Encoding/decoding method and apparatus with vector derivation mode

A method of decoding for a video image, comprising:

• determining an optimal merged candidate block for a current block based on an index value of the optimal merged candidate block in an encoded bit stream which is received from an encoder and obtained by the encoder using a motion vector merging technology, wherein a motion vector of the optimal merged candidate block is closest to and used as a substitute of a motion vector for the current block in the motion vector merging technology;
• based on one or a combination of a prediction direction of the optimal merged candidate block and an instruction flag which is carried in the encoded bit stream and is for instructing a decoder to use a motion vector derivation mode or not, determining whether to use the motion vector derivation mode;
• determining, based on the prediction direction of the optimal merged candidate block, the motion vector derivation mode that needs to be used;
• correcting the motion vector of the current block based on the determined motion vector derivation mode;
• and
• decoding the current block based on the corrected motion vector and a residual carried in the encoded bit stream.

An encoding apparatus for a video image, comprising:

• at least one hardware processor;
• a memory including instructions to control the at least one hardware processor to:
• determine an optimal merged candidate block for a current block based on a motion vector merging technology, wherein a motion vector of the optimal merged candidate block is closest to and used as a substitute of a motion vector for the current block in the motion vector merging technology;
• based on one or a combination of a prediction direction of the optimal merged candidate block and an instruction flag which is carried in an encoded bit stream and is for instructing a decoder to use a motion vector derivation mode or not, determining whether to use the motion vector derivation mode;
• determine, based on the prediction direction of the optimal merged candidate block, the motion vector derivation mode that needs to be used by a decoder;
• correct the motion vector of the current block based on the motion vector derivation mode;
• determine a residual between a predicted value of the current block and an original value of the current block based on the corrected motion vector, wherein the predicted value of the current block is based on the corrected motion vector;
• and
• encode the residual and an index value of the optimal merged candidate block into an encoded bit stream transmitted to the decoder.

A decoding apparatus for a video image, comprising:

• at least one hardware processor;
• a memory including instructions to control the at least one hardware processor to:
• determine an optimal merged candidate block for a current block based on an index value of the optimal merged candidate block in an encoded bit stream which is received from an encoder and obtained by the encoder using a motion vector merging technology, wherein a motion vector of the optimal merged candidate block is closest to and used as a substitute of a motion vector for the current block in the motion vector merging technology;
• based on one or a combination of a prediction direction of the optimal merged candidate block and an instruction flag which is carried in the encoded bit stream and is for instructing a decoder to use a motion vector derivation mode or not, determine whether to use the motion vector derivation mode;
• determine, based on the prediction direction of the optimal merged candidate block, the motion vector derivation mode that needs to be used;
• correct the motion vector of the current block based on the determined motion vector derivation mode;
• and
• decode the current block based on the corrected motion vector and a residual carried in the encoded bit stream.