视频空间分辨率下变换转换编码过程的运算量较大,受实时性、输出码率的限制,转换后的图像质量会有一定程度的下降。为了改善转换后码流的质量,同时又不会大幅增加计算量和输出码率,提出了综合考虑相邻宏块的运动矢量的集簇状态及其残差信息的情况,判断下变换后宏块纹理信息和运动矢量的失真情况,然后动态地选择一种转换编码算法。实验结果表明,使用该方案进行转换编码后,码流的质量有一定提高,同时避免了进行大范围运动搜索和引入大量内部编码的宏块。

Video transcoding for reduced spatial resolution needs a lot of computation.Restricted by real-time demand,the quality of transcoded stream will decrease in variant degree.In order to improve the quality of transcoded stream,a new scheme is proposed in this paper which estimates the distortion degree of downscaled texture and motion vector according to the condition of neighbor macroblocks' texture and the cluster degree of their motion vectors,and then adaptively chooses one arithmetic to transcode.Experimental results show that this scheme can bring some improvement to the quality of transcoded stream,and at the same time avoid extensive motion search and introducing much of intra-coded macroblocks.