多媒體通信傳播品質日漸提升，其中高畫質視訊處理技術更是顯著提升，高效率視訊編碼(HEVC)即為了處理高畫質視頻需求而制定。HEVC為目前最新的視訊編碼標準，其發展目標為達到與上一代視訊編碼標準－H.264差不多的畫面品質下，節省一半的位元率(Bit-rate)。為達到如此優良的編碼效率，HEVC使用了許多新的編碼技術，如:編碼單位(Coding Unit(CU))、預測單位(Predict Unit(PU))和轉換單位(Transform Unit(TU))，但也因此增加了大量的運算複雜度。在編碼時，HEVC必須花費相當大量的時間對所有的CU區塊分割模式估算編碼效能以決定最好的區塊方割方式。針對此一問題，本篇論文提出了快速CU決策的方法，藉此減少HEVC編碼法中畫面間預測編碼的複雜度。在我們的方法中，基於CU切割流程中的失真值、位元(Bits)、率-失真衡量數據、鄰居區塊的最佳深度等級，以及是否選擇SKIP模式等資訊，提出了三種提早終止(early termination)CU決策流程的方法。其中方法一基於「失真值」、「位元」；方法二基於「RD-Costs」、「SKIP模式」；方法三基於「鄰居區塊的最佳深度等級」與「SKIP模式」，最後將此三種方法結合成一快速CU決策演算法，並提供了三種結合模式。實驗結果顯示，我們所提出的演算法，依三種不同的結合模式，平均分別能減少42.52%、 38.47 %與32.63%的時間。

Multimedia commnications enable high quality video transmission and the high efficienct video coding standard, HEVC, is proposed to provide high perception QoS for users. The HEVC design target is to provide a new video coding standard that can use half the bitrates but maintain the same coding quality as compared to the previous one, H.264. To achieve this coding efficiency, several coding units, such as coding unit (CU), prediction unit (PU), and transform unit (TU) are utilized in the HEVC and the coding complexity is increased. In the HEVC coding process, as it has to spend a lot of time to determine the best CU mode, more efficient CU mode decision methods are required. We proposed to speed the CU mode decision process such that the HEVC inter-frame coding complexity can be largely reduced. In our method, parameters such as the distortion, rates, rate-distortion cost, optimal depth level of neighboring blocks, and whether using skip modes, are utilized to determine the coding depth of current CU. Three early termination strategies are specified:(1) the first one is carried out based on distortion and rate; (2) The second one on RD-Cost and Skip Mode; (3) The third one on the optimal depth level of neighboring blocks and skop modes. The three strategies are combined to yield a fast CU decision method, which can be carried out with three operation modes. Experiments showed that the proposed method with three operation modes can reduced the encoding time on the average with 42.52%, 38.47% and 32.63% smaller, respectively, as compared to the standard HEVC codec, HM13.0.

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