新一代的H.264不管是壓縮率和影像品質都明顯優於以往的視訊標準。這是因為其使用了新的技術[1]：可變區塊大小的移動估計（variable block size motion estimation）、多幅參考畫面的移動估計（multi-reference frame motion estimation）、整數轉換（integer transform）。為了達到更好的編碼效益，H.264/AVC更使用位元率失真函數(rate distortion optimization, RDO）技術來得到更好的編碼結果[2]。然而卻使其編碼端的運算複雜度大幅提升，導致增加了硬體實現的困難度；而其計算的複雜度主要分佈在可變區塊大小及多幅參考畫面的移動估計。在此篇論文中，利用時間域的移動緩慢特性(stationary)及空間域的平滑特性(homogenous)，我們提出兩種快速區塊模式決策的方法，在影像品質幾乎沒有失真的情況下，降低編碼端的運算複雜度。 The new video coding standard, H.264/AVC, use variable block size ranging from 4x4 to 16x16 and multi-reference frame in interframe coding. This new feature has achieved significant coding gain compared to coding a macroblock using fixed block size. However, this feature results in extremely high computational complexity when brute force rate distortion optimization (RDO) algorithm used. This thesis proposed two fast intermode decision algorithms to decide the best mode in interceding. It make use of the spatial homogenous and the temporal stationary. Based on homogeneity and stationary of the video objects, only a small number of intermodes are selected in RDO process. The experimental results show that the fast intermode decision is able to reduce the encoding time, with a negligible peak-signal-to-noise ratio.
