US Patent 11445183 Chroma intra mode derivation in screen content coding

A method of video processing is described. The method includes deriving, for a current video block of a video that is a chroma block and coded in a chroma DM mode, an intra prediction mode for the current video block according to a rule related to a coding mode of the current video block; and performing a conversion between the current video block and a coded presentation of the video, wherein the rule specifies to derive the intra prediction mode based on an intra prediction direction of a corresponding luma block used to derive the chroma DM mode and coded using a block differential pulse code modulation representation of a quantized residual block corresponding to the current video block.