5
Method 2
Letterbox
Entire
16x9
Picture
30I Picture Format
= 2/60
second or
1/30
1/60 sec.
Field 1
1/60 sec.
Field 2
+
4
3
16
9
Method 1
Cropping
Shaded
area
Cropped/
removed
Center
of 16 x 9
picture
The NTSC format is commonly written as “30i” picture format because it
takes 1/30 of a second to complete an interlaced picture.
Aspect Ratio
Although the first pictures were round, later TV pictures adopted a rectan-
gular shape. The aspect ratio of these pictures is the same as they are
today, 4 x 3 ratio.
Movie theaters show films in a wider 16x9 aspect ratio. This 16x9 picture
is also the way most films are shot. To present the original 16x9 picture
on a 4x3 TV screen, one of two common methods is adopted to fit the
picture:
In method 1, the 16x9 picture is cropped or cut off at the left and right. The
main action part of the picture (usually the center or near center) is the
only part transmitted.
In method 2, the 16x9 picture is shrunken and placed on the TV screen.
The entire picture is seen but with black areas above and below the pic-
ture. This method of viewing the entire 16x9 picture on a 4x3 set is called
a Letterbox picture. Letterbox pictures can be selected on some DVD
players and TV sets from the menu if the DVD or TV transmissions offer
it.
USA Digital Transmission Formats
There are 18 digital transmission formats approved by the ATSC (Ad-
vanced Television Standards Committee) in the USA. The first six offer
HD (high definition/resolution) signals in a 16x9 aspect ratio. The remain-
ing 12 formats are SD (standard definition) signals in progressive (p) or
interlaced (i) scan. Note that the 480p signal can be a 4:3 or 16:9 aspect
ratio transmission.
18 Digital Transmission Formats
Resolution
Aspect
Ratio
Frame
Resolution
Aspect
Ratio
Frame
1. 1080x1920
16:9
30 i
10. 480x 704
16:9
24 p
2.
16:9
30 p
11.
4:3
60 p
3.
16:9
24 p
12.
4:3
30 i
4. 720 x 1280
16:9
60 p
13.
4:3
30 p
5.
16:9
30 p
14.
4:3
24 p
6.
16:9
24 p
15. 480x 640
4:3
60 p
7. 480x 704
16:9
60 p
16.
4:3
30 i
8.
16:9
30 i
17.
4:3
30 p
9.
16:9
30 p
18.
4:3
24 p
A standard definition transmission contains less data, permitting space
for another digital video stream to coexist on the same frequency (chan-
nel). Therefore, a station can have more than one program stream on a
digital channel. The maximum number of programs is six.
Digital TV (DTV) Converter Boxes
TV broadcasters are transmitting their analog signals on one channel and
their DTV signals on another. A list of their analog and digital channel
assignments by state is located at
www.transmitter.com
.
To receive a DTV station on an analog TV, a set top converter box is
used. The box receives digital RF and outputs analog composite video to
the TV. The boxes can also output higher resolution video signals to a
high-resolution analog TV. These cable boxes are flexible at their input
and outputs:
Summary of Contents for KV-32XBR400
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