Home Analysis High dynamic range re-emerges as UHD battleground, as DVB demos HD-plus-HDR profile...

High dynamic range re-emerges as UHD battleground, as DVB demos HD-plus-HDR profile for DTT

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Ten months is a long time in the TV standardisation business. Last November, the DVB was hoping it had nailed the UHD standardisation problem and neatly side-stepped a format war by including within its UHD-1 Phase 2 norm two rival systems for High Dynamic Range (HDR) – namely Hybrid Log Gamma (HLG) and the ten-bit variant of Perceptual Quantizer (PQ-10).

This year, at IBC2017, DVB Chairman Peter MacAvock was lamenting the fact that “what we’re seeing now is those battles being played out all over again.”

HDR is the technology that brings extra ‘sparkle’ to UHD TV pictures both through higher contrast and its associated wider colour gamut, and it’s now considered to be as important as 4K resolution, if not more, to future consumer adoption of ultra-high definition television.

PQ, developed by Dolby as part of its Dolby Vision standard, is favoured by the Hollywood studios and OTT providers such as Netflix. However, it is not backwards-compatible with existing receivers which use Standard Dynamic Range (SDR). HLG, meanwhile, which was created by the BBC in collaboration with Japanese broadcaster NHK, was specifically designed to be backwards-compatible with SDR sets and to favour live production workflows.

The DVB position last autumn was that industry players were free to use either approach, depending on their requirements. This would cause few interoperability issues, it was thought, because it was straightforward to transcode from one to the other, and manufacturers were creating 4K panels with both options included.

However, not all DVB members were happy with that compromise, admits MacAvock. “Some of our members have stipulated that they would like to have mechanisms that are more sophisticated,” he says. Enter four new HDR variants from Dolby, Philips, Qualcomm and Samsung, which unlike the previous two are ‘dynamic’ rather than ‘static’ – that is, they support metadata that changes scene-by-scene rather than metadata that is constant throughout the entire film or video.

“There are some industry observers who suggest that the perceptible difference for the average consumer between these dynamic metadata systems and the static metadata systems like PQ-10 and HLG-10, are very limited,” notes MacAvock. “[But] there are others who say, ‘Oh, no, no. It’s really important.”

This isn’t necessarily because the proponents of dynamic metadata believe it will make any difference to consumers, claims MacAvock: “The idea is, ‘this is the way the editor would like it’ – even if the consumer can’t see it.”

His personal view is accordingly that the industry should “concentrate on getting stuff out into the marketplace and making HDR a success commercially, by providing coherent and consistent messaging to those who would implement it. […] To my mind, the standards discussion, at least this phase, is over. Let’s move on.”

In the meantime, DVB is responding by “looking at whether there’s a commercial requirement for extending beyond those static metadata systems and specifying some form of dynamic metadata system. That work is still ongoing [and] it’ll be ongoing for at least another year. I don’t know that we’ll actually end up specifying another system or not. We may say, ‘no, it’s just not worth it,’ because the market doesn’t absolutely need it.”

One HDR-related profile that the market may require more urgently is the marriage of HDR with HD – as opposed to 4K – resolution. DVB played down the possibility a year ago, but this year the combination provided one of the main demonstrations on DVB’s IBC stand.

MacAvock explains that last year, the sector equated UHD with increased spatial resolution – although “some people, including my own organisation, argued that it wasn’t just spatial resolution, it was a combination of the three features [of HDR, High Frame Rate (HFR) and Wide Colour Gamut (WCG), as well].”

Now, he says, there’s emerged a realisation that, “in fact, HDR is the unique selling point for this enhanced experience, whether you call it UHD or not.” In this connection, “there is a sweet spot for 1080p50 with HDR over terrestrial channels. Terrestrial channels have all the advantages of accessibility, but they don’t have the advantage of having extensive bit-rate. In that sphere, 1080 P50 with HDR looks pretty damn good,” he declares, “particularly with HFR. Being able to see that tennis ball is revolutionary.”

The HD-plus-HDR profile works well in part because an increasing number of 4K TV sets are able to upscale HD signals to UHD very effectively, MacAvock points out. “Particularly on a 55-inch [4K] set, if you put that in front of a substantial proportion of the public, I would argue they won’t know the difference,” he says.

“This enhances the DTT platform to the extent where it can now compete with other similar platforms that maybe have a dearth of bandwidth – so we can address the deficiencies of the DTT platform in that regard,” he concludes.

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