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Finding answers to questions, Understanding tv terms, Terlaced signal formats for digital tvs – HP LT4200 42 inch Professional LCD HDTV User Manual

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Finding Answers to Questions

45

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.