Video coding method and device, video decoding method and device
Provided are image decoding/encoding methods and apparatuses for increasing coding efficiency and reducing complexity while using a flexible tree split. The image decoding method includes: obtaining, from a bitstream, a bin string corresponding to a split shape mode of a coding unit; determining a split rule of the coding unit; and splitting the coding unit into a plurality of coding units, based on at least one of the split rule and the bin string corresponding to the split shape mode, wherein the determining of the split rule includes: determining an allowable first range of a size of the coding unit according to a ratio of a width and a height of the coding unit; and determining an allowable second range of the size of the coding unit according to the split shape mode of the coding unit.
1. An image decoding method comprising:
obtaining, from a bitstream, a bin string corresponding to a split shape mode of a coding unit, the split shape mode being which split type of the coding unit is allowable among a quad split type, a binary split type and a tri split type;
obtaining, from the bitstream, information about an allowable range of a length of a long side of a coding unit, a width and a height of which has a 1:4 ratio;
determining an allowable maximum length of the long side of the coding unit with the 1:4 ratio, based on the information about the allowable range of the length of long side of the coding unit with the 1:4 ratio;
determining an allowable minimum length of the long side of the coding unit with the 1:4 ratio;
splitting the coding unit into two or three coding units when the split type of the coding unit is allowed to be the binary split type or the tri split type according to the split shape mode, and when it is determined that the coding unit is allowed to be split into two or three coding units based on the allowable maximum length of the long side of the coding unit with the 1:4 ratio and the allowable minimum length of the long side of the coding unit with the 1:4 ratio; and
decoding the two or three coding units when the two or three coding units are not further split into smaller coding units.
2. An image encoding method comprising:
determining an allowable maximum length of a long side of a coding unit, a width and a height of which has a 1:4 ratio;
determining an allowable minimum length of the long side of the coding unit with the 1:4 ratio:
determining a split shape mode of a coding unit, the split shape mode being which split type of the coding unit is allowable among a quad split type, a binary split type and a tri split type;
encoding two or three coding units split from the coding unit when the split type of the coding unit is allowed to be the binary split type or the tri split type, and it is determined that the coding unit is allowed to be split into two or three coding units based on the allowable maximum length of the long side of the coding unit with the 1:4 ratio and the allowable minimum length of the long side of the coding unit with the 1:4 ratio;
generating information about an allowable range of a length of long side of the coding unit with the 1:4 ratio based on the allowable maximum length of a long side of the coding unit with the 1:4 ratio; and
generating a bin string corresponding to the split shape mode of the coding unit.