With the explosive growth of subscription VOD services, OTT streaming has already become mainstage for on-demand content. The new OTT frontier is now for live or linear streaming. Delivering low latency streams may be a key ingredient to bring live OTT streaming to the mainstage.
Where we are with OTT streaming and latency
Adaptive Bitrate technologies represented the critical ingredient that enabled the OTT streaming revolution a decade ago. Previous approaches such as RTMP couldn’t scale and take advantage of the Internet’s architecture with caches and CDNs designed for data packets. The technology initially fooled the Internet into treating video streams just like any other data. However, in fixing the scalability challenge, ABR introduced stream delay as the content is buffered to cater to the Internet’s varying capabilities. The technology is evolving and new enough sometimes still to be “bleeding-edge”. OTT video streaming gained sufficient reliability to carry commercial services such as Netflix, but the latency issue it introduced is still problematic today. In this blog, I’ll take a look at how and where that is an issue.
The streaming industry has agreed on the term Low Latency, and there are many new ultra-low-latency or ULL offerings. In this context, latency is the time between real-time action for live video and the video displaying on the subscriber’s screen.
The characteristics of OTT live streaming are only relevant in comparison to broadcast and have delays of only around 5 seconds. You can see this delay when watching a live event on broadcast TV. Or, when listening to the commentary on an analog radio. Is it safe to say that since we have not heard many complaints about this 5-second delay, then it's a delay that is generally acceptable? Possibly.
What about a 6, 10 or 15-second delay, are they acceptable?
How latency affects the video experience
Let’s first look at how some different types of content may be affected by latency.
- Non-linear content is only impacted by latency in that this could, in some cases, cause initial buffering before a stream starts.
- Re-linearized content is similarly impacted by latency, which can also be akin to channel-change time.
- Live news only suffers from latency when it is significant, i.e., over 30 seconds.
- Interactive shows have traditionally not required low latency like, for example, with the Eurovision song contest that uses telephone, SMS-based voting. However, a new genre of truly interactive shows, where participants interact in real-time based on a stream, will require a latency below two seconds.
- Niche live sports will typically only be streamed on a single platform and, therefore, not broadcast simultaneously on different ones. They are not affected by latency, except perhaps if there is also a social media aspect.
- Mass audience live sports are the premium market that most of us focus on in this debate. But as with niche sports, most events, even a major event like the European Champions League final, will be carried by a single provider in most markets. Potential competition in terms of latency will be between the same operator’s broadcast and OTT streams. Such a difference isn’t an issue within a household as the event will either be on the main screen or second screens, not both.
- The World Cup happens once every four years, is a unique case where latency does become an issue. Indeed, the national team’s matches are, in most cases, carried by a public broadcaster that is itself freely available on all platforms.
- Teleshopping requires Interactivity and responsiveness for the best shopping experiences. See the use illustrated by Shop LC and the Jewelry Channel that have launched a DASH CMAF-based service built on Harmonic’s VOS360 SaaS.
- Betting is a unique use case where low latency is preferable, but the requirement is for a fully controlled and consistent latency.
Inherently real-time video applications like telemedicine, flying a drone, or using a massive screen at a live event are niche applications that require latency in milliseconds, not seconds, and are beyond the scope of this post.
Each use case has different latency requirements
Any operator offering any of the above use cases will eagerly embrace lower delay times for OTT streaming. However, the business case to spend significant money to reduce delay will depend on the use case. The one factor that applies to all use cases, however, is social media. Indeed, posting a tweet from a live event has a similar five-second delay to linear broadcast. That, therefore, becomes a key target for OTT live streaming.
Although there are different technical approaches to reducing stream delay, most newer solutions use CMAF. Explaining these different techniques requires a deep-dive into packaging, chunks, origin servers, video players and CDNs. Commercial products have been available for over a year, and media processing and delivery providers have been making their case through growing marketing efforts. Some operators like the BBC have been vocal about the issue for several years. Still in 2020, operators are learning more about the business growth potential gained from lowering delay.
OTT is still a key business focus
Operators are no longer trying to fight off OTT platforms like Netflix. They are instead embracing them. The boundary between on-demand and linear or live content is blurring. The super-aggregation buzzword is seeing operators around the world work on having a central role to offer access to all types of content. A reduced live streaming delay can become a critical unique selling point (USP).
If you are looking for solutions that help you lower latency and reduce delay, Harmonic can help. We have decades of experience and leadership in the media processing and delivery industry. Contact us to start a discussion about how we can help your business best deliver media content to your subscribers.