"' 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.
2.
In systems historically based on NTSC standards, for reasons originally related to the Chrominance subcarrier in analog NTSC TV systems, the exact frame rate is actually ( 3579545 / 227.5 ) / 525 = 29.97002616 fps.
3.
Additionally, in order to minimise beat-patterns between the chrominance subcarrier and the sound subcarrier, when PAL is used with System I, the sound subcarrier is moved slightly off the originally-specified 6.0 MHz to 5.9996 MHz.
4.
A " PAL 60 " signal is similar to an NTSC ( 525 / 30 ) signal, but with the usual PAL chrominance subcarrier at 4.43 MHz ( instead of 3.58 as with NTSC and South American PAL variants ) and with the PAL-specific phase alternation of the red colour difference signal between the lines.
5.
To provide sufficient bandwidth for the chrominance signal, yet interfere only with the highest-frequency ( and thus least perceptible ) portions of the luminance signal, a chrominance subcarrier near 3.6 MHz was desirable . 227.5 = 455 / 2 times the line rate was close to the right number, and 455's small factors ( 5 ?7 ?13 ) make a divider easy to construct.
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