Method for image interpolation using asymmetric interpolation filter and apparatus therefor
A sub-pel-unit image interpolation method using a transformation-based interpolation filter includes, selecting, based on a sub-pel-unit interpolation location in a region supported by a plurality of interpolation filters for generating at least one sub-pel-unit pixel value located between integer-pel-unit pixels, one of a symmetric interpolation filter and an asymmetric interpolation filter from among the plurality of interpolation filters; and using the selected interpolation filter to generate the at least one sub-pel-unit pixel value by interpolating the integer-pel-unit pixels.
1. An apparatus for motion compensation, the apparatus comprising:
a luma interpolation filtering unit which is configured for determining, in a luma reference picture, a luma reference block for prediction of a current block, by using a luma motion vector of the current block, and generating a luma sample of a ¼-pixel location or a ¾-pixel location included in the luma reference block by applying a 7-tap filter to luma samples of an integer pixel location of the luma reference picture; and
a chroma interpolation filtering unit which is configured for determining, in a chroma reference picture, a chroma reference block for prediction of the current block, by using a chroma motion vector of the current block, and generating a chroma sample of a ⅛-pixel location or a 4/8-pixel location included in the chroma reference block by applying a 4-tap filter to chroma samples of an integer pixel location of the chroma reference picture,
wherein the 7-tap filter comprises seven filter coefficients, and
the 4-tap filter comprises four filter coefficients.
2. The apparatus of claim 1 , wherein the luma interpolation filtering unit is configured for scaling the luma sample generated by applying the 7-tap filter by using a luma scaling factor so that a sum of coefficients of the 7-tap filter is 1.
3. The apparatus of claim 1 , wherein the chroma interpolation filtering unit is configured for scaling the chroma sample generated by applying the 4-tap filter by using a chroma scaling factor so that a sum of coefficients of the 4-tap filter is 1.