Does the length of HDMI 2.1 cable matter? - Page 1
Forum section: electronics / general

author: eeguy
author_rank: Regular Contributor
timestamp: June 13, 2022, 07:56:27 pm
content: Hi, I plan to buy a HDMI 2.1 cable to connect between a high-end PC with Nvidia RTX GPU and a 4K TV at 120-144Hz. Does the length matter? Even within the same company one guy said it doesn't but the other said it does. However, he could not provide a number for the maximum recommended length. Some manufacturers list the AWG value. At the same length, is the larger the AWG the better or the other way around? How about 30AWG for 2m cable and 28AWG for 3m cable? Are these specs good enough?

author: wraper
author_rank: Unknown
timestamp: June 13, 2022, 08:02:50 pm
content: AWG as such does not say anything about its quality. But I don't suggest buying more than 2m unless you really need such length. With 2m significantly lower quality of cable is acceptable to work without issues.

author: wraper
author_rank: Unknown
timestamp: June 13, 2022, 08:06:59 pm
content: The problem is that this cable market is full of BS and a lot of cables are not up to spec. Not to say more expensive often is not better but worse than an inexpensive cable which was properly made according to spec.

author: wraper
author_rank: Unknown
timestamp: June 13, 2022, 08:16:17 pm
content: Personally I would buy something like Amazon basics. No fancy braid or other marketing BS but should work with no problems, and is amongst the safest options. For some weird reason 10ft cable is the least expensivehttps://www.amazon.com/dp/B08BRYJWSM/ref=twister_B08BS2HWB6?_encoding=UTF8&th=1.

author: eeguy
author_rank: Regular Contributor
timestamp: June 13, 2022, 08:32:25 pm
content: How about these two?https://www.amazon.com/Cable-Matters-3-Pack-48Gbps-Support/dp/B084RFQPSP/ref=sr_1_1?crid=1TY19Z6OI2W4&keywords=B084RFQPSP&qid=1655151969&sprefix=b084rfqpsp%2Caps%2C57&sr=8-1andhttps://www.amazon.com/gp/product/B09CHH8TRC/ref=ox_sc_act_title_1?smid=ATVPDKIKX0DER&psc=1I bought a StarTech HDMI 2.1 cable but there are some issues when used with Cable Matters's adapter. Not sure if the issues are caused by the cable, the adaptor or something else. Cable Matters suggested using the one listed above with their adapter. How are the products of these two companies?

author: wraper
author_rank: Unknown
timestamp: June 13, 2022, 08:39:45 pm
content: Quote from: eeguy on June 13, 2022, 08:32:25 pmI have doubts if the first one meets the spec or not, especially considering misleading 4k/240Hz 8k/120Hz claim, and it's a 3-pack. Second cable should be fine but it's an unneeded waste of money which won't improve anything.

author: eeguy
author_rank: Regular Contributor
timestamp: June 13, 2022, 08:48:04 pm
content: Yes, 4k/240Hz and 8k/120Hz seem too good to be true. Also the price seems low for three such high performance cables. So having the HDMI 2.1 certification from hdmi.org does not mean anything?

author: wraper
author_rank: Unknown
timestamp: June 13, 2022, 08:49:14 pm
content: Startech is a reputable company. Dunno anything about Cable Matters but looking on their website I have a suspicion they do not design anything of what they sell and just rebrand some Chinese stuff.

author: wraper
author_rank: Unknown
timestamp: June 13, 2022, 08:53:35 pm
content: Quote from: eeguy on June 13, 2022, 08:48:04 pmBut they claim the same 48Gbps throughput. So dunno where they got those resolutions. if it's certified as 2.1, it means it must meet the spec and work flawlessly up to 48Gbps. But not nearly everything that claim certification was actually tested and passed. Often crappy cables work fine on a first glance, but they may be marginally operational, emit EMI or are susceptible to external noise.

author: wraper
author_rank: Unknown
timestamp: June 13, 2022, 09:01:24 pm
content: I'm convinced they resell Chinese garbage.The same thing sold for way more more than on Aliexpress:https://www.aliexpress.com/item/4000720445216.htmlhttps://www.aliexpress.com/item/1005003809439717.htmlhttps://www.cablematters.com/pc-682-140-5-port-hdmi-switch-supporting-4k-resolution-with-twin-pack-6-feet-high-speed-hdmi-cable.aspx#The only difference I see is a slight enclosure customization. Every connection or indicator is in exactly the same place.

author: Kjelt
author_rank: Super Contributor
timestamp: June 13, 2022, 09:04:03 pm
content: If you need an HDMI cable for 48Gbps longer than two metres then you should buy an active optical cable with transceivers on both ends. Then the length does not matter much anymore.I use 15m of these cables for 4K/10bit 60Hz video, never a glitch.

author: eeguy
author_rank: Regular Contributor
timestamp: June 13, 2022, 11:12:54 pm
content: Quote from: Kjelt on June 13, 2022, 09:04:03 pmI only need 3m maximum. Any recommended active optical cable with transceivers on both ends?

author: Zoli
author_rank: Frequent Contributor
timestamp: June 13, 2022, 11:17:30 pm
content: Quote from: eeguy on June 13, 2022, 11:12:54 pmTake a look, it worth it:http://www.bluejeanscable.com/NAWTS, as usual.

author: tooki
author_rank: Super Contributor
timestamp: June 14, 2022, 07:29:08 am
content: Quote from: eeguy on June 13, 2022, 11:12:54 pmYou don’t need an optical cable for just 3m. Just get a good quality cable and it’ll be fine. Good quality doesn’t have to be expensive: Blue Jeans Cable sells a 3m cable specifically for UHD for $22.

author: madires
author_rank: Super Contributor
timestamp: June 14, 2022, 08:19:32 am
content: The common estimation for the maximal length of a passive HDMI 2.1 cable is 5m.

author: eeguy
author_rank: Regular Contributor
timestamp: June 14, 2022, 12:40:25 pm
content: How come Startech's cables are more expensive than most other brands?

author: Kjelt
author_rank: Super Contributor
timestamp: June 14, 2022, 12:44:55 pm
content: Indeed for that short length passive cables would suffice but if you really intend to use for 4K/50 and higher the cable and pair shielding becomes really important.Be aware for manufacturers or sellers selling HDMI2.1 or 4KHDR cables etc., they do not use the proper terminology since HDMI2.1 also has all the backward compatible formats like 1080p25 in it.So by itself this says nothing.Check if the proper terms are used ON the cable itself which should be: Category 3 HDMI or "Ultra High Speed" HDMI cable.

author: wraper
author_rank: Unknown
timestamp: June 14, 2022, 12:49:34 pm
content: Quote from: eeguy on June 14, 2022, 12:40:25 pmThey have quite fancy connector construction and you pay for it being Startech. BTW by adapter which you purchased you mean something from these?https://www.cablematters.com/c-141-adapters.aspx. The vast majority of them look like pure Chinesium sold on Aliexpress for less than $2 with delivery from China included. Usually they are total trash with no regards to signal integrity whatsoever.

author: eeguy
author_rank: Regular Contributor
timestamp: June 14, 2022, 01:35:05 pm
content: So they are like the Apple in the cable industry? I tried their DisplayPort 1.4 to HDMI 2.1 adapter but there are issues with fuzzy text. I also tried Club3D's adapter and cable but the display could not even detect the PC. Know any good DisplayPort 1.4 to HDMI 2.1 adapter that can do 4K@120/144Hz with chroma 444?

author: tszaboo
author_rank: Super Contributor
timestamp: June 14, 2022, 01:45:09 pm
content: Yes absolutely, cable quality and length matters at those speeds. Eye diagram will look bad, and you will get disconnections of dropped frames or other digital weirdness.Linus tech tips had a HDMI cable tester not that long ago, and they tested a bunch of cables, check out their video about it. If you can find it since they are named clickbait recently.

author: wraper
author_rank: Unknown
timestamp: June 14, 2022, 01:56:25 pm
content: Quote from: eeguy on June 14, 2022, 01:35:05 pmThen likely it does 4:2:0 or 4:2:2 chroma subsampling.

author: tooki
author_rank: Super Contributor
timestamp: June 14, 2022, 03:56:46 pm
content: Quote from: eeguy on June 14, 2022, 01:35:05 pmBlurriness isn’t, as far as I understand it, a possible symptom of a bad DP-HDMI adapter: marginal connections manifest as “sparkles” (random-color pixels) and handshaking failure (display isn’t recognized at all, or flashes or drops out completely). Remember that standard DP-HDMI adapters don’t actuallydoanything: they just connect pins of the two connectors. The DisplayPort output of the graphics card actually just detects the presence of the adapter and then changes its signaling to output HDMI signals instead.

author: wraper
author_rank: Unknown
timestamp: June 14, 2022, 04:45:51 pm
content: Quote from: tooki on June 14, 2022, 03:56:46 pmActually they do. Passive adapters have a level shifter in them. However with given resolution/refresh rate it must be an active adapter.QuoteIt outputs HDMI signal, however voltages are wrong for HDMI, hence level shifter is needed.

author: tom66
author_rank: Super Contributor
timestamp: June 14, 2022, 04:49:16 pm
content: I'm reasonably sure the 8K/120Hz standard (who the hell asked for that outside of broadcast editing?) is using a form of near-lossless compression. That's why it can run on the 4K/120Hz cables. The bitrate is about 25% that of a compressed stream. It's probably also chroma subsampled.

author: tooki
author_rank: Super Contributor
timestamp: June 15, 2022, 01:37:57 am
content: Quote from: wraper on June 14, 2022, 04:45:51 pmAh! I’d never heard that the adapters contain level shifters.Why would the higher resolutionrequireit to be an active converter? (I use the terminology that it’s an “adapter” if it’s passive, “converter” for a device that actually converts from one signal type to another.)

author: wraper
author_rank: Unknown
timestamp: June 15, 2022, 06:47:10 am
content: Quote from: tooki on June 15, 2022, 01:37:57 amIIRC with "type 1" passive adapter up to 165MHz pixel clock is possible. Which means up to 1920x1200@60Hz or 2560x1600@30Hz. Up to 300MHz pixel clock (2560x1600@60Hz or 4K@30Hz) is possible with passive "type 2" adapter. I'm not aware of standard which would allow higher pixel clock with passive adapter.