Method and apparatus for encoding video, and method and apparatus for decoding video

A method of decoding an image, the method comprising:

• extracting information that indicates an intra prediction mode applied to a current block to be decoded, from a bitstream;
• determining one of neighboring pixels adjacent to the current block and filtered neighboring pixels filtered from the neighboring pixels as reference pixels, based on at least one of a size of the current block and an intra prediction mode of the current block;
• performing intra prediction on the current block using the extracted information and the determined reference pixels,
• wherein, when the current block has a size of N×N, where N is integer, the neighboring pixels include 2N neighboring pixels adjacent to an upper side and an upper right side of the current block and 2N neighboring pixels adjacent to a left side and a below left side of the current block,
• wherein the image is split into a plurality of maximum coding units, according to information about a maximum size of a coding unit,
• a maximum coding unit among the plurality of maximum coding units is hierarchically split into one or more coding units of depths according to split information,
• a coding unit of a current depth is one of rectangular data units split from a coding unit of an upper depth,
• when the split information indicates a split for the current depth, the coding unit of the current depth is split into coding units of a lower depth, independently from neighboring coding units, and the coding unit of the current depth is split into at least one prediction unit.