Viewers should notice improvements in picture and sound quality, particularly in the case of high-definition (HDTV) broadcasts. (To get the full effect, you’ll need a high-definition set, and the broadcaster and, if applicable, cable or satellite provider must provide a high-definition signal.)

Digital transmissions make more efficient use of the broadcast spectrum, leaving more of the airwaves available for additional channels or interactive data services.

When analog TV broadcasts end, broadcasters will return those frequencies to the federal government. Some have been pre-allocated to public-safety uses, including communications systems for police and fire departments. The government is likely to auction off much of the rest to wireless companies and others for commercial uses.

Source: www.dtvfacts.com

SDTV is the basic level of quality display and resolution for both analog and digital. Transmission of SDTV may be in either the traditional (4:3) or widescreen (16:9) format. Digital SDTV provides pictures and sound comparable to the best available analog TV.

Enhanced Definition TV (EDTV)

EDTV is a step up from Analog Television. EDTV comes in 480p widescreen (16:9) or traditional (4:3) format and provides better picture quality than SDTV, but not as high as HDTV. EDTV picture quality has been compared to the DVD format, and for some viewers the perceived quality is nearly comparable to HDTV.

EDTV models are generally priced lower than HDTVs, and many consumers were content to sacrifice image quality when it meant saving a thousand bucks. But HDTV prices have now dropped so much that EDTV may not seem like much of a value.

High Definition TV (HDTV)

HDTV in widescreen format (16:9) has the greatest picture quality of all digital broadcast formats. Combined with digitally enhanced sound technology, HDTV sets new standards for sound and picture quality in television. There are 4 formats that can be viewed on a High Definition TV; they are 480i, 480p, 720p and 1080p. The higher the number, the higher the resolution. Although HDTV's can play all 4 formats, most experts refer to High Definition TV broadcasts as having either 720p and 1080p resolution.

High quality image resolution is the main selling point for HDTV's. All HDTV's signals are digital signals; no longer does your TV rely on analog signals for broadcasts. Most HDTV's are able to process either HDTV format (720p and 1080p).

In fact, the video signal of analog television is transmitted in AM, while the audio is transmitted in FM. Analog TV is subject to interference, such as ghosting and snow, depending on the distance and geographical location of the TV receiving the signal.

In addition, the amount of bandwidth assigned to an analog TV channel restricts the resolution and overall quality of the image. The current analog TV signal standard (in the U.S.) is referred to as NTSC. NTSC is the U.S. standard that was adopted and came into popular use after World War II. NTSC is based on a 525-line, 60 fields/30 frames-per-second at 60Hz system for transmission and display of video images. This is an interlaced system in which each frame is scanned in two fields of 262 lines, which is then combined to display a frame of video with 525 scan lines.

This system works, but one drawback is that color TV broadcasting was not part of the equation when the system was approved. The implementation of color into the NTSC format has been a weakness of the system, thus the term for NTSC became known by many professionals as “Never Twice The Same Color”. Ever notice that color quality and consistency varies quite a bit between stations?

Digital TV, or DTV, on the other hand, is transmitted as data bits of information, just as computer data is written or the way music is written on a CD. In this way, the signal is basically “on” or “off”. In other words, the intent of DTV technology is that the viewer either sees an image or nothing at all. There is no gradual signal loss as distance from the transmitter increases. If the viewer is too far from the transmitter or is in an undesirable location, there is nothing to see.

On the other hand, unlike analog TV, digital TV has been designed from the ground up to take all the main factors of the television signal into consideration: B/W, color, and audio and can be transmitted as an interlaced (lines scanned in alternate fields) or progressive (lines scanned in linear sequence) signal. As a result, there is greater integrity and flexibility of signal content.

In addition, since the DTV signal is made up of “bits”, the same bandwidth size that takes up a current analog TV signal, can accommodate not only a higher quality image in digital form, but the extra space not used for the TV signal can be used for additional video, audio, and text signals.

In other words, broadcasters can supply more features, such as surround sound, multiple language audio, text services, and more in the same space now occupied by a standard analog TV signal. However, there is one more advantage to the ability of a Digital TV channel's space; the ability to transmit a High Definition (HDTV) signal.

Lastly, another difference between Digital TV and Analog TV is the ability to broadcast programming in a true widescreen (16×9) format. The shape of the picture more closely resembles the shape of a movie screen, which enables the viewer to see the movie as the filmmaker intended. In Sports, you can get more of the action in one camera shot, such as viewing the entire length of a football field without making look like it is a long distance away from the camera.

A 16×9 TV can display widescreen images without a large amount of picture space taken up by black bars on the top and bottom of a widescreen image, which is what you see if such images are shown on a standard TV. Even non-HDTV sources, such as DVD can also take advantage of a 16×9 TV.

Source: www.about.com

In comparison, analog television produces a total of about 210,000 pixels. Broadcasters and cable providers can choose which format of DTV they transmit, and most DTV's and new HDTV set-top boxes will be able to receive the signal regardless of which format is transmitted. Note, however, that your standard analog TV set will not be able to receive DTV signals (neither HDTVnor SDTV).

If you have an analog television, you will have to purchase a digital-to-analog set-top converter box to attach to your TV set to be able to view over-the-air digital programming.

Source: www.fcc.gov