I had originally planned this "caution" on HDMI cables for a later date, but recent developments suggest "sooner better than later" timing.
As many of my past clients (and many among this readership) are in the process of moving to 4K/HDR systems, immediate consideration to the following could save you time, money and hassle down the road.
Whenever I install complete home theater systems I try to "future-proof" the hardware to the extent I can. That means installing a level of performance beyond the immediate requirements. This is always in the client's best interests as most of the upgrading to "the next new thing"—and you know it's comin'—is already in place when needed.
There is no better example of the merit of this practice than the current state of HDMI interconnect cables.
Recent advertisements have pretty much drilled into our heads that we need HDMI cables capable of 18Gbps transmission if we want unmolested 4K/HDR at even an 8-bit color depth. Turns out, a short look downstream sights much bigger demands.
See the "4K" chart below (courtesy of the Imaging Science Foundation) showing the pending potential bandwidth requirements (and HDMI cable designations) for the new HDMI 2.1 standard with 4K-resolution content at various frame rates. The first column shows the signal resolution and frame rate. The second column shows the potential options for chroma subsampling (i.e., color compression), where 4:4:4 represents uncompressed color and the highest quality. The third column represents the options for color bit-depth (Editor's note: you can read all about chroma subsampling and color bit-depth in the linked Tech Talk articles.-RS). The last two columns show the required bandwidth for each signal configuration and the official HDMI cable category that is certified to handle it.
You'll notice that as resolution, frame rate, color sub-sampling and bit depth become maximized, the required cable bandwidth quickly shoots to 48 Gbps.
Now get ready for 8K and screens with an aspect ratio of 21:9 (yes, 'Scope movies with no black bars—yea!...and yup, 45 million pixels). I predict the popularity of such screens will rise soon. By the way, these wider screens turn 8K into 10K!
So take a look at the "10K" chart below.
At maximum everything, we'll need cables capable of passing 120 Gbps comfortably—nearly seven times our current target. Clearly, these aren't on the shelf yet, but invention has always found a way to satisfy necessity in our industry when required to...especially when big bucks are involved.
Current advice: buy the very best carbon fiber-optic cables you can find (AVPro Store is a good place to look) as you transition to 4K/HDR. For long runs, pull two cables in conduit anywhere you go for a chance of not having to rip up the walls...again.