A method of filtering reconstructed video data is disclosed. The method comprising: parsing a first syntax element used for setting cross-component filter coefficients; inputting a reconstructed luma picture sample array; deriving luma locations by using location corresponding to a current chroma sample; deriving a filter coefficient array by using the cross-component filter coefficients; deriving a variable by using the filter coefficient array and the reconstructed luma picture sample array defined by the luma locations; and deriving a scaled variable by using the variable, wherein the variable is modified by a sum of a sample of a current chroma block, which is defined by a predetermined location, and the scaled variable.