Patent ID: RE39455

Claim:
A method for encoding a sequence of video image frames comprising the steps of: dividing a source sequence into a set of group of pictures, each group of pictures comprising a first frame (I-frame) followed by a plurality of pairs of predictively encoded frames (PB-frame pairs), each PB-frame pair having a corresponding P-block; dividing each I-frame or PB-frame pair into a plurality of spatially non-overlapping blocks of pixel data; encoding the blocks from the I-frame (I-blocks) independently from any other frames in the group of pictures; predictively encoding the blocks from the second frame of the PB-frame pair (P-blocks), based on the I-blocks in the previous I-frame or the P-blocks in the previous PB-frame pair; bi-directionally predictively encoding the blocks from the first frame of the PB-frame pair (B-blocks), based on the I-blocks in the previous I-frame or the P-blocks in the previous PB-frame pair and the corresponding P-block in the current PB-frame pair; deriving a scaled forward motion vector and a scaled backward motion vector for the B-block by scaling the motion vector of the corresponding P-block in the current PB-frame pair; obtaining a final forward motion vector for the B-block by adding a delta motion vector to the scaled forward motion vector; and obtaining a final backward motion vector for the B-block by subtracting the delta motion vector from the scaled backward motion vector.