Inventor: Robert H Nagel

US patent number:3,875,329

US patent application date: January 17, 1974
US patent issue date: April 1, 1975

SYNOPSIS OF THE INVENTION

A real time frame grabbing system for essentially instantaneous provision of a continuous video display for selected information. This system also provides a video display from a large number of different and continuously transmitted frames of video information. The selected frame, which is grabbed in real time, may be continuously updated in real time. The selection frame is located by counting of the vertical sync pulses, the counter being reset in accordance with detection of a frame sync pulse on a predetermined horizontal scan line of a frame, the interval between these reset pulses being dependent on a predetermined minimum update time and maximum access time for a frame.

The updating of a frame is provided in accordance with the detection of another pulse located on a different horizontal scan line and used for the frame sync pulse when the frame contains updated video information. Capture logic is responsive to detection of these signals either indirectly or directly in order to control a local memory which captures the frame for continuous video display thereof until either a new frame is selected or the selected frame is updated, the capture video information changing in either instance. The coding of the predetermined horizontal scan lines with the frame sync information and update control signals is provided in conventional fashion by a conventionally programmed computer which retrievably stores the continuously transmitted video frames in a mass memory. This stored information is supplied to a video generator which creates a frame of video information at a predetermined rate from data contained in the mass memory.

The resulting signal can modulate RF and can be transmitted any way suitable for standard television transmission. This signal is subsequently retrieved by logic that compares the actual frame number with the frame number requested, such as by keyboard, and if they agree, captures and stores this information in the local memory for continuous readout and display. The incoming video signal provides the vertical and horizontal sync information as well as being available for storage on command from capture logic. The provision of a capture command to the local memory causes the frame to be stored which is then continuously read out, such as into a sync adder, and therefrom to the video display means. Thus, a single frame of video information may be instantaneously selected in real time from continuously transmitted video information and such selected frame may be automatically updated as new information is provided in real time.