視訊資料透過有限的無線網路頻寬傳輸，必須使用具高壓縮率之視訊編碼如H.264/AVC。H.264/AVC為提升視訊編碼標準的壓縮率，採用較以往複雜的移動補償技術，但因移動補償造成的潛在性錯誤蔓延效應，使得已編碼之視訊串流要透過容易發生錯誤的無線網路環境下傳輸更是一大挑戰。除了視訊編碼標準本身造成的量化失真，還有在無線網路環境下，封包遺失…等造成的通道失真，都會造成解碼端在重建視訊串流時，發生嚴重的錯誤蔓延效應，進而影響解碼後的影像品質。近年來隨著網際網路的蓬勃發展，多媒體通訊的應用與服務範疇亦相對擴張，因此除了將視訊串流有效率地轉換編碼成符合異質網路環境之H.264/AVC串流格式外，另一面須提升視訊串流的容錯能力。本計畫於前兩個年度已針對即時性之轉換編碼器作一探討，而部分研究成果已經發表於知名期刊及知名國際會議上，未來一年將探討適用於即時視訊網路傳輸並具有抵抗錯誤蔓延效應之容錯性視訊編碼。最後將本系統的整體效果與其他子計劃作整合，並將相關研究成果發表於知名期刊或知名國際會議上。Due to channel bandwidth limitation of wireless networks, a video bit stream has to be highly compressed using efficient coding techniques, such as H.264/AVC. To improve coding efficiency, the H.264/AVC encoder features many advanced techniques such as variable block sizes mode decision, quarter-pixel motion compensation and multiple reference frames. These advanced coding techniques cause severe error propagation problem in error-prone wireless transmission channels due to channel distortions. The error propagation severely deteriorates decoded visual quality, and a robust error resilient video coding is required in error-prone transmission channel. In the first two years of this project, we have investigated many advanced transcoding techniques to meet channel requirements such as bit rate reduction etc., and in this year we investigate robust error resilient video coding techniques to improve video quality over error-prone wireless networks. The joint source and channel rate-distortion mode decision for H.264/AVC video coding will be studied. In the proposal algorithm, a novel rate-distortion cost function, taking channel distortions into account, will be considered in mode decision to improve visual quality in error-prone heterogeneous wireless networks. 研究期間：10008 ~ 10107
