Inter-frame prediction method based on merge with motion vector difference (MMVD) mode, video coding method, related device and apparatus

An inter-frame prediction method based on a merge with motion vector difference (MMVD) mode, comprising:

• constructing a first candidate list of a current coding block in the MMVD mode, wherein the first candidate list comprises a first preset number of first candidate motion vectors (MVs);
• and
• each of the first preset number of first candidate MVs comprises two sub-MVs corresponding to two directions respectively;
• determining a second preset number of motion search amplitudes and a third preset number of motion search directions;
• taking at least one sub-MV of each first candidate MV as a starting point, and searching by different motion combinations of the motion search amplitudes and the motion search directions, to obtain a MV offset of the corresponding one first candidate MV under the different motion combinations, wherein the MV offset of the corresponding one first candidate MV comprises offsets of the two sub-MVs corresponding to the two directions;
• determining to obtain an optimal MV of the current coding block based on the MV offset of each of the first candidate MVs in the different motion combinations.

An inter-frame prediction apparatus based on a merge with motion vector difference (MMVD) mode, comprising:

• a processor and a memory coupled to each other;
• wherein the memory is configured to store a program;
• and the processor is configured to execute operations comprising:
• constructing a first candidate list of a current coding block in the MMVD mode, wherein the first candidate list comprises a first preset number of first candidate motion vectors (MVs);
• determining a second preset number of motion search amplitudes and a third preset number of motion search directions;
• taking each of the first preset number of first candidate MVs as a starting point, and searching by different motion combinations of the motion search amplitudes and the motion search directions, to obtain a MV offset of each first candidate MV under the different motion combinations;
• determining to obtain an optimal MV of the current coding block based on the MV offset of each of the first candidate MVs in the different motion combinations;
• wherein, the first preset number, the second preset number, and the third preset number are integers;
• and the first preset number, the second preset number, and the third preset number are satisfied at least one of the following:
• the first preset number being greater than 2, the second preset number being greater than 6, the third preset number being greater than 4, and an index value of the motion search direction used by the first candidate MVs being related to the corresponding first candidate MVs;
• and
• for each of the first candidate MVs, the more the motion search direction is related to the first candidate MV, the smaller the index value of the motion search direction is.