5
Introduction
Resolution an interlacing
Two of the elements determining the quality of a TV
picture are resolution and interlacing.
Resolution
For TV equipment and broadcasts, resolution is
defined by the number of horizontal lines displayed
to make up each frame of a video image. The more
lines of resolution used to draw each frame of
video, the more detailed and sharp the picture will
be. Standard TV resolution uses 480 horizontal
lines to make up each of video.
HDTV uses either 720lines, or 1080 lines to make
each video frame.
Interlacing
When TVs display video, they display a new video
frame at a rate that is faster than your eye can see
(from 24 to 60 frames per second, depending on
the TV and broadcast). Interlacing refers to whether
each of those frames contains all of the lines of
video for each frame or every other line. Interlaced
signals take every other line frame 2 frames of
video (each lasting 1/60
th
of a second), and
combine them into one frame lasting 1/30
th
of a
second. In this way, interlacing tricks your eye into
thinking it is seeing twice the resolution that is
actually being displayed.
In non-interlaced video, (referred to as progressive
scan video), video frames are displayed every
1/60
th
of a second containing all of the lines of video
information for each frame.
The specifications for video resolutions are usually
stated by giving the number of horizontal lines,
followed by either the letter i, for interlaced video, or p
for progressive scan video. Some DVDs and
non-HDTV digital TV broadcasts use 480p.
The ATSC specification for HDTV broadcasts and
equipment requires either 1080i or 720p while there
is some debate as to whether it is better to have more
lines that are interlaced that 1080i is highest quality
video format.
Video output
The PHD-200 Digital HDTV Tuner is able to receive
broadcasts in any of the resolutions mentioned
above. It can also display programs on TVs capable
of displaying any of those resolutions.
To set up your PHD-200 to handle the combinations
of incoming video formats and TV display capabilities,
you simply set the Resolution Switch on the rear
panel to match the highest resolution your TV is
capable of displaying. (If you’re not sure about your
TV’s resolution, see your TV’s manual for this
specification.)
PHD-200 will then do the appropriate conversion
from input signal format to display format.
Video output formats:
Output Connection
Available Formats
YPbPr 1080i/720p/480p/480i
DTV(RGB) 1080i/720p/480p
DVI 1080i/720p/480p/480i
Aspect ratio
In addition to resolution and interlacing, HDTV is also
defined by the aspect ratio of its broadcasts.
Aspect ratio means the shape of the screen as
defined by the ratio of the screen’s width to its height.
For analog TV and SDTV, the aspect ratio is 4 units
wide by 3 units high (usually written 4:3).
This is familiar shape of conventional TVs----slightly
wider than they are tall.
For HDTV broadcasts, the aspect ratio is 16:9 (nearly
twice as wide as it is tall).
This is, not coincidentally, more like the shape of
movies shown in theaters.
This makes HDTV an ideal format for broadcasting
and viewing movies on a TV.
But what happens if you are watching a nearly
square-shaped 4:3 broadcast on a rectangular 16:9
TV. The PHD-200 Digital HDTV Tuner allows you to
choose from a variety of screen formats to help you
dealing with those scenarios.