Not sure if anyone can help with this, but I'm having an annoying problem and its really starting to frustrate me.
I have several PCs where I want to take the 4k video signal and display it on a combination of 4k and 2k displays. I solved this problem using a J-Tec 18GSP14M mixed video splitter/downscaler. Its a 1x4 splitter that can take a 4k input and output either 4k or 2k signals. I have 2 of these on separate PCs and they worked flawlessly for several years.
Starting a few months ago, both splitters simultaneously began to exhibit the same problem. It will be working fine, then "something* happens(usually a power outage, but any number of things have done it). And the display from the splitter on my 4k screen becomes fuzzy. I can usually "fix" this after untold hours of diddling around with the system, but I've not thusfar found "the fix" that works every time, and its getting very frustrating. I don't believe the problem is just that the hardware is failing, but I don't know.
To be clear: the downscaled video always looks bad, that's to be expected. The problem is the regular scaled video is not getting passed properly, and I don't know why this is happening.
Anyone got any ideas?
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My guess is the splitter is re-negotiating the resolution with the HDMI source (on a power glitch or other disturbance). And it drops down from 4K to 2K (or worse).
This does seem likely. Problem is I cannot make it re-negotiate back to 4k for love or money. The last time this happened(a few weeks ago) I tried ever trick I knew, eventually gave up, and bypassed the jtec downscalers. A few days later I decided to get back to work on it, hooked the downscaler back up, and it just... worked. I've no idea why any of this is happening, or how to prevent it.
An EDID emulator between the source and the splitter/scaler should let you force the resolution negotiation to 4K only.
without an EDID emulator the usual way of getting the resolution back to max would be to turn off all the devices and remove power (don't just turn them off, remove the power cables), remove the HDMI cables (to prevent power leaking through the cables to power other devices), wait a bit for power to dissipate, then reconnect the cables and power up the devices. Try different orders, say, connect and power up only the 4K devices to be sure any EDID negotiation comes from them.
Last edited by jagabo; 28th Feb 2023 at 20:12.
Every device between the PC and the display claims to do EDID emulation, none does. I've also tried dedicated EDID emulators, but all of them produced fuzzy video as well.
About the only thing that works every time is to string an HDMI cable directly from the source to the display, then slowly add devices working my way back up the chain. Unfortunately today even THAT doesn't seem to be working. At present my attempts to fix are only managing to break everything even worse.
Hello! In some cases, a power outage or other interference can cause HDMI devices to revise the resolution, resulting in a lower quality signal being sent to the splitter/downscaler. This may explain why normal scaled video is not being transmitted properly. You could try connecting the devices to an uninterruptible power supply or surge protector to protect against power surges or outages. You can also try setting the resolution on the source devices to a fixed value (such as 4K) to prevent re-matching the resolution to the splitter/downsampler.
So where I last left this problem, I'd gotten so frustrated I gave up and bypassed the downscalling switchers. This post reminded me of the problem, and I just hooked one back up. Low and behold: it working fine. Apparently I just have to leave the bloody thing alone for a couple months and it magically fixes itself.
I am definitely phasing these things when I build my new setup in a couple months.
Maybe you're right. In any case, in 2 months you will see whether this thing has tuned itself or not.