Fast Algorithm of Subband Discrete Cosine Transform Based on H.264
Jiang Jian-guo①②; Lu Xiao-hong①; Qi Mei-bin①②; Zhan Shu①②
①School of Computer and Information, Hefei University of Technology, Hefei 230009, China;②Engineering Research Center of Safety Critical Industrial Measurement and Control Technology, Ministry of Education, Hefei 230009, China
Abstract:Fast DCT (Discrete Cosine Transform) is one of the key issues in H.264, according to the properties of DCT coefficients’ energy distribution and the characteristics of “zigzag scan”, one fast DCT algorithm is proposed based on divided subbands. In the algorithm, DCT coefficients of the prediction residue (Zero Quantized DCT coefficients, ZQDCT) are set zero predictably before implementing DCT and quantization (Q), and then the redundant computations are deduced greatly. One adaptive scheme is also presented with multiple thresholds to divide the subbands. By this scheme, only the DCT coefficients without ZQDCT will be computed. The experimental results show that the proposed algorithm outperform other approaches in literature, and achieve the best performance in reducing computations in the case of the same picture quality and the same compression ratio by the traditional algorithms in H.264 .