H.263中基于全零块发现的运动搜索方法

Ｈ．３２４系统中，Ｈ．２６３图象编码速度一直是影响系统实时性能的瓶颈，而运动搜索和ＤＣＴ等模块又是其中运算量最大的模块，为了进一步降低图象编码的运算量，提出了一种基于零块发现的运动搜索方法。该方法在对活动图象进行运动搜索时，应用了一种基于发现全零块的中止准则，使得Ｈ．２６３中占用运行时间最多的ＩＮＴＥＲ块的运动搜索，收敛得更快，它尤其提高了对背景图象或者变化较小的图象部分的编码效率，同时也较大幅度也减少了ＤＣＴ等模块所占用的计算时间。该算法在提高速度的同时，仍保持了Ｈ．２６３原有压缩算法的效率和图象质量。

Motion Search Based on Zero Block Detection in H.263

To further improve the performance of H.263' s encoder in the real time H.324 system, a motion searchalgorithm using zero block detection technology, is proposed in this paper. This algorithm exploits the fact thatmany residual blocks become all zero blocks after DCT and coarse quantization in very low bit rate video coding.To further speed up the encoder implementation, this zero detection technology is combined with motionestimation. In the motion search process, if an all zero macro-block is detected using the distortion value of themacro-block, the search process is stopped. The choice of the threshold for zero detection is critical. Simulationresults show that the algorithm can dramatically decrease the motion search points. And also many blocks'quantization, DCT and other reconstruction steps are skipped. Under typical quantization parameter of 12, theaverage search points decrease is 30%~50%, and 25%~30% blocks' DCT and quantization is skipped due to thezero detection in the motion search. With the gain of encoder speed, the algorithm does not suffer the codingefficiency of the H.263 baseline. The algorithm does not affect the reconstructed image quality either. After thealgorithm is combined into a real~time H.324 system, the performance of the whole system is improved a lot.