Screen Sharing with High Resolution and High Frame Rate

[fivins]

Hi.  I spend almost 100% of my time screen sharing with my students on Zoom.

I would like to deliver the highest resolution along with the highest frame rate possible.  Optimize for video isn't great since it remvoes the video of my students and creates black boxes for them.

Does anyone know the limitations on how Zoom implements screen sharing?  If I were to invest in a powerful graphics card, could I send 4K at 25 fps or more (I have plenty of internet bandwidth)?  Or, is there some ceiling imposed by Zoom that would prevent thet no matter how powerful the PC?

Any help much appreciated!

[bstrelko]

Unfortunately, Zoom cares very little about your graphics card and puts a tremendous amount of burden on your CPU (the low hanging fruit - this is because the bulk of consumers don't even have discrete GPUs).

There is a ceiling. 

https://support.zoom.com/hc/en/article?id=zm_kb&sysparm_article=KB0068426

As you can see, even when using the 'optimize for video' function, the resolution is downsampled - I've personally never seen it go higher than 1280x720 on high-end systems, which is horrendous and not worth the higher framerate.

You won't get 4K, but your best bet might be to use a capture card (many manufacturers, I've found Magewell to be reliable) or a virtual camera (OBS, Manycam, VMix) and pipe your shared content through your 'camera' feed. This will give you up to 1920x1080 video at the highest framerate Zoom will allow (still typically around 20-30fps max).

Zoom is stingy about bandwidth and even 1080p was a 'premium feature' that had to be manually requested until a short while ago. There are still a number of hoops to jump through in order to 'convince' Zoom to send FHD video. Always try to ensure that at least one far-end participant is viewing the desired FHD video source in full-screen - otherwise, Zoom will try to scale the sending video down because it's not 'necessary'. Not a hi-res friendly platform!

[fivins]

Thanks @bstrelko 🙂

I wonder if my settings are a bit different than yours.  When I check the stats during the call my "screen share" is reporting the full 4K resolution but at a painfully slow fps (5-8).  My students confirm that the fps is very low on their end.  I actually have to lower my Windows 11 resolution to force it to send at 1K to get the fps up to a tolerable level (about 25 fps).

I wish they screen sharing more seriously.  It's important enough to my work that I would be willing to pay a premium to ensure high res and high frame rate.

[bstrelko]

Huh. To confirm, you have 'optimize for video' ticked when seeing 4K@5fps, correct?

[fivins]

HI @bstrelko 

Sorry, I missed this last response somehow. 

No, I don't use the optimize function because 1.) it removes my student's video feed 2.) It shows all Zoom windows as black boxes over the shared feed which isn't great.

"optimize for video" does seem to downgrade the resolution according screen share stats, but again, not  a great option for me for the reasons above.

So,  with normal screen share, it seems Zoom attempts to send my 4K monitor's full res but at very low fps.  This does seem to have a lot to do with hardware.  I tried the exact same settings on my son's gaming PC (I use a lapto with integrated GPU).  Stats there say it's sending 4K at 20-25 fps. He has an RTX 460 card.

So, I'm wondering if that's the upper limit or if even more powerful CPU/GPU combos can send higher fps?

At the moment, I have to manuall downgrade my res through Windows display settings to 1080p to get a decent fps.

I hope that make sense!

[bstrelko]

Makes perfect sense - thanks for clarifying!

There is a ton of non-customer-facing logic under the hood that would govern hardware acceleration - it's actually refreshing to hear that performance with the RTX4060 is better (Zoom Client utilizes external GPUs, Zoom Rooms - where it's often more needed - does not).

This would ultimately be a question for Zoom's tight-lipped engineering team - here's hoping you get an answer!

[fivins]

I'll prod them a bit and see how far I get!

[brunavs]

I'll leave a comment here because I've had the exact same issue for quite some time now (and also as a teacher) and never found a successful solution. Hopefully the support team finally helps us?

[fivins]

Agreed.  I'm actually happy to invest in the hardware needed to maximize the experience for my students.  However, while Zoom are opaque about how this all works, it's difficult.  I would like to know if there is a ceiling on what is possible from Zoom or if the sky is the limit if I have enough CPU, GPU, and bandwidth?