Is there a way to release the integrated webcam service held by an .exe application?

I have a Dell Inspiron 15 3542 laptop with Windows 8.1. Recently, I installed the Zbar application for scanning QR code. It does decode the QR code using integrated webcam. But the problem is, i am able to use the service only once! If I try to run the application again, it throws an ERROR which is shown on a command prompt window for a second and it disappears. I tried to run the Zbar application as a subprocess from python and I could see the error which stated:

InvalidRequestError: ERROR: zbar processor in _zbar_video_open():
    invalid request: failed to connect to camera '/dev/video0'

I tried disabling and enabling the Driver from Device Manager but with no success. To use the Zbar application I have to reboot my laptop. My question is not about Zbar application's erratic behavior.

My questions are-

What is the name of the Integrated Webcam service?

Is there a way to release the resources held by an application in Windows?

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