No CAM 2 using iMac with ATEM Mini Pro

Volunteer helping with new setup and can't figure out this issue.

iMac (M3 - 2 thunderbolt ports, 2 USB 3 ports)
ProPresenter running on the iMac
ATEM Mini Pro
JVC PTZ camera

We have 3 TV's and the iMac connected to an HMDI splitter (input) and the output from that splitter going to CAM 2 on the ATEM. The JVC camera is connected to CAM 1 via HDMI.

In Multiview, we can see the JVC camera image in CAM 1 but not the iMac in CAM 2 (it's black). If I unplug and replug the cable for the iMac, the image appears for a brief second and goes to black. I purchased a Thunderbolt to HDMI cable and connected my iPhone 15 directly to CAM 2 and the image appears properly and switches between CAM 1 and CAM 2 as expected. If I use the same cable with the iMac (plugging directly from either a Thunderbolt or USB 3 port), the CAM 2 screen is black.

I've tried new HDMI cables, a new powered HDMI splitter, a 3rd party usb 3 adapter, an apple branded thunderbolt to HDMI adapter, switching the JVC to CAM 2 and the iMac to CAM 1 (camera works on CAM 2, nothing via the iMac to CAM 1), a powered splitter between the Mac and the existing HDMI splitter, different CAM inputs on the ATEM. All with the same issue.

Can anyone help please? This is frustrating and I can't get an answer that makes sense other than "connect directly via HDMI because adapters/dongles aren't supported".

Thanks in advance!

HDMI splitters can cause real problems. I’ll try to explain.
HDMI devices come in two basic types - SOURCES and SINKS.
Sources are for example - DVD players , Set Top boxes , ATEM outputs, iMAC outputs , PC outputs - these send video signals.
SINKS are consumers of video - for example displays , recorders , ATEM inputs.

HDMI can support many resolutions - and SINKS contain a set of supported video formats.
SOURCES ask SINKS about the supported resolutions and if they can agree on a common set then all is good.

When you use a splitter the potential for creating a situation with no common supported formats increase.
For example you have a 1 to 3 splitter , and so have 1 SOURCE video and 3 SINKS ( tv/monitor) . ( the splitter has 3 SOURCES and 1 SINK )
Splitters can either be dumb , or somewhat clever about how they deal with this - and thats the problem you don’t know what the splitter will do. Sometimes they try to merge the available formats , sometimes you can tell the splitter to use the video formats (EDID) available from a particular port on the device.

Sadly in the attempt to make life easier for normal situations HDMI has made more complex abnormal situations difficult unless you really understand what is going on.

For these situations - most professionals use devices such as the Decimator scalers/cross converters ( MD-HX ). These are able to convert the video standards.

Sometimes you can use EDID faker devices which replace the list of video modes - and hope that each SINK can actually display the selected video mode.

I know this is a long answer - but it is a messy subject.

https://www.amazon.co.uk/Emulator-Passthrough-Manager-Equipment-Projector/dp/B0CRHSXPDJ this is the cheap device I usually use - which sometimes helps - but really a decimator is usually a good tool to have at hand.

Have you tried setting your iMac video output to other possible modes ? E.g. one of the Atem supported formats ?

Thanks for the reply.

Do you think using an MD-HX converter between the iMac and the ATEM (thunderbolt/HDMI cable from iMac to the converter HDMI input and converter HDMI output to ATEM CAM 2 input) is worth a try?

The thing that confuses me is my iPhone 15 works using a thunderbolt/HDMI cable to the ATEM but the iMac does not, using the same cable.

Use an UltraStudio Mini Monitor 3G to get a proper video signal from the iMac.

It's far cheaper than a cross converter and will work fine.

There are significant issues with Apple M series HDMI out signals.

Thank you for the recommendation. I will purchase and keep my fingers crossed!

The thing that confuses me is my iPhone 15 works using a thunderbolt/HDMI cable to the ATEM but the iMac does not, using the same cable.

I think iPhones ( and iPads ) are intended for connecting to TVs ( and thus negotiate standard TV resolutions ) but iMacs are intended to connect to monitors - which may or may not support standard TV modes. Thus iMacs have a much wider range of supported resolutions - iPhones / iPads a much more limited range.

Use an UltraStudio Mini Monitor 3G to get a proper video signal from the iMac.

It's far cheaper than a cross converter and will work fine.

There are significant issues with Apple M series HDMI out signals.

Certainly that is an option - it depends if you think you may need to convert other signals which might not originate from a PC/Mac. Also - using a decimator does not require any drivers - and some applications may not be able to generate output for a device which requires the decklink API ( its been a while since I’ve used any decklink device on a mac - but in some circumstances you need specific support for generating video from these devices - not sure how the desktop output software works nowadays ).
As a linux user - I certainly prefer a non software dependent solution )

Can be a bummer trying to get an HDMI signal out of a Mac at times. This is typically what they do, black screen, not no-signal but black output. Folks will be quick to assume HDCP but in my case 30p was black (not out of range) and 60p was fine. I’ve used SwitchresX in the past to solve display issues but I honestly couldn’t say where support lies with with the modern ARM processors.

Desktop output isn’t supported with the Ultrastudio, Propresenter will work with the device but may require an additional sofware license (module) depending on the version.

Good Luck

Thank you everyone for the replies/suggestions/information.

As I currently wait for Blackmagic Tech support (I'm on hold) for help with this issue, I can relay that the UltraStudio Monitor 3G did not work. I also confirmed it's not supported with ProPresenter (which we use).

Before I try the Decimator MD-HX, I'm hoping Blackmagic support can offer some suggestions. This is a bummer.

Update:

Great tech support!

After messing around with display settings, we were able to get the iMac to display properly via input 2 on the ATEM Mini Pro. However, that was a direct connection to the ATEM. It appears that the HDMI splitter (the second one we've tried) is the culprit. It's a 1 input/4 output powered splitter. I've tried this generic splitter, as well as a StarTech branded splitter.

So, does anyone have any suggestions for a splitter to try? I'm going to search the forum but thought I'd ask here for now.

Thanks again for the help!

Update:

Got it to work! Thanks to this thread:
viewtopic.php?f=4&t=122818&p=984250&hilit=Manhattan+hdmi#p984250

A user posted "Then I found out that most newer splitters contain the Macrosilicon MS933x IC which is for some reason incompatible with ATEM output. Then I tried another splitter, Manhattan Compact 4K 4-Port splitter and it worked!"

So, I purchased and tried the Manhattan Compact 4K 4-Port splitter and it's working as intended.

Hope this info helps in case anyone else is having issues. HDMI is weird...