determining at least one reference sample line for intra prediction of a current block among a plurality of reference sample lines by selecting the at least one reference sample line,

wherein based on an upper boundary part of the current block corresponding to an upper boundary part of a current coding tree block including the current block, only a first reference sample line among the plurality of reference sample lines is determined as the at least one reference sample line for intra prediction of the current block,

wherein the first reference sample line includes upper reference samples adjacent to the current block and left reference samples adjacent to the current block,

deriving reference samples for intra prediction of the current block based on the selection of at least one reference sample line; and

performing intra prediction for the current block based on an intra prediction mode and the reference samples,

wherein the performing the intra prediction for the current block comprises:

determining an interpolation filter for the intra prediction between a first interpolation filter and a second interpolation filter; and

performing the intra prediction for the current block based on the interpolation filter,

wherein filter coefficients of the interpolation filter are determined differently depending on whether the determined at least one reference sample line is the first reference sample line,

wherein the interpolation filter is determined further based on the size of the current block, the intra prediction mode of the current block, and a color component of the current block, and

wherein the first interpolation filter is determined as the interpolation filter for the current block in case the selected reference sample line is not the first reference sample line.