Industry Experts Discuss the Future of MPEG-DASH at NAB
“More important than anything else, DASH enables interoperability,” said Iraj Sodagar, a principal multimedia architect at Microsoft and the DASH Industry Forum (DASH-IF) president. “DASH的整个想法是收集市场上部署最好的流媒体技术, adding more to it, and creating a standard for interoperability."
第一版核心标准于2012年4月发布, Sodagar noted, adding, “The second edition of MPEG-DASH, which extends the functionality of the first edition, is about to published by ISO/IEC.” Sodagar is also the MPEG-DASH subgroup chair.
Sodagar made these comments during the DASH Talks, 这是上周在拉斯维加斯举行的NAB会议期间在万丽酒店举行的一次活动, Nevada. Will Law, an architect at Akamai, presented and hosted the talks. Setting the stage, 法律提醒观众在DASH承诺之前传统玩家环境的局限性.
“今天的内容所有者必须创建和管理12个或更多的玩家才能接触到大多数用户,” Law said. Flash Player提供了一个单一的播放器应用平台. It is still dominant on desktop/laptop devices today, but the rise of mobile devices without Flash support, such as phones and tablets, has fractured that player space.”
Law指出，这不仅是因为玩家的要求不同, but also differing development and player environments.
“智能电视都有不同的应用程序开发环境，”Law说. “Connected devices such as Roku, Apple TV, Chromecast, have separate player environments, and game consoles such as the PS4, Xbox One, Nintendo, require separate players.”
Several speakers focused on areas where MPEG-DASH, as a relatively new standard, 需要增强功能以赶上更多专有解决方案, even for HTML5-based players.
其中一个领域是使用浏览器扩展来保护内容. Lumped together, these are known as encrypted media extensions (EME) 哪一个是W3C的标准，正在被集成到DASH标准中. DASH中的EME提案通过提供api来控制受保护内容的播放，从而扩展了HTMLMediaElement.
这种通用eme的使用类似于通用加密方案(CENC)，后者被纳入DASH标准的第一版. However, eme为媒体服务(如Adobe Primetime和Microsoft Azure media services)提供了额外的好处，这些服务本身使用受保护的sdk (psdk)来保护内容.
“该API支持从简单的清晰密钥解密到高价值视频的用例，并提供适当的用户代理实现," a DASH Talks slide noted. "License/key exchange is controlled by the application, 促进支持一系列内容解密和保护技术的健壮播放应用程序的开发.”
小组成员还讨论了在DASH中加入广告插入的问题. InterDigital’s Alex Giladi touched on two types of architectures, 一种是应用驱动的，另一种是服务器驱动的, as well as linear workflows for each.
For the app-driven model, Giladi指出，这需要将现有的工作流程转换为DASH, 哪一组标准足够健壮，可以处理这两种类型的工作流.
DASH客户端和广告拼接器是客户端应用程序中的模块,” Giladi said, 注意DASH事件用于传输提示消息, including user-defined events as “timed blobs.”
“Cue events are essential,” one of Giladi’s slides stated. 不支持特定球杆格式的DASH客户端无法播放内容.”
Giladi showed how different types of cue messages, including the ubiquitous SCTE 35 cue message, could be carried in DASH.
DASH Talks和NAB展会上的一个热门话题是对符合DASH标准的玩家的需求. Michael Luby of Qualcomm 展示了两种技术:一种即将问世，另一种已经被高通的至少一家主要OEM客户采用. 已经实现的技术是硅内DASH客户端，作为高通长期演进(LTE)移动芯片组的一部分而设计.
“我们的多播服务设备客户端符合3GPP Rel-9规范, and our DASH client is integrated to MSDC,” Luby said.
MSDC中的DASH客户端已经在骁龙800芯片组上, Luby said, 他补充说，高通的一个关键卖点是MSDC和骁龙LTE调制解调器之间的紧密集成, 包括从网络获取准确时间的API扩展, 这在单播和多播环境(如eMBMS)中都是至关重要的.
“我们正在将eMBMS支持扩展到所有支持LTE的骁龙设备上,” Luby said, 韩国电信于2014年1月推出了商用LTE/eMBMS服务。. 目前正在澳大利亚、欧洲和美国进行的试验仍在继续.
View the full DASH Talks.
Related Articles
广播公司想要的是经得起时间考验的可靠标准. 他们不想要的是定期改变他们的整个视频工作流程.
04 Aug 2014
DASH将成为向HTML5浏览器传送内容的最可靠的方式, says an Adobe software architect.
29 May 2014
随着MPEG-DASH的兴起以及微软和Adobe在这一主题上的nabb相关公告, 我们与两家公司坐下来讨论了DASH支持的现状以及他们的传统ABR协议, Smooth Streaming and HDS
08 Apr 2014
MPEG-DASH正在缓慢但肯定地成为HLS的主要竞争对手, 由主要参与者的采用和内在优势驱动. 下面是哪些人正在使用它，哪些人将很快使用它，还有哪些挑战需要解决.
08 Apr 2014
软件视频处理开发人员为NAB提供了六个4K演示, is partnering with Ericsson EVE, and claims to be the fastest growing vendor around
05 Apr 2014