Method and apparatus for encoding and decoding video based on first sub-pixel unit and second sub-pixel unit

A video encoding apparatus comprising:

• a motion estimator which performs motion estimation on a current block according to a first sub-pixel unit, and obtains a motion vector in the first sub-pixel unit with respect to the current block;
• a motion compensator which interpolates a reference picture indicated by the obtained motion vector according to a second sub-pixel unit smaller than the first sub-pixel unit, which selects, by using the interpolated reference picture, selecting a second sub-pixel from among sub-pixels in the second sub-pixel unit adjacent to a first sub-pixel in the first sub-pixel unit of the reference picture indicated by the obtained motion vector, and which selects a corresponding region that has a smaller error with the current block from among a first corresponding region and a second corresponding region, wherein the first corresponding region is of the reference picture indicated by the obtained motion vector and is obtained with respect to the first sub-pixel in the first sub-pixel unit, and the second corresponding region is of the current block and is obtained with respect to the selected second sub-pixel in the second sub-pixel unit;
• and
• an encoder which encodes information of the selected corresponding region,
• wherein:
• the current block is comprised in an image;
• the image is hierarchically split from a plurality of maximum coding units according to the information about a maximum size of a coding unit into coding units of coded depths according to depths;
• wherein a coding unit of a current depth is one of rectangular data units split from a coding unit of a upper depth;
• wherein the coding unit of a current depth are split into coding units of a lower depth, independently from neighboring coding units;
• and
• wherein the coding units of a hierarchical structure comprise encoded coding units among the coding units split from the maximum coding unit.

A method of decoding video, the method comprising:

• decoding and obtaining a motion vector in a first sub-pixel unit with respect to a current block from a bitstream;
• obtaining information from the bitstream, wherein the information indicates whether motion compensation is performed on the current block by using a corresponding region obtained with respect to a second sub-pixel in a second sub-pixel unit that is smaller than the first sub-pixel unit adjacent to a first sub-pixel in the first sub-pixel unit of a reference picture indicated by the obtained motion vector in the first sub-pixel unit;
• if the motion compensation is performed on the current block by using information of the corresponding region obtained with respect to the second sub-pixel in the second sub-pixel unit, extracting position information of the second sub-pixel in the second sub-pixel unit from the bitstream;
• and
• performing the motion compensation on the current block by using the motion vector in the first sub-pixel unit, and the extracted position information of the second sub-pixel in the second sub-pixel unit,
• wherein:
• the current block is comprised in an image;
• the image is hierarchically split from a plurality of maximum coding units according to the information about a maximum size of a coding unit into coding units of coded depths according to depths;
• wherein a coding unit of a current depth is one of rectangular data units split from a coding unit of a upper depth;
• wherein the coding unit of a current depth are split into coding units of a lower depth, independently from neighboring coding units;
• and
• wherein the coding units of a hierarchical structure comprise encoded coding units among the coding units split from the maximum coding unit.

A video decoding apparatus comprising:

• an entropy decoder which decodes and obtains a motion vector in a first sub-pixel unit with respect to a current block from a bitstream, which obtains information indicating whether motion compensation is performed on the current block by using a corresponding region obtained with respect to a second sub-pixel in a second sub-pixel unit that is smaller than the first sub-pixel unit adjacent to a first sub-pixel in the first sub-pixel unit of a reference picture indicated by the obtained motion vector in the first sub-pixel unit, and which, if the motion estimation is performed on the current block by using information of the corresponding region obtained with respect to the second sub-pixel in the second sub-pixel unit, extracts position information of the second sub-pixel in the second sub-pixel unit from the bitstream;
• and
• a motion compensator which performs the motion compensation on the current block by using the motion vector in the first sub-pixel unit, and the extracted position information of the second sub-pixel in the second sub-pixel unit,
• wherein:
• the current block is comprised in an image;
• the image is hierarchically split from a plurality of maximum coding units according to the information about a maximum size of a coding unit into coding units of coded depths according to depths;
• wherein a coding unit of a current depth is one of rectangular data units split from a coding unit of a upper depth;
• wherein the coding unit of a current depth are split into coding units of a lower depth, independently from neighboring coding units;
• and
• wherein the coding units of a hierarchical structure comprise encoded coding units among the coding units split from the maximum coding unit.