An efficient all zero block detection algorithm based on frequency characteristics of DCT in HEVC

Like the previous video coding standard, DCT and quantization are also adopted in HEVC. Compared with H.264/AVC, HEVC employs larger transform blocks, which makes the all zero block detection algorithm designed for H.264/AVC inefficient for HEVC. An efficient all zero block detection algorithm aimed at HEVC, especially for 16×16 and 32×32 transform blocks, is proposed in this paper based on frequency characteristics of DCT. By analysing the distribution of residual energy in frequency domain, Hadamard transform is used to evaluate only a part of DCT coefficients which usually consume most of energy. To make the proposed algorithm efficient in complex sequences, a sum of absolute transformed difference based method is used to evaluate the maximum value of the rest of the coefficients. Experimental results show that more than 90% all zero blocks for 4×4, 8×8 and 16×16 transform blocks and about 80% for 32×32 transform blocks can be detected by the proposed algorithm. In addition, about 50% computational complexity in DCT/quantization can be reduced with negligible loss of video quality and compression efficiency.