Methods for encoding and decoding pictures and associated apparatus

A method for encoding a picture, comprising:

• determining a width and a height of a coding block in the picture;
• if the width and the height are equal to N, wherein N is a positive integer power of 2, determining a matrix-based intra prediction (MIP) size identifier indicating that an MIP prediction size equal to N;
• deriving a group of reference samples of the coding block;
• and
• deriving an MIP prediction of the coding block based on the group of reference samples and an MIP matrix according to the MIP size identifier by:
• deriving the MIP prediction of the coding block based on following equations:
• oW=(1<<(sW−1))−fO*(Σi=0inSize-1p[i]), and
• predMip[x][y]=(((Σi=0inSize-1mWeight[i][y*predSize+x]*p[i])+oW)>>sW)+pTemp[0](for x from 0 to “predSize-1”, for y from 0 to “predSize-1”),
• wherein “sW” represents a shifting number parameter, “fO” represents a shifting offset parameter, “oW” represents a parameter based on the shifting offset parameter and the shifting number parameter, “inSize” represents a variable indicating the number of reference samples used in deriving the MIP prediction, “p[i]” represents a reference sample, “predMip[x][y]” represents the MIP prediction, “mWeight[i][j]” represents an MIP weighting matrix, “predSize” represents a size of the MIP prediction, “pTemp[0]” represents the 0-th value in a reference sample buffer, symbol “<<” represents a binary left shifting operator, and symbol “>>” represents a binary right shifting operator;
• determining the shifting offset parameter;
• and
• deriving the MIP prediction of the coding block based on the group of reference samples, the shifting offset parameter, and the MIP matrix according to the MIP size identifier, wherein different MIP size identifiers correspond to the same shifting offset parameter, and the shifting offset parameter is a constant equal to 32.

A decoder for decoding a picture, comprising:

• a processor;
• and
• a memory storing one or more computer programs which, when executed by the processor, cause the processor to:
• parse a bitstream to determine a width, a height and a prediction mode of a coding block;
• and
• when the prediction mode indicates a matrix-based intra prediction (MIP) mode is used in decoding the coding block, determine an MIP size identifier indicating that an MIP prediction size equal to N, if the width and the height are equal to N, wherein N is a positive integer power of 2, and wherein the processor is configured to derive a group of reference samples of the coding block, and wherein the processor is configured to derive an MIP prediction of the coding block based on the group of reference samples and an MIP matrix corresponding to the MIP size identifier by:
• deriving the MIP prediction of the coding block based on following equations:
• oW=(1<<(sW−1))−fO*(Σi=0inSize-1p[i]), and
• predMip[x][y]=(((Σi=0inSize-1mWeight[i][y*predSize+x]*p[i])+oW)>>sW)+pTemp[0](for x from 0 to “predSize-1”, for y from 0 to “predSize-1”),
• wherein “sW” represents a shifting number parameter, “fO” represents a shifting offset parameter, “oW” represents a parameter based on the shifting offset parameter and the shifting number parameter, “inSize” represents a variable indicating the number of reference samples used in deriving the MIP prediction, “p[i]” represents a reference sample, “predMip[x][y]” represents the MIP prediction, “mWeight[i][j]” represents an MIP weighting matrix, “predSize” represents a size of the MIP prediction, “pTemp[0]” represents the 0-th value in a reference sample buffer, symbol “<<” represents a binary left shifting operator, and symbol “>>” represents a binary right shifting operator;
• determining the shifting offset parameter;
• and
• deriving the MIP prediction of the coding block based on the group of reference samples, the shifting offset parameter, and the MIP matrix according to the MIP size identifier, wherein different MIP size identifiers correspond to the same shifting offset parameter, and the shifting offset parameter is a constant equal to 32.

An encoder for encoding a picture, comprising:

• a processor;
• and
• a memory storing one or more computer programs which, when executed by the processor, cause the processor to:
• receive an input picture and divide the input picture into one or more coding blocks;
• determine a width and a height of the coding block, wherein if the width and the height are equal to N, the processor is configured to determine a matrix-based intra prediction (MIP) size identifier indicating that an MIP prediction size equal to N, wherein N is a positive integer power of 2, and wherein the processor is configured to derive a group of reference samples of the coding block, and wherein the processor is configured to derive an MIP prediction of the coding block based on the group of reference samples and an MIP matrix according to the MIP size identifier by:
• deriving the MIP prediction of the coding block based on following equations:
• oW=(1<<(sW−1))−fO*(Σi=0inSize-1p[i]), and
• predMip[x][y]=(((Σi=0inSize-1mWeight[i][y*predSize+x]*p[i])+oW)>>sW)+pTemp[0](for x from 0 to “predSize-1”, for y from 0 to “predSize-1”),
• wherein “sW” represents a shifting number parameter, “fO” represents a shifting offset parameter, “oW” represents a parameter based on the shifting offset parameter and the shifting number parameter, “inSize” represents a variable indicating the number of reference samples used in deriving the MIP prediction, “p[i]” represents a reference sample, “predMip[x][y]” represents the MIP prediction, “mWeight[i][j]” represents an MIP weighting matrix, “predSize” represents a size of the MIP prediction, “pTemp[0]” represents the 0-th value in a reference sample buffer, symbol “<<” represents a binary left shifting operator, and symbol “>>” represents a binary right shifting operator;
• and
• determining the shifting offset parameter;
• and
• deriving the MIP prediction of the coding block based on the group of reference samples, the shifting offset parameter, and the MIP matrix according to the MIP size identifier, wherein different MIP size identifiers correspond to the same shifting offset parameter, and the shifting offset parameter is a constant equal to 32;
• and
• transform parameters to derive the MIP prediction into a bitstream.