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While online streaming video once meant video-on-demand, today’s organizations and their audiences are increasingly leveraging the excitement and engagement of live video in multiple ways. Yet, as organizations seek to adopt live video for time-critical use cases, latency has emerged as a significant challenge. Limelight gives you a choice of latency reduction options—including ongoing support for Flash, small chunk streaming for HLS/DASH, and a soon to be released WebRTC-based realtime streaming solution—allowing you to choose the solution that makes the most sense for your use case.


Online streaming video is a force to be reckoned with. From 2016 to 2017, the number of users watching more than 10 hours of online video per week increased from 9.8 to 17 percent. Over the same period, those watching only one to two hours of video per week fell from 49 to 29.1 percent, according to the Limelight “State of Online Video 2017” report.1


While streaming video was once relegated to video-on-demand, live online streaming video is gaining traction. According to a survey by Brandlive,2 44 percent of businesses have already attempted live video streaming in the past 12 months and 20 percent are planning to get into the action in the months ahead.


The incentive is clear: The vast majority (80 percent) of audiences3 prefer to watch live video from a brand than read a blog post while more than one in five Facebook videos is live. These videos are watched three times longer than on-demand videos. Watching live online video, viewers are more likely to feel excitement, immediacy and connection as they stay informed on the latest news and events.


Many live online streaming video services deliver viewing experiences over the internet (via Over the Top (OTT) streaming services) that are nearly as good and predictable as those from traditional TV broadcasters. But a big frustration with online viewing for some use cases is that live video streams typically delay delivery by 40 seconds or more compared to TV broadcasts. This delay is called “latency.”


Latency is the time between when the camera captures the video until it is played back on another device. For internet streaming applications, latency is added by all the components in the streaming workflow: the camera/encoder, upstream network, streaming server, downstream network, and video player on the viewer side.


Latency is not a problem for every online live streaming application. Think about the last live concert you watched on TV. Would it have really made a difference if there was a one-minute delay? On the other hand, the following are examples of use cases where timing is critical—even a matter of life and death.


  • ■ Sports and news—When you’re watching a live online stream of a sports event on your smartphone, the last thing you want is to get a chat from a friend watching the same event on TV saying, “What a great play!!!” before you’ve seen it on your mobile device.
  • ■ Online gaming—When you’re playing online poker and cards are dealt, a one-minute delay means that the dealer must wait to deal the next round until all players see their cards. High latency reduces the number of rounds, which in turn cuts the house’s revenues from the game.
  • ■ Live auctions—Some live auctions now stream live to online bidders. Online auction attendees can bid on items via a two-way channel. To make bids in a timely manner, the online video must be delivered to bidders in realtime.


Limelight offers a number of latency-reduction capabilities, including Flash, small-chunk streaming for HLS/DASH and soon, a realtime streaming solution.. You can pick the one that best suits your use case.


Limelight Multi-Device Media Delivery Live (MMD Live) is designed to take the headaches and hassles out of delivering live online streaming video to a variety of devices, including smart TVs, desktops, mobile screens and set-top boxes. It comes complete with a number of capabilities specifically to minimize latency. MMD Live functions include:


  • ■ Ingesting RTMP (Real Time Messaging Protocol) directly from encoders
  • ■ Cloud-based transcoding and transmuxing a single RTMP ingest stream into other bitrates and formats, such as the popular HTTP chunked streaming formats HLS and DASH, as well as Flash.
  • ■ Video delivery and security


For more than 20 years, the predominant real-time video streaming format has been Adobe Flash which uses RTMP to provide two-to-six second latency.

Flash has long had significant disadvantages. Issues have included enormous security risks, lack of support from Apple and iOS, constant updates that make Flash painful to use, and lack of support in browsers. Unsurprisingly then, the number of users has steadily declined. Adobe recently announced that it plans to stop improving and distributing its Flash player by the end of 2020. Customers will have to find an alternative method for delivering low latency streaming video.

The challenge for customers is that it takes considerable time and effort to transition to a new video delivery protocol. Limelight is committed to allowing these customers to transition to newer technologies. Limelight is one of only a few solutions currently on the market that will continue to support Flash in addition to other protocols to enable the smoothest transition possible to newer technologies on their own schedule.


As mentioned previously, HLS and DASH are the dominant and most widely supported formats for delivering video over the Web. HLS & DASH work by steaming chunks of video, with a default 10 second chunk size and three chunks created before playback begins. Overall total playback latency typically exceeds 45 seconds when CDN ingesting, transcoding, distance between source and viewer, and delivery are factored in. An obvious way to reduce latency is to reduce the chunk size. That’s exactly what Limelight has done. To provide deployment flexibility, Limelight offers two small chunk size solutions.


Many organizations rely on Limelight to handle stream transcoding. Our transcoding service can ingest RTMP live streams and transcode them to HLS/DASH with one second size chunks and deliver them over the Limelight CDN to users with total latency as low as six seconds.



  • Live Cloud Transcoding
  • ■ CDN does transcoding
  • ■ Chunk size can be reduced from standard 10 seconds, to as small as 1 second
  • ■ This reduces video transmit start time to as low as 3 seconds
  • ■ Results in as low as 6 seconds ingest to egress latency


These chunk size reductions reduce latency, regardless of whether video is delivered to tablets, phones, desktops, or other devices.



One note of caution:

The lowest optimal chunk size for your particular use case will depend on your audience’s internet connection. If you have a broad base of users in areas with poor last-mile connections, it may not be possible to reduce chuck size to one second because of the potentially high rate of packet loss. It’s important to have a way to measure your end user’s experience so you can experiment with different chunk sizes. A good tool to monitor video quality is YouBora from Nice People At Work.




Limelight’s Video Acceleration solution is for organizations that prefer to do their own transcoding and use the Limelight CDN to deliver their live online video streaming content to their end users.



  • Live Stream Delivery
  • ■ Content owner does transcoding/packaging
  • ■ Chunk size: as low as 1 second
  • ■ Results in as low as 4 seconds latency depending on ingest chunk size
  • ■ Available today


Video Acceleration is a configuration option in the Limelight Content Delivery Service that is designed to accelerate the delivery of very small video chunks and dynamic manifest files. In this case, small chunk size HLS or DASH is ingested into the CDN and moved across the Limelight network in milliseconds. This capability reduces the live streaming latency to as low as three seconds, a significant improvement over existing HLS/DASH live streaming delivery solutions.


Limelight's realtime streaming solution, which uses WebRTC technology, offers near real-time, sub-second latency for use cases requiring the lowest latency. Limelight is at the forefront of implementing WebRTC technology.

Released in May of 2011, WebRTC (Web Real Time Communication) is an open standard for embedding secure, SSL-protected real-time voice, video and data communication capabilities into a broad range of web browsers and mobile applications. It leverages the real time communications protocol (RTC) created by Google. While WebRTC was originally intended for peer-to-peer communication, Limelight isdeploying it as a unidirectional video channel connection to end user viewers to deliver low latency live video streams.



  • New Option
  • ■ Is not chunked streaming
  • ■ Uses UDP/IP protocol for transport
  • ■ Latency as low as sub-second
  • ■ Broad browser support – no plugin needed
  • ■ Supports adaptive bitrate streaming to adjust to network conditions
  • ■ Availability 2H 2018


HTTP chunk streaming for HLS/DASH utilizes the TCP/IP protocol. The high latency is due to the buffering of chunks prior to transmission. Limelight realtime streaming will run over User Datagram Protocol (UDP). The sub-second latency it provides is because video is not transmitted in chunks.


Another advantage is that while other low latency schemes require considerable work on the client side, Limelight enables playback and delivery to the broadest set of end users. Native browser support means video playback can happen without the need for plug-ins or special players. Currently supported PC and mobile device browsers are Google Chrome, Mozilla Firefox, Safari, Microsoft Edge, and Microsoft Internet Explorer.


Limelight realtime streaming also features the ability to share bidirectional data. This sharing of integrated data along with video allows Limelight customers to develop their own creative ways to use data as part of their video workflows. For example, online auctions can be streamed along with the ability for viewers to bid on items by hitting a button. Gamers can have an integrated chat channel with their video. Viewers watching live sporting events can receive statistics about their favorite players and even vote on their favorite plays in real time. These integrated data capabilities open many new business opportunities.


Limelight provides the scalability to ensure your viewers receive the best live experiences. Unlike most CDNs, Limelight has more than 80 points-of-presence (PoPs) connected by a high-capacity private fiber backbone that allows it to bypass the unreliable public internet when delivering content. With complete control over routing from the content source to the user’s ISP, the Limelight CDN eliminates many common bottlenecks in the content delivery process. Our advanced caching proxy server software reduces rebuffering and latency and increases throughput speed.

What happens if my firewall blocks UDP?

Some enterprise firewalls are configured to block UDP traffic. In many cases, this will not be an issue because live online streaming videos are often consumed by residential users rather than enterprises.

But in instances where your enterprise does need to watch live videos and your firewalls block UDP, you can take advantage of Limelight Realtime Streaming’s capability to deliver video via TCP transport when corporate internet firewalls block UDP traffic.


Limelight offers a flexible set of live video delivery options. If you have video assets in Flash format, you can continue to distribute them to your audience during a transition period, with options for HLS and DASH small chunk size low latency streaming, and realtime streaming.



  • ■ Single format RTMP ingest
  • ■ Multi-format outputs
  • ■ Ease transition from Flash delivery
  • ■ Limelight Networks continues to deliver Flash during transition


The real impact of low latency live online streaming will be the new use cases and business models that are enabled that are not possible with broadcast TV, a key advantage being that internet streaming can deliver video streams anywhere in the world.

To find out more about how MMD Live can reduce latency for your online live video delivery application, contact us at: