Apparatus for controlling on screen display

Abstract

A video signal of a sub-picture screen is supplied from an input terminal ( ) via an adder ( ) for superimposing display to a forming control circuit ( ) for a sub-picture screen signal, and a sub-picture screen video signal, which is compressed to an arbitrary size, is synthesized with a video signal of a main picture screen from an input terminal ( ) at a change-over switch ( ). Further, in accordance with a command signal supplied to a microcomputer ( ), a central processing unit (CPU) ( ) produces a control signal which decides a size, a position and the like of display of sub-picture screen. Also, a signal from the central processing unit is supplied to a display control circuit ( ) which then produces a figure signal to be superimposed and displayed. Set values of size, position and the like of sub-picture screen display are recorded on and held by a random access memory (RAM) ( ). The set values are supplied through the central processing unit ( ) to the display control circuit ( ) and hence such a figure signal is produced that the figure is reduced or expanded in response to expansion or reduction of the sub-picture screen.