A motion vector detection apparatus wherein a macro block most similar to an object macro block in a frame under image processing is detected in a retrieval range prescribed in a reference frame which is close in time to the frame under image processing, which comprises:
- vector evaluation value calculation means for setting one of two frames representing a dynamic image which are close in time to each other as a reference frame, setting the other of the two frames as a frame under image processing, associating pixels forming arbitrary one macro block among macro blocks obtained by dividing the frame under image processing into a plurality of regions with pixels forming an inspection framework existing in the reference frame and having the same size as that of the macro block, in one-to-one correspondence, and calculating a vector evaluation value from a result obtained by accumulating signal level difference values of the pixels;
- retrieval range setting means for setting a retrieval range, in response to a position of a macro block included in the frame under processing and to be calculated by the vector evaluation value calculation means, a position in which the same image portion as the macro block exists is retrieved in the retrieval range by using the inspection framework;
- inspection framework moving means for moving the inspection framework to a next new position within the retrieval range set by the retrieval range setting means and causing a vector evaluation value to be calculated for the new position, whenever the vector evaluation value calculation means finishes the vector evaluation value calculation operation in response to one inspection frame;
- motion vector detection means for deriving a motion vector represented as a vector linking an inspection framework having a minimum vector evaluation value to the macro block included in the frame under processing and to be calculated by the vector evaluation value calculation means, when all movements of the inspection framework in the retrieval range caused by the inspection framework moving means have been finished;
- macro block specifying means for specifying a macro block in order to detect a motion vector, so long as there is at least one macro block in the frame under processing for which a motion vector has not been detected, whenever the motion vector detection means detects a motion vector for a macro block in the frame under processing;
- fixed detection threshold value setting means for setting a fixed detection threshold value serving as a value for fixing motion vector detection, based on already derived vector evaluation values, if any, among vector evaluation values of a predetermined number of macro blocks located in the same frame under processing near and having specific position relations to a macro block specified by the macro block specifying means;
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- motion vector detection decision means for comparing a vector evaluation value obtained whenever the inspection framework is moved within the retrieval range by the inspection framework moving means with the fixed detection threshold value set by the fixed detection threshold value setting means, and responding to emergence of an inspection framework having a vector evaluation value which is at most the fixed detection threshold value, by judging a motion vector determined by a relation to the inspection framework to be a motion vector finally obtained with respect to the macro block and finishing the movement of the inspection framework with respect to the macro block.