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All About Digital TV — DTV and HDTV

In the world of television entertainment, everyone's talking HDTV (high-definition television). HDTV offers consumers much higher resolution and better picture color and clarity when compared to standard analog televisions.  Analog televisions which use CRT technology have been around for many years now. A standard television is able to broadcast 480 lines of pixels. Each line takes 1/60 of a second to draw. The line drawing is done by having the odd lines drawn first followed by the even lines, which is commonly called interlaced scanning.

Until recently, consumers wanting large-screen televisions had to rely on CRT technology. Now large screen televisions are available that use digital display technology. Instead of relying on interlacing, digital displays create their images using a fixed grid of tiny, individually controlled pixels and offers 720 lines of pixels up to 1080 and uses progressive scanning where the entire picture moves at one time every 1/60 of a second.

Digital Television (DTV)
Short for Digital Television, DTV is a digital television standard that will replace analog (or NTSC analog) television. Digital television will allow broadcasters to offer better picture quality over current transmissions, and movie-quality transmissions with HDTV. DTV also allows broadcasters to offer multiple TV programs at the same time with better picture quality and sound.

 

Key Terms To Understanding Digital Television

analog television
Preceding digital television (DTV) all televisions encoded pictures as an analog signal by varying signal voltage and radio frequencies.

DTV
Short for Digital Television, it is a digital television standard that is fast replacing analog (or NTSC analog) television.

HDTV
Short for High-Definition Television, HDTV is a standard for digital TV where the broadcast transmits widescreen pictures with more detail and quality than found in a standard analog television.

While many use the terms Digital Television (DTV) and High-definition Television (HDTV) interchangeably, they are, in fact, two very different things. DTV refers to the actual TV signal being transmitted digitally (instead of as an analog signal). DTV offers several broadcast options, which two are considered to be HDTV formats.

  • 480i:  The digital version of current television signals.

  • 480p: Enhanced Definition Television (EDTV) provides a sharper image and looks closer to HDTV than regular television. Today all DVDs can be played on EDTV.

  • 720p: a HDTV format that provides an image close in quality to 1080i, but allows 480p signals to be broadcast as well.

  • 1080i: the most detailed HDTV image available from broadcast TV

* The numbers above represent the vertical resolution, while the letters represent interlaces (i)or progressive (p) scan. For example, 1080i represents 1080 vertical resolution, interlaced scanning.

In addition to offering a higher resolution, DTV also offers a higher television aspect ratio when compared to analog. Television aspect ratio compares the the screens width to its height. Traditional televisions offer a 4x3 aspect ratio. A standard 32-inch screen would be 25 1/2 inches wide and 19 inches tall. DTV allows for widescreen aspect ratio, which is measured as 16x9. A 32-inch widescreen would be 28 inches wide and 19 inches tall, allowing viewers to see a much bigger image area.

A U.S. Senate panel has set an April 7, 2009, as the deadline for television stations to switch entirely from analog to digital broadcasts. Analog televisions will work until all analog broadcasting ceases. Once the transition to complete DTV has taken place, older types of televisions will need a converter to receive DTV signals. Current televisions will continue to work with cable, satellite, VCRs and DVD players for many years.

EDTV and SDTV
Standard Definition Television (SDTV) is a type of digital television that is able to transmit and produce images that are of a higher quality than standard analog broadcast. SDTV is typically a 480i signal (where 480 represents the vertical resolution and i represents interlaced scanning). Digital cable and digital satellite programming is widely available in SDTV format. While SDTV doesn't approach the quality of HDTV, it's superior when compared to conventional television.

EDTV, or Enhanced Definition Television can also be transmitted by DTV, and visually, it simulates HDTV viewing quality. EDTV operates as 480p (where 480 represents the vertical resolution and p represents progressive scanning). To take advantage of the 480p standard, you must use a video source that outputs that signal (e.g., a DVD player) and the display must be able to read the 480p input signal. EDTV also offers the benefits of Dolby digital surround sound. 

Both SDTV and EDTV can be viewed in widescreen format.

EDTV is a major advancement in television. While HDTV is still seen, right now, as an emerging technology, EDTV is available now and can provide you with an on-screen picture that is close in quality to HDTV.

HDTV
Short for High-Definition Television, HDTV is a standard for digital TV where the broadcast transmits widescreen pictures with more detail and quality than found in a standard analog television, or digital television. HDTV is a type of Digital Television (DTV) broadcast, and is considered to be the best quality DTV format available. Types of HDTV displays include direct-view, plasma, rear screen and front screen projection. HDTV requires an HDTV tuner to view and the most detailed HDTV format is 1080i.

Types of HDTV Displays

Direct-view TV
A direct-view television is the type we are all familiar with. Direct-view televisions use a CRT an a scanning electronic gun to "paint" an image on a phosphor coated screen. Direct-view televisions are now available in analog, digital and HDTV versions.

Plasma TV
Plasma TV's create a picture from a gas (plasma) filled with xenon and neon atoms and millions of electrically charged atoms and electrons, that collide when you turn the power on. The energy the collision releases, increase the energy level in the plasma and the neon and xenon release photons of light (similar to the way neon lights work). Plasma TVs offer large viewing areas (up to 50 inches) but are very thin. While they offer excellent picture quality, they're quite expensive.

Rear Screen TV
A rear screen TV uses a projection screen in place of a CRT to display images. Rear screen TVs offer high resolution and bright colors, and newer models use high-quality screens that allow for many viewing angles.

Front Screen Projection TV
Front screen projection works like a Rear Projection TV, only Cathode Ray Tubes are built into a separate unit that projects the image onto the front of the TV screen. The screen and projector are separate so the viewing size is mainly limited to the size of your room. More expensive front screen projectors can produce a nice bright image, however they will only work in a darkened room.

HDTV or HDTV Ready?
One thing you may find confusing is that buying an HDTV will not guarantee you immediate access to HDTV programming. When purchasing a HD television, you'll have a choice between integrated HDTVs and those that are often called "HDTV-ready" or "HDTV compatible." To receive HDTV broadcast, you need an HDTV tuner — a device capable of receiving and decoding HDTV signals. HDTV tuners can be a stand-alone device or it can integrated in the HDTV display. A high-definition television or display that has the HDTV tuner built into the set is called "integrated HDTV" while "HDTV-ready" refers to a television set that does not come with an integrated HDTV tuner. An HDTV-ready set means you must purchase the tuner separately.

More Digital TV and Home Theater Related Terms
1080i
analog television
bad strobing
digital
direct-view TV
EDTV
flat-panel display
front screen projection TV
HDTV-ready
HDTV tuner
integrated HDTV
interlaced scan
NTSC
plasma TV
progressive scan
rear screen TV
SDTV
television aspect ratio

Did You Know...
A "HDTV set-top box" is another name for a high-definition tuner. It is also called a HDTV receiver or HDTV converter. A high-definition tuner is required to receive and decode HDTV signals.


Vangie 'Aurora' Beal
Writer, www.Webopedia.com
Last updated: November 11, 2005


Related Links

ATSC General FAQ
Analog television sets will continue to receive analog broadcasts at least through 2006 and possibly longer. After that, consumers will be able to hook up a set-top box to their existing TV to receive digital TV broadcast signals, but not in high-definition. Of course, current TV sets will continue to work with cable, satellite, VCRs, DVD players, and other devices for many years.

HDTV World
Everything you need to know about HDTV from C|Net.com

HDTV in Plain English
This article takes a look at where we have been with the current television system so you can see where we are going with the new technologies.

Interlaced Video
Interlaced video exploits various technical possibilities of video broadcasting, to reduce the frame rate (and therefore the transmission bandwidth)  while avoiding a frame rate that would be too slow for the eyes to to cope with (bad strobing).

How progressive scan works
Progressive scan technology is synonymous with super sharp picture quality but how does it differ from interlacing scanning and just how does it work?

Senate Approves 2009 For End of Analog TV
The Senate moved the digital TV transition one step closer to reality, setting a firm date for television broadcasters to switch to all-digital transmissions. Lawmakers gave broadcasters until April 7, 2009, to end their traditional analog transmissions. The so-called "hard date" was included in a sweeping budget bill.

Guide To DTV Standards
The ATSC Standard for Digital Television (DTV) encompasses a number of elements, documented in various Standards, Recommended Practices, and Implementation Guidelines. This resource serves as a guide to the these documents.

Home Theater Magazine
Featuring news, spotlights, product descriptions and reviews of today's Home Theater equipment.

DTV Shopper's Guide
Digital Television (DTV) is a new type of broadcasting that will transform your television viewing experience. That means better quality, more choices, and more control over your television. This articles discusses what you should know before you buy!

What to Look For in a direct-view TV
Direct-view TV is the industry label for what most people think of as a standard TV.




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