Video for the Long Haul: Exploring Backhaul Options
You’re streaming a high-profile event in the not-too-distant future, and you’re wondering about your options for transmitting your video to your streaming server or service provider. You’re concerned about quality, reliability, and perhaps redundancy. You’ve read about satellite and fiber, as well as multiple options for efficiently transmitting over IP networks, 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, because these backhaul options are precisely what I’ll be covering in this article.
Let’s start with some assumptions. First, you won’t be encoding the streams you’ll actually distribute onsite. Instead, you’ll be sending the signal elsewhere for encoding, either in the cloud via live cloud transcoding or to a remote facility with a bank of hardware encoders that can produce multiple Flash and HLS streams. Second, your primary interest is streaming, not broadcast. So the goal is delivering a reliable 4-8Mbps 1080p stream to your encoding facility, not a broadcast-quality signal.
If you asked large event producers to choose a transport technology even two or three years ago, fiber and satellite would likely have been first and second on most lists. Today, however, the availability of live cloud transcoding, the maturation of internet connectivity at hotel and conference centers, and the availability of tools that enhance IP transport all come together to push fiber and satellite to the rear for many producers.
For example, Mark East, iStreamPlanet’s executive director of live event operations, says his preferred transport method for many live events changed to IP transport when iStreamPlanet launched its Aventus live video workflow platform, which includes live cloud transcoding. Before Aventus, he would have to route the live signal to one of the company’s broadcast operation centers to encode the stream into the multiple formats and variants necessary for most clients. Though costly, this is the high-bandwidth routing that satellite and fiber are designed to accomplish.
Now, if he can deliver one high quality stream at 3-5Mbps to the Aventus server in the cloud (Figure 1), East says he can produce the same viewer experience at a fraction of the cost. If your workflow involves live cloud transcoding, say with the Wowza Transcoder or a service provider like Brightcove, YouTube Live, or Aventus, you should explore IP transport techniques first.
Figure 1. The live cloud transcoding feature in iStreamPlanet’s Aventus service makes IP delivery the preferred technique.
Will There Be Ethernet?
While sourcing bandwidth from a hotel or conference center used to be problematic, things have changed.
“Most of these internet services are now managed by third-party service providers who worked the kinks out years ago,” East says. “It’s been a while since we had an unrecoverable issue with bandwidth sourced from a hotel or conference center.” However, East strongly recommends obtaining dedicated bandwidth rather than broadcasting via a shared connection.
For high-profile events, East advises having a representative from the hotel or conference center on site or on call to swiftly resolve any issues. He also recommends producing two outgoing streams for redundancy, each pointed to a different CDN data center. That way, if a hop between you and one CDN data center goes down, or if the data center itself goes offline, the CDN’s back-end can automatically switch to the backup stream and the show will go on.
Of course, for true outbound bandwidth redundancy, your backup signal needs to use a different medium than your primary. In this case, you might consider using a 4G cellular multiplexing, or cellmux, device, discussed next. These are also your least expensive options when your broadcast point doesn’t offer Ethernet but does have 4G/LTE connectivity.
A typical scenario for cellmux devices might be a broadcast from a company off-site event, or a sporting event where Ethernet isn’t available but one or more cellular towers are closeby. While you can use a single 4G modem with most on-camera encoders, this enables a single connection only, and no redundancy, which is why cellmuxes are preferred.
As the name suggests, a cellmux can use multiple modems connecting via multiple 3G and 4G services to provide a higher bandwidth and built-in redundancy. For instance, if you’re in a Verizon dead zone, ATT might have a signal. If the Sprint circuits get clogged with other traffic, perhaps it’s T-Mobile to the rescue. Some devices, such as the LiveU LU70, can deploy up to 14 cellular modems, while less expensive models from companies like Teradek and LiveGear use six or fewer, which should be more than enough for a 3-5Mbps stream. When other signals are available, some units can also integrate Wi-Fi, WiMAX, Ethernet, or even satellite connectivity into the mix to enhance both throughput and signal redundancy.
Most cellmux units either incorporate an H.264 encoder or work with a sister product that provides these encoding functions. You plug the HD-SDI output from your camera or mixer into the unit (or combined units), which encodes your video, divides it up into chunks to distribute via the different connections and sends these chunks on their way (Figure 2).
Figure 2. The two sides of the cellmux solution, shown here in LiveU’s configuration.
At the other end, these chunks need to be reassembled into a cohesive stream. If you’re transcoding in the cloud, most cellmux providers offer a cloud-based service or server, like Teradek’s 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, that can demux the stream and output an HD-SDI signal to feed into your encoder.
Either way, 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. For occasional use, you may be better off leasing the entire package from the manufacturer or a third-party service provider.
Beyond simple H.264 encoding, these cellmux systems offer advanced techniques such as adaptive bitrate encoding, which matches the bitrate to the available bandwidth, and forward error correction to minimize error in the signal. One competitive and complementary technology that’s gaining widespread acceptance is Zixi, which provides an enhanced quality of service layer over the H.264 stream to reduce latency, jitter, and packet loss. You can use Zixi to solve the first-mile problem of getting your video into the cloud over IP-based technologies, 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.
Implementing Zixi involves three components: Zixi Feeder, Zixi Broadcaster, and Zixi Receiver. Zixi Feeder wraps the H.264 encoded stream in the Zixi format and delivers it to Broadcaster. Feeder is available as either a standalone program running on a computer or as a feature in other companies’ encoders. Broadcaster, which can run on premises or in the cloud, can push the stream to your streaming server or transcode the incoming stream into multiple HLS, HDS, or DASH streams for delivery to your CDN.
Like Feeder, Receiver can run as a component of a decoder product, with both Ateme and Teradek offering Receiver in several of their products, or on a separate computer with the appropriate output card. Receiver’s job is to unwrap the Zixi transport layer and deliver it either to the decoder card, say for HD-SDI output, or as a standalone MPEG transport stream for transcoding or other deployment.
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