Read: Anatomy of our Premium HDMI Cable
November 2016 Update:
40 ft test passes full 4K 60Hz 4:4:4 in this video.
We've recently received questions about the methodology we use to test and certify our HDMI cables. This is becoming an increasingly interesting topic because as each new HDMI standard is released, there is a wider spectrum of quality found in cables that claim to accomplish the maximum spec. These days the high-end HDMI shopper is wanting to make sure that the HDMI cable they are purchasing:
1. Has been tested in an authorized third party lab (such as ATC)
2. Supports 4K 60Hz
3. Supports 4:4:4 chroma (no subsampling needed)
4. Successfully passes a bandwidth of 18 Gbps.
5. Successfully passes HDCP 2.2
Our 4K HDMI Cables
pass these and the other HDMI 2.0a specs.
1. Third Party Lab Testing (ATC Certification)
ATC certification (Authorized Testing Centers) or equivalent is required to claim specs, be in good graces with the HDMI consortium, and be able to use the HDMI trademark (e.g., using the term 'HDMI' to describe and sell HDMI cable). The HDMI organization has a list of authorized 3rd party testers that will certify that the product in question passes the specs that the product will be marketed under. It's also important to note that ATC certification typically applies to a factory rather than a brand (like how Foxconn is the factory that makes many Apple products for instance).
Simply having an ATC certification unfortunately is not a silver-bullet guarantee that the product you are purchasing will support all of the specs that it claims-- it just means that the cables that were tested passed, and that the product still passed after occasional testing cycles. Like most products, there is a spectrum of quality that HDMI products will have that is mostly determined by how good their quality control and quality assurance programs are. A good HDMI cable starts with good materials, but workmanship and precision play a large role in whether the cable will pass the most extreme tests (such as passing the full 18 Gbps for the HDMI 2.0 spec).
2. Supports 4K at 60Hz
Perhaps the most commonly asked question about an HDMI product is whether it supports 4K at 60 Hz. This simply means that it can display a picture that is roughly 4000 pixels wide, and it can refresh that 4K picture 60 times per second. The most common spec on the market these days is 4K at 30Hz (30 refreshes of that 4K picture). This requires half the bandwidth as the 60Hz spec simply because it is refreshing the 4K image half as fast.
One thing you might be asking is: Why bother? 30Hz is already faster than the human eye can distinguish, right?
Well, not really. It's true that even at 24Hz (the movie theater refresh rate), the human eye is tricked into thinking those objects that are moving on the screen are actually moving and are not just frames rapidly following each other in fast succession. When it comes to high-intensity gaming or watching an action flick however, fast moving objects tend to blur a lot more in 30Hz than in 60Hz. So that old adage is kind of correct when it comes to distinguishing frames from an animated picture, but when it comes to high-quality viewing, humans can easily tell the difference between 30Hz and 60Hz when put side-by-side!
3. 4:4:4 Chroma
This spec is lesser-known than the 4K@60Hz spec but describes a very similar thing. Color data takes up a lot of HDMI's bandwidth, and so something called 'chroma subsampling' was thought-up to save bandwidth and still trick the eye into thinking they are seeing 100% of the color data that every pixel is meant to carry. If all colors of all pixels are being refreshed in real time, there is no subsampling going on, and that is described as 4:4:4 chroma. 4:2:0 is a sub-sampling standard that is very common and requires only a fraction of the bandwidth that 4:4:4 requires.
The affect of chroma sub-sampling is somewhat analogous to a lower frame rate-- the colors tend to blur the more subsampled the picture is.
For a mind-blowing in-depth read on this, check out wikipedia
4. Successfully Passes a Bandwidth of 18 Gbps
If you were only able to test one thing, bandwidth is the thing that makes all the other specs work well in an HDMI cable. After all, HDMI is little more than a data signal, and if it has the bandwidth to send all of the data that's required, it will likely pass all of the other specs.
Bandwidth doesn't only rely on a nice thick gauge, although wire gauge is a very important aspect. Besides having a thick enough wire, the cable must also mitigate interference (electro-magnetic waves that come from our surroundings) and cross-talk (what happens if the many conductors within an HDMI cable are not shielded or twisted at the right frequency.
Attenuation is also a bad guy here. Attenuation happens because copper cable (or any material) has a certain amount of electrical resistance. The longer the cable is, the stronger the signal has to be in order to travel further down that copper cable. So in this case, copper purity plays a large role as well as the wire gauge.
5. HDCP 2.2
Passing HDCP 2.2 might not be contingent on the cable, but it's worth mentioning here that passing HDCP 2.2 is one of the tests that we require our QC/QA team to perform. Since HDCP 2.2 is not backwards compatible, it's very important that all of our HDMI cable is capable of passing that and also older versions of HDCP for maximum compatibility.
Some Office Tests For Your Enjoyment
Like I said, the actual QC/QA happens at the factory. For anyone reading this that's NOT Six Sigma certified, catching quality problems at the factory is several orders of magnitude less-costly than selling bad cables to real people, so we put a lot of resources into quality assurance before the cable is sold. OK-- I admit I'm personally not Six Sigma certified either.
That being said, I went ahead and used our tester here in the office to demonstrate some benchmarks. This test is for our 15 foot 4K HDMI cable
Our in-office tester isn't nearly as big and doesn't have nearly as many buttons as the test equipment used at the factory, but we can at least test for the things that matter most (like bandwidth).
One of the most difficult specs to pass is to run the 4K 60Hz resolution with 4:4:4 chroma (no chroma subsampling). This is an image showing us select the 4:4:4 option on the generator.
Test results up-close. The most important spec here is the second one that tests 18Gbps bandwidth with a 4K 60Hz resolution. We didn't bother to run the 480p test in this demo so that one did not register a signal.