Scientific Atlanta Explorer 3270HD User Manual page 10

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Are Local TV Stations Broadcasting in HDTV?
Aspect Ratio? Resolution? What Does All That Mean?
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Many local stations are transmitting digital
signals. However, transmitting a digital
signal does not mean transmitting an
HDTV signal. Some stations are using the
new bandwidth to broadcast several
The aspect ratio of a television screen is
the ratio of its width to its height. The
standard television screen is 4 units wide
for every 3 units tall, so its aspect ratio is
4 x 3 or 4:3.
However, many HDTVs have an aspect
ratio of 16:9 (meaning that the screen is
16 units wide for every 9 units tall).
The resolution of an HDTV screen
indicates the amount of detail that the
screen can display. This resolution is
identified by the number of display lines on
the screen. For example, 1080i means that
the screen shows 1080 lines in interlaced
format, and 480p means that the screen
shows 480 lines in progressive format.
Standard Screen HDTV
(4:3 Aspect Ratio)
About HDTV About HDTV About HDTV
About HDTV
standard-definition channels. Most stations,
however, once they begin broadcasting in
digital, are offering HD content from their
parent station, that is, CBS, ABC, NBC,
Fox, WB, UPN, or PBS.
Progressive and interlaced format describe
the technique that your HDTV uses to
"paint" the picture on the screen. Inter-
laced format updates half of the lines on
the screen with every new video frame. In
one frame, an interlaced screen will update
all of the odd-numbered lines on the
screen. In the next frame, it updates all of
the even-numbered lines.
By contrast, progressive format updates
each line on the screen every time the
frame changes.
Your set-top can display the following
formats:
• 1080 lines, interlaced (1080i)
• 720 lines, progressive (720p)
• 480 lines, progressive (480p)
• 480 lines, interlaced (480i)
Wide Screen HDTV
(16:9 Aspect Ratio)