How to use green screen with video?

[MitchStevens]

How do I create a video using a green screen that will allow me to put whatever is on my desktop in the background of the video? Does anyone know of any good applications for this?

For example, is it possible to have a PowerPoint in the background as I describe what is being presented via green screen?

[MitchStevens]

I've seen how Camtasia can do picture-in-picture video. But it can't do video like the weatherman - where the speaker can interact with the content in the background. Is there something that can do that in real time without the editing process?

[poisondeathray]

Do you already have 2 videos? 1 with the subject shot on green screen , 1 with the "background"?

The general method is to "key" out the green screen, leaving the subject on a transparent background. This is done with software like after effects or premiere. You then take that keyed footage and superimpose it onto the background video (compositing)

[guns1inger]

Have a look at CineGobs Keyer, which is a free and rather powerful keying tool. It does green/blue screen separation, garbage mattes, roto-keying and keyframing, and for a freebie is very good.

[edDV]

I'm confused by your question.

Are you doing this live or in post?
The first post said you were making a video.

Are you asking for free or do you have a budget?

Is this for high resolution presentation or a web feed?

Do you have any current editing software (e.g. Premiere, Vegas, etc)?

There are answers for no budget up to pro with a low budget "teacher" able to get great discounts.