Yesterday I installed HeadTracking Demo from faceAPI website on my laptop which has a built-in webcam. However the app only displayed blank image on the camera feed. I thought maybe my laptop just can't run the app, so I simply uninstalled it.
The next day when I want to use the webcam, it still displays no image. The light is on but there is no image. I tried everything, disable-enable/uninstall-reinstall the driver, system restore, download the webcam driver from Asus website (since my laptop is Asus) and installed it manually... still, no image.
I started to panic. I registered for a free version of the faceAPI so I don't think I will get support and I couldn't find their forum either, so I contacted Asus support instead while still trying to fix this problem. Then I found the fix! I run Asus LifeFrame which has access to built-in webcam settings and restore everything to default, and then suddenly my camera works as it supposed to do.
So I guess, perhaps the HeadTracking Demo set my camera brightness to 0, maybe a bug, I don't know, and resetting camera settings would fix it.