The scalable extension of H.264 video coding standard (SVC) has achievesd temporal scalability using Hierarchical-B structure. Compared to traditional coding structures like IPPP and IBBP

ithas a significant coding gain as well. However

due to its hierarchical prediction dependency

quality fluctuation among consecutive frames may sometimes occur. Such situation usually gets worse when high motion or scene changes exist. In this paper

we propose a simple but effective constant quality algorithm based on PSNR and MAD measures. Restriction to the possible fluctuation is realized by adapting the quantization parameter(QP) at frame level. We simulate our method based on JVT official specification. Experimental results show that our algorithm has greatly reduced the PSNR variance and obtained the target PSNR simultaneously.