Dual-screen apparatus capable of preventing jitter and screen cutoff

摘要

An apparatus for composing two screens in a television which is capable of solving the problems of a jitter and a screen being cut off at the top and bottom portions caused by a non reference signal in composing two screens, includes a line memory for storing in the unit of lines a video signal for a main screen converted into a digital signal, a frame memory for storing in the unit of frames a video signal for a sub- screen converted into a digital signal, a mixing unit for receiving and mixing the outputs from the line memory and the frame memory to compose two screens, a D/A converter for converting an output from the mixing unit into an analog signal, an encoder for encoding an output from the D/A converter and outputting a double screen signal, a clock signal generator for receiving the horizontal synchronous signals for a main screen and a sub-screen, generating a clock signal corresponding thereto, dividing a horizontal fly back signal in a predetermined number in accordance with a division control signal and outputting the resultant signals, and a control signal generator for receiving an output from the clock signal generator to generate clock/timing pulse signals required in each unit and a read enable signal in accordance with the clock signal divided in a predetermined number when the above two memories read data.