 - The NTSC (National Television Standards
Committee) was responsible for developing, in 1953, a set of standard protocol for
television (TV) broadcast transmission and reception in the
United States. Two other standards - Phase Alternation Line (PAL) and Sequential Couleur avec Memoire (SECAM) - are used in other parts of the world. The NTSC standards have not changed significantly since
their inception, except for the addition of new parameters for
color signals. NTSC signals are not directly compatible with
computer systems.
An NTSC TV image has 525 horizontal lines per
frame (complete screen image). These lines are scanned from left
to right, and from top to bottom. Every other line is skipped.
Thus it takes two screen scans to complete a frame: one scan for
the odd-numbered horizontal lines, and another scan for the
even-numbered lines. Each half-frame screen scan takes
approximately 1/60 of a second; a complete frame is scanned every
1/30 second. This alternate-line scanning system is known as
interlacing.
Adapters exist that can convert NTSC signals to
digital video that a computer can "understand."
Conversely, there are devices that can convert computer video to
NTSC signals, allowing a TV receiver to be used as a computer display. But because a
conventional TV receiver has lower resolution than a
typical computer monitor, this does not work well for all
computer applications, even if the TV screen is very large.
In recent years, there has been increasing
pressure to adopt a new set of TV standards. One of the proposed
protocols is known as high-definition
television (HDTV). Ideally, the HDTV standard that is
ultimately adopted will be directly compatible with computer
systems. However, there are engineering problems associated with
this. Some industry experts fear such compatibility could
dramatically increase the cost of a conventional TV set.
| CONTRIBUTORS: |
Roopesh Doshi |
| LAST UPDATED: |
27 Jul 2001
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