A rate-distortion optimization model for SVC inter-layer encoding and bitstream extraction

Abstract

The Scalable Video Coding (SVC) standard enables viewing devices to adapt their video reception using bitstream extraction. Since SVC offers spatial, temporal, and quality combined scalability, extracting proper bitstreams for different viewing devices can be a non-trivial task, and naive choices usually produce poor playback quality. In this paper, we propose a two-prong approach to achieve rate-distortion (R-D) optimal extraction of SVC bitstreams. For SVC encoding, we developed a set of adaptation rules for setting the quantization parameters and the inter-layer dependencies among the SVC coding layers. A well-adapted SVC bitstream thus produced manifests good R-D trade-offs when its scalable layers are extracted along extraction paths consisting of successive refinement steps. For extracting R-D optimized bitstreams for different viewing devices, we formalized the notion of optimal and near-optimal extraction paths and devised computationally efficient strategies to search for the extraction paths. Experiment results demonstrated that our R-D optimized adaptation schemes and extraction strategies offer significant improvement in playback picture quality among heterogeneous viewing devices. Particularly, our adaptation rules promise R-D convexity along optimal extraction paths and permit the use of steepest-descent strategy to discover the optimal/near-optimal paths. This simple search strategy performs only half of the computation necessary for an exhaustive search.