Why Brightness is Lighting up the UHD Agenda

IBC

While reports continue to surface about impending launches of UHD broadcast services, the issue of higher dynamic range (HDR) has risen to the top of the industry agenda.

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Broadcasters like Sky Deutschland (now Sky) and the BBC have used IBC in recent years to argue that better pixels, not just more pixels, are required to kick-start UHD in the home. They needed to convince TV set makers not to go to market solely on resolution and earlier this year it seems they had finally done so.

Announced in January the UHD Alliance brings together consumer electronics brands like Samsung with the studios Warner Bros. and Fox as well as Netflix to explore how HDR can be delivered. Colour depth, luminance and colour space are all within its remit. It will address fundamental issues like, 'how bright should bright be?' and for colour gamut, 'how wide should the colour space be?'

“HDR allows us to both raise the ceiling and drop the floor, to the point where dark blacks and grey gradients reveal incredible detail that the consumer has never before been able to see,” says Technicolor, a UHD Alliance member. “Expanding the dynamic range has a side benefit of increasing the available saturation of any particular colour, so even without expanding the colour gamut, HDR can create richer colours. By establishing a minimum level of viable specifications for HDR, we can promise consumers a defined level of quality.”

Collaboration across the ecosystem will ensure the industry can move forward together, however the path is not clear. For a start the UHD Alliance conflicts with the Ultra HD Forum, set up in 2014 by Harmonic to explore an end-to-end ecosystem for delivering UHD services. The publicly expressed aim of both groups is to agree a joint approach by NAB 2015 but their dual existence appears to expose different commercial goals.

While content everywhere vendors would prefer to increment UHD technology each year in order to sell more products, broadcasters would prefer a big bang introduction that justifies charging consumers a premium for a new service.

Futuresource Consulting has even observed that the UHD Alliance can be seen as an attempt to counter Chinese content everywhere vendors by differentiating UHD Alliance-member products from supposedly inferior quality but certainly cheaper competition.

Approaches to HDR are already being played out in standards bodies. A version before SMPTE seems primarily designed for theatrical display, while the BBC and NHK are among several parties tabeling other proposals before the ITU.

Among expressed concerns: how will viewer's eyes adapt to viewing HDR augmented content in a living room (rather than darkened auditoria) and juxtaposed with SDR (traditional HD) content?

A related discussion is how to make content that works for both HDR consumption and SDR consumption since there is an ongoing need to support current TV platforms.

Another issue surrounds HDR metadata which is used to describe the dynamic range alongside the picture asset. “In a production and delivery environment there are too many options for that to get out of sync and cause a bad end-user experience,” says Simon Gauntlett, CTO, Digital TV Group.

Then there is the whole marketing piece. Content Everywhere vendors rightly point to the concept of 4K being more readily understood by consumers familiar with HD 1080P. But HDR?

“HDR is hard to communicate to consumers and it has nothing to do with the technology,” declared Netflix's Scott Mirer at CES. “[the industry] does not have experience with how to talk about HDR’s benefits to consumers and we don’t have convergence on how to implement it.”

According to Technicolor, the challenge for the industry will be to convey the HDR and colour space value at the retail level.

Viewers won't see any benefit in HDR while content is still produced to match the existing Rec. 709 standard. Upscaling technology in TV sets is a workaround, although the results can look unnatural and over saturated. One of the goals of the UHD Alliance is to standardise around Rec. 2020 but until content is produced in that format, a TV's ability to display extra colour gamut will be wasted.

On the production side, HDR impacts right through the chain. Many digital cameras can capture 14+ stops of dynamic range but this tends to get thrown away quite quickly in the capture process. A workflow needs to be found to store and retain the information into the pipeline.

As it stands content may require a separate HDR grade, adding cost to the post process. Professional monitors capable of displaying HDR are few and far between. As with the move from SD to HD there are even implications for how a scene is lit, how special effects are composited and even how makeup is applied on set.

The concerns raised by the broadcaster lobby are being explored within the UHD 1 phase 2 specifications currently working their way through the DVB. Once standardised, new chipsets will be needed to accommodate the change which could be a couple of years away.

None of this is to suggest that broadcasters won't launch a UHD service before 2017. The odds are that they will bow to competitive pressure and launch UHD live sports services first where higher frame rates are more the issue than higher brightness.

According to Technicolor, a single, open specification accepted by both content creators and display developers will eliminate the 'chicken and egg' scenario of content and hardware availability, allowing consumers to experience the full benefit of these new technologies.

However, there are those who argue that the introduction of HDR should be detached from UHD so that it can be applied to HD as well.  Those who have witnessed comparisons of HDR-augmented High Definition versus non-HDR UHD content at shows like IBC leave convinced that HDR is the greater visual bonus.