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Fast RQT structure decision method for HEVC

Variable transform block (TB) sizes cause high computational complexity at the HEVC encoder. In this paper, a fast residual quad-tree (RQT) structure decision method is proposed to reduce the number of candidate transform sizes. The proposed method uses spatial and temporal correlation information in the neighbor blocks to predict the depth of current RQT. In addition, an efficient all zero block (AZB) detection approach is designed to accelerate transform and quantization. At last, the nonzero DCT coefficient (NNZ) based scheme is also integrated in the proposed method to early terminate the recursive RQT mode decision process. Experimental results show that our proposed method is able to reduce 70% computation complexity on average in RQT structure decision. And the BDBR and BDPR gains are 1.13% and −0.048dB respectively which are negligible.