USB Webcam Limit - 3 Cameras Maximum?

[georgeb23]

Hi there,

So yesterday I tried connecting 4 USB webcams to my laptop (Asus, 8GB RAM, Windows 11 Home, Intel i7) in OBS. Only 3 would work simulataneously, and this depended on which of the webcams was plugged in last. I cannot use the "Deactivate when not showing" feature as the cameras often need to be displayed together on screen.

I looked in USBview to discover that my laptop only has 1 USB controller / Root hub, and I understand this may result in not enough bandwitdth to be available for 4 webcams to run together?

I know USB hubs are not at all recommended when using them with webcams, but I can plug 3 into a USB hub and they all work perfectly. My laptop has 2 regular USB ports (presumably 2.0?) and one USB port labeled "SS" - I have tried all combinations of where to plug in the USB hub, and where the different cameras are plugged in - however the 4th webcam no matter what just shows a black screen in OBS.

All webcams work fine when using the Microsoft Camera app - I assume this is because here the cameras are being activated in turn rather than all together as OBS does.

My question is this - is there any workaround at all so I can reliably use 4 cameras, or am I stuck at 3 because of a bandwidth issue / the fact that my machine only has 1 USB controller?

Thanks chaps

 

[khaver]

You can't force more bandwidth through your USB hardware than it was designed to handle. There is a hard limit. Try lowering the resolution of any cameras you don't use full screen in your scenes.

 

[AaronD]

I looked in USBview to discover that my laptop only has 1 USB controller / Root hub, and I understand this may result in not enough bandwitdth to be available for 4 webcams to run together?

I know USB hubs are not at all recommended when using them with webcams, but I can plug 3 into a USB hub and they all work perfectly. My laptop has 2 regular USB ports (presumably 2.0?) and one USB port labeled "SS" - I have tried all combinations of where to plug in the USB hub, and where the different cameras are plugged in - however the 4th webcam no matter what just shows a black screen in OBS.

"SS" stands for "Super Speed" (marketing :-P). Usually, that's a 3.x port. If you look into it, can you see more than the traditional 4 contacts? That's the difference between 2.x and 3.x. 3.0 introduced a whole 'nother bus, essentially, in the same cable because the later end of v2 had already squeezed as much performance as they could get out of the original single twisted pair + power.

Sure, it's not recommended, but I do run 4x HDMI capture cards on a 4-port USB 3 hub. Holdover from trying to software-reboot that hub from a script because the cards don't like being powered on 24/7, as they are on this motherboard even when the OS is shut down. (no jumper or BIOS setting either) I ended up using an automotive relay instead, to control the ATX 5V standby (the only thing that stays on), based on the ATX 12V rail, so that the whole thing goes dead. Button to bypass the relay, and I set the BIOS to always turn on after a "power failure", which is effectively what the relay creates. So now the cards reboot that way. Never got around to removing the hub, but it seems to work okay for me.

If you only have one controller anyway (very common), then all of the external ports go through an internal hub. So you're still going through a hub regardless. There might be something to say about minimizing the number of hubs, but "not having any" isn't really achievable.

If you do have a for-real USB 3.x port, that really does support that data rate (marketing again, and designed to sell more than work :-P), then you might think about putting a for-real USB 3 hub (fakes exist) on that port and running the cameras through that. Yes, you're intentionally adding a hub, against the recommendation, but if it gets you from "garbage" to "okay", then it's still an improvement.

 

[georgeb23]

You can't force more bandwidth through your USB hardware than it was designed to handle. There is a hard limit. Try lowering the resolution of any cameras you don't use full screen in your scenes.

Thanks, I'll give that a try and let you know how it goes.

 

[georgeb23]

"SS" stands for "Super Speed" (marketing :-P). Usually, that's a 3.x port. If you look into it, can you see more than the traditional 4 contacts? That's the difference between 2.x and 3.x. 3.0 introduced a whole 'nother bus, essentially, in the same cable because the later end of v2 had already squeezed as much performance as they could get out of the original single twisted pair + power.

Sure, it's not recommended, but I do run 4x HDMI capture cards on a 4-port USB 3 hub. Holdover from trying to software-reboot that hub from a script because the cards don't like being powered on 24/7, as they are on this motherboard even when the OS is shut down. (no jumper or BIOS setting either) I ended up using an automotive relay instead, to control the ATX 5V standby (the only thing that stays on), based on the ATX 12V rail, so that the whole thing goes dead. Button to bypass the relay, and I set the BIOS to always turn on after a "power failure", which is effectively what the relay creates. So now the cards reboot that way. Never got around to removing the hub, but it seems to work okay for me.

If you only have one controller anyway (very common), then all of the external ports go through an internal hub. So you're still going through a hub regardless. There might be something to say about minimizing the number of hubs, but "not having any" isn't really achievable.

If you do have a for-real USB 3.x port, that really does support that data rate (marketing again, and designed to sell more than work :-P), then you might think about putting a for-real USB 3 hub (fakes exist) on that port and running the cameras through that. Yes, you're intentionally adding a hub, against the recommendation, but if it gets you from "garbage" to "okay", then it's still an improvement.

I can confirm that there are 5 contacts in the USB port marked "SS" - so am I right in saying this is a 3.x port then?

Just to check, do you still suggest going for a proper 3.0 USB hub to see if this works? To be honest I am in need of another anyway so I can use my already existing one (which I don't think is 3.0) for other duties.

 

[Lawrence_SoCal]

Just to check, do you still suggest going for a proper 3.0 USB hub to see if this works? To be honest I am in need of another anyway so I can use my already existing one (which I don't think is 3.0) for other duties.

It is worth a try. Hopefully you can get a quality USB 3.x hub that you can return for a full refund if it doesn't work for you. My approach, with spare budget, is to go for slight overkill, so maybe a USB 3.2 (Gen2x2 /20gb/s) vs a slower one, if price premium is small. If you think you may have a USB2 hub, that is absolutely a limiting factor (and easily testable by attaching a USB 3.x flash drive to that hub and checking data transfer performance

 

[AaronD]

I can confirm that there are 5 contacts in the USB port marked "SS" - so am I right in saying this is a 3.x port then?

You mean 5 additional contacts? Or 5 total? There should be 5 additional - 2 dedicated for each direction with different physical requirements from the original, and 1 more ground/shield - plus the original 4 for power, ground, and 2 signal. 9 total.

Just to check, do you still suggest going for a proper 3.0 USB hub to see if this works? To be honest I am in need of another anyway so I can use my already existing one (which I don't think is 3.0) for other duties.

Yes. And Lawrence has some good advice too.

One potential hangup is that the latest USB standard has decided to limit itself to the C-type connector. (I remember an interview with one of USB's original designers, who said that it should have been that way from the beginning, but the prototype was cheaper and took off prematurely, hence the "turn it over twice before it goes in" meme) So pay attention to the type of connector that you're getting, as well as the data standard.

 

[georgeb23]

It is worth a try. Hopefully you can get a quality USB 3.x hub that you can return for a full refund if it doesn't work for you. My approach, with spare budget, is to go for slight overkill, so maybe a USB 3.2 (Gen2x2 /20gb/s) vs a slower one, if price premium is small. If you think you may have a USB2 hub, that is absolutely a limiting factor (and easily testable by attaching a USB 3.x flash drive to that hub and checking data transfer performance

I'll find and order one and let you know how it goes. Cheers.

You mean 5 additional contacts? Or 5 total? There should be 5 additional - 2 dedicated for each direction with different physical requirements from the original, and 1 more ground/shield - plus the original 4 for power, ground, and 2 signal. 9 total.

Unless I've gone blind / missed a load of connections on another "side" of the port, there were 5 TOTAL contacts in the SS USB port. Does this change the advice?

 

[AaronD]

Unless I've gone blind / missed a load of connections on another "side" of the port, there were 5 TOTAL contacts in the SS USB port. Does this change the advice?

The host side (I presume that's what you're looking at) has the additional 5 easy to see, and the original 4 are back in a little bit. Google images should help.

Edit: Searching GI for usb 3.0 port, I ended up with this, which has a good picture at the top:

What Is USB 3.0? - The Plug - HelloTech

USB 3.0, also called SuperSpeed USB, is the third generation of Universal Serial Bus standard. It is capable of transmitting data at a maximum rate of 5

www.hellotech.com

 

[georgeb23]

Got it! I could see all 9 contacts originally, just not well enough. I (for whatever reason) assumed the 4 at the back were connected to the 5 at the front! D'oh!

 

[AaronD]

Got it! I could see all 9 contacts originally, just not well enough. I (for whatever reason) assumed the 4 at the back were connected to the 5 at the front! D'oh!
View attachment 90063

Yep! That has the connections for USB 3 at least. So that'd be your best bet to run cameras through. Or any live video, in or out, if you don't have an available dedicated connector for it. If the controller behind it isn't fast enough, then it's probably time for a new (to you) laptop.

 

[georgeb23]

Happily admitting my stupidity here and apologies for messing you all around.........just noticed my laptop has a USB C port marked SS which I haven't noticed until now..........bigger d'oh!

So pay attention to the type of connector that you're getting, as well as the data standard.

So I presume I can go for a USB C hub which should make things even better?

If the controller behind it isn't fast enough, then it's probably time for a new (to you) laptop.

I hope a new hub solves it because the laptop was brand new in August! Therefore out of the option.

 

[georgeb23]

You can't force more bandwidth through your USB hardware than it was designed to handle. There is a hard limit. Try lowering the resolution of any cameras you don't use full screen in your scenes.

Lowered all webcams to lowest they would go and still the 4th didn't work. I use / will use all my webcams, whether it be 3 or 4, on full screen at some point.

Another message from me awaiting moderator approval.

 

[georgeb23]

Looking at my laptop specs, it says both USB C port and the SS USB port are both 3.2, don't know if this helps any further.

 

[AaronD]

.........just noticed my laptop has a USB C port marked SS which I haven't noticed until now..........
So I presume I can go for a USB C hub which should make things even better?

Sure! USB C by definition has all the connections required for 3.x. They're even duplicated so that it works both ways around!

It's still possible that only the legacy pins are connected, but I think that's more likely for devices that want to use that connector but don't actually have a 3.x controller.

As for the data standard, there's no difference between the updated "A" connector and the "C" one. Same connections and same specs on a different plug.

 

[georgeb23]

Thanks for the reply, I'll get one ordered and let you know how it goes.

 

[Lawrence_SoCal]

If you have a USB-C port, due to industry migration to that port/plug style going forward, to simplify matters, I'd get a USB-C hub, presuming no or small price premium compared to equivalent USB-A cabled hub. I'm betting your cameras are USB-A, so you need to make sure your hub has enough of those ports, just recognize that it is likely future peripherals are more likely to be USB-C than A (though a simple cheap A-to-C adapter works fine, but who wants to bother with them)
And I'd be looking for a true 20Gb/s USB 3.2 (Gen 2 x2... stupid USB forum naming convention, /separate rant) hub, as a higher speed hub less likely to have trouble at the slower speeds your camera will use (ie spend a couple extra dollars to over-provision, to reduce chance of a flaky hub being an issue)

 

[georgeb23]

Cheers, thanks for the advice!

 

[georgeb23]

USB Hub
Does this seem like a wise choice? It says it cannot support charging but this isn't an issue, I won't ever be charging anything from it.

 

[AaronD]

USB Hub
Does this seem like a wise choice? It says it cannot support charging but this isn't an issue, I won't ever be charging anything from it.

There's an official part of the USB spec, that didn't exist originally, to support fast-charging. It provides a way for devices to ask for and get up to 20V instead of the normal 5V, and a boatload of current as well.

If that's what it doesn't have, then you're fine. The cameras won't ask.

If it has such a limited power budget that it shuts down with 4 cameras connected, then that's a problem. Also relevant in that discussion is the amount of power that the laptop port can provide, since all of it has to come from there. Not everything supports full power, and not everything is capable of shutting off like the spec says it's supposed to. (which is why some USB desk fans work)