HEVC是目前還在發展中的視訊編碼標準。相較於上一代H.264的視訊編碼標準，HEVC 採用四分樹的架構並且利用R-D成本公式決定最佳的編碼效能。轉換單元是轉換和量化最基本的單元，其大小有4*4至32*32。而四分樹架構以遞迴的方式去呈現編碼單元被分割成轉換單元。因為在畫間預測的殘餘值通常有較少的誤差，所以量化後為零的區塊偵測很常被用來做轉換研究。基於這樣的理由，若能提前偵測出量化後為零的區塊，則能減少殘餘四分樹決定時所需的計算複雜度。因此我們提出一個基於量化後為零之區塊的預測方法來加速殘餘四分樹的決策。若殘餘值區塊有較小的錯誤預測，尤其在編碼單元同質區域被編碼時，會選擇一個大區塊轉換單元去編碼， 例如32*32。基於這樣的觀察，我們提出兩個步驟的方法來省略不必要的四分樹決策所需花費的計算複雜度。第一個步驟決定離散餘弦轉換和量化是否能被省略，而第二個步驟則判斷能否提前終止轉換單元分割的過程。相較於原
本的編碼方式，實驗結果顯示我們提供的方法能在不同類型的影像，能維持一定的品質外，在畫面間四分樹的決策方面平均能減少50%的時間。

High E cieny Video Coding (HEVC) is an ongoing video coding standard. Commpared to H.264, it adopts quad-tree structure to decide the optimal encoding e ciency by computing the rate-distortion (R-D) cost function recursively. In HEVC, the transform unit (TU) is the basic unit used for the transform and quantization processes and the size of TU ranges from 4* 4 to 32* 32. The residual quad-tree (RQT) is recursive representation of the partition of a coding unit into transform units. Zero-quantized blocks (ZQBs) are quite common after transform (DCT) and quantization (Q) because a residual block obtained by using the inter prediction strategy has a small value in video coding. For that reason, the computational complexity of the RQT decision can be reduced if ZQBs are early detected before DCT and Q. Therefore, a method based on the zero-quantized block detection is proposed to accelerate the RQT decision. In addition, a large size TU is always chosen, e.g., 32 32, of the RQT if a residual block has a little prediction error, especially the homogeneous-area CUs are encoded. Based on the observations, the proposed method uses two stages to skip unnecessary computations on the RQT. The first stage decides whether DCT/Q processes can be omitted
or not. The second stage is used to early terminate the TU split process. Experiment results show that the proposed method is capable of reducing a large amount of time of inter prediction RQT decision on average 50% and retaining the coding performance by comparing to the original HEVC encoder.

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