Method and apparatus for intra prediction

An intra-prediction method in which an intra-prediction is performed on a current block, comprising:

• determining whether or not to perform smoothing on a reference pixel of the current block based on a size of a block and an intra-prediction mode for the current block, the size of the block being indicated by an encoder and transmitted to a decoder through a higher layer syntax;
• and
• determining a smoothing method by comparing the size of the current block with the transmitted size of the block,
• wherein the determining of whether or not to perform smoothing on the reference pixel based on the transmitted size of the block and the intra-prediction mode for the current block comprises determining to perform smoothing only in response to each of:
• the size of the current block being 8×8 and the intra-prediction mode for the current block being a No. 2 intra-prediction mode,
• the size of the current block being 8×8 and the intra-prediction mode for the current block being a No. 18 intra-prediction mode,
• the size of the current block being 8×8 and the intra-prediction mode for the current block being a No. 34 intra-prediction mode,
• the size of the current block being 8×8 and the intra-prediction mode for the current block being a planar mode;
• the size of the current block being 16×16 and the intra-prediction mode for the current block being a No. 2 intra-prediction mode to a No. 8 intra-prediction mode,
• the size of the current block being 16×16 and the intra-prediction mode for the current block being a No. 12 intra-prediction mode to a No. 24 intra-prediction mode,
• the size of the current block being 16×16 and the intra-prediction mode for the current block being a No. 28 intra-prediction mode to a No. 34 intra-prediction mode, and
• the size of the current block being 16×16 and the intra-prediction mode for the current block being a planar mode;
• and
• the size of the current block being 32×32 and the intra-prediction mode for the current block being a No. 2 intra-prediction mode to a No. 34 intra-prediction mode, and
• the size of the current block being 32×32 and the intra-prediction mode for the current block being a planar mode other than a No. 10 intra-prediction mode and a No. 26 intra-prediction mode.

An image decoder in which an intra-prediction is performed on a current block, comprising:

• an intra-prediction unit configured to:
• determine whether or not to perform smoothing on a reference pixel of the current block based on a size of a block and an intra-prediction mode for the current block, the size of the block being indicated by an encoder and transmitted to the decoder through a higher layer syntax,
• determine a smoothing method by comparing the size of the current block with the transmitted size of the block,
• in response to the result of comparison between the size of the current block and the transmitted size of the block, determine the smoothing filter to be a bi-linear smoothing filter or a smoothing filter having predetermined filtering coefficients.