Speeding up HEVC intra coding based on tree depth inter-levels correlation structure

The encoding efficiency of the High Efficiency Video Coding (HEVC) standard is considerably higher than that of its predecessors. The intra coding method adopted by this new standard includes a larger number of prediction directions than those of its preceding standards namely H.264/AVC. This improvement contributed to enhance the encoding efficiency, but carried with it a much larger computational complexity. This paper presents an algorithm to speed-up the intra mode decision procedure through the exploitation of inter-level correlation observed between the predominant edge orientation of the current PU and those of the PUs already coded at lower levels of the encoding quadtree. Experimental results show that the proposed algorithm provides a decrease of up to 39.6% in the HEVC intra coding processing time, with a small increase in bit-rate (avg. 1.2%) and a negligible reduction in PSNR values.