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Why 2 Short HDMI Cables Yield Different Results
This is not new, we’ve been following specification rules since the invention of the wheel, so why has it now taken such a toll?
In our experience, some manufacturers have shown a lack of competency in making HDMI products right the first time and continuing that over the products’ life span. It is absolutely false that all cables are the same, even at short lengths.
DPL Labs is more than just a certification company. It offers additional services that manufacturers, vendors, retail operations and even distribution firms look deep into when they are either buying or building products to verify that the integrity is what they were promised.
These are called PDRs (Provisional Design Reviews). This service provides testing and examination of cables, Blu-ray players, switchers, A/V receivers and baluns from many firms.
Here’s an example: Two relatively inexpensive 1-meter cables came in for testing. They were being used with cable TV, so not such a big deal. When tested with one TV, however, only one of the cables worked, but with another TV they both worked. They were from two different manufacturers, and we were supplied two of each cable.
Upon testing and inspection we found that the integrity of the serial interface used to communicate the HDCP and EDID on one cable proved to be substantially slower in response compared to another cable that did work. By using different loads we were able to see, by way of an oscilloscope, that the rise times of these serial channels were very different. In an effort to expose why, we dissected each product.
Neither cable supported a shielded wrap around the video channels … that’s a first no-no. They both don’t twist the serial wires … sort of a no-no. However, the one that failed used a very thin solid gauge wire size for the HDCP/EDID channel compared with the cable that worked. The HDCP/EDID wires within the cable that failed are at least two times smaller in diameter than the one that worked. That smaller diameter HDMI cable was easy to bend and connect, but the consequences were dire, because the installer had no other cables to replace these, and it took yet another trip to the site to clear it all up.
Could the cable company still have made a thinner diameter cable with enough integrity for it to work with more devices? Yes! All it had to do was determine the intended cable length and predict, to some standard, the gauge of wires needed to support the video, supply voltage and the HDCP/EDID lines. Of course, the cable would not be the best cable in the world, but it sure would have had a better chance by decreasing the gauge of the video wires and increasing the gauge to the HDCP/EDID wires. When you make a product that sells for cheap, it becomes a give-and-take.
This example is not to say you must go out and purchase the most expensive cable either.
So what do you do? Buy from the people that can explain their differences with factual data, and not from the jacket style, color or price alone. Remember, one return visit can cost you time, money and grief.
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22 Comments (displayed in order by date/time)
Good info, but I’d like to see the brands you tried named and the TV / Cable box manufacturer / model used. Be honest here the TV / cable box can cause almost as much problem as the cables.
I’d also like to see this tried with different major brands (probably have to try several levels but lets just start with the entry level). Again need to say which brands pass / failed what test. The tests need to include 1080i and 1080p (plus 3D for both).
Also please place some major blame on the HDMI spec / org it’s self. Why in the world would they allow new cables that don’t have the bandwidth to pass 1080p let alone 3D be available for HDMI 1.4 spec???
The HDMI community needs to do a much better job a providing a robust environment. HDMI is (has been) the joke of the tech industry for a long time.
Want a spec that doesn’t work… ->> HDMI 1.anything
Suggestions for HDMI 2.0: make it a Ethernet CAT6 cable and make it WORK right the first time.
I totally agree with Carl. I find it very annoying when someone writes an article about a bad product and fails to name that product. I understand there may be some issues with this, but if you contacted the manufacturer with your problems first and they didn’t fix the problem then they should be called out on their bad products. Otherwise I have no idea if this article is true or just someones opinion with no facts.
I agree, state the facts otherwise it is just conjecture…
HDBaseT is your HDMI on CAT-5 or 6. This is a much better technology than HDMI. Extron and Crestron are already using it. Check it out at HDBaseT.org
Although I agree with the statements above, I think the moral of the story is carry extra decent HDMI cables with you when you do any job and charge the client for it.
Also remember not all cables are created equal.
My cable cost more because I warranty my installation. You want me to use your cheap/free cable, fine no warranty, you can pay later to fix it.
Excellent and informative article. Thanks Jeff.
Russ,
Just a technicality – HDBaseT is not a replacement for HDMI. It is a way to extend the HDMI signals through a single 4-twisted pair cable. It currently still requires connections through HDMI chipsets on both the transmitter and receiver ends.
=D-
More testement to the case that HDMI is not a great technology by any means.
>More testement to the case that HDMI is not a great technology by any means.
I know right? My abacus always works, but my computer freezes up all the time! Definitely an inferior technology.
Back on the topic at hand, it would be nice to know the make/model of the cables used. Data is data, no need for political correctness here.
Lets also be clear about the failure mode as well. Bad HDMI cables either a) pass no signal, b) cause image breakup , and c) cause sparkles in the image.
Bad cables don’t cause poor blacks, de-saturated colors, additional noise in the image.
Yet many voodoo cable manufactures and their dealers still scam the public with this mis-information.
@ Russ.
I’m with you there. I love pulling a run of CAT 5 to get video out to a remote monitor, then hang a box off the end with a power supply to convert it to an 18” HDMI cable going into the back of the TV. I feel a George Carlin joke coming on at that point.
HDMI is a over engineered interface and was designed to appease the sky is falling Hollywood studios.
With BR and DVD’s being copied without their DRM and Anti-Copy protections CAT5 and Component video work just fine for SOME reason and no unreasonable distance limitations 
No Andy your right they don’t cause the poor-black levels and such things you describe they do how ever improve upon these things especially noticeable on better TV’s, and guarantee they WORK at any length made or sold.
You are scamming your clients by not offering them a better option.
Also take some time and A/B a better made cable for audio and hear the difference yourself.
I am not an installer. I am a graduate EE working in the ollywood entertainment business. So let’s dispense with the voodoo cable stuff.
If an HDMI cable produces a stable image free of sparkles, that’s as good as it gets. A more expensive cable will not provide ANY additional image improvement.
Now do you want to explain just how a better HDMI cable improves image quality other than the cliff effect where sparkles come in
Jeff,
You bring up a very interesting consideration. My assumption is that most manufacturers probably order spools of wire and use that same wire type for all lengths of HDMI cables. It makes a lot more sense if they were to look at the different wire characteristics required for specific cable lengths. They could assess the appropriate (and maybe less expensive) electrical characteristics (possibly thinner and more flexible) for shorter lengths and incorporate a more robust wire with different electrical characteristics for longer lengths. I wonder how many vendors actually take that into account. That would be a good question to ask when evaluating products.
Most cable vendors focus on the TMDS lines and the bandwidth they support. As we know, many problems in the field actually are related directly to the HDCP handshaking and potentially EEDID errors. As we put more reliance on the EEDID data and the constant HDCP key updates coming across the cables, the data reliability on these lines is increasingly becoming more important. Thanks for your insights.
=D-
Derek R. Flickinger
Interactive Homes, Inc.