HDMI 2.1: Much Ado About Nothing?

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) mandate 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., 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.

From left to right, David Meyer, Rob Tobias, Paul Gagnon and Scott Klienler. Image:P Putman

To drive this point home, IHS analyst Paul Gagnon showed numbers that forecast 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 every 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. – Pete Putman

Analyst Comment

Regular readers with long memories might remember that the ill-fated Super MHL specification was shown running 8K 120Hz back in 2005! (SuperMHL Silicon Announced). (BR)