A PROCESSING METHOD AND APPARATUS FOR PERFORMING 4 X 4 DISCRETE COSINE TRANSFORMATION OR INVERSE DISCRETE COSINE TRANSFORMATION

A two-dimensional 4.times.4 discrete cosine transformation (4.times.4 DCT) in which the number of multiplications is small and the calculation precision is not lowered can be defined by the relationship between input matrix data [X] and output matrix data [Y], by [Y]=1/4.multidot.[W] [V] [R] [Q] [R] [Q] [X] as factorization equations. The matrices [R], [Q], and [V] are constant matrices including "0", "1", and "-1", and the matrix [W] is a matrix indicating irrational numbers defined by two-dimensional 4.times.4 DCT. The computation of the constant matrices [R], [Q], and [V] can be realized by addition-subtraction, and the multiplication is carried out only for the computation of matrix [W]. The first addition-subtraction circuit (2) performs the first computation between [X] and [RQ] and the first computation between this result with [RQ] by time division, the second addition-subtraction circuit (2) performs the remaining second computation between [RQ] and [S] and a third computation between this result and [V] by time division, and the multiplication-addition circuit (6) performs the computation between [U] and [W]. The intermediate value holding circuits (3 and 5) hold the intermediate calculation values in the time division computation.