MOTION DETECTOR FOR MOVING IMAGE CODER

PROBLEM TO BE SOLVED: To reduce the circuit scale without deteriorating the accuracy of retrieval by providing two computing element groups, dividing picture elements of one peripheral block retrieved by the 1st computing element group into plural numbers and using the 2nd computing element group to make calculation for plural number of times thereby retrieving a block with a minimum difference. SOLUTION: When picture element strings By to By+x with a minimum difference are obtained by a 1st stage retrieval, peripheral picture element strings including the retrieved picture element strings are obtained as picture element strings C. In the 2nd stage, the number of computing elements used for difference calculation per one picture element is p and the arithmetic precision is enhanced by a multiple of p for the strings A, C as p×(n-m)bits}. In this case, since number of picture elements for difference calculation is decreased to 1/p, p times of calculation is required to obtain differences for (x+1) picture elements. Thus, the calculation result of each time is sequentially accumulated by using an adder 4 and a memory 7 and the final result is obtained after the arithmetic operation of p times. Thus, the retrieval error is reduced while using the computing elements in common for 1st and 2nd stages.