Signal Components
A composite video signal combines on one wire the video information required to recreate a color picture, as well as line and frame synchronization pulses. The color video signal is a linear combination of the luminance of the picture, and a modulated subcarrier carries the chrominance or color information, a combination of hue and saturation. Details of the encoding process vary between the NTSC, PAL and SECAM systems.
The frequency spectrum of the modulated color signal overlaps that of the baseband signal, and separation relies on the fact that frequency components of the baseband signal tend to be near harmonics of the horizontal scanning rate, while the color carrier is selected to be an odd multiple of half the horizontal scanning rate; this produces a modulated color signal that consists mainly of harmonic frequencies that fall between the harmonics in the baseband luma signal, rather than both being in separate continuous frequency bands alongside each other in the frequency domain. In other words, the combination of luma and chroma is indeed a frequency-division technique, but it is much more complex than typical frequency division multiplexing systems like the one used to multiplex analog radio stations on both the AM and FM bands.
Colorburst is a composite analog video signal generated by a video-signal generator used to genlock, keep the chrominance subcarrier synchronized in television studios for color television.
Read more about this topic: Composite Video
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