8
Resolution an interlacing
Two of the elements that determine 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.
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.
Input formats
TV SET-UP BOX is able to receive broadcasts in any of the
resolutions mentioned above.
It will then do the appropriate
conversion from input signal format to general TV display
format.
The table below details the results you get with each
combination of input signal format.
Type
Aspect
Ratio
Compression
Size Values
Frame
Rate
p
0
3
8
1
p
4
2
7
1
16
1920
×
1080
30i
p
0
6
5
1
p
0
3
4
1
13
H
D
T
V
1280
×
720
24p
p
0
6
2
1
p
0
3
1
1
p
4
2
0
1
9
16:9
30i
p
0
6
8
p
0
3
7
p
4
2
6
5
704
×
480
30i
p
0
6
4
p
0
3
3
p
4
2
2
1
S
D
T
V
4:3
640
×
480
30i