An apparatus of decoding video data, comprising: a prediction mode decoding unit (250, 320) configured to derive a luma intra prediction mode and a chroma intra prediction mode; a prediction size determining unit configured to determine a size of a luma transform unit and a size of a chroma transform unit using transform size information; a reference pixel generating unit configured to generate referential pixels if at least one reference pixel is unavailable; a reference pixel filtering unit configured to adaptively filter the reference pixels of a current luma block based on the luma intra prediction mode and the size of the luma transform unit, and not to filter the reference pixels of a current chroma block; a prediction block generating unit configured to generate prediction blocks of the current luma block and the current chroma block; a residual bock generating unit (210, 220, 230, 240) configured to generate a luma residual block and a chroma residual block, and an adder which adds the generated residual block and the generated prediction block to generate a reconstructed block, wherein the luma intra prediction mode is derived using a most probable mode, MPM, group including three intra prediction modes, a mode group indicator and a luma prediction mode index, when only one of a left intra prediction mode and an above intra prediction mode of a current luma prediction unit is available and if the available intra prediction mode is a non-directional mode, the three intra prediction modes in MPM group are planar mode, DC mode and vertical mode, and when only one of a left intra prediction mode and an above intra prediction mode of a current luma prediction unit is available and if the available intra prediction mode is a directional mode, the three intra prediction modes in MPM group are planar mode, DC mode and the available intra prediction mode. a prediction mode decoding unit (250, 320) configured to derive a luma intra prediction mode and a chroma intra prediction mode; a prediction size determining unit configured to determine a size of a luma transform unit and a size of a chroma transform unit using transform size information; a reference pixel generating unit configured to generate referential pixels if at least one reference pixel is unavailable; a reference pixel filtering unit configured to adaptively filter the reference pixels of a current luma block based on the luma intra prediction mode and the size of the luma transform unit, and not to filter the reference pixels of a current chroma block; a prediction block generating unit configured to generate prediction blocks of the current luma block and the current chroma block; a residual bock generating unit (210, 220, 230, 240) configured to generate a luma residual block and a chroma residual block, and an adder which adds the generated residual block and the generated prediction block to generate a reconstructed block, wherein the luma intra prediction mode is derived using a most probable mode, MPM, group including three intra prediction modes, a mode group indicator and a luma prediction mode index, when only one of a left intra prediction mode and an above intra prediction mode of a current luma prediction unit is available and if the available intra prediction mode is a non-directional mode, the three intra prediction modes in MPM group are planar mode, DC mode and vertical mode, and when only one of a left intra prediction mode and an above intra prediction mode of a current luma prediction unit is available and if the available intra prediction mode is a directional mode, the three intra prediction modes in MPM group are planar mode, DC mode and the available intra prediction mode.