Scalable video coding (SVC) is an extension of some target codec design. The objective of SVC is to enable the encoding of a single video bit stream that contains one or more substreams that can themselves be decoded with complexity and reconstruction quality similar to that achieved using the target codec design with the same quantity of data as in the substream. The substream is derived by dropping packets from the larger bitstream. A substream may represent a lower spatial resolution, or a lower temporal resolution, or a lower quality video signal as compared with the bitstream it is derived from. For the H.264/AVC standard, for instance, the usual modes of scalability are temporal, spatial, and quality scalability. Currently, some video experts have started to pay attention to the scalable extension of High Efficiency Video Coding (HEVC). Recommended requirements and test points for the scalable extension of HEVC have been discussed and briefly listed as follows:
 
1. Spatial Scalability
2. SNR scalability
3. Temporal scalability
4. Aspect Ratio
5. Robustness to transmission errors and congestion (Error Resilience)
6. Bit Depth
7. Chroma Resolution
8. Region Of Interest (ROI)
9. Combined scalability and complexity
10. End-to-end delay and latency
11. Random access
12. View Scalability for 3D Video
 
Our goal is to develop some techniques for the scalable extension of HEVC. (Reference: m21100)

可調式視訊編碼(SVC)可視為某個特定編解碼器設計的擴充,其目標是讓單一視訊壓縮串流能夠同時包含一個或多個子串流,讓他們自己可以各自解碼出與該特定解碼器設計有著相似的複雜度和重建品質的視訊。子串流可由更大的資料串流丟棄數據包而得。相較於整個資料串流而言,一個經過解壓縮的子串流可能就代表了一個具有較低畫面解析度、較低畫面更新率,或較低品質的視頻信號。以H.264/AVC標準為例,其包含了時間,空間和品質三種常見的可調性。目前,一些視頻專家已開始關注高效率視頻編碼(HEVC)於可調性效能的擴充。已針對其需求和測試條件進行了討論,簡要列出如下:
 
1.空間可調性 - 應支援2層或更多層,每層有不同的畫面解析度。
2.SNR可調性 - 應支援具有相同畫面解析度和更新率,但不同的位元率的層級。
3.時間的可調性 - 應支援具有不同的畫面更新率的層級。
4.縱橫比 - 應支援不同的圖像的跨層縱橫比(PARs)。
5. 針對傳輸錯誤和擁塞的穩健性(容錯) - 相較於單層HEVC,應加強對於容易出錯或擁塞的通道傳輸時的效能。
6.位元深度 – 當HEVC於單層壓縮時能支援高於8位元深度,再來重新檢視。
7.色彩解析度 - 當HEVC於單層壓縮時能支援4:4:4解析度,再來重新檢視。
8.感興趣區域(ROI) - 待定。
9.結合可調性與複雜度 – 應可支援於單一位元流支援多種可調性能的結合。
10.點對端的延遲和等待時間 – 至少應使從同一端點到另一端點的延遲和等待時間跟單層的HEVC一樣。
11.隨機存取 – 應允許具有至少跟單層HEVC相同的隨機存取性質。
12.三維圖像的視野可調性 – 應當支援視野可調性。
 
我們將致力於開發HEVC可調性的相關技術。

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