Method and device for encoding and decoding video

A video decoding method comprising:

• receiving, from a bitstream, partition type information indicating a partition type of a current coding unit;
• determining a size of a current prediction unit in the current coding unit based on the partition type information;
• obtaining, when the size of the current prediction unit is equal to a predetermined size, motion prediction mode information indicating a single prediction mode for the current prediction unit among a plurality of prediction modes including only an L0 prediction mode and an L1 prediction mode;
• obtaining, when the size of the current prediction unit is not equal to the predetermined size, the motion prediction mode information indicating the single prediction mode for the current prediction unit among a plurality of prediction modes including the L0 prediction mode, the L1 prediction mode, and a Bi prediction mode;
• and
• performing an inter-prediction according to the single prediction mode indicated by the motion prediction mode information,
• wherein, when the size of the current prediction unit is equal to the predetermined size, the plurality of prediction modes do not include the Bi prediction mode,
• wherein the single prediction mode is determined depending on the determined size of the current prediction unit,
• wherein the predetermined size of the current prediction unit is 4×8 or 8×4,
• wherein a maximum coding unit is hierarchically split into at least one coding unit of depths according to split information,
• a coding unit of a current depth is one of rectangular data units split from a coding unit of an upper depth among the at least one coding unit of depths,
• when the split information indicates a split of the coding unit of the current depth, the coding unit of the current depth is split into coding units of a lower depth, independently from neighboring coding units, and
• when the split information indicates a non-split of the coding unit of the current depth, at least one prediction unit comprising the current prediction unit is obtained from the coding unit of the current depth based on the partition type information.