視訊編碼的應用相當廣泛，從電視傳播、視訊會議、監控系統、影片拍攝、影片串流到手持裝置的應用，都有舉足輕重的地位。目前新制定的H.264/AVC編碼標準，採用了更多樣化的編碼技術，以提高壓縮的效率與畫質。在比MPEG-2 提供更佳的編碼效能背後，所付出的是為編碼器帶來相當大的運算量，而使H.264/AVC無法輕易地實現在即時編碼的應用環境。因此，如何有效降低編碼的運算量，並維持應有的壓縮品質，是相當重要且熱門的研究主題。本論文提出了使用最近中心法，配合多階層式分類的機制，快速篩選出最適合的編碼區塊大小，不但有效降低了編碼所需的運算時間，更保持了相當優越的壓縮品質。根據實驗，本論文所提出的方法可節省約68% 的編碼時間，卻能維持與原本非常接近的壓縮品質。 Video coding plays an indispensible role in a wide variety of applications such as TV-broadcast, video conference, monitoring system, filming, video streaming and mobile service. The latest video coding standard, H.264/AVC, adopts several new coding techniques to improve the compression ratio and visual quality. In spite of the better coding efficiency comparing to MPEG-2, H.264/AVC suffers from the extremely high computational burdens in the encoding process induced by those new coding features. Therefore, how to reduce the encoding complexity while keeping nearly the same coding performance is a vital and challenging task. In this paper, a very efficient fast mode decision algorithm using nearest mean method and multi-phase classification scheme is proposed, which reduces encoding time greatly without any noticeable performance degradation.
