VIDEO DISPLAY CONTROL SYSTEM

摘要

PURPOSE: To enable a letter box detecting circuit to automatically respond to specified information and to prevent a letter box detecting circuit from erroneously responding to information which is not specified. CONSTITUTION: Video information in an image to be represented by an input video signal in a form of a letter box is sampled, and a control signal to extend the image to almost satisfy a video display with an effective video is generated by a letter box detecting circuit 100. Motion of the letter box detecting circuit 100 is restricted within a vertical range, including a specified number of horizontal line in each field of the video signal by a first control circuit 128 including comparators 130 and 132. The motion of the letter box detecting circuit 100 is restricted within a horizontal range, including a specified number of video data in each horizontal line by a second control circuit 101 which includes comparators 102 and 104.