HDMI over Ethernet pair and DisplayPort adapter issues! HELP!  - Page 1
Forum section: electronics / general

author: edy
author_rank: Super Contributor
timestamp: July 13, 2021, 09:57:51 pm
content: I recently upgraded a computer that was using a dual display… VGA to monitor 1 and HDMI output to monitor 2. The second display was mounted in the ceiling (quite far away) and so when it was installed the computer tech used a device that puts it on what looks like 2 Ethernet cables. It’s powered and when I plug the HDMI in the box at one end it shows a red light on the box. On the other end (ceiling) is another box with the other side of the 2Ethernet cables plugged in and an HDMI output going out to the monitor.Anyways, my new computer has VGA and DisplayPort only, no HDMI output. So I got an “active” adapter (they didn’t have any passive) that converts DisplayPort to HDMI female. I thought I could just plug the cable in there but alas… doesn’t work. There must be too many conversions along the way or something is not communicating properly due to the HDMI-over-Cat5pair adapters I have at both ends.So should I be looking at a “passive” converter, or is there some other solution (installing a cheap dual video card into the machine) or hooking the ceiling monitor up to a Roku. Or maybe using DisplayPort over Ethernet boxes. I don’t think it will be easy to rewire or pull cables up through walls to ceiling, so if I can make use of the Ethernet pair already there somehow that would be best. Perhaps the active/passive is what I should try first.Any help would be greatly appreciated!!!!

author: edy
author_rank: Super Contributor
timestamp: July 13, 2021, 11:45:16 pm
content: Update… I returned the “active” adapters and got passive dongles (DP male to HDMI female). The computer detects the display, even identifies it by brand. I went in to advanced settings, adjusted resolution and refresh (1024x768 60Hz) and still a blank screen that times out after 60 seconds (monitor counts down for autoshutoff if doesn’t detect signal). So somehow the computer knows it’s plugged in to it, senses monitor type. Maybe signal strength is just not high enough? Not sure what to do… if I could find some cheap used basic video card with VGA and HDMI outs I could plug that in, forgot onboard graphics and just use that. The old computers I’m replacing also used motherboard graphics but at least they had VGA/HDMI outputs.

author: Whales
author_rank: Super Contributor
timestamp: July 13, 2021, 11:45:34 pm
content: Edit: ninja'dWhen you say "doesn't work":(1) Does your OS detect the monitor at the end of the system?(2) Does your OS detect the correct list of resolutions reported as supported by the monitor?(2) Does the active converter work at all? Might be a dud. Try plugging it in directly if you have anything else that takes HDMI.If a monitor is "detected" but you get a list of every resolution under the sun: your active adapter might not be passing EDID. Try manually choosing a very low resolution & refreshrate just as a test (eg 800x600@60Hz).Keep in mind that "HDMI" is a long list of standards with many versions and vastly different bitrates. At the lowest versions: it's essentially DVI with a few extras (hence why HDMI <-> DVI passive cables tend to work so well). Your extender boxes may only support the lower versions; but your converter dongle may be trying to different ones. Maybe possibly.

author: Whales
author_rank: Super Contributor
timestamp: July 13, 2021, 11:49:14 pm
content: If it's sensing monitor brand & supported resolutions: that means the EDID info is making across the link. That's a good start.Not sure sorry.- You could eliminate whether or not driver voodoo is a problem by temporarily booting Ubuntu off a USB stick and see if the remote monitor works.- You could eliminate whether or not the cat extender is a problem by plugging the new passive cable directly into the HDMI screen (ie temporarily move the computer)- You could elimitate whether or not the graphics card output is a problem by temporarily stealing any graphics card from somewhere else (although it sounds like you don't have any handy)

author: edy
author_rank: Super Contributor
timestamp: July 14, 2021, 02:10:58 pm
content: Ok, I plugged in the DP to HDMI adapter into computer DP port and HDMI cable running straight to the second monitor. Still nothing, but computer detected it. Went through all the settings for resolution and refresh that I knew worked before when I used old computer with HDMI output. Still a blank screen.Guess how I eventually got it to work…..I switched the displays around (in display settings) from primary and secondary… made the DP-HDMI monitor primary and VGA connected monitor secondary (before the VGA-connected monitor was primary and the DP was secondary). Voila! It worked!!!! Then I switched them BACK…. Guess what… They STILL worked!!!!I haven’t tried the HDMI-over-Ethernet boxes yet [EDIT: Now I have, it works fine] but now that I saw the symptoms I’m pretty sure everything will be good. Seems like I needed to swap primary-Secondary in Windows to have it “trigger” something in the software… because when I switched them back to the original configuration the setting it worked. Strange or what?Maybe some programming error in Windows or intel display drivers. Something has to initiate and maybe that only works when you make the other monitor primary and after that first time it sets the system properly, so you can switch back and forth (swap primary/secondary as many times as you want) and it will be fine.I can see how this stupidity can waste a lot of time and money if someone were to chase down the rabbit hole. I ended up returning active DP-HDMI adapters for passive (which were cheaper anyways) but this could have gone sideways really fast… buy discrete video cards, rewire cabling to ceiling monitor, etc… wow, all over a software bug that I discovered by accident?!?

author: edy
author_rank: Super Contributor
timestamp: July 15, 2021, 06:06:30 pm
content: UPDATE:So I had another machine (HP desktop) with the same situation... VGA out to primary monitor, and DP out via passive DP-HDMI adapter to HDMI cable going to converter box with pair of Ethernet to a ceiling mounted second monitor (HDMI input). Same as the previous post involving Lenovo machine.Anyways, as I was setting it up I noticed my steps more closely. Swapping primary/secondary didn't actually do it. Along the way with my first machine, I believe at some point just before this I switched from Extended to Clone/Duplicate. I believe THAT is what may have "snapped" the driver into properly handling both displays. After I cloned and set the proper display mode for my ceiling monitor, it worked. Then I went back to Extended and it was still good. So probably don't even need to be swapping the primary/secondary. The "trigger" may be playing with Extended/Clone setting.The moral of the story... Mess around with something long enough and you may stumble on a solution even if you have no idea why it works.