1. A decoder comprising: an input receiving moving image data in encoded form, including a plurality of frames in which a region is encoded using motion estimation, the moving image data including a respective set of motion vector values associated with each respective one of the frames or with each respective region within each of the frames, each of the motion vector values of each respective frame or region is included in a motion vector field in an encoded bitstream, the moving image data further including at least one respective indicator in header information associated with each of the respective frames or regions indicating whether the respective motion vector values are encoded at a first resolution or a second resolution, the motion vector field having a reduced size for the frames or the regions having the motion vector values encoded at the second resolution relative to a size of the frames or the regions having the motion vector values encoded at the first resolution, and the moving image data including a setting to set whether the first resolution or the second resolution of the motion vector values is being indicated per region or per frame; and a motion prediction module decoding the frames or regions based on the motion vector values, the decoding comprising: reading each of the indicators from the header information; reading the setting and interpreting the motion vector values accordingly; determining, from the read indicators, whether the motion vector values of the respective frame or region are encoded at the first resolution or the second resolution; and interpreting the motion vector values in units of fractional pixels for the indicated first resolution or in units of integer pixels responsive for the indicated second resolution.