Chinese Academy of Sciences

Debin Zhao

Wen Gao

Yan Lu

Siwei Ma

Xiangyang Ji

Qiang Wang

Honggang Qi

A method for obtaining an image reference block in a code mode of fixed reference frame number includes the steps of: performing motion estimation for each block of a current B frame and obtaining a motion vector MV of a corresponding block of a backward reference frame; discriminating whether the motion vector is beyond a maximum forward reference frame which is possibly pointed by the B frame, if not, then calculating the forward and backward motion vectors in a normal way; if yes, then using the motion vector of the forward reference frame that the B frame can obtain in the same direction to replace the motion vector of the corresponding block in the backward reference, and calculating the forward and the backward motion vectors of the B frame; finally, two image blocks pointed by the final obtained forward and backward motion vectors as the image reference blocks corresponding to the macro block. The present invention solves the possibly appeared problem of un-matching motion vectors, and can guarantee the coding efficiency to the largest extent.

Method for obtaining motion vector and image reference block in a code mode of fixed reference frame a number

The invention discloses a bi-directional prediction method for video coding/decoding. When bi-directional prediction coding at the coding end, firstly the given forward candidate motion vector of the current image block is obtained for every image block of the current B-frame; the backward candidate motion vector is obtained through calculation, and the candidate bi-directional prediction reference block is obtained through bi-directional prediction method; the match is computed within the given searching scope and/or the given matching threshold; finally the optimal matching block is selected to determine the final forward motion vector, and the backward motion vector and the block residual. The present invention achieves the object of bi-directional prediction by coding a single motion vector, furthermore, it will not enhance the complexity of searching for a matching block at the coding end, and may save amount of coding the motion vector and represent the motion of the objects in video more actually. The present invention realizes a new prediction coding type by combining the forward prediction coding with the backward.

Bi-directional predicting method for video coding/decoding

The present invention provides an entropy coding method for coding video prediction residual coefficients, comprising the steps of: firstly, zig-zag scanning coefficients of blocks to be coded to form a sequence of (level, run) pairs; secondly, selecting a type of code table for coding a current image block to be coded according to a type of macro block; then switching and coding each (level, run) pair in the obtained sequence of (level, run) pairs with multiple tables, with the reverse zig-zag scanning order for the coding order of the pairs; at last, coding a flag of End of Block EOB with the current code table. The present invention of an entropy coding method for coding video prediction residual coefficients fully considers the context information and the rules of symbol's conditional probability distribution by designing different tables for different block types and different regions of level. The coding efficiency is improved and no impact to computational implementation complexity is involved.

Entropy coding method for coding video prediction residual coefficients

A 'rounding to zero' method can maintain the exact motion vector and can also be achieved by the method without division so as to improve the precision of calculating the motion vector, embody the motion of the object in video more factually, and obtain the more accurate motion vector prediction. Combining with the forward prediction coding and the backward prediction coding, the present invention realizes a new prediction coding mode, which can guarantee the high efficiency of coding in direct mode as well as is convenient for hardware realization, and gains the same effect as the conventional B frame coding.

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Beijing, China

Debin Zhao