Encoder, a decoder and corresponding methods for merge mode

A non-transitory computer-readable medium having stored thereon instructions that, when executed by one or more processors, cause the one or more processors to perform operations including:

• constructing a first list according to motion information of neighboring blocks of a current block, wherein the motion information includes the information whether one or two reference picture lists are used, a reference index, and a motion vector for each reference picture list, and wherein the first list is a merge candidate list;
• obtaining prediction information of the current block;
• if the prediction information of the current block indicates that a sub-block prediction is applied to the current block,
• obtaining a uni-prediction candidate for the current block according to the first list;
• and
• using, the uni-prediction candidate for the current block to perform inter prediction of the current block,
• wherein constructing the first list further comprises:
• after checking whether a neighboring block is available and contains the motion information, performing redundancy checks before using the motion information of the neighboring blocks as merge candidates in the first list, wherein the redundancy checks ensure that the merge candidates with same motion information are excluded from the first list, and wherein the redundancy checks include a first redundancy check performed among left, top-right, top, and top-left neighboring blocks, and a second redundancy check performed among left, bottom-left, and top-left neighboring blocks.

A decoder, comprising:

• one or more processors;
• and a non-transitory computer-readable storage medium coupled to the processors and storing instructions for execution by the processors, wherein the instructions, when executed by the processors, causes the decoder to:
• construct a first list according to motion information of neighboring blocks of a current block, wherein the motion information includes the information whether one or two reference picture lists are used, a reference index, and a motion vector for each reference picture list, and wherein the first list is a merge candidate list;
• obtain prediction information of the current block;
• if the prediction information of the current block indicates that a sub-block prediction is applied to the current block,
• obtain a uni-prediction candidate for the current block according to the first list;
• and
• use, the uni-prediction candidate for the current block to perform inter prediction of the current block,
• wherein constructing the first list further comprises:
• after checking whether a neighboring block is available and contains the motion information, performing redundancy checks before using the motion information of the neighboring blocks as merge candidates in the first list, wherein the redundancy checks ensure that the merge candidates with same motion information are excluded from the first list, and wherein the redundancy checks include a first redundancy check performed among left, top-right, top, and top-left neighboring blocks, and a second redundancy check performed among left, bottom-left, and top-left neighboring blocks.