Measuring Up With DisplayHDR

For the past 16 years, the High Definition Multimedia Interface (HDMI) has ruled the roost for display connections, pushing aside VGA at first and then DVI on everything from televisions and Blu-ray players to laptop computers and camcorders. It’s evolved numerous times from a basic plug-and-play interface for televisions and AV receivers to a high-speed transport system for 4K and ultimately 8K video. Ironically, HDMI is often the input and output connection for video encoders and decoders that, in theory, could displace it from the market altogether.

But there are other players in the interfacing market, and that would be the folks at the Video Electronics Standards Association (VESA), who developed and periodically update DisplayPort. First launched in 2006, DisplayPort was intended to replace the old analog VGA connector with a newer, 100%-digital version that could handle many times the bandwidth of an XGA (1024×768) or UXGA (1600×1200) video signal.

Other forward-looking features included direct display drivers (no need for a video card), support for optical fiber, multiplexing with USB and other data bus formats, and even a wireless specification (it never really caught on). Like HDMI, DP had its “mini” and “micro” versions (Mini DP and Mobility DP).

In recent years, VESA stayed current by upping the speed limit from 21.6 to 32 gigabits per second (Gb/s), supporting the USB 3.0 Alternate Mode, adding some cool bells and whistles like simultaneous multi-display output, adopting the first compression system for display signals (Display Stream Compression), recognizing high dynamic range metadata formats, and even accepting color formats other than RGB.

Best of all, there continue to be no royalties associated with DP use, unlike HDMI. The specification is available to anyone who’s interested, unlike HDMI. And DP was ready to support deep color and high frame rate 4K video as recently as 2013, unlike HDMI.

However…unlike HDMI, DisplayPort has had limited success penetrating the consumer electronics display interfacing market. While some laptop manufacturers have adopted the interface, along with commercial AV monitors and video cards for high-performance PCs, HDMI is still the undisputed king of the hill when it comes to plugging any sort of media device into a display.

Even long-time supporters of DP have switched allegiances. Apple, known for using Mini DisplayPort on its MacBook laptops, is now adding HDMI connections. Lenovo, another DP stalwart, is doing the same thing on its newer ThinkPad laptops.

One of the many DisplayHDR-certified monitors in VESA’s booth at CES 2018.

But VESA has a few more tricks up its sleeve. Earlier this year at CES, VESA had several stands in their booth demonstrating a new set of standards for high dynamic range and wide color gamuts on computer monitors – specifically, those using LCD technology. DisplayHDR calls out specific numbers that must be achieved to qualify for DisplayHDR 400, DisplayHDR 600, and DisplayHDR 1000 certification.

Those numbers fall into the categories of 10% full white, full screen white “flash,” and full screen white “sustained” operation, minimum black level, minimum color gamut, minimum color bit depth, and black-to-white transition time. With interest in HDR video growing, the DisplayHDR specifications are an attempt to get around vague descriptions of things like color range (“70% of NTSC!”) and contrast ratios that don’t specify how the measurements were taken.

And this is actually a good thing. In the CE world, the UHD Alliance has a vague set of minimum requirements for a TV to qualify as high dynamic range. Compared to the more stringent DisplayHDR requirements, the UHD Alliance specs are equivalent to asking if you can walk and chew gum at the same time. Whereas HDMI version 2.0 (currently the fastest available) can transport an Ultra HD signal with 8-bit RGB color safely at 60 Hz, that’s setting the bar kinda low in our opinion.

In contrast, DisplayPort 1.3 and 1.4 (adds HDR metadata and support for 4:2:0 and 4:2:2 color) aren’t even breathing hard with a 12-bit RGB Ultra HD video stream refreshed at 60 Hz. And that means a computer display certified to meet one of the DisplayHDR standards can actually accept a robust HDR signal. (Note that VESA isn’t choosing sides here – DisplayHDR-certified screens can also use HDMI connections, but signal options are limited by HDMI 2.0’s top speed of 18 Gb/s.) You can learn more about DisplayHDR here.

With HDMI 2.1 looming on the horizon – a new version of the interface that liberally borrows from DisplayPort architecture – VESA will certainly have its work cut out. The accelerated trend to 4K and ultimately 8K imaging will help, as DP can get to the faster data rates more quickly than HDMI. And the DisplayHDR standards aren’t just fluff – they’re also a way to expand awareness of the DisplayPort brand.