DirecTV HR10-250 User Manual page 41

O f f - A i r C h a n n e l s a n d V i d e o S e t u p
What's the difference between 1080i, 720p, 480p, and 480i?
These are names for different video resolution formats. Each name includes a number and
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a letter. The number indicates how many horizontal lines of information make up a single
video image. Generally, bigger numbers mean sharper, more detailed images. The letter
indicates whether the output uses "interlaced" or "progressive" scanning.
With interlaced scanning, the horizontal lines in a video frame are divided into two
groups. If you were to number the lines from the top to the bottom of the screen, one group
would be the odd numbered lines, and the other would be the even numbered lines.
Interlaced video refreshes half of the video frame 60 times per second—alternating
between the odd and even lines. This means the whole video frame refreshes 30 times per
second. This is fine for smaller screens but can result in flickering on larger screens.
Progressive scanning refreshes the whole video frame (all even and odd horizontal lines),
60 times per second. This eliminates flicker but requires the TV to process more
information since twice as many frames are displayed each second.
For any given resolution (number of scan lines), progressive scanning looks better than
interlaced. Standard TV has 480 lines, uses interlaced scanning, and is referred to as 480i.
Many HDTVs offer a display format called 720p (720 lines with progressive scanning).
Video formats 720p and 1080i have similar picture quality, each having the edge over the
other under particular circumstances. For example, 1080i shows detail better in still
images or when there is little motion, whereas 720p excels when there is lots of action.
The size and capabilities of your high-definition TV will also inform your choice of video
output formats, so be sure to check its owner's manual.
High-resolution video signals require special types of cables and connections. It's
important to remember that Composite A/V and S-Video cables do not support enhanced-
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