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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 signifi cant challenge. Limelight Multi-Media Delivery Live (MMD Live) gives you a choice of latency reduction options— including ongoing support for Flash, small chunk streaming for HLS/DASH, and soon WebRTC—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 videos 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 fi ve 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.


Increasing the complexity, latency needs to be minimized across all devices on which the live streaming video will be viewed. These include more types of devices than ever:


  • ■ Smart TV with streaming devices such as Google Chromecast, Amazon Fire TV, Apple TV, Roku, and set-top boxes
  • ■ Mobile devices such as smartphones and tablets
  • ■ Laptops
  • ■ Game consoles


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 diff erence 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.

Law enforcement

Swat teams often stream video of ongoing crisis operations to their fellow officers. As they raid a drug house, these teams need instant information. They can’t rely on one-minute old video when they’re planning to break down the door and need to know what’s on the other side.

Remote security surveillance

Corporations often use security cameras to monitor multiple sites on their campus. If cameras detect an employee being mugged in a stairwell, the company can’t afford any delays due to latency in sending help.

Monitoring drones

Many organizations are starting to use drones to monitor their operations. For example, oil and gas companies fly drones equipped with cameras and sensors to detect if there are any problems with their pipelines. Piloting drones remotely requires realtime low latency video from the drone.

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 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 player 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 declined steadily. 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 offers the only solution 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.


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


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 and the default HLS/DASH chunk size is 10 seconds with three chunks created before delivery begins. Overall total delivery latency exceeds 45 seconds when CDN ingesting, transcoding, distance between source and viewer, and delivery are factored in. An obvious way to reduce latency then is to reduce the chunk size. That’s exactly what Limelight has done. To provide deployment flexibility, Limelight off ers two small chunk size solutions.


Many organizations rely on Limelight to handle transcoding for them. Our transcoding service ingests RTMP live streams, transcodes them to HLS/DASH with one second size chunks and delivers them over the Limelight CDN to users with total latency of around six seconds.



These chunk size reductions reduce latency, regardless of whether video is delivered to tablets, phones desktops or other devices, since most modern devices have the processing power and memory to handle low chunk size streaming.


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 connection quality, 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 zipped across the network in milliseconds. This capability reduces the live streaming latency down to about three seconds, a significant improvement over existing HLS/DASH live streaming delivery solutions.


For use cases requiring the lowest latency, WebRTC offers near real-time, sub-second latency. Limelight is in the forefront of WebRTC delivery proof-of-concept testing in production environments.


Released in May of 2011, WebRTC 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 is deploying 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 has high latency because the protocol is chatty – it requires considerable back and forth round trip acknowledgements of packets. If any packet is dropped, HTTP retransmits it. WebRTC can have much lower latency because it runs over User Datagram Protocol (UDP). The UDP protocol does not use acknowledgements back and forth. It creates a point-to-point connection with the client so the video can stream continuously with little communications overhead.


One potential downside is that the lack of acknowledgements and retransmissions means UDP has the potential for unreliable transmissions. MMD Live addresses this issue by supporting the Adaptive Bit Rate (ABR) built into the WebRTC protocol. The ABR automatically reduces the bit rate if it discovers that packets are not transmitting properly. The WebRTC player (e.g. the Web browser) switches to the right bitrate based on the measured bandwidth.


Another advantage of WebRTC is that while other low latency schemes require considerable work on the client side, WebRTC enables playback and delivery to the broadest set of end users. Native browser support means WebRTC can handle the video playback 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.


WebRTC also features a bidirectional data channel. That channel will enable a lot of interesting apps to appear over the next few years that can interact with viewers watching a real-time stream. Examples include live online auctions, online casino gambling, and online games. However, the initial productization of WebRTC will focus on video delivery. Apps that leverage the data channel will come later on.


Whether you rely on Flash, HLS/DASH, or WebRTC, MMD Live delivers live online streaming video to consumers over the Limelight CDN to provide low-latency delivery with a high degree of reliability. Our CDN’s scalability means we can even deliver low latency in the face of large bursts of demand.


Unlike most CDNs, Limelight connects its more than 80 points-of-presence (PoPs) using a high-capacity private fiber backbone that allows it to bypass the unreliable public internet when delivering content to each PoP. 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 called EdgePrism reduces rebuffering and latency and increases throughput speed.


What happens if my firewall blocks UDP?

Some enterprise firewalls are confi gured to block UDP. 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’s Traversal Using Relays around NAT (TURN) server to establish a connection when one or both sides are incapable of a direct P2P connection.

The TURN server is also a building block for supporting interactive, real-time communication using audio, video, collaboration, games and so on between two peer web browsers using WebRTC. Enterprise firewalls are often configured to permit UDP/TCP traffic to well-known TURN servers to allow WebRTC media streams and data channels. Most ISPs will allow traffic from Limelight’s TURN servers.


With MMD Live, Limelight is off ering 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 WebRTC real time low latency.



  • ■ 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: