块效应是基于块的编码系统中频繁出现的问题，特别是在码率较低的状况下尤为明显，这种块效应的存在严重影响了图像的主观质量。和MPEG系列标准不同的是，H．264并没有采用后处理滤波器，而是在运动矢量补偿环中添加了环路滤波器。但由于环路滤波器是基于宏块和条带的，且环路滤波的核心技术在于块效应值的大小的判定和滤波器的选择，因此其编码图像的主观质量不能完全令人满意。为了获得更好的主观效果，提出了一种基于H．264的新型环路滤波方法，该方法不仅使滤波算子被进一步细化，而且使块效应值的判定准则也融入了更多的影响因子。实验结果表明，无论是在主观上还是在客观上，滤波效果都较以前的方案有较大改善。

Block artifactwhich deteriorates the video subjective visual quality especially in low bit rate is a remarkable problem which usually appears in block based c1oding system. Unlike MPEG series coding system, H.264 does not use post processing filter but adds loop filter in motion vector compensation loop. Loopfilter is based on macroblock or piece. The most essential points in loop filter are strength—a value which indicates the strength of block artifact—and filtering operators. In order to obtain better subjective visual quality, a new loopfilter arithmetic where the filtering operators are added withmore details and some other factors are added in the arithmetic of computing strengths. In the experiment, it is showed that the subjective and objective quality of video can be improved remarkably.