在HEVC上基於可調性手風琴變形之視訊壓縮方法

Abstract

視訊編碼追求的是快的處理速度和高壓縮比，越高的解析度和畫面品質越有這些需求。然而，這兩項需求是很難同時兼顧的，因為越高的壓縮比通常需要越複雜的編碼技術。Ouni等人提出一種基於手風琴變形（ACC）的新編碼方法，這種方法將多個視訊畫面組合成一個手風琴形狀的畫面，並將這個畫面用於壓縮，能用較低複雜度的編碼方式達到很高的壓縮比。對於畫面內容變化不大的影片，ACC在high bit-rates的編碼效果與H.264/AVC差不多。但是，將ACC編碼技術應用於HEVC可能不會更好，因為HEVC的編碼效率比H.264/AVC好的非常多。 此外，一個影片的內容不太可能變化都很小而全部適用於ACC。為了應付這些問題，在這篇論文提出了一種根據視訊畫面內容的特性，自適應性的在基於手風琴變形和傳統HEVC編碼方式之間動態切換的壓縮方法。實驗結果顯示，相較於HEVC，我們提出的方法可以節省高達21.1％的bit-rate和58.6％的編碼時間。

Fast processing speed and high compression ratio are always expected for video coding, especially for dealing with the increase of video resolutions and the demand of high quality. However, it is hard to compromise between each other since high compression ratio usually requires high coding complexities. Ouni et al. proposed a novel method called accordion-based (ACC) coding in which multiple video frames are combined into an accordion-like representation for compression and it can achieve high compression ratio with low coding complexity. Its coding efficiency is close to H.264/AVC for low-motion video at high bit-rates. However, it may no longer have benefit when applying the ACC to HEVC because HEVC has much better coding efficiency than H.264/AVC. Besides, it is not likely that all the frames in a video sequence are low-motion and thus suitable for ACC coding. To cope with these problems, in this thesis we propose an adaptive method which dynamically switches between accordion-based coding and traditional HEVC coding according to the characteristics of video frames. The experiment result shows that the proposed method can achieve up to 21.1% of total bit-rate saving and 58.6% of encoding time saving, compared to HEVC.