Posted by Phil Layton on
The latest from our work on High Dynamic Range and Hybrid Log-Gamma. This article by BBC R&D's Phil Layton first appeared in the September 2016 edition of TVBEurope.
Throughout IBC 2016 there will be more HDR content on display than ever before. Those of you attending will have the opportunity to attend demonstrations such as 'Better Pixels and More' from the EBU and see the pioneering work of organisations around the globe that will bring this technology to audiences.
It doesn't feel that long since I was similarly enthused about HD. Advances in picture quality can be subtle yet profound and when I was working on the BBC's first HD broadcast for the 2006 World Cup I didn't realise quite how impressed I was at first. It was clearly an improvement on my trusty TV at home, but it was only after I'd grown accustomed to it that its importance struck me. When the time came to return the prototype I was working with I knew that watching in standard definition would never be the same. There was no going back for me. I needed an HD TV. The move to HD saw TV sets jump from around 702 pixels wide to 1920 pixels and now many people are looking forward to a similar shift in quality with UHD and a jump to 3840 pixels. Increasing the number of pixels in a set can improve quality for viewers and UHD is a perfect example of this. But we're getting nearer to the resolution limit of the human eye. The original UHD standard acknowledged this and alongside introducing superior colour compared to HD, it left the door open for improvements in the dynamic range of the images.
HDR can take advantage of a TV's capability to show pictures in far higher contrast meaning pictures can give a better impression of sharpness, more natural and brighter highlights, mirror-like reflections and extended detail in shadows and dark parts of the picture. HDR doesn't give you more pixels - it gives you better pixels.
In July the International Telecommunications Union (ITU) took a huge step forward in making this a reality with a new standard for HDR TV known as the ITU-R Recommendation BT.2100. The standard includes two approaches: Dolby's Perceptual Quantization and Hybrid Log-Gamma (HLG) which has been developed by BBC R&D and NHK.
HLG was developed to specifically address the needs of TV broadcasters. It can help take TV quality to the next level, complementing the advances made in TV resolution to deliver the most life-like and atmospheric programmes we've ever seen. The HLG specification makes it relatively straightforward for major TV broadcasters to adopt HDR productions into their existing infrastructure and workflows.
At the BBC we distribute content to a range of devices, through our traditional TV channels and to connected devices through our online services such as BBC iPlayer.
Root and branch changes would add considerable cost and complexity so a new standard needs to be deployed as simply as possible. BBC R&D and NHK's approach helped guard against needless inefficiencies creeping into future HDR production. For example, because HLG uses characteristics similar or closely matched to current television, it ensures future HDR programmes will also be compatible with non-HDR UHD televisions. They are also straightforward to convert for distribution over our existing SD, HD and online networks.
The HDR-TV standard published by the ITU is a major milestone and the inclusion of HLG means we can continue working with the industry to turn the potential of HDR into reality and, ultimately, make TV even more real.
This post is part of the Broadcast and Connected Systems section