1

My problem involves connecting to an external display. For years I've been using a 2015 15" MacBook Pro with Retina Display (Current OS is 12.6.1, AMD Radeon R9 M370X 2GB / Intel Iris Pro 1536MB Graphics) to connect to an External Monitor to extend my Desktop. The external display is a LG SIGNAGE setup with 6 TV's hooked up together to project as one large display. I've never had issues connecting to this setup from my Windows laptop or Macbook Pro as it appears as a single external monitor with 720p resolution at 1920 x 1080 resolution with a 60Hz refresh rate. Here is a picture of what this display looks like: https://i.stack.imgur.com/oz0ae.jpg

Here are some specs that Windows identified with it once connected: display specs

I just bought a new 2021 14" MacBook M1 Pro (Current OS is 12.6.2) with Built-In Liquid Retina XDR Display. When I try to connect to the LG SIGNAGE external display as an external monitor, I cannot get the contents to display. It sometimes flickers for a second but just goes black. I'm using the native HDMI port on my MacBook Pro. My MacBook pro sees the external display as LG SIGNAGE so it detects it. Here are the steps I've tried to resolve the issue:

Tried multiple HDMI cables. All have the issue. Tried all the resolutions available. When I select scaling, I try every available resolution, along with different refresh rates (50 or 60Hz). I even try different color profiles. When I select the desire display of 1920x1080 it flickers for a second but goes black. None of the other available resolutions produce any flickering and just show nothing. Here is a video of it flickering: this is the problem

Tried connecting to other displays (Monitor, Projector, etc.) They all work flawlessly. Tried selecting 'Main Display' instead of Extended Display. It just shows Black. Instead of selecting External Display, I've selected 'Mirror for Built-In Liquid Retina XDR Display' - and it works! This is the odd thing - nothing works except for when I select this mode and it shows my mirrored display. Unfortunately this mirroring mode will not work my use case. Here is a picture of it doing that: mirroring works The port on my Macbook Pro that I am using is the native HDMI port. There is no DisplayPort in the mix, and thus I don't think any conversion needed for an active HDMI adapter solution.

Can you think of what might be the issue? Since I can get other laptops to work, I think it's just this new MacBook Pro. Since I can get it to work in Mirroring mode, I doubt its the cable or port. It seems to be a software issue with the OS perhaps or some other system config that isn't compatible with this LG SIGNAGE external display and the "Use as: Extended Display" mode.

Any help would be appreciated!

LeroyJenkins608
  • 11
  • Most likely, you need an active HDMI adapter. Your Mac’s video signal is DisplayPort and the conversion can get out of clock sync. – Allan Jan 05 '23 at 02:48
  • That sounds interesting - however the port on my Mac is a HDMI port. There are no DisplayPorts on my Mac. Given that the native port is an HDMI port, do you feel that an active HDMI adapter is still needed? – LeroyJenkins608 Jan 07 '23 at 21:02
  • The new M1 has a Thunderbolt port which carries the DisplayPort signaling. HDMI (not your Mac) lacks a clock signal making it easy to get out of sync when things like power save mode kicks in. I wrote about this in What’s Wrong with HDMI? – Allan Jan 07 '23 at 22:28
  • @Allan - I just wanted to say YOU ARE COMPLETELY CORRECT. I took your advice and used the USB-C port (DisplayPort) and it worked. I learned something new today about DisplayPort and clock signaling. Thank you for solving what I didn't think anybody could solve! – LeroyJenkins608 Jan 24 '23 at 22:44

0 Answers0