Fast intra-mode decision method based on DCT coefficients for H.264/AVC

This paper presents an efficient intra-mode decision method for H.264/AVC. By slightly changing the mode examination order, the proposed method obtains the discrete cosine transform (DCT) coefficients of the original 4 x 4 image blocks without requiring any additional computation. These DCT coefficients are efficiently utilized to determine the best modes for 4 x 4 luma blocks. Then, the proposed method makes use of the best mode information of the 4 x 4 luma blocks to determine the best modes for 16 x 16 luma blocks. A new chroma mode decision method is also presented, which efficiently combines several DCT coefficients from various 4 x 4 sub-blocks. As a result, the proposed method reduces the encoding time of the conventional methods while also improving the coding performance significantly. Simulation results show that the average BD-BR of the proposed method is 1.63% while the reduction in the encoding time of the reference software is 66.3% on average.