I just got a Google+ invite.
When I join a Google+ Hangout, I'd like to do it with a green screen so that I can loop a video in the background.
How should I do this?
Do I need a special webcam?
I'm not a video expert, but this is my understanding of the process of green screening. AFAIK, it's not all that easy to do, and it's not something you can do just buy getting a different webcam.
First, you build a set which has a screen in the background of a single color. The color must be uniform, and the chosen color must also be a color which will not appear on the characters and items present in the foreground. Bright green was a very common color to use historically, but modern movies tend to use bright blue.
Next, you record your film as normal in front of the screen. This will be the foreground layer.
Third, you obtain whatever image or whatever you want to be the new background. This will be the background layer.
Finally, you use software to digitally combine the two films. This can be done in post-production (such as in the Star Wars prequels or Avatar) or for live TV (such as most weather reports). You tell the software to treat the green (blue) color on the foreground film as invisible, and thus the background comes through. To do it real-time is much more expensive, of course, because you need to have a computer capable of keeping up.
I expect Final Cut Pro (Mac only, IIRC) and Adobe's Premiere Pro (or something in Creative Suite Production Premium) can do this as those are industry standard for basic professional video editing, but I don't know of any software which I know for a fact can do it real-time.
I'm sure it's possible to change the background on a video without the use of a screen aid, but that would be a lot more difficult I think. Maybe the software could take a picture of the scene prior to filming and mark that as invisible, but I'm just speculating at this point.