标题: | 异质无线网路之可扩充性多媒体群播服务(Scalable Multimedia Multicasting Services over Heterogeneous Wireless Networks)-运用在异质无线网路多方视讯广播服务之可调视讯编解码最佳化与网路介面设计 Optimization and Network Interface Design of Scalable Video Coding for Multicasting Services over Heterogeneous Wireless Networks |
作者: | 彭文孝 PENG WEN-HSIAO 国立交通大学资讯工程学系(所) |
关键字: | 可调视讯编码;多方视讯广播服务;异质无线网路;可调视讯编码快速演算法;Scalable Video Coding,Video Multicasting,HeterogeneousWireless Networks,Fast Algorithm of Scalable Video Coding |
公开日期: | 2009 |
摘要: | 本计划之目标为针对整合计画“异质无线网路之可扩充性多媒体群播应用(Scalable Multimedia Multicasting Service Over Heterogeneous Wireless Networks)”,进行可调视讯 编码最佳化,与开发可调视讯编码之网路介面。 随着视讯编码与传输技术的快速发展,可调性多媒体群播(意指在不同的传输通道 中,发送单一可调位元流给予不同使用者)对于遍地即时之多媒体通讯应用而言,已成 为一个可行并实际的做法。可以预期的是,在不久的将来,使用者不仅可以在不同多媒 体平台上观赏视讯,并且能够藉由不同网路协定与连结方式来存取伺服器。为了能够支 援多样的使用者需求与不断变化的网路环境,ISO/IEC MPEG 与ITU-T 组织了一个JVT 团队来制定可调视讯编码标准技术,其目的是以单一的视讯位元流提供空间上 (Spatial)、时间上(Temporal)以及画质精细(SNR)可调的特性。目前,可调视讯编码提供 了一个可完全相容于MPEG-4 AVC/H.264 之基本层,以及一个可以被即时舍弃与切割来 达到不同时间,空间,与画质解析度之可调层。 尽管可调视讯编码能够提供诸多可调性特色,然而却也在伺服器端(Servers)、媒体 转接器(Media Relay)与接收端(Receivers)带来不同的困难与挑战。对伺服器而言,可调 视讯编码之高复杂度对于即时应用是一大挑战。初步分析指出,目前最新的参考软体即 使在最快的机器上作编码,其速度距离即时条件仍有1000 倍之差。另外,连接伺服器 端与接收端之媒体转接器必须持续不断的随着不同接收端需求与网路环境作适应性的 位元流调整。因此,为了能够让网路封包作即时的应用,伺服器必须适当地在封包内加 入优先权资讯,藉以辅助媒体转接器对位元流的撷取。尽管目前可调视讯编码已在网路 撷取层(NAL)中提供简易的优先权资讯,但是现有方法并无法同时满足不同接收端之需 求。因此,在此方面仍有许多研究空间。再者,对于低阶之可携式接收器,媒体转接器 甚至必须提供从可调视讯编码转换至MPEG-4 AVC/H.264 编码之能力。因此,在媒体转 接器上,另一个值得探讨的问题是如何兼顾转码复杂度与转码品质。而另一方面在接收 端,其主要议题则在于如何根据影像特性与拨放器能力,有效地利用已接收之位元流作 最佳解码,并在错误发生的状况下提供优雅解码品质。 根据上述之问题,在本计画中我们将研究并开发适用在异质无线网路环境下之可扩 充性多媒体群播应用相关技术。同时所提之技术将在展示系统与最新的参照软体中验 证。以下是各年度之计画目标:第一年 -- (1)发展快速演算法,改进目前可调视讯编解 码之速度,(2)根据可调视讯之传输需求,发展网路介面;第二年 -- (3)根据可调视讯编 码标准与MPEG-4 AVC/H.264标准两者之语法定义,发展转码技术,以及(4)最佳化位元 流撷取技术;第三年 -- (5)提供可调视讯解码错误容忍与(6)错误隐藏机制。 This subproject aims at optimizing the scalable extension of MPEG-4 AVC/H.264 and developing associated network interface for the scalable multicasting service over heterogeneous wireless networks. With the rapid advances of video coding and transport technologies, the scalable multimedia multicasting ─ the ability to deliver multimedia data streams from a single encoding source to a wide range of receivers through different communication channels ─is now a feasible and practical solution to pervasive real-time multimedia communication and entertainment. It can be foreseen that the users in the near future can not only watch the live videos on various multimedia platforms, but also access the services by different types of connections. In order to support clients with diverse capabilities and varying network conditions, ISO/IEC MPEG and ITU-T form a Joint Video Team (JVT) to develop a scalable video coding (SVC) technology that uses single bitstream to provide multiple spatial, temporal, and quality (SNR) resolutions. It provides a H.264/AVC-compatible base layer and a fully scalable enhancement layer, which can be truncated and extracted on-the-fly to obtain a preferred spatial-temporal and quality resolution. While the SVC offers many attractive features, it comes with different challenges at servers, media relays, and receivers. At servers, the highly computational complexity of SVC encoder puts up a barrier in the real-time applications. The preliminary analysis has shown that the up-to-date reference software is 1000x slower than real-time when executed on the state-of-the-art machines with combined scalability enabled. Besides, as the bridges connecting servers and receivers, the media relays need to constantly adapt the SVC bitstream for matching device capabilities and network conditions. To allow the packets be parsed in a real-time manner, servers must embed the priority information to facilitate the bitstream extraction. Although the current algorithm provides simple priority identification in the SVC network abstraction layer (NAL), it cannot simultaneously fulfill the requirements of different devices, and thus, leaving plenty of research spaces for further improvement. In addition, the media relay may sometimes perform the transcoding from SVC to MPEG-4 AVC/H.264 for low-complexity portable devices. Thus, how one can minimize the complexity while maintaining the quality of transcoding is another issue at media relays. On the other hand, at receivers, the problem is how to smartly utilize the received bitstream according to the video characteristic and display capability so as to optimize the decoded quality and provide graceful degradation in the presence of packet loss. In terms of the problems raised, in this project, we will accordingly investigate and develop related technologies, and validate the proposed schemes with the up-to-date reference software and in the demonstration system. The yearly goals of this project include: Year 1 -- (1) design fast algorithms for SVC encoder and (2) develop network interfaces for the transport of SVC. Year 2 -- (3) develop SVC to MPEG-4 AVC/H.264 transcoder based on syntax direct mapping and (4) provide rate-distortion optimized bitstream extraction scheme. Year 3 – (5) offer SVC decoder with graceful degradation and (6) propose error concealment scheme for SVC. |
官方说明文件#: | NSC96-2628-E009-015-MY3 |
URI: | http://hdl.handle.net/11536/100875 https://www.grb.gov.tw/search/planDetail?id=1734060&docId=296897 |
显示于类别: | Research Plans |