US Patent 11943444 Restricted upsampling process in matrix-based intra prediction

A method for video processing includes performing a conversion between a current video block of a video and a bitstream representation of the current video block using a matrix based intra prediction (MIP) mode, where the conversion includes performing the upsampling operation in which the final prediction block is determined by using a reduced prediction block of the current video block and by using reconstructed neighboring samples of the current video block according to a rule, and where the reduced prediction block is obtained by performing the matrix vector multiplication operation on reduced boundary samples of the current video block.