A video processing method comprises receiving input data of a current block, checking if the current block satisfies one or more predefined criteria, setting the current block to be a root block if the current block satisfies the predefined criteria, one or more color components of one or more blocks in the current block are not checked with the predefined criteria if the current block is a root block, encoding or decoding the one or more color components of one or more blocks in the current block using neighboring reconstructed samples of the one or more color components of the current block as reference samples if the current block is a root block. Each block in the current block is encoded or decoded using neighboring reconstructed samples of each block in the current block as reference samples if the current block is not a root block.