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Efficient key picture and single loop decoding scheme for SHVC

Scalable video coding has been a popular research topic for many years. As one of its key objectives, it aims to support different receiving devices connected through a network structure using a single bitstream. Scalable video coding extension of HEVC, also called as SHVC, is being developed by Joint Collaborative Team on Video Coding (JCT-VC) of ISO/IEC MPEG and ITU-T VCEG. Compared to previous standardized scalable video coding technologies, SHVC employs multi-loop decoding design with no low-level changes within any given layer compared to HEVC. With such a simplified extension it aims at solving some of the problems of previous scalable extensions that haven't been successful, and at the same time, aims at supporting all design features that are of vital importance for the success of SHVC. Supporting lightweight and finely tunable bandwidth adaptation is one such vital design feature important for the success of SHVC. This paper proposes novel high level syntax mechanism for SHVC quality scalability to support: (a) using the decoded pictures from higher quality layer as reference for lower layer pictures and key pictures concept to reduce drift; (b) single loop decoding design with encoder only constraints without introducing any normative low-level changes to the normal multi-loop decoding process. Experimental results based on SHVC reference software (SHM 2.0) show that the proposed key picture method achieves an average of 2.9% luma BD-rate reduction in multi-loop framework and an average of 4.4% luma BD-rate loss to attain the capability of single loop decoding.