HDBaseT… a power of good
HDBaseT technology offers many features to make installers’ lives easier, but there may be some ‘gotchas’. David Meyer explores the details and the certification process.
When you consider that HDMI is a mere subset of HDBaseT – which offers far more features and is inherently more complex – getting it right is paramount.
In its first few years, HDBaseT was pretty much limited to point-to-point extenders, but now the applications are much broader. There are AV receivers with direct HDBaseT outputs, projectors with HDBaseT inputs, HDMI matrix switchers with HDBaseT outputs to pair with far-end receivers, and more.
The aim of the HDBaseT Alliance is to manage a Standard that would allow transmitters and receivers of mixed brands, whether integrated or stand alone, to work seamlessly together.
Imagine taking just the transmitter from an extender pair and using it to connect directly to the HDBaseT input (receiver) of a projector.
However, if that extender pair has DC power input at one side only and doesn’t manage power over the cable in a compliant manner, it could blow the projector up.
So how do we ensure that all devices will play well together? The answer is certification, as has now been mandated by the HDBaseT Alliance. It will take time for the market to conform, so in the meantime it’s best to learn what to look out for.
The HDBaseT Alliance
The Alliance is an international organisation whose function is to standardise and promote HDBaseT technology.
Its founders include Valens (inventor of HDBaseT and provider of chipsets), LG Electronics, Samsung Electronics and Sony Pictures Entertainment.
The organisation was founded in 2010, and its administration is based in the US state of Oregon. It has more than 100 member companies.
The HDBaseT 1.0 specification, released in the same year, is the basis for certification.
The five key features of HDBaseT are encompassed in the ‘5-Play’ trademark – video, audio, power, Ethernet and control.
Support for video and audio (aka HDMI) are compulsory, and the other three are optional. A certified product has been rigorously tested for the features in question to operate with other products, irrespective of brand.
Once certified, a product can carry the HDBaseT logo, although this is not compulsory. More definitively, it will appear on the certified products list at http://hdbaset.org/products_list
The list is growing, and from next year it will be an increasingly important reference for installers. As it gains in maturity, installers will be reluctant to use unlisted products. After all, installers must deal with the repercussions if anything goes wrong, so it is in their best interests to check for certification.
As it stands, there are two classes of HDBaseT product: A and B.
Class A is the full original configuration, which can support the entire 5-Play feature set plus 1080p and 2160p (4K) to 100m over a high-quality LAN cable.
Current Class A products use Valens VS100 chipsets.
Class B is more commonly known as HDBaseTLite. This can support 1080p up to about 70m, and 2160p to about 40m. It supports control and power protocols as well, but unlike Class A it cannot support Ethernet.
Current Class B products utilise Valens VS010 chipsets.
Video and audio
Support for uncompressed video and audio are compulsory minimum requirements for any product to be HDBaseT certified.
Video formats supported are basically all those as defined in the HDMI 1.4 specification, from 480i up to 2160p/30 (4K). Some video formats of HDMI 2.0 can also be supported over Category-x cable, but only those with an aggregate data rate less than 10Gbps. This includes 2160p/60 8-bit 4:2:0, but nothing higher.
As for audio, there’s a lot less bandwidth to consider, so HDBaseT could (at least in theory) support virtually all audio formats as defined by HDMI 1.4 & 2.0.
This includes 3D audio up to 30.2 channels of either 192kHz 24-bit resolution or 1-bit DSD, as well as the multitude of lossy and lossless surround formats – 5.1, 7.1, etc.
Minimum support of PCM 2.0 is required for certification.
This is one of the most important aspects of HDBaseT for an installer to understand, as it could cause extensive damage if the wrong products are mixed.
The main reason for certification of products is to ensure interoperability of transmitters (Tx) and receivers (Rx) across brands and product types. This is irrespective of whether a manufacturer claims that an extender is designed to be used only as a captive pair (or at least everyone assumes so).
Certification tests each end on a stand-alone basis to ensure that they could be split and used independently at the installer’s discretion.
The 5V line inside HDMI only allows up to 55mA current draw – a mere 0.275W of power. A typical HDBaseT pair requires about 20W, so external power is essential for HDBaseT products.
The next question is whether to power at both ends of an extender pair. Single-ended is always more convenient from an installer’s point of view, but it means sending power over the cable. Is that safe? Well, that depends on how it is done.
So it comes down to two considerations: is power being sent over the cable, typically identifiable by the presence of a single external power supply for the pair, and is that power being sent in a controlled way?
True PoH means there is a handshake between the two ends, wherein no power goes over the cable unless this has been ‘negotiated’.
Unfortunately, you can’t always rely on information provided by a manufacturer. It is easy to label a product as having PoH, but that doesn’t make it true – it may be PoC.
The only way to know for sure whether a product supports PoH is to check the aforementioned certified products webpage. Listings look something like the accompanying graphic.
If an extender pair has only one power supply but is not certified for PoH, then just assume that power may be present in the cable.
Another requirement of HDBaseT products is DC isolation, which in theory should prevent damage to third-party devices. However, the first you may know of it is when a projector or AV receiver HDBaseT port blows up.
Any product that uses separate external power at both ends is not using any form of power over cable. Certification without PoH should then be simple, and third-party devices should not be at risk.
HDBaseT Class A can support 100Mbps Ethernet, (aka 100BaseT).
This is where HDBaseT can sometimes get confusing. It wears a name in the xBaseT family, it uses the same local area network (LAN) cable for the link, internally uses protocols like PoE and offers Ethernet support.
But it is not compatible with regular networks. The Alliance tells us that future iterations will include HDBaseT exclusive independent network capabilities.
The protocols supported in HDBaseT are HDMI Consumer Electronics Control (including 2.0), RS232 (typically simple Tx/Rx type) and infra-red.
As HDBaseT is based on LAN technology, it can also support captive internet protocol signalling
These features are tested as part of product certification, and those that conform are listed as ‘Features’. Each feature should be interoperable with other products and brands that list the equivalent feature, even if the physical interface (eg: connector and pinouts) varies.
If a product seems to have these features but they are not on the certified products list, they are non-standard in configuration and cannot be assumed to work across other products. Non-compliant power is the only feature with the potential to block basic certification, as it can be dangerous.
We can’t talk about HDBaseT without touching on the importance of LAN/Cat-x cable quality.
In its early days, HDBaseT was promoted as a technology that could transport 4K video over 100m of Cat 5e. These days the view is somewhat more pragmatic, as not all cables are created equal (far from it).
Cat 5e at only 100MHz is acceptable as long as it is of decent quality, but realistically it won’t achieve the lengths originally suggested.
The top end of HDMI 1.4 runs at a staggering 1.485GHz, and even with PAM-16 (the modulation technique that HDBaseT uses), Cat 5e is still a stretch.
Cat 6 unshielded twisted pair (250MHz) is typically the go-to cable in 2014, but screened or shielded cable is better again. Cat 6a (500MHz) is the best, and generally better for most installers than even Cat 7, as you can still use 8P8C connectors (better known as RJ45).
Whichever you choose, copper-based LAN cable has a ‘hard ceiling’ at 10Gbps aggregate data rate. HDMI 2.0 features such as 2160p/60 eight-bit 4:2:0 can still fit through this pipe, but anything higher than that and it’s all over for copper LAN cable and HDBaseT.
Combine 60 frames per second and 10-bit or 12-bit colour with 4:2:0 or 4:2:2 chroma subsampling, and the future points to fibre optics.
HDBaseT over fibre
As mentioned, HDBaseT started with the release of the VS100 chipsets in 2009, and later the detuned VS010 chips as a more economical solution.
At that stage it was all about cable length and whether it supported Ethernet. But since then we’ve had the release of HDMI 2.0 and newly defined speeds up to 18Gbps, as well as the broadening of USB as a ubiquitous Standard for more than just file transfer.
The next generation of HDBaseT addresses these points, and then some. The second generation is trademarked Colligo.
The new VS2000 5-Play chip is a step up from the VS100. It’s more efficient, and paves the way for future HDBaseT 2.0 networking capabilities.
The VS2310 is better again, as it adds support for USB 2.0 host and device interfaces, as well as taking the inevitable step towards fibre optics in place of copper-based LAN cable.
The way HDBaseT works in principle is to serialise all incoming streams – video, audio, control and Ethernet – then modulate this for transmission using PAM-16.
One of the outstanding features of the VS2310 is its ability to output the raw stream to couple with its sister chip, the VS2311, to deliver through multi-mode fibre (MMF) or single-mode fibre (SMF) “over any imaginable distance”.
For any installer wanting to pre-wire for the most foreseeable future-proofing, the best thing will be to run two lengths of raw MMF of at least OM3 clarity. No need to terminate yet, just run the cable.
You may not need two cables when the time comes, but considering that the effort is the same and the cost is relatively low, it’s worth doing.
MMF is fine for lengths up to about 300m, whereas SMF is required for extra-long runs, that is, kilometres.
Bandwidth and HDCP
A final recommendation is to keep in mind that the bandwidth of any system will be limited to its ‘narrowest’ point.
In the case of a matrix switch, this may be the bandwidth of the HDMI switching stage. If it’s only 225MHz transition minimised differential signalling (TMDS) clock speed then this limitation will flow through to the HDBaseT stage, limiting it to 1080p/60 at best.
Similarly HDBaseT is completely agnostic when it comes to high-bandwidth digital content protection (HDCP), particularly the concerns that are brewing around HDCP 2.2.
In a pass-through arrangement, HDBaseT has no problem with this. However, any product that decodes HDMI might have issues, such as those that offer video processing and scaling, audio breakout, etc. Just learn to ask the right questions of your vendors.
Every AV installer has probably used HDBaseT enabled products by now, in various forms and configurations.
Like everything in our industry, HDBaseT continues to evolve, and I recommend that you don’t take it for granted.
Installers generally are held responsible when things go wrong, or they have to put in non-billable troubleshooting hours. As for having an expensive device blow up on site – let’s not go there.
The HDBaseT Alliance exists to steer the technology and ensure that products fulfil expectations. No company is allowed to sell HDBaseT enabled products without being an HDBaseT Alliance member, and from next year all products must be certified to ensure safe interoperability.
When the capabilities of HDBaseT 2.0 are fully realised, this will become more important than ever as products become networked.
As an industry we need to ensure video and audio formats work seamlessly, control commands such as infra-red and RS232 work across brands, and there’s no stray DC power across cables and systems.
This new mandate for certification will inevitably create a backlog of demand at certification centres, but by the second quarter of 2015 you should be using only HDBaseT products that are listed as certified.
In HDBaseT utopia it will all just work!