Video for the Long Haul: Exploring Backhaul Options

You’re streaming a high-profile event in the not-too-distant future, 您想知道将视频传输到流媒体服务器或服务提供商的选项. You’re concerned about quality, reliability, and perhaps redundancy. You’ve read about satellite and fiber, 以及通过IP网络有效传输的多种选项, but you’re not sure what they require in terms of equipment and cost. If this in any way describes your situation, you’ve come to the right place, 因为这些回程选项正是我将在本文中介绍的内容.

Let’s start with some assumptions. 首先，您不需要对现场实际分发的流进行编码. 而不是, you’ll be sending the signal elsewhere for encoding, 要么在云中通过实时云转码，要么在远程设施中使用一组可以产生多个Flash和HLS流的硬件编码器. Second, your primary interest is streaming, not broadcast. 因此，我们的目标是向编码设备提供可靠的4-8Mbps 1080p流, not a broadcast-quality signal.

如果你在两三年前要求大型活动主办方选择一种传输技术, fiber and satellite would 就像ly have been first and second on most lists. 今天, 然而, the availability of live cloud transcoding, the maturation of internet connectivity at hotel and conference centers, 以及增强IP传输的工具的可用性，这些因素共同将光纤和卫星推到了许多生产商的后面.

例如，马克·伊斯特， iStreamPlanet的 executive director of live event operations, 他说，当iStreamPlanet推出了它的IP传输时，他对许多现场活动的首选传输方式变成了IP传输 Aventus live video workflow platform, which includes live cloud transcoding. 之前Aventus, 他必须将直播信号路由到公司的广播操作中心之一，将流编码为大多数客户所需的多种格式和变体. 虽然昂贵的, 这就是卫星和光纤所要实现的高带宽路由.

现在，如果他能以3-5Mbps的速度向Aventus服务器传送一个高质量的数据流 (图1)伊斯特说，他可以以很少的成本提供同样的观看体验. If your workflow involves live cloud transcoding, say with the Wowza代码转换器 or a service provider 就像 Brightcove, YouTube生活, 或Aventus, you should explore IP transport techniques first.

会有以太网吗??

而从酒店或会议中心采购带宽过去是有问题的, 一切都变了.

“这些互联网服务现在大多由第三方服务提供商管理，他们多年前就解决了这些问题,伊斯特说. “我们已经有一段时间没有恢复来自酒店或会议中心的带宽问题了.“然而, East强烈建议获得专用带宽，而不是通过共享连接进行广播.

对于高调的活动, East建议酒店或会议中心的代表在现场或随叫随到，以迅速解决任何问题. He also recommends producing two outgoing streams for redundancy, each pointed to a different CDN data center. 这种方式, if a hop between you and one CDN data center goes down, or if the data center itself goes offline, CDN的后端可以自动切换到备份流，节目将继续进行.

当然, for true outbound bandwidth redundancy, your backup signal needs to use a different medium than your primary. 在这种情况下, you might consider using a 4G cellular multiplexing, 或cellmux, 设备, 讨论了下. 当你的广播点不提供以太网但有4G/LTE连接时，这也是你最便宜的选择.

4 g LTE Cellmuxers /

蜂窝复用设备的典型场景可能是来自公司场外活动的广播, 或者在没有以太网但附近有一个或多个蜂窝信号塔的体育赛事中. While you can use a single 4G modem with most on-camera encoders, this enables a single connection only, 没有冗余, which is why cellmuxes are preferred.

顾名思义, cellmux可以使用多个调制解调器，通过多个3G和4G服务连接，以提供更高的带宽和内置冗余. For instance, if you’re in a Verizon dead zone, ATT might have a signal. 如果Sprint的线路被其他交通堵塞，也许T-Mobile会来拯救它. 一些设备, 比如LiveU LU70, can deploy up to 14 cellular modems, 而Teradek和LiveGear等公司较便宜的型号使用6个或更少, which should be more than enough for a 3-5Mbps stream. When other signals are available, some units can also integrate Wi-Fi, WiMAX, 以太网, 或者甚至将卫星连接加入其中，以增强吞吐量和信号冗余.

Most cellmux units either incorporate an H.264编码器或与提供这些编码功能的姊妹产品一起工作. 您可以将相机或混频器的HD-SDI输出插入单元(或组合单元)。, 哪个对视频进行编码, 将数据分成若干块，通过不同的连接进行分发，并将这些块发送出去 (图2).

在另一端，这些块需要重新组装成一个内聚流. If you’re transcoding in the cloud, most cellmux providers offer a cloud-based service or server, 就像 Teradek的 Sputnik, that can de-mux the stream and send it to your server. If you’re using a standalone hardware encoder, cellmux providers typically offer decoder hardware, such as the LiveGear LGR-1000 receiver, 它可以分解流并输出HD-SDI信号以馈送到编码器.

无论哪种方式, to use cellmux technology, you need to figure out both the encode and decode sides of the equation. So you need to buy the cellmux and any required modems, sign up with the various cellular providers, and figure out what you need on the back end to decode the stream. 偶尔使用, 您最好从制造商或第三方服务提供商处租用整个软件包.

超越简单H.264编码, 这些蜂窝复用系统提供了先进的技术，如自适应比特率编码, which matches the bitrate to the available bandwidth, and forward error correction to minimize error in the signal. 一项具有竞争力和互补性的技术正在获得广泛接受，那就是紫溪, which provides an enhanced quality of service layer over the H.264 stream to reduce latency, jitter, and packet loss. 你可以用 紫溪 解决通过基于ip的技术将视频传输到云端的第一英里问题, or deploy it throughout the entire encoding and delivery workflow. While it might not be appropriate for a one-off event, it should be on your radar screen for more regular events.

见到紫溪

实现“子溪”包括三个组成部分:“子溪馈线”、“子溪广播”和“子溪接收”. 紫溪喂料器包装H.264 encoded stream in the 紫溪 format and delivers it to 广播公司. Feeder既可以作为在计算机上运行的独立程序，也可以作为其他公司编码器的功能. 广播公司, which can run on premises or in the cloud, 可以将流推送到流服务器或将传入流转码到多个HLS, HDS, or DASH streams for delivery to your CDN.

就像给料机, Receiver can run as a component of a decoder product, Ateme和Teradek在他们的几个产品中都提供了Receiver, or on a separate computer with the appropriate output card. 接收方的工作是打开子溪传输层并将其传送到解码卡, 例如HD-SDI输出, 或作为独立的MPEG传输流，用于转码或其他部署.

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