TV input source identifier

Abstract

The disclosed circuit determines whether a video signal is from a video tape player or a broadcast signal source by measuring jitter of the vertical synchronization pulses. In one embodiment, every other time interval between the vertical synchronization pulses is measured and saved as a count, and each count is compared to the preceding count to determine whether sufficient jitter is present to indicate that the video signal is from a local tape player. In another embodiment all intervals between the vertical synchronization pulses are measured and a predetermined number thereof are saved as counts. The even and odd counts are then analyzed separately, and the extreme count (the most deviant count) of each group is eliminated. With the extremes eliminated, the overall deviation of the counts from an average is determined for each group (even and odd) and such deviations are compared to predetermined data (a threshold) to decide whether jitter is sufficiently large to indicate that the source of the video signal is a local tape player.

Dependencies are inferred from the claim text.