新一代的視訊壓縮標準HEVC(High Efficiency Video Coding)畫面內預測之角度模式擁有33個不同的方向，使得預測畫面能更精確地預測，而得到更好的壓縮效能。然而HEVC角度預測擁有單一方向性的缺點，因此在複雜紋理的畫面還有改善的空間。曾有文獻[1]提出利用渲染方法來加以改善預測畫面，但編碼時間過長，為了解決此問題，文獻[2]提出了新的方法，將原本使用於半色調法(Halftoning)的錯誤擴散法(Error Diffusion)應用於畫面內預測(Intra Prediction)之中。錯誤擴散法能夠在不增加過多編碼時間的情況下，有效改善含有複雜紋理之區塊的預測畫面，進而增進壓縮的效能。但增加20%的編碼時間還是覺得太多，因此本篇論文將錯誤擴散法加以改良，讓時間下降至5%並且能夠改善編碼效能，另外半色調法裡除了有錯誤擴散法之外，還有另一個有序抖色法(Order Dithering)，我們將之應用至HEVC畫面內預測，經由實驗證明，僅需增加約3%的編碼時間，且依然能夠降低約0.5%的BDBR(Bjontegaard Delta Bit Rate)。;In order to predict more accurately, High Efficiency Video Coding, the latest standard of video compression, has 33 different directions in intra prediction, so we can get better coding performance. However, the characteristic of single directionality has not changed. There is still plenty of room for improvement in complex texture image. To improve coding performance of intra prediction, the inpainting technique[1] has been studied but it is impractical because of its high computational complexity. In [2], Error diffusion is applied to HEVC intra prediction. It can improve the quality of prediction images by extending the information of bilateral reference pixels to them with only a little increase of time consumption. In addition, It still has 20% increase of encoding time, so we improve it in this paper. The improving error diffusion just need 5%, and the coding performance can be better. Except for the error diffusion, there is another technique named ordered dithering which come from Halftoning. We apply it to HEVC intra prediction. The results demonstrate that average 0.5% BDBR reduction can be achieved, and only need 3% increase of encoding time in the proposed algorithm, compared to HEVC intra prediction.
