MOTION VIDEO ENCODING APPARATUS, MOTION VIDEO ENCODING METHOD, MOTION VIDEO ENCODING COMPUTER PROGRAM, MOTION VIDEO DECODING APPARATUS, MOTION VIDEO DECODING METHOD, AND MOTION VIDEO DECODING COMPUTER PROGRAM

A motion video encoding apparatus includes: a prediction error image generating unit which computes a difference between a block being encoded and a predicted image for the block being encoded and thereby generates a prediction error image; a prediction error orthogonal-transforming unit which computes a plurality of first frequency coefficients by orthogonal-transforming the prediction error image; a predicted image orthogonal-transforming unit which computes a plurality of second frequency coefficients by orthogonal-transforming the predicted image; a sign judging unit which judges the positive/negative sign of each one of the plurality of second frequency coefficients; and an adaptive encoding unit which encodes each given one of the plurality of first frequency coefficients by using sign match/mismatch information that indicates a match or mismatch between the sign of the given first frequency coefficient and the sign of a corresponding one of the plurality of second frequency coefficients.