Bitstream decoder

Abstract

The present disclosure relates to: a method of decoding, in a decoder, a bitstream representing an image, wherein the bitstream comprises a plurality of blocks of residual samples, and one or more reconstructed image frames of the image are obtained by adding a respective block of residual samples to a combined hypotheses block of intra-predictions, the combined hypotheses block of intra-predictions being formed by applying a method comprising: receiving the bitstream; for each block of residual samples: determining if a combined intra-prediction hypothesis is indicated and/or inferred from the bitstream and, if so: for each block of residual samples of a block for which a combined intra-prediction hypothesis is indicated and/or inferred: determining a first intra-prediction mode from information extracted from the bitstream; determining or inferring at least a second, different, intra-prediction mode; applying the first intra-prediction mode to at least one reference sample to form a first hypothesis prediction sample; applying the at least one second intra-prediction mode to said at least one reference sample to form a second hypothesis prediction sample; and forming a said combined hypotheses block of predictions by combining the first and second hypothesis prediction samples formed for the block.