為H.264/SVC傳輸而設計之編碼相依性導向優先化策略

H.264/SVC三維可調的特性造成封包在制訂優先權上變得更加複雜。不同於以往依據layer type制訂封包優先權的作法，我們認為封包的重要程度不應該只參考其layer type，還要考慮是否能有效解碼。因此，我們提出編碼相依性（coding dependency；CD）graph來描述H.264/SVC當中frame解碼的相依性。CD graph是用於中介節點，例如行動閘道器，主要用來檢測封包的有效性。如果封包所屬的frame與其所參考的frames都完全接收時，我們稱此封包為“passed”。而且封包只有在“passed”的情況才可以被轉送出去；否則，這些封包將會被過濾。我們同時也檢測基於不同layer type所制定的優先權策略，並且發現（T（temporal）, D（spatial）, Q（quality））這種priority order能得到最佳的視訊品質。模擬結果顯示，整合CD graph與TDQ priority order的方式能藉由節省傳輸無效封包的空間給予更重要且有效的封包使用，進而有效地提升傳輸效率，並確保視訊播放的品質。

關鍵字

視訊串流；編碼相依性；優先化策略；可調視訊編碼；視訊品質

並列摘要

The multidimensional scalability of H.264/SVC introduces a complexity of the packet prioritization. Different from most of previous works, where layer type is the major metric for prioritization, we vision that the importance of a packet depends not only on its layer type but also on its validity of decoding. Therefore, we proposed a coding dependency (CD) graph to characterize the frame coding dependency for H.264/SVC. The CD graph is employed in an intermediate node, like a mobile gateway, to check the packet validity. A packet is said “passed” only if the packets of its associated frame and its reference frames are completely received. Only passed packets will be forwarded; otherwise, they will be dropped. We also investigated different layer-type-based prioritization policies and found that the (T (temporal), D (spatial), Q (quality)) priority order gives the best picture quality. The simulation result shows that the incorporation of CD graph and the TDQ priority order can improve the transmission efficiency by saving invalid packets transmission for more crucial and valid packets.

並列關鍵字

video streaming ； coding dependency ； prioritization policy ； H.264/SVC ； video quality

參考文獻

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為H.264/SVC傳輸而設計之編碼相依性導向優先化策略

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