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Troubleshooting a cheap HDMI splitter


Stuart91

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Posted

Another week, another HDMI niggle...

 

This time we have a customer who's got an issue with what should be (on the surface) a fairly simple visual setup. They've got an iMac feeding into a cheap HDMI splitter (similar to this one). Two of the four outputs feed HDMI to SDI senders, which has a ~40m run to projectors. One of the remaining outputs feeds a local projector via a direct HDMI line.

 

The problem they've had is that one of the main projectors (on the SDI run) was flickering during their last event. It had been working fine earlier in the week, so my suspicion is that one of the patch leads might have come adrift somewhere. (Their rack is a complete mess) However the one bit of information that they can offer is that when they were having the problem, "all of the LEDs on the front were flicking on and off". Neither of the other projectors were exhibiting any kind of issue, so I don't think the problem was upstream of the splitter, but I'm not sure why the other indicators would blink as well.

 

They bought the HDMI splitter from some random online outlet, and binned the instructions immediately. I doubt if there would have been much useful information there anyway. What I'm not sure about is what, exactly, the front LEDs indicate. They only come on when a display is connected, but do they blink if the HDMI handshaking is interrupted? Could a problem with a display affect the other outputs, or should I be looking elsewhere for the root of the problem? I'm tempted to tell them to just try another splitter, for the sake of £15, but not convinced it's going to change anything, and every disrupted event just gets people more annoyed.

 

I'm trying to troubleshoot this remotely - the customers have done enough of their own work that it's not really "my" installation any more. But any pointers I can pass on to them would be very gratefully received.

Posted
I'd look at swapping items to see if the fault transposes. First try a different HDMI output (or swap the 2 SDI run outputs) to see if the fault continues or disappears. If not, swap the 2 HDMI > SDI converters. If the fault persists on the same projector the fault is either the SDI line or the projector, so I guess swap the 2 projectors over. Either way at some point the fault should move to a different projector "position" - if not then it would be the cable?
Posted
Cheap splitters can do weird stuff with the EDID (usually the last thing that happened on any display gets sent back to the source) so swapping items can be more confusing than usual, as the source may change or disable its output as the displays are plugged and unplugged, windows 10 is really horrible for this and does all sorts of nasty things.
Posted

Cheap splitters can do weird stuff with the EDID

 

That makes a lot of sense. (And might also explain why the customers' own attempts at troubleshooting have not led them anywhere).

 

If there's a loose connection on one output, then when it breaks and re-makes itself, the splitter will see that as fresh connection, and feed that EDID information back to the source? That would explain the blinking indicator lights, if everything is refreshed as part of that process. I'm still impressed (and a little skeptical) that it can do this without any glitches being visible on the other displays, although the customers may well have overlooked minor interruptions.

 

One other potential factor is that the rear projector (on a direct HDMI connection) is a portable machine, so may well have been the last thing plugged in. There's a chance that it might have negotiated a format with the source which the other projectors aren't as happy with.

 

The source computer is a relatively new iMac, so thankfully no Windows 10 issues to deal with at the moment.

Posted

Maybe suggest an edid emulator between the splitter and the source. I had to do this with our church install which has a proj and foldback monitor split from a pc laptop. The laptop would come up in a different resolution depending what got plugged in first and would disable the output if either display was disconnected or switched off, even though the other one was still on.

 

I used a cheap Lindy edid emulator to get round this.

Posted

Yes. Lindy do 2 types, the cheaper one has a range of fixed resolutions which you just choose on the source computer, but you need to check it offers the one you need.

 

The more expensive ones can be programmed with your desired resolution but you need a programming device as well as the edid device.

 

Also this still doesn't prevent the output blanking (on Windows) if one of the devices is turned off. I don't really understand why that is so...

  • 2 weeks later...
Posted
If the splitter is a real cheapo from eBay then it's worth checking if any power supply that was supplied with it is into one of those shady death-daptors and possibly arcing. If it's a real cheapo then the power supply should be considered an electrical hazard out the box.
Posted

'That's useful to know. It's daft that the lindy ones don't do that. ' - the HDFury Dr HDMI and New Dr HDMI 4K are often used on the output of a PC/Mac to ensure the Source stays active when connected to a Switch or Matrix, the HDFury Feature set is pretty useful in all manner of systems.

Joe

Posted

A quick update on the original situation - I ended up with no option but to go and pay them a visit. Managed to narrow the problem down to a couple of faulty connections - one intermittent HDMI cable, and a projector input socket that has clearly seen some abuse. What seems to have been happening is that the dodgy connections have been coming and going, leading to a fresh handshake with the source computer.

 

I added the HD Fury Dr HDMI into the chain, and whilst it seems to reduce the amount of flickering visible on the displays, there are still glitches when things are plugged and unplugged so the customer didn't want to spend the money on it. I'm quite happy to keep it myself as I'm pretty sure it'll come in handy elsewhere.

 

The other useful tool I found is SwitchResX for the Mac. I'd got hold of it to get a 4K screen working on a relatively old MacBook Pro, but it's quite useful for interrogating the EDID. It meant I could at least see when different information was being sent back to the source.

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