Advanced Television

BBC R&D solves iPlayer World Cup ‘lag’

September 13, 2018

Colin Mann @ IBC

Football fans have reason to cheer – BBC Research & Development (R&D) has managed to solve the problem of delays when people watch live Internet streams rather than a TV broadcast. In a new prototype being demonstrated at the IBC in Amsterdam, the team will show how the gap between an Internet-delivered live stream and live TV via broadcast can be eliminated.

During this summer’s dramatic World Cup, some fans watching on BBC iPlayer experienced a ‘lag’ while watching matches of 30 seconds or more behind the TV broadcast, with some complaining of hearing neighbours cheering goals that they hadn’t seen happen yet.

The problem – latency – affects the vast majority of live video delivered over the Internet. It happens because it takes longer to send video over the Internet reliably than it does to broadcast it. While still just a prototype and unlikely to change live streaming delays any time soon, BBC R&D’s demonstration at IBC will show how innovations can solve the issue, so that, in the future, fans watching over the Internet won’t have to wait to see the action.

Latency occurs because of the way video is distributed over the Internet. Portions of video and audio data are typically delivered over the Internet in separate files. If these files – known as media segments – get too short, processing them becomes very inefficient. If the files are long, you get higher latency, as each segment needs to be generated in full before it can be passed on to the next step in the chain.

Building upon work by standards organisations and others in the industry, the low latency techniques BBC R&D has been experimenting with work by either reducing the duration of each segment, or by creating the segments progressively as a series of chunks that can be passed through the chain immediately as they become available. The result means that, in the future, live streaming viewers watching over the Internet will be able to see the action at the same time as they would see it if they were watching on TV.

“Obviously, viewers were frustrated this summer hearing goals go in before they saw them, or finding out about a red card decisions on social media first,” admitted Chris Poole, lead research engineer for BBC R&D. “That’s why we’re so excited by the results of our experiments, and we’re hoping that the demonstration we’ll be showing at IBC will help accelerate the work taking place across the industry to eliminate long delays from Internet streams.”

“Earlier this year, BBC CTPO Matthew Postgate said that the days when all media will be distributed over the Internet are not too far away. With that in mind, we’re hoping that this work will help to make our Internet-streamed live video as good as it can possibly be.”

“What we’re showing at IBC is a prototype, however. To roll it out properly will take time, and it needs coordination with the whole industry, so viewers shouldn’t expect the lag to disappear imminently. But perhaps by the time they’re watching the next World Cup, viewers will be cheering at the same time, regardless of how they’re watching the match.”

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