Patent ID: 7660471

Claim:
A method in video coding or decoding executed at a video compression apparatus for calculating interpolation ½ position pixel values and ¼ position pixel values located between integer pixel positions when determining a prediction of a first pixel block in a video picture from a second pixel block in a previous decoded video picture with a spatial offset relative to the first pixel block according to a motion vector in a set of motion vectors, said method comprising: calculating, at the video compressing apparatus, the ½ position pixel values by a six-tap filter on neighboring integer pixel position values including a rounding addition value of 16/32 or calculating the ½ position pixel values by a four-tap filter on neighboring integer pixel position values including a rounding addition value 4/8, calculating, at the video compressing apparatus, the ¼ position pixel values by averaging two neighboring ½ position pixel values or one neighboring ½ position pixel value and one integer position pixel value followed by rounding or truncation, and adjusting, at the video compressing apparatus, previously calculated ½ position pixel values by a negative or positive shift to compensate for an error introduced by rounding or truncating calculated ¼ position pixel values by reducing the rounding addition value to a value less than 16/32 if the six-tap filter is used and reducing the rounding addition value to a value less than 4/8 if the four-tap filter is used.