Method and apparatus for performing intra-prediction using adaptive filter
Provided is a method and apparatus for performing intra-prediction using an adaptive filter. The method for performing intra-prediction includes the steps of: determining whether or not to apply a first filter for a reference pixel value on the basis of information of a neighboring block of a current block; applying the first filter for the reference pixel value when it is determined to apply the first filter; performing intra-prediction on the current block on the basis of the reference pixel value; determining whether or not to apply a second filter for a prediction value according to each prediction mode of the current block, which is predicted by the intra-prediction performance on the basis of the information of the neighboring block; and applying the second filter for the prediction value according to each prediction mode of the current block when it is determined to apply the second filter.
1. A video decoding method, comprising:
determining whether to apply a first filter to a reference pixel value of a current block based on at least one of an intra prediction mode of the current block or a size of the current block;
deriving a prediction value of the current block using the reference pixel value; and
determining whether to apply a second filter for the prediction value of the current block based on at least one of the intra prediction mode of the current block or the size of the current block, for thereby producing a filtered prediction value,
wherein when the intra prediction mode of the current block is a DC mode, the filtered prediction value is generated by applying a 3-tap filter for an upper-leftmost pixel among prediction pixels of the current block and applying a 2-tap filter for remaining pixels indicating uppermost pixels and leftmost pixels except the upper-leftmost pixel among the prediction pixels of the current block, and
wherein the 3-tap filter includes a first filter coefficient corresponding to the reference pixel value and a second filter coefficient corresponding to the upper-leftmost pixel, wherein the second filter coefficient is 2 times larger than the first filter coefficient.
2. The video decoding method of claim 1 , wherein the 2-tap filter includes a third filter coefficient corresponding to the prediction value of the remaining pixels, and wherein the third filter coefficient is 1.5 times larger than the second filter coefficient.
3. The video decoding method of claim 1 , wherein the intra prediction mode of the current block is determined based on a Most Probable Mode (MPM).
4. A video encoding method comprising:
encoding information related to whether to apply a first filter to a reference pixel value of a current block and whether to apply a second filter for a prediction value of the current block,
wherein the information is related to at least one of an intra prediction mode of the current block or a size of the current block,
wherein when the intra prediction mode of the current block is a DC mode, as the second filter, a 3-tap filter is applied to an upper-leftmost pixel among prediction pixels of the current block and a 2-tap filter is applied to remaining pixels indicating uppermost pixels and leftmost pixels except the upper-leftmost pixel among the prediction pixels of the current block, and
wherein the 3-tap filter includes a first filter coefficient corresponding to the reference pixel value and a second filter coefficient corresponding to the upper-leftmost pixel, wherein the second filter coefficient is 2 times larger than the first filter coefficient.
5. The video encoding method of claim 4 , wherein the 2-tap filter includes a third filter coefficient corresponding to the prediction value of the remaining pixels, and wherein the third filter coefficient is 1.5 times larger than the second filter coefficient.
6. A non-transitory computer-readable storage medium storing a bitstream, the bitstream comprising:
information related to whether to apply a first filter to a reference pixel value of a current block and whether to apply a second filter for a prediction value of the current block,
wherein the information is related to at least one of an intra prediction mode of the current block or a size of the current block,
wherein when the intra prediction mode of the current block is a DC mode, as the second filter, a 3-tap filter is applied to an upper-leftmost pixel among prediction pixels of the current block and a 2-tap filter is applied to remaining pixels indicating uppermost pixels and leftmost pixels except the upper-leftmost pixel among the prediction pixels of the current block, and
wherein the 3-tap filter includes a first filter coefficient corresponding to the reference pixel value and a second filter coefficient corresponding to the upper-leftmost pixel, wherein the second filter coefficient is 2 times larger than the first filter coefficient.