Colorburst is an analog video, composite video signal generated by a video-signal generator used to keep the chrominance subcarrier synchronized in a color television signal. By synchronizing an oscillator with the colorburst at the back porch (beginning) of each scan line, a television receiver is able to restore the suppressed carrier of the chrominance (color) signals, and in turn decode the color information. The most common use of colorburst is to genlock equipment together as a common reference with a vision mixer in a television studio using a multi-camera setup.
In NTSC, its frequency is exactly 315/88 = 3.579 MHz with a phase of 180°. PAL uses a frequency of exactly 4.43361875 MHz, with its phase alternating between 135° and 225° from line to line. Since the colorburst signal has a known amplitude, it is sometimes used as a reference level when compensating for amplitude variations in the overall signal.
SECAM is unique in not having a colorburst signal, since the chrominance signals are encoded using FM rather than QAM, thus the signal phase is immaterial and no reference point is needed.
The original black and white NTSC television standard specified a frame rate of 30 Hz and 525 lines per frame, or 15750 lines per second. The audio was frequency modulated 4.5 MHz above the video signal. Because this was black and white, the video consisted only of luminance (brightness) information. Although all of the space in between was occupied, the line-based nature of the video information meant that the luminance data was not spread uniformly across the frequency domain; it was concentrated at multiples of the line rate. Plotting the video signal on a spectrogram gave a signature that looked like the teeth of a comb or a gear, rather than smooth and uniform.
RCA discovered that if the chrominance (color) information, which had a similar spectrum, was modulated on a carrier that was a half-integer multiple of the line rate, its signal peaks would fit neatly between the peaks of the luminance data and interference was minimized.
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Colorburst is an analog video, composite video signal generated by a video-signal generator used to keep the chrominance subcarrier synchronized in a color television signal. By synchronizing an oscillator with the colorburst at the back porch (beginning) of each scan line, a television receiver is able to restore the suppressed carrier of the chrominance (color) signals, and in turn decode the color information. The most common use of colorburst is to genlock equipment together as a common reference with a vision mixer in a television studio using a multi-camera setup.
Le Sécam ou SECAM, acronyme de « séquentiel couleur à mémoire », désigne un standard international de codage couleur du signal vidéo analogique, inventé par l'ingénieur français Henri de France, breveté en 1956 et expérimenté en télédiffusion en décembre 1961 à Paris sur la Tour Eiffel, puis en 1963 sur la deuxième chaîne ORTF et lancé officiellement à l'antenne, à partir de 1967. Ce standard couleur peut être exploité par différents équipements analogiques vidéo tels que caméras, écrans ou téléviseurs, magnétoscopes ou dispositifs d'enregistrement vidéo, micro-ordinateurs et consoles de jeux.
L'acronyme NTSC (National Television System Committee, signifiant en français « Comité du système national de télévision » désigne un standard international de codage couleur du signal vidéo analogique, finalisé en 1953 par les ingénieurs de plusieurs sociétés américaines, parmi lesquelles CBS Corporation et surtout les sociétés RCA et Philco. Aux États-Unis, le marque la première télédiffusion nationale en couleur au standard NTSC.