Layer-based temporal dependent rate-distortion optimization in Random-Access hierarchical video coding

Rate-distortion optimization (RDO) plays an important part in improving the coding efficiency of High Efficiency Video Coding (HEVC), especially for the hierarchical coding structure defined in the Random-Access (RA) configuration, noted as Random-Access Hierarchical Video Coding (RA-HVC), where different frames are assigned to different temporal layers and further coded with different coding parameters. Due to the inter-frame prediction, coding result of one unit may affect the coding performance of the following temporally related units. Therefore, the temporal dependency among units needs to be considered in the coding process. However, the RDO process in the current video codec is performed without considering the varying temporal dependency, thus compromising the rate-distortion performance significantly. To address this problem, a layer-based temporal dependent RDO method is proposed in this paper where the temporal dependency among different frames in the same or different layers is examined. By reformulating the temporal dependent RDO for the RA-HVC, we show that it can be implemented in a way of simply refining the Lagrange multiplier. Experimental results show that the proposed method achieves, in average, about 1.4% BD-rate savings with a negligible increase in encoding time for the random-access configuration.