Inter-Frame Dependent Rate-Distortion Optimization Using Lagrangian Multiplier Adaption

Abstract : It is known that, in the current hybrid video coding structure, spatial and temporal prediction techniques are extensively used which introduce strong dependency among coding units. Such dependency poses a great challenge to perform a global rate-distortion optimization (RDO) when encoding a video sequence. RDO is usually performed in a way that coding efficiency of each coding unit is optimized independently without considering dependeny among coding units, leading to a suboptimal coding result for the whole sequence. In this paper, we investigate the inter-frame dependent RDO, where the impact of coding performance of the current coding unit on that of the following frames is considered. Accordingly, an inter-frame dependent rate-distortion optimization scheme is proposed and implemented on the newest video coding standard High Efficiency Video Coding (HEVC) platform. Experimental results show that the proposed scheme can achieve about 3.19% BD-rate saving in average over the state-of-the-art HEVC codec (HM15.0) in the low-delay B coding structure, with no extra encoding time. It obtains a significantly higher coding gain than the multiple QP (3) optimization technique which would greatly increase the encoding time by a factor of about 6. Coupled with the multiple QP optimization, the proposed scheme can further achieve a higher BD-rate saving of 5.57% and 4.07% in average than the HEVC codec and the multiple QP optimization enabled HEVC codec, respectively.