兼具高傳輸效率與容錯韌力之異質多層次多媒體群播服務(II)

Abstract

本計畫乃一項由國科會資助正在執行中之研究第二、三兩年的延續。 從2008年夏，本團隊從網際網路、視訊壓縮、通道/網路編碼等方面開始研發兼具高傳輸效率與容錯韌力之異質多層次多媒體群播服務。我們希望在位元率-失誤最佳化、封包遺漏補救、影傳輸延遲縮短等方面對視訊串流技術作進一步的改善。本計劃使用H.264可調式影片編碼(Scalable Video Coding, SVC)標準將影像序列編碼成各層間相關的網路抽象層(Network Abstract Layer)單位並允許不同的播放裝置能按自身網路頻寬與處理能力調整影像的接收與播放。此外，我們將使用多重樹狀應用層(Application-layer multicasting)根據各別的位元率播放優先權與重要度使用不同的網路途徑來傳遞不同的SVC層。我們並將使用多維度通道編碼及線性網路編碼技巧將提供不同的SVC層非均等抹除保護,使接收端只收到片段資訊的情況下,回復完整資訊。 在視訊串流技術研究上,我們將全力解決SVC串流的兩個主要問題：

This proposal describes a two-year continuation of an on-going research currently funded by the National Science Council. Since the beginning of 2008, we, a team of researchers in internetworking, video compression, channel and network coding, started our work on the necessary technology to provide rate- distortion optimized, packet loss resilient and transport latency minimized video streaming to a wide variety of viewing devices scattered over the public Internet. The scalable heterogeneous video multicasting services will be made possible by transporting scalable video coded bitstreams through a multipath application-layer multicasting (ALM) overlay network with the use of unequal erasure protection (UEP) codes. The H.264 Scalable Video Coding (SVC) standard enables video frames to be encoded into interdependent layers of network abstraction layer (NAL) units and permits viewing devices to adapt their video reception and playback according to device capability and network performance. A multipath application layer multicasting (ALM) network, on the other hand, can pass different SVC layers along different paths based on their rate-distortion performance. Finally, multi-dimensional channel coding and linear network coding techniques will provide unequal erasure protection to the SVC layers and thus enable erasure recovery during partial reception. After a survey of state-of-art video streaming techniques, we decided to focus our efforts on two specific challenges of SVC streaming: 1. Rate-distortion optimized SVC multicasting over multi-mode wireless networks ― this effort aims at providing the viewing devices that have two radio links with rate-distortion optimized degradation of viewing quality when they experience signal fading and band-width fluctuation over their radio channels. Our goal is to have the rate-distortion per-formance of playback during poor reception closely tracks that of the encoded video with-out unnecessary complication of the radio channel assignments for the video multicasting sessions. 2. Latency-Minimized Bandwidth-Efficient AVC/SVC Transport over public Internet ― this effort aims at achieving sub-second end-to-end video transport latency across the public Internet while maintaining a relatively frugal consumption of Internet bandwidth. Our approach calls for a distributed implementation of AVC-to-SVC transcoding with the aid of supplementary encoding information embedded in the forwarding bitstreams. It will also use linear network codes with unequal error protection capability to achieve loss- resilient and latency-reduced SVC transport. This project will pursue the following technology innovation: