A method and a video decoder for decoding an encoded bitstream of video data in a picture encoding and decoding system are disclosed. The video decoder includes a motion compensation unit for calculating a position for a sample image portion using an encoded bitstream of video data having a motion vector and rounding information. The calculated position of a sample image is rounded with the rounding information. The rounding information indicates the accuracy for rounding, and it is decoded from the bitstream. An image reconstruction unit reconstructs a decoded image portion of the video data from the sample image portion.