Finding Answers to Questions

Understanding TV Terms

What are analog TV, digital TV, and high-definition TV (HDTV)?

Devices such as monitors, tuners, and integrated monitor/tuner combinations are designed to handle any of the 18 formats officially sanctioned by the industry-led standard setting, Advanced Television Systems Committee (ATSC), for the digital transmission of video signals. There are three subgroups of

digital televisions depending on their capabilities: high- definition (HDTV), enhanced-definition (EDTV), and standard-definition (SDTV).

In contrast, U.S. analog television has been available for over 50 years in the single National Television Standards Committee (NTSC) format. This is the signal format that has been broadcast over the air and through cable systems. NTSC television offers slightly more than 480 interlaced lines of resolution.

To high-definition programming, your TV must receive high-definition signals by means of a high-definition signal source connected to the television. The source can be an off-the-air high-definition antenna or cable HD signal, or a HD source, such as a cable or satellite provider HD set-top box, a HD-DVD player, and so on. All sources except a HD antenna or cable HD signal, must connect to one of the High Definition Input connector sets on the rear pf the TV. Your cable or satellite provider may require additional purchase for high-definition programming; off-the-air high-definition broadcasts may not be available in all areas.

What is the difference between progressive and interlaced signal formats for digital TVs?

There are 18 standard digital TV signal formats. Each provides a different picture quality. The names of these digital TV formats consist of a number followed by either p (progressive) or i (interlaced). The letter refers to the way the TV uses the signals to create the picture:

■Progressive (p) scanning presents all the horizontal lines of the picture in one frame. This provides a sharper picture to the eye, and looks much better than an interlaced image of the same resolution.

■Interlaced (i) means that the picture appears in two segments; every other horizontal line of the picture is displayed in one frame, and the other half of the horizontal lines are displayed in the next frame.

This works because it happens so fast that the eye is deceived into believing that only one picture is being shown.

The number in the names of the formats refers to the number of lines of resolution. Generally speaking, the higher the number, the better the picture. For example, with digital TV (DTV), there are two progressive formats for broadcasters to choose from: 480p and 720p. 480p has 480 horizontal scan lines. Although the 480p image is much sharper than a regular TV broadcast, it is considered only a DTV signal and not a true high-definition signal. 720p has 720 horizontal scan lines and is considered to be true HDTV. 720p can rival a 1080i picture, in which 1080 horizontal scan lines are displayed as an interlaced image. The sharper and more accurate (progressive) 720p picture looks better, even though a 1080i picture has many more scan lines and a much higher resolution.

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