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22 April 2021

HDR hits 50% of UHD channels, says nomenclature-abusing event

Is it so hard to use the correct terms when describing things? Should we be allowed to throw things at marketers that misuse these names? Is this a fight we’ve already lost and we should just give up on? Well, thanks to a webinar from Harmonic this week, our teeth started grinding, against a backdrop of HDR adoption among broadcasters, channels, and VoD.

Harmonic’s Stephane Cloirec, VP of Video Appliance Product Management, kicked things off, rattling through Harmonic’s view of HDR – providing a more compelling user experience for the person watching TV, by allowing a TV to output more photorealistic images.

Immediately, however, we hit a running problem in this webinar, and in the industry at large. The nomenclature we use to describe things has been thoroughly abused, and off the bat, we had Cloirec talking about how HDR was able to convey more colors to the human eye.

The problem is that a number of distinct factors combine to create the image on a screen, and for marketers, it’s easier to talk about a three-letter-acronym than try to dish out a lecture, each time they want to hype a company up.

Specifically, the color output of a TV is down to whether it is using the old Rec.709 color-space, or whether it is capable of the new Rec.2020 color-space that is part of the new UHD standards. This determines whether we are using an 8-bit signal in Rec.709, giving us a maximum of 256 possible values for our Red, Green, and Blue signal, and there some 16.7 million possible colors.

For 10-bit color, we have 1,024 gradations for our RGB values, and therefore over 1.07 billion possible colors that can be represented by our pixels. Here, a 2-bit difference results in a 10x change. A technology called Frame Rate Control (FRC) can let us mimic 10-bit signals in 8-bit panels, but we are already moving towards 10-bit being commonplace. The next generation is 12-bit, which provides 4,096 RGB gradations, and some 68.7 billion colors.

High Dynamic Range, as the name implies, relates to creating an image with better contrast between the brightest spots in an image and the darkest ones. In a Standard Dynamic Range (SDR) image, we would lose the details in a bright sky or a shadowed corner. With HDR, we are able to see these details, thanks to the improved ration between the brightest and darkest.

But this is all to do with how much light the TV can throw out. Old TVs had to deal with around 100 nits (a nit is equal to the amount of light generated by one candela per square meter, or cd/m2). Modern HDR-capable TVs can handle between 250 and 400 nits without sweating much, with some capable of far more.

You will note that color isn’t mentioned when discussing dynamic range, but of course, better backlighting technologies, driven by the adoption of LEDs and new grid designs, provide a better strength and quality of light, which helps us more accurately produce all those colors defined in the new color-space.

So, without the increased brightness, we can’t accurately reproduce the better color. However, it is not good practice to talk about HDR producing better color. After all, we could add HDR to an 8-bit Full HD signal and notice the quality improvement from the better dynamic range, over the SDR counterpart.

The final abused term is UHD. This should be understood to mean a TV that is capable of producing the Rec.2020 color space, with HDR, at a resolution of 3840x2160p, and a frame rate of 60fps – as per the ITU standards. Of course, thanks to marketers, the resolution was the easiest new sticker to slap on the box to shift more units, and so we have a bunch of consumers that think “4K” and “UHD” are interchangeable. An 8-bit SDR signal at a 4K resolution is absolutely not UHD.

To this end, we were quick to pounce on the webinar’s mention of the UHD Forum’s recent declaration that over half of UHD channels have HDR capabilities, noting that we shouldn’t be calling them UHD if they did not have HDR by default, and that only having 50% of UHD channels supporting HDR should be seen as a massive failure. This implies that they are 4K channels, and only half of them are actually UHD.

A text answer came through, which in a garbled fashion tried to explain that the adoption followed HDR-enabled TVs and devices, which started later than the availability of 4K resolutions, “and that it should not be a surprise that there are still today UHD channels without HDR.”

Now, that was a pretty woeful and utterly incorrect response from whoever was in charge of the Harmonic Live Summit Q&A control panel, but at least we got something of an answer. This brings us to another gripe with the event, which was the attempt to make it sound like an organic conversation, but betrayed its scripting with a prepared slide for every talking point. But hey, at least it was live.

Unfortunately, presenters wrapped things up without taking any questions from the audience. Despite the Europeans having daylight behind them, and Colorado-based Felix Nemirovsky, Dolby’s Media Delivery Ecosystem Expert, sporting a darkened backdrop, suggesting that we were watching something in real time, we’re still not sure whether that was actually a live event.

Now, prerecording elements of it wouldn’t be so bad, but it means that points like the abuse of UHD in the presentation can’t be challenged by the audience. Sure, whoever typed up the response to our question was watching along with us, but this seems like another event with no access to the speakers – and worse, speakers that are knowingly or unknowingly furthering confusion in the industry.

We appreciate that we are sticklers for terminology, and many would not be so anal about it, but the event definitely got off on the wrong foot. After the introduction, b<>com’s Tania Pouli, Deputy Lab Manager, described how HDR-capable capture devices allow you to capture light how it really looks, but that this in turn means you have to pay a lot more attention to the production environment, to make sure that you get the capture right. Here, light allows you to tell a more creative story.

Dolby’s Nemirovsky added that the way we watch TV has changed, as HDR has emerged, and that we are now able to bring this improved quality content to devices such as smartphones. Phabrix’s Prinyar Boon, a Project Manager, added that it is hard to buy a TV these days without it being HDR-enabled, which isn’t quite true. It’s certainly easy to buy HDR, and it’s definitely no longer a premium feature, but it’s not yet standard across the range.

A popular retailer here has 263 TVs listed for sale. The first 30 featured results list 21 HDR models – near enough 70% penetration. If you filter from lowest price, only 11 of the cheapest 30 have HDR. Unsurprisingly, the 30 most expensive all support HDR, but notably, many of them don’t list HDR in their product names – requiring an additional click to check that you haven’t just found a $5,000 television without HDR.

The discussion was then turned to the challenges of transitioning content production chains to accommodate the new HDR standards. Nemirovsky said that production cameras that generate the required HDR metadata natively are still too expensive to be commonplace – meaning that you need to create the HDR metadata after your scene has been captured. This is a significant cost barrier, according to Nemirovsky, who added that it also prevents knowledge about HDR production from spreading as easily.

On the distribution side of things, the speakers agreed it was much easier. Nemirovsky said it was just a matter of delivering the video to the head end as either Hybrid Log Gamma (HLG) or Perceptual Quantizer (PQ), and then the broadcaster can encode it however it likes – before pushing that video out to the distribution networks. Harmonic described how it was using a b<>com technology to add HDR at the last step, in some workloads.

b<>com’s Pouli touched on the headache that is migrating your production workflow to HDR, describing the two main approaches. The more conservative approach is staying within the BT.2408 realm, and producing SDR and HDR in parallel, where HDR is only a slight improvement. This allows for a more gradual migration. The other approach is to go whole-hog, which is riskier because you will have jumped further from familiar surroundings.

Phabrix’s Boon said that these new workflows are well understood now, but that you still need to be careful that you keep the SDR and HDR pictures within tolerance of each other. Boon added that outdoor live sports is particularly challenging, in that regard, due to the mix of camera types and the likelihood of encountering a mix of 8-bit and 10-bit equipment in the production chain. However, the EPL and UEFA have been producing HDR for the past 18-months, proving that this is achievable, according to Boon.

At this point, the conversation turned towards the use of HDR for Full HD content, but Dolby’s Nemirovsky warned that this view is very broadcast-centric – that ABR in VoD allows you to deliver cinematic experiences to all manner of devices.

Nemirovsky stressed that adding HDR can be a big headache, because you have to upgrade your entire postproduction environment to have all your on-screen elements available in both SDR and HDR formats. Technically, he added, HDR doesn’t have to be UHD (resolution), but at the same time, you have to invest in these technologies at some point. Phabrix’s Boon added that most replays in live sports broadcast in UHD are actually being presented in 1080p, and those still look fantastic in HDR.

Dolby’s Nemirovsky argued that HDR in VoD applications has been so successful because the creators understand that they are able to create exactly the image they want. They are not subject to the same constraints that the live production crews have to deal with, and now consumers are expecting live content to look as good as the HDR content they get through VoD services. As it just so happens, Dolby Vision can be created from the HLG feeds, as well as HDR10, which means that adding HDR to live feeds is now a lot easier than it used to be. Isn’t that convenient?

b<>com’s Pouli warned that live content needs to embrace HDR quickly, or risk harming the technology’s reputation in the market. If viewers turn on a live feed, after becoming familiar with HDR in VoD, there is a risk they will think the content is either underwhelming or that the channel is broken. You can find many examples of these complaints on internet forums, Pouli warned – and that’s especially problematic, because those early adopters are usually quite evangelical about their opinions.

The panel wrapped up, sharing their thoughts on where HDR would be in a year’s time. Dolby’s Nemirovsky said it was now obviously a case of when, not if, but that this is down to broadcasters implementing HDR in their channels and workflows. b<>com’s Pouli thinks that the resurgence of live sports should drive an uptick in HDR adoption too.

Phabrix’s Boon added that Covid will have knock-on effects, and that the Tokyo Olympics were initially promising something like 9,000 hours of HDR content. Finally, Harmonic’s Cloirec returned to the UHD Forum’s channel penetration, and said that only three months ago, the number of channels was way below 50%.