Patent ID: 7327399

Claim:
A method for deriving a synchronisation signal from a video signal having a synchronisation pulse signal therein, the method comprising the steps of: selecting a value of at least one of a first slice level signal and a second slice level signal, the at least one of the first and second slice level signals being of selectable value, and the first and second slice level signals defining a first amplitude bandwidth therebetween, the selected value of the at least one of the first and second slice level signals being such that the second slice level signal lies on the side of the first slice level signal in a direction similar to that from which the synchronisation pulse signal is expected to extend from the blanking level of the video signal, and the value of the blanking level of the video signal lies within the respective values of the first and second slice level signals, deriving a value of an intermediate slice level signal from the current value of at least one of the first and second slice level signals and the current value of a signal indicative of the value of the sync tip of the synchronisation pulse signal of the video signal, so that the value of the intermediate slice level signal lies intermediate the current value of the at least one of the first and second slice level signals and the current value of the signal indicative of the value of the sync tip of the synchronisation pulse signal of the video signal, comparing the video signal with the intermediate slice level signal, and producing the synchronisation signal by providing a logic signal at one of a logic high level and a logic low level and transitioning the logic signal from the one of the logic high level and the logic low level to the other of the logic high level and the logic low level in response to the value of the video signal transitioning in at least one direction across the value of the intermediate slice level signal.