Chinese Journal of Computers   Full Text
Title	A Rate Control Algorithm for Scalable Video Coding
Authors	XU Long1) GAO Wen1)，2) JI Xiang-Yang1) ZHAO De-Bin3)
Address	1)(Institute of Computing Technology, Chinese Academy of Sciences, Beijing 100190) 2)(Institute of Digital Media, Peking University, Beijing 100871) 3)(Department of Computer Science and Technology, Harbin Institute of Technology, Harbin 150001)
Year	2008
Issue	No.7(1175—1184)
Abstract &   Background	Abstract The joint scalable video model (JSVM) as a scalable extension of H.264/AVC provides a high efficient solution for scalable video coding (SVC). However, there is not efficient rate control scheme is specified. This paper presents a new rate control scheme for the JSVM based on the special structure of hierarchical B decomposition (or motion compensation temporal filtering (MCTF)). In a sense of bit allocation, a novel hierarchical bit allocation strategy is proposed. Meanwhile, the different rate-distortion (R-D) model is provided for each kind picture with different picture type or temporal decomposition level. Experiment results show that the mismatch of target bit rate and real bit rate generated for coding doesn’t exceed 2%; meanwhile, the PSNR improvement can be up to 1dB in low bit rate; furthermore, comparing to the original rate control method which achieves the target bit rate through regulating quantization parameter (QP) step by step, the computation complexity of the proposed rate control algorithm base on experimental model is reduced drastically. Keywords scalable video coding; rate control; rate distortion optimization; rate distortion model Background This paper is concentrated on the rate control for joint scalable video model (JSVM). In the beginning of standardization of scalable video coding (SVC), there is not efficient rate control scheme proposed for JSVM, where the bit rate controlling is realized by multi-pass encoding. Certainly, the target bit rate can be obtained by truncated the bit stream compressed with high picture quality or high bit rate, which is an important character of SVC. However, this method is hard to achieve the optimized coding performance, so a one-pass rate control scheme is proposed for JSVM in the authors’ previous work. For rate control of hybrid video coding H.264/AVC, the laboratory that the authors is currently dedicated to mading important contributions in the past several years. A two-pass rate control scheme proposed individually by Siwei Ma from the Lab. is adopted by JVT to be a reference solution of rate control of H.264/AVC. And also, a one-pass rate control scheme popularly employed in the current reference codec of H.264/AVC is proposed by Zhengguo Li, Singapore and Siwei Ma. In the beginning of standardization of SVC, the authors have provided the rate control scheme for JSVM, which is published in VCIP2005. The algorithm of VCIP2005 is based on the traditional rate distortion (R-D) model, and with a layered bit allocation strategy which can brings much more coding performance. The algorithm in this paper makes a bigger improvement than the previous one, due to a set of scaling-factors employed for bit allocation. In the new proposed bit allocation, a set of weight parameters derived from the importance of each subband/picture for the whole coding performance is used to help bit allocation; moreover, based on the experiments, the authors propose a leveled R-D model for each hierarchical level of subbands. For low-pass subbands, the quadratic R-D model is employed, and for high-pass subband, the linear R-D model is used. From the experiments provided by the authors, it can be seen that the leveled R-D model can reflect the relationship between R and D more accurately. This research is supported by National Natural Science Foundation of China under grant Nos.4041003, 60333020, National Key Scientific and Technological Project under grant No.2002BA906A35, National Basic Research Program of China (973 Program) under grant No.2004AA119010.