An early block type decision method for intra prediction in H.264/AVC

In this paper, we propose an early block type decision method to reduce the complexity of rate-distortion (R-D) cost computation in intra prediction. Our method decides the block size early among luma 4 times 4, 8 times 8 and 16 times 16 with simple decision scheme. R-D cost for mode decision is used for R-D cost of a subblock ( 8 times 16 block ) instead of that of macroblock (MB) with the proposed encoding order for the intra prediction of 4 times 4 and 8 times 8 block. The R-D cost of a subblock consists of luma components only. Chroma components have a smaller potion of the R-D cost because they use subsampling (4:2:0) and there is relatively small variance among chroma pixels. Our method provides the reduction of computational complexity with average 0.04 dB PSNR degradation and rate increase of less than 1% in comparison with the full search method.