Patent ID: 8630349

Claim:
A method of determining and using motion vectors for a bi-predictive image block, the method performed by a moving picture coding system and comprising: obtaining, by the moving picture coding system, reference index information from a co-located image block for the bi-predictive image block; determining, by the moving picture coding system, motion vectors of the bi-predictive image block based on a type of reference picture referred to by the reference index information, the reference picture being for the co-located image block, the type being one of long term and short term, the type characterizing a temporal distance of the reference picture for the co-located image block with respect to the bi-predictive image block, the determining step determining the motion vectors according to a first set of expressions if the reference index information refers to a reference picture of the short term type and the determining step determining the motion vectors according to a second set of expressions if the reference index information refers to a reference picture of the long term type, the second set of expressions being different than the first set of expressions; and decoding, by the moving picture coding system, the bi-predictive image block based on the determined motion vectors.