影像壓縮標準H.264/AVC在現實應用上獲得極大的成功，不管是網路影音串流或是影音儲存媒體（藍光光碟）都將H.264/AVC用於其標準規格。然而下一代的視訊壓標準HEVC即將在2013年制定完成，在同樣主觀視覺品質之下HEVC比H.264/AVC節省約50%的位元率。由於目前主要流通的格式仍舊是H.264/AVC，提供一個H.264/AVC和HEVC的有效率轉碼方式是非常必要的。 本論文提出一個應用於畫面間預測之視訊轉換轉編碼架構，重複利用H.264/AVC解碼端所解出的運動向量、預測模塊及冗餘餘弦轉換係數等編碼預測資訊，找出其資訊與重複編碼時模式切割決策及運動向量估計的相關性。藉由參考編碼預測資訊作快速決策，以此節省編碼時間，使得這兩種不同視訊編碼標準之間的轉換更加有效率。實驗顯示應用論文中所提出的可變搜尋視窗及快速決策方式，能夠節省40%-50%之整體編碼時間，且保持一定的影像品質及壓縮表現。Video compression standard H.264/AVC on the great success in real life applications, whether it is Internet video streaming or audio and video storage media (Blu-ray Disc) use H.264/AVC for its specifications. However, the next generation of video compression standard HEVC is about to be completed in 2013, under the same subjective quality metric HEVC save about 50% bit rate to H.264/AVC. Thus, it can be expected as a successor to H.264/AVC. The widely use of the H.264/AVC standard today and the expected adoption of HEVC raises a new demand for H.264 to HEVC transcoding. An Efficient transcoding way is necessary. In this thesis, we present several strategies for H.264 to HEVC transcoding on pixel domain transcoding architecture. And reuse the coding information ex. motion vector, prediction mode and residual DCT coefficient from the H.264 decoder side. For inter frame, we adopt the adaptive search range for motion estimation and candidate pruning for mode decision. The experimental results show that our propose transcoding strategies can maintain the coding performance and save 40%-50% encoding time.
