Posts Tagged ‘HDMI 2.1’

HDMI 2.1 Update – Pretty Much Status Quo

Last Thursday, a joint press conference was held in New York City by the HDMI Licensing Administrator to update attendees on the latest version of HDMI – version 2.1.

V2.1, which was officially announced at CES in 2017, represents a quantum leap over earlier versions. It’s the first HDMI architecture to use a packet-based signaling structure, unlike earlier versions that employed transition-minimized differential signaling (TMDS). By moving to a packet transport (an architecture which V 2.1 apparently borrowed a lot from DisplayPort, according to my sources), the maximum data rate could be expanded several-fold from the previous cap of 18 gigabits per second (Gb/s) to a stratospheric 48 Gb/s.

What’s more, the clock reference can now travel embedded in one of the four lanes. Previously, HDMI versions up to 2.0 were limited to three signal lanes and one clock lane. And of course, a digital packet-based signal stream lends itself well to compression, accomplished with VESA’s Display Stream Compression (DSC) system that is also the basis for Aptovision’s Blue River NT technology.

The HDMI Forum simply had to kick up the performance of the interface. Version 2.0, announced five years ago, was perceived by many (including me) to be too slow right out of the gate, especially when compared to DisplayPort 1.2 (18 Gb/s vs. 21.6 Gb/s). That perception was prescient: Just half a decade later, Ultra HDTVs are rapidly approaching the unit shipment numbers of Full HD models, and the bandwidth demands of high dynamic range (HDR) imaging with wide color gamuts (WCG) need much faster highways, especially with RGB (4:4:4) color encoding and 10-bit and 12-bit color rendering.

And if we needed any more proof that a faster interface was overdue, along comes 8K. Samsung is already shipping an 8K TV in the U.S. as of this writing, and Sharp has introduced a model in Japan. LG’s bringing out an 8K OLED TV in early 2019, and Dell has a 32-inch 8K LCD monitor for your desktop.

To drive this point home, IHS analyst Paul Gagnon showed numbers that call for 430,000 shipments of 8K TVs in 2019, growing to 1.9 million in 2020 and to 5.4 million in 2022. 70% of that capacity is expected to go to China, with North America making up 15% market share and western Europe 7%. Presumably, at least one of the signal inputs on these TVs will support HDMI 2.1, as even a basic 8K video signal (60p, 10-bit 4:2:0) will require a data rate of about 36 Gb/s, while a 4:2:2 version demands 48 Gb/s – right at the red line. (DSC would cut both of those rates in half).

Aside from stating that over 900 million HDMI-equipped devices are expected to ship in 2019 (including everything from medical cameras to karaoke machines,) HDMI Licensing CEO Rob Tobias didn’t offer much in the way of real news. But I had a few deeper questions, the first of which was “Is there now native support for optical interfaces in the HDMI 2.1 standard?” (Answer – no, not yet.)

My next question was about manufacturers of V2.1 transmitter/receiver chipsets. Had any been announced that could actually support 48 Gb/s? According to Tobias, HDMI Forum member Socionext, a chip manufacturer in Japan, has begun production on said chipsets. I followed that reply up with a question about manufacturer support for DSC in televisions and other CE devices, but couldn’t get a specific answer.

Much of the discussion among these panel members and David Meyer (director of technical content for CEDIA), Brad Bramy, VP of marketing for HDMI LA, and Scott Kleinle, director of product management for Legrand (a supplier to the CEDIA industry) was focusing on future-proofing residential installations that used HDMI interconnects.

But why not just go optical for all HDMI 2.1 connections and guarantee future-proofing? The responses I got to my last question were mostly along the line of “The installer just wants it to work the first time.” Yes, there are faster (Ultra High Speed) HDMI cables available now to work with V2.1 connections. But an HDMI cable that has to run 20, 30, or 40 feet at over a GHz clock rate is a pretty fat cable!

Multimode fiber cable is inexpensive compared to Cat 6 cable and the terminations are not difficult to install. Running strands of fiber through conduit, stone, and behind walls seems to be the most logical solution at the required speeds and is certainly what I’d recommend to installers in the commercial AV market. Properly terminated, optical fiber works the first time and very time and can run over a mile without significant signal degradation.

Once again, the HDMI Forum will have a booth at CES in the lower South Hall. With a new display wrinkle lurking in the shadows – high frame rate (HDR) video – there will be more upward pressure than ever on data rates for display connections. HDMI 2.1 may be up to the task (most likely aided by DSC), so I will be curious to see if there are any 8K/120 demos in Las Vegas. – PP

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.

HDMI 2.1: The Need For Speed Continues

Ever since HDMI version 2.0 was announced in September 2013, I’ve been pretty vocal about criticizing its “not quite fast enough” speed upgrade from 10.2 to 18 Gb/s, which turned out to be barely adequate for transporting 4K (3840×2160) video at full color resolution (RGB, or 4:4:4 in the world) at a frame rate of 60 Hz – and only with 8-bit color.

Given how quickly the display industry is shifting to 4K and even higher resolutions, it was inconceivable that this new interface would in effect create a “speed bump” in the 4K chain, particularly since high dynamic range (HDR) and wide color gamut (WCG) enhancements were becoming part of the UHD ecosystem. And both enhancements require at least 10-bit color rendering, something that would be impossible to pass through the HDMI 2.0 interface if using a full-resolution color format.

It didn’t help that HDMI’s competitor – DisplayPort – had already broken the 20 Gb/s barrier way back in 2007 with version 1.2 and could easily interface a 2160p/60 signal with 10-bit RGB color @ 60 Hz, and earlier in 2013 had announced version 1.3, which saw a speed boost to 32.4 Gb/s.

For a time there, I thought the superMHL format, which had its debut at CES 2015, might be the successor to HDMI. It was faster (36 Gb/s), had a large, reversible connector, was compatible with USB Type-C Alternate Mode, and most importantly, supported Display Stream Compression.

Alas; it appears superMHL turned out to be mostly a science experiment. The MHL Forum was conspicuous by its absence at CES 2017, but the HDMI Forum more than made up for it by unveiling version 2.1. And now, we’ve got a real horse race.

High dynamic range support will be much easier with version 2.1, especially deeper color from RGB sources.

THE DETAILS

The public press release on HDMI 2.1 is sketchy on details, except to say that the maximum speed of the interface has now reached a mind-boggling 48 Gb/s (that’s faster than most network switches!). Quite the leap from 18 Gb/s, wouldn’t you say?

The release goes on to talk about a new generation of 48G cables, a greatly improved eARC audio return channel with auto-detect, and finishes with a discussion of high dynamic range and higher video resolutions, both of which are possible with faster data rates that enable higher frame rats and deeper color. And of all of this happened while retaining the familiar 19-pin Type A connector. (Wha-a-a-t?)

But what’s really going on here? How did HDMI accelerate to 48 Gb/s? Hold on, and I’ll provide the details missing from the press release.

First off, the current version of HDMI uses three connections – well call them lanes, like DisplayPort does – to transport red, green, and blue display pixels. There’s a fourth lane for the clock to synchronize frames, and the balance of the connectors are used for ‘hot plug detect’ connections, the Data Display Channel (EDID). That doesn’t leave much room for expansion.

But HDMI 2.1 adds another lane for TMDS data (although it’s not really TMDS anymore) by taking over the clock lane and embedding clock data within the existing signal, much the same way it’s done with packet-based signaling systems.

Next, the physical data rate over each lane has been raised from 6 Gb/s to 12 Gb/s. I don’t know how that 100% increase was achieved, but that’s an impressive achievement considering that we are still waiting for 12G SDI cables to come to market.

The 12G number may also be a function of jiggering the acceptable signal-to-noise (SNR) ratio, something proposed a year ago by Steve Lampen of Belden – but then again, we’re not likely to see 12 Gb/s of data traveling down any display pipes in the immediate future. (For comparison, DisplayPort’s HBR3 cap is 8.1 Gb/s per lane.)

That’s not all. The standard ANSI coding format for HDMI, DVI, and DP (not to mention numerous other interfaces) is known as 8b/10b, coding 8-bit words into 10-bit symbols, resulting in about 20% overhead. Example: A 4K/60 signal encoded as an 8-bit RGB signal requires 17.28 Gb/s, and 20% of that is overhead from 8b/10b coding.

HDMI 2.1 has adopted a more obscure form of coding known as 16b/18b. You can find a IEEE PDF from 1999 describing how it works here, and it’s formally known as “partitioned DC-balanced 16b/18b transmission code.” The net effect of moving from 8b/10b to 16b/18b is reducing the overhead to about 12% from 20%. What’s interesting though is that the HDMI 2.1 signal isn’t really TMDS we’ve come to know and love when in this mode – it’s something else, possibly more of a packet structure.

HDMI is now compatible with USB Type-C Alternate Mode – a”must have” feature for any new display interface.

Last but not least, HDMI announced last fall that it was compatible with the USB Type-C Alternate Mode format. And now, it appears that HDMI 2.1 is also compatible with DisplayStream 1.2 compression, which is a much more efficient way to transport signals like 7680×4320/60 (8K, for those not paying attention). Although at 48 Gb/s, version 2.1 could theoretically transport that signal uncompressed using 4:2:0 color.)

Compatibility with DSC wouldn’t be that much of a shocker – superMHL also offered it and it’s another TMDS format. In fact, at second glance, it appears that much of the engineering that went into superMHL has now migrated over to HDMI 2.1 (about time) and the most significant breakthrough is doubling the interface speed.

Given that 40 Gb/s is definitely optical fiber territory, the only remaining question is why we still haven’t seen a detailed HDMI specification for direct optical interfaces. 48G cables will be expensive and difficult to engineer, but multimode optical fiber can already do the job and is cheap. To come up with 50-foot and longer manufactured optical cables for HDMI would be a piece of cake – and it’s already been done in the past for HDMI 1.3/1.4.

So there you have it: HDMI 2.1; a faster, smarter, and more appropriate display interface as we head into the era of 4K and beyond. How soon will we see HDMI 2.1 interfaces and cables? Well, considering it took almost 3 years for version 2.0 to achieve any significant presence in commercial AV, I’d say maybe a year from now at the earliest…and perhaps not until 2019 in any quantity.

By then, a good deal of the industry may have already shifted to AV-over-IP for the bulk of its signal switching and distribution, using simple format conversion at the display end. And we still have to see who is going to adopt on DisplayPort 1.3/1.4, still a “no-royalty” interface that can hit 32 Gb/s and supports all the forward-looking necessities (Type-C Alternate Mode, DSC, HDR).

Gentlemen, start your engines…