Apparatus, a method and a computer program for video coding and decoding

Abstract

A method comprising: obtaining an image block unit comprising samples in color channels of one or two chrominance channels and one luminance channel (); reconstructing samples of said luminance channels of the image block unit (); predicting samples of at least one color channel of image block unit using a cross-component prediction model based on reconstructed samples on a reference channel, wherein parameters of the cross-component prediction model are determined at least partly based on a plurality of reconstructed chrominance samples and their corresponding reconstructed luminance samples in neighboring image block units (); predicting a plurality of color channel samples in said neighboring image block units co-locating at least part of the reconstructed chrominance and luminance samples using said cross-component prediction model (); determining a difference between values of the predicted plurality of color channel samples in said neighboring image block and corresponding reconstructed color channel samples (); and adjusting the parameters of the cross-component prediction model based on said difference ().