比起先前的視訊壓縮技術，如MPEG-2以及H.263，H.264/AVC有著更好的編碼效率，這是因為有許多先進的技術被應用在裡面，B畫面中的直接模式就是其中一種，當最佳模式被決策為直接模式時，我們就可以得到較低的位元率。在H.264/AVC中，時間域直接模式利用後一張P畫面中相同位置巨區塊的資訊來取得直接模式移動向量，但是這種方式並未考慮到所有的移動情形，因此除了考慮後一張P畫面中相同位置巨區塊的知訊之外，在本篇論文中，我們將它鄰近巨區塊的資訊也列入考慮，藉此已達成改良直接模式的目的。在本篇論文的最後，實驗結果也顯示出我們所提出的方法可以比原始的方法帶來大約平均3.3%的位元率增益。 H.264/AVC achieves better coding efficiency than previous coding standard, such as MPEG-2 and H.263. This is because that many advanced techniques are employed. One of important technique is direct mode coding. The encoded bit rate can be saved when the direct mode is chosen as best mode. In H.264/AVC, temporal direct mode only uses the co-located information of previous coded P picture. However the motion in video sequence is not still. In addition to the co-located information, in this thesis we make use of the neighboring information to improve the direct mode coding. The experimental results show that our proposed algorithm can achieve 3.3% of BD bit-rate decrement on average when compared to original algorithm.
