The BBC hopes a new low latency trial on its iPlayer platform will improve the quality and reliability of live streamed content, potentially transforming the live event viewing experience for sports fans.
Latency, which refers to the time it takes for data to be transmitted across the internet, has been one of the major weaknesses of digital distribution.
This is especially true with regards to live sport, which is one the most latency-sensitive forms of content given even only a slight delay could lead to an event being ruined by a smartphone notification.
The BBC’s research and development team has been working to reduce the degree of latency to a level at least comparable to that of traditional broadcasting. In recent years, the latency experienced by iPlayer viewers has been reduced to just 40 seconds. However, this is still much higher than the eight to ten seconds incurred by linear transmission.
This latest trial will allow users to opt-in to receive a low latency feed of BBC Two, powered by ‘Low Latency Dynamic Adaptive Streaming’ over HTTP (DASH) and common media application format (CMAF) technologies which split live streams into multiple segments. This means end user devices, such as mobile phones and connected televisions, can process the signal as soon as they receive some of these segments rather than having to wait until they receive the data in its entirety.
By reducing the amount of time required to process a live feed, latency should be significantly reduced.
This BBC trial will be limited to a select number of devices, such as certain generations of Amazon Fire Sticks and some Samsung televisions, with the feed available between 9am and 5pm in England and Scotland.
The BBC will collect performance data from end users to see how the low latency feed performs in real life situations so researchers can understand how viewers would actually benefit and respond to a low latency feed. Meanwhile, they would also be able to see how the feed behaves when transmitted over a real world connection away from lab conditions.
‘With low latency streaming, we also have to think about what should happen if users do experience some rebuffering,’ the researchers said in a blog post.‘Should the stream just resume, leaving them further behind for the rest of the programme? Should the stream catch up, skipping a few seconds in the process?
‘Neither is ideal. Instead, our trial stream will play slightly faster after a stall, aiming to maintain low latency but without the viewer missing any of the action. Doing this without the viewer being aware requires some functionality that is not available on all TVs. To get the best quality data on the reliability we can achieve at delays comparable to broadcast, we are starting our trial using only devices that support this variable speed playback capability and will maintain the target latency we have set.’
Eventually, the BBC will move on to testing different variants of the low latency stream to maximise reliability and expand the trial to more devices. However, the researchers have warned that there is still much work to be done before latency is reduced to near-linear levels.
‘This trial is only our first step in trialling low latency streaming to the public: viewers should not expect that all live internet viewing will match the delays on broadcast at the end of the trial,’ added the researchers. ‘Gradual improvements are more likely. This trial is aiming to assess the reliability of the delivery of low latency media over the internet. More work is needed to build a fully resilient, fault tolerant system that can scale to the size of audience that the BBC serves for major sporting events. Since common ways to build in resilience to failure themselves add delay, achieving this for low latency streams remains a challenge.’
SportsPro says…
Streaming platforms have delivered unprecedented choice and flexibility, with fans able to watch virtually any sporting event in any location on the planet with access to Wi-Fi or mobile connectivity.
But streaming presents its own challenges. Sport is extremely latency-sensitive, with viewers not too keen on delayed feeds that can be spoiled by app notifications, trigger-happy texts from friends, or screaming neighbours next door. This is an issue that is being improved by technological advances, especially 5G, but exacerbated by higher picture quality such as 4K HDR.
As broadcasters add more real time capabilities and integrated betting features into their live feeds, the challenge of latency becomes more pronounced.
While digital distribution is undoubtedly the future, it is experiments like this by the BBC that will ensure streaming no longer has any disadvantage compared to traditional broadcasting.
By SportsPro
