDTV broadcast was of the launch of the space shuttle Discovery and John Glenn's return to space; that broadcast was made possible in part by Harris Corporation.[3] The first major sporting event broadcast in HD was Super Bowl XXXIV on January 30, 2000.

Satellite and cable: Satellite television companies in the United States, such as Dish Network and DirecTV, started to carry HD programming in 2002. Satellite transmissions in the U.S. use various forms of PSK modulation. A separate tuner is required to receive HD satellite broadcasts. Cable television companies in the U.S. generally prefer to use 256-QAM to transmit HDTV. Many of the newer HDTVs with integrated digital tuners include support for decoding 256-QAM in addition to 8VSB for OTA digital. Some cable television companies, such as Comcast, started carrying HDTV in 2003. Currently, HD programming is carried by all major television networks in most DMAs, including ABC, CBS, NBC, FOX, PBS, The CW, MyNetworkTV and Telemundo; and on some independent stations.

EUROPEAN UNION. The European Commission reviewed the status of emissions to 16:9, as well as HDTV in the document The contribution of wide-screen and high definition to the global roll-out of digital television (The contribution of widescreen and high definition to the global expansion of digital television.) This document states that the above objectives for the Europe-wide introduction of HDTV, 1999 (or HD-MAC in 1992) were not achieved because the market is focused on digital technologies and services easier to implement. Thus, European consumers have never had the opportunity to try the HDTV. It also suggests some causes for the poor representation of HDTV in the European Union (EU):

* The rulers of the European market thought the fail HDTV in Europe.

* The issuers preferred to focus on multi-channel SDTV, cheaper. * A screen resolution SDTV has a better cash cost equivalent to an HDTV. Later, the commissioners suggested that some coordination is required in the EU for HDTV services that were available to all member states.