In an adaptive motion direction detecting apparatus, an image input unit inputs two-dimensional pixel data of an object. A response output unit includes a plurality of response element arrays each having different time phases, and each of the response element arrays includes a plurality of response elements. Each of the response elements generates a response output for one of a plurality of local areas partly superposed thereon, and the two-dimensional pixel data is divided into the local areas. A correlation function calculating unit calculates spatial and time correlation functions between the response outputs of the response elements. A response output selecting unit selects response outputs of the response output unit for each of the local areas in accordance with the spatial and time correlation functions. A motion direction detecting unit includes a plurality of detection elements each corresponding to the response elements. Each of the detection elements detects a motion direction of the object at one of the local areas in accordance with selected response outputs therefor.

In a correlation arithmetic system adapted to detect a relative difference between two functions, an operation is simplified. This makes it possible to perform the operation with a small scale of hardware and also with great accuracy. There is adopted an operation g*h instead of the "product" in the correlation arithmetic operation. There is disclosed an arithmetic unit in which two numeral values a and b are inputted, and the two numerical values a and b are subjected to a predetermined operation process, so that a numerical value c representative of an operation result is derived. The arithmetic unit has an absolute value operation unit for evaluating an absolute value .vertline.c.vertline. of the numerical value c, and a sign operation unit for evaluating a sign "sign (c)" of the numerical value c.

It is determined whether each block (51) including a plurality of pixels extracted from a basic field (30) has an edge or not, and then which state, stationary or non-stationary, each of the pixels forming together the block (51) determined to have an edge is. There is calculated an absolute value of a difference between a pixel determined to be non-stationary and a pixel (91 or 92) in each pixel position in a reference field (40) or pixels (82 to 85) included in the reference field and adjacent to the non-stationary pixel, and a correlation is found between such pixels in consideration according to the calculated difference absolute-value. A motion vector is determined by the block matching method according to results of the determination, and allocated to each of the pixels. Thus, the motion vector of each block is corrected to an accurate one of each of the pixels.

A picture quality measurement technique using blockiness provides realtime analysis without the use of a reference signal. A field/frame of an image represented by a processed video signal is captured in a bit-map for analysis. The image is filtered to enhance edges and then correlated with a kernel having a size corresponding to the block size of the compression algorithm used in compressing and decompressing the video signal to produce the processed video signal. The correlation results are processed by comparing an average value with the maximum value to produce a picture quality rating for the processed video signal.