Continuing the BBC's experiments in UHD
Head of Broadcast and Connected Systems, BBC R&D
From the introduction of colour TV on BBC Two for Wimbledon in 1966, to championing free-to-air HDTV for terrestrial viewers, we’ve always been working to improve picture quality for audiences.
Lately, our experiments have seen us make select shows available to watch in Ultra-High Definition (UHD) on BBC iPlayer. So far, we’ve focused on providing on-demand programmes in UHD, but now we’re taking the next step by streaming live UHD content.
On Sunday, we streamed a full Rugby League match between the York City Knights and Catalans Dragons live in UHD and High Dynamic Range on BBC iPlayer Beta. It’s the first time we’ve streamed a live event in such high quality.
For those unfamiliar with the terminology, UHD takes advantage of higher resolution TVs to provide exceptional clarity of picture, while HDR takes this further with greater detail in the shadows and dark areas of the picture, as well as more natural and brighter highlights and mirror-like reflections.
Here at the BBC, we use a type of HDR called Hybrid Log-Gamma (HLG), invented by BBC Research & Development and Japanese broadcaster, NHK. Due to the way HLG represents light, audiences get the most natural colours possible on their televisions at home. In our last experiment, which saw the whole series of Blue Planet II on BBC iPlayer in UHD HDR, this meant that the spectacular animals, vibrant coral reefs and deep blue oceans were brought to life like never before.
The BBC chooses to use HLG for BBC iPlayer because it fits very well and reliably into existing live production workflows. It also provides a great picture not only to HDR devices, but to standard dynamic range (SDR) devices that support the BT.2020 wide colour gamut as well. Being able to support both HDR and SDR TVs with the same bitstream is cost-effective for the BBC and makes the content available to as wide a range of devices as possible.
However, making the move from on-demand UHD programmes to live UHD footage presents significant engineering challenges for our teams. High quality real-time HEVC encoding of UHD is still in its infancy, and is much more demanding for live programmes than for on-demand. That means we need to use higher distribution bitrates, and that people’s TVs will need to work harder to show the best picture.
We’re always looking to provide our audiences with the best possible viewing experience, and live UHD could be the next step in that journey. We’re now looking at the results from this latest experiment to help us build our understanding for how we might be able to provide live events in UHD in the future.