近幾年來，越來越多高解析度裝置的使用，例如高畫質電視、智慧型手機、平板電腦等，高解析度伴隨而來的是龐大的資料量，所以視訊壓縮技術儼然成為一門重要的課題。
由ITU-T Video Coding Experts Group (VCEG) and ISO/IEC Moving Picture Experts Group (MPEG) 所制定的最新一代視訊壓縮標準High Efficiency Video Coding (HEVC)，在視訊多媒體中扮演著相當重要的角色，原因是它能在相同的影像品質下，擁有比以往的編碼標準(H.264/AVC)更佳的壓縮效率。
原始畫面減去Intra、Inter預測的畫面即為殘差，然後再轉換和量化有可能會發生轉換係數的量化誤差，因而使重建完的畫面產生artifact現象，之後先經過Deblocking filter對8×8的垂直邊界和水平邊界做邊緣強化，再經過自適應樣點偏移濾波器(Sample Adaptive Offset Filter)做畫面內的邊界強化，以提升影像的品質，SAO是HEVC新加入的濾波器主要可以分為兩個種類，分別為Edge Offset(EO)和Band Offset(BO)，EO主要是針對影像的紋理資訊去做分析，而BO則是針對影像的強度去做分析，最後會把計算得到的補償值加到像素裡面去減少像素的失真，但SAO在計算EO或BO及補償值花費許多時間。
而本論文主要是針對EO，去加快方向的決策以減少複雜度，最終整體編碼時間平均減少10.07%運算量，而位元率約有1.21%左右的提升。

In recent years, there are more and more people using high resolution devices, such as high-definition televisions、smart phones、tablet computers and etc. High resolution is associated with huge amount of data. So the video compression technology has become an important issue.
The High Efficiency Video Coding (HEVC) standard is the most recent joint video project of the ITU-T Video Coding Experts Group (VCEG) and the ISO/IEC Moving Picture Experts Group (MPEG) standardization organizations. It played a very important role in the video multimedia. The reason is that with the same quality, the HEVC has better compression efficiency than the H.264/AVC.
The original blocks subtract the prediction blocks is the residual. Afterward, transform and quantization may occur quantization errors of transform coefficients. As a result, reconstruction blocks produce artifact phenomenon. To enhance block boundary, reconstruction blocks go through the deblocking filter for 8×8 vertical and horizontal boundaries. Next, the SAO filter is to enhance edge within the picture. The procedure can enhance image quality. The HEVC added new filter called Sample Adaptive Offset Filter. The main two type of the SAO are EO (Edge Offset) and BO (Band Offset). Analysis of image texture information is the main EO. Analysis of image intensity is the main BO. Finally, in order to reduce mean sample distortion of a region, the offset will be added to each samples. But the SAO spend a lot of time to calculate EO, BO and offset.
This thesis is mainly for EO, speeding up direction decision is to reduce complexity. Finally, the proposed fast direction detection for SAO algorithm can reduce 10.7 % computation time and 1.21 % bitrate increase.

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