ABSTRACT
Here, I’m going to limit the concepts to a few I think
are not only essential, but also relatively easy to
understand. For a thorough technical guide, check
out How Video Works by Diana Weynand and Marcus
Weise (www.focalpress.com). Use this section either
as a reference section or an aid to understanding the
material later:
Interlace
A video screen is made up of a series of horizontal
lines of color and brightness information. For
example, an NTSC (American) screen has 480
horizontal lines running across it. Interlacing is the
sequence in which the lines are drawn. In an
interlaced image, the 240 even-numbered lines are
drawn from top to bottom first, then the 240 odd-
numbered lines. Drawing both fields takes about
1/30th of a second on American television (with a
frame rate of 29.97 frames per second). Each field,
odd or even, takes about 1/60th of a second to draw.
