Question / Help Unable to use 2x Logitech C930e USB cameras simultaneously, if either use custom resolution

bradjshannon

bradjshannon

New Member
tl;dr:
OBS Studio ONLY works with both if BOTH are set to Default Resolution.
OBS Studio is only able to work with one of these webcams, if either of them is set to Custom Resolution.

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~


Hi folks, I'm a video professional experiencing a problem that is new to me. There doesn't appear to be a solution so I'm going to work around it. I'm posting this for anyone in the future researching this issue.

  • I'm using OBS Studio 25.0.8 x64, on Win10 Pro.
  • Both of my Logitech C930e webcams have the latest firmware from the vendor, as of an hour ago.
  • Both webcams connect to a powered USB 3.0+ hub, which has been extremely reliable (I have used many, and this one is the best model so far; I have several in production environments)
  • I have an additional "real" camera piping to a Magewell HDMI-USB capture device, also connected to the hub.

I verify the cameras work individually:
I can open the "Logitech Camera Settings" app and flip from Webam1 to Webcam2. They each wake up when selected, with indicator LED on and a clear image onscreen.​

Then I close Logitech Camera Settings and open OBS Studio.

I have Webcam1 in Scene1. Webcam2 in Scene2.

I set both cameras to use Custom Resolution, 1920x1080, because that's the only way to get them widescreen. Choosing 'widescreen' in Logitech Camera Settings has the same effect but only sets it temporarily. OBS Studio reverts to a 4:3 resolution, if not specified.

[edit: I tested 1280x720 with the same results]

I switch so Scene1 is live. I open the Video Capture source. I see the same settings, basically, as the Logitech Camera Settings app provided me. I activate the device and see its video feed pop up, as expected. All good so far.

I switch to Scene2. I open its Video Capture source. Same settings as the first camera. I press 'activate' and the indicator LED flickers on/off on/off on/off like it's trying to power up but can't. This happens while the first camera still is active, with indicator LED on.

What if I turn the first one off? Well, I deactivate Webcam1 and get Webcam2 active, with indicator LED lit. And now Webcam1 fails to activate and its LED flickers. So, OBS Studio is only able to work with one of these webcams at a time, for some reason -- electrical, software bug, whatever. But the problem isn't one camera or the other, or a bad cable -- the symptom appears with each camera if the other one is active.

Now, I change one webcam to Default Resolution. It works, as expected. When I change the second to Custom Resolution, it fails as before. If I set the second webcam to Default Resolution, both work simultaneously.

OBS Studio ONLY works with both if BOTH are set to Default.
OBS Studio is only able to work with one of these webcams, if either of them is set to Custom.

Maybe this is my USB hub not providing enough power? I can test that. I'll disconnect my Magewell USB capture device, which draws over 1A of power from the hub. Even with an extra amp of current available, if needed, the cameras exhibit the same symptom. No, it does not appear to be a USB hub power-draw issue.

Maybe this is a USB hub bandwidth issue? No, same test as above. Even without the Magewell device sucking up a ton of USB bandwidth, the symptom remains.

Here it gets weirder: With one webcam up and running in OBS in Default Resolution, I open the Logitech Camera Settings app. Of course it can't display one of the cameras, because OBS is using it. But it can show me the second webcam. AND I CAN SET IT TO WIDESCREEN. The framerate kind of sucks, but it's around 20FPS.

THIS WORKS:
OBS Studio with 1 webcam in Default Resolution​
LCS app with 1 webcam in Widescreen​
​
THE REVERSE DOES NOT:
OBS Studio with 1 webcam in Widescreen​
LCS app with 1 webcam in Default​
​
​
​
So my final conclusion is this, as stated above:
OBS Studio ONLY works with both if BOTH are set to Default.​
OBS Studio is only able to work with one of these webcams, if either of them is set to Custom.​
 
Fenrir

Fenrir

Forum Admin
Sounds like you're overloading your USB ports, and the driver is automatically selecting a lower resolution when the second camera is detected on default settings. Overriding those settings causes it to fail because there's not enough available system resources.

This is just a guess, though, I would need a log from OBS where they fail to see what is actually going on.
 
Harold

Harold

Active Member
The magewell runs on the usb 3.0 bus
The webcams run on a usb 2.0 bus
The split between these two busses happens BEFORE the usb hub.
Don't use usb hubs with webcams.
 
carlmmii

carlmmii

Active Member
To re-emphasize Harold's point, USB2.0 devices are physically only connected to the USB2.0 host controller. Your magewell device is connected to its own separate USB3.0 pins to the USB3.0 host controller, so it has no bearing on any issues with your USB2.0 devices.

There is a hard limit of 480mbps for the USB2.0 spec, and USB2.0 webcams usually use over half of this (or at least, over half of the real-world bandwidth availability). The default resolution working for both is expected due to the lower bandwidth required to send the smaller image feed, but this cannot be sustained normally when using two webcams at any higher resolution when connected to the same USB host controller.

The only real solution is to connect each webcam to a separate host controller. You can get a picture of how your USB connections are grouped using a program called USBview. Use this to identify which ports are connected to which host controllers, and connect your webcams to separate ones.
 
F

featheredphoenix

New Member
bradjshannon said:
tl;dr:
OBS Studio ONLY works with both if BOTH are set to Default Resolution.
OBS Studio is only able to work with one of these webcams, if either of them is set to Custom Resolution.

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~


Hi folks, I'm a video professional experiencing a problem that is new to me. There doesn't appear to be a solution so I'm going to work around it. I'm posting this for anyone in the future researching this issue.
Click to expand...
Ok, having the same problem here, but none of your solutions work for me. I had exactly the same set up on my iMac and everything worked perfectly. I have just gotten a pc specifically for streaming and am experiencing these exact problems. Tried the 'set to default' option, camera flashes but does nothing else. unplugged everything from the hub tried again, same result. I have a Logi 920 and 930e set of cameras. Either work, but not both together. I got the pc because my poor imac is now almost 8 yrs old and really battles to process a twitch stream. This pc was orginially a gaming pc and has a stupid amount of ram and graphics cards so it's not a resource issue either. Any help or advice would be greatly appreciated. Also, the exact same problem happens in Streamlabs obs, so i'm totally stumped. . .
 
carlmmii

carlmmii

Active Member
featheredphoenix said:
Ok, having the same problem here, but none of your solutions work for me. I had exactly the same set up on my iMac and everything worked perfectly. I have just gotten a pc specifically for streaming and am experiencing these exact problems. Tried the 'set to default' option, camera flashes but does nothing else. unplugged everything from the hub tried again, same result. I have a Logi 920 and 930e set of cameras. Either work, but not both together. I got the pc because my poor imac is now almost 8 yrs old and really battles to process a twitch stream. This pc was orginially a gaming pc and has a stupid amount of ram and graphics cards so it's not a resource issue either. Any help or advice would be greatly appreciated. Also, the exact same problem happens in Streamlabs obs, so i'm totally stumped. . .
Click to expand...
Read my above response relating to USB bandwidth. That's the issue you're running into if both work individually -- when you're attempting to use both, they're being connected to the same host controller, and the 2nd one requires more bandwidth than is available.
 
F

featheredphoenix

New Member
Thank you kindly sir! I've been using mac since win95 so have absolutely no idea what I'm doing here. I assumed I could just transfer the hub over to the pc and all would be well. . . It's all fixed now and running. Thanks so much for your patience with the noob. :)
 
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