Scene switching in Windows 10 with camera change has certain effects

[H3n4i]

Hi, I would like to share a problem, I am half way through troubleshooting.

I am using two USB webcams (Logitech C270 (hereafter C270) and Microsoft Studio (hereafter MS)) under OBS on a Lenovo X220 with docking station under Windows 10 x64.

There are several scenes set up:
1) both webcams, one in full resolution (MS), the other (C270) with reduced resolution split in the virtual cam.
2) MS full resolution in full screen
3) C270 full resolution (further video device created with full resolution)
4) one still image pix

If I switch between the scenes via hotkey, this leads to the following behaviour under Windows 10 (comprehensible under all versions 26.0 ... up to the current version):
If I switch between 2 to 3 or 2/3 to 4 or back, everything works as intended. If I switch from 2 or 3 to 1 or vice versa, the previously used camera remains off, I have to switch to 4 and back again to have both cams under 1.

This behaviour does not exist (!) with the same configuration under HighSierra (Hackintosh & dual-boot on the X220).
I also think that I had this configuration under Windows 8.1 x64 on the same X220 before and there was no such effect, I'll check this by restoring a backup...

My guess: Due to the change in the scene, the HW driver is operated and reacts too sluggishly. Especially because I have created the C270 twice in order to operate it once in low resolution (320pix) and once in full resolution (1280pix).

It makes no difference whether "deactivate, when not showing" is checked or not.

Since I do not have this effect with the identical HW under HighSierra without switching the devices, I would exclude other reasons for the moment.

From my point of view, the solution could be to set a delay for the driver switchover during the scene change - similar to scene change (500ms) - but since the scene change does not pause, this does not help.

This would be a feature request if other solutions do not help.

I am happy to provide further details, config details or screen shots if it is helpful.

 

[koala]

Don't add the same webcam twice. Remove the low res version of your C270 and add it again by choosing the "add existing" option. This will get you the high res instance of your webcam of the other scene. Don't crop it with the crop filter (it's global for both webcam instances), instead hold down the ALT key and drag the borders of the source on the preview to crop. This is local to each instance of your source. Then resize the source to a size you'd like to show, this is also not reflected to the other instance of your source.

 

[H3n4i]

Thank you koala! I understand what you mean.

I was surprised that it works great under MacOS.

I use ALT for cropping, which works independently for each scene for the MS-Cam.

I use the C270 without crop, I was just do this to reduce to the number of pixels. The idea for different resolutions for C270 was based on the assumption that with a small camera window of C270 in the VirtualCam, I can reduce the computing load and possibly also the output to the VirtualCam.

Because of the low upload bandwidth, I try to keep the VirtualCam as slim as possible.

I'm still testing how it worked under Windows 8.1 - where may the same USB drivers run, but Windows may unload/load the drivers differently.

 

[koala]

Yes, lower resolution means less computing power required. But since you have a high res source anyway, and additional instances of the same source don't need additional computing power, you gain nothing if you add one high res and one low res source. I assume having 2 different sources even need more computing power, because OBS has to handle 2 distinct sources instead of 2 instances of the same source.
Resizing needs practically no computing power: this is done on the GPU with its very efficient graphics capabilities.

Keep in mind that all sources are global. They are all always active, even if invisible in other scenes.