Method of and apparatus for movement portrayal with a raster, e.g. television, display

摘要

To portray movement in a television display, a field of the signal is stored in an image store (110), and subsequent input fields are compared in a motion detector (104) with the sorted field to detect differences between them due to movement. A flag is retained in an auxiliary store (114) to indicate the positions in the field of the detected differences. For those positions for which a new difference is detected, i.e. for which no difference has been detected previously, the corresponding portions of the then current input scan are stored in the image store (110), by a switch (106) being connected to the input (102). For portions which are flagged, the output of the auxiliary store (114) causes the switch (106) to take the output of the image store (110), thus insetting past positions of movement into the current field. The background of the field in the image store is nevertheless updated by the background of the input field. To allow for the 4-field NTSC or 8-field PAL cycle, transducers, or predictors, (170,160) are placed at the input and output of the image store (110) such that the image store retains information in one state only of the cycle. The motion detector (104) comprises a subtractor, a rectifier and a low- pass filter.