新一代的壓縮標準 — 高效率視訊編碼 (High Efficiency Video Coding, HEVC) 利用了編碼單元的概念與分層式四分樹的架構，以提供適用於高解析度影像之壓縮技術，但卻也因此造成計算時間的大幅增加。在本論文中，我們提出一個植基於可調式權重的有效編碼單元之深度決定演算法，來有效提升HEVC的壓縮速度，並同時能夠得到相似於標準HEVC的壓縮品質。首先，我們為當前編碼單元估計出一個合適的深度範圍，為了確實反應出鄰近參考區塊的參考價值，深度估計式中將以鄰近參考區塊的平均殘差量作為依據，以達到自適性的效果。在取得合適的深度範圍後，當前編碼單元只需在該範圍內進行預測程序，藉此達到加速之目的。實驗結果顯示，我們所提出之演算法確實能夠有效提升HEVC的壓縮速度，並維持相似於標準HEVC的壓縮品質。另外，與Shen等人所提出的方法比較，我們的方法亦有部份的壓縮效果及壓縮速度上的優勢。

The state-of-the-art video codec, high efficiency video coding (HEVC), adopts quadtree-structured coding units (CUs) for efficient compression of high resolution video sequences. However, at the encoder side, motion estimation (ME) for the CUs in each quadtree-structured depth level should be preformed to find the optimized rate-distortion depth level, resulting in extremely high computational complexity. In this thesis, we propose an efficient CU depth level decision algorithm based on adaptive weight mechanism. By utilizing the residuals and depth levels of neighboring CUs in the current frame and co-located CU in the previous frame, the proposed algorithm can adaptively determine an appropriate depth level range for the current CU. Since ME process is only performed in the determined depth level range rather than all the depth levels, it leads to significant reduction of computational complexity. Experimental results demonstrate that the proposed algorithm can significantly reduce computational complexity while preserving quite similar quality of the reconstructed video sequences to that by standard HEVC encoder. Furthermore, when compared with Shen et al.'s method, the proposed method has some benefit on reducing bitrate and encoding time.

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