近年隨著寬頻網路的普及與多媒體資料編解碼技術的成熟，在網際網路中資料傳輸型態與特性，已逐漸從過去的非即時性數據資料演進至現階段的多媒體服務，然而在傳統網際網路的傳送機制下已無法滿足多媒體應用的需求，加上在視訊編碼過程中，不同型態的視訊封包具有不同重要性，若一視同仁地直接在網路上傳送，將使得視訊品質遭受嚴重影響。 基於以上的問題，本論文針對H.264視訊提出一套傳送於差異式服務網路之跨層服務品質對應機制。此機制包含三個主要部分：第一，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ㄧ同進行評估，並對於不同的影像特性進行調適性優先權調整；第二，在網路層中提出一套動態跨層服務品質對應機制，利用『應用層』中視訊封包優先權等級資訊對應到『網路層』中有限的差異式服務等級，並依據目前網路狀況做動態服務品質對應調整；第三，對於封包標頭所帶來的額外負擔，提出一套同時考慮優先權等級與封包標頭負荷的視訊封包封裝策略。在整體傳輸效能評估上，本論文所提出的跨層服務品質對應機制於差異式服務網路中，可有效提升視訊接收品質，比起未支援服務品質的傳統網際網路上增加4dB。而調適性視訊封包優先權訂定機制相對於僅使用畫面位置/封包內容之優先權機制也有3dB/1.5dB提升。對於具有優先權考量的視訊封裝策略亦比一般固定大小的封裝策略，提升約1.6dB。 With the technology advances in multimedia compression and Internet, video streaming of multimedia application is full of potentials. However, the delivery mechanism of the traditional Internet can not satisfied with the demand of multimedia application. Additionally, considering the video encoding process, the property of video packet with different types has different significance. An equal error protection to all video packets in the Internet will degrade the video quality significantly. Therefore, this thesis proposes a cross layer QoS mapping framework for H.264 video transmission over Diffserv network. Then there are three main parts in this framework; First, application layer proposes an adaptive priority of video packet mechanism. Furthermore, the mechanism can estimate each packet location and content information to adjust different video with adaptive priority. Second, network layer recommends a dynamic cross layer QoS mapping (D-CQM) mechanism. According to the current network situation, D-CQM can use the priority of video packet in application layer and it corresponds to the limited Diffserv level in network layer to regulate the dynamic QoS mapping. Third, for the extra packet header, it brings a packetization strategy that considers the priority of video packet and packet header overhead simultaneously. After evaluating the whole transmission efficiency, the cross layer QoS mapping framework over Diffserv network can improve the quality of video receiving and also better than the traditional Internet up to 4dB. Moreover, the adaptive priority of video packet is superior to the frame/packet based priority up to 3dB/1.5dB. For the strategy of priority packetization, it also increase PSNR up to 1.6dB than fixed packetization.
