Automatic shift circuit for a sub-picture screen for picture-in-picture feature

摘要

An automatic-shift circuit for a sub-picture screen for PIP feature is disclosed. The circuit includes; a brightness signal separator device for separating only the brightness signal from the composite video signal for the main picture screen; a brightness level comparison device for selecting the character brightness level and the width thereof from the separated brightness signals; and a identical position comparison device for determining whether the character brightness width is detected at the identical position. The circuit also includes a device for setting the vertical and the horizontal timing; a counter for counting the field number where character brightness width is detected at the identical position and for generating the automatic shifting signal if the field number counted is beyond the predetermined value; and a microcomputer for controlling the PIP processing unit so as to shift the sub-picture screen upon receipt of the automatic shifting signal. This invention enables the sub-picture screen to automatically shift to another pre-specified area according to the presence of character information on the main picture screen overlapping with the sub-picture screen.