There are currently two industry groups fight for market standardisation what regards to HDR: UHD Alliance and Ultra HD Forum. Every time this happens is usually due to a fight over consumer awareness on something that doesn’t make sense. We’ve already seen what UHD Alliance brings (or doesn’t….), but know there is a new group trying to make your mind: Ultra HD Forum.
A lot has happened for last couple of years in the TV industry due to fuss around Ultra HD, always surrounded by confusion, mishaps and all around caos and damnation.
How we got here
Starting with the availability of Ultra HD TV sets which happened even before HDMI 2.0 was available as a standard, which created some very weird cases of TVs which were only able to support UHD formats from downloaded sources only, or others which only supported UHD at half the colour accuracy… Then again, UHD came and went as far as industry hype is concerned, and the next hype was need to sell more TVs, and that is High Dynamic Range, or HDR.
High dynamic range is a whole different beast as compared with UHD. Ultra high definition was limited to an increase of picture resolution, to 3840 pixels wide and 2160 pixels high, and although it required a new HDMI interface if you need to transmit that video stream uncompressed, it didn’t significantly change the way things work, including using the same cables (or not… sorry private joke). High dynamic range has far reaching implications, ranging from the content production ecosystem, to the way pictures are transmitted, but the most concerning of those is the need to a new colour space.
High Dynamic Range Explained
For a brief description, colour space represents the whole set of colours which can be represented, and how they are represented. Currently there are two major colour spaces on TV, defined by Bt.709 for HD quality and Bt.2020 for UHD and higher video. Unfortunately, the difference between then is not significant enough for most people to distinguish between then. On HDR, the whole objective is to enhance the whole range of colour, and more significantly, how bright those colours are, and to reach that objective the overall number of colours was also increased from around 4 000 000 to around 1 000 000 000, which is roughly a 64 fold increase. Not only that, but the actual representation of those colour also needs to be changed, from a linear based value, to an non linear (for the most knowledgeable of you, linearity is only for the overall light value, not color…).
This linear to non linear representation represents the most significant architectural change on television since the introduction of digital TV. Actually, it breaks the most fundamental designs defined on analog NTSC: linear light representation: the light output of a given phosphorus picture element (also known as Pixel 🙂 ) is proportional to the amount of energy received, which is proportional to the power of the electrons transmitting the information, and this is the fundamental change.
Why the change? Because the human eye doesn’t behaviour linearly as well. On very dark or very bright environments it adapts. It is capable of seeing more than 50 shades of grey ( 🙂 ) on a very dark room or transmitted coloured lights on very bright days, such as when sun shines on a billboard but none of those scenes are properly displayed on current TVs, not to mention the basic scene of a camera pointing directly at the sun, or at any light source.
The nice thing about standards is that you have so many to choose from.
The problems arise from the fact that there is not one single standard which solves all use cases (as UHD Alliance tried to do. More on that later), but when standards start to emerge solving all use cases, the end result are standards which are incompatible, bringing us to that epic quote from Andrew Tanenbaun “The nice thing about standards is that you have so many to choose from.”