Thanks for your reply,
I use below camera and it's installed on the door,
My computer has installed a capture card which used to capture analog signal, the model is "ProHDTV Dual 3"

Capture card manufacture:
http://www.magic-pro.com/en/product/oth ... V_Dual.htm----------------------
If I directly use vitamindvideo to connect with the camera via capture card, The webcam feed will not reverse.
However, when the webcam feed go into webcamxp first, and use vitamindvideo to obtain the webcam feed from webcamxp web server, the screen reverse.
In order to find out whether it's vitamindvideo or webcamxp problem, I installed a 3rd party software, "IP camera viewer"
http://www.deskshare.com/ip-camera-viewer.aspxWhen the "IP camera viewer" obtain the webcam feed from webcamxp, the feed have not reverse.
Although "IP camera viewer" provided a rotate function but I did not need to use it.

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Conclusion: vitamin d video have a bug.
Please let me know what you think,
Regards,
Kam