Patent GB-1329146-A (GB)
Title: System for encoding video signals
IPC: H04N7/26
Filed: 1970-12-23
Abstract: 1329146 Encoding video signals WESTERN ELECTRIC CO Inc 23 Dec 1970 [23 Dec 1969] 61073/70 Heading H4F In a system for encoding video signals the intensity of points at common geometric locations in a present frame and the previous frame are compared and those points having substantially different intensities in these two frames are designated as part of a region of movement in the present frame, the intensity of each such point X forming part of a region of movement in the present frame is correlated with the intensity of points in the previous frame at locations surrounding the location of the corresponding point Y, and combining these correlations to determine the average translation of the region of movement, and forming a predicted present frame by duplicating at locations in the predicted present frame corresponding to locations of points in the present frame the intensities of points in the previous frame displaced by the average translation and duplicating at other points the intensities of undisplaced points in the previous frame. The intensities of points X in the present frame are successively applied to a delay line 31 which contains previously supplied intensities of points Y in the previous frame. Comparison of points X and Y are made by a threshold comparator 32 which produces a binary output of unit value only when the points have substantially different intensities, this output being fed to AND gates 33 which also receive the outputs of a number of correlators which serve to compare the intensity of point X with the intensities of points surrounding Y. The outputs of the AND gates are fed to integrators, which average these outputs, and thence to a selector 34 which determines the largest integrator output and hence which average translation of the region of movement is most likely. For each frame, the output of selector 34 sets data switch 36 to an input from delay line 35 in which the past frame is stored to select a point in the past frame corresponding to the most likely average translation and provide an intensity value which represents the predicted translation. Thus the predicted frame is the past frame except that elements within the region of movement are replaced with translated elements chosen by switch 36. A signal representative of the difference between the actual intensities of points in the present frame and the predicted intensities is provided by substractor 39. An address signal is also provided by counter 38 to identify the position of the point. Gates 40 and 41 restrict transmission of the difference signal and address information to those elements in the region of movement. The decoder, Fig. 5, not shown, at the receiver is basically an encoder in reverse except that it does not compute average translations. It delivers the video output of the previous frame to a display mechanism except for elements in the region of movement which latter are replaced with the sum of the appropriately translated point from the previous frame and the received difference signal. Simultaneously the video signal is applied to a one frame delay line for use in decoding the next frame.