HDMI cable difference?

James S.

James S.

Audioholic Intern
I asked this on another site, but I thought I would see if anyone knows here. Wondering if someone knows what the physical difference is the makes the HDMI versions different. I get the spec differences and what each version does, but what makes one cable pass 8k/60hz and the other can't. I thought cables are copper wiring with connectors on each end. What difference is in the actual cable that makes it able to pass higher bandwidth, channels, etc? Thanks.
 
sweetness34

sweetness34

Enthusiast
I believe the physical internals of and HDMI 2.0 and 2.1 cable are the same (4 twisted pairs along with 7 individual wires). The reason HDMI 2.1 can handle a higher bandwidth because it uses the new Fixed Rate Link technology to send uncompressed signals and the DSC 2.1 technology when compression is required.
 
TLS Guy

TLS Guy

Audioholic Slumlord
I asked this on another site, but I thought I would see if anyone knows here. Wondering if someone knows what the physical difference is the makes the HDMI versions different. I get the spec differences and what each version does, but what makes one cable pass 8k/60hz and the other can't. I thought cables are copper wiring with connectors on each end. What difference is in the actual cable that makes it able to pass higher bandwidth, channels, etc? Thanks.
Digital signals are not like analog ones. Digital signals operate at very high frequencies, sending packets of discrete information. So internal reflections in the cable matter. So design and optimizing impedance of the cable and terminations is crucial. Now digital cables will either transmit a digital signal with a low enough error rate or they won't. So if sufficient packets of bits of information are lost, you eventually exceed the error correction rate of the receiving devices. Then you start getting glitches, dropouts and total loss of a useable signal. Where copper wires are concerned the length of the cable is a big issue. For that reason I recommend optical HDMI cables for lengths over 12 ft ideally and definitely for lengths over 25 ft. Optical transmission results in much less degradation.

You can not apply analog audio transmission theory to the transfer of digital signals. The rules are very different.
 
Otto Pylot

Otto Pylot

Junior Audioholic
Here's my answer to your question from the "other" site ;) . I limited my response to copper only cables but I'm glad the fiber optic cables were mentioned above.

High Speed HDMI cable is the basic description for a non-certified, passive HDMI cable that will pass the HDMI 2.0 options sets.

Premium High Speed HDMI cables is a certified, passive, High Speed HDMI cable that has been tested and certified by an ATC (Authorized Testing Center) by a standardized testing program designed by HDMI.org and certified by HDMI LA to meet the HDMI 2.0 option sets. The cables will come with a QR label of authenticity affixed to the packaging. PHS HDMI cables can be certified up to 25' lengths.

Ultra High Speed HDMI cable is the new designation for certified, passive, High Speed HDMI cables that have been tested/certified for the new HDMI 2.1 option sets. They are certifiable up to 16' lengths.

Certification is not a guarantee that the cable will work 100% of the time for all devices and setups. It is mostly for consumer confidence that the cable has been tested and certified following standardized protocols so regardless of who you purchase the cable from, if it is labeled as Premium High Speed HDMI or Ultra High Speed HDMI, and comes with the QR label, it has been tested by an ATC. That being said, cable mfrs are very clever with their marketing, product descriptions, claims, etc so read and purchase carefully.

Passive HDMI cables are just copper wiring that has been designed and built well to handle the bandwidth required, and options offered, for the HDMI chipsets at the source and sink end. The cable is just a data pipe, nothing more.

Active cables are an entirely different animal altogether. They were basically developed to handle the HDMI option sets over longer distances by employing chipsets in the connector ends that communicate with the HDMI ports in your source and sink devices. They do this by utilizing error correction, timing, etc protocols, and require a small amount of power that they pull from the HDMI ports. They can not be certified but that is changing soon as one mfr has an ATC certified active cable that they will soon be marketing. There are lots of caveats to using active HDMI cables.

HDMI is backwards compatible but only to the in-common option sets. So, pushing options from an HDMI 2.1 source to an HDMI 2.0 sink will only properly utilize the HDMI 2.0 option sets.
 
BMXTRIX

BMXTRIX

Audioholic Warlord
@Otto Pylot -

High Speed HDMI is not a 'non-certified' cable. Any cable can make any claim, but to carry logos from hdmi.org they all must be certified to meet the speed/resolution requirements for each class. So, to say your cable is capable of 48Gb/s bandwidth (HDMI 2.1 full resolution), they can do so. But, to carry the HDMI Ultra High Speed logo, then it must be certified at that speed. The same is true for all versions of HDMI cables that carry an official logo.
HDMI has a full writeup of their different cable types and classifications right here:

I typically refer to them in bandwidth categories. Most cables you buy are 10Gb/s capable. That's enough for 1080p viewing. It was the first generation of 4K at 30Hz, but not enough for all the new 4K displays on the market which need an 18Gb/s connection.

As to actual cable differences, I would expect that most of it is similar to how cat5e, cat6, cat7, etc. are different. They build the cables to a higher tolerance rating. They use more twists, better shielding, and newer technology to build the cables to pass the bandwidth that is required. The jump from 720p to 1080p wasn't a huge issue, but there were some cables which couldn't handle 1080p/60 years ago. But, the jump from the 4Gb/s which 1080p requires to the 18Gb/s which 4K/60 requires has been crushing to many cables and the components which connect them.

To this day, there is not a wall plate which you can plug in a 4K source and reliably pass it up to a TV easily. No standard keystone HDMI connections can do it. I have yet to see an active wall plate which can do it which isn't $1,000+.

8K and 48Gb/s (HDMI 2.1) is another level. There are cables coming to market which make claims for 48Gb/s support. But, anything claiming HDMI 2.1 support is something to be wary of. The full 48Gb/s bandwidth is rarely supported in any new product. Most just support some lower level of bandwidth. 33Gb/s or so. The PS5 and XBox Series are excellent examples of products which go beyond HDMI 2.0, but aren't full bandwidth HDMI 2.1.

All of this, and HDMI still doesn't require a stereo stream alongside surround sound in all of their products so you can hook up headphones or a second zone easily.
 
Otto Pylot

Otto Pylot

Junior Audioholic
@Otto Pylot -

High Speed HDMI is not a 'non-certified' cable. Any cable can make any claim, but to carry logos from hdmi.org they all must be certified to meet the speed/resolution requirements for each class. So, to say your cable is capable of 48Gb/s bandwidth (HDMI 2.1 full resolution), they can do so. But, to carry the HDMI Ultra High Speed logo, then it must be certified at that speed. The same is true for all versions of HDMI cables that carry an official logo.
HDMI has a full writeup of their different cable types and classifications right here:

I typically refer to them in bandwidth categories. Most cables you buy are 10Gb/s capable. That's enough for 1080p viewing. It was the first generation of 4K at 30Hz, but not enough for all the new 4K displays on the market which need an 18Gb/s connection.

As to actual cable differences, I would expect that most of it is similar to how cat5e, cat6, cat7, etc. are different. They build the cables to a higher tolerance rating. They use more twists, better shielding, and newer technology to build the cables to pass the bandwidth that is required. The jump from 720p to 1080p wasn't a huge issue, but there were some cables which couldn't handle 1080p/60 years ago. But, the jump from the 4Gb/s which 1080p requires to the 18Gb/s which 4K/60 requires has been crushing to many cables and the components which connect them.

To this day, there is not a wall plate which you can plug in a 4K source and reliably pass it up to a TV easily. No standard keystone HDMI connections can do it. I have yet to see an active wall plate which can do it which isn't $1,000+.

8K and 48Gb/s (HDMI 2.1) is another level. There are cables coming to market which make claims for 48Gb/s support. But, anything claiming HDMI 2.1 support is something to be wary of. The full 48Gb/s bandwidth is rarely supported in any new product. Most just support some lower level of bandwidth. 33Gb/s or so. The PS5 and XBox Series are excellent examples of products which go beyond HDMI 2.0, but aren't full bandwidth HDMI 2.1.

All of this, and HDMI still doesn't require a stereo stream alongside surround sound in all of their products so you can hook up headphones or a second zone easily.
By "non-certified" I meant a cable that does not have the QR label of authenticity affixed to the packaging or is labeled as Premium High Speed (HDMI 2.0 options) or Ultra High Speed (HDMI 2.1 options). I thought I made that clear but maybe not. I suppose I could have mentioned that wall plates, extenders, adapters, etc are not recommended for active cables as you alluded to but I figured my response was long enough. I could have also gone into conduit use, bend radius and strain on the HDMI ports as well but chose not to do so.
 
BMXTRIX

BMXTRIX

Audioholic Warlord
@Otto Pylot - You know beginners. If they aren't familiar with it, they can get buried in the minutiae.

We did some in-house testing of 4K video and trying to pass it through wall plates. We did NOT use active cables, but just passive cables. We couldn't get video to work at 6 feet passing through any wall plate that we tried. We used different models, but the Extron one was the most disappointing since it specifically listed support for 4K/18Gb/s on their website and they are a respected brand.

We also tried using a Extron cable equalizer. This was super annoying, because if the cable passed through their wall plate, it was super erratic and had video dropouts even with 3, 3 foot cables in use. But, if used directly, two 12' cables could be used giving you 24' of 4K video - no problem, on super thin/lightweight HDMI 2.0 cables.
This was made worse because their active cable equalizer is small enough to fit into a wall plate if they wanted to build it that way. It would be the ONLY active HDMI 2.0 wall plate equalizer on the market that I am aware of and would solve a host of problems in the industry... if they would only make it that way.
 
Otto Pylot

Otto Pylot

Junior Audioholic
@Otto Pylot - You know beginners. If they aren't familiar with it, they can get buried in the minutiae.

We did some in-house testing of 4K video and trying to pass it through wall plates. We did NOT use active cables, but just passive cables. We couldn't get video to work at 6 feet passing through any wall plate that we tried. We used different models, but the Extron one was the most disappointing since it specifically listed support for 4K/18Gb/s on their website and they are a respected brand.

We also tried using a Extron cable equalizer. This was super annoying, because if the cable passed through their wall plate, it was super erratic and had video dropouts even with 3, 3 foot cables in use. But, if used directly, two 12' cables could be used giving you 24' of 4K video - no problem, on super thin/lightweight HDMI 2.0 cables.
This was made worse because their active cable equalizer is small enough to fit into a wall plate if they wanted to build it that way. It would be the ONLY active HDMI 2.0 wall plate equalizer on the market that I am aware of and would solve a host of problems in the industry... if they would only make it that way.
Yeah, I have a tendency to go on a bit longer than I should with my canned responses. That is interesting about the issues with passive cables. Never thought that it would be a concern. You have to wonder sometimes, even with reputable companies, just how tight their specs are for passing in-house QA/QC so they can make a claim. That's why I like the HDMI LA certification program, but it too is far from ideal. At least there is some standardization as to pass/fail that all subscribers to the program have to follow.

Having a reliable HDMI 2.0 wall plate would be nice if the potential of incompatibility with the cable connector end chipsets could be reduced or eliminated altogether. Now, with HDMI 2.1 upon us, and the gamers wanting those long cable runs the problems of connectivity rear its ugly head again. It's going to be interesting once 8k or 12-bit panels become the norm and the full 48Gbps bandwidth is needed for source material that requires it.

I really do dislike HDMI.
 

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