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Are Active (HDMI) Cables the Future?

by June 30, 2011
Active Cables - Here to Stay?

Active Cables - Here to Stay?

With a recent tear-down by ArsTechnica on the new Thunderbolt cable Apple is selling for $50, we're starting to wonder if active cabling is the future of all A/V electronics. With a desire by content providers to keep everything digital and protected in the realm of high definition television, and A/V manufacturers scrambling to provide features that will generate more 'oohs' and 'awes', it's a wonder if we aren't digging a hole.

A great big hole.

It all started with HDMI. When it began, it was buggy. but sending 1080p over multiple copper wires was still feasible. As the HDMI Licensing Group began to feel pressure from organizations and formats such as VESA's DisplayPort, however, the race began. New features, like Ethernet support and Audio Return Channel (ARC) began to emerge, as did support for uncompressed multi-channel audio in multiple native formats and, most devestatingly in our opinion, ultra-high video resolutions.

Now, I'm all for high resolution, but is the consumer market really in need of 4K × 2K (3840×2160p24/25/30Hz and 4096×2160p/24Hz) resolutions? Can't digital theaters use something more demanding and consumers be left with something that's actually manageable?

This week, ArsTechnica's tear down revealed that the new Thunderbolt cable form Apple costs $50 largely because it is active. There are two Gennum GN2033 Thunderbolt Transceivers embedded within the cable at both ends. And this isn't the first time we've seen active cabling. When DVIGear began to make its 22 gauge Blue Super High Resolution HDMI cables we immediately wondered how many consumers would want to deal with cables that looked like they were meant to be used as towing harnesses rather than A/V interconnects. But that's the problem with ultra high resolution, and now HDMI 1.4a and Category 2 specifications... you need to support an inordinate amount of bandwidth over long distances.

We've espoused What's Wrong with HDMI before, but we're now wondering if we've just hit a wall. If, from here on out, even shorter runs of HDMI are going to more or less have the requirements of being active in order to support the bandwidth needed for future technology and throughput.

That certainly seems to be the writing on the wall. And it's going to add costs to cables that are already expensive if you don't know where to shop. If Big Box stores can charge monstrous prices on passive cables, can you imagine what will happen when they all go active?

In order to avoid cables that are ridiculously thick and heavy, manufacturers are more consistently turning to active HDMI cable technology. But it has to be done correctly. Even HDMI argues that it's a recommendation (that's an understatement!) for longer runs and that relying on the built-in 5V line isn't the most reliable way to do it (again, yet another short-sighted failing of the HDMI spec). The trouble is, many of these solutions require an external device or at least a power source - that's another black box you need to add to your install JUST TO RUN A CABLE FROM ONE PLACE TO ANOTHER. In their own words:

Using active electronics to boost and clean up the signal can effectively double the range of a standard twisted-copper HDMI cable. Cable runs of up to 30 meters are the norm for this type of solution, which may be deployed as either a standalone signal management device, i.e., a repeater or booster box, or incorporated into the manufacture of the cable itself. Boxes are available in many configurations, usually incorporating both booster and equalization functions, and may also serve as repeaters or switchers. Active cables, on the other hand, embed the signal-enhancement electronics in the cable itself, with chips embedded in the connector housings. They are unidirectional, using different modules at the transmit and receive ends of the cable. All the technologies in this category require external power.

Beware products that draw power from the +5V power line. Although these may work in certain applications, different components draw varying amount of power from that line to communicate with each other. A cable that draws power from the HDMI cable may fail when components and the active components in the cable or external booster are all drawing from the same source.

So what can we expect? A switch to all-active is the spec keeps changing to accommodate more and more things most people don't use in their home theaters. If HDMI continues to increase resolution capabilities and adding features - and electronics manufacturers keep supporting them - then those copper cables you have simply aren't going to cut it in future products.

Fortunately, electronics keep shrinking. That means more and more electronics can fit into smaller spaces. One of the things we hate about embedded electronics is that it often makes the connector heavier, longer, and more difficult to manage. Since HDMI doesn't inherently have a locking mechanism, connectors are already prone to fail. Adding more weight certainly doesn't improve things. Smaller chips will yield smaller connectors - and this is a good thing.

The problem of power is also still an issue. Since the 5V available over HDMI is often not enough to power the active electronics - especially over longer distances, external power seems to be a constant requirement. We're not sure how this will be improved over time, but that's the current elephant in the living room, and it's a big one. Nobody wants to plug HDMI into their receiver and then supply it power just to get to the projector.

It would also be great for the industry to realize that there is a lot of work left to do in terms of 1080p, and that expanding to higher resolutions is inappropriate for the consumer market. Separating the commercial and consumer markets might actually make a lot of sense and keep needless advances from trickling into the spec and applications where it's just not needed.

What do you think? Are you pleased with the current state of A/V and HDMI cabling? Do you want to see more active electronics coming to the consumer market? Or do you think that the added expense in cables is going to make it harder for consumers to get what they need and wire up their rooms - especially over longer distances.


BoredSysAdmin posts on July 20, 2011 09:16
jotham, post: 817707
As a computer programmer I vastly prefer network approaches like Cat-5/6 over proprietary or new cabling standards. That said, I think the reason that stuff like HDMI/Display Port/Thunderbolt/Firewire have their place is because of latency. Network protocols are great for transmitting data asap but timing is fluid and can't be counted on. Add-ons to the protocol like QOS(quality of service) attempt to lower the latency for apps like VOIP and video conferencing but they're not perfect.

In summation, it's not all about the bandwidth, it's also about the timing. Think about how we tweak our projectors to get the lip sync correct, or play video games successfully.

Not everything is about A/V. Thunderbolt has it's place but nowhere near our a/v racks for the near future. I doubt that active tech is necessary for HDMI 4a stuff. I could see it being mandatory for 4K projectors but at that point, we are spending a ton on the display device and the cable will be the least of our worries.

One interesting (to me) thing about the Ars Technica article is the idea that the active chips mean that different transports like optical could be used in the cable with no change in connector. Kind of an optical balun built into the spec. That's pretty cool. I envision an active cable that allows a slim hdmi-like cable to reach 50 ft with complete compatibility.

I was just reading on SMPTE 424M standard - the “future” for video broadcasters - ability to transfer upto 3Gpbs on single sdi link - Read single coax cable and then I found this article - https://www.smpte.org/events/smpte_annual_tech/schedule/02tuespm2/

Like they say - from the horse mouth - Regular 10 Gbps Ethernet is already finding it's way into broadcast studios….

As with may other developments in video technologies over the past decade, the solution to this quandary comes from IT infrastructures, such as 10Gigabit Ethernet. This technology is ideal from several perspectives, including capacity, cost, and native support for high-speed file transfer. The question becomes: Is it possible to develop a smooth, incremental migration path from current dedicated systems to a common 10Gibt Ethernet backbone for all broadcaster services? The answer is yes, as will be shown in this presentation. Already, multiple vendors are developing products to map a variety of high-performance video and audio signals into Ethernet infrastructure.

I just hope just this will find it's way into consumer market sooner than later.
demoncamber posts on July 10, 2011 13:07
That's crazy, I love technology
rjplummer posts on July 05, 2011 11:28
I hope active cables aren't necessary

USB 3.0 supports 5 Gb/s without active cables. Granted that's not isochronous and the cable runs are slightly shorter, but USB3 is already 3 years old so it seems like the industry should be able to come up with something better
rjplummer posts on July 05, 2011 11:17
Higher resolution desired?

I'm surprised nobody has yet replied to:

Now, I'm all for high resolution, but is the consumer market really in need of 4K × 2K (3840×2160p24/25/30Hz and 4096×2160p/24Hz) resolutions? Can't digital theaters use something more demanding and consumers be left with something that's actually manageable?

I personally look forward to higher resolution. There should be fewer visible artifacts and better motion and color.
Ajswanson posts on July 01, 2011 19:28
Cart before the horse?

This is an interesting topic. I remember in the 90s when Microsoft planned to make the next version of Office an online only version that you essentially leased. There was a big uproar but here we are on 2011 wanting The Cloud. I think much is the same here. The question isn't will we have it, but when and what technology will be so compelling that we accept the trappings that go with it?

As a manufacturer of HDMI cables, we find that people want (and deserve for that matter) good quality but don't want a high price tag. As a consumer myself, I always get upset when I buy a new piece of equipment only to find out I need to spend another $xx on accessories and cables. 3D is still pretty nascent and has a lot to work out before it can really be successful. Other technologies on the horizon are even further out. I dont think there is a large need for active HDMI right now. But when the right technology comes along, it wont be such a big deal.

And the same will be true of all interconnecting technologies, there will be the companies that sell you much more than you need for much more than you should afford, and there will be companies like Volo, that focus on getting great quality and great customer service at a great price. *We are committed to supporting the technologies as they become available and come into more frequent use, and also to making sure that the customer is getting what they NEED, not what they are SOLD.
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Clint Deboer was terminated from Audioholics for misconduct on April 4th, 2014. He no longer represents Audioholics in any fashion.

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