Letter from America: The Significance of Better Pixels
In last month’s Letter we spoke to the changes in audio that are revolving around the world of improved video content.
To provide the full view, we’ll pair that for this month with some thoughts on the video side of the fence. As with audio, the technologies are clearly changing, but consumer awareness of the new technologies does not always line up with their availability. That often leads to confusion, so perhaps a few words on that subject are in order.
At the top level, by now most people are likely to understand that the “4K” in “4K/UHD” conveys that proper UHD images have a resolution of 3840 x 2160, Or four times the resolution on a standard 1920 x1080 image display. True, but as has also been often said, at least here, to properly convey the full benefit of UHD it is not just “more pixels”, but “better pixels” and “faster pixels”. The “more” is obvious and it is always there either in the native content or in lower resolution that is (hopefully properly) scaled to UHD.
The latter is certainly helpful, but for the most part it is outside of our control. The frame rate at which the content is show is set by the program’s producers, and depending on whether it is an episodic TV drama or a sports event it could be anything from a “fractional” frame rate at 23.98fps (for content meant to “look like film”) all the way to 60fps for sports and live content. Yes, the formats provide for 120fps and beyond, but at this time that’s out of the range of consumer products for a variety of reasons on the connectivity and display side. At the end of the day, in most cases, what you and your clients see on the screen is what was captured in production.
Where the fun is coming is in the “better pixels” part of the equation. Within that are two main sub-categories: “WCG”, or Wide Colour Gamut and “HDR” or High Dynamic Range. They are where the real improvement, along with the fun and confusion begin and they are our inner topic this month.
Colour Gamut is also commonly known as the “Colour Space”, or in other words a modeled representation of how much of the actual colour the human eye can perceive is able to be displayed by a video system. The familiar CEI 1932 triangle-ish charts you’ve seen outline this and then inside that there are the various standards defining how much of that and with which colours a system can accommodate. Set by standards bodies such as SMPTE and the ITU, they take into account the capabilities of the display as it doesn’t make sense to carry colours the display can’t reproduce.
The trail of progression starts with Rec. 601, which was the standard created back in the days of “SD” video played back through CRTs. After all that was all we had at the time. Today’s standard of “Rec 709” is based around HD video but is still matched against what CRTs can reproduce. Yes, we’re now in the world of LCD, OLED and various forms of projection, but Rec. 709 still rules the roost. “P3” is the Colour Space for digital cinema, taking into account the equipment and unique requirements of that channel of distribution and display. Finally, Rec. 2020, as promulgated by the ITU, takes into account the improved capabilities of 4K/UHD as well as contemporary display technologies to take the edges of the colour space out even further.
The construction and definition of colour space also includes the bit-depth used to sample the image. Most production and many displays are still 8-bit. Newer displays are 10-bit with 12-bit possible, but not wide spread. The capability to deliver this from the camera all the way through to the display is technically possible, but to date rarely used. In most cases that is due to the increased bandwidth that requires in the content delivery chain.
Dynamic Range, the other half of “better pixels” is an expression of the system and display’s ability show a range from black to white. The notation for this is often shown in the number of photographic “stops” that can be shown. A standard display system might be said to show about four stops; the best HDR systems have a range of up 14 stops. That gives the viewer an image that can show more detail in dark areas without blooming in white areas since the contrast range is greater. The better the HDR representation, the brighter the display can be as you don’t have to worry about blowing out the image from a sunny window while still trying to show that, for example, someone in a dark outfit is hiding away from the bright light under a desk or in a corner of the sun-lit room.
Fine, outstanding! So why can’t we, and for the most part at this time why don’t we have these “better pixels” options today? A good question, indeed. Or, perhaps if you don’t closely read or understand some of the manufacturer promotional material, isn’t it true that we have these features today?
Let’s hold the answer to the latter for our conclusion for a moment. The fact is that for actual implementation, WCG and HDR must both be complete end-to-end systems. That is, the imager and camera system must capture to the limits of the range in question, the post-production system must deal with it and carry it through to distribution, the distribution medium, be it physical or streaming/cloud-based must carry it, the in-home devices must all recognise it and finally the display must be capable of showing it.
Sounds easy, but it is not. In the case of WCG’s better pixels, most cameras used to capture 4K native content can accommodate the requisite number of stops. Post production “work flow” systems are in place, or are on the way, to “grade” the content to Rec. 2020. The problem, however, is the display side of things.
Outside of some rare and very expensive OLED production quality monitors and laser projectors shown at April’s NAB Show in Las Vegas as well as other recent technical conferences, there are simply NO displays, and certainly none in the consumer world that can show the Rec. 2020 images. Even the amazing 8K demonstrations at NAB from Japan’s NHK used only Rec. 709 colour. Simply put, as much as we’d love to see Rec.2020 in the home, as of today it is akin to the old cliché about a tree falling in a forest: If no one sees it, is it really there?
We’ve seen demos of it and thus confirm it is there, but it will be a while before it comes home. When it does, it will definitely given the total package of UHD something amazingly demonstrable that we are certain will spur new set sales and upgrades. [But DO NOT ask me when that will be; it is just too soon to know.]
If WCG is still out there on the time line, is the notion of “better pixels”, as well? Thanks to HDR, the answer is no.
High Dynamic Range, and remember that it is also an end-to-end system in place, but the degree of difficulty to deliver it is not as huge. Coming out of CES, and more recently, NAB, we not only see all the capture, “post” and delivery systems in place there, as well. Content providers such as Warner Home Video, Netflix and Amazon Prime have committed to delivering HDR-encoded content. At least one set manufacturer, though unfortunately for our readers in the UK and EMEA, it is the US-only Vizio, has announced availability of HDR sets for this year.
But wait, you’ll correct me, didn’t Sony announce that models in their new line for 2015 will accommodate HDR? Haven’t other brands promoted what sounds for all the world like “HDR”? Yes, you would be quite correct to say that, but that also leads us to a message point later in this Letter.
To address the latter, it must be repeated that to be “real HDR” you must have an end-to-end system with content produced, prepared and distributed in HDR. To display it, you need to have circuitry and connectivity all along the line that recognises that HDR is present and passes it through unaltered. You also need to have the circuitry in the display to recognize it and then finally show it. As of this writing, there isn’t a consumer display available with true HDR. On the content and system side at this time, other than some very new AVRs, none of the intermediary devices we provide and integrate have the HDMI 2.0a capability needed to pass HDR through.
Oh, and there is one more thing to remember. You’ll often see joking mention here that no consumer electronics system is worth its salt if it isn’t part of a format war. HDR has just that.
While, just as on the production work-flow side for audio there is movement towards a single standard for object-based audio that then gets distributed as one of the three main proprietary systems discussed last month (Dolby Atmos, DTS:X or Auro3D), the same pattern is falling into place for HDR. A standardised way of describing HDR content is falling into place and it seems that at least for a while we’ll see most or all of them in the marketplace.
Dolby Vision currently has the most visible adherents with Vizio and Warner on board with more more promised shortly. Competitive systems have been developed by Technicolor, Philips, Japan’s NHK and the BBC, but none of them have yet announced who will offer it on the content or display side.
That is where we raise the caution flag. For example, while it is true that Sony have said they will support HDR, they have not disclosed which format(s) that will be. The same goes for the other content suppliers and streamers. Which will they select? One, some, all? The standard for UltraHD Blu ray is agnostic. It mandates support for all but requires or specifies none.
Thus, while we acknowledge and anxiously await the widespread availability of content, displays and all the other signal chain products required to bring these “better pixels” home, the reality is that right now it is a tough task due to the simple fact that the kit isn’t here yet.
The final caution flag is key as you prepare bids and proposals. Some brands are claiming “HDR” using descriptors that make it sound like they are capable of recognising the metadata that is part of an end-to-end system to tell the display how to show the improved image, not the standard-range baseline. Without full HDR what you are really being offered is advanced signal processing that may certainly be able to display great image quality, but it simply can’t be the HDR you will get in a product that has it all.
Isn’t this all fun? You have the promise of considerably better images to accompany UHD’s high resolution.
You have some parts of that will be available within this year and some that may be a bit further off in the distance. You have a variety of options as to how much of the new technology a given product will deliver, and to round out the package we have the uncertainty of specifying products in the midst of a looming format battle that has barely started, let alone be headed toward a resolution. Yes, it is fun if you play it right.
As always, be aware of the what the benefit to the end user is. Know what is available now and what is not. Know what can be upgraded and what not, and in this case the answer there is regrettably not much. Arm yourself with the proper information and you’ll make it through this one just fine.
Michael Heiss is a technology consultant and journalist, CEDIA Fellow, CEDIA ESC 2 Certified, and US correspondent for HiddenWires magazine. You can contact Michael via the HiddenWires LinkedIn Group, follow him on Twitter @captnvid.