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Signal Format Analog (NTSC)
Digital (ATSC/DIRECTV)
SD HD
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2-2. TV Signal Format
The digital TV standards allow several different formats. Broadcasters can choose between
three formats:
• 480p - The picture is 704 x 480 pixels, sent at 60 complete frames per second (480i is
also possible).
• 720p - The picture is 1280 x 720 pixels, sent at 60 complete frames per second.
• 1080i - The picture is 1920 x 1080 pixels, sent at 60 interlaced frames per second (30
complete frames per second).
(The “p” and “i” designations stand for “progressive” and “interlaced.” In a progressive for-
mat, the full picture updates every sixtieth of a second. In an interlaced format, half of the pic-
ture updates every sixtieth of a second.)
The 480p and 480i formats are called the SD formats, and 480i is roughly equivalent to a nor-
mal analog TV picture. The 720p and 1080i formats are called the HD formats.
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 maximum 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.
Standard Comparison Table
Active Lines 480i 480p 720p or 1080i
Sound Stereo (2 ch)
Dolby Digital (5.1 ch) Dolby Digital (5.1 ch)
MPEG Audio (2 ch)
Aspect Ratio 4 : 3 4 : 3 or 16 : 9 16 : 9
Resolution 720 x 480
640 x 480 1280 x 720
704 x 480 1920 x 1080