Encoder, a decoder and corresponding methods of intra prediction

A method of coding implemented by a decoding device, comprising:

• obtaining a bitstream for a current block;
• obtaining a value of a Matrix-based Intra Prediction (MIP) indication information for luma component of the current block according to the bitstream;
• and
• performing chroma mode derivation process for the current block,
• wherein a corresponded luma intra predicting mode for the current block is set to Planar mode, when the value of the MIP indication information indicate that the current block is predicted using a Matrix-based Intra Prediction, the corresponded luma intra predicting mode is derived from a position in luma component (xCb+cbWidth/2, yCb+cbHeight/2), wherein (xCb, yCb) specifying a top-left sample for chroma component of the current block relative to a top left luma sample of a current picture, cbWidth specifying a width of the current block in luma samples, and cbHeight specifying a height of the current block in luma samples.

A decoder, comprising:

• one or more processors;
• and
• a non-transitory computer-readable storage medium coupled to the one or more processors and storing programming for execution by the one or more processors, wherein the programming, when executed by the one or more processors, configures the decoder to carry out the operation of:
• setting a value of candidate intra prediction mode of a current block to be a default value, wherein the current block is predicted using an intra prediction mode but not a Matrix-based Intra Prediction (MIP) mode and a neighboring block adjacent to the current block is used to derive the value of candidate intra prediction mode of the current block and is predicted using the MIP mode, the default value corresponding to a non-angular intra mode;
• and
• obtaining a value of the intra prediction mode of the current block according to the default value.