System for allowing two television programs simultaneously to use the normal bandwidth for one program by chrominance time compression and luminance bandwidth reduction

摘要

A method and apparatus for bandwidth compression allows two television programs to simultaneously occupy the bandwidth normally allowed for one television program. The composite video signals from first and second program sources are separated into chrominance, luminance and synchronization component signals for each. The chrominance signals for each program source are compressed in time, and the sync pulse from one of the program sources is used to generate a narrow sync pulse. The luminance signal from the one program source modulates a carrier signal, and the luminance signal from the other program source modulates a subcarrier signal. The compressed chrominance signals for the first and second program sources are transmitted, with the narrow sync pulse, for alternate lines of each image frame for each program, respectively, during the inactive video time, and the luminance signals for both program sources are transmitted during the active video time for each line of each image frame for each program, respectively. At the receiver, the compressed chrominance and the luminance signals for both program sources are detected, and the compressed chrominance and the luminance signals for one or the other of the two program sources are selected. The selected chrominance signal is stored during the inactive video time in an analog delay line, the output of which is combined with the selected luminance signal to reconstruct a composite video signal for the selected program source during the active video time in the selected program.