Thursday, December 13, 2007

Equipment and Signal

When you've found an HDTV with a screen size, aspect ratio and native resolution you want, you'll need to make sure the equipment you already own will work with it. If you already have a DVD player, a DVR, game consoles or other equipment, make sure that they can connect to the TV directly or through an audio/visual receiver. Many HDTVs have High-Definition Multimedia Interface (HDMI) connections, which can transmit audio/visual signals to the TV without compression. In some cases, you can use adapters to make your equipment compatible with your set.

Once you've picked up your set and installed it in your home, you'll need to get a signal. To get a signal, you can use:

Photo courtesy Consumer Guide Products
With an antenna, you can get
digital television for free. This
Zenith model works best for
UHF analog and DTV signals.

  • An antenna - Depending on your location relative to the stations you want to watch, a set of rabbit ears might do, but you might need a rooftop or attic antenna. You can buy an antenna that's specially made for digital signals, but any reliable VHF/UHF antenna will work.
  • Cable - Keep in mind that digital cable is not the same as HDTV. You'll need to check with your provider to determine which packages include HDTV stations. You'll also either need a set-top cable box or a CableCARD™ to allow your television to receive and decode the cable signal.
  • Satellite service - As with cable, check with your provider to determine which plans and stations use HDTV signals. You may need a different satellite dish and tuner to receive HDTV signals via satellite.

To learn more about TVs, HDTVs and digital broadcasting, check out the links on the next page.

Sets marked "digital cable ready" or "plug-and-play" are equipped to use a CableCARD™. A CableCARD is a PCMCIA type II card, or PC card, that takes the place of a set-top cable box. It encrypts and decrypts cable signals and may reduce cable theft.

Your cable company will install the card, and you'll pay a small monthly rental fee, which can cost less than a cable box rental. You'll also have one less remote control to deal with. However, current CableCARDs allow one-way communication only. If you choose to use one, you will not be able to access interactive menus or buy video-on-demand or Pay-per-View programming. If you use any of these services, you should wait until the next generation of CableCARDs comes out. Check out Ars Technica for more information on CableCARD technology.

HDTV - Technical details

One of the first DVB-S2 tuner cards.
One of the first DVB-S2 tuner cards.

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, such as the BBC which is trialing such a system via satellite broadcast, which will save considerable bandwidth compared to MPEG-2 systems. Some German broadcasters already use MPEG-4 AVC together with DVB-S2 (Pro 7, Sat.1 and Premiere). Although MPEG-2 is more widely used at present, it seems likely that in the future all European HDTV may be MPEG-4 AVC, and Norway, which is currently in the progress of implementing digital television broadcasts, is using MPEG-4 AVC for present SD Digital as well as for future HDTV on terrestrial broadcasts. In parts of Sweden the standard is already in use for HDTV terrestrial broadcasting, reaching about 25-30% of the population.

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, in which each pixel's height equals its width. New HD compression and recording formats such as HDV use rectangular pixels to save bandwidth and to open HDTV acquisition for the consumer market. For more technical details see the articles on HDV, ATSC, DVB, and ISDB.

Television studios as well as production and distribution facilities, use HD-SDI SMPTE 292M interconnect standard (a nominally 1.485 Gbit/s, 75-ohm serial digital interface) to route uncompressed HDTV signals. The native bitrate of HDTV formats cannot be supported by 6-8 MHz 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 Cinealta F23 & 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.

HD ready (1080p) requirements

In order to be awarded the label "HD ready 1080p" (not equivalent to Full HD) or the older "HD Ready" logo a display device has to cover the following requirements:

HD Ready 1080p HD Ready
Minimum native resolution 1920x1080 720 horizontal lines in widescreen ratio
Accepted video formats are reproduced without distortion Yes No
Display 1080p and 1080i video without overscan (1:1 pixel mapping) Yes No
Display native video modes at the same (or higher) refresh rate. Yes No
Analogue YPbPr HD input Yes Yes
Digital HDMI or DVI HD input Yes Yes
720p HD progressive (1280x720 @50 & 60HZ) Yes Yes
1080i HD (1920x1080 interlaced @50 & 60HZ) Yes Yes
1080p HD (1920x1080 progressive @24, 50 & 60HZ) Yes No
The HDMI or DVI input supports copy protection (HDCP) Yes Yes

Older products that bear the label "HD ready" may not display the full picture resolution possible from a HD source. Most HD-ready sets do not have enough pixels to give true pixel-for-pixel representation without interpolation of the higher HD resolution (1920x1080) - or (in rare cases) even the lower HD resolution (1280x720) horizontally (CRT based sets, or the plasma-based sets with 1024x768 resolution). This limitation has been removed in the "HD Ready 1080p" logo

The term HD compatible is also being used in Europe to indicate that a display device has HDMI capability but with lower than HD-ready resolution.

The following technical references apply to the above descriptions:

DVI: DDWG, “Digital Visual Interface”, rev 1.0, Apr 2, 1999 as further qualified in EIA861B, “A DTV Profile for Uncompressed High Speed Digital Interfaces” May 2002, furthermore allowing both DVI-D and DVI-I connectors, requiring compliance to both 50 and 60Hz profiles, and requiring support for both 720p and 1080i video formats.

HDMI: HDMI Licensing, LLC, “High-Definition Multimedia Interface”, rev.1.1, May 20, 2004

HDCP: Intel, “High-Bandwidth Digital Content Protection System”, rev 1.1, June 9, 2003.

(NB: on DVI HDCP rev 1.0 will apply)

YPbPr: EIA770.3-A, March 2000, with the notice that the connectors required may be available only through an adaptor.


Nano-TV enters the flat-screen fray

Plasma under threat? A model relaxes in front of the Panasonic plasma HDTV screen at the Panasonic stand during the recent CeBIT computer fair in Hanover, Germany.

Plasma under threat? A model relaxes in front of the Panasonic plasma HDTV screen at the Panasonic stand during the recent CeBIT computer fair in Hanover, Germany.
Photo: Reuters

Plans are afoot to pilot test the world's first widescreen nano-TV following a recent pact between Applied Nanotech of the US and a Taiwanese manufacturer.

The nano-TV, which goes under the official title of Carbon Nanotube Television (CNT), is a next-generation display technology that its creators hope will deliver better picture quality than existing plasma and LCD TVs.

A letter of intent was signed yesterday between Applied Nanotech and Da Ling Co to form a joint venture with the aim of constructing a pilot line of the units.

The nano-TVs will be built with 60 to 100 inch diagonal screens and units are expected retail for $US1,300 ($1,800) when they hit full production. But first the technology must go through a series of trials that are scheduled to begin later this year or early next year.

The CNT is not the only new kid on the block when it comes to emerging display technologies. New surface-conduction electron-emitter displays (SED) were also recently unveiled by Canon and Toshiba to challenge existing TV technologies and the units are expected to go on sale in the fourth quarter of next year.

Like the nano-TV technology, the SEDs are believed to deliver clearer images with no "ghosting" because they are based on technology that is similar to traditional cathode-ray tube TVs.

The nano-TVs are also designed to be large and flat, and they deliver images to the display using carbon nanotubes with high thermal and electrical conductivity.

A 25-inch proof of concept was built last year by Applied Nanotech which the company said demonstrated sharper images than those currently observed in large LCD and plasma TVs .

"We expect CNT TVs to become the standard in large size flat panel displays," said Dr Zvi Yaniv, chief executive of Applied Nanotech.

Buying an HDTV

As you're shopping, you'll probably see some enhanced definition TV (EDTV) sets. EDTV isn't one of the digital broadcast formats -- it's a description of the level of picture quality the set can produce. An EDTV set can produce better quality than SDTV, but it's not an HDTV set. Most EDTV sets are flat-panel LCD or plasma sets.The DTV transition is not the first change to the TV signal. In 1946, the National Television System Committee (NTSC) began setting standards for American broadcasting. In 1953, NTSC standards changed to allow color television, and in 1984, they changed to allow stereo sound.

Those changes were different from the DTV switch because they were backwards compatible -- you could watch the new signal on your trusty old TV. With DTV, you'll need some new gear, and the gear you choose will affect whether you can receive and view high-definition video. You can learn about buying a DTV set in How Digital Television Works -- here, we'll focus on HDTV.

When you start shopping, keep in mind that HDTV requires three parts:

  • A source, such as a local, cable or satellite HDTV station
  • A way to receive the signal, like an antenna, cable or satellite service
  • An HDTV set
Motorola HDTV receiver
Photo courtesy Consumer Guide Products
If you purchase an HDTV-ready set, you'll need a receiver before you can watch high-definition broadcasts.

Most people start with the set. You can choose:
  • An integrated HDTV, which has a digital tuner, also known as an ATSC tuner, built in. If a station near you is broadcasting in HDTV, you can attach an antenna to an integrated set and watch the station in high definition.
  • An HDTV-ready set, also called an HDTV monitor, which does not have an HDTV tuner. HDTV-ready sets often have NTSC tuners, so you can still watch analog TV with them. This is the option for you if you want to have HDTV capabilities later on but aren't ready for the financial commitment now. Your picture quality will still be better than on your old TV, but it won't be high definition until you get an HDTV receiver.

Designing and building an HDTV that could display all of the ATSC formats would be virtually impossible. For this reason, HDTVs have one or two native resolutions. When the TV receives a signal, it will scale the signal to match its native resolution and de-interlace the signal if necessary. A good rule of thumb is to choose a set that has a native resolution matching the signals you plan to use most often. Film fans will generally want displays with the highest possible resolution. Sports fans will generally want displays with the highest possible progressive frame rate.

84-inch HDTV-ready plasma TV
Photo courtesy Consumer Guide Products
An HDTV-ready plasma TV

If you receive a signal that has a significantly lower resolution than your screen can display, all the extra pixels won't help it look better. This is why some people who have bought HDTVs have been dismayed at the quality of the picture - the existing analog signal just doesn't have enough detail to look good on a high-definition set. As broadcasters change to a digital signal, this problem will improve substantially.

In the next section, we'll look at the options for getting a signal to your TV as well as the compatibility of your existing home entertainment equipment.

HD Ready

Current logo for 1080p sets
Current logo for 1080p sets
HD ready logo for earlier devices
HD ready logo for earlier devices

HD ready concerns the ability of television receivers to display high-definition pictures. The term has had official use in Europe since January 2005 when, EICTA (European Information, Communications and Consumer Electronics Technology Industry Associations) announced the requirements for the label.

EICTA introduced the label as a quality sign for the differentiation of display equipment, capable of processing and displaying high-definition signals. It is awarded on the basis of minimum functionality requirements that are detailed in the "EICTA conditions for HD Labelling of Display Devices".

In the USA, "HD Ready" refers to any display that is capable of accepting and displaying a high-definition signal at either 720p, 1080i or 1080p using a component video or digital input, and does not have a built-in HD-capable tuner.

Alternatives to HD ready TVs

Many PCs and laptops are actually more HD ready, in the true sense of the phrase, than the HD ready label requires. They will not, however, qualify for the HD ready label, unless they also meet the connector requirements.

Any sufficiently fast computer with a 1280x720 or higher resolution display is capable of displaying HD video, even though computers are generally not advertised as such. This video may come from the Internet, data files, or a DTV tuner card. The Internet already offers some HD content, like movie and videogame trailers.

Blu-ray Disc

Reverse side of a Blu-ray Disc
Media type: High-density optical disc
Encoding: MPEG-2, MPEG-4 AVC (H.264), and VC-1
Capacity: 25 GB (single layer), 50 GB (dual layer)
Read mechanism: 1x@36 Mbit/s & 2x@72 Mbit/s
Developed by: Blu-ray Disc Association
Usage: Data storage, High-definition video and PlayStation 3 Games

Blu-ray Disc is a high-density optical disc format for the storage of digital information, including high-definition video.


The name Blu-ray Disc is derived from the blue-violet laser used to read and write this type of disc. Because of its shorter wavelength (405 nm), substantially more data can be stored on a Blu-ray Disc than on the DVD format, which uses a red (650 nm) laser. A single layer Blu-ray Disc can store 25 gigabytes (GB), over five times the size of a single layer DVD at 4.7 GB. A dual layer Blu-ray Disc can store 50 GB, almost six times the size of a dual layer DVD at 8.5 GB.

Blu-ray was developed by the Blu-ray Disc Association, a group of leading companies representing consumer electronics, computer hardware, and motion picture production. The standard is covered by several patents belonging to different companies. As of March 2007, a joint licensing agreement for all the relevant patents has not yet been finalized.[1]

As of November 25, 2007, 415[2] titles have been released on Blu-ray Disc in the United States (32 of those titles have since been discontinued). As of October 9, 2007, 179 titles have been released in Japan, with 55 titles planned for release.[3]

The Blu-ray standard is currently in a format war with its rival HD DVD, to determine which (if either) of the two formats will become the leading carrier for high-definition content to consumers.


HD DVD logo
Media type: High-density optical disc
Encoding: VC-1, H.264, and MPEG-2
Capacity: 15 GB (single layer)
30 GB (dual layer)
51 GB (triple layer) [1]
Read mechanism: 1x@36 Mbit/s & 2x@72 Mbit/s
Developed by: DVD Forum
Usage: Data storage, including high-definition video

HD DVD or High-Definition DVD is a high-density optical disc format designed for the storage of data and high-definition video.


HD DVD is designed to be the successor to the standard DVD format and is derived from the same underlying technologies. Since all variants except the 3x DVD employ a blue laser with a shorter wavelength, it can store about 3 1/2 times as much data per layer as its predecessor (maximum capacity: 17 GB instead of 4.7 GB per layer). A 51 GB triple-layer spec has been approved, however no movies are currently scheduled for this disc type.[2]

HD DVD is currently in a "format war" with rival format Blu-ray Disc, to determine which of the two formats will become the leading carrier for high-definition content to consumers.

As of November 27, 2007, 344 HD DVD titles have been released in the USA.[3] As of September 15, 2007, 133 HD DVD titles have been released in Japan, with 21 titles pending to be released.[4]

Broadcast station format considerations

Close-up view
HDTV resolution SDTV resolution

At the least, HDTV has twice the linear resolution of standard-definition television (SDTV), thus showing greater detail than either analog television or regular DVD. The technical standards for broadcasting HDTV also handle the 16:9 aspect ratio images without using letterboxing or anamorphic stretching, thus increasing the effective image resolution.

The optimum format for a broadcast depends upon the type of videographic recording medium used and the image's characteristics. The field and frame rate should match the source and the resolution. A very high resolution source may require more bandwidth than available in order to be transmitted without loss of fidelity. The lossy compression that is used in all digital HDTV storage and transmission systems will distort the received picture, when compared to the uncompressed source.

Types of medium

The high resolution photographic film used for cinema projection is exposed at the rate of 24 frames per second. Depending upon available bandwidth and the amount of detail and movement in the image, the optimum format for video transfer is either 720p24 or 1080p24. When shown on television in PAL system countries, film must be projected at the rate of 25 frames per second by accelerating it by 4.1 per cent. In NTSC standard countries, the projection rate is 30 frames per second, a using a technique called 3:2 pull-down. One film frame is held for three video fields (1/20 of a second), and the next is held for two video fields (1/30 of a second) and then the process is repeated, thus achieving the correct film projection rate with two film frames shown in 1/12 of a second. Template:Cf.

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.

Non-cinematic HDTV video recordings are recorded in either the 720p or the 1080i format. The format used is set by the broadcaster (if for television broadcast). In general, 720p is more accurate with fast action, because it progressively scans frames, instead of the 1080i, which uses interlaced fields and thus might degrade the resolution of fast images.

720p is used more for Internet distribution of high-definition video, because computer monitors progressively scan; 720p video has lower storage-decoding requirements than either the 1080i or the 1080p.


The Advanced Television Standards Committee (ATSC) has set voluntary standards for digital television. These standards include how sound and video are encoded and transmitted. They also provide guidelines for different levels of quality. All of the digital standards are better in quality than analog signals. HDTV standards are the top tier of all the digital signals.

Aspect ratios: Standard vs. high-definition
Standard vs. high-definition aspect ratio

The ATSC has created 18 commonly used digital broadcast formats for video. The lowest quality digital format is about the same as the highest quality an analog TV can display. The 18 formats cover differences in:
  • Aspect ratio - Standard television has a 4:3 aspect ratio -- it is four units wide by three units high. HDTV has a 16:9 aspect ratio, more like a movie screen.
  • Resolution - The lowest standard resolution (SDTV) will be about the same as analog TV and will go up to 704 x 480 pixels. The highest HDTV resolution is 1920 x 1080 pixels. HDTV can display about ten times as many pixels as an analog TV set.
  • Frame rate - A set's frame rate describes how many times it creates a complete picture on the screen every second. DTV frame rates usually end in "i" or "p" to denote whether they are interlaced or progressive. DTV frame rates range from 24p (24 frames per second, progressive) to 60p (60 frames per second, progressive).

Many of these standards have exactly the same aspect ratio and resolution -- their frame rates differentiate them from one another. When you hear someone mention a "1080i" HDTV set, they're talking about one that has a native resolution of 1920 x 1080 pixels and can display 60 frames per second, interlaced.

The 18 primary DTV standards
The 18 Primary DTV Standards

Broadcasters get to decide which of these formats they will use and whether they will broadcast in high definition -- many are already using digital and high-definition signals. Electronics manufacturers get to decide which aspect ratios and resolutions their TVs will use. Consumers get to decide which resolutions are most important to them and buy their new equipment based on that.

Until the analog shutoff date, broadcasters will have two available channels to send their signal -- a channel for analog, and a "virtual" channel for digital. Right now, people can watch an over-the-air digital signal only if they are tuned in to the broadcaster's virtual digital channel. After analog broadcasting ends, the only signals people will receive over the air will be digital.

However, even though a digital signal is better quality than an analog signal, it isn't necessarily high definition. HDTV is simply the highest of all the DTV standards. But whether you see a high-definition picture and hear the accompanying Dolby Digital® sound depends on two things. First, the station has to be broadcasting a high-definition signal. Second, you have to have the right equipment to receive and view it. We'll look at how to get an HDTV set and signal next.

DTV usually uses MPEG-2 encoding, the industry standard for most DVDs, to compress the signal to a reasonable size. MPEG-2 compression reduces the size of the data by a factor of about 55:1, and it discards a lot of the visual information the human eye would not notice was missing.

Is the U.S. Really Ready to Switch to Digital TV?

A federal study says regulators have no plan in place for the scheduled switch, little more than a year away.

WASHINGTON (Reuters) - U.S. regulators have "no comprehensive plan" for preparing TV viewers for the approaching switch-over to digital television, a congressional study released on Tuesday said.

The study by the Government Accountability Office took issue with the Federal Communications Commission for lacking an overall strategy for the February 17, 2009 switch, which will require broadcasters to change to digital signals from their traditional analog ones.

"Despite efforts by the public and private sectors and ongoing coordination, we found that no comprehensive plan for the transition exists," the GAO said.

The digital TV transition is being closely watched because owners of analog televisions will not be able to watch television unless they subscribe to satellite or digital cable, replace their TV with a digital television by that date or get a converter box.

Congress ordered the switch to digital television because it will free up valuable airwaves for other uses, such as for police and fire departments and because it will lead to improved picture and sound for TV viewers.

The federal government plans to subsidize the cost of buying a digital-analog converter box by offering $40 discount coupons to anyone who owns an analog television. That program is being overseen by an arm of the Commerce Department called the National Telecommunications and Information Administration.

The agency's chairman, Kevin Martin, responded in a letter to the GAO, saying he had "significant reservations and concerns with the report's approach and conclusions."

Martin also issued 99 pages of "comprehensive plans, goals and achievements" that the FCC had drawn up to address the digital TV transition.

In their report, the authors of the GAO study said Martin also told them that the FCC "does not have a formal plan in place that is publicly available, but that the various orders contained in FCC dockets amount to a plan."

The GAO's report credited the FCC, NTIA and private industry with making progress in educating consumers about the switch-over. It also said the NTIA had made progress on the converter box program.

The report said private players, including cable operators, broadcasters and the consumer electronics industry, had taken the lead in informing consumers about the digital TV transition.

In a related development, the NTIA issued a press release on Tuesday announcing that it had certified more than 100 retailers to participate in the converter box program, including Best Buy Co Inc, Circuit City Stores Inc , RadioShack Corp, Sears Holdings Corp, Target Corp and Wal-Mart Stores Inc.

The retailers represent more than 14,000 stores throughout the United States, the NTIA said.

But according to the GAO, the lack of a "comprehensive" plan makes the switch-over a riskier proposition, raising

potential problems, such as misinformation, inadequate funding and failure to reach some analog TV set owners.

"This raises uncertainty, including whether consumers, particularly underserved and otherwise vulnerable populations, will have the information necessary to respond to the transition and to maintain their access to television programming," the GAO report said.

The GAO report rekindled concerns among some Democratic lawmakers in Congress, who fear the agency is relying too heavily on voluntary industry efforts to notify consumers.

"Without a comprehensive plan that also addresses managing risks and mitigating against potential problems, tens of millions of consumers could be adversely affected and this important transition put needlessly in jeopardy," Democratic Rep. Edward Markey, of Massachusetts, said in a statement.

(Reporting by Peter Kaplan; editing by Carol Bishopric)

Copyright 2007 Reuters. Click for Restrictions.,140506-c,futuretechnology/article.html

New HDTVs Bring Higher Def, Better Color

Increased resolution, new peripherals and connections promise the best TV yet.

Falling prices aren't the only positive news for HDTV shoppers: New and upcoming sets boast higher resolution and improved image and sound quality. Here's what to look for.

1080p TVs

Click here to view full-size image.
Photograph: Robert Cardin

LCD televisions that can display images in 1080 progressive resolution (or 1080p, as opposed to the 720p capability of most HDTVs in our roundup) are increasingly common; and the format is getting support in such peripherals as Blu-ray drives, HD DVD drives (like Toshiba's HD-XA2), Sony's PlayStation 3, and Microsoft's Xbox 360 (via an accessory HD DVD drive). Also at hand is a growing collection of 1080p content on Blu-ray and HD DVD discs.

Plasma has been slow to reach 1080p because cramming lots of tiny pixels into a plasma panel is a manufacturing challenge. Big-screen 1080p plasmas are finally appearing, but they don't come cheap. Pioneer's 50-inch Pro-FHD1 retails for $8000, and Panasonic's 65-inch TH-65PX600U goes for an even heftier $10,000.

HDMI 1.3

The Playstation 3 and Toshiba HD-XA2 are also the first two devices to deliver 1080p content through the new HDMI 1.3 interface, which enables "Deep Color," meaning up to 48-bit color depth (the current high is 24 bits). "More colors allow for better gradation and color shading," says Eric Haruki, research director for TV markets and technologies with IDC. HDMI 1.3 also supports new 7.1-channel audio formats, including Dolby TrueHD and DTS-HD.

To experience HDMI 1.3's benefits, however, all your components--including the TV--must support the standard. "You don't need it to do 1080p, but it's still a good thing," says Scott Ramirez, vice president of marketing for Toshiba. LG Electronics, Mitsubishi, Samsung, Sharp, and others have promised HDMI 1.3 sets next year.,127312/article.html

More HDTV for Your Money

LCD, DLP, or plasma? Big, bigger, or biggest? We lab-tested 15 screens to find the best values in next-generation TV.

Click here to view full-size image.
Photograph: Marc Simon

Now more than ever, both bargain hunters and luxury seekers can find an HDTV to satisfy their high-def needs and their budgets. Whether you want an LCD, plasma, or DLP HDTV set, you can choose from a wide range of prices, and even the high-end models aren't as expensive as you might think. And you'll find more high-def content--from network and cable broadcasts to HD DVD movies--than ever before.

Deals abound in every size and technology category. PC World tested a total of 15 TVs across three popular technologies

(LCD, plasma, and DLP) and three popular screen sizes (37 inches, 42 inches, and 50 to 52 inches). For a little over $1000, you can buy an LCD or plasma TV with impressive picture quality. And today, thanks to DLP technology, a gigantic screen and even 1080p resolution may be within your reach.

To test each of the TVs, we played several high-definition clips, a couple of standard-definition clips, and scenes from two DVDs on each set. Our panel of judges scored each model based on its brightness, sharpness, and color clarity. Our verdict, after a thorough comparison of the sets: Lower-priced HDTVs frequently equal or better the performance of higher-priced sets. In addition to pinpointing which of the tested models are true screen stars, we have tips on how to shop for deals. Armed with this information, you'll be able to tell whether the next bargain that catches your eye is a great deal--or just a snare for the unwary.,127578/article.html

Analog, Digital and HDTV

For years, watching TV has involved analog signals and cathode ray tube (CRT) sets. The signal is made of continually varying radio waves that the TV translates into a picture and sound. An analog signal can reach a person's TV over the air, through a cable or via satellite. Digital signals, like the ones from DVD players, are converted to analog when played on traditional TVs. (You can read about how the TV interprets the signal in How Television Works.)

This system has worked pretty well for a long time, but it has some limitations:

  • Conventional CRT sets display around 480 visible lines of pixels. Broadcasters have been sending signals that work well with this resolution for years, and they can't fit enough resolution to fill a huge television into the analog signal.
  • Analog pictures are interlaced -- a CRT's electron gun paints only half the lines for each pass down the screen. On some TVs, interlacing makes the picture flicker.
  • Converting video to analog format lowers its quality.
analog CRT tv
Photo courtesy Consumer Guide Products
Analog TVs like this one can't use digital signals without a
set-top converter.

United States broadcasting is currently changing to digital television (DTV). A digital signal transmits the information for video and sound as ones and zeros instead of as a wave. For over-the-air broadcasting, DTV will generally use the UHF portion of the radio spectrum with a 6 MHz bandwidth, just like analog TV signals do.

DTV has several advantages:

  • The picture, even when displayed on a small TV, is better quality.
  • A digital signal can support a higher resolution, so the picture will still look good when shown on a larger TV screen.
  • The video can be progressive rather than interlaced -- the screen shows the entire picture for every frame instead of every other line of pixels.
  • TV stations can broadcast several signals using the same bandwidth. This is called multicasting.
  • If broadcasters choose to, they can include interactive content or additional information with the DTV signal.
  • It can support high-definition (HDTV) broadcasts.

DTV also has one really big disadvantage: Analog TVs can't decode and display digital signals. When analog broadcasting ends, you'll only be able to watch TV on your trusty old set if you have cable or satellite service transmitting analog signals or if you have a set-top digital converter.

This brings us to the first big misconception about HDTV. Some people believe that the United States is switching to HDTV -- that all they'll need for HDTV is a new TV and that they'll automatically have HDTV when analog service ends. Unfortunately, none of this is true.

HDTV is just one part of the DTV transition. We'll look at HDTV in more detail, including what makes it different from DTV, in the next section.

HDTV - Notation

HDTV broadcast systems are defined threefold, by:

  • The scanning system: progressive scanning (p) or interlaced scanning (i). Progressive scanning redraws an image frame (all of its lines) when refreshing each image. Interlaced scanning redraws the image field (every second line) per each image refresh operation, and then redraws the remaining lines during a second refreshing. Interlaced scanning yields greater image resolution if subject is not moving, but loses up to half of the resolution and suffers "combing" artifacts when subject is moving.
  • The number of frames per second or fields per second.

The 720p60 format is 1280 × 720 pixels, progressive encoding with 60 frames per second (60 Hz). The 1080i50 format is 1920 × 1080 pixels, interlaced encoding with 50 fields per second. Sometimes interlaced fields are called half-frames, but they are not, because two fields of one frame are temporally shifted. Frame pulldown and segmented frames are special techniques that allow transmitting full frames by means of interlaced video stream.

For commercial naming of the product, either the frame rate or the field rate is dropped, e.g. a "1080i television set" label indicates only the image resolution.[5] Often, the rate is inferred from the context, usually assumed to be either 50 or 60, except for 1080p, which denotes 1080p24, 1080p25, and 1080p30, but also 1080p50 and 1080p60 in the future.

A frame or field rate can also be specified without a resolution. For example 24p means 24 progressive scan 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.

Standard resolutions

Visual comparison of common TV display resolutions

When resolution is considered, both the resolution of the transmitted signal and the (native) displayed resolution of a TV set are taken into account. Digital NTSC- and PAL/SECAM-like signals (480i60 and 576i50 respectively) are transmitted at a horizontal resolution of 720 or 704 "pixels". However these transmitted DTV "pixels" are not square, and have to be stretched for correct viewing. PAL TV sets with an aspect ratio of 4:3 use a fixed pixel grid of 768 × 576 or 720 × 540; with an aspect ratio of 16:9 they use 1440 x 768, 1024 × 576 or 960 × 540; NTSC ones use 640 × 480 and 852 × 480 or, seldom, 720 × 540. High Definition usually refers to 720 vertical lines of resolution or more.

Common High-Definition Display Resolutions

Resolution (WxH) Pixels Aspect Ratio Name Description
1024×768 786,432 16:9 (non-square pixels) 720p/XGA Used on PDP HDTV displays with non square pixels
1280×720 921,600 16:9 720p/WXGA Used on Digital television, DLP, LCD and LCOS projection HDTV displays
1366×768 1,049,088 16:9 720p/WXGA Used on LCD/PDP HDTV displays (HD Ready, HD Ready 720p,1080i)
1024×1080 1,105,920 16:9 (non-square pixels) HD1080 Used on PDP HDTV displays (HD Ready, HD Ready 720p,1080i)
1280×1080 1,382,400 16:9 (non-square pixels) HD1080 Used on PDP HDTV displays (HD Ready 1080p)
1920×1080 2,073,600 16:9 1080p HDTV standard format Used on all types of HDTV technologies (HD Ready 1080p, Full HD)

A common resolutions used in HD Ready LCD TV panel are 1366 x 768[6] pixel instead of 1280 x 720 pixel - ATSC Standards. It is due to standard manufacturing yield and maximise resolution on VGA, VRAM that come with 768 pixel. Hence LCD manufacturers set to 16:9 ratio to be compatible for HD Ready 1080p standard, but nevertheless every HDTVs will have an overscan processing chipset to fixed resolution scaling and color screen, eg LG XD Engine, SONY BRAVIA Engine. Only when viewing 1080i/1080p HD contents under HD Ready 1080p where there are true pixel-for-pixel reproduction, and for HD ready LCD TV, there would be some signal undergoing scaling process which result in 3-5% loss of picture.