What is DTV Technology - The Full Story

www.ercservice.com Express Repair Center

What is DTV Technology?
The Full Story

DTV represents the most profound change in the history of Television since the addition of color in 1951. Here we will tell you all about this new development, and how it will change the way you see television. We also include some background on the dramatic and always colorful history of the television standard, and of course the ways that Samsung specifically contributed to this revolution in home entertainment. So click back, relax and let's talk TV . . .

Evolution of Digital Television

fcc advanced television systems committee In late 1996 the Federal Communications Commission (FCC) recommended a new digital television (DTV) system, proposed by the Advanced Television Systems Committee (ATSC), and Congress decided that by 2006, all television programs would be broadcast in DTV. DTV is an umbrella term that refers to both the high-profile High Definition Television (HDTV) we've all been hearing so much about recently and Standard Definition Television (SDTV), also a digital system, but one that displays an image that is somewhat less detailed.

How did all this get started? In the mid-1980s, the FCC had been approached by consumer electronics manufacturers, who had realized the potential of "advanced television" and wanted the FCC's approval of a standard so they could begin developing and marketing products. The ATSC was an offshoot of earlier bodies set up by the FCC charged to develop a DTV standard. (For more detailed information about the ATSC, click on the "ATSC" logo above.)

What's so special about DTV? Quite a lot. For example, because DTV is transmitted as bits of data, instead of analog signals like current NTSC television, digital television doesn't face the problems that often plague analog signals, such as ghosts, snow, or color distortions. With DTV you get more detailed pictures, richer colors, and clearer images. In short, the picture on the screen is always near "picture perfect," if it is received. Why the "if"? That's because of a characteristic of digital transmission, called the "cliff effect." Unlike analog transmissions, which roll along, getting progressively weaker, digital signals forge ahead to the end of the transmission range at the same quality, but then just stop, as though they've fallen off a cliff.

Picture in Picture Display (PIP) DTV's potential is truly exciting. For example, while watching a live musical performance, a viewer could decide which musician to zero in on, or while watching a home improvement or news program, bring up on screen additional diagrams and information. And if you wanted to get a printout of something on the screen, adding a printer could make that happen. Much of that's for the future, though. Here's what we have now.

HDTV is the "the top of the line" as far as TV systems go, with almost three-dimensional images and movie theater quality sound. HDTVs have, at minimum, resolution of 1280 x 720 pixels (picture elements, or dots) progressive (p) or 1920 x 1080 pixels interlaced (i) or higher, and an aspect ratio of 16:9 (more like a movie screen). For more on "progressive scanning" and "interlaced scanning", see the following illustrations below. HDTV is transmitted as bits of data (18.4 Mbps) on a single channel and takes up the entire channel in the same amount of bandwidth as current analog systems use (6 megaherz). HDTV, as currently defined, is a picture made up of more than one million pixels, according to the Consumer Electronics Association (CEA). Today's TVs are generally one-quarter narrower (4:3 or 12:9 aspect ratio), and their screen image is made up of 525 lines that are scanned horizontally, with effective resolution of 640 x 480i. HDTV sets also receive and reproduce Dolby Digital sound (six channels) instead of NTSC's two plus a second audio program (SAP).

SDTV is also digital, but its display resolution is either 640 x 480 or 704 x 480 so the picture it displays isn't as detailed as that of HDTV (i.e., it uses fewer bits), but it is free from ghosts or snow. Because SDTV doesn't use as many bits, transmitting in SDTV allows a broadcaster to send about four channels in the same bandwidth that one HDTV channel takes up. An SDTV set could have either a 16:9 or a 4:3 aspect ratio, and it may not reproduce Dolby Digital sound.

interlaced vs. progressive scanning The number of DTV formats is usually stated as 18 (actually there are more, but we don't need to consider them now). Six of the 18 formats are used for HDTV and 12 are used for SDTV. These can be either "progressive" (the image is scanned onto the screen in horizontal lines that are added consecutively) or "interlaced" (the odd-numbered horizontal lines are scanned onto the screen first and then the even-numbered lines are scanned). Interlaced formats (an early form of compression) were developed when TVs first came out in the 1930's, because early TVs couldn't work fast enough to "paint" pictures on the screen in a progressive way.

Currently, there are nearly 250 million television sets in the United States. You don't have to worry that the move to digital TV will make all of these sets obsolete, because converter boxes will allow consumers to display digital programming on their current analog TVs. So, people who want to receive digital TV, but aren't quite ready to make a big cash outlay for a new TV set will be able to receive programs that are broadcast in digital form on their current analog television set by plugging their TV set into a set-top box. However, since their TV was designed for NTSC quality, the images that will be displayed on their screen won't have all of the rich detail and color, but they will be free of snow and other distortions of analog transmissions. It is important to recognize that there is a difference between "detail" and "sharpness," which refer to two different aspects of the image viewed on the TV screen.

According to Consumer Electronics Association numbers as of January 2000, since the first DTV sets appeared in retail outlets in 1998, factory sales of DTV products to dealers have totalled approximately 100,000 units. These sales include TV sets capable of displaying HDTV, a much larger number of "HDTV-ready" displays (high-scan monitors that require external DTV tuner/ decoders to receive HDTV and SDTV signals), set-top boxes, and other products. About a dozen manufacturers are (or will be) offering fully integrated 1080i DTV sets (with the digital decoder included); a dozen are (or will be) offering DTV set-top decoders; and about 21 are (or will be) offering 1080i- and/or 720p-capable monitors which require an external DTV decoder.

To receive DTV signals consumers may need a new antenna, depending on where they are located in relation to the broadcast antenna. But, getting the right antenna for your location won't be a problem, because retailers will be offering antennas that are color coded to match colors on a map of your neighborhood that marks specific transmitters, the areas they serve, and the color/grade of antenna required to receive the DTV signals from your location. CEA has introduced the TV Antenna Selector Map Program to help consumers select the correct antenna. You can install the antenna yourself, or have it installed professionally. As with analog television, the over-the- air signal may be subject to interference in certain areas.

Consumers will, of course, want more digital TV programming available to make it worthwhile for them to upgrade their analog TVs. There will be a slow rollout of programming originating in DTV to meet this demand, and the landscape is continually changing. In the meantime, many TV stations are choosing to produce analog material that can be "upconverted" to one of the many DTV formats. Some networks, though, are creating and transmitting true DTV programs. For example, according to the CEA's count as of January 2000, in some markets CBS was presenting its NFL games, as well as some movies, in DTV; NBC was transmitting The Late Show with Jay Leno in DTV; and PBS was broadcasting various specials in DTV. More broadcast DTV programs are coming, but it's also important that cable and satellite programs be transmitted in digital form. Consumers don't want to give up the wealth of programming they now get through cable and satellite.

Some cable and satellite providers are offering ATSC HDTV programming in addition to analog programs, and more is expected. However, other cable companies are arguing in favor of changing the current ATSC requirement to one that is incompatible with the ATSC DTV system because this would allow them to squeeze more programs onto the cable system. Their solution would require two set-top boxes; the second set-top box would be required to convert the cable signal into something that the first set-top box could understand.

You may hear the terms "8-VSB" and "32-QAM" kicked around in this argument. The mathematics required to explain the differences between those two encoding schemes is very complex, so we won't bore you with the details. But you may want to remember the names so you can keep track of the players. And at times, you may hear other acronyms like "DVB" tossed in to muddy the waters even more. It took eleven years to arrive at the ATSC system that Congress approved. It would be a shame if the industry had to go through another lengthy process like this. The FCC and TV set manufacturers are strongly resisting these efforts because they would create chaos out of an already complex changeover.

Four technical solutions are available to allow consumers to link cable and satellite boxes to their digital television receivers: the 1394 interface ("Firewire" or "iLink"), the RF remodulator interface, a component video interface, and the National Renewable Security Standard (NRSS) interface. The consumer electronics industry is working with the FCC to ensure that the cable industry lives up to its obligation to carry HDTV programming.

Consumers don't have to worry about being left out in the cold after 2006 if they haven't bought a DTV set by then. At least for the time being, most DTV sets will accept both analog and DTV signals, because there isn't a lot of digital programming out there yet. Most set-top boxes receive only the DTV signals and leave the analog reception to the tuner built into the TV.

Current HDTVs will eventually be able to receive digital cable broadcasts through a set-top box, which consumers will be able to buy from their local retailers. There is even talk about eventually building cable interfaces directly into DTV sets, but that will have to wait until all the parties are working on the same page. As digital broadcasting technology gets even better and as more programming becomes available, more "conversion" products will become available. As time goes on and more DTV programming becomes available and less NTSC analog programming is broadcast, analog tuners in DTV sets will disappear. But, not to worry. That won't be for a while. Even though analog TV signals are supposed to stop being transmitted in 2006, that date is a target and not carved in stone. Few people in the consumer electronics industry believe that enough consumers will have bought DTVs in the next few years to actually allow analog programming to be stopped in 2006. In fact, federal legislation enacted in 1997 allows for continuation of analog signals in markets where penetration of digital TVs is less than 85 percent.

How Does It Work?

DTV is an umbrella term that refers to both the high-profile High Definition Television (HDTV) we've all been hearing so much about recently and Standard Definition Television (SDTV), also a digital system, but one that displays an image that is somewhat less detailed.

big screen tv and flat screen displays What's so special about DTV? Quite a lot. For example, because DTV is transmitted as bits of data, instead of analog signals like current NTSC television, digital television doesn't face the problems that often plague analog signals, such as ghosts, snow, or color distortions. With DTV you get more detailed pictures, richer colors, and clearer images.

In short, the picture on the screen is always near "picture perfect," if it is received. Why the "if"? That's because of a characteristic of digital transmission, called the "cliff effect." Unlike analog transmissions, which roll along, getting progressively weaker, digital signals forge ahead to the end of their transmission range at the same quality, but then just suddenly stop, as though they've fallen off a cliff. That means you won't get any image because your antenna is too far away from the transmitter.

big screen tv hdtv DTV's potential is truly exciting. For example, while watching a live musical performance, a viewer could decide which musician to zero in on, or while watchinhing a home improvement or news program, bring up on screen additional diagrams and information. And if you wanted to get a printout of something on the screen, adding a printer could make that happen. Much of that's for the future, though. Here's what we have now. The number of DTV formats is usually stated as 18. Six of the 18 formats are used for HDTV and 12 are used for SDTV. These can be scanned either "progressive" or "interlaced."

HDTV is the "the top of the line" as far as TV systems go, with almost three-dimensional images and movie theater quality sound. HDTVs have, at minimum, resolution of 1280 x 720 pixels (picture elements, or dots) progressive (p) or 1920 x 1080 pixels interlaced (i), both with an aspect ratio of 16:9--more like a movie screen. That 1920 x 1080 format has three times as much horizontal resolution and slightly over twice as much vertical resolution as a standard analog NTSC picture. That is over six times as much picture information as NTSC.

HDTV is transmitted as bits of data up to (18.4 Mbps) on a single channel and takes up the entire channel. It takes up the same amount of bandwidth as current analog NTSC systems use ,6 megaherz. HDTV, as currently defined by the Consumer Electronics Association (CEA), is a picture made up of more than one million pixels. Today's TVs are generally one-quarter narrower (4:3 or 12:9 aspect ratio), and their screen image is made up of 525 lines that are scanned horizontally, with effective resolution of 640 x 480 pixels. HDTV sets also receive and reproduce Dolby Digital sound (six channels) instead of NTSC's two plus a second audio program (SAP).

SDTV is also digital, but its display resolution can be either 640 x 480 or 704 x 480 with either interlaced or progressive scanning so the picture it displays isn't as detailed as that of HDTV (i.e., it uses fewer bits), but it is free from ghosts or snow. Because SDTV doesn't use as many bits, transmitting in SDTV allows a broadcaster to send about four channels in the same bandwidth that one HDTV channel takes up. An SDTV set could have either a 16:9 or a 4:3 aspect ratio, and it may not reproduce Dolby Digital sound.

Currently, there are nearly 250 million NTSC television sets in the United States. You don't have to worry that the move to digital TV will make all of these sets obsolete, because converter boxes will allow consumers to display digital programming on their current analog TVs. So, people who want to receive digital TV, but aren't quite ready to make a big cash outlay for a new TV set will be able to receive programs that are broadcast in digital form on their current analog television set by plugging their TV set into a set-top box. However, since those TVs were designed for NTSC quality, the images that will be displayed on their screen won't have all of the rich detail and color, but the DTV signals will be free of snow and other distortions of analog transmissions. It is important to recognize that there is a difference between "detail" and "sharpness," which refer to two different aspects of the image viewed on the TV screen.

Digital Television (General Background)

In late 1996 the Federal Communications Commission (FCC) recommended a new digital television (DTV) system, proposed by the Advanced Television Systems Committee (ATSC), and Congress decided that by 2006, all television programs would be broadcast in DTV.

How did all this get started? In the mid-1980s, the FCC had been approached by consumer electronics manufacturers, who had realized the potential of "advanced television" and wanted the FCC's approval of a standard so they could begin developing and marketing products. The ATSC was an offshoot of earlier bodies set up by the FCC charged to develop a DTV standard.

According to Consumer Electronics Association numbers as of January 2000, since the first DTV sets appeared in retail outlets in 1998, factory sales of DTV products to dealers have totaled approximately 100,000 units. These sales include TV sets capable of displaying HDTV, a much larger number of "HDTV-ready" displays (high-scan monitors that require external DTV tuner/decoders to receive HDTV and SDTV signals), set-top boxes, and other products. About a dozen manufacturers are (or will be) offering fully integrated 1080i DTV sets (with the digital decoder included); a dozen are (or will be) offering DTV set-top decoders; and about 21 are (or will be) offering 1080i- and/or 720p-capable monitors which require an external DTV decoder.

NBC abc FOX CBS PBS Consumers will, of course, want more digital TV programming available to make it worthwhile for them to upgrade their analog TVs. There will be a slow rollout of programming originating in DTV to meet this demand, and the landscape is continually changing. In the meantime, many TV stations are choosing to produce analog material that can be "unconverted" to one of the many DTV formats. Some networks, though, are creating and transmitting true DTV programs. For example, according to the CEA's count as of January 2000, in some markets CBS was presenting its NFL games, as well as some movies, in DTV; NBC was transmitting The Late Show with Jay Leno in DTV, and PBS was broadcasting various specials in DTV. More broadcast DTV programs are coming, but it's also important that cable and satellite programs be transmitted in digital form. Consumers don't want to give up the wealth of programming they now get through cable and satellite.

Some cable and satellite providers are offering ATSC HDTV programming in addition to analog programs, and more is expected. However, other cable companies are arguing in favor of changing the current ATSC requirement to one that is incompatible with the ATSC DTV system because this would allow them to squeeze more programs onto the cable system. Their solution would require two set-top boxes; the second set-top box would be required to convert the cable signal into something that the first set-top box could understand.

What do I need to see Digital Television?

what do i need to see DTV? You can receive a DTV signal via Cable, Satellite or TV Antenna. With Cable and Satellite, you simply run a wire from your cable box or satellite receiver to your DTV's set-top box or straight into your DTV if it is an intergrated unit. To receive DTV signals via a TV antenna, you may need a new antenna depending on where you are located in relation to the broadcast antenna. Getting the right antenna for your location shouldn't be a problem because retailers will be offering antennas that are color coded to match colors on a map of your neighborhood that marks specific transmitters, the areas they serve, and the color/grade of antenna required to receive the DTV signals from your location.

DTV Antenna Program?

The Consumer Electronics Association, an industry group, has introduced the TV Antenna Selector Map Program to help consumers select the correct antenna. You can install the antenna yourself, or have it installed professionally. As with analog television, the over-the-air signal may be subject to interference in certain areas. As we noted in the "How does DTV work?" section, with digital reception there is what is called "the cliff effect." You'll get great reception of particular incoming signals, or none at all as if the signal fell off a cliff. Moving the antenna to another spot even a few feet away might allow you to receive that signal you couldn't receive with the antenna in the first position. Positioning antennas, now almost a lost art, will have to be rediscovered.

We would like to express our appreciation for the preceding information provided by Samsung Electronics.