Screen Sharing - Mac to Windows

[KUCTech]

Hello Everyone: I will be implementing OBS on a Windows 11 computer to live stream church services. As part of the live stream, I need to include slides from a slideshow which is being shown from an iMac computer. I have been looking at software screen sharing options, and while I am open to suggestions, I am also considering a hardware approach.

The iMac is connected to a projector with an HDMI cable, and the projector is recognized as a second/auxiliary monitor to display the slideshow. My thought is to use an HDMI splitter on the HDMI cable to connect the signal to an HDMI Capture Card, and run that into the Windows/OBS computer via the USB connection. Does this sound feasible?

Some other comments/considerations:

• The computers will be side by side, so distance should not be an issue.
• I have had experience with NDI screen sharing in the past and found it to be unsatisfactory - high resource usage, performance not always reliable.
• My ideal solution should have minimum or no start up requirements at run time. For example, no sign-in or program initialization, etc.
• There needs to be no lag/latency i.e. when the slide changes, it should be reflected immediately in the OBS feed.
• The popular screen sharing software (TeamViewer and equivalents) seem like overkill for a view only requirement.

I hope that makes sense - any comments appreciated.

Regards. . .

Tony N.

 

[AaronD]

My thought is to use an HDMI splitter on the HDMI cable to connect the signal to an HDMI Capture Card, and run that into the Windows/OBS computer via the USB connection. Does this sound feasible?

Absolutely yes! That's the most guaranteed to work of anything. HDMI is its own independent standard, so no question of compatibility...unless your Mac insists on encrypting everything all the time, and your capture card doesn't like encryption. But that's relatively easy to solve.

No change at all to the sending machine, which is always a plus, and using dedicated cabling for each signal eliminates congestion and associated delays or breakups.

 

[KUCTech]

Hi AaronD: Thanks for your reply - very encouraging and reassuring. I generally favour software over hardware solutions, in spite of what people tell me about hardware being more reliable. However, in this case it seems pretty straightforward, so I'm ready to give it a try.

Regards. . .

Tony N.

 

[KUCTech]

Hello Everyone: Well, I have connected my OBS computer to the slideshow computer, splitting off the HDMI feed that goes to the projector, and running a line to the OBS computer.

Although the connectivity seems to be sound, I have some questions about using the video/HDMI feed as an OBS Source. It looks like it's 'single use' - if I try to specify it more than once, I do not get an image, just a blank screen. And if I use the original image multiple times, some of the characteristics carry across all iterations. What I need is several instances, with different positioning and sizes and filters. I have used Source Groups for the filters, but I am wondering if there are other techniques to handle this requirement.

Also, I notice that my shiny new computer has an HDMI In port. Can I do anything useful with this?

Cheers
Tony N

 

[AaronD]

It looks like it's 'single use' - if I try to specify it more than once, I do not get an image, just a blank screen.

Historically, that behavior was universal for performance reasons. Each time it appears, it takes another set of processing power to handle, and the hardware just wasn't that good yet. Now that the hardware usually *is* that good, some operating systems have lifted that restriction, but not all yet.

Regardless, the capture device itself only has a single feed to a single point inside the OS. If the OS allows sharing, it's the OS that copies it, not the capture device.

And if I use the original image multiple times, some of the characteristics carry across all iterations. What I need is several instances, with different positioning and sizes and filters.

I haven't needed to do a whole lot with that yet, but I do know that OBS has a way to do it. Probably several, all of which involve the copy step being at different places along the processing chain, or perhaps a different "loop" of processing, and the signal goes around the same basic structure several times.

The first one that comes to mind is the ability to use an entire scene, as a source in another scene. But I'm sure there are others too.

Also, I notice that my shiny new computer has an HDMI In port. Can I do anything useful with this?

Really?! A built-in capture card? Sure, it's possible, but very few people need one outside of our use-case, and that's a pretty small part of the market for computers in general. So I'd be surprised if it was.

Can you post a picture? See if you can make the lettering clear, which might be difficult if it's just surface-stamped into the sheet metal, and show what's around that connector too.

 

[qhobbes]

Create a scene that is just the HDMI capture card and then add that scene as a source.

 

[KUCTech]

AaronD and ghobbes: Thank you both for your comments. The Scene as Source approach sounds good - I'll give it a try.

AaronD: Here are the specifications for the Lenovo - IdeaCentre AIO 5i Intel (24″).

Cheers. . .

 

[AaronD]

AaronD: Here are the specifications for the Lenovo - IdeaCentre AIO 5i Intel (24″).

Huh. Yeah, it does list both an HDMI Out and HDMI In. I need to see both to confirm the In, since people often get the directions backwards (the plug goes "in" the jack, perhaps, instead of signal directions?), but there they both are.

The quality of that could be anything, from a token cheap deceptive thing that they just wrapped the case around and made into an unverified selling point, to a serious name brand that works perfectly. I'd say it's at least worth a shot.

 

[KUCTech]

Hello Everyone: Following up on trying to make separate iterations of the same source (Video/HDMI capture) unique, I tried creating a base scene with only the HDMI Capture card specified as a Source, and then using that scene as a Source in other Scenes. It works up to a point, in that it keeps the position and sizing straight, but a Filter (e.g. Color Key) applied on one will be applied to all instances. So I'm back to using Groups to keep Filters only on a specified source. Unless there's another way of doing it?

Cheers,
Tony N.