Qt multi purpose capture window

[Shunyata]

Hello,

I want to write a capture window in C++ and Qt, which can display any other window's contents and also video feed from a webcam, a tv stream etc. (I want to be able to overlay several sources later on). Could anybody point out how to do this in general and which classes and techniques I should research? Thanks in advance.


Best regards,
Shunyata

PS:
It would also be interesting to know how to implement pie menus. Does anybody know how to do this most effectively?

[Shunyata]

Now, for a start - Could anybody at least tell me generally how to write a program, which can display my webcam video feed like CamStream does? I would really appreciate the effort. Video4Linux drivers are present and the device is located at /dev/video0 just like it should be. The stream is shown fine by CamStream, but I want to know how to write it in simple form myself. Because the program supports a lot, looking at the source directly would be cumbersome. Just a few hints would be really helpful as a kick-start. Thanks in advance.