HP (Hewlett-Packard) CHPTOH-0711 ユーザーズマニュアル

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 setter, 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).

By 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 view 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 an HD 
source such as a cable or satellite provider HD set-top 
box, an HD-DVD player, and so on. All sources, except 
an HD antenna or cable HD signal, must connect to 
one of the High Definition Input connector sets on the 
rear of 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.

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.