At the recent SportsPro OTT Summit in Madrid, a poll of the audience was conducted to determine the biggest challenge of OTT service delivery. Latency ranked second, and it is an especially pertinent issue for live sports events.
If you want proof, look no further than the world’s biggest soccer tournament, which took place in Russia in 2018. Hundreds of millions of people around the world watched this year’s event via OTT services, and the delay for video streaming compared to broadcast was quite noticeable, to say the least! Families in the same household, some gathered around the TV screen and others watching on their mobile devices, saw a video delay of about 30 to 90 seconds for OTT. And instant notifications on social media meant soccer fans were finding out about goals before actually seeing them.
Why is this happening?
Classical methods of HTTP transmission (e.g., HLS or DASH) typically cause latency of between 30 and 90 seconds due to sequential buffering of multiple media delivery chunks. Thankfully, the industry has come up with a solution.
What’s the solution?
The MPEG Common Media Application Format (CMAF) standard and its Low Latency Chunk (LLC) option, introduced in July 2017, enables live OTT content to be delivered using micro chunks of about 100ms. Under this approach, all the elements of the food chain exchange data on a micro chunk basis, which makes the delay of an OTT distribution as low as 5 seconds.
Harmonic conducted trials of CMAF during the soccer tournament and measured delays between 5 to 9 seconds depending on the infrastructure, the network and the type of client used. We predict that by 2019, the delay for OTT will be very close to broadcast.
Why is this important?
Sports fans do not want to hear what’s happening during a live event from their neighbors, family members and social network friends. The delay for OTT must be on par with broadcast. For IPTV operators that want to migrate from IP multicast to unicast (ABR), low latency for live sports streaming has to be on equal ground with multicast delay. For pay-TV operators that are using an ABR catch-up mechanism and what to offer a smooth start-over experience, they must align the timing of broadcast and ABR.
Want to learn more? Check out a recent white paper Harmonic recently released explaining the fundamentals of MPEG CMAF low latency and the state of the art of CMAF as of today.
– Thierry Fautier VP Video Strategy at Harmonic and President of the Ultra HD Forum