Rate-Distortion Analysis And Its Application In Rate Control For Scalable Video Coding

With the rapid developments of communication and network technologies, video transmission is no longer restricted in traditional channels with fixed bandwidths. Multimedia services based on large distributed systems like Internet and wireless networks are very attractive now, such as video conferences, video-on-demand, mobile TV and etc. Such heterogeneous networks with time-varying characteristic bring about unprecedented challenges to reliable and efficient video transmission. In response to such requirements, JVT developed a new generation of video coding standard: scalable video coding (SVC). SVC provides several exciting scalabilities, enabling the original video to have a variety of subversions with low quality. Users with different capabilities can decode different parts of the bitstream according to their actual needs. The works in this thesis are based on SVC. We present a rate control algorithm for H.264/AVC base layer and SVC as well. We also propose a constant quality algorithm to restrict quality fluctuations in Hierarchical B structure.In the first part, we briefly outline the main techniques used by SVC and their implementations, in the order of temporal, spatial and quality scalability. We discuss about potential applications of rate-distortion optimization theory in the new context of SVC.Secondly, we define the rate control problem in details and give an in-depth analysis of the difficulties in rate control for H.264/SVC. We propose an efficient rate control scheme for H.26-compliant base layer with two-step quantization parameter determination but single-pass encoding: we use a pre-analysis stage to solve the famous chicken-and-egg dilemma in H.264 resulting from QP-dependent rate-distortion optimization (RDO); we refine the quantization parameter for each candidate mode in RDO to reflect one macroblock's rate-distortion information more accurately; our frame-level target bits allocation strategy considers the encoder buffer fullness combined with rate-distortion costs of past encoded frames. Then, we present a rate control algorithm for Hierarchical B structure, taking into account the different importance of different temporal level pictures in one GOP. Different weighting factors are used when allocating target bits.We extend our rate control algorithm to the enhancement layer in the third part. Since our rate control model decouples between layers, we can simply inherit the original model and parameter settings. When implementing rate control in enhancement layers, we use the new prediction mode BLSkip as the mode in pre-analysis stage. Furthermore, considering the computational complexity, we propose a fast RDO mode decision algorithm. We adjust the priority queue according to the probability distribution of MB coding modes such that the most probable mode will be checked first. The RDO process will be terminated early as soon as RD cost is below a threshold. Therefore, the overall computation burden can be reduced significantly.Finally, we talk about the problem of constant quality control. We observe that quality fluctuation between frames in Hierarchical B structure is obvious, particularly when scene cut occurs. We present a simple but effect constant quality control scheme based on PSNR and MAD measures. A suitable quantization parameter is determined at frame level to make the fluctuation range as small as possible.