1. A video data signal for use in a video coding apparatus for transmitting image information, said video data signal comprising: an encoded video stream including a code string which includes: a synchronization code; a group of coded coding mode information; a group of coded motion vectors; and a group of coded prediction error information, the synchronization code, the group of coded coding mode information, the group of coded motion vectors and the group of coded predicted error information being arranged in this order corresponding to a descending order of importance in decoding.