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Abstract

The present invention discloses a method for fractional pixel interpolation in video coding. According to a preferred embodiment of the invention, a symmetric 4-tap filter is used to calculate intermediate 1/2 pixel values. Further, the 1/4 pixel values are calculated by averaging two values of neighboring pixel positions including at least one 1/2 pixel position in the horizontal and/or vertical direction, e.g. between a 1/2 pixel position and an integer pixel position The discrete impulse response of the 4-tap filter for calculating k pixel values and the impulse response derived from which for calculating q pixel values, correspond to respective frequency responses which are combined with weights according to the ratio of 1/2 and 1/4 pixel occurrences. The characteristics of the first impulse response, which in the preferred embodiment only have one degree of freedom, are tuned in such a way that the combined frequency response approaches an ideal frequency response being substantially flat close to one at low frequencies, and approaching zero at high frequencies. The present invention is especially useful in motion compensation in connection with inter prediction in video compression similar to the one defined in H.264/AVC.

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First Claim