It’s been a fantastic summer on BBC iPlayer – with amazing sporting moments from Wimbledon, the Netball World Cup, and the FIFA Women’s World Cup, not to mention a record-breaking Glastonbury and great new dramas series like Ten Pound Poms, The Sixth Commandment, and Wolf.
And while we’ve been bringing viewers all these great moments, we’ve also been hard at work making changes to iPlayer under the hood to bring viewers programmes more quickly.
Rapid availability
The first update is that we’ve introduced a bit of technology that ensures programmes are now available to watch on demand on iPlayer much more quickly than they were before.
Anyone who has tried and failed to catch the end of Strictly Come Dancing or Match of the Day so they can restart it knows the frustration of having to wait for them to become available on iPlayer. With the countdown to Strictly officially beginning as the celebs who’ll take to the dancefloor have started to be announced, plus the return of Match of the Day this weekend as the new Premier League season gets underway – fans of these programmes will be pleased to hear they won’t need to wait nearly as long to watch them on demand.
Previously, there was a significant delay before a programme became available after it was broadcast. This was because it takes time for us to process programmes into a high quality on demand video after they’ve been broadcast. The longer the programme, the longer it takes to process – and being long programmes, both Strictly and MOTD could leave viewers waiting for quite a while before being able to watch them on demand.
What we’ve done now is sped this up significantly, by introducing what we’ve called ‘pseudo VOD’. Rather than processing the whole programme once it’s finished, this pseudo VOD system reuses the live segments of video you see when you’re watching live on iPlayer to create a temporary on demand video instead, which we can publish as soon as the programme ends. This plugs the gap, while we work on processing the high quality on demand video as we did before, and once this is ready replace the temporary video.
Reducing latency
The second update is that we’ve made changes that have reduced the streaming latency of live programmes on iPlayer.
Previously viewers watching live streams may have found they were lagging about 80 – 120 seconds behind the TV broadcast. This is what we refer to as ‘latency’ – and this lag is built in to all live-streamed video on all streamers, to ensure viewers aren’t interrupted when they’re watching a live stream. Now, thanks to some upgrades we’ve made, we’ve been able to reduce this lag by 20 seconds, meaning viewers will now typically only be around 60 seconds behind the TV broadcast.
We’ve done this by modernising the systems we use to process live video. When we prepare video for live streaming, that media is separated into segments of a few seconds each, which make it easier and faster to distribute. However, preparing those separate segments takes time, and the time it takes can vary. That’s why we have latency in the first place, we build in a worst case amount of time so we can be confident the segment of media will definitely have been prepared properly by the time the live stream needs it.
The technology we previously used to do this took quite a long time to prepare each segment, and that time was quite variable. That meant we had to give the latency quite a bit of padding to allow for the worst case preparation time, otherwise a segment not ready on time could interrupt the viewing experience.
What we’ve done now is replace these systems with newer ones, which take a shorter and more predictable amount of time to prepare each segment. That means we’ve been able to reduce the latency, while remaining confident viewers will still get a reliable, stable, uninterrupted viewing experience.
This reliability of viewing experience has always been and remains our top priority, and is what has previously held us back from cutting latency. However, while keeping reliability as the top priority, there are still improvements we can make to reduce this 60 second lag even further.
In the coming months we’ll be looking at further improvements we can make to our existing infrastructure, as well as working with our colleagues at BBC R&D on implementing additional improvements have the potential to bring streaming latency much closer to that of TV broadcast.
All of which means you no longer need to worry if you miss the end of a show, as you’ll be able to watch it on iPlayer within a matter of minutes of it ending. And if you do manage to catch it live – you’ll be seeing it much closer to real-time than you were before.