Techniques, devices, and systems for video processing are described. In one example aspect, a video processing method includes determining, for a conversion between a block of a video and a bitstream representation of the video, a manner in which information for a Matrix-based Intra Prediction (MIP) coding technique is coded in the bitstream representation. A prediction block of the block is determined using the MIP coding technique based on performing a matrix vector multiplication operation on previously coded samples of the video. The method also includes performing the conversion based on the determining.