Encoder, a decoder and corresponding methods using IBC merge list

A method for constructing a candidate merge list for Intra block copy (IBC) mode, the method comprising:

• inserting a block vector of a neighboring block of a current block into an initial merge list of the current block, when the neighboring block is available and the neighboring block is using an IBC mode;
• inserting a block vector of a last candidate in a history based motion vector predictor (HMVP) into the initial merge list subsequently after the block vector of the neighboring block, when the block vector of the neighboring block is not identical to the block vector of the last candidate in the HMVP;
• and
• inserting a block vector of another candidate in the HMVP into the initial merge list, wherein pruning for the block vector of another candidate in the HMVP is removed.

A method for constructing a candidate merge list for Intra block copy (IBC) mode, the method comprising:

• inserting a block vector of a left neighboring block of a current block into an initial merge list of the current block, when the left neighboring block is available and the left neighboring block is using an IBC mode;
• inserting a block vector of an above neighboring block of the current block into the initial merge list, when the above neighboring block is available, the above neighboring block is using the IBC mode and the block vector of the above neighboring block is not identical to the block vector of the left neighboring block;
• inserting a block vector of a last candidate in a history based motion vector predictor (HMVP) into the initial merge list subsequently after the block vector of the left neighboring block or the above neighboring block, when the block vector of the above neighboring block is not identical to the block vector of the last candidate in the HMVP and when the block vector of the left neighboring block is not identical to the block vector of the last candidate in the HMVP;
• and
• inserting a block vector of another candidate in the HMVP into the initial merge list, wherein pruning for the block vector of another candidate in the HMVP is removed.