How can I embed a video in a XNA application? I'm developing a card game with XNA C# and I need to send webcam video between four machines. Could anyone give me some tips about that?
I believe the general solution to this is to capture the webcam images and apply it to a Texture2D. This is known as rendering to a texture. You can find more information here: http://www.riemers.net/eng/Tutorials/XNA/Csharp/Series3/Render_to_texture.php
Be warned that that tutorial is made for XNA 3.1 so it might need a bit of work porting it to XNA 4.0 code.
I've found a few webcam components/image capture facilities that are written in C# so they can be used along with the XNA framework:
https://stackoverflow.com/questions/1789684/webcam-calling-in-xna - This SO question provides a few answers and even some techniques to apply the webcam stream to an image (although it's a very dirty way in my opinion).
http://forums.create.msdn.com/forums/p/1467/9530.aspx#9530 - This forum post provides an XNA specific Webcam component that allows you to capture the images to a texture. I believe this to be fairly buggy, but the code should provide you with a good starting point.
Hope that helps!