Studio Display does not work with Catalina 10.15.7

I've been having the same problem, and I've janky found a fix for the issue! This lets me use my Studio Display at full resolution on Catalina without any app freezing.

As @eyablunosky pointed out, it's the "VDCAssistant" process that's causing the problems. From reading its manpage, it seems this process is just related to managed video cameras for Apple services. Since I wasn't expecting the Studio Display's camera to work on Catalina anyway, I don't really care about it. Let's disable it!

So to fix the issue, just temporarily disable VDCAssistant by running this command in a Terminal:

$ sudo launchctl stop com.apple.cmio.VDCAssistant

This temporarily stops the VDCAssistant process for that session. It'll start up again if you re-plug in your monitor or open any app that wants to use it, like Photo Booth or Face Time. When it starts up you'll need to run that command again to disable it.

I re-wrote this info with more details and put it online here: https://gist.github.com/varenc/15ffb3e60bb79408c830f9030b7d74ab#file-studio_display_catalina_fix-md

On that gist is also a shell snippet to just stop the process every 10 seconds... which is very hacky but seems to work. Thank you eyablunosky for figuring out that VDCAssistant was to blame!

I still intended to upgrade to Monterey, eventually, but in the mean time this is at least making my Studio Display usable on Catalina. Cheers!

It’s incompatible with Catalina - return it ASAP.

I've fixed the issue with the apps becoming unresponsive!

It only requires the worlds hackiest workaround and trip to dongle town. I used a USB C to HDMI dongle, and then an HDMI (M) in to display port (F) out dongle. And now I can join zoom calls and use teams without the apps becoming unresponsive and having to unplug my monitor.

One drawback is the display looks noticeably worse this way than with using the thunderbolt connection, and the brightness cannot be adjusted. I'm not sure if my USB C to HDMI dongle supports UHD out, so your mileage may vary. I'm going to try a new dongle and report back later if I get better results. However there is only one HDMI in to display port out dongle I know of, and it's limited to 4k60, which is also bottleneck.

I also noticed something weird when I tried using a high speed USB C cable instead of a thunderbolt cable. The laptop was able to recognize the studio display speakers and webcam unlike before. I thought tricking the monitor into using display port mode with a USB C cable might fix the issue. However, anything that would try to use the speakers or webcam would instantly freeze up, worse than before.

varenchris wrote:

I've been having the same problem, and I've janky found a fix for the issue! This lets me use my Studio Display at full resolution on Catalina without any app freezing.

How do you know it's running at full resolution? Did you check the pixel clock of the timing info using SwitchResX or AGDCDiagnose to make sure it's > 900 MHz? Because nowhere else in macOS does it show the actual output resolution.

What Mac/GPU do you have? I suppose if it supports DSC then you may have 5K. AGDCDiagnose will have that info (DisplayPort link rate, lanes, DSC enabled) for an Intel Mac.

For a Mac with a GPU that doesn't support DSC, 5K may not be possible without Monterey unless maybe you try a custom timing with lower refresh rate. Another option may be to copy the override files from Monterey. You'll also need the .mtdd file. This has not been tested though. The .mtdd file is not loaded from the /Library overrides folder so you'll need to put it in the /System overrides folder. Another option my be the /var/db/displaypolicyd/ folder using a different name for the mtdd file as described at #36

See the following from Studio Display - Technical Specifications - Apple

Studio Display is compatible with the following Mac models running macOS Monterey 12.3 or later:

• Mac Studio (2022)
• 16-inch MacBook Pro (2019 or later)

...

To upgrade to Monterey, see: How to upgrade to macOS Monterey - Apple Support

I have this problem too. It is very frustrating. I don't understand how a monitor can cause Chrome, Zoom, and even Teams for me to be so buggy. It seems to be an issue with VDCAssistant. Apple needs to address this. I also have the problem of when I connect the monitor the brightness is all the way on low.

My work requires me to use Catalina so updating to Monterrey is not an option for me either. I'm really disappointed I have to return the monitor.

error	18:20:01.095160-0400	VDCAssistant	CMIO_DPA_VDC_Server_Assistant.cpp:1381:GetDeviceByGUID No match for specified GUID 0x1414000005ac1114
error	18:20:01.095748-0400	VDCAssistant	DeviceArrived  caught an exception from determining the deviceType (0x1) or removing the device
error	18:20:01.101449-0400	VDCAssistant	[guid:0x1414000005ac1114] Wave2SendVendorSpecificRequest for kWave2ISPAttributesReportID returned 0xe000404f
error	18:20:01.101943-0400	VDCAssistant	[guid:0x1414000005ac1114] DoesWaveCameraSupportVendorSpecificControls not supported. Error 0xe000404f
error	18:20:01.129337-0400	VDCAssistant	CMIO_DPA_VDC_Server_Device.cpp:518 cmio assert: "mContainerID == __null" at exit - (err=0)
error	18:20:01.129726-0400	VDCAssistant	[guid:0x1414000005ac1114] Wave2  Wave2SendVendorSpecificRequest #2 returned 0xe000404f
error	18:20:01.130225-0400	VDCAssistant	[guid:0x1414000005ac1114] Wave2::  Wave2SendVendorSpecificRequest(kWave2GammaOverrideReportID - toneCurve) returned 0xe000404f
error	18:20:01.130695-0400	VDCAssistant	CMIO_DPA_VDC_Server_iSightWave2_Device.cpp:1198:DiscoverCapabilities Wave2::DiscoverCapabilities   we did not find any settings
error	18:20:01.130867-0400	VDCAssistant	[guid:0x1414000005ac1114] SuspendDevice  returned 0xe00002eb
error	18:20:01.231297-0400	VDCAssistant	CMIO_DPA_VDC_Server_iSightWave2_Device.cpp:1198:DiscoverCapabilities Wave2::DiscoverCapabilities   we did not find any settings
error	18:20:01.231455-0400	VDCAssistant	[guid:0x1414000005ac1114] SuspendDevice  returned 0xe00002eb
error	18:20:01.301745-0400	nehelper	-[NWPrivilegedHelper startXPCListener]_block_invoke client pid 141 does not have any known entitlement
error	18:20:01.301997-0400	configd	networkd_privileged_check_interface_settings_block_invoke received XPC_ERROR_CONNECTION_INVALID
error	18:20:01.332053-0400	VDCAssistant	CMIO_DPA_VDC_Server_iSightWave2_Device.cpp:1198:DiscoverCapabilities Wave2::DiscoverCapabilities   we did not find any settings
error	18:20:01.404300-0400	UserEventAgent	ncm-0> No listener for "<private>"
error	18:20:01.404350-0400	UserEventAgent	ncm-0> No listener for "<private>"
error	18:20:01.404454-0400	UserEventAgent	ncm-0> No listener for "<private>"
error	18:20:01.404519-0400	UserEventAgent	ncm-0> No listener for "<private>"
error	18:20:01.404577-0400	UserEventAgent	ncm-0> No listener for "<private>"

the 'MIO_DPA_VDC_Server_iSightWave2_Device.cpp:1198:DiscoverCapabilities Wave2::DiscoverCapabilities   we did not find any settings' error gets logged more and more as the console goes on.

Return, you can always buy one later.

@joevt my "trick" to figure out the full resolution macOS is aware of is to go to Display preferences, then option+click the "scaled" button, which converts the options to showing a long list resolutions. And the highest resolution on that list is always, in my experience, the monitor's resolution as seen by macOS. (meaning it should be the monitor's physical resolution). Since it was showing 5120x2880 as the top option, I assumed I was getting the full resolution. But keep in my I only have used 2 monitors as data points...

I also had some idea that I was getting the full resolution because when I connected the monitor through my eGPU on Catalina I was NOT and the blur was noticeable even when I was running at a logical 2560x1440 resolution (which when doubled for retina should match the physical resolution). And using the trick above, I saw that only 3840x2160 was listed as the top option.

Sadly I've now upgraded to Monterey, so can't double check anymore. But after upgrading I'm even more confident that I was getting the full resolution on Catalina (with a straight monitor->macbook connection) because nothing has changed. I did have to upgrade so that I could get the full resolution when using my eGPU (which is quite necessary with this many pixels).

Also I was one of the people on another macrumors thread you replied to! I wanted to try the mtdd hack, but would have required disabling SIP and I was long overdue for an upgrade anyway. Your knowledge of this topic is so impressive. Thanks for your replies! You've definitely taught me something, and once/if I fully understand everything I'll have learned even more.

Edit: After getting a new high speed USB C to hdmi adaptor, my previous solution no longer works. I don't seem to be able to edit it with the update. The screen constantly flickers. Probably the bandwidth bottleneck coming into play. My previous hdmi adaptor was limiting the resolution to 2560x1440 which is why it looked so bad.

Thank you all so much for trying to find workaround for this. Glad to hear I am not alone either with this issue! I do music production and use tons of different software. If I upgraded to Monterey I have to pay to upgrade some of the software that is working fine and there's the uncertainty of not knowing what will not work with Monterey.

So now I am faced with a big decision --> I don't know how much of a pain is to try to go to BigSur first and then Monterey OR return this monitor. I got a week or two left to return it so I have to make this decision soon. The command line you provided is working so at least I can open Firefox and Chrome now!

By the way, Safari works ok so far with the workaround but it a bit laggy on sites like Fiverr.com which I have to access frequently. Also, nightshift seems to go back and forth, I had to disable it.

@varenchris nice work! It might be worth refactoring that into a cron job rather than a loop + sleep command