A method of filtering reconstructed video data is disclosed. The method comprising: inputting reconstructed luma component sample values; deriving a filtered sample value by using cross component filter coefficients and the reconstructed luma component sample values prior to an adaptive loop filtering process; deriving a refinement value for chroma components by using the filtered sample value; and deriving a refined chroma sample value by using a sum of a sample value of chroma components and the refinement value for chroma components.