Serious interest in enhanced HDTV with HDR as an alternative to basic 4K

The possibility of an enhanced version of HDTV as an alternative to 4K and even as an alternative to what people are calling real UHD or premium UHD (meaning 4K plus high dynamic range, higher frame rates and wider colour gamut) seems to be gathering support. Ericsson has thrown its weight firmly behind the concept and reckons there will be serious interest from service providers with limited bandwidth, not only using OTT networks but even on bandwidth constrained broadcast networks.

At Ericsson TV Live London last month the company gave a brilliant demonstration of how much better HDTV can look simply by adding high dynamic range (HDR) support. With HDR the colours and detail were noticeably better. And according to Matthew Goldman, SVP Technology, TV Compression at Ericsson, HDR can be supported with potentially very small increases in bandwidth. He says the bit rate increase could be as low as zero and as high as 20% depending on the content and how you encode it (and he is confident it can be kept down the low end of this range).

Goldman and his colleague Lukasz Litwic, Principal Engineer at Ericsson, presented a paper at NAB this year on ‘Implications of High Dynamic Range on the Broadcast Chain for HD and Ultra-HD Content’, which looks at the benefits of HDR to consumers and how different approaches to HDR can impact bit rates when using existing encoding technology. The paper also looks at the compatibility of HDR services with television displays that only support standard dynamic range. Ericsson won the NAB Best Paper Award for this research. 

At Ericsson TV Live London the company focused on the implications of HDR for HDTV and had two big screen displays alongside each other, both receiving the same HDR-enabled signal (with 10-bit sampling depth) that was filmed on Sony cameras. The first television supported HDR so could display the additional contrast information and the second did not, so just ignored it. One of the video sequences showed an aerial view of a football stadium where the buildings and especially the tops of gas storage tanks near the football ground were much clearer. The green football pitch stood out far better against the night sky on the HDR display. There was also a sunset over a city where the buildings were much clearer, and a scene of someone swimming that, more than any other, highlighted the difference between HDR and non-HDR viewing.

One of the main points of the demonstration was to show that you can achieve something of a ‘wow’ effect without needing 4K or UHD. Ericsson believes in the concept of ‘Immersive TV’ and considers enhanced HD to be one of the options that should be available in an expanding choice of profiles to make up the next-generation big screen experience. Goldman said Ericsson would like to see a 1080 [HD resolution] profile that contains enhancements currently being lined up for premium UHD, namely HDR, 10-bit support and wider colour gamut. “This would be for people who are limited in the bit rates they can apply [due to bandwidth constraints] but who want to deliver an immersive experience. Maybe you can provide the immersive experience with HD,” he suggests.

This could mean taking the HD signal and upconverting it to UHD on the television set, complete with HDR and the other enhancements, and it would not require the same bandwidth as UHD. Goldman says this could be a better approach than using a UHD signal but squeezing the bit rate down in order to get it across a lower bandwidth network like OTT. 

Ericsson believes that HDR must come as a package with expanded colour range and also 10-bit depth, which is already used for contribution signals and provides more banding levels for shades, avoiding the ‘banding’ or contours that you can sometimes see on dark scenes with HDTV today. Goldman points out that one of the big changes between the HEVC compression standard and its predecessors, MPEG-2 and AVC, is the inclusion of a direct-to-home (transmission network) profile supporting 10 bits. Importantly, 10-bit comes free in terms of bandwidth. Encoders receiving contribution signals in 10-bit have less work to do when encoding the transmission video stream with 10-bits than if they construct an 8-bit stream, so there is no impact on bit rate. Goldman says platform operators will deploy new HEVC set-top boxes whether they want to go down the enhanced HD or UHD road.

Ericsson is a fierce supporter of single layer HDR, saying that dual layer HDR is only suitable for physical media like Blu-ray. Taking this approach, there is no impact on the production and transmission chain if you add HDR to the HDTV signal, the company reckons. So this approach could suit any media company whose facilities are not ready to carry 4K signals or who are using networks (including CDNs) that cannot cope with the extra bit rates that 4K/UHD demands. Giving the HD-HDR demonstration with Goldman, Mark Horton, Strategic Project Manager, Encoding Portfolio at Ericsson, suggested: “There are some people thinking that maybe they don’t need 4K at all, and that maybe HD with these changes is enough for consumers, so this is therefore an option.”

Goldman points out that if the difference between enhanced HDTV and 4K/UHD is only marginal in the eyes of consumers then media companies will then turn their attention to the issue of bandwidth. “They want compelling new services and the key is immersive television and the viewing quality,” he argues. 

Ericsson believes media companies want an immersive TV offer of some kind, and the emphasis is on delivering the characteristics of ‘immersive’ and that is not necessarily tied to one particular profile of next-generation television, including premium (or real) UHD. Goldman emphasizes: “Within immersive television there could be a range of what is offered. There is a trade-off because bandwidth is not free. So what is the most compelling service you can offer while being bit rate efficient? People want the best bang for their buck.”

This all seems to point to some media companies – like bandwidth constrained service providers – investigating enhanced HD as an alternative to basic 4K resolution (basic UHD) services, given that some people cannot see enough difference between simple 4K (without HDR) and HDTV on normal sized televisions. Ericsson has conducted its own research that shows that 4K on its own provides little noticeable benefit over HD unless you are watching on very big screens, and this is currently a limited part of the market. 

Thus the range of television options for a living room TV could expand to include not just SD, HDTV and simple 4K (basic UHD) with its 3840 x 2160 resolution and 24 frames per second for film and typically 50/60 fps for television. It will probably include true (real, premium) UHD that adds 10-bit support (and insists on 10 bit minimum depth), HDR, wider colour gamut and frame rates up to 100/120 fps. This technology grouping could be deployed in 2017 onwards if the industry agrees the specifications this year. Then there is 8K television, driven from Japan, for the longer term. More immediately a 1080p HD profile with HDR, 10-bit and wider colour gamut could emerge. And there may even be an appetite for a profile that takes simple 4K and adds just HDR.

Ericsson is certainly not dismissive of (simple) 4K UHD. “We simply think that 4K is not enough on its own,” Mark Horton said during the HD-HDR demonstration, a stance that is shared by plenty of major media companies. Goldman adds: “Most people consider it an intermediate step. It suits some services, mostly for on-demand or OTT, just so they can say they are doing UHD but it is all pre-recorded content.” 

Ericsson expects operators who want 4K resolution to move as soon as possible to enhanced UHD (with HDR, wider colour gamut, 10-bit, higher frame rate potential) if they are not taking the enhanced HD option. “Neither approach is right or wrong,” Horton noted.

Over the last year HDR has been recognized as an important tool for next generation TV. It increases the grades between black and white and by improving contrast it also makes pictures look more detailed and enhances colour. In effect you get to see, as a viewer, something closer to what the camera sees. The net result is that television is more realistic – more like the real world than a picture – and that is why it is so significant if you want to create an ‘immersive’ experience. During the HD-HDR demo Horton said it was especially beneficial on films and sports and excelled on a British winter afternoon when football coverage has to compete with a winter sun and lots of shadow. 

One of the key benefits of HDR, in terms of how you address the market, is that it performs its magic on any sized screen, from a tablet upwards. Thus it can be applied to multiscreen TV and to 32-inch televisions showing HDTV. Unlike basic 4K/UHD, there are no debates about what size screen you need or how close you need to be to the screen before consumers notice a better picture. HDR has universal benefit and so is a great complement to 4K resolution as well. Of the various enhancements that can be used with UHD (and HD), Goldman says it is HDR that really seems to make a big difference. 

Interested in ‘Immersive TV’?

Check out the Connected TV World Summit 2015 conference session on Immersive TV here, featuring Andy Quested, Head of Technology BBC HD & UHD, BBC and Andy Gower, Head of Interactive TV Research, Future Consumer Applications and Services, BT Research & Innovation, among other speakers.