Doing Interactive Streaming the Right Way: Ultra-Low Latency Streaming at Scale With HESP

近年来， 高效流协议, 通常称为HESP, has significantly enhanced the cost-effectiveness and performance of large-scale ultra-low latency streaming.

在需要交互性的用例中, latency plays a crucial role in determining the viewer quality of experience. 互动的场景, 比如网上拍卖, 有粉丝参与的现场音乐会, 或涉及投票的互动电视形式, 对长时间的延误特别敏感, 哪些会对用户体验产生负面影响. 在某些情况下, 延误会导致错失机会, 而在其他国家, content creators may need to incorporate artificial waiting periods into their content to allow time for viewer feedback. There are also more subtle examples where latency can affect the user experience, such as when watching a sports game and facing potential spoilers from sources like noisy neighbors, 带有分数更新的推送通知, or text messages from friends expressing their excitement about something that has happened.

HESP是一种基于http的协议. This means it can leverage standard content delivery networks (CDNs). These CDNs serve as the backbone of the Internet and are continuously delivering billions of assets, 从网页和图像到视频文件, 给全球观众. By leveraging these capabilities, HESP can provide ultra-low latency streaming at any scale. This is in contrast with other ultra-low latency protocols such as WebRTC, 哪里的扩展既复杂又昂贵, as it takes place through spinning up additional server infrastructure in the backend.

图1. High efficiency streaming through HESP brings a high viewer quality of experience.

通过HESP高效流 does not only provide for ultra-low latency at scale. It additionally brings benefits such as fast channel change and improved adaptive bitrate (ABR), almost instantly changing qualities upon changing network conditions. Other benefits of HESP are full compatibility with studio-approved DRM, and the possibility of cost savings when working at broadcast latencies of about 5–7 seconds, 因为它为编码提供了更多的时间, 与LL-HLS和LL-DASH等协议相比.

本质上, HESP is quite simple and feels familiar to those already working with streaming protocols such as Apple’s HLS or MPEG-DASH. 主播放期间, streaming is nearly identical to that of these protocols: A media player is simply downloading a list of chunked media segments and playing them one after the other. This group of segments, in HESP lingo, is called the Continuation Stream.

The special sauce of HESP can be found in the so-called Initialization Stream. The Initialization Stream is a specially crafted stream from which a client will load a single packet when performing stream startup, or when switching between alternative qualities to adapt to the network. 这些包, 一个数字, individually addressable packet can exist for each frame in the video, contain all the 信息 required to perform video startup… fast. An Initialization Packet will often contain decoder configuration, DRM的配置, 全画框(I-frame), and a reference to where in the Continuation Stream the next frame can be found.

当媒体客户端要开始播放时, the process is very simple: You collect the Initialization Packet where you want to start playback and follow its reference to start downloading the Continuation Stream. 收到初始化包后, 客户端已经可以开始检索DRM许可证, 并将第一张图片呈现给观看者. During playback, when the client reaches the end of a segment in the
Continuation Stream, it simply requests the next one, and so on, and so on. 简单，但高效.

HESP的低延迟能力源于同样的原理. 通过允许在任何帧上启动流, 通过非常快地执行, 可以减少确保稳定性所需的客户机缓冲区, 有效地减少了延迟. 在目前的测试中, production deployments of HESP can perform stream startup within a few hundred milliseconds, allowing for stable playback at latencies as low as 700ms–900ms.

Today the number of solutions that offer HESP capabilities is growing. HESP联盟, an industry body dedicated to publishing and evolving the HESP IETF specification, 推进协议, 并确保供应商之间的兼容性, 维护一个不断增长的HESP-Ready解决方案列表. This includes a wide range of industry brands such as encoders and packagers from Synamedia and NativeWaves, DRM解决方案 BuyDRM and EZDRM，以及来自 Akamai and G-Core，以及 THEOplayer 媒体播放器和THEOlive实时流媒体平台. The ecosystem is expanding further with an even broader set of companies listed as members working on compatible products: Arena.TV, Ceeblue, Hoki, 主流化, MediaMelon, Scalstrm, SyncWords, and Videon.

图2. The number of solutions that offer HESP capabilities is growing.

Today, the HESP technology can already be found in production for a notable group of different use cases such as live auctions, 在线健康和健身, 活动直播, sportsbook赌博, 交互式电视, 和更多的. This list will likely exp和更多的 into mainstream content as the number of solutions increases.

If you’re interested in learning more about HESP or have questions about how to get started with HESP, 请电邮至 contact@hespalliance.org.

关于HESP联盟

HESP联盟, 由Synamedia和THEO Technologies创立, brings together streaming video vendors and media companies to provide superior online video quality of experience at reduced cost through standardizing and advancing the 高效流协议 (HESP) and marketing of HESP solutions.

欲了解更多信息，请访问 www.hespalliance.org.

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