Understanding Digital Television
Standards Standard Definition: 480P, the
DVD format. 480I is shorthand for analog video; the name refers to
480 visible horizontal scanning lines interlaced in alternating
fields. 480P is a progressive-scan mode that basically doubles the
resolution of the old video, producing a better image. High-Definition: 720P and
1080I are both High-Definition formats. Some video experts contend
that the difference in picture quality between 720P and 1080I is
negligible. • 720P
could be thought of as a line-tripling scheme, and is favored by ABC
and ESPN. • 1080I
alternates fields of 540 lines each to create combined frames of
1080 lines. 1080I is used by CBS, NBC, and PBS. Stereo or
Multi-channel Sound HDTV Introduction The 480p and 480i formats are
called the SD (standard definition) formats, and 480i
is roughly equivalent to a normal (old) analog TV picture.
The 720p, 1080i and 1080p
formats are HD (high definition) formats. When you
hear "HDTV," this is what is being discussed
-- a digital signal in the 720p, 1080i or 1080p format. Digital
Signal
Analog TV broadcasts you
receive are a single, analog composite video signal and a
separate sound signal. You can get, over the air (OTA),
channels 2 thru 83 in most large cities if you live within 50
miles of the station's antenna.
Digital TV as well can be
received from local commercial digital TV stations if
you have a digital TV receiver and an antenna. The FCC gave
television broadcasters a new frequency to use for their
digital broadcasts, so right now each broadcaster has an
analog TV channel and a digital TV channel. The digital
channel carries a 19.39-megabit-per-second stream of digital
data that your digital TV receives and decodes.
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