How to use an extra webcam on android?

I have got android 3.开发者_如何学Python1,it got usb API.So I'd like to use an extra usb webcam,but I dont know how to do.Can somebody please help me?

Thanks.

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I'm assuming you use this API: http://developer.android.com/guide/topics/usb/host.html

In that case, you need to re-implement your camera driver in Java. Perhaps gspca sources will help.