HDMI 2.1a Spec Revision Aims To Solve Your Short High Speed Cable Woes

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HDMI and DisplayPort both keep increasing the peak transfer rates of data signals across their cables. This is necessary to support higher resolutions and refresh rates, as well as the extra signaling required for things like HDMI Deep Color and High Dynamic Range video, so if you want fancy video signals, you need fancy cable standards.

The thing is, when you raise the signaling rate of a digital connection, you typically reduce its resilience to interference. Shielded cables can help to a degree, but there's only so much you can do once the data rate rises to the multiple-tens-of-gigabits-per-second levels of modern video connections.

One way to help combat interference is to increase the strength of the signals along the way by using active cables. This is how Thunderbolt works, after all. HDMI 2.1 doesn't specify a standard for active cabling, but you can find various third-party solutions on the internet, offering HDMI 2.1-capable cabling at lengths up to 75 feet or longer.

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They're also really expensive.

The problem with these active cables is that they require an external power source. Usually a USB connection is sufficient to provide the additional power required, so it's not like you need a wall wart for your HDMI cable. Still, it can be tedious to connect the extra power, and not all devices with USB ports supply sufficient power to said ports.

Well, along comes HDMI.org with a solution to your long-cable worries. HDMI 2.1a Amendment 1 is attaching a standard for active cabling, known as "HDMI Cable Power." It's more or less as simple as it sounds: "with this feature, active HDMI cables can now be powered directly from the HDMI connector, without attaching a separate power cable."

Obviously, to make use of this feature without using external power, you're going to have to have an HDMI Cable Power-capable device, and because this standard is brand new, that probably won't include any extant HDMI devices—even if they already support HDMI 2.1. Likewise, you'll need an HDMI cable that's capable of carrying the extra power, and you'll need to make sure you connect it the right way 'round, because active cables only go one way.