Max concurrent videos on screen

My apologies if this is documented somewhere and i didn’t see it. Is there any limit to the number of concurrent videos we can show simultaneously when using a custom UI? Right now it seems to work up to 34. If we have more than 34 on screen at once they seem to just be black vs showing the user’s video. This very well could be something in our code and i’m continuing to dig into it, but wanted to see if there was some known limit that we are hitting.

Thanks!

-stephen

Hi @stallent, thanks for the post.

The only limitation I am aware of is that the default meeting UI can only display up to 49 participants per page. In theory, if there were a limit on concurrent streams to one device, it should be no less than 49. The cap at 34 does not align with any restrictions I am aware of.

I’ll see if I can dig up additional information on this, but you definitely were not overlooking any documentation on this topic. :slightly_smiling_face:

Thanks!

@jon.lieblich thanks. its certainly odd. I’m certainly open to it being our code but I can’t find any errors being thrown or any other potential causes. Its very easy to drive. Lets say i have my window big enough to show 36 users (remote ones, not myself). The first 34 in and turn on video all show. The 35th and anyone above show just black screen but i get no errors. Then if a few people leave, if the ones that were black toggle their video off and back on, it then shows (as long as they become one of the 34 count). Would y’alls logs maybe show some error on that 35th user that isn’t being reported out to our code?

Hey @stallent,

Jon is out currently, so I will be taking over this thread until he returns.

Yes, I believe logs would help investigate this issue further. Would you be able to obtain the SDK logs after an instance of this issue, then send it in an email to developersupport@zoom.us so that we can investigate further?
Please provide a link to this post and/or mention my name in addition to providing your SDK version.

Thanks!
Michael

@Michael_Condon thank you! i"m actually trying to carve out the time to reproduce the issue in your sample app which should make it easier for you to track down. I hope to have that accomplished in the next day or so. While initially we thought it was our code (and still could be) its starting to feel more and more like an SDK issue which is why i wanna help get you clear proof.

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Hey @stallent,

That would be awesome if you could repro in the sample application. That makes things easier for us, and will speed up resolution time.

Thanks!
Michael

@Michael_Condon so while i haven’t reproduced in your sample app yet, i just was informed by my Windows dev coworkers that they are seeing the exact same 34 concurrent video on limit on their side too. This all but verifies its nothing we are doing in our mac code that would cause this. That should be enough evidence for you guys to test it in your own test harness and inform us if 34 is going to become a documented limit or if there is an sdk bug. Thanks!

Hi @stallent,

Thank you for verifying that this behavior is present on Windows as well.

Looking into this further, it may be as simple as enabling a setting on your meeting. As the host of the meeting, you can try calling onDisplayUpTo49InWallView to allow 49 videos to be displayed simultaneously.

Please give this a try at your convenience and let me know if you encounter any issues.

Thanks!

@jon.lieblich Sadly that does not impact it. It is set to true but still max’d out at 34 on both platforms. I wonder if this is a bug with that setting when using a CustomUI vs the standard.

Hi @stallent, thanks for confirming.

We will need to investigate the reasoning for this limitation and get back to you. I think it is possible that we will be able to identify a strategy of increasing this to 49, but I cannot guarantee that in any way at this moment.

Would being able to display 49 users simultaneously be sufficient for your use case? Any additional context on your requirements would be helpful as we look into prioritizing adding support for this.

Thanks!

Hi @jon.lieblich , can Zoom confirm a limit of 34 videos on screen in CustomUI?
I have not reached a stage of testing yet to test that limitation myself but for my use case as many videos on screen as possible is helpful (ideally up to the max 100 panelists).
Thanks for your help.

@jon.lieblich so there are two aspects to this. Yes, being able to show as many simultaneously as the stand alone zoom client would be wonderful, and as close as you can get is great.

But the bigger issue is the limit is undocumented. More than undocumented, i’m not getting any errors or have no way to know in the code that it failed to load. Only that the user sees a blank video. The sdk needs to either 1) explicitly state the limit in documentation or 2) vend it via the video container. For example i’ve noticed that some hardware seems to disable the 49 option in settings so SOMETHING has some input on if 49 is supported or not. Regardless, i should not be able to add 35 (one above what is working) and not get some sort of error or way to know it failed. Maybe a new error code that states we’ve exceeded the max limit or something. Right now it fails completely silently. Thats the biggest issue i have more so than the actual limit.

Hi @stallent and @brainbomb,

Investigating this further, this is not a statically defined limit of 34 simultaneous videos. It is actually a limit on the bandwidth of the connection the SDK is allowed to maintain with our back end.

But the bigger issue is the limit is undocumented

We will work on documenting this limitation as we work towards improving our macOS docs in the future. Apologies for the inconvenience.

More than undocumented, i’m not getting any errors or have no way to know in the code that it failed to load

You are absolutely right that this is problematic. We will investigate if there are any workarounds available through the SDK that can be implemented while we look into adding this functionality in a future release.

Thanks!

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@jon.lieblich thank you very much for the response. Super helpful to get actual details on the issue even if they aren’t fixed yet.

Further questions here are purely for my curiosity… Bandwidth limit. Totally makes sense its backend driven, but the fact its always 34, regardless of video quality or platform or client connection speed seems like its maybe something other than an actual bandwidth limit? I mean how shockingly coincidental would it be if its ALWAYS 34 that triggered some specific bandwidth threshold.

Regardless. Thanks a ton for the response!

-stephen

Hi @stallent,

Always happy to help!

Bandwidth limit. Totally makes sense its backend driven, but the fact its always 34, regardless of video quality or platform or client connection speed seems like its maybe something other than an actual bandwidth limit?

This actually makes more sense than you’d think. If you were streaming something with significant bandwidth requirements like 4k video for each participant, bandwidth would be a serious concern. However, when you are not even reaching HD resolution for everyone in the meeting, the bandwidth required is actually surprisingly small. If you look at our system requirements, you will notice that the bandwidth requirements are very low for non-HD streams.

Hopefully this gives you a bit more insight into why this limit behaves so consistently across varying connections. :slightly_smiling_face:

Thanks!