Rate-distortion optimized layered coding of high dynamic range videos

Abstract

An efficient algorithm to compress high dynamic range (HDR) videos into layered bitstreams is proposed in this work. First, we separate an HDR video sequence into a tone-mapped low dynamic range (LDR) sequence and a ratio sequence, which represents ratios between HDR and LDR pixel values. Then, we encode the LDR and ratio sequences to maximize the rate-distortion (R–D) performance by extending the standard H.264/AVC codec. Specifically, we estimate the distortion of the HDR sequence from those of the LDR sequence and the ratio sequence, and then allocate a limited bit budget to the LDR sequence and the ratio sequence efficiently to maximize the qualities of both LDR and HDR sequences. Conventional LDR devices use only the LDR stream, whereas HDR devices reconstruct the HDR video from the LDR and ratio streams. Simulation results show that the proposed algorithm provides significantly better R-D performance than conventional HDR video coding techniques.