Looking for videoCapture functions code

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Hello, I'm very new to OpenCV and I'm trying to find how some of these functions were actually implemented.
Take the videoCapture class for example. I can find all of the videoCapture functions easily here:

http://docs.opencv.org/2.4/modules/hi...

But I'm trying to find the actual code for these functions to see how they were implemented. Can anyone point me in the right direction?

Edit: OS is Ubuntu