Video encoder, video decoder, video encoding method, video decoding method, and video encoding and decoding system

A video decoder for decoding an encoded bitstream of video data, comprising:

• a motion compensation unit including an image transformation unit for transforming a reference image portion into a transformed image portion using the transformation specified by at least one motion parameter decoded from an input bitstream;
• an image reconstruction unit for reconstructing a decoded image portion using a decoded data and said transformed image portion;
• and
• wherein the at least one motion parameter consists of plural motion vectors, a transformation pattern information and a round-up information, and the image transformation unit transforms the reference image portion comprised of half-pels as well as integer pels into the transformed image portion by indicating addresses according to the following process:
• 1) calculate addresses with plural motion vectors according to the transformation pattern information,
• 2) round up calculated addresses with the round-up information.