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206-3675
2-2. TV Signal Formats
What makes HD digital signals (including SD signals) special is that they provide a high reso-
lution and wide format, like a movie (16:9 TV aspect ratio). On the other hand, analog signals
have the standard or normal format (4:3 TV aspect ratio). Thus, you receive programs with two
distinct formats. Like a wide movie screen, the HD digital signals are formatted more like the
way we actually see; our field of vision is more rectangular than square. So, when we view
movies in a wide screen format, the image fills more of our field of vision yielding a stronger
visual impact.
HD digital program signals use smaller pixels that are closer together. In the area taken up by
a single pixel of a standard NTSC signal, HD digital signals will have four and a half pixels,
four times the detail. The more pixels in a given area, the better the picture.
Some NTSC televisions can display a picture 720 pixels wide by 480 pixels high, that's a total
of 345,600 pixels. HD digital signals can have a resolution of 1920 x 1080, that's 2,073,600
pixels, or six times more pixels than the older resolution. Pictures will be crisper and cleaner,
with more detail in every close-up and every panorama.
Standards Comparison Table
Signal Format
Total Lines
Active Lines
Sound
Aspect Ratio
Max Resolution
Analog (NTSC)
HD Digital (ATSC/DIRECTV
)
1125
1080
Surround (5.1 ch)
16 : 9
1920 X 1080
525
480
Stereo (2 ch)
4 : 3
720 X 480
