Appendix 1

Appendix 1: Understanding the NTSC Video Format and Digital Video
Figure A1.3 Even video fi eld. The spot then traces in the even numbered lines, 240 more lines
between the fi rst set as well as 22.5 more lines of sync. On a properly set up TV, the odd and even
lines are the exact right width so that they do not overlap or leave any spaces between the lines
Figure A1.4 Full frame video. The fi nished “interlaced” frame therefore consists of 480 lines of picture
and 45 lines of sync for a total of 525 lines per frame. As the frame rate is 29.97 per second, the fi eld
rate is 59.94 fi elds per second
Does this mean that if we could freeze time, all that would be on the screen would be a tiny dot of
color? To some extent, the answer is both yes and no. Different TV sets have different amounts of
“lag,” which is to say that once the “spot” area of the screen lights up, it takes a small fraction of a
second for it to dim and go out. By then, the spot has moved on, and may even be several lines
further down the screen. So if we could freeze time we would see a very narrow band of image across
the screen, dimmer at the top than the bottom. The full image is created in the viewer’s eyes and
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