A method of de-blocking an edge of a block of samples of video data is disclosed. A first prediction mode is decoded for a first block of two adjacent blocks of video data, each of the blocks of video data including a primary color channel and at least one secondary color channel. A second prediction mode is decoded for a second block of the two adjacent blocks of video data. A boundary strength value is determined for a block of samples along an edge corresponding to a boundary between said first block of video data and said second block of video data. A weak de-blocking filter is applied to the block of data along said edge if the determined boundary strength value indicates that the first prediction mode is intra prediction and the second prediction mode is intra-block copy prediction. The weak de-blocking filter is different to a filter applied to a block determined to have two, adjacently located, intra prediction mode blocks.