中文摘要：

结合图像纹理特征和宏块运动特性，提出一种新的H．264降尺寸转码算法，充分利用输人编码码流中的编码信息来提高转码效率．通过运动边缘检测划分出运动区域与背景区域，针对不同区域内的宏块，基于其运动特性，采取不同的帧间模式选择策略．提出一种基于感兴趣区域的运动矢量合成和修正算法．利用运动矢量方差判断宏块运动的多样性，基于宏块的多样性和重要性自适应地合成和修正运动矢量．实验证明，此算法具有较强的鲁棒性和广泛的适用性，在转码后的视频质量和转码速度方面都取得了很好的效果．

英文摘要：

A novel fast variable block size selection method for an inter-MB in a video-downsizing transcoder for H. 264 is proposed, which uses the spatial homogeneity based on moving edge detection and temporal stationary characteristics by measuring activity magnitude. Based on the homogeneity and stationary of macro-blocks, only a few inter-modes are operated with the RDO process. In addition, adaptive motion vector re-construction and refinement scheme are proposed based on region of interest （ROI）, besides of using variance and DCT coefficient for the definition of diversity and importance, respectively. Experimental results show that the new method is more robust and achieves good performance in both quality and complexity.