Tagged: HDBT 4K loop through
May 26, 2020 at 10:04 am #4002
We regularly use HDBT to transmit single HD displays over CAT6 to monitors, but with customers budgets disappearing and reducing equipment in comms rooms we are looking at utilising the in built matrix function of professional displays but having issues with the looping.
Is there anything we need to look at with regards to HDBT and using it in this manner? The idea would be to pass 4K@30Hz from a video wall processor (Windows based) over to a display and then that display pass the signal to loop through via HDMI. We have tried this on a display which when connected direct does pass through but HDBT doesn’t (Shows fine on the display source connected to), we suspect its down to EDID but wondered if anyone else has faced this issue and if so how did you overcome it? I have read the technical paper about working out the signal route and to my knowledge HDCP etc is passed through the loop, its not MST based and instead I believe clones to the looped displays.
Any help or advice would be greatly appreciated.May 26, 2020 at 12:27 pm #4003
Thanks for contacting us.
I would like to try and help you out here, but I’m afraid that I do not fully understand the system setup. Could you please elaborate? Also, please let me know brand/model of the display.
DanielMay 26, 2020 at 12:45 pm #4004
Thank you for the quick response. We are using 8x 4K@30Hz to drive 24x Barco Overview LVD displays (8×3 so the bottom row is showing only the top half of the 4K). The signal comes out of the controller as HDMI 4K@30Hz then over shielded CAT6 by HDBT, then it comes out of the HDBT in to the HDMI input on the Barco display, which works fine. The display should then pass the signal out of its Display Port out and in to Display Port in on the second display, then again out as display port and in to the next. Then using an internal matrix show the appropriate section of the 4K (e.g. 2×2 HD displays = 1x 4K image).
The weird thing is it worked for a short period and after a reboot of the display it never worked again.May 27, 2020 at 7:07 am #4005
Thanks for the additional info – things are considerably clearer to me now.
As I understand it, the Barco display does not have a built-in HDBaseT port, so you are using an HDBaseT receiver that outputs the HDMI stream to the Barco HDMI port. That part of the system works well, but the problem you are having is with the DP output to the next display. So it would appear that this is not an HDBaseT issue, but rather something with the display itself.
You have suggested that maybe this might be an issue related to HDCP. As far as the HDBaseT link is concerned, we are just a passthrough channel for the DDC. But maybe this could be an HDCP compatibility issue with the source itself. A few suggestions:
– With the existing setup, try running non-HDCP video to see if it works
– Try to remove the HDBaseT link completely, and drive the existing source directly into the HDMI input of the first display
– Have you tried swapping the displays around to see if this is an issue with the specific display itself?
– Have you reached out to Barco support?
DanielMay 27, 2020 at 7:35 am #4014
Thank you for the reply, direct loop through works fine, also it’s a Windows Pc output so no HDCP content. I thought maybe EDID related?
I am onsite today but it’s happening on all 8 outputs, none of the loops are going through but display 1 is ok.
I will do more tests today and will let you know how I get on.May 27, 2020 at 7:54 am #4019
OK – let me know how you get on.
Which receiver box are you using on the first screen?
DanielMay 27, 2020 at 8:00 am #4020
The first screen in each loop is using an OEM HDBT receiver, I am not sure of the original manufacturer sorry.
strange how it works on the first displays but not on the sub displays though, is there anything else you can think I could try?May 27, 2020 at 8:40 am #4021
Ok so direct it works fine and on one of the loops I put an edid emulator in to the hd t receiver and then out the emulator in to display 1, that now loops through.
On another display I have instead attached the receiver to an hdmi splitter, then an HDMI to 2 separate displays, both of those now work too! Looks to be an edid issue.
Any idea from an HDBT point of view why that wouldn’t work?May 27, 2020 at 1:02 pm #4022
Checking…May 31, 2020 at 10:46 am #4023
A couple of points to try out:
– Use a much shorter HDBaseT link cable (a few meters long)
– You mentioned using anHDMI splitter between on the output from the receiver, and you run HDMI from the splitter to the other displays. If you take the output from the splitter and input it only to the first display, and then use the DP output to connect to the rest of the displays, does it work? I wonder if there might be a clock jitter/sensitivity that may be affecting the performance of the HDMI-to-DP converter IC within the display (try a few different splitters if you have them available to see which help and which do not)
– I would still recommend you reach out to Barco support, as the HDBaseT link is up and running well (the first display works)
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