Display system for selectively overlaying symbols and graphics onto a video signal

摘要

A display system for the on screen display of information for a subscriber terminal of a subscription television system includes a display processor which can display information in the form of a display screen stored in a display memory. The display processor can be preprogrammed by the control processor with a plurality of display attributes including different symbol sets, different color palettes, whether the screen is to be a text screen, graphic screen or a combination of a text and graphics system, and the size and location of each screen display on the display area. The display processor includes a digital processor and an analog processor. The digital processor controls accessing the display data from the memory and converting it into timed digital pixels. The analog processor includes a digital to analog pixel converter which produces analog pixels from the digital pixels in a timed relation to an input video signal. The analog processor includes a multiplexer which substitutes the analog pixels for the pixels of the input video signal when display processor is active.