Encoder, decoder and corresponding methods of boundary strength derivation of deblocking filter

An encoder, comprising:

• one or more processors;
• and
• a computer-readable medium communicatively coupled to the one or more processors, wherein the computer-readable medium stores instructions, which when executed by the one or more processors, cause the encoder to:
• determine whether at least one of two blocks of an image in a video is predicted with a combined inter-intra prediction (CIIP), wherein the two blocks include a first block and a second block, and a boundary exists between the first block and the second block;
• set a boundary strength (Bs) for the boundary to a first value when the at least one of the two blocks is predicted with the CIIP, wherein the first value is 2;
• and
• encode a flag into a video bitstream, wherein the flag is used to indicate whether at least one of the two blocks is predicted with the CIIP.

A non-transitory computer-readable medium storing computer instructions, that when executed by one or more processors of a processing device, cause the processing device to perform operations comprising:

• determining whether at least one of two blocks of an image in a video is predicted with a combined inter-intra prediction (CIIP), wherein the two blocks include a first block and a second block, and a boundary exists between the first block and the second block;
• setting a boundary strength (Bs) for the boundary to a first value when the at least one of the two blocks is predicted with the CIIP, wherein the first value is 2;
• and
• encoding a flag into a video bitstream, wherein the flag is used to indicate whether at least one of the two blocks is predicted with the CHIP.