【作者】 王烁；

【导师】 张江陵；

【作者基本信息】 华中科技大学 ， 计算机系统结构， 2004， 博士

【摘要】 目前,数字化和网络化已成为电视台影视播放设备发展的必然趋势。播出系统作为电视台节目面向观众的最后一道关口,直接关系到节目播出的图像质量和可靠性,它是电视台数字化的核心,已成为当前计算机应用技术研究的热点。为了保证播出图像的质量,从数字播放系统的体系结构、关键算法、服务响应时间等方面,进行深入的研究,重点是研究播放系统的可靠性、帧精确性及实时性等关键问题。 组建电视台数字视频播放系统最重要的内容是确立其体系结构,而存储播放子系统是整个系统的核心,它的体系结构设计至关重要。为满足高质量存储播放子系统的高可靠性、高数传率、海量存储容量和可扩展性的要求,我们在理论指导下,对存储播放子系统进行了性能平衡设计,并建立了它的可靠性模型,计算出它的可用度,其性能完全满足电视台停播率的要求。该设计方法与可靠性模型对设计存储播放系统和分析系统性能均具有指导意义。 播出质量是数字视频播放系统一项最重要的技术要求。为了实现无压缩播出和任何制式下的帧精确性。在分析了无压缩数字播放系统的播出工作特性的基础上,提出了一种多线程并行直接 I/O(MPPDIO)存取算法,并建立了计算共享缓冲区大小的模型。实验证明:MPPDIO 存取算法完全能实现无压缩媒体流的不掉帧、无黑场的关键性能,既能保证播放质量,又提高了磁盘 I/O 通道的利用率,降低了 CPU 负载,传统的 PRE_CACHE 顺序存取算法则不能实现系统的这些关键性能。MPPDIO 存取算法也可以在未来用于高清晰度电视的数字播放系统中。 MPEG2 具有压缩效率高的优点,它对电视台业务的大部分应用场合是适用的。我们详细讨论了实现 MPEG2 的数字视频播放的关键技术,提出并实现了冗余双播放缓冲区多线程调度算法,解决了压缩数字播放系统的帧精确和节目间平滑转换的问题。指出:该算法既不影响播放帧的及时处理,又不使预解码数据量受播放缓冲区限制;与现有的压缩播放系统靠双解码卡以硬件实现帧精确与平滑转换相比,具有巧妙性,成本低和可推广性。电视台需要对某些直播节目进行实时监控,要在对节目进行审阅后,延迟一段时间再播出,以满足电视台的特殊要求,因此有必要研究延迟播放技术。目前的延迟播放系统大多由大规模集成电路实现,价格昂贵,国内也较罕见,针对这种情况,我们在分析比较了四种不同处理方案的特点的基础上,另辟蹊径,提出了利用磁盘缓存共1本文受国家自然科学基金资助,批准号 69973017、60273074。 I<WP=4>享压缩视频文件来实现延迟播放的新方案,并创建了一种最优算法。使用此算法可以有效地实现延迟播放功能,且不存在延迟时间限制的瓶颈,用软件实现,所需代价最小。播放系统在播放节目文件时存在实时格式转换的需求,以往的格式转换要么通过底层硬件电路实现,要么通过工具软件实现,两者都不能满足系统的需求。因此我们提出了一种多线程流水调度算法,根据 VOB 文件特点,对文件格式转换的解复用、编码、复用等环节进行优化,较好地实现了 DVD 文件、VCD 文件转换到 MPEG2 文件的混合无掉帧实时播放。实验结果表明有以下三点好处:针对 VOB 文件特点的解复用器比通用解复用器提取音视频流的耗时要小得多;采用编码优化算法使得编码时间远小于播放时间及未优化算法的编码时间;DAT 文件及 VOB 文件到 MPEG2 文件的格式转换及混合播放,可达到帧精确。在节目的播放过程中存在临时更改节目单的情况。为实现播出时能实时修改节目单,有必要分析播放系统服务响应时间。在分析影响播放系统服务响应时间的因素之后,建立了计算其服务响应时间的数学模型,得出节目单条数、磁盘阵列的磁盘数与分块大小对系统服务响应时间的影响程度。并针对影响系统服务响应时间的因素,提出了四条相应的改进措施,使系统服务响应时间达到可能的最小值。更多还原

【Abstract】 Current, broadcasting movies and TVs in the television station has inevitablydeveloped into digital and network age. Broadcasting systems are the last part beforetelevision station program faces to the audience, relating to directly picture quantity andreliability of the program broadcasting. It is a core that television station’s digital turn,having become a highlight of research on computer application. For the sake of guaranteethe picture quality of program broadcasting, the key problems such as reliability, frameaccurateness and real-time performance are studied from the hardware architecture, the keyalgorithm and the response time etc. aspect of digital broadcasting systems. The architecture of digital broadcasting systems is the most important issue of buildingthe digital broadcasting systems. Its core is the storage and broadcasting sub-systems, andthe design of architecture of the storage and broadcasting sub-system is a key. For satisfythe high reliability, the high data transfer rate, the mass storage capacity and scalability ofthe high quality storage and broadcasting sub-system, its performance balance design hasbeen done and its reliability model is built based on the theory. Its availability cancompletely meet the requirement of TV Station. The design mothed and the reliabilitymodel can serve as a guide to the design and performance analysis of the storage andbroadcasting system. The broadcasting quality is one of the most important technology issues in the digitalbroadcasting systems. To realize frame precision when broadcast, an algorithm calledMPPDIO (multi-thread parallel pre-fetch Direct IO) is proposed after the characters of thebroadcasting part in uncompressed digital broadcasting system are analyzed. The size of thesharing buffer between multi-threads is modeled and calculated. Experiment results indicate that the traditional pre-cache sequence algorithm can’tmeet the need of performance, and the MPPDIO algorithm not only can perfectly satisfy theperformance requirements but also can improve the utilization of disk I/O channel andreduce the load of CPU. The MPPDIO algorithm can use in the digital broadcastingsystems on HDTV later. The MPEG2 has the advantage of high efficiency in compression; it is suitable for lotof applications of the television station business. The key techniques of digital broadcastingbased on MPEG2 are discussed in detail. A redundancy playing buffer multi-threadingscheme is put forward, and it realizes the frame precision and smooth switch betweenprograms. The scheme doesn’t affect both processing playing frame and the pre-decodeing1This research work was supported by the National Science foundation of china under grant 69973017 and 60273074 III<WP=6>on frame. It is smarter and costs lesser compared with the current mothed to realized theframe precision and smooth switch between programs by hardware. Some live program must be monitored and delay played to satisfy the special realdemand in television station. It’s necessary to research the delay playback technology. Thecurrunt delay playback systems are implemented by LSI and cost huge. We put ingeniouslyforward a scheme realized by share the compression file in disk buffer, after analyzing andcomparing the performance of four kinds different handling methods. This method canrealize availably the function of the delay playback, has no bottleneck in delay timerestriction, and costs least. The digital broadcasting systems demand the real time conversion of file format whenbroadcasting programs. The past conversion of file format is implemented by hardware orsoftware tool, which can’t meet the requirment of the system. A kind of real timeconversion method fulfilled by the multithread pipeline scheme algorithm is proposed.According to format characteristics of VOB file in the DVD, each link in conversion thefile format—demultiplex, code and multiplex, is imp更多还原