以正确的方式进行交互式流:使用HESP进行大规模的超低延迟流

In recent years, the High Efficiency Streaming Protocol, commonly known as HESP, 是否显著提高了大规模超低延迟流的成本效益和性能.

In use cases that require interactivity, 延迟在决定观看者体验质量方面起着至关重要的作用. Interactive scenarios, such as online auctions, live concerts with fan engagement, or interactive TV formats that involve voting, are particularly sensitive to long delays, which can negatively impact the user experience. In some cases, delays can cause missed opportunities, while in others, 内容创建者可能需要在内容中加入人工等待期，以便有时间让观众反馈. 还有一些更微妙的例子，其中延迟会影响用户体验, 比如在观看体育比赛时，面对来自吵闹邻居的潜在剧透, push notifications with score updates, 或者来自朋友的短信，表达他们对发生的事情的兴奋.

HESP is an HTTP-based protocol. 这意味着它可以利用标准内容交付网络(cdn). 这些cdn充当互联网的骨干，并不断交付数十亿美元的资产, ranging from web pages and images to video files, to a global audience. 通过利用这些功能，HESP可以提供任何规模的超低延迟流. 这与其他超低延迟协议(如WebRTC)形成对比, where scaling is complex and expensive, 因为它是通过在后端旋转额外的服务器基础设施来实现的.

Figure 1. 通过HESP的高效率流媒体带来了高质量的观看体验.

通过HESP的高效流不仅提供了大规模的超低延迟. 此外，它还带来了诸如快速通道转换和改进的自适应比特率(ABR)等优点。, 随着网络条件的变化，质量几乎会瞬间改变. HESP的其他优点是与工作室批准的DRM完全兼容, 当工作在广播延迟约5-7秒时，可能会节省成本, as it then provides more time for encoding, compared to protocols such as LL-HLS and LL-DASH.

In its essence, HESP非常简单，对于那些已经在使用流媒体协议(如苹果的HLS或MPEG-DASH)的人来说，感觉很熟悉. During main playback, 流媒体几乎与这些协议相同:媒体播放器只是下载一组媒体片段，然后一个接一个地播放它们. 在HESP术语中，这组片段称为延续流.

HESP的特殊功能可以在所谓的初始化流中找到. 初始化流是一个特殊制作的流，当执行流启动时，客户端将从中加载单个数据包, 或在交替切换时适应网络质量. These packets, for which a numbered, 视频中的每一帧都可以存在单独的可寻址数据包, 包含执行视频启动所需的所有信息…快速. 初始化包通常包含解码器配置, DRM configuration, a full picture frame (I-frame), 以及在延续流中可以找到下一帧的位置的参考.

When a media client wants to start playback, 这个过程非常简单:收集想要开始播放的初始化包，并按照其引用开始下载延续流. Upon receipt of the Initialization Packet, clients can already start retrieving DRM licenses, and render out the first picture to the viewer. 在播放过程中，当客户端到达
延续流，它只是请求下一个，等等，等等. Simple, but efficient.

HESP’s low-latency capabilities stem from the same principle. By allowing startup of a stream on any frame, and by being able to execute this very fast, client buffers required to ensure stability can be reduced, effectively reducing latency as well. In current tests, HESP的生产部署可以在几百毫秒内执行流启动, 允许在低至700ms-900ms的延迟下稳定播放.

如今，提供HESP功能的解决方案数量正在增长. The HESP Alliance, 一个致力于发布和发展HESP IETF规范的行业组织, promoting the protocol, and ensuring inter-vendor compatibility, maintains a growing list of HESP-Ready solutions. 这包括广泛的行业品牌，如编码器和包装从Synamedia和NativeWaves, DRM solutions from BuyDRM and EZDRM, and CDNs from Akamai and G-Core, as well as the THEOplayer media player and the THEOlive real-time streaming platform. 这个生态系统正在进一步扩大，越来越多的公司被列为开发兼容产品的成员: Arena.TV, Ceeblue, Hoki, Mainstreaming, MediaMelon, Scalstrm, SyncWords, and Videon.

Figure 2. 提供HESP功能的解决方案数量正在增长.

Today, HESP技术已经在生产中发现了一组不同的用例，例如现场拍卖, online health and fitness, live event streaming, sportsbook betting, interactive TV, and more. 随着解决方案数量的增加，这个列表可能会扩展成主流内容.

如果你有兴趣了解更多关于HESP的知识，或者对如何开始使用HESP有疑问, please email us at contact@hespalliance.org.

About HESP Alliance

The HESP Alliance, founded by Synamedia and THEO Technologies, 整合流媒体视频供应商和媒体公司，通过标准化和推进高效流媒体协议(High Efficiency streaming Protocol, HESP)以及HESP解决方案的营销，以更低的成本提供卓越的在线视频质量体验.

For more information, please visit www.hespalliance.org.

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