HDR-TV-Standards: What technology is going on?

High Dynamic Range, or HDR, promises more: more brightness, more contrast, more plasticity and more color. It creates a much more intense, more authentic cinema adventure. This is undoubtedly true and we are looking forward to it from the video editorial team.


In the beginning was the light


The explosive mixture is currently taking the first hurdles. First of all, the TVs can be taught. HDR requires more light for optimal reproduction than most screens can currently produce. The second point to be clarified is that TV manufacturers already talk about HDR, but manufacturers and cross-selling standards are just starting to establish themselves. In this article, we explain the different approaches to bring HDR to home cinema.

What exactly is HDR?


The success that HDR can celebrate depends directly on the light output of the TVs. The larger it is, the more impressive the effect is. Here the hurdles are high. Brightness for screens is given in nits or in candelas per square meter (cd / m²), where 1 Nit corresponds exactly to 1 cd / m². Currently, most LCD panels light up with about 400 Nits. Peak values ​​reach a rounded 500 Nits. New or hitherto announced HDR panels now promise over-values ​​over or over 600 Nits.


Lesetipp


This raises the question of the minimum brightness for HDR. One of the scene pioneers is the already well-known company Dolby with its technique "Dolby Vision" in terms of sophisticated sound. It wants to explore the optimum and has found with consumer tests a brightness value for itself. The result, according to project manager Roland Vlaicu: a whopping 10,000 Nits. Such size orders can not be achieved at the moment. Even studiomonitors is the blow out - they are currently just calibrated to 100 Nits. This is why Dolby's practice is milder than in theory: the current recommendation to the manufacturers for Dolby technology is "only" 1000 Nits.


Dolby Vision is only one of several. There are even opposites. The American Institut für Rundfunktechnik (IRT) conducts research for German-speaking public service broadcasters. Rainer Schäfer, Head of the TV business segment, has contracted figures. According to him, subjects were already "dazzled" with a screen brighter than 1500 Nits. There are therefore considerations to limit at least large screens by standard to this value. This would also meet the energy consumption requirements of the European Union.


So what does "high dynamic" ultimately mean when the brightness is dispensed? Three popular approaches, originating from Dolby, Philips and the English program provider BBC, illustrate the other important details. With DolbyVision as the Rolls-Royce variant, the most brilliant images are created in the home cinema as well as in the real cinema. You can see even deeper black than the LCD TVs so far usually achieve, and clearly brighter white.


This also gives additional space to add more color and brightness levels between black and white. Thus Dolby achieves the most vivid images with the finest brightness traces of all HDR concepts. The figure "plasticity thanks to shading" at the bottom of this page illustrates the importance of numerous intermediate steps in brightness: excessive brightness steps cause visible gradations within the motifs, which the eye recognizes as image defects. A high number of steps can make the courses homogeneous and natural.


Compared to our current full-HD stand, the new era with ultra-high definition (UHD) will increase the intermediate steps by four times. DolbyVision wants to add another 16 times. Handicap: The enormous data volume must be able to cope with both TV transmissions and storage variants such as Blu-ray. With every additional brightness step, however, the data volume grows almost exponentially.


This high effort has called Philips to the plan. There, a concept has been developed, which is completely aligned with the UHD standard and thus reduces the amount of data to the soonest customary. Philips does not aim at 10,000 Nits maximum brightness, but 5000. This reduces the data base vehement.


But even with Philips, the amount of data is still high. Therefore, both work with a trick: some of the image data is not actually transmitted, but separate "metadata" merely describe how it is to represent the TV. Thanks to this combination, the amount of data to be transferred can be significantly reduced.


While Dolby continues to transfer "true" HDR data with this technology, Philips packs all HDR info into the metadata. The BBC proposal is even smaller and therefore the most uncomplicated. In this approach, 5000 Nits are also the target - which can be achieved without any additional information.