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The State of HDR in Broadcast and OTT

By Yoeri Geutskens

A lot has been written about HDR video lately, and from all of this perhaps only one thing becomes clear – that there appear to be various standards to choose from/ What’s going on in this area in terms of technologies and standards?

A handful of organizations have proposed technologies for HDR capture, transmission and reproduction – Dolby, SMPTE, Technicolor, Philips, and BBC together with NHK.

Dolby’s HDR technology is branded as Dolby Vision. One its key elements is the Perceptual Quantizer EOTF which has been standardized as SMPTE ST 2084. Both Dolby Vision and HDR10, the profile mandated by the Blu-ray Disc Association for all new HDR Ultra HD Blu-rays use the same SMPTE 2084 standard making it easy for studios and content producers to master once and deliver to HDR10 or Dolby Vision with Dynamic Metadata added. The dynamic metadata is not an absolute necessity but it guarantees the best results when played back on a Dolby Vision-enabled TVs. HDR10 uses static metadata which ensures it still looks good, well beyond what we have today. Even using no metadata SMPTE 2084 can work at an acceptable level just as other proposed EOTFs without metadata do.

For live broadcast Dolby supports both single and dual-layer 10-bit distribution methods and has come up with a single workflow that can simultaneously deliver an HDR signal to the latest generation and future TVs plus a derived Standard Dynamic Range (SDR) signal to support legacy TVs. Not requiring dual workflows will be very appealing to all involved in content production. Because the SDR distribution signal is derived from the HDR original using Dolby’s content mapping unit (CMU) it is significantly better with more detail and color than one captured natively in SDR, as Dolby demonstrated at IBC 2015.  

Technicolor has developed two HDR technologies. The first takes a 10-bit HDR video signal from a camera and delivers a video signal that is compatible with SDR as well as HDR displays. The extra information that is needed for the HDR rendering is encoded in such a way that it builds on top of the 8-bit SDR signal but SDR devices simply ignore the extra data.

The other is called Intelligent Tone Management and offers a method to ‘upscale’ SDR material to HDR, using the extra dynamic range that current-day cameras can capture but traditional encoding cannot handle, and providing enhanced color grading tools to colorists. The resulting picture quality remains to be seen but this technique could greatly expand the amount of available HDR content.

Having a single signal that delivers SDR to legacy TV sets (HD or UHD) and HDR to new sets is also the objective of a collaboration between BBC R&D and NHK: Hybrid Log Gamma (HLG) is compatible with existing 10-bit production workflows and can be distributed using a single HEVC Main 10 Profile bitstream. On cable and satellite but especially for terrestrial broadcasting bandwidth is scarce, so transmitting the signal in SDR and HDR in parallel is not attractive. For the same reason, most broadcasters are far more interested in adding HDR to 1080p HD channels than in launching UHD channels. Adding HDR is estimated to consume up to 20% extra bandwidth at most – not 300%, like UHD.

The DVB Project meanwhile has recently announced that UHD-I phase 2 will include a profile that adds HDR to 1080p HD video – a move advocated by Ericsson and various broadcasters. Don’t expect CE manufacturers to start producing HDTVs with HDR however. Such innovations are likely to end up only in the UHD TV category. This means consumers will need a HDR UHD TV to watch HD broadcasts with HDR. Owners of such TV sets will be confronted with a mixture of qualities.

The SMPTE is one of the foremost standardization bodies active in developing official standards for the proposed HDR technologies. Another body is the Blu-ray Disc Association (BDA). Few people are blessed with a fast enough broadband connection to be able to handle proper UHD video streaming, with or without HDR. Netflix requires at least 15 Mbps sustained average bitrate for UHD watching but recommends 25 Mbps. The new Ultra HD Blu-ray standard offers up to 128 Mpbs peak bit rate.

The BDA deserves praise for not rushing the new standard to launch without HDR support. The complication, of course, was the lack of a single standard for HDR. The BDA has declared the HDR10 Media Profile mandatory for players and discs with Dolby Vision and Philips’ HDR format optional.

The UHD Alliance mostly revolves around Hollywood movie studios and is focused on content creation and playback, guidelines for CE devices, branding and consumer experience. They may issue specifications for HDR as well, come CES 2016. The Ultra HD Forum meanwhile focuses on the end-to-end content delivery chain including production workflow and distribution infrastructure.

In broadcasting there’s the ATSC in North America (and South Korea) defining how to broadcast UHD and HDR over the air with the upcoming ATSC 3.0 standard and transmitted via cable. Here, the SCTE comes into play also. Japan has the ARIB and for most of the rest of the world including Europe the DVB Project, part of the EBU, specifies how to fit UHD and HDR into the standards for terrestrial, satellite and cable distribution.

ETSI has just launched a new Industry Specification Group (ISG) to look at UHD, HDR and WCG. Founding members include two telcos. BT already operates a UHD IPTV service; Telefónica is about to launch one.

The CTA (Consumer Technology Association, formerly CEA) in the US and DigitalEurope deal with guidelines and certification programs for consumer products. By now, the CTA has also issued guidelines for HDR. DigitalEurope hasn’t yet.

One couldn’t blame a consumer for deciding to postpone the purchase of a new TV until standards for HDR have been nailed. Similarly, for broadcasters and production companies it only seems prudent to postpone making big investments in HDR equipment and workflows.

It’s inevitable we’re going to see a mixture of TV sets with varying capabilities in the market – SDR HDTVs, SDR UHD TVs and HDR UHD TVs – not even taking into consideration near-future extensions like HFR.  Simply ignoring some of these segments would be very unwise: cutting off SDR UHD TVs from a steady flow of UHD content for instance would alienate the early adopters who bought into UHD TValready. The CE industry needs to cherish these consumers. It’s bad enough that Brits who bought a UHD TV in 2014 cannot enjoy BT Sport’s Ultra HD service because their TV set doesn’t support HDCP 2.2 which the set-top box requires.

It is not realistic to cater to each of these segments with separate channels either. Even if the workflows can be combined, no broadcaster wants spend the bandwidth to transmit the same channel in SDR HD and HDR HD, plus potentially SDR UHD and HDR UHD.

Having separate channels for HD and UHD is inevitable but for HDR to succeed it’s crucial that the HDR signal is an extension to the SDR broadcast signal.

Innovations like Ultra HD resolution, High Dynamic Range, Wide Color Gamut and High Frame Rate will not come all at once with a big bang but – apart from HDR and WCG which go together – one at a time, leading to a fragmented installed base. This is why compatibility and ‘graceful degradation’ are so important: it’s impossible to cater to all segments individually.

What is needed now is alignment and clarity in this apparent chaos of SDOs (Standards Defining Organizations). Let’s group them along the value chain:

Domain

Production

Compression

Broadcast

Telecom

Media/ Streaming

CE

SDO

SMPTE, ITU-R

MPEG , VCEG

ATSC, SCTE, EBU/DVB, ARIB, SARFT

ETSI

BDA, DECE (UV)

CTA, DigitalEurope, JEITA

 

Within each segment, the SDOs need to align because having different standards for the same thing is counterproductive. It may be fine to have different standards applied, for instance if broadcasting uses a different HDR format than packaged media; after all, they have differing requirements. Along the chain, HDR standards do not need to be identical but they have to be compatible. Hopefully organizations like the Ultra HD Forum can facilitate and coordinate this between the segments of the chain.

If the industry can figure out what HDR flavor to use in which case and agree on this, the future is looking very bright indeed.

Thanks to various Ultra HD Forum members for their inputs.

Yoeri Geutskens writes about high-resolution audio and video, including Ultra HD and 4K.