How HDTV Works

by Tracy V. Wilson

Introduction to How HDTV Works
When the first high-definition television (HDTV) sets hit the market in 1998, movie buffs, sports fans and tech aficionados got pretty excited, and for good reason. Ads for the sets hinted at a television paradise with superior resolution and digital surround sound. With HDTV, you could also play movies in their original widescreen format without the letterbox "black bars" that some people find annoying.
Shopping for an HDTV?
Compare HDTV prices at Consumer Guide Products before you buy.

But for a lot of people, HDTV hasn't delivered a ready-made source for transcendent experiences in front of the tube. Instead, people have gone shopping for a TV and found themselves surrounded by confusing abbreviations and too many choices. Some have even hooked up their new HDTV sets only to discover that the picture doesn't look good.

Fortunately, a few basic facts easily dispel all of this confusion. In this article, we'll explain the acronyms and resolution levels and give you the facts on the United States transition to all-digital television. We'll also tell you exactly what you need to know if you're thinking about upgrading to HDTV.



Analog, Digital and HDFor 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.

Photo courtesy HowStuffWorks Shopper

Analog TVs like this one can't use a digital signal 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

by Edward Jay Epstein

---

Converting to high-definition television (HDTV), whatever its benefits to American civilization, would be possibly the most costly modernization ever undertaken voluntarily. It would far exceed the cost of building the interstate highways. Even if Americans bought the cheapest equipment available today, they would need to spend more than $300 billion just to replace their analog TVs with ones capable of receiving HDTV. Television stations also would have to spend tens of billions of dollars for new equipment. To provide the carrot for this massive conversion, the federal government has already committed itself to giving away much of the remaining frequency spectrum to television stations. The public, as its incentive for converting, will get a more elongated picture -- using a 16:9 instead of 12:9 ratio of width to height -- that provides better resolution in newscasts, game shows, reality-based voyeurism, soap operas, wrestling matches and other entertainments. The public's gain has been difficult to fully assess because very few people have ever actually seen regular HDTV broadcasts.

Indeed, until very recently, HDTV was not broadcast in a form in which most Americans could get it without an antenna complex. Television stations had little incentive for broadcasting HDTV, since very few people had the ability to receive it. So they put it on relatively obscure UHF stations as a public relations gesture. Unfortunately, according to tests done by Sinclair Broadcasting, the largest broadcaster group, indoor antennas would not work without a direct line of sight to the transmitting antennas, nor if there was any interference. Further adding to its unavailability, the cable industry, which did not participate in the spectrum giveaway and thus had no incentive to show HDTV, declared that the home cable box was incompatible with it. Similarly, the satellite narrowcasters, DirectTV and EchoStar, although digitized, had little reason to launch the new satellites necessary to carry broader-band HDTV -- at least not until a significant portion of the public had the hardware to receive these signals. It was a chicken-and-egg situation: no sets, no reason to broadcast; no broadcasts, no reason to buy a set.

Like other concerned citizens, I wanted to evaluate this new technology. But I was discouraged when a high-ranking executive at Sony told me that she had considered having the company install a giant antenna on the roof of its skyscraper in New York to get HDTV broadcasts for its showroom, but had found that the cost of providing a reliable signal was "prohibitive." If Sony, which employs 100,000 engineers and technicians, could not get a reliable HDTV of its own, what chance had I of getting one in my New York apartment?

Then, just two weeks ago, I heard through the Internet grapevine that there might be a means of getting HDTV free. My proximate source was Bill Cushman, a Houston-based writer for the video magazine The Perfect Vision, who keeps close contact with the small but resourceful community of HDTV seekers. He passed on the rumor that Time Warner was secretly transmitting HDTV on unused channels of its cable system in New York, presumably to test it out. To get it, he suggested, I merely had to discard my cable box and hook the cable into a HDTV decoder.

I immediately called Time Warner in New York. The customer representative came on the line and courteously denied the rumor that there was free HDTV on its cable. There was now only one way to find out. I bought a RCA Digital Decoder ($630), which arrived by FedEx the next morning. I then unplugged the cable from the cable box and replugged it into the "Antenna A" slot on the HDTV decoder, which was connected to my Sony HDTV- ready projector. Less than 5 minutes later, I was watching HDTV on two channels, CBS and (free) HBO. It was in the 16:9 format with Dolby digital sound (CBS had five channels, HBO only two). To fine-tune these channels, one needs the service access code for the RCA decoder. Fortunately, like many other codes, it is available on the Internet.

Then, to find out what was available over the airwaves as opposed to cable, I mounted an eight-foot UHF ChannelMaster antenna on my roof, which I plugged into the "Antenna B" slot on the RCA decoder. After getting a number of tips from the Internet -- including the useful site at www.antennaweb.org1, which draws a street map from your address showing the precise path to all obtainable digital stations -- I got WNYW, the Fox digital station. According to Internet tipsters, I might also get WTNH, the ABC digital station in New Haven, Conn., and WNJT, the PBS digital station in Trenton, N. J., under the right weather conditions. But at present I can count on only three digital stations, and not everything they broadcast is converted to HDTV. Nevertheless, the material that is broadcast in HDTV -- especially the CBS programs for which Mitsubishi paid to convert and the 16:9 formatted movies on HBO -- provide an ample opportunity to assess this new technology.

There can be no doubt that HDTV renders a picture that is vastly superior to the one on conventional television. HDTV uses roughly 500,000 color pixels; conventional television uses the equivalent of about 50,000. Consider, for example, a picture of 100,00 people at a political demonstration. On HDTV, each person could be represented by five different color pixels, which could show them with multiple color outfits and banners. Conventional television would have to use one color pixel to represent every two persons, turning them into a blur. Suddenly, it becomes possible to see individually tinted hairs on a head or weeds on a baseball diamond. This cumulatively adds up to the illusion of depth, complexity and three-dimensionality. It is, in a word, fabulous.

The price for this new diversion and deception is relatively steep. Unfortunately, smaller HDTV receivers, which cost more than $2,000 (without the decoder), will not provide the full virtual-reality illusion (unless one sits only a few inches away at the risk of one's vision). So one needs a projection HDTV receiver costing between $4,000 and $8,000, as well as a decoder (another $600 to $1,000.) Then there is the cost of getting a signal. Unless one can tap into one's local cable for HDTV, as I did, one will have to invest in some sort of rooftop antenna farm or at least a satellite dish. Of course, there is the risk that HDTV will be abandoned once television stations get full title to their digital licenses. (Stations can pack four non-HDTV digital channels in the space required for one HDTV channel.) But why not see HDTV while the opportunity nobly provided by Time Warner still exists? If, of course, you can afford it.

HDTV

Samsung TH-50PX60U Description

Featuring Panasonic's 9th generation gas-plasma screen, the 50-inch TH-50PX60U features a width-to-height 16:9 aspect ratio similar to movie theater screens, providing a theater-like experience at home. Its maximum of 29 billion colors and over 3,000 shades of gradation provide exceptionally fine detail for outstanding HDTV reproduction. The set's built-in ATSC (DTV) tuner pulls HD signals (480p/720p/1080i) right from the airwaves, and its QAM tuner is fully compatible with unscrambled HDTV cable reception. A standard analog NTSC tuner receives standard-definition (SD) programming. It also includes a Secure Digital (SD) memory card slot, enabling you to take an SD card directly from a digital still camera or camcorder and insert it directly into the TV for quick and colorful photo slideshows.
A plasma screen renders vivid colors like you've never seen before (as in, up to 29 billion in this case), extremely wide viewing angles (wider, even, than those of most LCD screens), and easy placement due to a plasma monitor's slim profile--the TH-42PX60U is a mere 3.7 inches deep, one of the slimmest plasmas around--perfect for desk or wall mounting. Brightness tends to be extremely uniform across plasma screens, which are also impervious to the picture distortion and negative color balances that afflict CRT monitors when placed near lighting or sound systems.

The TH-50PX60U features a 1366 x 768-pixel resolution and an amazing contrast ratio of 10000:1. (The higher the contrast ratio, the greater a TV's ability to display subtle color details and not get washed out by ambient room light.) The 3D Y/C digital comb filter constantly analyzes the three dimensions of picture height, picture width, and picture changes-over-time, to reduce dramatically edge image artifacts while improving transition detail. Other features include V-Chip parental controls, on/off sleep timers, closed-caption decoding, aspect ratio control, and video input labeling.
The TV's internal stereo speakers are powered by 10 watts per channel (for 20 watts of total power). It features the following connection options:
Component (Y/Pb/Pr): 2 inputs (with 2 audio inputs)
HDMI: 2 inputs
Composite (RCA audio/video): 3 inputs (1 on the front), 1 output
S-Video: 3 inputs (1 on the front)
HDMI (High-Definition Multimedia Interface) is a lossless, uncompressed, all-digital audio/video interface to link any AV source with an audio and/or video monitor, such as a digital television (DTV). HDMI supports standard-definition (SD), enhanced definition (ED), or high-definition (HD) video, plus multi-channel digital audio--all using a single cable.
If a component doesn't have an HDMI connection, you'll also get great picture reproduction using the three-jack component video (Y/Pb/Pr) input, which provides separate connections for luminance (Y), blue color difference (PB) and red color difference (PR). This results in increased bandwidth for color information, resulting in a more accurate picture with clearer color reproduction and less bleeding than you would get with S-Video or composite (RCA yellow video plug) connections. Component video output is available only for DVD playback.
What's in the BoxPlasma TV, remote control (with batteries), pedestal base, power cord, printed operating instructions Product DescriptionThe TH-50PX60U 50" Diagonal Plasma HDTV gives you deep blacks, bright whites and 29 billion colors -- it's an image so close to real life, you'll swear you were in your favorite programs instead of just watching them. Enjoy crisp, lifelike details with the up to 10,000:1 contrast ratio. Deep blacks provide excellent shadow detail during dark scenes, while brilliant whites render bright scenes with vivid realism. Receive and view local over-the-air broadcasts in stunning HD, using the built-in HDTV tuner. You can even share your JPEG photos taken with the built-in SD card slot. Features a width-to-height ratio similar to movie theater screens, providing a theater-like experience at home. View HDTV broadcasts and widescreen DVDs the way they were meant to be seen. Native Resolution - 1366 x 768 Contrast Ratio - Up to 10,000 - 1 Progressive Scan Video Noise Reduction Digital Comb Filter Color Purity Optimizer (3D Color Management) Two 20-watt, 8 ohm speakers -- 70Hz - 17kHz, 10% THD Surround Sound Motion Pattern Noise Reduction BBE ViVA HD3D Sound Standard NTSC tuner ATSC/QAM (SDTV and HDTV broadcasts) SD Card Slot & Photo Viewer HDMI-HDCP Interface - 2, in rear Analog Audio Input (for HDMI) - 1 rear Composite Video Input - 3 (2 rear, 1 front) S-Video Inputs - 3 (2 rear, 1 front) Audio Input (for Video) - 3 (2 rear, 1 front) Rear Inputs/Outputs - 2 Component Video (YPbPr), 2 Component Audio out, 1 Composite & Audio out On-screen display languages - English/Spanish/French Timers - Sleep/On/Off Built-in closed-caption decoder Video Input Labeling V-Chip Program Lockout Includes remote control & pedestal stand Unit Dimensions(HxWxD) - 32.2 x 47.6 x 3.7 Unit Weight - 89.5 lbs

HDTV signal reception

HDTV signal reception

The popularity of large screens and projectors makes the limitations of conventional broadcast video, especially compressed digital video, very visible unless viewed far from the screen. An HDTV compatible television set or projector does not improve the quality of the conventional TV channels. They require a different tuner to acquire entirely different signals from new signal sources, sometimes at an additional cost. These are typically
Over the air over an antenna. Most cities in the US with major network affiliates broadcast over the air in HDTV. Tuners can also be fitted to computers to receive this signal. Some televisions have a HDTV tuner built in. Monitors often lack a tuner, but a tuner is not needed for digital cable.
Cable television companies often offer HDTV broadcasts as part of digital broadcast service. HDTV will not work with an analog service. For example, if channel 4 is ABC, channel 104 might be offered in HDTV. For clearest signal, the monitor should be connected with an HDMI cable rather than composite or component cables. Some cable carriers also offer HDTV on-demand playback of free and for-fee movies and programming of commonly viewed shows.
Satellite-based TV companies, such as Optimum, DirecTV and Dish Network, offer HDTV to customers as an upgrade. New satellite receiver boxes and a new satellite dish are often required to receive HD content.
Video game systems, such as the Xbox (NTSC only), Xbox 360 and Playstation 3, can output at an HD resolution.
Two optical disc standards, Blu-ray and HD DVD, can provide HDTV signal.

High-definition television

High-definition television
From Wikipedia, the free encyclopedia

Projection screen in a home theater, displaying a high-definition television image.

Projection screen in a home theater, displaying a high-definition television image.
High-definition television (HDTV) is a digital television broadcasting system with a significantly higher resolution than traditional formats (NTSC, SECAM, PAL). While some early analog HDTV formats were broadcast in Europe and Japan, HDTV is usually broadcast digitally, because digital television (DTV) broadcasting requires much less bandwidth. HDTV technology was first introduced in the US during the 1990s by a group of electronics companies called the Digital HDTV Grand Alliance.[1][2]
In the early 2000s, a number of high-definition television standards were competing for the still-developing niche markets. Current HDTV standards are defined by the International Telecommunication Union (ITU-R BT.709) as 1080 active interlace or progressive scan lines, or 720 progressive scan lines, using a 16:9 aspect ratio. HDTV is also capable of "theater-quality" audio because it uses the Dolby Digital (AC-3) format to support "5.1" surround sound. It should be noted that while HDTV is more like a theater in quality than conventional television, 35mm and 70mm film projectors used in theaters still have the highest resolution and best viewing quality on very large screens. Many HDTV programs are produced from movies on film as well as content shot in HD video.
The term "high-definition" can refer to the resolution specifications themselves, or more loosely to media capable of similar sharpness, such as photographic film. As of 2007, 24 million US households have HDTVs. However, only half are set up to actually receive HDTV programming[3] as some consumers are not aware that they must get special receivers to get HDTV from cable, or use HDTV tuners to receive over-the-air broadcasts, and some are planning to use it in the future.