Methods for decoding of a video bitstream by a video decoding circuit are provided. In one implementation, a method receives coded data for a 2N×2N coding unit (CU) from the video bitstream, selects one or more first codewords according to whether asymmetric motion partition is disabled or enabled when a size of said 2N×2N CU is not equal to a smallest CU size, wherein none of the first codewords corresponds to INTER N×N partition, selects one or more second codewords when the size of said 2N×2N CU is equal to the smallest CU size, wherein none of the second codewords corresponds to the INTER N×N partition when N is 4, determines a CU structure for said 2N×2N CU from the video bitstream using said one or more first codewords or said one or more second codewords, and decodes the video bitstream using the CU structure.