Digital TV, also called DTV, is the method of broadcasting TV signals using digital technology. Until recently, all TV signals were broadcast using analog technology that has existed for over 50 years. Digital TV is just a new and better way to get the same TV programming to your home. Additionally, DTV provides new capabilities for TV programming, such as High Definition TV (HDTV), a program guide, datacasting, and multicasting.
How is Digital TV different than regular TV?
Digital television is the same regular TV programming and the same broadcast stations that have been available for free. With new technology, that programming is now delivered over-the-air using a digital signal. The digital signal assures that the picture and sound will be crystal clear. In addition, High Definition TV can be carried on DTV transmissions. HDTV offers a much higher resolution picture and sound than standard or conventional television broadcasts, but requires an HDTV-capable display to see its full potential.
What is HDTV?
High Definition TV can be carried on digital TV transmissions. HDTV offers a much higher resolution picture and sound than standard or conventional television broadcasts. HDTV picture resolution is even better than DVD's with the same high-quality digital sound as DVD's. HDTV programming is also "widescreen."
How are HDTV and DTV related?
Digital TV is not HDTV. Digital TV or DTV is a transmission method - sending television over the airwaves digitally. HDTV can only be seen or carried on DTV transmissions. So, DTV is necessary for the existence of HDTV, but HDTV need not exist for DTV to exist
Do all networks use the same resolutions or HDTV format?
No. The Digital TV guidelines (called ATSC standards) allow for many DTV broadcasting formats or resolutions. Two of these are considered true High Definition: 720p and 1080i. Both of these formats use the widescreen 16:9 aspect ratio compared with TV's old/usual 4:3 aspect ratio. Currently, ABC broadcasts its HDTV programs in 720p, while NBC, CBS. UPN and WB use 1080i. The premium channels on Dish Network and DirecTV, such as HBO-HD and Showtime HD, use 1080i. The Fox network currently does not broadcast true High Definition. Instead, Fox broadcasts an "enhanced" or "extended" definition format, 480p widescreen. This flavor of DTV has a 16:9 (widescreen) aspect ratio, but a lower resolution than true High Definition.
Do I need to be concerned with the resolution or HDTV format being broadcast?
In most cases, no. Your DTV tuner or set-top-box will interpret whatever HDTV or DTV format is being sent and convert it for display on your television. Many DTV tuners output only 1080i (and many HDTV sets only accept 1080i). In these cases, the tuner converts another format, such as 720p or 480p to 1080i.
What does 720p or 1080i mean?
These are HDTV formats or resolutions. The "720" and "1080" refer to the number of horizontal scan lines per frame. A frame is one screen that is draw at a time. Usually, there are 30 frames per second drawn to your television screen. The "i" and the "p" refer to how frames are handled. With "i", the frames are interlaced. That is, half of the lines are drawn each frame in an interlaced or "every-other-line" fashion. The progressive format, "p", draws all of the lines in every frame. So, 1080i draws 540 new lines in each frame, interlacing them. The 720p format draws 720 new lines in each frame. For comparisons, most DVD players output 480i, while "progressive scan" DVD players output 480p.
Interlace vs. Progressive
Televisions create a picture by tracing, or scanning the screen in horizontal lines, from left to right, from the top of the screen to the bottom. Interlace means that the TV scans half the screen, just the odd-numbered lines, in the first 60th of a second, and the even lines in the next 60th of a second. Progressive Televisions scan the entire screen every 60th of a second. Interlace was a necessary compromise in the early days of TV. Televisions then had no memory, so the CRT vertical scanning rate had to match the transmitted frame rate (or field rate). It would have taken too much radio spectrum to transmit a progressive picture with a high enough frame rate while keeping the resolution high. Interlace allows you to keep the frame rate high while not sacrificing the resolution too much and meet bandwidth constraints. Digital electronics and memories make progressive TV practical. All computer monitors scan progressively. Non-CRT display technologies such as LCD, plasma, and DLP are inherently progressive. Interlace scanning artifacts are always present in an interlace picture, and they become objectionable on very large displays. Interlace pictures are also harder to manipulate (pause, scaling, slow motion). Interlace scanning means that a 1920 x 1080i picture doesn't really have twice the resolution of a 1280 x 720p picture (as you might think by comparing the number of pixels). To compare resolution directly, multiply the number of pixels in an interlaced display by a factor between 0.5 and 0.7. 1080i is still higher resolution than 720p, but the difference will not be pronounced on typical HDTV’s. On somewhat large HDTVs, 720p may look better because it doesn't have interlacing artifacts.
Is Digital TV the same as DirecTV, Dish Network, and Digital Cable?
Do not confuse Digital TV with digital cable or digital satellite. While these systems do use digital technology, they are not using the same digital signal technology that your local stations use and that this site discusses.
I have a digital television, do I get Digital TV?
Many televisions are labeled "digital," but do not tune or receive DTV broadcasts. To view Digital TV transmissions, your TV must have 1) a DTV tuner built-in, or 2) an external DTV tuner box connected to the TV.
I have digital cable, do I get Digital TV?
Do not confuse Digital TV with digital cable or digital satellite. While these systems do use digital technology, they are not using the same digital signal technology that your local stations use and that this site discusses.
I have an HDTV-ready television, do I get Digital TV?
Unless your television has a built-in Digital TV tuner, you cannot receive DTV unless you connect your television to a DTV tuner.
How do I receive Digital TV telecasts?
To receive DTV, you need a DTV tuner. DTV tuners, commonly called "Set Top Boxes" or STBs, are separate units that sit on top of the television set and plug into external jacks on the TV. These STBs are generally the size of a typical VCR and are designed to connect to the television display in much the same way as a VCR or DVD unit.
Do I need an antenna?
Yes. To receive DTV for free over-the-air, you need an antenna. The size or type of the antenna will depend on how far you live from the transmitter towers and how clear your line-of-site is to the towers.
What kind of antenna do I need?
This depends. There is no single antenna that will work for everyone in the mid-south. First, you will need an antenna capable of tuning both VHF and UHF stations. This includes most conventional antennas. In other parts of the country, Digital TV stations might only be on UHF stations. In the mid-south however, Digital TV is on both VHF and UHF. Most viewers in the mid-south have found that "omni-directional" antennas do not work very well, including antennas labeled or marketed as "digital." There is nothing special about digital signals - regular TV antennas that work for analog TV will also work for Digital TV.
Is reception of DTV better than cable TV?
The picture quality is generally superior to analog cable TV and even digital cable TV. With the proper antenna, DTV is as close to "perfect reception" as possible.
Is DTV reception better than analog reception?
Yes. When the digital signal is received, the picture is identical to what the station sends out - no ghosting, snow, or color blurring or fading. Because the signal is over-the-air, there can be reception problems, such as signal dropouts. Most reception problems can be addressed with a suitable antenna setup.
Do I have to mount my antenna on my roof?
Not necessarily. Many viewers in the mid-south have antennas inside the house. Although outdoor mounting, such as on a roof, theoretically provides stronger or better reception, many viewers have found that mounting an antenna in the attic works fine. Outdoor antennas can be mounted indoors, size and space permitting. Whether it is necessary to mount the antenna outside will depend on several factors including distance from the transmitting towers and the construction of the house. If you are located far from the WPTY-DT or WLMT-DT’s transmitter, then an outdoor antenna might be necessary.
How much does Digital TV cost?
Nothing! This is part of the beauty of DTV. It is free! DTV is just the digital equivalent of broadcast television. It is being sent out over the airwaves from the same broadcast stations that have been around for a long time. The only thing new is the technology used to send the broadcast signal. So, network programming (such as NBC, UPN, WB ABC, CBS, and Fox) is available for free.
How much does HDTV cost?
Nothing! Just like with DTV, this is part of the beauty of HDTV. It is free! It is being sent out over the airwaves from the same broadcast stations on the DTV transmission. So, HDTV network programming (such as NBC, ABC, CBS, and Fox) is available for free.
What other sources of HDTV are available?
Besides over-the-air broadcasts, HDTV programming is available from satellite services, such as DirecTV and Dish Network. Dish Network offers HBO-HD, Showtime HD, and a pay-per-view HDTV channel. DirecTV currently offers HBO-HD and HDNet (an all HDTV network that features sports, documentaries, and various other HDTV programming). Of course, you must pay to subscribe to DirecTV's or Dish Network's programming packages, in addition to having a small satellite dish and a compatible tuner. Dish Network sells a DTV tuner that will also tune free over-the-air DTV signals. Many DTV tuners, such as those from Hughes, Mitsubishi, Panasonic, RCA, Sony, and Toshiba also include DirecTV tuners.
Can I record DTV on a VCR?
Yes. However, you currently cannot record the full resolution of DTV broadcasts, including HDTV. A DTV tuner can be connected to your VCR so that you can record programming received from the Digital TV transmission. Several manufacturers have announced new HDTV VCRs, but they are currently quite expensive. Also, some computer-based DTV tuners have recording capability.
Do I need a new television to watch Digital TV?
No. Remember, DTV is a way of broadcasting television signals. Your television connected to a DTV tuner will show a near-perfect picture thanks to the digital signal. However, you must have a Digital TV tuner to receive the DTV broadcast signals. Digital television can be displayed on any television, although some DTV tuners may not provide outputs that are compatible with some televisions. For any given content displayed on any given television, a DTV tuner provides the highest possible quality picture.
Do I need a new television to watch HDTV?
To see the full resolution of HDTV, you need an HDTV-capable or HDTV-ready television in addition to a DTV tuner. Some HDTV televisions have a built-in DTV tuner, but many are just ready to be connected to a DTV tuner. A DTV tuner will still tune HDTV programming and output it to regular televisions. However, the HDTV program will be "down-converted" to your television's lower resolution. On non-HDTV televisions, the HDTV programming will not appear in its full resolution. Instead, it will look similar to the picture you get from a DVD. In some cases, this will still look better than regular television programming. Also, HDTV programming is in the 16x9 widescreen format. Most HDTV televisions have 16:9 dimensions compared to regular TV's 4:3 dimensions.
What is datacasting?
An additional possibility with data being sent via DTV is something called "datacasting." Stations can broadcast news, weather, sports scores, stock prices, consumer information, etc. to appear on your TV. Datacasts will "piggyback" on the DTV television signal.
What is multicasting?
Digital TV allows stations to broadcast multiple programs on one channel. Each digital channel can potentially hold six "sub-channels." Broadcasters can use this capability of DTV to broadcast multiple programs at the same time. For example, one station could re-broadcast its local newscast on a sub-channel during primetime while it shows the regular network programming on another sub-channel. Currently WPTY-DT and WLMT-DT does not provide any multi-casting services.
What is a program guide?
One use of data in the DTV signal is a program guide, also called "PSIP". Similar to the program guides used in cable TV or satellite systems, this guide provides program times, information, and ratings. Currently, only basic channel information is available on WPTY-DT 24 and WLMT-DT 30. Your DTV tuner will receive and display this information for free.
What to Expect in the Future
More digital broadcasters - all over-the-air broadcast television stations are required to be digital by the end of 2003.
More digital and HD programming.
Lower-cost DTV decoders. Prices should fall to $200 within a few years.
Better receivers. Current receivers have problems with multipath interference.
Enhancements to 8VSB/ATSC. When broadcasters and receivers both take advantage of enhancements, reception is easier.
Lower-cost and higher-quality HDTVs. It will be several years before we see HDTVs that are capable of displaying all of the picture information in an HD transmission.
New DTV signal sources - satellite, cable, and consumer formats such as tape and DVD
Where can I see a demonstration of DTV or HDTV?
Most local electronics retailers have set up displays of DTV and HDTV.
*some material provided courtesy of AtlantaDTV.org
