Fast transform unit decision for HEVC

For the High Efficiency Video Coding (HEVC) standard, a fast transform unit (TU) decision method is proposed. HEVC defines the TU representing a region sharing the same transformation, and it supports various transform sizes from 4×4 to 32×32 by using a quadtree of TUs. The various sizes of TUs can provide good coding efficiency, whereas it may increase dramatically encoding complexity. Assuming that a TU with highly compacted energy is unlikely to be split, the proposed method determines an appropriate TU size according to the position of the last non-zero transform coefficient and the number of zero transform coefficients. Experimental results show that this reduces encoding run time by 14% with a negligible coding loss of 0.38% BD-rate from Random_access_main case.