Why it’s so hard to fix lag on Euro 2020 live streams

Two sets of fans remember England’s clash with Sweden in the 2018 World Cup with particular venom. Swedish fans, who lost, and England fans watching on BBC iPlayer, where the stream went down with three minutes to go.
These fans, who took to Twitter to demand financial compensation, weren’t the only victims of technical mishaps at the last World Cup. Latency – the amount of time between a video frame being recorded and it being shown on TV – was another bugbear. The latency of an online stream can be much bigger than that of traditional broadcast TV. We all feared an errant WhatsApp message or telling cheer ruining the surprise of a goal.
A large portion of the UK will be concerned about a repeat of this outage when England take on Scotland on Friday. But fear not! ITV and the BBC have been hard at work these last three years, preparing for this moment: you may not notice it, but we are watching a far more stable stream than three years ago. “Certainly that’s been our main focus,” says Henry Webster, head of media services for BBC digital distribution. “What we did see at that time were some particular challenges that we weren’t very well set up to face. And we have done a significant amount of work between now and then to get us into a much better place.”

It’s not surprising that streams aren’t yet up to scratch with live broadcast: from a broadcast technology perspective, they’re competing with more than 60 years of development. “Broadly, the challenge is that you are making a kind of one to one connection with all of the audience, and you need to scale appropriately to manage that,” Webster says. “So broadcasting, traditionally, has been either sticks on hills or satellites in the sky, which cast a single signal to a large number of people, and is a very efficient mechanism for sending information out to lots of people at the same time.”
Streams, on the other hand, reach you in a different way, and there’s a lot more things that can go wrong. “A lot of it has to do with the way that video was packaged up and sent down the internet: it’s sent in chunks of six and 12 seconds,” says Steve Forde, ITV’s director of digital products. “And the higher the quality of that video, the more the latency really, because obviously, you’ve got bigger packages of data to send down down the internet.”

In order to reach that holy grail of parity with traditional broadcast TV, companies are shooting for what Forde calls “ideal streams”, a series of factors that make up a quality viewing experience. For instance, start time – how long does it take somebody to get from pressing play to the first video frame? How much buffering is there? How long does it take to transition between the ads and the show?

Finally, and most importantly, they must eliminate dreaded “fatal errors”: people dropping out, as happened on the BBC stream of Sweden versus England. Factors like these are analysed in the months and years between tournaments and big events and tweaked live in the moment. “When the stream is on, we make changes on the fly,” says Forde. “There are so many eyes on the screen it’s a bit like Star Trek Enterprise.”
The scale of streaming is also skyrocketing: audiences are getting bigger and bigger, while expecting streams to get more and more reliable. About 3.9 million people streamed the very first England group game against Croatia on Sunday live on BBC, a new record. If England get further in the tournament, this record is likely to be broken again and again. “What we know is that every year is bigger than the last in terms of the number of people coming to watch,” Webster says. “And so our primary focus is very much on making sure that we can support that new audience scale at any given time.”

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