A method and system for video system using coding modes including an Inter prediction mode and an Intra Block Copy (IntraBC) mode are disclosed. A syntax element in a bitstream is determined to indicate whether two versions of a reconstructed current image unit are needed. If two versions of the reconstructed current image unit are needed, a loop-filtered version of the reconstructed current image unit and a non-loop-filter version of the reconstructed current image unit are allowed to be stored and used as reference data. Otherwise, only one version of the reconstructed current image unit is stored as the reference data. According to another method, bi-prediction mode is converted to uni-prediction mode for a certain prediction mode, where the bandwidth exceeds the existing worst case.