TODAY TELEVISION SIGNALS are encoded, broadcast, and received in the
United States using the color system of the National Television Systems
Committee (NTSC). Almost 40 years old, this system has well-known
performance limitations. It is subject to flickering and ghosting, it has
low resolution (more apparent as TV sets become larger), and it requires
cutting off the side panels in showing material shot for exhibition on
wide movie screens. NTSC is derisively known in some circles as
“Never Twice the Same Color.” Although it nominally has 525 horizontal
lines, a mere 483 “active” lines produce the picture; the rest
carry auxiliary information. Moreover, NTSC is interlaced: only half
of the lines are displayed on each pass. This creates a visible flicker
when there are horizontal lines in the scene portrayed, so studios deliberately
reduce the resolution. Even with ideal reception, the resolution
is roughly equivalent to that achievable with 330 to 350 lines.
The PAL and SECAM standards are significantly better, but still noticeably
imperfect. Developed about 15 years later than NTSC, they
are used in much of the world outside North America and Japan.
