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Unformatted text preview: ideos using composite video signals technology. They mainly
differ in the way they encode the chrominance signal. They also differ in screen
resolution and frame rate. Their characteristic features are briefly described below.
1. NTSC. NTSC stands for National Television Systems Committee. It is a 525
scanlines system that uses interlaced scanning technique with a refresh rate of
29.97 frames per second. In NTSC, the luminance signal is called the Y signal,
and the chrominance signal is amplitude modulated onto the color subcarrier at
two different phases - the / (in-phase) value at 0° and the Q (quadrature) value at
90°. NTSC is used in the US, Japan , and some Asian countries.
2. PAL. PAL stands for Phase Alternating Line. It is a 625 scanlines system
that uses interlaced scanning technique with a refresh rate of 25 frames per second.
In PAL, the composite video signal operates on the YUV model, where Y is the
luminance component and (U, V) are the chrominance components. In PAL also,
the chrominance signal is transmitted on a two-phase amplitude-modulated color
subcarrier but it uses a more complex process called Phase Alternating Line, which provides more bandwidth for chrominance modulation, yielding better color
resolution. PAL is used in India and Western Europe (except France).
3. SECAM. The SEC AM system, developed in France, stands for Sequential
Couleur Avec Memoire. It is a 625 scanlines system that uses interlaced scanning
technique with a refresh rate of 25 frames per second.
In SECAM, the
chrominance signal is transmitted using a frequency-modulated color subcarrier,
transmitting one of the color difference signals on every other scanline, and the
other color difference signal on alternate scanlines. It also has better color
resolution than NTSC. SECAM is used in France, Eastern Europe, Russia, and
A summary of the characteristic features of the three analog TV signal standards is
given in Figure 19.6. Compared to NTSC, PAL and SECAM have better
resolution but lower refresh rates and hence more flicker.
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This document was uploaded on 04/07/2014.
- Spring '14