Video encoding method, video decoding method, video encoding apparatus, video decoding apparatus, and programs thereof

A video decoding method using inter-frame prediction with motion compensation of fractional-accuracy, the method comprising:

• a step of decoding information on division into regions from encoded data;
• a step of performing a region classification on a block-by-block basis based on encoding information obtained by performing decoding on the encoded data;
• a step of performing a divided region redefinition process in which a region dividing line in a horizontal direction, a region dividing line in a vertical direction, or both the region dividing line in the horizontal direction and the region dividing line in the vertical direction are shifted based on a result of the region classification, and a region dividing line with which density of blocks belonging to a particular region classification is greater than or equal to a predetermined threshold value is determined;
• a step of switching an interpolation method of a fractional-accuracy pixel for each of divided regions divided by the region dividing line;
• a step of performing interpolation of the fractional-accuracy pixel for each of the divided regions;
• and
• a step of decoding a picture using inter-frame prediction with motion compensation of fractional-accuracy for an interpolated picture.

A video encoding apparatus using inter-frame prediction with motion compensation of fractional-accuracy, the apparatus comprising:

• an encoding information acquiring unit which acquires encoding information for each block which is a unit of encoding or prediction;
• a region classification unit which performs a region classification on a block-by-block basis based on the acquired encoding information;
• a divided region redefinition processing unit which performs a divided region redefinition process in which a region dividing line in a horizontal direction, a region dividing line in a vertical direction, or both the region dividing line in the horizontal direction and the region dividing line in the vertical direction are shifted based on a result of the region classification, and a region dividing line with which density of blocks belonging to a particular region classification is greater than or equal to a predetermined threshold value is determined;
• an interpolation method switching unit which switches an interpolation method of a fractional-accuracy pixel for each of divided regions divided by the region dividing line;
• an interpolation performing unit which performs interpolation of the fractional-accuracy pixel for each of the divided regions;
• a picture encoding unit which encodes a picture using inter-frame prediction with motion compensation of fractional-accuracy for an interpolated picture;
• and
• a region classification information encoding unit which encodes information on the region classification.

A video decoding apparatus using inter-frame prediction with motion compensation of fractional-accuracy, the apparatus comprising:

• a divided region information decoding unit which decodes information on division into regions from encoded data;
• a region classification unit which performs a region classification on a block-by-block basis based on encoding information obtained by performing decoding on the encoded data;
• a divided region redefinition processing unit which performs a divided region redefinition process in which a region dividing line in a horizontal direction, a region dividing line in a vertical direction, or both the region dividing line in the horizontal direction and the region dividing line in the vertical direction are shifted based on a result of the region classification, and a region dividing line with which density of blocks belonging to a particular region classification is greater than or equal to a predetermined threshold value is determined;
• an interpolation method switching unit which switches an interpolation method of a fractional-accuracy pixel for each of divided regions divided by the region dividing line;
• an interpolation performing unit which performs interpolation of the fractional-accuracy pixel for each of the divided regions;
• and
• a picture decoding unit which decodes a picture using inter-frame prediction with motion compensation of fractional-accuracy for an interpolated picture.