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[摘要] 本文阐述了基于DAB(Digital Audio Broadcasting)系统发展起来的韩国数字多媒体广播国家标准T-DMB系统的设计及实现情况。文章开始简要地介绍了T-DMB诞生的缘由,接着 较为详细地介绍了其在移动电视业务处理上所使用的一些技术,包括H.264、MPEG-4、MPEG-2 TS等,最后介绍了DMB在我国的发展情况,以及展望了其作为手机电视播放平台的市场前景。9月份去哪里旅游比较好 国内
一. 引言
随着人们生活水平的不断提高,人们对信息消费多元化的趋势亦趋明显。传统的固定地面电视广播已难以满足人们的消费需求,人们不仅希望可以随时随地的收看高 清晰画面的视频广播,还希望可实时的接收一些诸如数据、图片、声音、股市财经等信息。在韩国,由于他们使用了美国数字电视标准ATSC对其国内地面电视广 播业务进行数字化,而这种标准无法支持移动电视业务。在人们对移动电视业务需求日趋增长的情况之下,韩国人在经过两年多时间对目前现有可用的地面广播技术 标准进行一番精心比较分析后,最终选择了DAB Eureka-147欧洲标准作为韩国开展地面手机电视业务的传输标准,并由此确立了韩国的地面手机电 视国家标准T-DMB。
T-DMB作为对DAB标准的继承与发展,除了采用DAB标准原先所使用的相关技术外,为了进行视频广播,还使用了一序列新技术。包括在视频压缩上采用了 适合低比特速率视频业务的视频编码标准MPEG-4 AVC/H.264,节目伴音压缩则采用BSAC,数据交互使用BIFS。DAB与MPEG-4技术的成功结合有效地解决了人们对数字移动电视业务的需 求。DAB Eureka-147作为第一个为对地面声音广播进行数字化开发的标准,完成于1994年,发展至今已成为一个非常成熟的技术标准,目前已被欧洲和其它一 些国家和地区,包括中国、韩国、加拿大、台湾、澳大利亚等采纳作为实施本国地面声音广播数字化的获选方案。目前,在欧洲国家尤其是英国,DAB的芯片和接 收机在市场上随处可见,种类也非常齐全,价格也比较合理。由于从标准设计开发一开始,DAB标准就是为向固定、可持及移动设备广播声音业务而开发的,所以 非常适合于移动电视业务。DAB系统可提供高达1.824Mb/s的比特率用于声音广播跟数据业务。时至今日,DAB系统已经能够提供包括动态文本、幻灯 片、广播Web站点和其它一些与声音相关或无关的业务。尤其是在复用方面,DAB允许在其独立的数据子信道中进行流模式运用,这一特点成为韩国人发展T- DMB的突破口。 二. DAB到DMB的发展
从目前的DAB系统过渡到DMB,无需对现存的DAB广播前端进行任何改动,只要在前端设备上引入一个DMB视频编码器。就可以实现从DAB到DMB的过 渡。图1所示为韩国T-DMB的结构层次图。从图中可以看出,DMB系统中仍延用了DAB的整个系统,只是在DAB的MSC(主业务信道)中划分出一个独 立的子信道用于视频业务。而像原先DAB中所固有的声音业务,数据业务都保持不变,这也使得DMB的部署相对较为容易。而新增的视频业务则主要通过前端的 DMB视频编码器来实现,视频编码器编码产生的数据流,以ETI(复合传输接口)信号形式通过DAB的复用器以流模式方式复用到子信道中去,与来自其它 路的音频或数据复用成高达2.048Mb/s的ETI传输数据流,然后将ETI数据流分配给DAB同步网中的各个发射台进行发射。
随州旅游景点大全
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)
图1 T-DMB结构图
1.音视频编码处理
韩国T-DMB标准采用了在限定带宽内仍能提供高效压缩性能的压缩标准MPEG-4 AVC视频压缩标准。而在视频伴音压缩标准的选择上,则采用专利使用费相对较低的MPEG-4 BSAC音频压缩标准而非AAC+。对于视频播放中伴随的一些数据业务或需要提供一些交互应用的场合,则使用了MPEG-4 BIFS编码。为了便于商用接收机的开发,T-DMB使用MPEG-4压缩标准中所需解码处理能力相对较容易的架构。图2示出了DMB对视频业务的处理流 程。
图2 DMB视频业务处理流程图
从该框图可以看出:在DMB视频编码器中,使用了MPEG-4 system部分的标准对分别采用H.264编码的视频,BSAC编码的伴音以及BIFS编码的交互数据内容进行同步。首先使用MPEG-4 SL(同步层)数据包格式对视频、伴音以及交互数据进行封装,进而把同步包复用到MPEG-2 TS传输流中。然后再进行前向纠错,最后以流模式方式复用到DAB系统中。使用的前向纠错技术包括RS编码,卷积交织技术。采用前向纠错技术的主要原因就 是提高数据流的抗误码性能。因为DAB获得好的声音质量要求的比特错误率(BER)是不大于。然而在DMB中,要实现接收端对视频业务的稳定可靠接收,比 特错误率(BER)的要求高达。为了满足这一要求,韩国T-DMB标准使用了在DVB-T标准中也使用的前向纠错技术(FEC)。即使用RS(204, 188)对MPEG-2 TS打包流进行编码然后再进行卷积交织。每188字节的TS包经过RS编码变成204字节的包,其中有16字节是纠错编码。经过编码之后,每隔11个RS 编码的数据包作一次卷积循环,这样就可以把在时间域中突发的错误分散在各个部分,减少了连续错误出现的概率。通过使用前向纠错技术,可以有效地保证视频流 的BER低于。
2.DMB网络结构
一种比较常见的DMB应用情况是在一个1.534M带宽的DAB频率块中,同时广播两套音频包括与音频相关的数据和一套手机电视视频业务。DMB的网络结 构层次图如图3所示。DMB的视频业务以流模式方式进入DAB系统的第一级复用器并打包形成ETI信号,再与其它路的音频或数据业务经二级复用形成发射所 需的ETI信号,送到各发射站点的激励器进行放大发射。或者是不需使用第一级复用器,而直接把信号送到第二级复用器或称为总成复用器中,该种使用情况是在 DMB视频编码器中已集成了一级复用模块在编码器中。在图3中,还列出了DMB所使用的编码标准及复用的标准。
图3 T-DMB网络结构
三. DMB前端编码器的设计实现
DMB系统作为对DAB系统的发展,其最大的不同就是增加了视频业务。这一业务的实现所带来的改变是在发射前端部分增加了DMB视频编码器。该视频 编码器完成的功能是对视频、伴音及交互数据进行编码、各种码流之间的同步、RS编码、卷积交织功能。目前这种编码器韩国OTT公司跟PIXTREE公司已 有可商用的产品出来,并且是基于硬件实现的实时编码器。其音频跟视频的压缩通过两块DSP实现,数据流的输入输出控制则由一块CPU负责。该编码器目前已 达到商用水平,而在我国目前还没有国产的同类产品出现。该编码器所实现功能的详细处理过程如图4及图5所示。
坦桑尼亚时差>泰国芭提雅洋妞多少钱
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)
图4 视频业务复用层次结构图
图5 视频业务编码输出打包流程
它的工作原理是:通过sl打包模块把经过压缩的各种视频、音频及交互数据基本码流打包成同步包,主要是加入一些时间标签及参考时基用于接收端播 放时各码流的同步。打包完成后的SL打包流再经过MPEG-2 PES打包形成PES流,最后再打包成TS包。之后完成对TS传输包的RS编码及卷积交织,增强其抗误码性能。在编码器设计过程中,我们使用了一种纯软件 方式的外层打包解决方式。就是以MPEG-4 IM1工程组提供的参考软件为基础,在VC++环境下开发SL Packetizer软件模块,该模块负责对由DSP压缩编码输出的音
视频基本流(Elementary Stream)进行封装,主要目的是加上各自所对应的时间标签用于播放器端码流间的同步。之后再经过PES Packetizer模块进行PES的封装及后续的各项处理。该软件实现基本上可以完成DMB编码器所需实现的功能,但不足之处在于实时性效果不好,跟韩 国的硬件编码器编码输出比较存在较大的延迟现象,稳定性方面也需改进。
四. DMB在国内的发展旅游节门票半价上海
在国内,目前已有北京、上海及广东的佛山等地在试播DMB业务,佛山的DMB系统主要是由1996国家在广东建立的DAB先导网发展而来,并由几家广东省 广电系统企业合资组成粤广数字多媒体有限公司。该公司原先使用的是采用微软公司WME9进行编码的DMB,后来由于H.264技术的不断发展成熟以及韩国 DMB产业进程相对比较快而改用了韩国基于H.264编码的T-DMB方案。此两种不同编码方式的DMB最显著区别就是在视频编码的压缩率上有比较大的不 同。WME9作为微软公司自己所拥有知识产权的标准,其在DMB方面的应用都是基于软件编码的,通过Windows 2000 Server自带的多播站来完成整个前端的编码处理,压缩率较小但系统兼容性方面相对较好。而基于H.264编码的T-DMB标准,主要
应用于小屏幕低码 率的场合,因此被推荐为手机电视的标准之一,与3G所推出的手机业务的显著区别就是其价格优势。3G中所提供的手机电视业务要同时占用上下行信道,在带宽 昂贵的今天,用户所需要承担的费用就十分庞大,而基于T-DMB标准的手机电视则是一种双网合一的模式。既有移动运营商的网络又有广电系统的网络,这种广 播式的手机电视业务不会占用有限的信道资源,相比之下,业务价格就可以显著降低;再者在业务的交互性方面,可以利用电信网的良好交互性能,实现用户与服务 器之间的交互。所以相对来讲,这种基于广播式的手机电视的应用前景更为明朗,而作为DVB组织所推出的手机电视标准DVB-H目前仍处于研发阶段,至今仍 没有成熟的产品推向市场。不同的是,T-DMB目前已有从前端到终端的整套产品,并且是由成熟的DAB系统发展而来的,技术可靠性更有保障。像韩国的三星 及LG公司已相继推出自己的基于T-DMB方案的手机电视终端,该类产品可以同时具有手机的一切功能,又可以收看电视节目,极大了满足了用户的需求。据上 海文广集团下属企业东方明珠预计,未来5年内国内DMB业务带来的产值就可达到2000亿元左右。