HDBaseT Interoperability Follies

Welcome back to any AV followers who faded away last month while I was posting all fiction all the time. The stories and poems won't entirely go away but we'll start moving into a little better balance between pixels and ink for the nonce. Today I'd like to share a moment to discuss everyone's  favorite transport mechanism, HDBaseT.

For those not in the know, the HDBaseT alliance have defined HDBaseT as a technology for transport of video, audio, power, ethernet, and control over standard category cable. As a point-to-point (as opposed to routable) signals, HDBaseT cannot be routed with standard network switches. With offerings branded by major techm manufacturers (ie, Crestron's "Digital Media" and AMX "Enova" it has become a defacto standard for commercial systems.

Or has it?

The idea of a "standard" is that it should be manufacturer-agnostic. The HDMI output on a Sony Blu-ray player, for example, will work on the input of a Sharp LCD panel as well as it would on a Sony. Is that the case with HDBaseT? Is it, in other words, really a "standard"? The HDBaseT website does boast, in a large banner, that it is "The standard of the future", but the remainder of their text is much more cautious, referring to HDBaseT "technology" or "specifications". Can one grab an HDBaseT transmitter from one manufacturer and receiver from another and expect them  to work together? In an ideal world, the answer would be yes. Those of us who have wrestled with HDCP, EDID, or other HDMI-inspired headaches knows one thing for sure: this is not an ideal world.

For the sake of my own curiosity I tried a little experiment. I had access to transmitters from three major manufacturers: Crestron Digital Media, AMX DXLink, and Extron XTP. The latter is not, to the best of my knowledge, HDBaseT certified, so I'd not expect interoperability from it. The others are, so I would. Is that what happened? Not quite.

The AMX receiver gave me a "green screen of doom" when I tried to connect the Crestron or Extron transmitter to it. This is apparently an HDCP handshake error (as opposed to HDCP noncompliance, which would give a red screen of doom. Doom is the consistent part). This possibly has to do with how AMX handles HDCP authentication, which treats the receiver as a source rather than a repeater. This is nifty in that it bypasses the key limit in some sources (in other words you can run a single Blu-ray player to as many displays as you have outputs for, regardless of its key limit), but might make the receiver more picky in what it looks for from the source side.

This was a fairly disappointing result in that it left the non-HDBaseT certified Extron XTP as my only other receiver. IT might not be "certified", but it does use the same technology as HDBaseT transport solutions. Somewhat to my surprise the Crestron and AMX transmitters both sent HDCP protected content to the Extron XTP receiver. So much for certification.

What does this mean in practical terms? Not all that much. What it highlights is just how similar these devices are. Even in terms of form-factor you get a great deal of similarity between product lines; everyone has a standalone receiver about an inch or so deep to fit behind a flatpanel (or in a wall box), a similarly shaped standalone transmitter, a two-gang wall-mount transmitter,  and modular matrix frames sized from 8x8 up to 32x32 or larger. There's no real practical reason to step out of a single manufacturer's ecosystem other than to prove that you can. Now that we've done so, even that is gone.

A selection of transmitters and receivers

So how does one choose? We're the same place we were back when we did "Switcher-Wars" last year. Do you need Crestron's full audio and USB breakaway? AMX's smaller form-factor and better energy efficiency? Does an end-user with limited programming expertise want to be able to make equipment substitutions and other programming changes through Extron's Global Configurator or AMX's Rapid Project Maker? Is there an existing implementation of a remote-control and asset management system (Crestron Fusion, AMX RMS, Extron Global Viewer) into which you'd like your new system to tie? We've reached a point at which not only are the differences more subtle, but many of them won't even appear on a spec sheet.

The real take away here - for those who didn't realize it already - is confirmation  that the technology is very much the same. In fact, it's the same to the point that if one files off the serial numbers one would have a hard time even telling one apart from another. What this really means is that the best manufacturers aren't just selling the technology; they're selling a solution, including an ecosystem to fit around it and the thought they put in to some of the details that one might miss on a spec sheet.

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The HDBaseT adventure continues

HDBaseT has been around for a few years now and, to the likely disappointment of the initial HDBaseT consortium, appears to have settled into a role as a midpoint; it still isn't a format likely to be seen as the input or output to a device, but is widely used in distribution and switching. I had the chance to ponder and discuss this with some of my colleagues in the commercial AV industry at AMX's showroom during the two-day certification class for their HDBaseT system: Enova. It's striking to see how far this technology has come, and how different manufacturers can take the same underlying chip set to create very different-feeling solutions.
The idea for HDBaseT is a grand one; to have one and only one cable connected to each display.  That cable, a standard network cable with standard RJ45 connectors, would carry uncompressed high-definition video, audio, control, and even power. Yes, they expect to power your display via the same Cat5 jumper that carries everything else. One cable in this case literally means one cable. In real world applications, that isn't what's happened. For one thing, native HDBaseT inputs and outputs. Even if manufacturers want to use this kind of system, even mid-size displays in the 50 to 65 inch range outdraw HDBaseT's upper power limit by an approximate factor of 10. So, like a phone company  running fiber to the curb before converting to old-fashioned copper, we're left with easily-pulled Cat5e cables to a receiver-box giving way to good old HDMI cables for the proverbial last mile. We're not quite where we someday can be, but it's an improvement. Crestron's Digital Media is an HDBaseT solution, as is Extron's XTP and AMX's DXLink, the heart of its Enova solutions.
How do solutions compare? Not only does Enova have a different feel from Crestron, but AMX's DVX (a family of all-in-one presentation switchers) behaves differently from their DGX (more conventional digital matrix switchers). One thing I hadn't known - because I'm not in the habit of removing the case on expensive pieces of electronics unless I have to - is that while it looks like one seemless piece of hardware, the DVX is, in fact, card-based. My notes include a glimpse at its innards, highlighting the HDMI input cart swappable with a DXLink card for another model. It's a clever design philosophy which allows AMX to inexpensively and reliably use one platform to produce a suite of units with slightly different features. 
So how does Enova compare to Digital Media? At a glance they're similar; each has a presentation-switcher with built-in control processor, audio mixing, and an amplifier. Each line boasts a modular matrix switch capable of handling different video formats. Each has a series of Cat5 transmitters and receivers. Each handles HDCP key authentication, effectively eliminating any risk of running out of keys in large systems. Looking a bit closer, one sees differences.
The first distinction - of  which AMX is justifiably proud - is that each output on an Enova system has a built-in "smart-scaler" which reads the  EDID from a display and scales the image to fit. This means that even in a large system with many different displays each device will get an image at its native resolution. Their contention is that other practices, like choosing "best common", not only leave adjusting resolution to a device's onboard scaler, but fails to take advantage of the higher resolution in the largest display in a system. It adds a certain measure of cost, but AMX feels that they give value for it.
The second distinction is that each AMX matrix switch has a control processor built into it. This makes for a neater and more compact installation, but isn't a tremendous improvement over the inclusion of a standalone processor, and burying it in the switch gives you the new problem of having no local control ports. Unless everything in your system has IP control, you'll have to build out the system with varying add-ons. In all fairness, AMX has a nice suite of IP-based control port expansion modules, and seems to have a philosophy of preferentially using IP-based controls.

What about the distinction within the Enova line? At Enova training in AMX's New York showroom we got a demonstration of both the DVX presentation switcher and DGX matrix switcher.  The performance in switching speed is markedly different, with the DVX switching, I would estimate, twice as fast as its cousin. The difference was explained as a result of different engineering teams working on the two devices, and upcoming firmware updates to let the DGX catch up were hinted at. (it was further explained that the slower switch time - one and a half to two seconds - was a result of the switcher dropping sync when it changed sources. It is very interesting how the same hardware can have different performance given different firmware.
What about venerable switching manufacturer Extron? I don't have much to say about their XTP line; certainly until they start shipping the Cat5 input and output cards for their switcher, they can't be said to have a real solution available. Even given that, they're still behind the curve in not having a DMPS300/DVX style presentation switcher available. They have added power injectors to their XTP line, but it is, at the very least, unclear that these would work with other HDBaseT solutions.
Long story short? It's an exciting time in the commercial AV industry as we finally seem to have the hardware, software, and expertise to start making digital video work closer to the way it should; many of these solutions are, if anything, easier to use and more flexible than old analog solutions.

A side note: my adventure at AVI-SPL has come to an end, so I am open to new opportunities in the AV field. Anyone reading this is welcome to comment or drop me a line with any openings in the New York metropolitan area.

Stay tuned for a book review later this week.

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