隨著寬頻網路與多媒體編解碼技術的成熟，使得多媒體服務的發展具有極大的潛力。在視訊編碼過程中，不同視訊型態的視訊封包具有不同重要性，若不顧視訊封包之重要性而將其一視同仁地傳送於網路上，將使得畫面移動量大或是複雜度高之視訊品質遭受嚴重影響。 基於以上的問題，本論文針對H.264視訊提出一套適用於網路中所有視訊使用者之視訊封包重要性分類機制。此機制包含兩個主要部分：首先，在應用層中提出調適性視訊封包優先權訂定機制，針對每個視訊封包所位於的畫面位置與內容資訊一同進行評估，並根據不同影像序列的特性進一步進行優先權調整，使封包重要性能夠有所區別。其次，在多使用者的網路環境中，提出依據影像類別來調整視訊封包重要性與網路遞送優先權之間的對應機制。有別於過去的對應機制對於不同影像類別採取一視同仁的作法，本機制根據多使用者之間的不同影像複雜度而給予不同的對應關係，使得重要的視訊封包能得到正確的保護。在整體的傳輸效能評估上，本論文之機制雖然會使畫面較為靜態的視訊影像品質有些許下降，但其影像品質還是在可接受範圍內；反觀畫面複雜度或移動度較高的視訊影像，將會有效地提升其影像品質，最高可將視訊品質提升6.67dB。 With technology advances in multimedia compression and Internet development, video streaming applications are full of potentials. By utilizing the current video coding techniques such as H.264, the significances of video packets in different video sequences may differ significantly. Equal error protection to all video packets regardless the significance may seriously degrade the quality of video sequences with high motion, complex texture, or intra-coded. Therefore, this thesis proposes a packet significance classification mechanism for multiple H.264 video streams over networks. This framework consists of two main parts. First, we propose an adaptive packet classification mechanism in the application layer. Based on the packet location in video frames, error propagation effect, and video sequence complexity, this mechanism can adaptively estimate the significance of each video packet. Second, we propose an adaptive QoS mapping mechanism based on video classes for multiple video users over networks. In contrast to traditional QoS mapping mechanisms that do not consider the differences of video properties among users, this study takes multiple video users into consideration. Different video sequences belonging to various users are assigned different QoS mapping criteria to the limited service levels in the network layer. Comparing the overall video transmission efficiency with traditional methods in simulations, the received video quality belonging to the users that send complex video sequences can be improved up to 6.67 dB. Although the received quality of video with low motions is slightly degraded, the overall received quality is still acceptable.
