Catalina causing issues with HDMI

AudibleNectar

macrumors member
Jan 22, 2018
47
31
I have a new Mac mini running to an LG 4K monitor as well as a Sony 55" TV via HDMI (10.15.1, adapter firmware version 2.0a) and notice that the LG does delay a bit in waking up. The Sony comes up right away on power-up, Apple logo showing then to login screen, but the LG wants to be slow on the wakeup, not appearing until several seconds after the Sony shows the login.......then the LG comes up afterwards.

There also seems to be some differences in how the monitors "optimize" for best screen resolution, the Sony 55" being a 1080 display and the LG 4K 27" being the newer 4K. If it's set to be optimized for the Sony, the LG looks noticeably inferior in resolution, if optimized for the LG it looks great and the Sony res tails off just a bit (but not as much).

Both issues have had mentions here seemingly relating to the newer OS version, so it's good news and a bit of not so much as I do generally have my theater system/computer communicating and working pretty well otherwise but know that it might be necessary to wait this out while Apple devises the proper tweaks to address.......

I set the machine to not auto update as I want o leave well enough alone until I see/read more from here as to how this is being addressed.

I am new to Mac computers and had a good amount of wondering/curiosity as to how well this might work out in a multimedia environment, and generally seems like "yes" albeit these issues.

So I will intently watch here/read along and see what is discovered about resolving these....
 

redbaron123

macrumors newbie
Jan 14, 2012
3
0
For what it's worth, thank you for this thread. I've been having display problems since ~Oct 2019 but have been living with it hoping for a solution in an update. Finally tested out a USB-C to HDMI dongle from Amazon, and it has solved my problem. I had been using HDMI-to-HDMI before.

My setup is a little complex, but had been working fine for years up until Catalina.
I use a Mac mini, connected to a Sony Stereo via HDMI with passthrough, which then outputs to a Sony Bravia TV with HDMI ARC. That let's me get audio and video through the TV when the stereo is off, through the stereo when it's on, or I can switch inputs on the TV and still get audio through the stereo.
But since the Oct Catalina update, every time either the TV or the Stereo would turn off, the Mac mini would lose its output, and all I could get was a black screen until I rebooted and Sleep and wake-up with the TV and stereo both on.
Long story short, since switching to USB-C on the Mac, the video output works again whether I have the stereo or TV on or off.
 

tk_mac

macrumors member
Dec 26, 2019
49
7
I was having issues with HDMI to HDMI connections of my 2018 Mac Mini to LG 4K monitor and Samsung 4K TV until I got this

Belkin USB-C to HDMI Adapter

The mini is working well with the Samsung TV, and I have yet to try the LG monitor again.

Apple also told me the engineers found a fix and they plan to release it as part of the Catalina 10.15.3 update.
 

bfChris2

macrumors newbie
Apr 27, 2014
20
4
Virginia, USA
SOLUTION FOUND (LG):
One of our editors had this issue, and jiggling the HDMI cable would intermittently get a signal to the LG OLED 55" 4K tv, but it would be black a few seconds later.

The fix that worked was to change a setting in the tv. Toggle ON the setting for "HDMI Ultra HD Deep Color." It's found in the LG tv's Advanced Picture settings.
 

tk_mac

macrumors member
Dec 26, 2019
49
7
I have tried this adapter with success on my 24” 4K LG computer monitor. This adapter resolves my HDMI issued on both of my 4K screens.

Belkin USB-C to HDMI Adapter
 

tk_mac

macrumors member
Dec 26, 2019
49
7
10.15.3 is out today. Anyone try it? Does it fix this issue? Apple Support told me weeks ago that it will fix it.
 

mikeka

macrumors newbie
Jan 31, 2013
29
14
Not fixed here. No HDMI output. Mac Mini 2018.

Fine under Mojave.

I'm done with Catalina. They've known about this for how long now?
 
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djc6

macrumors 6502a
Aug 11, 2007
591
135
Cleveland, OH
Not fixed here. No HDMI output. Mac Mini 2018.
I went from 10.14.6 to 10.15.3 today - no output on HDMI after I shutdown first time. Once I started back up, only the display connected via USB-C -> HDMI worked.

Then I reset my SMC (shut down mac mini; hold down power button 10 seconds) - then voila! My 4K display worked over HDMI 2.0 port again.
 
Last edited:

elaeroplano

macrumors newbie
Jan 29, 2020
2
0
Have updated from 10.15.2. to 10.15.3 but still not working. Trying to connect to external Acer RT270 monitor but get no signal. Tried USBC to HDMI via Apples own adaptor. Tried USCB C to VGA (suggested in one of the forums. Have reset SMC. Cannot Detect Display. The screen recording option only shows zoom

Wits end!!!!
 

wilyone

macrumors newbie
Jan 14, 2016
6
1
Picked up a new mac mini and ran into a similar problem. The HDMI port would not work for the initial setup screen when connected to a 4k TV. Went out and bought a USB-C to HDMI. Moved the cable and could set up the new mini. Went to boot it this morning. TV said no signal. I had to move the HDMI cable from the USB-C to the HDMI port to log in. Once logged in, blank screen. Had to move the HDMI cable back to the USB-C. What in the world is going on that has me doing this port dance to reboot?
 

Dave_O

macrumors member
Nov 16, 2018
67
25
Picked up a new mac mini and ran into a similar problem. The HDMI port would not work for the initial setup screen when connected to a 4k TV. Went out and bought a USB-C to HDMI. Moved the cable and could set up the new mini. Went to boot it this morning. TV said no signal. I had to move the HDMI cable from the USB-C to the HDMI port to log in. Once logged in, blank screen. Had to move the HDMI cable back to the USB-C. What in the world is going on that has me doing this port dance to reboot?
This is a well known problem with Catalina. It might have been fixed with the latest update (10.15.3). The normal HDMI output now seems to work with my 4K TV. If, after updating MacOS, you still have the issue, I'd recommend opening an Apple Support case.
 
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djc6

macrumors 6502a
Aug 11, 2007
591
135
Cleveland, OH
iFixIt teardown shows the mac mini has a MegaChips MCDP2920A4 DisplayPort 1.4 to HDMI 2.0 converter to make the HDMI port function:


I bet this is the firmware that is being updated. Anyone try contacting MegaChips? They are in San Jose:


Apple TV 4K uses same chip - curious if the displays that don't work on 2018 mac mini also fail on Apple TV 4K.
 

Dave_O

macrumors member
Nov 16, 2018
67
25
10.15.3 has not totally fixed the issue. It still happens about once a week, as it did in 10.15.2. The HDMI firmware was not updated from 10.15.2 (remaining at 2.16).
 

TDiz

macrumors newbie
Aug 23, 2019
1
0
I updated my formally perfect working MacBook Pro, running Catalina Public Beta 10.15.4 two days ago.
My LG 27" 4K display now looks dreadful. Bad dayglow coloration and dismal contrast. All my other monitors look perfect.
What is the fix? A C to HDMI connector?...
 

djc6

macrumors 6502a
Aug 11, 2007
591
135
Cleveland, OH
I updated my formally perfect working MacBook Pro, running Catalina Public Beta 10.15.4 two days ago.
My LG 27" 4K display now looks dreadful. Bad dayglow coloration and dismal contrast. All my other monitors look perfect.
What is the fix? A C to HDMI connector?...
Have you tried SMC reset on macbook?

you can also reset settings on LG monitor by unplugging power and holding down power button for 30 seconds. I had this recommended to me when I called LG with some issues and it cleared it right up.
 

Entrep

macrumors newbie
Jul 24, 2010
1
0
10.15.3 has not totally fixed the issue. It still happens about once a week, as it did in 10.15.2. The HDMI firmware was not updated from 10.15.2 (remaining at 2.16).
I agree. Whatever system updates have been released have fixed the issue somewhat, but it still happens about 1-2 a week. Before it used to be every day.
 

Ign1stra

macrumors newbie
Dec 6, 2019
10
6
Germany
I updated my formally perfect working MacBook Pro, running Catalina Public Beta 10.15.4 two days ago.
My LG 27" 4K display now looks dreadful. Bad dayglow coloration and dismal contrast. All my other monitors look perfect.
What is the fix? A C to HDMI connector?...
I have the exact same issue with my LG 27" Monitor connected to a macMini 2018 since upgrading to the latest public beta.
I mentioned that this is caused by the HDR settings. When I turn in the display settings in Catalina the HDR on and off the colors of the monitor sometimes get normal. But after a reboot the bad colors are back.
 

MacsRSour

macrumors newbie
Jan 25, 2019
15
1
I hope they fix this issue soon, it's been annoying me for months. Really disappointed in Apple lately.
I simply try not to reboot to avoid wasting ~10 minutes adusting egpu/hdmi cables until start/login work.

11:40 up 67 days, 14:24
 

tommiy

macrumors regular
Dec 11, 2015
110
18
Yep...in months its been since about October last year for myself. A number of discussions with Apple, logs, kernel debug etc still waiting....guess it will be a year or so before anything changes would be my guess..