Patent ID: 6608937
Filing Date: 2003-08-19
Classification: H04N

Abstract:
A method of encoding a source sequence of pictures comprising the steps of:dividing the source sequence into a set of groups of pictures, each group of pictures comprising a first frame, hereafter referred to as I-frame, followed by at least a pair of frames, hereafter referred to as PB-frames; dividing each I-frame and PB-frame into spatially non-overlapping blocks of pixels; encoding the blocks of said I-frame, hereafter referred to as the I-blocks, independently from any other frame in the group of pictures; deriving motion vectors and corresponding predictors for the blocks from a temporally second frame of said PB-frames, hereafter referred to as the P-blocks, based on the I-blocks in the previous I-frame or the P-blocks in a previous PB-frame; predictively encoding the P-blocks based on the I-blocks in the previous I-frame or the P-blocks in the previous PB-frame; predictively encoding the blocks of the first frame of said PB-frame, hereafter referred to as the B-blocks, wherein the encoding of the B-blocks.comprises for each B-block in series the steps of: deriving the minimum of the sum of absolute difference for the B-block based on the I-blocks in the previous I-frame or on the P-blocks in the previous PB-frame, hereafter referred to as SADf; deriving the sum of absolute difference for the B-block and the P-block in the P-frame of the PB-frame with the same location as the B-block, hereafter referred to as SADb; when SADf is greater than SADb, predictively encoding the B-block based on the P-blocks of the temporally second frame of the PB-frames; when SADf is lower than SADb: deriving, for the P-block with the same location as the B-block, the difference between said motion vector and said corresponding predictors; when the difference obtained is greater than a predetermined threshold, predictively encoding the B-block based on the I-blocks or the P-blocks in the previous PB-frame; when the difference obtained is smaller than the predetermined threshold, predictively encoding the B-block based on the P-blocks of the second frame of the PB-frame and the I-blocks or the P-blocks in the previous PB-frame.