HDR brings new dynamics to content production and consumption

Whether broadcasters and content producers are working in 4K/Ultra HD or HD, it would appear that HDR is playing an increasingly key role in bringing the most immersive viewing experience to the home.

While more and more viewers — even those of the sports persuasion — are embracing the concept of consuming their favourite content streamed over the Internet, it does not necessarily mean that they are willing to make major concessions when it comes to picture quality.

This possibly goes some way to explaining why even traditional broadcasters are stepping up efforts to bring the best viewing experience to their audiences, beyond the TV screen. The BBC, for instance, streamed selected matches of the 2018 FIFA World Cup live in 4K/Ultra HD (UHD) and high dynamic range (HDR) to UK-based audiences over the BBC iPlayer.

That, perhaps, remains the high point of a journey that began in 2014, when the BBC started to investigate how HDR could fit into its broadcast infrastructure. The British public broadcaster came to the conclusion that any approach could not rely on end-to-end metadata, as metadata often gets lost or becomes out-of-sync with the content as it passes through the production chain.

The BBC also wanted the captured signal to be display-independent because a wide range of different displays and lighting conditions are used both in production environments and in the home. Finally, the BBC wanted an approach that was compatible with its current 10-bit infrastructure, and only required changes to the cameras and critical monitoring displays. This led the BBC and Japanese public broadcaster NHK to invent the Hybrid Log-Gamma (HLG) system for HDR, which is included in ITU-R BT.2100, the international standard for HDR programme production and exchange.

Designed to be a scene-referred system, the HLG signal represents relative light levels in the original scene, which allows pictures from a single mastering process or live production to be adapted to give the same artistic effect on its own capabilities an environment to faithfully render the scene-referred signal, so metadata that describes the mastering display is not required. HLG also has native compatibility with standard dynamic range (SDR) TV within the same colour format, which can be used for 4K/UHD SDR displays.

Full story is available in the September 2018 of APB.

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