Patent ID: 7508453

Claim:
A video display apparatus, comprising: a source of a periodic synchronization signal for synchronizing an operation of a display device responsive to an accompanying video signal that provides picture information; a utilization circuit operating in a normal operation mode, when said synchronization signal is valid, and in a second operation mode, when said synchronization signal is invalid; and a processor responsive to said synchronization signal and coupled to said utilization circuit for producing a plurality of values corresponding to successive occurrences of said synchronization signal, a given value of said plurality of values being indicative of a length of an interval that has elapsed from a preceding occurrence of said synchronization signal, and wherein said processor produces a statistical variance indicative value in accordance with a difference between said given value of said plurality of values and a mean value of said plurality of values, wherein said value indicative of a statistical variance of a frequency of said synchronization signal indicates to change the mode of operation of said utilization circuit from said normal operation mode to said second operation mode, when the statistical variance exceeds a first threshold value.