As if it's not bad enough with all of this HDMI "stuff" that potential purchasers also need to worry about long HDMI Kabel runs. Dads and moms of analog video the reliability of signal transmission over long kabel lengths was never a problem but in the first days of HDMI and DVI we heard rumors of consumers encountering problems over relatively short runs but everything has improved over time but the actual length you can run long HDMI Kabels over continues to be an industry hot potato.
HDMI Kabel Test
Let's look at the latest HDMI specification to have an answer to the question. Every kabel needs to be tested by the HDMI authorized test centers before they are able to gain compliance certification. These certificates may be used as some kind of unofficial guide for workable kabel lengths. There are a variety of kabel that are compliant at lengths over 10 meters and there are some that have passed the testing as much as 13.0 meters, so they are proven not to degrade the signal beyond a place stipulated by the accreditors. A great piece of advice is to buy certified kabel using the latest specification, at this time HDMI is at 1.3b, but 1.3 and 1.3a are also acceptable, as the test protocols these kabel have to pass to receive the standard are more stringent than for prior specification, say 1.1 or 1.2.
Before you are tempted to buy anything over 13.0 meters (45-foot), they are available and being marketed as compliant, it may be wise to ask to see a copy of the certification because at this present time the size of 13.0 meters (45-foot) may be the longest none boosted (amplified) kabel that I have seen with the correct certification.
That said, there are available HDMI Kabels which are classed as active designed to use powered amplifiers to enhance the signal enabling longer runs of kabel to be used. An EQ unit can also be used on these active kabel which examines lost high frequency data and then compensates for this. Scalping strategies do work, but with no straight answers concerning actual effective length, the additional costs involved and also the extra possibility of signal delivery failure from the inclusion of extra components it might be a step to far for your home entertainment system and best left to commercial applications.
But stop worrying if you need to run longer lengths of kabel. Just bear in mind the HDMI spec is their so you can be confident that whenever you build your system the compliant signal (source) could be connected to a compliant unit which in turn can then be connected to another using compliant kabel and when you switch everything onto it will work. As with all specification, inside will be built some leeway - over engineered - so the source signal sent to the HD enabled equipment is better than is needed for that equipment to function as mentioned. This gives you a handful of options, options that don't fit into the specification so are not guaranteed to work as in the example above, but options that have been proven to work and don't have the added costs of amplification.
There are connectors available which, although not compliant, will do a job and of course there are the over length (for compliance) kabel. If you are to go this way it's worth bearing in mind that the higher the bit rate your HD enabled equipment is pulling the less chance of success you have. You also need to remember that this also applies to long chains, HDTV to Blu-ray or home entertainment connected to the internet streaming video on demand at 1080p will be pushing longer kabel lengths, those on the compliant length, to it's limits. But for 480p, 720p or 1080i they may work fine. Do you see just how hit and miss this can be.
Now take into account future advances, that you should if you are putting these kabel in walls etc., as if you are running about the limits of the kabel this could stop you upgrading. Take where we are at present. 1080p is the latest resolution for HDTV. Not that long ago 480p was the norm, then came 720p and 1080i which utilizes a bit rate almost 3 times that of standard 480p. Then along came 1080p that doubles the part rate consumption of 1080i and 720p. Now we get up on the edge of 3D TV, 16 bit color and 1460p (and above), 16 bit color alone will double the amount required bit rate for current standard resolutions, so you see where this could go. One more important point to consider when deciding whether or not to go long or otherwise. It is a fact that on short kabel, the ones from 2-3 meter (6-10-foot) length, the quality matters less. A kabel costing a few bucks will perform just as good as one costing tens of dollars, but when entering the realms of none compliance quality matters far more. Generally speaking, the lower quality the kabel is then the lower the effective working distance is going to be when depth of color or picture resolution increases.
So lets unravel what's been postulated regarding long HDMI Kabels and their reliability. For the lengths which are HDMI compliant, those lengths up to about 13 meters (45-foot), their me is pretty much guaranteed, even if you're using the cheaper options, for 480p, 720p, 1080i and - even when not as consistently reliable - 1080p so go on and use them with confidence. The same goes for those shorter kabel of 1-3 meters (3-10-foot) lengths, though care should taken when utilizing them in long signal chains because they could become unreliable. Cheaper options from the longest HDMI compliant kabel focusing on the limits of it's performance capabilities may struggle in the 1460p, 16 bit color future and their use needs to be questioned if their installation is behind ceilings or walls because the additional cost of a more expensive kabel may be less than a complete re-install in the (not to distant) future. The use of over compliant length HDMI Kabels must be linked to all the factors mentioned previously but with the rider the best method of testing whether it will be successful still lies with plugging it in. Even at these lengths, the cheaper choices are still worth considering if the installation of long HDMI Kabels is easily accessed and they work OK with your present equipment.
HDMI Kabel Test
