Intra prediction method and apparatus using the method

An intra prediction method, by a decoding apparatus, comprising:

• obtaining information on a prediction mode from a bitstream;
• determining an intra prediction mode for a current block based on the information on the prediction mode;
• deriving neighboring samples of the current block;
• and
• generating a prediction sample of the current block based on the intra prediction mode and 4 samples among the neighboring samples,
• wherein the 4 samples include a first sample located in a same column with the prediction sample, a second sample located in a right side of the first sample, a third sample located in a same row with the prediction sample, and a fourth sample located in a lower side of the third sample,
• wherein the second sample is located in a right side of a right-most sample among neighboring samples adjacent to an upper boundary of the current block, and
• wherein the fourth sample is located in a lower side of a lowest sample among neighboring samples adjacent to a left boundary of the current block.

A decoding apparatus performing intra prediction, comprising:

• an entropy decoding module for obtaining information on a prediction mode from a bitstream;
• and
• a prediction module for determining an intra prediction mode for a current block based on the information on the prediction mode, for deriving neighboring samples of the current block, and for generating a prediction sample of the current block based on the intra prediction mode and 4 samples among the neighboring samples,
• wherein the 4 samples include a first sample located in a same column with the prediction sample, a second sample located in a right side of the first sample, a third sample located in a same row with the prediction sample, and a fourth sample located in a lower side of the third sample,
• wherein the second sample is located in a right side of a right-most sample among neighboring samples adjacent to an upper boundary of the current block, and
• wherein the fourth sample is located in a lower side of a lowest sample among neighboring samples adjacent to a left boundary of the current block.