Inter-frame dependent rate-distortion optimization using lagrangian multiplier adaption

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.